fix: Context.setConfig must update metaConfig and indexConfig fields

This PR fixes a bug at `Context.setConfig`. It was not propagating
the configuration to the redundant fields (cache) `metaConfig` and `indexConfig`.

.github/workflows/labels-from-comments.yml

@@ -1,8 +1,7 @@
 # This workflow allows any user to add one of the `awaiting-review`, `awaiting-author`, `WIP`,
-# `release-ci`, or a `changelog-XXX` label by commenting on the PR or issue.
+# or `release-ci` labels by commenting on the PR or issue.
 # If any labels from the set {`awaiting-review`, `awaiting-author`, `WIP`} are added, other labels
 # from that set are removed automatically at the same time.
-# Similarly, if any `changelog-XXX` label is added, other `changelog-YYY` labels are removed.
 
 name: Label PR based on Comment
 
@@ -12,7 +11,7 @@ on:
 
 jobs:
   update-label:
-    if: github.event.issue.pull_request != null && (contains(github.event.comment.body, 'awaiting-review') || contains(github.event.comment.body, 'awaiting-author') || contains(github.event.comment.body, 'WIP') || contains(github.event.comment.body, 'release-ci') || contains(github.event.comment.body, 'changelog-'))
+    if: github.event.issue.pull_request != null && (contains(github.event.comment.body, 'awaiting-review') || contains(github.event.comment.body, 'awaiting-author') || contains(github.event.comment.body, 'WIP') || contains(github.event.comment.body, 'release-ci'))
     runs-on: ubuntu-latest
 
     steps:
@@ -21,14 +20,13 @@ jobs:
       with:
         github-token: ${{ secrets.GITHUB_TOKEN }}
         script: |
-          const { owner, repo, number: issue_number } = context.issue;
+          const { owner, repo, number: issue_number  } = context.issue;
           const commentLines = context.payload.comment.body.split('\r\n');
 
           const awaitingReview = commentLines.includes('awaiting-review');
           const awaitingAuthor = commentLines.includes('awaiting-author');
           const wip = commentLines.includes('WIP');
           const releaseCI = commentLines.includes('release-ci');
-          const changelogMatch = commentLines.find(line => line.startsWith('changelog-'));
 
           if (awaitingReview || awaitingAuthor || wip) {
             await github.rest.issues.removeLabel({ owner, repo, issue_number, name: 'awaiting-review' }).catch(() => {});
@@ -49,19 +47,3 @@ jobs:
           if (releaseCI) {
             await github.rest.issues.addLabels({ owner, repo, issue_number, labels: ['release-ci'] });
           }
-
-          if (changelogMatch) {
-            const changelogLabel = changelogMatch.trim();
-            const { data: existingLabels } = await github.rest.issues.listLabelsOnIssue({ owner, repo, issue_number });
-            const changelogLabels = existingLabels.filter(label => label.name.startsWith('changelog-'));
-
-            // Remove all other changelog labels
-            for (const label of changelogLabels) {
-              if (label.name !== changelogLabel) {
-                await github.rest.issues.removeLabel({ owner, repo, issue_number, name: label.name }).catch(() => {});
-              }
-            }
-
-            // Add the new changelog label
-            await github.rest.issues.addLabels({ owner, repo, issue_number, labels: [changelogLabel] });
-          }

doc/examples/interp.lean

@@ -12,17 +12,17 @@ Remark: this example is based on an example found in the Idris manual.
 Vectors
 --------
 
-A `Vec` is a list of size `n` whose elements belong to a type `α`.
+A `Vector` is a list of size `n` whose elements belong to a type `α`.
 -/
 
-inductive Vec (α : Type u) : Nat → Type u
-  | nil : Vec α 0
-  | cons : α → Vec α n → Vec α (n+1)
+inductive Vector (α : Type u) : Nat → Type u
+  | nil : Vector α 0
+  | cons : α → Vector α n → Vector α (n+1)
 
 /-!
-We can overload the `List.cons` notation `::` and use it to create `Vec`s.
+We can overload the `List.cons` notation `::` and use it to create `Vector`s.
 -/
-infix:67 " :: " => Vec.cons
+infix:67 " :: " => Vector.cons
 
 /-!
 Now, we define the types of our simple functional language.
@@ -50,11 +50,11 @@ the builtin instance for `Add Int` as the solution.
 /-!
 Expressions are indexed by the types of the local variables, and the type of the expression itself.
 -/
-inductive HasType : Fin n → Vec Ty n → Ty → Type where
+inductive HasType : Fin n → Vector Ty n → Ty → Type where
   | stop : HasType 0 (ty :: ctx) ty
   | pop  : HasType k ctx ty → HasType k.succ (u :: ctx) ty
 
-inductive Expr : Vec Ty n → Ty → Type where
+inductive Expr : Vector Ty n → Ty → Type where
   | var   : HasType i ctx ty → Expr ctx ty
   | val   : Int → Expr ctx Ty.int
   | lam   : Expr (a :: ctx) ty → Expr ctx (Ty.fn a ty)
@@ -102,8 +102,8 @@ indexed over the types in scope. Since an environment is just another form of li
 to the vector of local variable types, we overload again the notation `::` so that we can use the usual list syntax.
 Given a proof that a variable is defined in the context, we can then produce a value from the environment.
 -/
-inductive Env : Vec Ty n → Type where
-  | nil  : Env Vec.nil
+inductive Env : Vector Ty n → Type where
+  | nil  : Env Vector.nil
   | cons : Ty.interp a → Env ctx → Env (a :: ctx)
 
 infix:67 " :: " => Env.cons

doc/examples/tc.lean

@@ -82,7 +82,9 @@ theorem Expr.typeCheck_correct (h₁ : HasType e ty) (h₂ : e.typeCheck ≠ .un
 /-!
 Now, we prove that if `Expr.typeCheck e` returns `Maybe.unknown`, then forall `ty`, `HasType e ty` does not hold.
 The notation `e.typeCheck` is sugar for `Expr.typeCheck e`. Lean can infer this because we explicitly said that `e` has type `Expr`.
-The proof is by induction on `e` and case analysis. Note that the tactic `simp [typeCheck]` is applied to all goal generated by the `induction` tactic, and closes
+The proof is by induction on `e` and case analysis. The tactic `rename_i` is used to rename "inaccessible" variables.
+We say a variable is inaccessible if it is introduced by a tactic (e.g., `cases`) or has been shadowed by another variable introduced
+by the user. Note that the tactic `simp [typeCheck]` is applied to all goal generated by the `induction` tactic, and closes
 the cases corresponding to the constructors `Expr.nat` and `Expr.bool`.
 -/
 theorem Expr.typeCheck_complete {e : Expr} : e.typeCheck = .unknown → ¬ HasType e ty := by

src/Init/Data.lean

@@ -43,4 +43,3 @@ import Init.Data.Zero
 import Init.Data.NeZero
 import Init.Data.Function
 import Init.Data.RArray
-import Init.Data.Vector

src/Init/Data/Array/Basic.lean

@@ -13,7 +13,6 @@ import Init.Data.ToString.Basic
 import Init.GetElem
 import Init.Data.List.ToArray
 import Init.Data.Array.Set
-
 universe u v w
 
 /-! ### Array literal syntax -/
@@ -166,15 +165,15 @@ This will perform the update destructively provided that `a` has a reference
 count of 1 when called.
 -/
 @[extern "lean_array_fswap"]
-def swap (a : Array α) (i j : @& Nat) (hi : i < a.size := by get_elem_tactic) (hj : j < a.size := by get_elem_tactic) : Array α :=
+def swap (a : Array α) (i j : @& Fin a.size) : Array α :=
   let v₁ := a[i]
   let v₂ := a[j]
   let a'  := a.set i v₂
-  a'.set j v₁ (Nat.lt_of_lt_of_eq hj (size_set a i v₂ _).symm)
+  a'.set j v₁ (Nat.lt_of_lt_of_eq j.isLt (size_set a i v₂ _).symm)
 
-@[simp] theorem size_swap (a : Array α) (i j : Nat) {hi hj} : (a.swap i j hi hj).size = a.size := by
+@[simp] theorem size_swap (a : Array α) (i j : Fin a.size) : (a.swap i j).size = a.size := by
   show ((a.set i a[j]).set j a[i]
-    (Nat.lt_of_lt_of_eq hj (size_set a i a[j] _).symm)).size = a.size
+    (Nat.lt_of_lt_of_eq j.isLt (size_set a i a[j] _).symm)).size = a.size
   rw [size_set, size_set]
 
 /--
@@ -184,14 +183,12 @@ This will perform the update destructively provided that `a` has a reference
 count of 1 when called.
 -/
 @[extern "lean_array_swap"]
-def swapIfInBounds (a : Array α) (i j : @& Nat) : Array α :=
+def swap! (a : Array α) (i j : @& Nat) : Array α :=
   if h₁ : i < a.size then
-  if h₂ : j < a.size then swap a i j
+  if h₂ : j < a.size then swap a ⟨i, h₁⟩ ⟨j, h₂⟩
   else a
   else a
 
-@[deprecated swapIfInBounds (since := "2024-11-24")] abbrev swap! := @swapIfInBounds
-
 /-! ### GetElem instance for `USize`, backed by `uget` -/
 
 instance : GetElem (Array α) USize α fun xs i => i.toNat < xs.size where
@@ -236,7 +233,7 @@ def ofFn {n} (f : Fin n → α) : Array α := go 0 (mkEmpty n) where
 
 /-- The array `#[0, 1, ..., n - 1]`. -/
 def range (n : Nat) : Array Nat :=
-  ofFn fun (i : Fin n) => i
+  n.fold (flip Array.push) (mkEmpty n)
 
 def singleton (v : α) : Array α :=
   mkArray 1 v
@@ -252,7 +249,7 @@ def get? (a : Array α) (i : Nat) : Option α :=
 def back? (a : Array α) : Option α :=
   a[a.size - 1]?
 
-@[inline] def swapAt (a : Array α) (i : Nat) (v : α) (hi : i < a.size := by get_elem_tactic) : α × Array α :=
+@[inline] def swapAt (a : Array α) (i : Fin a.size) (v : α) : α × Array α :=
   let e := a[i]
   let a := a.set i v
   (e, a)
@@ -260,7 +257,7 @@ def back? (a : Array α) : Option α :=
 @[inline]
 def swapAt! (a : Array α) (i : Nat) (v : α) : α × Array α :=
   if h : i < a.size then
-    swapAt a i v
+    swapAt a ⟨i, h⟩ v
   else
     have : Inhabited (α × Array α) := ⟨(v, a)⟩
     panic! ("index " ++ toString i ++ " out of bounds")
@@ -749,7 +746,7 @@ where
   loop (as : Array α) (i : Nat) (j : Fin as.size) :=
     if h : i < j then
       have := termination h
-      let as := as.swap i j (Nat.lt_trans h j.2)
+      let as := as.swap ⟨i, Nat.lt_trans h j.2⟩ j
       have : j-1 < as.size := by rw [size_swap]; exact Nat.lt_of_le_of_lt (Nat.pred_le _) j.2
       loop as (i+1) ⟨j-1, this⟩
     else
@@ -789,7 +786,7 @@ it has to backshift all elements at positions greater than `i`.-/
 @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
 def eraseIdx (a : Array α) (i : Nat) (h : i < a.size := by get_elem_tactic) : Array α :=
   if h' : i + 1 < a.size then
-    let a' := a.swap (i + 1) i
+    let a' := a.swap ⟨i + 1, h'⟩ ⟨i, h⟩
     a'.eraseIdx (i + 1) (by simp [a', h'])
   else
     a.pop
@@ -836,7 +833,7 @@ def eraseP (as : Array α) (p : α → Bool) : Array α :=
   let rec @[semireducible] -- This is otherwise irreducible because it uses well-founded recursion.
   loop (as : Array α) (j : Fin as.size) :=
     if i < j then
-      let j' : Fin as.size := ⟨j-1, Nat.lt_of_le_of_lt (Nat.pred_le _) j.2⟩
+      let j' := ⟨j-1, Nat.lt_of_le_of_lt (Nat.pred_le _) j.2⟩
       let as := as.swap j' j
       loop as ⟨j', by rw [size_swap]; exact j'.2⟩
     else
@@ -886,12 +883,12 @@ def isPrefixOf [BEq α] (as bs : Array α) : Bool :=
     false
 
 @[semireducible, specialize] -- This is otherwise irreducible because it uses well-founded recursion.
-def zipWithAux (as : Array α) (bs : Array β) (f : α → β → γ) (i : Nat) (cs : Array γ) : Array γ :=
+def zipWithAux (f : α → β → γ) (as : Array α) (bs : Array β) (i : Nat) (cs : Array γ) : Array γ :=
   if h : i < as.size then
     let a := as[i]
     if h : i < bs.size then
       let b := bs[i]
-      zipWithAux as bs f (i+1) <| cs.push <| f a b
+      zipWithAux f as bs (i+1) <| cs.push <| f a b
     else
       cs
   else
@@ -899,23 +896,11 @@ def zipWithAux (as : Array α) (bs : Array β) (f : α → β → γ) (i : Nat)
 decreasing_by simp_wf; decreasing_trivial_pre_omega
 
 @[inline] def zipWith (as : Array α) (bs : Array β) (f : α → β → γ) : Array γ :=
-  zipWithAux as bs f 0 #[]
+  zipWithAux f as bs 0 #[]
 
 def zip (as : Array α) (bs : Array β) : Array (α × β) :=
   zipWith as bs Prod.mk
 
-def zipWithAll (as : Array α) (bs : Array β) (f : Option α → Option β → γ) : Array γ :=
-  go as bs 0 #[]
-where go (as : Array α) (bs : Array β) (i : Nat) (cs : Array γ) :=
-  if i < max as.size bs.size then
-    let a := as[i]?
-    let b := bs[i]?
-    go as bs (i+1) (cs.push (f a b))
-  else
-    cs
-  termination_by max as.size bs.size - i
-  decreasing_by simp_wf; decreasing_trivial_pre_omega
-
 def unzip (as : Array (α × β)) : Array α × Array β :=
   as.foldl (init := (#[], #[])) fun (as, bs) (a, b) => (as.push a, bs.push b)
 

src/Init/Data/Array/BinSearch.lean

@@ -5,64 +5,59 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Array.Basic
-import Init.Omega
 universe u v
 
-namespace Array
+-- TODO: CLEANUP
 
-@[specialize] def binSearchAux {α : Type u} {β : Type v} (lt : α → α → Bool) (found : Option α → β) (as : Array α) (k : α) :
-    (lo : Fin (as.size + 1)) → (hi : Fin as.size) → (lo.1 ≤ hi.1) → β
-  | lo, hi, h =>
-    let m := (lo.1 + hi.1)/2
-    let a := as[m]
-    if lt a k then
-      if h' : m + 1 ≤ hi.1 then
-        binSearchAux lt found as k ⟨m+1, by omega⟩ hi h'
-      else found none
-    else if lt k a then
-      if h' : m = 0 ∨ m - 1 < lo.1 then found none
-      else binSearchAux lt found as k lo ⟨m-1, by omega⟩ (by simp; omega)
-    else found (some a)
-termination_by lo hi => hi.1 - lo.1
+namespace Array
+-- TODO: remove the [Inhabited α] parameters as soon as we have the tactic framework for automating proof generation and using Array.fget
+-- TODO: remove `partial` using well-founded recursion
+
+@[specialize] partial def binSearchAux {α : Type u} {β : Type v} [Inhabited β] (lt : α → α → Bool) (found : Option α → β) (as : Array α) (k : α) : Nat → Nat → β
+  | lo, hi =>
+    if lo <= hi then
+      let _ := Inhabited.mk k
+      let m := (lo + hi)/2
+      let a := as.get! m
+      if lt a k then binSearchAux lt found as k (m+1) hi
+      else if lt k a then
+        if m == 0 then found none
+        else binSearchAux lt found as k lo (m-1)
+      else found (some a)
+    else found none
 
 @[inline] def binSearch {α : Type} (as : Array α) (k : α) (lt : α → α → Bool) (lo := 0) (hi := as.size - 1) : Option α :=
-  if h : lo < as.size then
+  if lo < as.size then
     let hi := if hi < as.size then hi else as.size - 1
-    if w : lo ≤ hi then
-      binSearchAux lt id as k ⟨lo, by omega⟩ ⟨hi, by simp [hi]; split <;> omega⟩ (by simp [hi]; omega)
-    else
-      none
+    binSearchAux lt id as k lo hi
   else
     none
 
 @[inline] def binSearchContains {α : Type} (as : Array α) (k : α) (lt : α → α → Bool) (lo := 0) (hi := as.size - 1) : Bool :=
-  if h : lo < as.size then
+  if lo < as.size then
     let hi := if hi < as.size then hi else as.size - 1
-    if w : lo ≤ hi then
-      binSearchAux lt Option.isSome as k ⟨lo, by omega⟩ ⟨hi, by simp [hi]; split <;> omega⟩ (by simp [hi]; omega)
-    else
-      false
+    binSearchAux lt Option.isSome as k lo hi
   else
     false
 
-@[specialize] private def binInsertAux {α : Type u} {m : Type u → Type v} [Monad m]
+@[specialize] private partial def binInsertAux {α : Type u} {m : Type u → Type v} [Monad m]
     (lt : α → α → Bool)
     (merge : α → m α)
     (add : Unit → m α)
     (as : Array α)
-    (k : α) : (lo : Fin as.size) → (hi : Fin as.size) → (lo.1 ≤ hi.1) → (lt as[lo] k) → m (Array α)
-  | lo, hi, h, w =>
-    let mid    := (lo.1 + hi.1)/2
-    let midVal := as[mid]
-    if w₁ : lt midVal k then
-      if h' : mid = lo then do let v ← add (); pure <| as.insertIdx (lo+1) v
-      else binInsertAux lt merge add as k ⟨mid, by omega⟩ hi (by simp; omega) w₁
-    else if w₂ : lt k midVal then
-      have : mid ≠ lo := fun z => by simp [midVal, z] at w₁; simp_all
-      binInsertAux lt merge add as k lo ⟨mid, by omega⟩ (by simp; omega) w
+    (k : α) : Nat → Nat → m (Array α)
+  | lo, hi =>
+    let _ := Inhabited.mk k
+    -- as[lo] < k < as[hi]
+    let mid    := (lo + hi)/2
+    let midVal := as.get! mid
+    if lt midVal k then
+      if mid == lo then do let v ← add (); pure <| as.insertIdx! (lo+1) v
+      else binInsertAux lt merge add as k mid hi
+    else if lt k midVal then
+      binInsertAux lt merge add as k lo mid
     else do
       as.modifyM mid <| fun v => merge v
-termination_by lo hi => hi.1 - lo.1
 
 @[specialize] def binInsertM {α : Type u} {m : Type u → Type v} [Monad m]
     (lt : α → α → Bool)
@@ -70,12 +65,13 @@ termination_by lo hi => hi.1 - lo.1
     (add : Unit → m α)
     (as : Array α)
     (k : α) : m (Array α) :=
-  if h : as.size = 0 then do let v ← add (); pure <| as.push v
-  else if lt k as[0] then do let v ← add (); pure <| as.insertIdx 0 v
-  else if h' : !lt as[0] k then as.modifyM 0 <| merge
-  else if lt as[as.size - 1] k then do let v ← add (); pure <| as.push v
-  else if !lt k as[as.size - 1] then as.modifyM (as.size - 1) <| merge
-  else binInsertAux lt merge add as k ⟨0, by omega⟩ ⟨as.size - 1, by omega⟩ (by simp) (by simpa using h')
+  let _ := Inhabited.mk k
+  if as.isEmpty then do let v ← add (); pure <| as.push v
+  else if lt k (as.get! 0) then do let v ← add (); pure <| as.insertIdx! 0 v
+  else if !lt (as.get! 0) k then as.modifyM 0 <| merge
+  else if lt as.back! k then do let v ← add (); pure <| as.push v
+  else if !lt k as.back! then as.modifyM (as.size - 1) <| merge
+  else binInsertAux lt merge add as k 0 (as.size - 1)
 
 @[inline] def binInsert {α : Type u} (lt : α → α → Bool) (as : Array α) (k : α) : Array α :=
   Id.run <| binInsertM lt (fun _ => k) (fun _ => k) as k

src/Init/Data/Array/Bootstrap.lean

@@ -23,7 +23,7 @@ theorem foldlM_toList.aux [Monad m]
   · cases Nat.not_le_of_gt ‹_› (Nat.zero_add _ ▸ H)
   · rename_i i; rw [Nat.succ_add] at H
     simp [foldlM_toList.aux f arr i (j+1) H]
-    rw (occs := [2]) [← List.getElem_cons_drop_succ_eq_drop ‹_›]
+    rw (occs := .pos [2]) [← List.getElem_cons_drop_succ_eq_drop ‹_›]
     rfl
   · rw [List.drop_of_length_le (Nat.ge_of_not_lt ‹_›)]; rfl
 

src/Init/Data/Array/DecidableEq.lean

@@ -6,6 +6,7 @@ Authors: Leonardo de Moura
 prelude
 import Init.Data.Array.Basic
 import Init.Data.BEq
+import Init.Data.Nat.Lemmas
 import Init.Data.List.Nat.BEq
 import Init.ByCases
 

src/Init/Data/Array/InsertionSort.lean

@@ -6,7 +6,7 @@ Authors: Leonardo de Moura
 prelude
 import Init.Data.Array.Basic
 
-@[inline] def Array.insertionSort (a : Array α) (lt : α → α → Bool := by exact (· < ·)) : Array α :=
+@[inline] def Array.insertionSort (a : Array α) (lt : α → α → Bool) : Array α :=
   traverse a 0 a.size
 where
   @[specialize] traverse (a : Array α) (i : Nat) (fuel : Nat) : Array α :=
@@ -23,6 +23,6 @@ where
     | j'+1 =>
       have h' : j' < a.size := by subst j; exact Nat.lt_trans (Nat.lt_succ_self _) h
       if lt a[j] a[j'] then
-        swapLoop (a.swap j j') j' (by rw [size_swap]; assumption; done)
+        swapLoop (a.swap ⟨j, h⟩ ⟨j', h'⟩) j' (by rw [size_swap]; assumption; done)
       else
         a

src/Init/Data/Array/Lemmas.lean

@@ -343,8 +343,8 @@ theorem isPrefixOfAux_toArray_zero [BEq α] (l₁ l₂ : List α) (hle : l₁.le
         rw [ih]
         simp_all
 
-theorem zipWithAux_toArray_succ (as : List α) (bs : List β) (f : α → β → γ) (i : Nat) (cs : Array γ) :
-    zipWithAux as.toArray bs.toArray f (i + 1) cs = zipWithAux as.tail.toArray bs.tail.toArray f i cs := by
+theorem zipWithAux_toArray_succ (f : α → β → γ) (as : List α) (bs : List β) (i : Nat) (cs : Array γ) :
+    zipWithAux f as.toArray bs.toArray (i + 1) cs = zipWithAux f as.tail.toArray bs.tail.toArray i cs := by
   rw [zipWithAux]
   conv => rhs; rw [zipWithAux]
   simp only [size_toArray, getElem_toArray, length_tail, getElem_tail]
@@ -355,8 +355,8 @@ theorem zipWithAux_toArray_succ (as : List α) (bs : List β) (f : α → β →
       rw [dif_neg (by omega)]
   · rw [dif_neg (by omega)]
 
-theorem zipWithAux_toArray_succ' (as : List α) (bs : List β) (f : α → β → γ) (i : Nat) (cs : Array γ) :
-    zipWithAux as.toArray bs.toArray f (i + 1) cs = zipWithAux (as.drop (i+1)).toArray (bs.drop (i+1)).toArray f 0 cs := by
+theorem zipWithAux_toArray_succ' (f : α → β → γ) (as : List α) (bs : List β) (i : Nat) (cs : Array γ) :
+    zipWithAux f as.toArray bs.toArray (i + 1) cs = zipWithAux f (as.drop (i+1)).toArray (bs.drop (i+1)).toArray 0 cs := by
   induction i generalizing as bs cs with
   | zero => simp [zipWithAux_toArray_succ]
   | succ i ih =>
@@ -364,7 +364,7 @@ theorem zipWithAux_toArray_succ' (as : List α) (bs : List β) (f : α → β
     simp
 
 theorem zipWithAux_toArray_zero (f : α → β → γ) (as : List α) (bs : List β) (cs : Array γ) :
-    zipWithAux as.toArray bs.toArray f 0 cs = cs ++ (List.zipWith f as bs).toArray := by
+    zipWithAux f as.toArray bs.toArray 0 cs = cs ++ (List.zipWith f as bs).toArray := by
   rw [Array.zipWithAux]
   match as, bs with
   | [], _ => simp
@@ -372,7 +372,7 @@ theorem zipWithAux_toArray_zero (f : α → β → γ) (as : List α) (bs : List
   | a :: as, b :: bs =>
     simp [zipWith_cons_cons, zipWithAux_toArray_succ', zipWithAux_toArray_zero, push_append_toArray]
 
-@[simp] theorem zipWith_toArray (as : List α) (bs : List β) (f : α → β → γ) :
+@[simp] theorem zipWith_toArray (f : α → β → γ) (as : List α) (bs : List β) :
     Array.zipWith as.toArray bs.toArray f = (List.zipWith f as bs).toArray := by
   rw [Array.zipWith]
   simp [zipWithAux_toArray_zero]
@@ -381,44 +381,6 @@ theorem zipWithAux_toArray_zero (f : α → β → γ) (as : List α) (bs : List
     Array.zip as.toArray bs.toArray = (List.zip as bs).toArray := by
   simp [Array.zip, zipWith_toArray, zip]
 
-theorem zipWithAll_go_toArray (as : List α) (bs : List β) (f : Option α → Option β → γ) (i : Nat) (cs : Array γ) :
-    zipWithAll.go f as.toArray bs.toArray i cs = cs ++ (List.zipWithAll f (as.drop i) (bs.drop i)).toArray := by
-  unfold zipWithAll.go
-  split <;> rename_i h
-  · rw [zipWithAll_go_toArray]
-    simp at h
-    simp only [getElem?_toArray, push_append_toArray]
-    if ha : i < as.length then
-      if hb : i < bs.length then
-        rw [List.drop_eq_getElem_cons ha, List.drop_eq_getElem_cons hb]
-        simp only [ha, hb, getElem?_eq_getElem, zipWithAll_cons_cons]
-      else
-        simp only [Nat.not_lt] at hb
-        rw [List.drop_eq_getElem_cons ha]
-        rw [(drop_eq_nil_iff (l := bs)).mpr (by omega), (drop_eq_nil_iff (l := bs)).mpr (by omega)]
-        simp only [zipWithAll_nil, map_drop, map_cons]
-        rw [getElem?_eq_getElem ha]
-        rw [getElem?_eq_none hb]
-    else
-      if hb : i < bs.length then
-        simp only [Nat.not_lt] at ha
-        rw [List.drop_eq_getElem_cons hb]
-        rw [(drop_eq_nil_iff (l := as)).mpr (by omega), (drop_eq_nil_iff (l := as)).mpr (by omega)]
-        simp only [nil_zipWithAll, map_drop, map_cons]
-        rw [getElem?_eq_getElem hb]
-        rw [getElem?_eq_none ha]
-      else
-        omega
-  · simp only [size_toArray, Nat.not_lt] at h
-    rw [drop_eq_nil_of_le (by omega), drop_eq_nil_of_le (by omega)]
-    simp
-  termination_by max as.length bs.length - i
-  decreasing_by simp_wf; decreasing_trivial_pre_omega
-
-@[simp] theorem zipWithAll_toArray (f : Option α → Option β → γ) (as : List α) (bs : List β) :
-    Array.zipWithAll as.toArray bs.toArray f = (List.zipWithAll f as bs).toArray := by
-  simp [Array.zipWithAll, zipWithAll_go_toArray]
-
 end List
 
 namespace Array
@@ -551,10 +513,10 @@ theorem getElem?_len_le (a : Array α) {i : Nat} (h : a.size ≤ i) : a[i]? = no
 theorem getD_get? (a : Array α) (i : Nat) (d : α) :
   Option.getD a[i]? d = if p : i < a.size then a[i]'p else d := by
   if h : i < a.size then
-    simp [setIfInBounds, h, getElem?_def]
+    simp [setD, h, getElem?_def]
   else
     have p : i ≥ a.size := Nat.le_of_not_gt h
-    simp [setIfInBounds, getElem?_len_le _ p, h]
+    simp [setD, getElem?_len_le _ p, h]
 
 @[simp] theorem getD_eq_get? (a : Array α) (n d) : a.getD n d = (a[n]?).getD d := by
   simp only [getD, get_eq_getElem, get?_eq_getElem?]; split <;> simp [getD_get?, *]
@@ -590,32 +552,31 @@ theorem getElem_set (a : Array α) (i : Nat) (h' : i < a.size) (v : α) (j : Nat
     (ne : i ≠ j) : (a.set i v)[j]? = a[j]? := by
   by_cases h : j < a.size <;> simp [getElem?_lt, getElem?_ge, Nat.ge_of_not_lt, ne, h]
 
-/-! # setIfInBounds -/
+/-! # setD -/
 
-@[simp] theorem set!_is_setIfInBounds : @set! = @setIfInBounds := rfl
+@[simp] theorem set!_is_setD : @set! = @setD := rfl
 
-@[simp] theorem size_setIfInBounds (a : Array α) (index : Nat) (val : α) :
-    (Array.setIfInBounds a index val).size = a.size := by
+@[simp] theorem size_setD (a : Array α) (index : Nat) (val : α) :
+    (Array.setD a index val).size = a.size := by
   if h : index < a.size  then
-    simp [setIfInBounds, h]
+    simp [setD, h]
   else
-    simp [setIfInBounds, h]
+    simp [setD, h]
 
-@[simp] theorem getElem_setIfInBounds_eq (a : Array α) {i : Nat} (v : α) (h : _) :
-    (setIfInBounds a i v)[i]'h = v := by
+@[simp] theorem getElem_setD_eq (a : Array α) {i : Nat} (v : α) (h : _) :
+    (setD a i v)[i]'h = v := by
   simp at h
-  simp only [setIfInBounds, h, ↓reduceDIte, getElem_set_eq]
+  simp only [setD, h, ↓reduceDIte, getElem_set_eq]
 
 @[simp]
-theorem getElem?_setIfInBounds_eq (a : Array α) {i : Nat} (p : i < a.size) (v : α) :
-    (a.setIfInBounds i v)[i]? = some v := by
+theorem getElem?_setD_eq (a : Array α) {i : Nat} (p : i < a.size) (v : α) : (a.setD i v)[i]? = some v := by
   simp [getElem?_lt, p]
 
 /-- Simplifies a normal form from `get!` -/
-@[simp] theorem getD_get?_setIfInBounds (a : Array α) (i : Nat) (v d : α) :
-    Option.getD (setIfInBounds a i v)[i]? d = if i < a.size then v else d := by
+@[simp] theorem getD_get?_setD (a : Array α) (i : Nat) (v d : α) :
+    Option.getD (setD a i v)[i]? d = if i < a.size then v else d := by
   by_cases h : i < a.size <;>
-    simp [setIfInBounds, Nat.not_lt_of_le, h,  getD_get?]
+    simp [setD, Nat.not_lt_of_le, h,  getD_get?]
 
 /-! # ofFn -/
 
@@ -660,19 +621,6 @@ theorem getElem?_ofFn (f : Fin n → α) (i : Nat) :
     (ofFn f)[i]? = if h : i < n then some (f ⟨i, h⟩) else none := by
   simp [getElem?_def]
 
-@[simp] theorem ofFn_zero (f : Fin 0 → α) : ofFn f = #[] := rfl
-
-theorem ofFn_succ (f : Fin (n+1) → α) :
-    ofFn f = (ofFn (fun (i : Fin n) => f i.castSucc)).push (f ⟨n, by omega⟩) := by
-  ext i h₁ h₂
-  · simp
-  · simp [getElem_push]
-    split <;> rename_i h₃
-    · rfl
-    · congr
-      simp at h₁ h₂
-      omega
-
 /-! # mkArray -/
 
 @[simp] theorem size_mkArray (n : Nat) (v : α) : (mkArray n v).size = n :=
@@ -807,32 +755,32 @@ theorem get_set (a : Array α) (i : Nat) (hi : i < a.size) (j : Nat) (hj : j < a
     (h : i ≠ j) : (a.set i v)[j]'(by simp [*]) = a[j] := by
   simp only [set, getElem_eq_getElem_toList, List.getElem_set_ne h]
 
-theorem getElem_setIfInBounds (a : Array α) (i : Nat) (v : α) (h : i < (setIfInBounds a i v).size) :
-    (setIfInBounds a i v)[i] = v := by
+theorem getElem_setD (a : Array α) (i : Nat) (v : α) (h : i < (setD a i v).size) :
+    (setD a i v)[i] = v := by
   simp at h
-  simp only [setIfInBounds, h, ↓reduceDIte, getElem_set_eq]
+  simp only [setD, h, ↓reduceDIte, getElem_set_eq]
 
 theorem set_set (a : Array α) (i : Nat) (h) (v v' : α) :
     (a.set i v h).set i v' (by simp [h]) = a.set i v' := by simp [set, List.set_set]
 
 private theorem fin_cast_val (e : n = n') (i : Fin n) : e ▸ i = ⟨i.1, e ▸ i.2⟩ := by cases e; rfl
 
-theorem swap_def (a : Array α) (i j : Nat) (hi hj) :
-    a.swap i j hi hj = (a.set i a[j]).set j a[i] (by simpa using hj) := by
+theorem swap_def (a : Array α) (i j : Fin a.size) :
+    a.swap i j = (a.set i a[j]).set j a[i] := by
   simp [swap, fin_cast_val]
 
-@[simp] theorem toList_swap (a : Array α) (i j : Nat) (hi hj) :
-    (a.swap i j hi hj).toList = (a.toList.set i a[j]).set j a[i] := by simp [swap_def]
+@[simp] theorem toList_swap (a : Array α) (i j : Fin a.size) :
+    (a.swap i j).toList = (a.toList.set i a[j]).set j a[i] := by simp [swap_def]
 
-theorem getElem?_swap (a : Array α) (i j : Nat) (hi hj) (k : Nat) : (a.swap i j hi hj)[k]? =
-    if j = k then some a[i] else if i = k then some a[j] else a[k]? := by
+theorem getElem?_swap (a : Array α) (i j : Fin a.size) (k : Nat) : (a.swap i j)[k]? =
+    if j = k then some a[i.1] else if i = k then some a[j.1] else a[k]? := by
   simp [swap_def, get?_set, ← getElem_fin_eq_getElem_toList]
 
-@[simp] theorem swapAt_def (a : Array α) (i : Nat) (v : α) (hi) :
-    a.swapAt i v hi = (a[i], a.set i v) := rfl
+@[simp] theorem swapAt_def (a : Array α) (i : Fin a.size) (v : α) :
+    a.swapAt i v = (a[i.1], a.set i v) := rfl
 
-@[simp] theorem size_swapAt (a : Array α) (i : Nat) (v : α) (hi) :
-    (a.swapAt i v hi).2.size = a.size := by simp [swapAt_def]
+@[simp] theorem size_swapAt (a : Array α) (i : Fin a.size) (v : α) :
+    (a.swapAt i v).2.size = a.size := by simp [swapAt_def]
 
 @[simp]
 theorem swapAt!_def (a : Array α) (i : Nat) (v : α) (h : i < a.size) :
@@ -879,10 +827,8 @@ theorem eq_push_of_size_ne_zero {as : Array α} (h : as.size ≠ 0) :
 
 theorem size_eq_length_toList (as : Array α) : as.size = as.toList.length := rfl
 
-@[simp] theorem size_swapIfInBounds (a : Array α) (i j) :
-    (a.swapIfInBounds i j).size = a.size := by unfold swapIfInBounds; split <;> (try split) <;> simp [size_swap]
-
-@[deprecated size_swapIfInBounds (since := "2024-11-24")] abbrev size_swap! := @size_swapIfInBounds
+@[simp] theorem size_swap! (a : Array α) (i j) :
+    (a.swap! i j).size = a.size := by unfold swap!; split <;> (try split) <;> simp [size_swap]
 
 @[simp] theorem size_reverse (a : Array α) : a.reverse.size = a.size := by
   let rec go (as : Array α) (i j) : (reverse.loop as i j).size = as.size := by
@@ -894,10 +840,16 @@ theorem size_eq_length_toList (as : Array α) : as.size = as.toList.length := rf
   simp only [reverse]; split <;> simp [go]
 
 @[simp] theorem size_range {n : Nat} : (range n).size = n := by
-  induction n <;> simp [range]
+  unfold range
+  induction n with
+  | zero      => simp [Nat.fold]
+  | succ k ih =>
+    rw [Nat.fold, flip]
+    simp only [mkEmpty_eq, size_push] at *
+    omega
 
 @[simp] theorem toList_range (n : Nat) : (range n).toList = List.range n := by
-  apply List.ext_getElem <;> simp [range]
+  induction n <;> simp_all [range, Nat.fold, flip, List.range_succ]
 
 @[simp]
 theorem getElem_range {n : Nat} {x : Nat} (h : x < (Array.range n).size) : (Array.range n)[x] = x := by
@@ -1093,34 +1045,6 @@ theorem foldr_congr {as bs : Array α} (h₀ : as = bs) {f g : α → β → β}
     as.foldr f a start stop = bs.foldr g b start' stop' := by
   congr
 
-theorem foldl_eq_foldlM (f : β → α → β) (b) (l : Array α) :
-    l.foldl f b = l.foldlM (m := Id) f b := by
-  cases l
-  simp [List.foldl_eq_foldlM]
-
-theorem foldr_eq_foldrM (f : α → β → β) (b) (l : Array α) :
-    l.foldr f b = l.foldrM (m := Id) f b := by
-  cases l
-  simp [List.foldr_eq_foldrM]
-
-@[simp] theorem id_run_foldlM (f : β → α → Id β) (b) (l : Array α) :
-    Id.run (l.foldlM f b) = l.foldl f b := (foldl_eq_foldlM f b l).symm
-
-@[simp] theorem id_run_foldrM (f : α → β → Id β) (b) (l : Array α) :
-    Id.run (l.foldrM f b) = l.foldr f b := (foldr_eq_foldrM f b l).symm
-
-theorem foldl_hom (f : α₁ → α₂) (g₁ : α₁ → β → α₁) (g₂ : α₂ → β → α₂) (l : Array β) (init : α₁)
-    (H : ∀ x y, g₂ (f x) y = f (g₁ x y)) : l.foldl g₂ (f init) = f (l.foldl g₁ init) := by
-  cases l
-  simp
-  rw [List.foldl_hom _ _ _ _ _ H]
-
-theorem foldr_hom (f : β₁ → β₂) (g₁ : α → β₁ → β₁) (g₂ : α → β₂ → β₂) (l : Array α) (init : β₁)
-    (H : ∀ x y, g₂ x (f y) = f (g₁ x y)) : l.foldr g₂ (f init) = f (l.foldr g₁ init) := by
-  cases l
-  simp
-  rw [List.foldr_hom _ _ _ _ _ H]
-
 /-! ### map -/
 
 @[simp] theorem mem_map {f : α → β} {l : Array α} : b ∈ l.map f ↔ ∃ a, a ∈ l ∧ f a = b := by
@@ -1672,30 +1596,28 @@ instance [DecidableEq α] (a : α) (as : Array α) : Decidable (a ∈ as) :=
 
 open Fin
 
-@[simp] theorem getElem_swap_right (a : Array α) {i j : Nat} {hi hj} :
-    (a.swap i j hi hj)[j]'(by simpa using hj) = a[i] := by
+@[simp] theorem getElem_swap_right (a : Array α) {i j : Fin a.size} : (a.swap i j)[j.1] = a[i] := by
   simp [swap_def, getElem_set]
 
-@[simp] theorem getElem_swap_left (a : Array α) {i j : Nat} {hi hj} :
-    (a.swap i j hi hj)[i]'(by simpa using hi) = a[j] := by
+@[simp] theorem getElem_swap_left (a : Array α) {i j : Fin a.size} : (a.swap i j)[i.1] = a[j] := by
   simp +contextual [swap_def, getElem_set]
 
-@[simp] theorem getElem_swap_of_ne (a : Array α) {i j : Nat} {hi hj} (hp : p < a.size)
-    (hi' : p ≠ i) (hj' : p ≠ j) : (a.swap i j hi hj)[p]'(a.size_swap .. |>.symm ▸ hp) = a[p] := by
-  simp [swap_def, getElem_set, hi'.symm, hj'.symm]
+@[simp] theorem getElem_swap_of_ne (a : Array α) {i j : Fin a.size} (hp : p < a.size)
+    (hi : p ≠ i) (hj : p ≠ j) : (a.swap i j)[p]'(a.size_swap .. |>.symm ▸ hp) = a[p] := by
+  simp [swap_def, getElem_set, hi.symm, hj.symm]
 
-theorem getElem_swap' (a : Array α) (i j : Nat) {hi hj} (k : Nat) (hk : k < a.size) :
-    (a.swap i j hi hj)[k]'(by simp_all) = if k = i then a[j] else if k = j then a[i] else a[k] := by
+theorem getElem_swap' (a : Array α) (i j : Fin a.size) (k : Nat) (hk : k < a.size) :
+    (a.swap i j)[k]'(by simp_all) = if k = i then a[j] else if k = j then a[i] else a[k] := by
   split
   · simp_all only [getElem_swap_left]
   · split <;> simp_all
 
-theorem getElem_swap (a : Array α) (i j : Nat) {hi hj}(k : Nat) (hk : k < (a.swap i j).size) :
-    (a.swap i j hi hj)[k] = if k = i then a[j] else if k = j then a[i] else a[k]'(by simp_all) := by
+theorem getElem_swap (a : Array α) (i j : Fin a.size) (k : Nat) (hk : k < (a.swap i j).size) :
+    (a.swap i j)[k] = if k = i then a[j] else if k = j then a[i] else a[k]'(by simp_all) := by
   apply getElem_swap'
 
-@[simp] theorem swap_swap (a : Array α) {i j : Nat} (hi hj) :
-    (a.swap i j hi hj).swap i j ((a.size_swap ..).symm ▸ hi) ((a.size_swap ..).symm ▸ hj) = a := by
+@[simp] theorem swap_swap (a : Array α) {i j : Fin a.size} :
+    (a.swap i j).swap ⟨i.1, (a.size_swap ..).symm ▸ i.2⟩ ⟨j.1, (a.size_swap ..).symm ▸ j.2⟩ = a := by
   apply ext
   · simp only [size_swap]
   · intros
@@ -1704,7 +1626,7 @@ theorem getElem_swap (a : Array α) (i j : Nat) {hi hj}(k : Nat) (hk : k < (a.sw
     · simp_all
     · split <;> simp_all
 
-theorem swap_comm (a : Array α) {i j : Nat} {hi hj} : a.swap i j hi hj = a.swap j i hj hi := by
+theorem swap_comm (a : Array α) {i j : Fin a.size} : a.swap i j = a.swap j i := by
   apply ext
   · simp only [size_swap]
   · intros
@@ -1739,20 +1661,6 @@ theorem eraseIdx_eq_eraseIdxIfInBounds {a : Array α} {i : Nat} (h : i < a.size)
     (Array.zip as bs).toList = List.zip as.toList bs.toList := by
   simp [zip, toList_zipWith, List.zip]
 
-@[simp] theorem toList_zipWithAll (f : Option α → Option β → γ) (as : Array α) (bs : Array β) :
-    (Array.zipWithAll as bs f).toList = List.zipWithAll f as.toList bs.toList := by
-  cases as
-  cases bs
-  simp
-
-@[simp] theorem size_zipWith (as : Array α) (bs : Array β) (f : α → β → γ) :
-    (as.zipWith bs f).size = min as.size bs.size := by
-  rw [size_eq_length_toList, toList_zipWith, List.length_zipWith]
-
-@[simp] theorem size_zip (as : Array α) (bs : Array β) :
-    (as.zip bs).size = min as.size bs.size :=
-  as.size_zipWith bs Prod.mk
-
 /-! ### findSomeM?, findM?, findSome?, find? -/
 
 @[simp] theorem findSomeM?_toList [Monad m] [LawfulMonad m] (p : α → m (Option β)) (as : Array α) :
@@ -1827,10 +1735,10 @@ Our goal is to have `simp` "pull `List.toArray` outwards" as much as possible.
   apply ext'
   simp
 
-@[simp] theorem setIfInBounds_toArray (l : List α) (i : Nat) (a : α) :
-    l.toArray.setIfInBounds i a  = (l.set i a).toArray := by
+@[simp] theorem setD_toArray (l : List α) (i : Nat) (a : α) :
+    l.toArray.setD i a  = (l.set i a).toArray := by
   apply ext'
-  simp only [setIfInBounds]
+  simp only [setD]
   split
   · simp
   · simp_all [List.set_eq_of_length_le]
@@ -1875,8 +1783,8 @@ theorem all_toArray (p : α → Bool) (l : List α) : l.toArray.all p = l.all p
   subst h
   rw [all_toList]
 
-@[simp] theorem swap_toArray (l : List α) (i j : Nat) {hi hj}:
-    l.toArray.swap i j hi hj = ((l.set i l[j]).set j l[i]).toArray := by
+@[simp] theorem swap_toArray (l : List α) (i j : Fin l.toArray.size) :
+    l.toArray.swap i j = ((l.set i l[j]).set j l[i]).toArray := by
   apply ext'
   simp
 
@@ -2060,20 +1968,6 @@ theorem foldr_filterMap (f : α → Option β) (g : β → γ → γ) (l : Array
   simp [List.foldr_filterMap]
   rfl
 
-theorem foldl_map' (g : α → β) (f : α → α → α) (f' : β → β → β) (a : α) (l : Array α)
-    (h : ∀ x y, f' (g x) (g y) = g (f x y)) :
-    (l.map g).foldl f' (g a) = g (l.foldl f a) := by
-  cases l
-  simp
-  rw [List.foldl_map' _ _ _ _ _ h]
-
-theorem foldr_map' (g : α → β) (f : α → α → α) (f' : β → β → β) (a : α) (l : List α)
-    (h : ∀ x y, f' (g x) (g y) = g (f x y)) :
-    (l.map g).foldr f' (g a) = g (l.foldr f a) := by
-  cases l
-  simp
-  rw [List.foldr_map' _ _ _ _ _ h]
-
 /-! ### flatten -/
 
 @[simp] theorem flatten_empty : flatten (#[] : Array (Array α)) = #[] := rfl
@@ -2196,8 +2090,6 @@ theorem toArray_concat {as : List α} {x : α} :
 
 @[deprecated back!_toArray (since := "2024-10-31")] abbrev back_toArray := @back!_toArray
 
-@[deprecated setIfInBounds_toArray (since := "2024-11-24")] abbrev setD_toArray := @setIfInBounds_toArray
-
 end List
 
 namespace Array
@@ -2343,11 +2235,4 @@ abbrev get_swap' := @getElem_swap'
 @[deprecated eq_push_pop_back!_of_size_ne_zero (since := "2024-10-31")]
 abbrev eq_push_pop_back_of_size_ne_zero := @eq_push_pop_back!_of_size_ne_zero
 
-@[deprecated set!_is_setIfInBounds (since := "2024-11-24")] abbrev set_is_setIfInBounds := @set!_is_setIfInBounds
-@[deprecated size_setIfInBounds (since := "2024-11-24")] abbrev size_setD := @size_setIfInBounds
-@[deprecated getElem_setIfInBounds_eq (since := "2024-11-24")] abbrev getElem_setD_eq := @getElem_setIfInBounds_eq
-@[deprecated getElem?_setIfInBounds_eq (since := "2024-11-24")] abbrev get?_setD_eq := @getElem?_setIfInBounds_eq
-@[deprecated getD_get?_setIfInBounds (since := "2024-11-24")] abbrev getD_setD := @getD_get?_setIfInBounds
-@[deprecated getElem_setIfInBounds (since := "2024-11-24")] abbrev getElem_setD := @getElem_setIfInBounds
-
 end Array

src/Init/Data/Array/QSort.lean

@@ -13,19 +13,19 @@ namespace Array
 def qpartition (as : Array α) (lt : α → α → Bool) (lo hi : Nat) : Nat × Array α :=
   if h : as.size = 0 then (0, as) else have : Inhabited α := ⟨as[0]'(by revert h; cases as.size <;> simp)⟩ -- TODO: remove
   let mid := (lo + hi) / 2
-  let as  := if lt (as.get! mid) (as.get! lo) then as.swapIfInBounds lo mid else as
-  let as  := if lt (as.get! hi)  (as.get! lo) then as.swapIfInBounds lo hi  else as
-  let as  := if lt (as.get! mid) (as.get! hi) then as.swapIfInBounds mid hi else as
+  let as  := if lt (as.get! mid) (as.get! lo) then as.swap! lo mid else as
+  let as  := if lt (as.get! hi)  (as.get! lo) then as.swap! lo hi  else as
+  let as  := if lt (as.get! mid) (as.get! hi) then as.swap! mid hi else as
   let pivot := as.get! hi
   let rec loop (as : Array α) (i j : Nat) :=
     if h : j < hi then
       if lt (as.get! j) pivot then
-        let as := as.swapIfInBounds i j
+        let as := as.swap! i j
         loop as (i+1) (j+1)
       else
         loop as i (j+1)
     else
-      let as := as.swapIfInBounds i hi
+      let as := as.swap! i hi
       (i, as)
     termination_by hi - j
     decreasing_by all_goals simp_wf; decreasing_trivial_pre_omega

src/Init/Data/Array/Set.lean

@@ -25,11 +25,9 @@ Set an element in an array, or do nothing if the index is out of bounds.
 This will perform the update destructively provided that `a` has a reference
 count of 1 when called.
 -/
-@[inline] def Array.setIfInBounds (a : Array α) (i : Nat) (v : α) : Array α :=
+@[inline] def Array.setD (a : Array α) (i : Nat) (v : α) : Array α :=
   dite (LT.lt i a.size) (fun h => a.set i v h) (fun _ => a)
 
-@[deprecated Array.setIfInBounds (since := "2024-11-24")] abbrev Array.setD := @Array.setIfInBounds
-
 /--
 Set an element in an array, or panic if the index is out of bounds.
 
@@ -38,4 +36,4 @@ count of 1 when called.
 -/
 @[extern "lean_array_set"]
 def Array.set! (a : Array α) (i : @& Nat) (v : α) : Array α :=
-  Array.setIfInBounds a i v
+  Array.setD a i v

src/Init/Data/Array/Subarray/Split.lean

@@ -23,13 +23,16 @@ def split (s : Subarray α) (i : Fin s.size.succ) : (Subarray α × Subarray α)
   let ⟨i', isLt⟩ := i
   have := s.start_le_stop
   have := s.stop_le_array_size
+  have : i' ≤ s.stop - s.start := Nat.lt_succ.mp isLt
+  have : s.start + i' ≤ s.stop := by omega
+  have : s.start + i' ≤ s.array.size := by omega
   have : s.start + i' ≤ s.stop := by
     simp only [size] at isLt
     omega
   let pre := {s with
     stop := s.start + i',
     start_le_stop := by omega,
-    stop_le_array_size := by omega
+    stop_le_array_size := by assumption
   }
   let post := {s with
     start := s.start + i'
@@ -45,7 +48,9 @@ def drop (arr : Subarray α) (i : Nat) : Subarray α where
   array := arr.array
   start := min (arr.start + i) arr.stop
   stop := arr.stop
-  start_le_stop := by omega
+  start_le_stop := by
+    rw [Nat.min_def]
+    split <;> simp only [Nat.le_refl, *]
   stop_le_array_size := arr.stop_le_array_size
 
 /--
@@ -58,7 +63,9 @@ def take (arr : Subarray α) (i : Nat) : Subarray α where
   stop := min (arr.start + i) arr.stop
   start_le_stop := by
     have := arr.start_le_stop
-    omega
+    rw [Nat.min_def]
+    split <;> omega
   stop_le_array_size := by
     have := arr.stop_le_array_size
-    omega
+    rw [Nat.min_def]
+    split <;> omega

src/Init/Data/BitVec/Bitblast.lean

@@ -346,10 +346,6 @@ theorem getMsbD_sub {i : Nat} {i_lt : i < w} {x y : BitVec w} :
   · rfl
   · omega
 
-theorem getElem_sub {i : Nat} {x y : BitVec w} (h : i < w) :
-    (x - y)[i] = (x[i] ^^ ((~~~y + 1#w)[i] ^^ carry i x (~~~y + 1#w) false)) := by
-  simp [← getLsbD_eq_getElem, getLsbD_sub, h]
-
 theorem msb_sub {x y: BitVec w} :
     (x - y).msb
       = (x.msb ^^ ((~~~y + 1#w).msb ^^ carry (w - 1 - 0) x (~~~y + 1#w) false)) := by
@@ -414,10 +410,6 @@ theorem getLsbD_neg {i : Nat} {x : BitVec w} :
   · have h_ge : w ≤ i := by omega
     simp [getLsbD_ge _ _ h_ge, h_ge, hi]
 
-theorem getElem_neg {i : Nat} {x : BitVec w} (h : i < w) :
-    (-x)[i] = (x[i] ^^ decide (∃ j < i, x.getLsbD j = true)) := by
-  simp [← getLsbD_eq_getElem, getLsbD_neg, h]
-
 theorem getMsbD_neg {i : Nat} {x : BitVec w} :
     getMsbD (-x) i =
       (getMsbD x i ^^ decide (∃ j < w, i < j ∧ getMsbD x j = true)) := by

src/Init/Data/BitVec/Lemmas.lean

@@ -269,10 +269,6 @@ theorem ofBool_eq_iff_eq : ∀ {b b' : Bool}, BitVec.ofBool b = BitVec.ofBool b'
   getLsbD (x#'lt) i = x.testBit i := by
   simp [getLsbD, BitVec.ofNatLt]
 
-@[simp] theorem getMsbD_ofNatLt {n x i : Nat} (h : x < 2^n) :
-    getMsbD (x#'h) i = (decide (i < n) && x.testBit (n - 1 - i)) := by
-  simp [getMsbD, getLsbD]
-
 @[simp, bv_toNat] theorem toNat_ofNat (x w : Nat) : (BitVec.ofNat w x).toNat = x % 2^w := by
   simp [BitVec.toNat, BitVec.ofNat, Fin.ofNat']
 
@@ -565,10 +561,6 @@ theorem zeroExtend_eq_setWidth {v : Nat} {x : BitVec w} :
   else
     simp [n_le_i, toNat_ofNat]
 
-@[simp] theorem toInt_setWidth (x : BitVec w) :
-    (x.setWidth v).toInt = Int.bmod x.toNat (2^v) := by
-  simp [toInt_eq_toNat_bmod, toNat_setWidth, Int.emod_bmod]
-
 theorem setWidth'_eq {x : BitVec w} (h : w ≤ v) : x.setWidth' h = x.setWidth v := by
   apply eq_of_toNat_eq
   rw [toNat_setWidth, toNat_setWidth']
@@ -763,10 +755,6 @@ theorem extractLsb'_eq_extractLsb {w : Nat} (x : BitVec w) (start len : Nat) (h
 @[simp] theorem getLsbD_allOnes : (allOnes v).getLsbD i = decide (i < v) := by
   simp [allOnes]
 
-@[simp] theorem getMsbD_allOnes : (allOnes v).getMsbD i = decide (i < v) := by
-  simp [allOnes]
-  omega
-
 @[simp] theorem getElem_allOnes (i : Nat) (h : i < v) : (allOnes v)[i] = true := by
   simp [getElem_eq_testBit_toNat, h]
 
@@ -784,12 +772,6 @@ theorem extractLsb'_eq_extractLsb {w : Nat} (x : BitVec w) (start len : Nat) (h
 @[simp] theorem toNat_or (x y : BitVec v) :
     BitVec.toNat (x ||| y) = BitVec.toNat x ||| BitVec.toNat y := rfl
 
-@[simp] theorem toInt_or (x y : BitVec w) :
-    BitVec.toInt (x ||| y) = Int.bmod (BitVec.toNat x ||| BitVec.toNat y) (2^w) := by
-  rw_mod_cast [Int.bmod_def, BitVec.toInt, toNat_or, Nat.mod_eq_of_lt
-    (Nat.or_lt_two_pow (BitVec.isLt x) (BitVec.isLt y))]
-  omega
-
 @[simp] theorem toFin_or (x y : BitVec v) :
     BitVec.toFin (x ||| y) = BitVec.toFin x ||| BitVec.toFin y := by
   apply Fin.eq_of_val_eq
@@ -857,12 +839,6 @@ instance : Std.LawfulCommIdentity (α := BitVec n) (· ||| · ) (0#n) where
 @[simp] theorem toNat_and (x y : BitVec v) :
     BitVec.toNat (x &&& y) = BitVec.toNat x &&& BitVec.toNat y := rfl
 
-@[simp] theorem toInt_and (x y : BitVec w) :
-    BitVec.toInt (x &&& y) = Int.bmod (BitVec.toNat x &&& BitVec.toNat y) (2^w) := by
-  rw_mod_cast [Int.bmod_def, BitVec.toInt, toNat_and, Nat.mod_eq_of_lt
-    (Nat.and_lt_two_pow x.toNat (BitVec.isLt y))]
-  omega
-
 @[simp] theorem toFin_and (x y : BitVec v) :
     BitVec.toFin (x &&& y) = BitVec.toFin x &&& BitVec.toFin y := by
   apply Fin.eq_of_val_eq
@@ -930,12 +906,6 @@ instance : Std.LawfulCommIdentity (α := BitVec n) (· &&& · ) (allOnes n) wher
 @[simp] theorem toNat_xor (x y : BitVec v) :
     BitVec.toNat (x ^^^ y) = BitVec.toNat x ^^^ BitVec.toNat y := rfl
 
-@[simp] theorem toInt_xor (x y : BitVec w) :
-    BitVec.toInt (x ^^^ y) = Int.bmod (BitVec.toNat x ^^^ BitVec.toNat y) (2^w) := by
-  rw_mod_cast [Int.bmod_def, BitVec.toInt, toNat_xor, Nat.mod_eq_of_lt
-    (Nat.xor_lt_two_pow (BitVec.isLt x) (BitVec.isLt y))]
-  omega
-
 @[simp] theorem toFin_xor (x y : BitVec v) :
     BitVec.toFin (x ^^^ y) = BitVec.toFin x ^^^ BitVec.toFin y := by
   apply Fin.eq_of_val_eq
@@ -1013,13 +983,6 @@ theorem not_def {x : BitVec v} : ~~~x = allOnes v ^^^ x := rfl
           _ ≤ 2 ^ i := Nat.pow_le_pow_of_le_right Nat.zero_lt_two w
       · simp
 
-@[simp] theorem toInt_not {x : BitVec w} :
-    (~~~x).toInt = Int.bmod (2^w - 1 - x.toNat) (2^w) := by
-  rw_mod_cast [BitVec.toInt, BitVec.toNat_not, Int.bmod_def]
-  simp [show ((2^w : Nat) : Int) - 1 - x.toNat = ((2^w - 1 - x.toNat) : Nat) by omega]
-  rw_mod_cast [Nat.mod_eq_of_lt (by omega)]
-  omega
-
 @[simp] theorem ofInt_negSucc_eq_not_ofNat {w n : Nat} :
     BitVec.ofInt w (Int.negSucc n) = ~~~.ofNat w n := by
   simp only [BitVec.ofInt, Int.toNat, Int.ofNat_eq_coe, toNat_eq, toNat_ofNatLt, toNat_not,
@@ -1044,10 +1007,6 @@ theorem not_def {x : BitVec v} : ~~~x = allOnes v ^^^ x := rfl
 @[simp] theorem getLsbD_not {x : BitVec v} : (~~~x).getLsbD i = (decide (i < v) && ! x.getLsbD i) := by
   by_cases h' : i < v <;> simp_all [not_def]
 
-@[simp] theorem getMsbD_not {x : BitVec v} :
-    (~~~x).getMsbD i = (decide (i < v) && ! x.getMsbD i) := by
-  by_cases h' : i < v <;> simp_all [not_def]
-
 @[simp] theorem getElem_not {x : BitVec w} {i : Nat} (h : i < w) : (~~~x)[i] = !x[i] := by
   simp only [getElem_eq_testBit_toNat, toNat_not]
   rw [← Nat.sub_add_eq, Nat.add_comm 1]
@@ -1521,12 +1480,6 @@ theorem getLsbD_sshiftRight' {x y: BitVec w} {i : Nat} :
       (!decide (w ≤ i) && if y.toNat + i < w then x.getLsbD (y.toNat + i) else x.msb) := by
   simp only [BitVec.sshiftRight', BitVec.getLsbD_sshiftRight]
 
-@[simp]
-theorem getElem_sshiftRight' {x y : BitVec w} {i : Nat} (h : i < w) :
-    (x.sshiftRight' y)[i] =
-      (!decide (w ≤ i) && if y.toNat + i < w then x.getLsbD (y.toNat + i) else x.msb) := by
-  simp only [← getLsbD_eq_getElem, BitVec.sshiftRight', BitVec.getLsbD_sshiftRight]
-
 @[simp]
 theorem getMsbD_sshiftRight' {x y: BitVec w} {i : Nat} :
     (x.sshiftRight y.toNat).getMsbD i = (decide (i < w) && if i < y.toNat then x.msb else x.getMsbD (i - y.toNat)) := by
@@ -1619,79 +1572,6 @@ theorem signExtend_eq_setWidth_of_lt (x : BitVec w) {v : Nat} (hv : v ≤ w):
 theorem signExtend_eq (x : BitVec w) : x.signExtend w = x := by
   rw [signExtend_eq_setWidth_of_lt _ (Nat.le_refl _), setWidth_eq]
 
-/-- Sign extending to a larger bitwidth depends on the msb.
-If the msb is false, then the result equals the original value.
-If the msb is true, then we add a value of `(2^v - 2^w)`, which arises from the sign extension. -/
-theorem toNat_signExtend_of_le (x : BitVec w) {v : Nat} (hv : w ≤ v) :
-    (x.signExtend v).toNat = x.toNat + if x.msb then 2^v - 2^w else 0 := by
-  apply Nat.eq_of_testBit_eq
-  intro i
-  have ⟨k, hk⟩ := Nat.exists_eq_add_of_le hv
-  rw [hk, testBit_toNat, getLsbD_signExtend, Nat.pow_add, ← Nat.mul_sub_one, Nat.add_comm (x.toNat)]
-  by_cases hx : x.msb
-  · simp [hx, Nat.testBit_mul_pow_two_add _ x.isLt, testBit_toNat]
-    -- Case analysis on i being in the intervals [0..w), [w..w + k), [w+k..∞)
-    have hi : i < w ∨ (w ≤ i ∧ i < w + k) ∨ w + k ≤ i := by omega
-    rcases hi with hi | hi | hi
-    · simp [hi]; omega
-    · simp [hi]; omega
-    · simp [hi, show ¬ (i < w + k) by omega, show ¬ (i < w) by omega]
-      omega
-  · simp [hx, Nat.testBit_mul_pow_two_add _ x.isLt, testBit_toNat]
-    have hi : i < w ∨ (w ≤ i ∧ i < w + k) ∨ w + k ≤ i := by omega
-    rcases hi with hi | hi | hi
-    · simp [hi]; omega
-    · simp [hi]
-    · simp [hi, show ¬ (i < w + k) by omega, show ¬ (i < w) by omega, getLsbD_ge x i (by omega)]
-
-/-- Sign extending to a larger bitwidth depends on the msb.
-If the msb is false, then the result equals the original value.
-If the msb is true, then we add a value of `(2^v - 2^w)`, which arises from the sign extension. -/
-theorem toNat_signExtend (x : BitVec w) {v : Nat} :
-    (x.signExtend v).toNat = (x.setWidth v).toNat + if x.msb then 2^v - 2^w else 0 := by
-  by_cases h : v ≤ w
-  · have : 2^v ≤ 2^w := Nat.pow_le_pow_of_le_right Nat.two_pos h
-    simp [signExtend_eq_setWidth_of_lt x h, toNat_setWidth, Nat.sub_eq_zero_of_le this]
-  · have : 2^w ≤ 2^v := Nat.pow_le_pow_of_le_right Nat.two_pos (by omega)
-    rw [toNat_signExtend_of_le x (by omega), toNat_setWidth, Nat.mod_eq_of_lt (by omega)]
-
-/-
-If the current width `w` is smaller than the extended width `v`,
-then the value when interpreted as an integer does not change.
--/
-theorem toInt_signExtend_of_lt {x : BitVec w} (hv : w < v):
-    (x.signExtend v).toInt = x.toInt := by
-  simp only [toInt_eq_msb_cond, toNat_signExtend]
-  have : (x.signExtend v).msb = x.msb := by
-    rw [msb_eq_getLsbD_last, getLsbD_eq_getElem (Nat.sub_one_lt_of_lt hv)]
-    simp [getElem_signExtend, Nat.le_sub_one_of_lt hv]
-  have H : 2^w ≤ 2^v := Nat.pow_le_pow_of_le_right (by omega) (by omega)
-  simp only [this, toNat_setWidth, Int.natCast_add, Int.ofNat_emod, Int.natCast_mul]
-  by_cases h : x.msb
-  <;> norm_cast
-  <;> simp [h, Nat.mod_eq_of_lt (Nat.lt_of_lt_of_le x.isLt H)]
-  omega
-
-/-
-If the current width `w` is larger than the extended width `v`,
-then the value when interpreted as an integer is truncated,
-and we compute a modulo by `2^v`.
--/
-theorem toInt_signExtend_of_le {x : BitVec w} (hv : v ≤ w) :
-    (x.signExtend v).toInt = Int.bmod x.toNat (2^v) := by
-  simp [signExtend_eq_setWidth_of_lt _ hv]
-
-/-
-Interpreting the sign extension of `(x : BitVec w)` to width `v`
-computes `x % 2^v` (where `%` is the balanced mod).
--/
-theorem toInt_signExtend (x : BitVec w) :
-    (x.signExtend v).toInt = Int.bmod x.toNat (2^(min v w)) := by
-  by_cases hv : v ≤ w
-  · simp [toInt_signExtend_of_le hv, Nat.min_eq_left hv]
-  · simp only [Nat.not_le] at hv
-    rw [toInt_signExtend_of_lt hv, Nat.min_eq_right (by omega), toInt_eq_toNat_bmod]
-
 /-! ### append -/
 
 theorem append_def (x : BitVec v) (y : BitVec w) :
@@ -3344,11 +3224,7 @@ theorem toNat_abs {x : BitVec w} : x.abs.toNat = if x.msb then 2^w - x.toNat els
   · simp [h]
 
 theorem getLsbD_abs {i : Nat} {x : BitVec w} :
-    getLsbD x.abs i = if x.msb then getLsbD (-x) i else getLsbD x i := by
-  by_cases h : x.msb <;> simp [BitVec.abs, h]
-
-theorem getElem_abs {i : Nat} {x : BitVec w} (h : i < w) :
-    x.abs[i] = if x.msb then (-x)[i] else x[i] := by
+   getLsbD x.abs i = if x.msb then getLsbD (-x) i else getLsbD x i := by
   by_cases h : x.msb <;> simp [BitVec.abs, h]
 
 theorem getMsbD_abs {i : Nat} {x : BitVec w} :

src/Init/Data/ByteArray/Basic.lean

@@ -108,18 +108,8 @@ def toList (bs : ByteArray) : List UInt8 :=
 
 @[inline] def findIdx? (a : ByteArray) (p : UInt8 → Bool) (start := 0) : Option Nat :=
   let rec @[specialize] loop (i : Nat) :=
-    if h : i < a.size then
-      if p a[i] then some i else loop (i+1)
-    else
-      none
-    termination_by a.size - i
-    decreasing_by decreasing_trivial_pre_omega
-  loop start
-
-@[inline] def findFinIdx? (a : ByteArray) (p : UInt8 → Bool) (start := 0) : Option (Fin a.size) :=
-  let rec @[specialize] loop (i : Nat) :=
-    if h : i < a.size then
-      if p a[i] then some ⟨i, h⟩ else loop (i+1)
+    if i < a.size then
+      if p (a.get! i) then some i else loop (i+1)
     else
       none
     termination_by a.size - i

src/Init/Data/Fin/Fold.lean

@@ -13,17 +13,17 @@ namespace Fin
 /-- Folds over `Fin n` from the left: `foldl 3 f x = f (f (f x 0) 1) 2`. -/
 @[inline] def foldl (n) (f : α → Fin n → α) (init : α) : α := loop init 0 where
   /-- Inner loop for `Fin.foldl`. `Fin.foldl.loop n f x i = f (f (f x i) ...) (n-1)`  -/
-  @[semireducible] loop (x : α) (i : Nat) : α :=
+  loop (x : α) (i : Nat) : α :=
     if h : i < n then loop (f x ⟨i, h⟩) (i+1) else x
   termination_by n - i
+  decreasing_by decreasing_trivial_pre_omega
 
 /-- Folds over `Fin n` from the right: `foldr 3 f x = f 0 (f 1 (f 2 x))`. -/
-@[inline] def foldr (n) (f : Fin n → α → α) (init : α) : α := loop n (Nat.le_refl n) init where
+@[inline] def foldr (n) (f : Fin n → α → α) (init : α) : α := loop ⟨n, Nat.le_refl n⟩ init where
   /-- Inner loop for `Fin.foldr`. `Fin.foldr.loop n f i x = f 0 (f ... (f (i-1) x))`  -/
-  loop : (i : _) → i ≤ n → α → α
-  | 0, _, x => x
-  | i+1, h, x => loop i (Nat.le_of_lt h) (f ⟨i, h⟩ x)
-  termination_by structural i => i
+  loop : {i // i ≤ n} → α → α
+  | ⟨0, _⟩, x => x
+  | ⟨i+1, h⟩, x => loop ⟨i, Nat.le_of_lt h⟩ (f ⟨i, h⟩ x)
 
 /--
 Folds a monadic function over `Fin n` from left to right:
@@ -176,19 +176,17 @@ theorem foldl_eq_foldlM (f : α → Fin n → α) (x) :
 /-! ### foldr -/
 
 theorem foldr_loop_zero (f : Fin n → α → α) (x) :
-    foldr.loop n f 0 (Nat.zero_le _) x = x := by
+    foldr.loop n f ⟨0, Nat.zero_le _⟩ x = x := by
   rw [foldr.loop]
 
 theorem foldr_loop_succ (f : Fin n → α → α) (x) (h : i < n) :
-    foldr.loop n f (i+1) h x = foldr.loop n f i (Nat.le_of_lt h) (f ⟨i, h⟩ x) := by
+    foldr.loop n f ⟨i+1, h⟩ x = foldr.loop n f ⟨i, Nat.le_of_lt h⟩ (f ⟨i, h⟩ x) := by
   rw [foldr.loop]
 
 theorem foldr_loop (f : Fin (n+1) → α → α) (x) (h : i+1 ≤ n+1) :
-    foldr.loop (n+1) f (i+1) h x =
-      f 0 (foldr.loop n (fun j => f j.succ) i (Nat.le_of_succ_le_succ h) x) := by
-  induction i generalizing x with
-  | zero => simp [foldr_loop_succ, foldr_loop_zero]
-  | succ i ih => rw [foldr_loop_succ, ih]; rfl
+    foldr.loop (n+1) f ⟨i+1, h⟩ x =
+      f 0 (foldr.loop n (fun j => f j.succ) ⟨i, Nat.le_of_succ_le_succ h⟩ x) := by
+  induction i generalizing x <;> simp [foldr_loop_zero, foldr_loop_succ, *]
 
 @[simp] theorem foldr_zero (f : Fin 0 → α → α) (x) : foldr 0 f x = x :=
   foldr_loop_zero ..

src/Init/Data/List/Basic.lean

@@ -231,7 +231,7 @@ theorem ext_get? : ∀ {l₁ l₂ : List α}, (∀ n, l₁.get? n = l₂.get? n)
     injection h0 with aa; simp only [aa, ext_get? fun n => h (n+1)]
 
 /-- Deprecated alias for `ext_get?`. The preferred extensionality theorem is now `ext_getElem?`. -/
-@[deprecated ext_get? (since := "2024-06-07")] abbrev ext := @ext_get?
+@[deprecated (since := "2024-06-07")] abbrev ext := @ext_get?
 
 /-! ### getD -/
 
@@ -682,7 +682,7 @@ theorem elem_cons [BEq α] {a : α} :
     (b::bs).elem a = match a == b with | true => true | false => bs.elem a := rfl
 
 /-- `notElem a l` is `!(elem a l)`. -/
-@[deprecated "Use `!(elem a l)` instead."(since := "2024-06-15")]
+@[deprecated (since := "2024-06-15")]
 def notElem [BEq α] (a : α) (as : List α) : Bool :=
   !(as.elem a)
 
@@ -1427,10 +1427,10 @@ def zipWithAll (f : Option α → Option β → γ) : List α → List β → Li
   | a :: as, [] => (a :: as).map fun a => f (some a) none
   | a :: as, b :: bs => f a b :: zipWithAll f as bs
 
-@[simp] theorem zipWithAll_nil :
+@[simp] theorem zipWithAll_nil_right :
     zipWithAll f as [] = as.map fun a => f (some a) none := by
   cases as <;> rfl
-@[simp] theorem nil_zipWithAll :
+@[simp] theorem zipWithAll_nil_left :
     zipWithAll f [] bs = bs.map fun b => f none (some b) := rfl
 @[simp] theorem zipWithAll_cons_cons :
     zipWithAll f (a :: as) (b :: bs) = f (some a) (some b) :: zipWithAll f as bs := rfl

src/Init/Data/List/Lemmas.lean

@@ -101,7 +101,7 @@ theorem tail_eq_of_cons_eq (H : h₁ :: t₁ = h₂ :: t₂) : t₁ = t₂ := (c
 theorem cons_inj_right (a : α) {l l' : List α} : a :: l = a :: l' ↔ l = l' :=
   ⟨tail_eq_of_cons_eq, congrArg _⟩
 
-@[deprecated cons_inj_right (since := "2024-06-15")] abbrev cons_inj := @cons_inj_right
+@[deprecated (since := "2024-06-15")] abbrev cons_inj := @cons_inj_right
 
 theorem cons_eq_cons {a b : α} {l l' : List α} : a :: l = b :: l' ↔ a = b ∧ l = l' :=
   List.cons.injEq .. ▸ .rfl
@@ -171,7 +171,7 @@ theorem get_cons_succ {as : List α} {h : i + 1 < (a :: as).length} :
 theorem get_cons_succ' {as : List α} {i : Fin as.length} :
   (a :: as).get i.succ = as.get i := rfl
 
-@[deprecated "Deprecated without replacement." (since := "2024-07-09")]
+@[deprecated (since := "2024-07-09")]
 theorem get_cons_cons_one : (a₁ :: a₂ :: as).get (1 : Fin (as.length + 2)) = a₂ := rfl
 
 theorem get_mk_zero : ∀ {l : List α} (h : 0 < l.length), l.get ⟨0, h⟩ = l.head (length_pos.mp h)
@@ -791,24 +791,6 @@ theorem mem_or_eq_of_mem_set : ∀ {l : List α} {n : Nat} {a b : α}, a ∈ l.s
     · intro a
       simp
 
-@[simp] theorem beq_nil_iff [BEq α] {l : List α} : (l == []) = l.isEmpty := by
-  cases l <;> rfl
-
-@[simp] theorem nil_beq_iff [BEq α] {l : List α} : ([] == l) = l.isEmpty := by
-  cases l <;> rfl
-
-@[simp] theorem cons_beq_cons [BEq α] {a b : α} {l₁ l₂ : List α} :
-    (a :: l₁ == b :: l₂) = (a == b && l₁ == l₂) := rfl
-
-theorem length_eq_of_beq [BEq α] {l₁ l₂ : List α} (h : l₁ == l₂) : l₁.length = l₂.length :=
-  match l₁, l₂ with
-  | [], [] => rfl
-  | [], _ :: _ => by simp [beq_nil_iff] at h
-  | _ :: _, [] => by simp [nil_beq_iff] at h
-  | a :: l₁, b :: l₂ => by
-    simp at h
-    simpa [Nat.add_one_inj]using length_eq_of_beq h.2
-
 /-! ### Lexicographic ordering -/
 
 protected theorem lt_irrefl [LT α] (lt_irrefl : ∀ x : α, ¬x < x) (l : List α) : ¬l < l := by
@@ -874,12 +856,6 @@ theorem foldr_eq_foldrM (f : α → β → β) (b) (l : List α) :
     l.foldr f b = l.foldrM (m := Id) f b := by
   induction l <;> simp [*, foldr]
 
-@[simp] theorem id_run_foldlM (f : β → α → Id β) (b) (l : List α) :
-    Id.run (l.foldlM f b) = l.foldl f b := (foldl_eq_foldlM f b l).symm
-
-@[simp] theorem id_run_foldrM (f : α → β → Id β) (b) (l : List α) :
-    Id.run (l.foldrM f b) = l.foldr f b := (foldr_eq_foldrM f b l).symm
-
 /-! ### foldl and foldr -/
 
 @[simp] theorem foldr_cons_eq_append (l : List α) : l.foldr cons l' = l ++ l' := by
@@ -1824,7 +1800,7 @@ theorem getElem_append_right' (l₁ : List α) {l₂ : List α} {n : Nat} (hn :
     l₂[n] = (l₁ ++ l₂)[n + l₁.length]'(by simpa [Nat.add_comm] using Nat.add_lt_add_left hn _) := by
   rw [getElem_append_right] <;> simp [*, le_add_left]
 
-@[deprecated "Deprecated without replacement." (since := "2024-06-12")]
+@[deprecated (since := "2024-06-12")]
 theorem get_append_right_aux {l₁ l₂ : List α} {n : Nat}
   (h₁ : l₁.length ≤ n) (h₂ : n < (l₁ ++ l₂).length) : n - l₁.length < l₂.length := by
   rw [length_append] at h₂
@@ -1841,7 +1817,7 @@ theorem getElem_of_append {l : List α} (eq : l = l₁ ++ a :: l₂) (h : l₁.l
   rw [← getElem?_eq_getElem, eq, getElem?_append_right (h ▸ Nat.le_refl _), h]
   simp
 
-@[deprecated "Deprecated without replacement." (since := "2024-06-12")]
+@[deprecated (since := "2024-06-12")]
 theorem get_of_append_proof {l : List α}
     (eq : l = l₁ ++ a :: l₂) (h : l₁.length = n) : n < length l := eq ▸ h ▸ by simp_arith
 

src/Init/Data/List/Nat/BEq.lean

@@ -9,7 +9,7 @@ import Init.Data.List.Basic
 
 namespace List
 
-/-! ### isEqv -/
+/-! ### isEqv-/
 
 theorem isEqv_eq_decide (a b : List α) (r) :
     isEqv a b r = if h : a.length = b.length then

src/Init/Data/List/Sort/Lemmas.lean

@@ -293,7 +293,7 @@ theorem sorted_mergeSort
     apply sorted_mergeSort trans total
 termination_by l => l.length
 
-@[deprecated sorted_mergeSort (since := "2024-09-02")] abbrev mergeSort_sorted := @sorted_mergeSort
+@[deprecated (since := "2024-09-02")] abbrev mergeSort_sorted := @sorted_mergeSort
 
 /--
 If the input list is already sorted, then `mergeSort` does not change the list.
@@ -429,8 +429,7 @@ theorem sublist_mergeSort
         ((fun w => Sublist.of_sublist_append_right w h') fun b m₁ m₃ =>
           (Bool.eq_not_self true).mp ((rel_of_pairwise_cons hc m₁).symm.trans (h₃ b m₃))))
 
-@[deprecated sublist_mergeSort (since := "2024-09-02")]
-abbrev mergeSort_stable := @sublist_mergeSort
+@[deprecated (since := "2024-09-02")] abbrev mergeSort_stable := @sublist_mergeSort
 
 /--
 Another statement of stability of merge sort.
@@ -443,8 +442,7 @@ theorem pair_sublist_mergeSort
     (hab : le a b) (h : [a, b] <+ l) : [a, b] <+ mergeSort l le :=
   sublist_mergeSort trans total (pairwise_pair.mpr hab) h
 
-@[deprecated pair_sublist_mergeSort(since := "2024-09-02")]
-abbrev mergeSort_stable_pair := @pair_sublist_mergeSort
+@[deprecated (since := "2024-09-02")] abbrev mergeSort_stable_pair := @pair_sublist_mergeSort
 
 theorem map_merge {f : α → β} {r : α → α → Bool} {s : β → β → Bool} {l l' : List α}
     (hl : ∀ a ∈ l, ∀ b ∈ l', r a b = s (f a) (f b)) :

src/Init/Data/List/Sublist.lean

@@ -835,7 +835,7 @@ theorem isPrefix_iff : l₁ <+: l₂ ↔ ∀ i (h : i < l₁.length), l₂[i]? =
       simpa using ⟨0, by simp⟩
     | cons b l₂ =>
       simp only [cons_append, cons_prefix_cons, ih]
-      rw (occs := [2]) [← Nat.and_forall_add_one]
+      rw (occs := .pos [2]) [← Nat.and_forall_add_one]
       simp [Nat.succ_lt_succ_iff, eq_comm]
 
 theorem isPrefix_iff_getElem {l₁ l₂ : List α} :

src/Init/Data/List/TakeDrop.lean

@@ -224,7 +224,7 @@ theorem take_succ {l : List α} {n : Nat} : l.take (n + 1) = l.take n ++ l[n]?.t
     · simp only [take, Option.toList, getElem?_cons_zero, nil_append]
     · simp only [take, hl, getElem?_cons_succ, cons_append]
 
-@[deprecated "Deprecated without replacement." (since := "2024-07-25")]
+@[deprecated (since := "2024-07-25")]
 theorem drop_sizeOf_le [SizeOf α] (l : List α) (n : Nat) : sizeOf (l.drop n) ≤ sizeOf l := by
   induction l generalizing n with
   | nil => rw [drop_nil]; apply Nat.le_refl

src/Init/Data/Nat.lean

@@ -20,4 +20,3 @@ import Init.Data.Nat.Mod
 import Init.Data.Nat.Lcm
 import Init.Data.Nat.Compare
 import Init.Data.Nat.Simproc
-import Init.Data.Nat.Fold

src/Init/Data/Nat/Basic.lean

@@ -35,6 +35,52 @@ Used as the default `Nat` eliminator by the `cases` tactic. -/
 protected abbrev casesAuxOn {motive : Nat → Sort u} (t : Nat) (zero : motive 0) (succ : (n : Nat) → motive (n + 1)) : motive t :=
   Nat.casesOn t zero succ
 
+/--
+`Nat.fold` evaluates `f` on the numbers up to `n` exclusive, in increasing order:
+* `Nat.fold f 3 init = init |> f 0 |> f 1 |> f 2`
+-/
+@[specialize] def fold {α : Type u} (f : Nat → α → α) : (n : Nat) → (init : α) → α
+  | 0,      a => a
+  | succ n, a => f n (fold f n a)
+
+/-- Tail-recursive version of `Nat.fold`. -/
+@[inline] def foldTR {α : Type u} (f : Nat → α → α) (n : Nat) (init : α) : α :=
+  let rec @[specialize] loop
+    | 0,      a => a
+    | succ m, a => loop m (f (n - succ m) a)
+  loop n init
+
+/--
+`Nat.foldRev` evaluates `f` on the numbers up to `n` exclusive, in decreasing order:
+* `Nat.foldRev f 3 init = f 0 <| f 1 <| f 2 <| init`
+-/
+@[specialize] def foldRev {α : Type u} (f : Nat → α → α) : (n : Nat) → (init : α) → α
+  | 0,      a => a
+  | succ n, a => foldRev f n (f n a)
+
+/-- `any f n = true` iff there is `i in [0, n-1]` s.t. `f i = true` -/
+@[specialize] def any (f : Nat → Bool) : Nat → Bool
+  | 0      => false
+  | succ n => any f n || f n
+
+/-- Tail-recursive version of `Nat.any`. -/
+@[inline] def anyTR (f : Nat → Bool) (n : Nat) : Bool :=
+  let rec @[specialize] loop : Nat → Bool
+    | 0      => false
+    | succ m => f (n - succ m) || loop m
+  loop n
+
+/-- `all f n = true` iff every `i in [0, n-1]` satisfies `f i = true` -/
+@[specialize] def all (f : Nat → Bool) : Nat → Bool
+  | 0      => true
+  | succ n => all f n && f n
+
+/-- Tail-recursive version of `Nat.all`. -/
+@[inline] def allTR (f : Nat → Bool) (n : Nat) : Bool :=
+  let rec @[specialize] loop : Nat → Bool
+    | 0      => true
+    | succ m => f (n - succ m) && loop m
+  loop n
 
 /--
 `Nat.repeat f n a` is `f^(n) a`; that is, it iterates `f` `n` times on `a`.
@@ -789,7 +835,7 @@ theorem pred_lt_of_lt {n m : Nat} (h : m < n) : pred n < n :=
   pred_lt (not_eq_zero_of_lt h)
 
 set_option linter.missingDocs false in
-@[deprecated pred_lt_of_lt (since := "2024-06-01")] abbrev pred_lt' := @pred_lt_of_lt
+@[deprecated (since := "2024-06-01")] abbrev pred_lt' := @pred_lt_of_lt
 
 theorem sub_one_lt_of_lt {n m : Nat} (h : m < n) : n - 1 < n :=
   sub_one_lt (not_eq_zero_of_lt h)
@@ -1075,7 +1121,7 @@ theorem pred_mul (n m : Nat) : pred n * m = n * m - m := by
   | succ n => rw [Nat.pred_succ, succ_mul, Nat.add_sub_cancel]
 
 set_option linter.missingDocs false in
-@[deprecated pred_mul (since := "2024-06-01")] abbrev mul_pred_left := @pred_mul
+@[deprecated (since := "2024-06-01")] abbrev mul_pred_left := @pred_mul
 
 protected theorem sub_one_mul  (n m : Nat) : (n - 1) * m = n * m - m := by
   cases n with
@@ -1087,7 +1133,7 @@ theorem mul_pred (n m : Nat) : n * pred m = n * m - n := by
   rw [Nat.mul_comm, pred_mul, Nat.mul_comm]
 
 set_option linter.missingDocs false in
-@[deprecated mul_pred (since := "2024-06-01")] abbrev mul_pred_right := @mul_pred
+@[deprecated (since := "2024-06-01")] abbrev mul_pred_right := @mul_pred
 
 theorem mul_sub_one (n m : Nat) : n * (m - 1) = n * m - n := by
   rw [Nat.mul_comm, Nat.sub_one_mul , Nat.mul_comm]
@@ -1112,6 +1158,33 @@ theorem not_lt_eq (a b : Nat) : (¬ (a < b)) = (b ≤ a) :=
 theorem not_gt_eq (a b : Nat) : (¬ (a > b)) = (a ≤ b) :=
   not_lt_eq b a
 
+/-! # csimp theorems -/
+
+@[csimp] theorem fold_eq_foldTR : @fold = @foldTR :=
+  funext fun α => funext fun f => funext fun n => funext fun init =>
+  let rec go : ∀ m n, foldTR.loop f (m + n) m (fold f n init) = fold f (m + n) init
+    | 0,      n => by simp [foldTR.loop]
+    | succ m, n => by rw [foldTR.loop, add_sub_self_left, succ_add]; exact go m (succ n)
+  (go n 0).symm
+
+@[csimp] theorem any_eq_anyTR : @any = @anyTR :=
+  funext fun f => funext fun n =>
+  let rec go : ∀ m n,  (any f n || anyTR.loop f (m + n) m) = any f (m + n)
+    | 0,      n => by simp [anyTR.loop]
+    | succ m, n => by
+      rw [anyTR.loop, add_sub_self_left, ← Bool.or_assoc, succ_add]
+      exact go m (succ n)
+  (go n 0).symm
+
+@[csimp] theorem all_eq_allTR : @all = @allTR :=
+  funext fun f => funext fun n =>
+  let rec go : ∀ m n,  (all f n && allTR.loop f (m + n) m) = all f (m + n)
+    | 0,      n => by simp [allTR.loop]
+    | succ m, n => by
+      rw [allTR.loop, add_sub_self_left, ← Bool.and_assoc, succ_add]
+      exact go m (succ n)
+  (go n 0).symm
+
 @[csimp] theorem repeat_eq_repeatTR : @repeat = @repeatTR :=
   funext fun α => funext fun f => funext fun n => funext fun init =>
   let rec go : ∀ m n, repeatTR.loop f m (repeat f n init) = repeat f (m + n) init
@@ -1120,3 +1193,31 @@ theorem not_gt_eq (a b : Nat) : (¬ (a > b)) = (a ≤ b) :=
   (go n 0).symm
 
 end Nat
+
+namespace Prod
+
+/--
+`(start, stop).foldI f a` evaluates `f` on all the numbers
+from `start` (inclusive) to `stop` (exclusive) in increasing order:
+* `(5, 8).foldI f init = init |> f 5 |> f 6 |> f 7`
+-/
+@[inline] def foldI {α : Type u} (f : Nat → α → α) (i : Nat × Nat) (a : α) : α :=
+  Nat.foldTR.loop f i.2 (i.2 - i.1) a
+
+/--
+`(start, stop).anyI f a` returns true if `f` is true for some natural number
+from `start` (inclusive) to `stop` (exclusive):
+* `(5, 8).anyI f = f 5 || f 6 || f 7`
+-/
+@[inline] def anyI (f : Nat → Bool) (i : Nat × Nat) : Bool :=
+  Nat.anyTR.loop f i.2 (i.2 - i.1)
+
+/--
+`(start, stop).allI f a` returns true if `f` is true for all natural numbers
+from `start` (inclusive) to `stop` (exclusive):
+* `(5, 8).anyI f = f 5 && f 6 && f 7`
+-/
+@[inline] def allI (f : Nat → Bool) (i : Nat × Nat) : Bool :=
+  Nat.allTR.loop f i.2 (i.2 - i.1)
+
+end Prod

src/Init/Data/Nat/Control.lean

@@ -6,51 +6,50 @@ Author: Leonardo de Moura
 prelude
 import Init.Control.Basic
 import Init.Data.Nat.Basic
-import Init.Omega
 
 namespace Nat
 universe u v
 
-@[inline] def forM {m} [Monad m] (n : Nat) (f : (i : Nat) → i < n → m Unit) : m Unit :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → m Unit
-    | 0,   _ => pure ()
-    | i+1, h => do f (n-i-1) (by omega); loop i (Nat.le_of_succ_le h)
-  loop n (by simp)
+@[inline] def forM {m} [Monad m] (n : Nat) (f : Nat → m Unit) : m Unit :=
+  let rec @[specialize] loop
+    | 0   => pure ()
+    | i+1 => do f (n-i-1); loop i
+  loop n
 
-@[inline] def forRevM {m} [Monad m] (n : Nat) (f : (i : Nat) → i < n → m Unit) : m Unit :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → m Unit
-    | 0,   _ => pure ()
-    | i+1, h => do f i (by omega); loop i (Nat.le_of_succ_le h)
-  loop n (by simp)
+@[inline] def forRevM {m} [Monad m] (n : Nat) (f : Nat → m Unit) : m Unit :=
+  let rec @[specialize] loop
+    | 0   => pure ()
+    | i+1 => do f i; loop i
+  loop n
 
-@[inline] def foldM {α : Type u} {m : Type u → Type v} [Monad m] (n : Nat) (f : (i : Nat) → i < n → α → m α) (init : α) : m α :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → α → m α
-    | 0,   h, a => pure a
-    | i+1, h, a => f (n-i-1) (by omega) a >>= loop i (Nat.le_of_succ_le h)
-  loop n (by omega) init
+@[inline] def foldM {α : Type u} {m : Type u → Type v} [Monad m] (f : Nat → α → m α) (init : α) (n : Nat) : m α :=
+  let rec @[specialize] loop
+    | 0,   a => pure a
+    | i+1, a => f (n-i-1) a >>= loop i
+  loop n init
 
-@[inline] def foldRevM {α : Type u} {m : Type u → Type v} [Monad m] (n : Nat) (f : (i : Nat) → i < n → α → m α) (init : α) : m α :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → α → m α
-    | 0,   h, a => pure a
-    | i+1, h, a => f i (by omega) a >>= loop i (Nat.le_of_succ_le h)
-  loop n (by omega) init
+@[inline] def foldRevM {α : Type u} {m : Type u → Type v} [Monad m] (f : Nat → α → m α) (init : α) (n : Nat) : m α :=
+  let rec @[specialize] loop
+    | 0,   a => pure a
+    | i+1, a => f i a >>= loop i
+  loop n init
 
-@[inline] def allM {m} [Monad m] (n : Nat) (p : (i : Nat) → i < n → m Bool) : m Bool :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → m Bool
-    | 0,   _ => pure true
-    | i+1 , h => do
-      match (← p (n-i-1) (by omega)) with
-      | true  => loop i (by omega)
+@[inline] def allM {m} [Monad m] (n : Nat) (p : Nat → m Bool) : m Bool :=
+  let rec @[specialize] loop
+    | 0   => pure true
+    | i+1 => do
+      match (← p (n-i-1)) with
+      | true  => loop i
       | false => pure false
-  loop n (by simp)
+  loop n
 
-@[inline] def anyM {m} [Monad m] (n : Nat) (p : (i : Nat) → i < n → m Bool) : m Bool :=
-  let rec @[specialize] loop : ∀ i, i ≤ n → m Bool
-    | 0,   _ => pure false
-    | i+1, h => do
-      match (← p (n-i-1) (by omega)) with
+@[inline] def anyM {m} [Monad m] (n : Nat) (p : Nat → m Bool) : m Bool :=
+  let rec @[specialize] loop
+    | 0   => pure false
+    | i+1 => do
+      match (← p (n-i-1)) with
       | true  => pure true
-      | false => loop i (Nat.le_of_succ_le h)
-  loop n (by simp)
+      | false => loop i
+  loop n
 
 end Nat

src/Init/Data/Nat/Dvd.lean

@@ -92,7 +92,7 @@ protected theorem div_mul_cancel {n m : Nat} (H : n ∣ m) : m / n * n = m := by
   rw [Nat.mul_comm, Nat.mul_div_cancel' H]
 
 @[simp] theorem mod_mod_of_dvd (a : Nat) (h : c ∣ b) : a % b % c = a % c := by
-  rw (occs := [2]) [← mod_add_div a b]
+  rw (occs := .pos [2]) [← mod_add_div a b]
   have ⟨x, h⟩ := h
   subst h
   rw [Nat.mul_assoc, add_mul_mod_self_left]

src/Init/Data/Nat/Fold.lean

@@ -1,168 +0,0 @@
-/-
-Copyright (c) 2014 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Floris van Doorn, Leonardo de Moura, Kim Morrison
--/
-prelude
-import Init.Omega
-
-set_option linter.missingDocs true -- keep it documented
-universe u
-
-namespace Nat
-
-/--
-`Nat.fold` evaluates `f` on the numbers up to `n` exclusive, in increasing order:
-* `Nat.fold f 3 init = init |> f 0 |> f 1 |> f 2`
--/
-@[specialize] def fold {α : Type u} : (n : Nat) → (f : (i : Nat) → i < n → α → α) → (init : α) → α
-  | 0,      f, a => a
-  | succ n, f, a => f n (by omega) (fold n (fun i h => f i (by omega)) a)
-
-/-- Tail-recursive version of `Nat.fold`. -/
-@[inline] def foldTR {α : Type u} (n : Nat) (f : (i : Nat) → i < n → α → α) (init : α) : α :=
-  let rec @[specialize] loop : ∀ j, j ≤ n → α → α
-    | 0,      h, a => a
-    | succ m, h, a => loop m (by omega) (f (n - succ m) (by omega) a)
-  loop n (by omega) init
-
-/--
-`Nat.foldRev` evaluates `f` on the numbers up to `n` exclusive, in decreasing order:
-* `Nat.foldRev f 3 init = f 0 <| f 1 <| f 2 <| init`
--/
-@[specialize] def foldRev {α : Type u} : (n : Nat) → (f : (i : Nat) → i < n → α → α) → (init : α) → α
-  | 0,      f, a => a
-  | succ n, f, a => foldRev n (fun i h => f i (by omega)) (f n (by omega) a)
-
-/-- `any f n = true` iff there is `i in [0, n-1]` s.t. `f i = true` -/
-@[specialize] def any : (n : Nat) → (f : (i : Nat) → i < n → Bool) → Bool
-  | 0,      f => false
-  | succ n, f => any n (fun i h => f i (by omega)) || f n (by omega)
-
-/-- Tail-recursive version of `Nat.any`. -/
-@[inline] def anyTR (n : Nat) (f : (i : Nat) → i < n → Bool) : Bool :=
-  let rec @[specialize] loop : (i : Nat) → i ≤ n → Bool
-    | 0,      h => false
-    | succ m, h => f (n - succ m) (by omega) || loop m (by omega)
-  loop n (by omega)
-
-/-- `all f n = true` iff every `i in [0, n-1]` satisfies `f i = true` -/
-@[specialize] def all : (n : Nat) → (f : (i : Nat) → i < n → Bool) → Bool
-  | 0,      f => true
-  | succ n, f => all n (fun i h => f i (by omega)) && f n (by omega)
-
-/-- Tail-recursive version of `Nat.all`. -/
-@[inline] def allTR (n : Nat) (f : (i : Nat) → i < n → Bool) : Bool :=
-  let rec @[specialize] loop : (i : Nat) → i ≤ n   → Bool
-    | 0,      h => true
-    | succ m, h => f (n - succ m) (by omega) && loop m (by omega)
-  loop n (by omega)
-
-/-! # csimp theorems -/
-
-theorem fold_congr {α : Type u} {n m : Nat} (w : n = m)
-     (f : (i : Nat) → i < n → α → α) (init : α) :
-     fold n f init = fold m (fun i h => f i (by omega)) init := by
-  subst m
-  rfl
-
-theorem foldTR_loop_congr {α : Type u} {n m : Nat} (w : n = m)
-     (f : (i : Nat) → i < n → α → α) (j : Nat) (h : j ≤ n) (init : α) :
-     foldTR.loop n f j h init = foldTR.loop m (fun i h => f i (by omega)) j (by omega) init := by
-  subst m
-  rfl
-
-@[csimp] theorem fold_eq_foldTR : @fold = @foldTR :=
-  funext fun α => funext fun n => funext fun f => funext fun init =>
-  let rec go : ∀ m n f, fold (m + n) f init = foldTR.loop (m + n) f m (by omega) (fold n (fun i h => f i (by omega)) init)
-    | 0,      n, f => by
-      simp only [foldTR.loop]
-      have t : 0 + n = n := by omega
-      rw [fold_congr t]
-    | succ m, n, f => by
-      have t : (m + 1) + n = m + (n + 1) := by omega
-      rw [foldTR.loop]
-      simp only [succ_eq_add_one, Nat.add_sub_cancel]
-      rw [fold_congr t, foldTR_loop_congr t, go, fold]
-      congr
-      omega
-  go n 0 f
-
-theorem any_congr {n m : Nat} (w : n = m) (f : (i : Nat) → i < n → Bool) : any n f = any m (fun i h => f i (by omega)) := by
-  subst m
-  rfl
-
-theorem anyTR_loop_congr {n m : Nat} (w : n = m) (f : (i : Nat) → i < n → Bool) (j : Nat) (h : j ≤ n) :
-    anyTR.loop n f j h = anyTR.loop m (fun i h => f i (by omega)) j (by omega) := by
-  subst m
-  rfl
-
-@[csimp] theorem any_eq_anyTR : @any = @anyTR :=
-  funext fun n => funext fun f =>
-  let rec go : ∀ m n f, any (m + n) f = (any n (fun i h => f i (by omega)) || anyTR.loop (m + n) f m (by omega))
-    | 0,      n, f => by
-      simp [anyTR.loop]
-      have t : 0 + n = n := by omega
-      rw [any_congr t]
-    | succ m, n, f => by
-      have t : (m + 1) + n = m + (n + 1) := by omega
-      rw [anyTR.loop]
-      simp only [succ_eq_add_one]
-      rw [any_congr t, anyTR_loop_congr t, go, any, Bool.or_assoc]
-      congr
-      omega
-  go n 0 f
-
-theorem all_congr {n m : Nat} (w : n = m) (f : (i : Nat) → i < n → Bool) : all n f = all m (fun i h => f i (by omega)) := by
-  subst m
-  rfl
-
-theorem allTR_loop_congr {n m : Nat} (w : n = m) (f : (i : Nat) → i < n → Bool) (j : Nat) (h : j ≤ n) : allTR.loop n f j h = allTR.loop m (fun i h => f i (by omega)) j (by omega) := by
-  subst m
-  rfl
-
-@[csimp] theorem all_eq_allTR : @all = @allTR :=
-  funext fun n => funext fun f =>
-  let rec go : ∀ m n f, all (m + n) f = (all n (fun i h => f i (by omega)) && allTR.loop (m + n) f m (by omega))
-    | 0,      n, f => by
-      simp [allTR.loop]
-      have t : 0 + n = n := by omega
-      rw [all_congr t]
-    | succ m, n, f => by
-      have t : (m + 1) + n = m + (n + 1) := by omega
-      rw [allTR.loop]
-      simp only [succ_eq_add_one]
-      rw [all_congr t, allTR_loop_congr t, go, all, Bool.and_assoc]
-      congr
-      omega
-  go n 0 f
-
-end Nat
-
-namespace Prod
-
-/--
-`(start, stop).foldI f a` evaluates `f` on all the numbers
-from `start` (inclusive) to `stop` (exclusive) in increasing order:
-* `(5, 8).foldI f init = init |> f 5 |> f 6 |> f 7`
--/
-@[inline] def foldI {α : Type u} (i : Nat × Nat) (f : (j : Nat) → i.1 ≤ j → j < i.2 → α → α) (a : α) : α :=
-  (i.2 - i.1).fold (fun j _ => f (i.1 + j) (by omega) (by omega)) a
-
-/--
-`(start, stop).anyI f a` returns true if `f` is true for some natural number
-from `start` (inclusive) to `stop` (exclusive):
-* `(5, 8).anyI f = f 5 || f 6 || f 7`
--/
-@[inline] def anyI (i : Nat × Nat) (f : (j : Nat) → i.1 ≤ j → j < i.2 → Bool) : Bool :=
-  (i.2 - i.1).any (fun j _ => f (i.1 + j) (by omega) (by omega))
-
-/--
-`(start, stop).allI f a` returns true if `f` is true for all natural numbers
-from `start` (inclusive) to `stop` (exclusive):
-* `(5, 8).anyI f = f 5 && f 6 && f 7`
--/
-@[inline] def allI (i : Nat × Nat) (f : (j : Nat) → i.1 ≤ j → j < i.2 → Bool) : Bool :=
-  (i.2 - i.1).all (fun j _ => f (i.1 + j) (by omega) (by omega))
-
-end Prod

src/Init/Data/Nat/Lemmas.lean

@@ -651,8 +651,8 @@ theorem sub_mul_mod {x k n : Nat} (h₁ : n*k ≤ x) : (x - n*k) % n = x % n :=
   | .inr npos => Nat.mod_eq_of_lt (mod_lt _ npos)
 
 theorem mul_mod (a b n : Nat) : a * b % n = (a % n) * (b % n) % n := by
-  rw (occs := [1]) [← mod_add_div a n]
-  rw (occs := [1]) [← mod_add_div b n]
+  rw (occs := .pos [1]) [← mod_add_div a n]
+  rw (occs := .pos [1]) [← mod_add_div b n]
   rw [Nat.add_mul, Nat.mul_add, Nat.mul_add,
     Nat.mul_assoc, Nat.mul_assoc, ← Nat.mul_add n, add_mul_mod_self_left,
     Nat.mul_comm _ (n * (b / n)), Nat.mul_assoc, add_mul_mod_self_left]
@@ -846,18 +846,6 @@ protected theorem pow_lt_pow_iff_pow_mul_le_pow {a n m : Nat} (h : 1 < a) :
   rw [←Nat.pow_add_one, Nat.pow_le_pow_iff_right (by omega), Nat.pow_lt_pow_iff_right (by omega)]
   omega
 
-protected theorem lt_pow_self {n a : Nat} (h : 1 < a) : n < a ^ n := by
-  induction n with
-  | zero => exact Nat.zero_lt_one
-  | succ _ ih => exact Nat.lt_of_lt_of_le (Nat.add_lt_add_right ih 1) (Nat.pow_lt_pow_succ h)
-
-protected theorem lt_two_pow_self : n < 2 ^ n :=
-  Nat.lt_pow_self Nat.one_lt_two
-
-@[simp]
-protected theorem mod_two_pow_self : n % 2 ^ n = n :=
-  Nat.mod_eq_of_lt Nat.lt_two_pow_self
-
 @[simp]
 theorem two_pow_pred_mul_two (h : 0 < w) :
     2 ^ (w - 1) * 2 = 2 ^ w := by

src/Init/Data/Sum/Basic.lean

@@ -31,7 +31,7 @@ This file defines basic operations on the the sum type `α ⊕ β`.
 
 ## Further material
 
-See `Init.Data.Sum.Lemmas` for theorems about these definitions.
+See `Batteries.Data.Sum.Lemmas` for theorems about these definitions.
 
 ## Notes
 

src/Init/Data/UInt/Basic.lean

@@ -246,12 +246,6 @@ instance (a b : UInt64) : Decidable (a ≤ b) := UInt64.decLe a b
 instance : Max UInt64 := maxOfLe
 instance : Min UInt64 := minOfLe
 
-theorem usize_size_le : USize.size ≤ 18446744073709551616 := by
-  cases usize_size_eq <;> next h => rw [h]; decide
-
-theorem le_usize_size : 4294967296 ≤ USize.size := by
-  cases usize_size_eq <;> next h => rw [h]; decide
-
 @[extern "lean_usize_mul"]
 def USize.mul (a b : USize) : USize := ⟨a.toBitVec * b.toBitVec⟩
 @[extern "lean_usize_div"]
@@ -270,29 +264,10 @@ def USize.xor (a b : USize) : USize := ⟨a.toBitVec ^^^ b.toBitVec⟩
 def USize.shiftLeft (a b : USize) : USize := ⟨a.toBitVec <<< (mod b (USize.ofNat System.Platform.numBits)).toBitVec⟩
 @[extern "lean_usize_shift_right"]
 def USize.shiftRight (a b : USize) : USize := ⟨a.toBitVec >>> (mod b (USize.ofNat System.Platform.numBits)).toBitVec⟩
-/--
-Upcast a `Nat` less than `2^32` to a `USize`.
-This is lossless because `USize.size` is either `2^32` or `2^64`.
-This function is overridden with a native implementation.
--/
-@[extern "lean_usize_of_nat"]
-def USize.ofNat32 (n : @& Nat) (h : n < 4294967296) : USize :=
-  USize.ofNatCore n (Nat.lt_of_lt_of_le h le_usize_size)
 @[extern "lean_uint32_to_usize"]
 def UInt32.toUSize (a : UInt32) : USize := USize.ofNat32 a.toBitVec.toNat a.toBitVec.isLt
 @[extern "lean_usize_to_uint32"]
 def USize.toUInt32 (a : USize) : UInt32 := a.toNat.toUInt32
-/-- Converts a `UInt64` to a `USize` by reducing modulo `USize.size`. -/
-@[extern "lean_uint64_to_usize"]
-def UInt64.toUSize (a : UInt64) : USize := a.toNat.toUSize
-/--
-Upcast a `USize` to a `UInt64`.
-This is lossless because `USize.size` is either `2^32` or `2^64`.
-This function is overridden with a native implementation.
--/
-@[extern "lean_usize_to_uint64"]
-def USize.toUInt64 (a : USize) : UInt64 :=
-  UInt64.ofNatCore a.toBitVec.toNat (Nat.lt_of_lt_of_le a.toBitVec.isLt usize_size_le)
 
 instance : Mul USize       := ⟨USize.mul⟩
 instance : Mod USize       := ⟨USize.mod⟩

src/Init/Data/UInt/BasicAux.lean

@@ -94,8 +94,10 @@ def UInt32.toUInt64 (a : UInt32) : UInt64 := ⟨⟨a.toNat, Nat.lt_trans a.toBit
 
 instance UInt64.instOfNat : OfNat UInt64 n := ⟨UInt64.ofNat n⟩
 
-@[deprecated usize_size_pos (since := "2024-11-24")] theorem usize_size_gt_zero : USize.size > 0 :=
-  usize_size_pos
+theorem usize_size_gt_zero : USize.size > 0 := by
+  cases usize_size_eq with
+  | inl h => rw [h]; decide
+  | inr h => rw [h]; decide
 
 def USize.val (x : USize) : Fin USize.size := x.toBitVec.toFin
 @[extern "lean_usize_of_nat"]

src/Init/Data/UInt/Lemmas.lean

@@ -133,9 +133,6 @@ declare_uint_theorems UInt32
 declare_uint_theorems UInt64
 declare_uint_theorems USize
 
-theorem USize.toNat_ofNat_of_lt_32 {n : Nat} (h : n < 4294967296) : toNat (ofNat n) = n :=
-  toNat_ofNat_of_lt (Nat.lt_of_lt_of_le h le_usize_size)
-
 theorem UInt32.toNat_lt_of_lt {n : UInt32} {m : Nat} (h : m < size) : n < ofNat m → n.toNat < m := by
   simp [lt_def, BitVec.lt_def, UInt32.toNat, toBitVec_eq_of_lt h]
 
@@ -148,22 +145,22 @@ theorem UInt32.toNat_le_of_le {n : UInt32} {m : Nat} (h : m < size) : n ≤ ofNa
 theorem UInt32.le_toNat_of_le {n : UInt32} {m : Nat} (h : m < size) : ofNat m ≤ n → m ≤ n.toNat := by
   simp [le_def, BitVec.le_def, UInt32.toNat, toBitVec_eq_of_lt h]
 
-@[deprecated UInt8.toNat_zero (since := "2024-06-23")] protected abbrev UInt8.zero_toNat := @UInt8.toNat_zero
-@[deprecated UInt8.toNat_div (since := "2024-06-23")] protected abbrev UInt8.div_toNat := @UInt8.toNat_div
-@[deprecated UInt8.toNat_mod (since := "2024-06-23")] protected abbrev UInt8.mod_toNat := @UInt8.toNat_mod
+@[deprecated (since := "2024-06-23")] protected abbrev UInt8.zero_toNat := @UInt8.toNat_zero
+@[deprecated (since := "2024-06-23")] protected abbrev UInt8.div_toNat := @UInt8.toNat_div
+@[deprecated (since := "2024-06-23")] protected abbrev UInt8.mod_toNat := @UInt8.toNat_mod
 
-@[deprecated UInt16.toNat_zero (since := "2024-06-23")] protected abbrev UInt16.zero_toNat := @UInt16.toNat_zero
-@[deprecated UInt16.toNat_div (since := "2024-06-23")] protected abbrev UInt16.div_toNat := @UInt16.toNat_div
-@[deprecated UInt16.toNat_mod (since := "2024-06-23")] protected abbrev UInt16.mod_toNat := @UInt16.toNat_mod
+@[deprecated (since := "2024-06-23")] protected abbrev UInt16.zero_toNat := @UInt16.toNat_zero
+@[deprecated (since := "2024-06-23")] protected abbrev UInt16.div_toNat := @UInt16.toNat_div
+@[deprecated (since := "2024-06-23")] protected abbrev UInt16.mod_toNat := @UInt16.toNat_mod
 
-@[deprecated UInt32.toNat_zero (since := "2024-06-23")] protected abbrev UInt32.zero_toNat := @UInt32.toNat_zero
-@[deprecated UInt32.toNat_div (since := "2024-06-23")] protected abbrev UInt32.div_toNat := @UInt32.toNat_div
-@[deprecated UInt32.toNat_mod (since := "2024-06-23")] protected abbrev UInt32.mod_toNat := @UInt32.toNat_mod
+@[deprecated (since := "2024-06-23")] protected abbrev UInt32.zero_toNat := @UInt32.toNat_zero
+@[deprecated (since := "2024-06-23")] protected abbrev UInt32.div_toNat := @UInt32.toNat_div
+@[deprecated (since := "2024-06-23")] protected abbrev UInt32.mod_toNat := @UInt32.toNat_mod
 
-@[deprecated UInt64.toNat_zero (since := "2024-06-23")] protected abbrev UInt64.zero_toNat := @UInt64.toNat_zero
-@[deprecated UInt64.toNat_div (since := "2024-06-23")] protected abbrev UInt64.div_toNat := @UInt64.toNat_div
-@[deprecated UInt64.toNat_mod (since := "2024-06-23")] protected abbrev UInt64.mod_toNat := @UInt64.toNat_mod
+@[deprecated (since := "2024-06-23")] protected abbrev UInt64.zero_toNat := @UInt64.toNat_zero
+@[deprecated (since := "2024-06-23")] protected abbrev UInt64.div_toNat := @UInt64.toNat_div
+@[deprecated (since := "2024-06-23")] protected abbrev UInt64.mod_toNat := @UInt64.toNat_mod
 
-@[deprecated USize.toNat_zero (since := "2024-06-23")] protected abbrev USize.zero_toNat := @USize.toNat_zero
-@[deprecated USize.toNat_div (since := "2024-06-23")] protected abbrev USize.div_toNat := @USize.toNat_div
-@[deprecated USize.toNat_mod (since := "2024-06-23")] protected abbrev USize.mod_toNat := @USize.toNat_mod
+@[deprecated (since := "2024-06-23")] protected abbrev USize.zero_toNat := @USize.toNat_zero
+@[deprecated (since := "2024-06-23")] protected abbrev USize.div_toNat := @USize.toNat_div
+@[deprecated (since := "2024-06-23")] protected abbrev USize.mod_toNat := @USize.toNat_mod

src/Init/Data/Vector.lean

@@ -1,7 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
--/
-prelude
-import Init.Data.Vector.Basic

src/Init/Data/Vector/Basic.lean

@@ -1,256 +0,0 @@
-/-
-Copyright (c) 2024 Shreyas Srinivas. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Shreyas Srinivas, François G. Dorais, Kim Morrison
--/
-
-prelude
-import Init.Data.Array.Lemmas
-
-/-!
-# Vectors
-
-`Vector α n` is a thin wrapper around `Array α` for arrays of fixed size `n`.
--/
-
-/-- `Vector α n` is an `Array α` with size `n`. -/
-structure Vector (α : Type u) (n : Nat) extends Array α where
-  /-- Array size. -/
-  size_toArray : toArray.size = n
-deriving Repr, DecidableEq
-
-attribute [simp] Vector.size_toArray
-
-namespace Vector
-
-/-- Syntax for `Vector α n` -/
-syntax "#v[" withoutPosition(sepBy(term, ", ")) "]" : term
-
-open Lean in
-macro_rules
-  | `(#v[ $elems,* ]) => `(Vector.mk (n := $(quote elems.getElems.size)) #[$elems,*] rfl)
-
-/-- Custom eliminator for `Vector α n` through `Array α` -/
-@[elab_as_elim]
-def elimAsArray {motive : Vector α n → Sort u}
-    (mk : ∀ (a : Array α) (ha : a.size = n), motive ⟨a, ha⟩) :
-    (v : Vector α n) → motive v
-  | ⟨a, ha⟩ => mk a ha
-
-/-- Custom eliminator for `Vector α n` through `List α` -/
-@[elab_as_elim]
-def elimAsList {motive : Vector α n → Sort u}
-    (mk : ∀ (a : List α) (ha : a.length = n), motive ⟨⟨a⟩, ha⟩) :
-    (v : Vector α n) → motive v
-  | ⟨⟨a⟩, ha⟩ => mk a ha
-
-/-- The empty vector. -/
-@[inline] def empty : Vector α 0 := ⟨.empty, rfl⟩
-
-/-- Make an empty vector with pre-allocated capacity. -/
-@[inline] def mkEmpty (capacity : Nat) : Vector α 0 := ⟨.mkEmpty capacity, rfl⟩
-
-/-- Makes a vector of size `n` with all cells containing `v`. -/
-@[inline] def mkVector (n) (v : α) : Vector α n := ⟨mkArray n v, by simp⟩
-
-/-- Returns a vector of size `1` with element `v`. -/
-@[inline] def singleton (v : α) : Vector α 1 := ⟨#[v], rfl⟩
-
-instance [Inhabited α] : Inhabited (Vector α n) where
-  default := mkVector n default
-
-/-- Get an element of a vector using a `Fin` index. -/
-@[inline] def get (v : Vector α n) (i : Fin n) : α :=
-  v.toArray[(i.cast v.size_toArray.symm).1]
-
-/-- Get an element of a vector using a `USize` index and a proof that the index is within bounds. -/
-@[inline] def uget (v : Vector α n) (i : USize) (h : i.toNat < n) : α :=
-  v.toArray.uget i (v.size_toArray.symm ▸ h)
-
-instance : GetElem (Vector α n) Nat α fun _ i => i < n where
-  getElem x i h := get x ⟨i, h⟩
-
-/--
-Get an element of a vector using a `Nat` index. Returns the given default value if the index is out
-of bounds.
--/
-@[inline] def getD (v : Vector α n) (i : Nat) (default : α) : α := v.toArray.getD i default
-
-/-- The last element of a vector. Panics if the vector is empty. -/
-@[inline] def back! [Inhabited α] (v : Vector α n) : α := v.toArray.back!
-
-/-- The last element of a vector, or `none` if the array is empty. -/
-@[inline] def back? (v : Vector α n) : Option α := v.toArray.back?
-
-/-- The last element of a non-empty vector. -/
-@[inline] def back [NeZero n] (v : Vector α n) : α :=
-  -- TODO: change to just `v[n]`
-  have : Inhabited α := ⟨v[0]'(Nat.pos_of_neZero n)⟩
-  v.back!
-
-/-- The first element of a non-empty vector.  -/
-@[inline] def head [NeZero n] (v : Vector α n) := v[0]'(Nat.pos_of_neZero n)
-
-/-- Push an element `x` to the end of a vector. -/
-@[inline] def push (x : α) (v : Vector α n)  : Vector α (n + 1) :=
-  ⟨v.toArray.push x, by simp⟩
-
-/-- Remove the last element of a vector. -/
-@[inline] def pop (v : Vector α n) : Vector α (n - 1) :=
-  ⟨Array.pop v.toArray, by simp⟩
-
-/--
-Set an element in a vector using a `Nat` index, with a tactic provided proof that the index is in
-bounds.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def set (v : Vector α n) (i : Nat) (x : α) (h : i < n := by get_elem_tactic): Vector α n :=
-  ⟨v.toArray.set i x (by simp [*]), by simp⟩
-
-/--
-Set an element in a vector using a `Nat` index. Returns the vector unchanged if the index is out of
-bounds.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def setIfInBounds (v : Vector α n) (i : Nat) (x : α) : Vector α n :=
-  ⟨v.toArray.setIfInBounds i x, by simp⟩
-
-/--
-Set an element in a vector using a `Nat` index. Panics if the index is out of bounds.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def set! (v : Vector α n) (i : Nat) (x : α) : Vector α n :=
-  ⟨v.toArray.set! i x, by simp⟩
-
-/-- Append two vectors. -/
-@[inline] def append (v : Vector α n) (w : Vector α m) : Vector α (n + m) :=
-  ⟨v.toArray ++ w.toArray, by simp⟩
-
-instance : HAppend (Vector α n) (Vector α m) (Vector α (n + m)) where
-  hAppend := append
-
-/-- Creates a vector from another with a provably equal length. -/
-@[inline] protected def cast (h : n = m) (v : Vector α n) : Vector α m :=
-  ⟨v.toArray, by simp [*]⟩
-
-/--
-Extracts the slice of a vector from indices `start` to `stop` (exclusive). If `start ≥ stop`, the
-result is empty. If `stop` is greater than the size of the vector, the size is used instead.
--/
-@[inline] def extract (v : Vector α n) (start stop : Nat) : Vector α (min stop n - start) :=
-  ⟨v.toArray.extract start stop, by simp⟩
-
-/-- Maps elements of a vector using the function `f`. -/
-@[inline] def map (f : α → β) (v : Vector α n) : Vector β n :=
-  ⟨v.toArray.map f, by simp⟩
-
-/-- Maps corresponding elements of two vectors of equal size using the function `f`. -/
-@[inline] def zipWith (a : Vector α n) (b : Vector β n) (f : α → β → φ) : Vector φ n :=
-  ⟨Array.zipWith a.toArray b.toArray f, by simp⟩
-
-/-- The vector of length `n` whose `i`-th element is `f i`. -/
-@[inline] def ofFn (f : Fin n → α) : Vector α n :=
-  ⟨Array.ofFn f, by simp⟩
-
-/--
-Swap two elements of a vector using `Fin` indices.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def swap (v : Vector α n) (i j : Nat)
-    (hi : i < n := by get_elem_tactic) (hj : j < n := by get_elem_tactic) : Vector α n :=
-  ⟨v.toArray.swap i j (by simpa using hi) (by simpa using hj), by simp⟩
-
-/--
-Swap two elements of a vector using `Nat` indices. Panics if either index is out of bounds.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def swapIfInBounds (v : Vector α n) (i j : Nat) : Vector α n :=
-  ⟨v.toArray.swapIfInBounds i j, by simp⟩
-
-/--
-Swaps an element of a vector with a given value using a `Fin` index. The original value is returned
-along with the updated vector.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def swapAt (v : Vector α n) (i : Nat) (x : α) (hi : i < n := by get_elem_tactic) :
-    α × Vector α n :=
-  let a := v.toArray.swapAt i x (by simpa using hi)
-  ⟨a.fst, a.snd, by simp [a]⟩
-
-/--
-Swaps an element of a vector with a given value using a `Nat` index. Panics if the index is out of
-bounds. The original value is returned along with the updated vector.
-
-This will perform the update destructively provided that the vector has a reference count of 1.
--/
-@[inline] def swapAt! (v : Vector α n) (i : Nat) (x : α) : α × Vector α n :=
-  let a := v.toArray.swapAt! i x
-  ⟨a.fst, a.snd, by simp [a]⟩
-
-/-- The vector `#v[0,1,2,...,n-1]`. -/
-@[inline] def range (n : Nat) : Vector Nat n := ⟨Array.range n, by simp⟩
-
-/--
-Extract the first `m` elements of a vector. If `m` is greater than or equal to the size of the
-vector then the vector is returned unchanged.
--/
-@[inline] def take (v : Vector α n) (m : Nat) : Vector α (min m n) :=
-  ⟨v.toArray.take m, by simp⟩
-
-/--
-Deletes the first `m` elements of a vector. If `m` is greater than or equal to the size of the
-vector then the empty vector is returned.
--/
-@[inline] def drop (v : Vector α n) (m : Nat) : Vector α (n - m) :=
-  ⟨v.toArray.extract m v.size, by simp⟩
-
-/--
-Compares two vectors of the same size using a given boolean relation `r`. `isEqv v w r` returns
-`true` if and only if `r v[i] w[i]` is true for all indices `i`.
--/
-@[inline] def isEqv (v w : Vector α n) (r : α → α → Bool) : Bool :=
-  Array.isEqvAux v.toArray w.toArray (by simp) r n (by simp)
-
-instance [BEq α] : BEq (Vector α n) where
-  beq a b := isEqv a b (· == ·)
-
-/-- Reverse the elements of a vector. -/
-@[inline] def reverse (v : Vector α n) : Vector α n :=
-  ⟨v.toArray.reverse, by simp⟩
-
-/-- Delete an element of a vector using a `Nat` index and a tactic provided proof. -/
-@[inline] def eraseIdx (v : Vector α n) (i : Nat) (h : i < n := by get_elem_tactic) :
-    Vector α (n-1) :=
-  ⟨v.toArray.eraseIdx i (v.size_toArray.symm ▸ h), by simp [Array.size_eraseIdx]⟩
-
-/-- Delete an element of a vector using a `Nat` index. Panics if the index is out of bounds. -/
-@[inline] def eraseIdx! (v : Vector α n) (i : Nat) : Vector α (n-1) :=
-  if _ : i < n then
-    v.eraseIdx i
-  else
-    have : Inhabited (Vector α (n-1)) := ⟨v.pop⟩
-    panic! "index out of bounds"
-
-/-- Delete the first element of a vector. Returns the empty vector if the input vector is empty. -/
-@[inline] def tail (v : Vector α n) : Vector α (n-1) :=
-  if _ : 0 < n then
-    v.eraseIdx 0
-  else
-    v.cast (by omega)
-
-/--
-Finds the first index of a given value in a vector using `==` for comparison. Returns `none` if the
-no element of the index matches the given value.
--/
-@[inline] def indexOf? [BEq α] (v : Vector α n) (x : α) : Option (Fin n) :=
-  (v.toArray.indexOf? x).map (Fin.cast v.size_toArray)
-
-/-- Returns `true` when `v` is a prefix of the vector `w`. -/
-@[inline] def isPrefixOf [BEq α] (v : Vector α m) (w : Vector α n) : Bool :=
-  v.toArray.isPrefixOf w.toArray

src/Init/GetElem.lean

@@ -206,12 +206,12 @@ instance : GetElem (List α) Nat α fun as i => i < as.length where
 @[simp] theorem getElem_cons_zero (a : α) (as : List α) (h : 0 < (a :: as).length) : getElem (a :: as) 0 h = a := by
   rfl
 
-@[deprecated getElem_cons_zero (since := "2024-06-12")] abbrev cons_getElem_zero := @getElem_cons_zero
+@[deprecated (since := "2024-06-12")] abbrev cons_getElem_zero := @getElem_cons_zero
 
 @[simp] theorem getElem_cons_succ (a : α) (as : List α) (i : Nat) (h : i + 1 < (a :: as).length) : getElem (a :: as) (i+1) h = getElem as i (Nat.lt_of_succ_lt_succ h) := by
   rfl
 
-@[deprecated getElem_cons_succ (since := "2024-06-12")] abbrev cons_getElem_succ := @getElem_cons_succ
+@[deprecated (since := "2024-06-12")] abbrev cons_getElem_succ := @getElem_cons_succ
 
 @[simp] theorem getElem_mem : ∀ {l : List α} {n} (h : n < l.length), l[n]'h ∈ l
   | _ :: _, 0, _ => .head ..
@@ -223,8 +223,7 @@ theorem getElem_cons_drop_succ_eq_drop {as : List α} {i : Nat} (h : i < as.leng
   | _::_, 0   => rfl
   | _::_, i+1 => getElem_cons_drop_succ_eq_drop (i := i) _
 
-@[deprecated getElem_cons_drop_succ_eq_drop (since := "2024-11-05")]
-abbrev get_drop_eq_drop := @getElem_cons_drop_succ_eq_drop
+@[deprecated (since := "2024-11-05")] abbrev get_drop_eq_drop := @getElem_cons_drop_succ_eq_drop
 
 end List
 

src/Init/MetaTypes.lean

@@ -251,16 +251,10 @@ def neutralConfig : Simp.Config := {
 
 end Simp
 
-/-- Configuration for which occurrences that match an expression should be rewritten. -/
 inductive Occurrences where
-  /-- All occurrences should be rewritten. -/
   | all
-  /-- A list of indices for which occurrences should be rewritten. -/
   | pos (idxs : List Nat)
-  /-- A list of indices for which occurrences should not be rewritten. -/
   | neg (idxs : List Nat)
   deriving Inhabited, BEq
 
-instance : Coe (List Nat) Occurrences := ⟨.pos⟩
-
 end Lean.Meta

src/Init/Notation.lean

@@ -71,9 +71,9 @@ def prio : Category := {}
 
 /-- `prec` is a builtin syntax category for precedences. A precedence is a value
 that expresses how tightly a piece of syntax binds: for example `1 + 2 * 3` is
-parsed as `1 + (2 * 3)` because `*` has a higher precedence than `+`.
+parsed as `1 + (2 * 3)` because `*` has a higher pr0ecedence than `+`.
 Higher numbers denote higher precedence.
-In addition to literals like `37`, there are some special named precedence levels:
+In addition to literals like `37`, there are some special named priorities:
 * `arg` for the precedence of function arguments
 * `max` for the highest precedence used in term parsers (not actually the maximum possible value)
 * `lead` for the precedence of terms not supposed to be used as arguments

src/Init/Prelude.lean

@@ -2116,11 +2116,6 @@ theorem usize_size_eq : Or (Eq USize.size 4294967296) (Eq USize.size 18446744073
   | _, Or.inl rfl => Or.inl (of_decide_eq_true rfl)
   | _, Or.inr rfl => Or.inr (of_decide_eq_true rfl)
 
-theorem usize_size_pos : LT.lt 0 USize.size :=
-  match USize.size, usize_size_eq with
-  | _, Or.inl rfl => of_decide_eq_true rfl
-  | _, Or.inr rfl => of_decide_eq_true rfl
-
 /--
 A `USize` is an unsigned integer with the size of a word
 for the platform's architecture.
@@ -2160,7 +2155,24 @@ def USize.decEq (a b : USize) : Decidable (Eq a b) :=
 instance : DecidableEq USize := USize.decEq
 
 instance : Inhabited USize where
-  default := USize.ofNatCore 0 usize_size_pos
+  default := USize.ofNatCore 0 (match USize.size, usize_size_eq with
+    | _, Or.inl rfl => of_decide_eq_true rfl
+    | _, Or.inr rfl => of_decide_eq_true rfl)
+
+/--
+Upcast a `Nat` less than `2^32` to a `USize`.
+This is lossless because `USize.size` is either `2^32` or `2^64`.
+This function is overridden with a native implementation.
+-/
+@[extern "lean_usize_of_nat"]
+def USize.ofNat32 (n : @& Nat) (h : LT.lt n 4294967296) : USize where
+  toBitVec :=
+    BitVec.ofNatLt n (
+      match System.Platform.numBits, System.Platform.numBits_eq with
+      | _, Or.inl rfl => h
+      | _, Or.inr rfl => Nat.lt_trans h (of_decide_eq_true rfl)
+    )
+
 /--
 A `Nat` denotes a valid unicode codepoint if it is less than `0x110000`, and
 it is also not a "surrogate" character (the range `0xd800` to `0xdfff` inclusive).
@@ -3420,6 +3432,25 @@ class Hashable (α : Sort u) where
 
 export Hashable (hash)
 
+/-- Converts a `UInt64` to a `USize` by reducing modulo `USize.size`. -/
+@[extern "lean_uint64_to_usize"]
+opaque UInt64.toUSize (u : UInt64) : USize
+
+/--
+Upcast a `USize` to a `UInt64`.
+This is lossless because `USize.size` is either `2^32` or `2^64`.
+This function is overridden with a native implementation.
+-/
+@[extern "lean_usize_to_uint64"]
+def USize.toUInt64 (u : USize) : UInt64 where
+  toBitVec := BitVec.ofNatLt u.toBitVec.toNat (
+        let ⟨⟨n, h⟩⟩ := u
+        show LT.lt n _ from
+        match System.Platform.numBits, System.Platform.numBits_eq, h with
+        | _, Or.inl rfl, h => Nat.lt_trans h (of_decide_eq_true rfl)
+        | _, Or.inr rfl, h => h
+      )
+
 /-- An opaque hash mixing operation, used to implement hashing for tuples. -/
 @[extern "lean_uint64_mix_hash"]
 opaque mixHash (u₁ u₂ : UInt64) : UInt64

src/Init/ShareCommon.lean

@@ -5,7 +5,6 @@ Authors: Leonardo de Moura, Mario Carneiro
 -/
 prelude
 import Init.Util
-import Init.Data.UInt.Basic
 
 namespace ShareCommon
 /-

src/Init/SimpLemmas.lean

@@ -72,21 +72,6 @@ theorem let_body_congr {α : Sort u} {β : α → Sort v} {b b' : (a : α) →
     (a : α) (h : ∀ x, b x = b' x) : (let x := a; b x) = (let x := a; b' x) :=
   (funext h : b = b') ▸ rfl
 
-theorem letFun_unused {α : Sort u} {β : Sort v} (a : α) {b b' : β} (h : b = b') : @letFun α (fun _ => β) a (fun _ => b) = b' :=
-  h
-
-theorem letFun_congr {α : Sort u} {β : Sort v}  {a a' : α} {f f' : α → β} (h₁ : a = a') (h₂ : ∀ x, f x = f' x)
-    : @letFun α (fun _ => β) a f = @letFun α (fun _ => β) a' f' := by
-  rw [h₁, funext h₂]
-
-theorem letFun_body_congr {α : Sort u} {β : Sort v}  (a : α) {f f' : α → β} (h : ∀ x, f x = f' x)
-    : @letFun α (fun _ => β) a f = @letFun α (fun _ => β) a f' := by
-  rw [funext h]
-
-theorem letFun_val_congr {α : Sort u} {β : Sort v} {a a' : α} {f : α → β} (h : a = a')
-    : @letFun α (fun _ => β) a f = @letFun α (fun _ => β) a' f := by
-  rw [h]
-
 @[congr]
 theorem ite_congr {x y u v : α} {s : Decidable b} [Decidable c]
     (h₁ : b = c) (h₂ : c → x = u) (h₃ : ¬ c → y = v) : ite b x y = ite c u v := by

src/Init/Syntax.lean

@@ -30,7 +30,7 @@ Does nothing for non-`node` nodes, or if `i` is out of bounds of the node list.
 -/
 def setArg (stx : Syntax) (i : Nat) (arg : Syntax) : Syntax :=
   match stx with
-  | node info k args => node info k (args.setIfInBounds i arg)
+  | node info k args => node info k (args.setD i arg)
   | stx              => stx
 
 end Lean.Syntax

src/Init/System/IO.lean

@@ -462,16 +462,6 @@ Note that it is the caller's job to remove the file after use.
 -/
 @[extern "lean_io_create_tempfile"] opaque createTempFile : IO (Handle × FilePath)
 
-/--
-Creates a temporary directory in the most secure manner possible. There are no race conditions in the
-directory’s creation. The directory is readable and writable only by the creating user ID.
-
-Returns the new directory's path.
-
-It is the caller's job to remove the directory after use.
--/
-@[extern "lean_io_create_tempdir"] opaque createTempDir : IO FilePath
-
 end FS
 
 @[extern "lean_io_getenv"] opaque getEnv (var : @& String) : BaseIO (Option String)
@@ -484,6 +474,17 @@ namespace FS
 def withFile (fn : FilePath) (mode : Mode) (f : Handle → IO α) : IO α :=
   Handle.mk fn mode >>= f
 
+/--
+Like `createTempFile` but also takes care of removing the file after usage.
+-/
+def withTempFile [Monad m] [MonadFinally m] [MonadLiftT IO m] (f : Handle → FilePath → m α) :
+    m α := do
+  let (handle, path) ← createTempFile
+  try
+    f handle path
+  finally
+    removeFile path
+
 def Handle.putStrLn (h : Handle) (s : String) : IO Unit :=
   h.putStr (s.push '\n')
 
@@ -674,10 +675,8 @@ def appDir : IO FilePath := do
     | throw <| IO.userError s!"System.IO.appDir: unexpected filename '{p}'"
   FS.realPath p
 
-namespace FS
-
 /-- Create given path and all missing parents as directories. -/
-partial def createDirAll (p : FilePath) : IO Unit := do
+partial def FS.createDirAll (p : FilePath) : IO Unit := do
   if ← p.isDir then
     return ()
   if let some parent := p.parent then
@@ -694,7 +693,7 @@ partial def createDirAll (p : FilePath) : IO Unit := do
 /--
   Fully remove given directory by deleting all contained files and directories in an unspecified order.
   Fails if any contained entry cannot be deleted or was newly created during execution. -/
-partial def removeDirAll (p : FilePath) : IO Unit := do
+partial def FS.removeDirAll (p : FilePath) : IO Unit := do
   for ent in (← p.readDir) do
     if (← ent.path.isDir : Bool) then
       removeDirAll ent.path
@@ -702,32 +701,6 @@ partial def removeDirAll (p : FilePath) : IO Unit := do
       removeFile ent.path
   removeDir p
 
-/--
-Like `createTempFile`, but also takes care of removing the file after usage.
--/
-def withTempFile [Monad m] [MonadFinally m] [MonadLiftT IO m] (f : Handle → FilePath → m α) :
-    m α := do
-  let (handle, path) ← createTempFile
-  try
-    f handle path
-  finally
-    removeFile path
-
-/--
-Like `createTempDir`, but also takes care of removing the directory after usage.
-
-All files in the directory are recursively deleted, regardless of how or when they were created.
--/
-def withTempDir [Monad m] [MonadFinally m] [MonadLiftT IO m] (f : FilePath → m α) :
-    m α := do
-  let path ← createTempDir
-  try
-    f path
-  finally
-    removeDirAll path
-
-end FS
-
 namespace Process
 
 /-- Returns the current working directory of the calling process. -/

src/Init/Tactics.lean

@@ -428,11 +428,11 @@ macro "infer_instance" : tactic => `(tactic| exact inferInstance)
 /--
 `+opt` is short for `(opt := true)`. It sets the `opt` configuration option to `true`.
 -/
-syntax posConfigItem := " +" noWs ident
+syntax posConfigItem := "+" noWs ident
 /--
 `-opt` is short for `(opt := false)`. It sets the `opt` configuration option to `false`.
 -/
-syntax negConfigItem := " -" noWs ident
+syntax negConfigItem := "-" noWs ident
 /--
 `(opt := val)` sets the `opt` configuration option to `val`.
 

src/Lean/Compiler/IR/Borrow.lean

@@ -205,8 +205,8 @@ def getParamInfo (k : ParamMap.Key) : M (Array Param) := do
 
 /-- For each ps[i], if ps[i] is owned, then mark xs[i] as owned. -/
 def ownArgsUsingParams (xs : Array Arg) (ps : Array Param) : M Unit :=
-  xs.size.forM fun i _ => do
-    let x := xs[i]
+  xs.size.forM fun i => do
+    let x := xs[i]!
     let p := ps[i]!
     unless p.borrow do ownArg x
 
@@ -216,8 +216,8 @@ def ownArgsUsingParams (xs : Array Arg) (ps : Array Param) : M Unit :=
    we would have to insert a `dec xs[i]` after `f xs` and consequently
    "break" the tail call. -/
 def ownParamsUsingArgs (xs : Array Arg) (ps : Array Param) : M Unit :=
-  xs.size.forM fun i _ => do
-    let x := xs[i]
+  xs.size.forM fun i => do
+    let x := xs[i]!
     let p := ps[i]!
     match x with
     | Arg.var x => if (← isOwned x) then ownVar p.x

src/Lean/Compiler/IR/Boxing.lean

@@ -48,9 +48,9 @@ def requiresBoxedVersion (env : Environment) (decl : Decl) : Bool :=
 def mkBoxedVersionAux (decl : Decl) : N Decl := do
   let ps := decl.params
   let qs ← ps.mapM fun _ => do let x ← N.mkFresh; pure { x := x, ty := IRType.object, borrow := false : Param }
-  let (newVDecls, xs) ← qs.size.foldM (init := (#[], #[])) fun i _ (newVDecls, xs) => do
+  let (newVDecls, xs) ← qs.size.foldM (init := (#[], #[])) fun i (newVDecls, xs) => do
     let p := ps[i]!
-    let q := qs[i]
+    let q := qs[i]!
     if !p.ty.isScalar then
       pure (newVDecls, xs.push (Arg.var q.x))
     else

src/Lean/Compiler/IR/ElimDeadBranches.lean

@@ -63,7 +63,7 @@ partial def merge (v₁ v₂ : Value) : Value :=
   | top, _ => top
   | _, top => top
   | v₁@(ctor i₁ vs₁), v₂@(ctor i₂ vs₂) =>
-    if i₁ == i₂ then ctor i₁ <| vs₁.size.fold (init := #[]) fun i _ r => r.push (merge vs₁[i] vs₂[i]!)
+    if i₁ == i₂ then ctor i₁ <| vs₁.size.fold (init := #[]) fun i r => r.push (merge vs₁[i]! vs₂[i]!)
     else choice [v₁, v₂]
   | choice vs₁, choice vs₂ => choice <| vs₁.foldl (addChoice merge) vs₂
   | choice vs, v => choice <| addChoice merge vs v
@@ -225,8 +225,8 @@ def updateCurrFnSummary (v : Value) : M Unit := do
 def updateJPParamsAssignment (ys : Array Param) (xs : Array Arg) : M Bool := do
   let ctx ← read
   let currFnIdx := ctx.currFnIdx
-  ys.size.foldM (init := false) fun i _ r => do
-    let y := ys[i]
+  ys.size.foldM (init := false) fun i r => do
+    let y := ys[i]!
     let x := xs[i]!
     let yVal ← findVarValue y.x
     let xVal ← findArgValue x
@@ -282,8 +282,8 @@ partial def interpFnBody : FnBody → M Unit
 def inferStep : M Bool := do
   let ctx ← read
   modify fun s => { s with assignments := ctx.decls.map fun _ => {} }
-  ctx.decls.size.foldM (init := false) fun idx _ modified => do
-    match ctx.decls[idx] with
+  ctx.decls.size.foldM (init := false) fun idx modified => do
+    match ctx.decls[idx]! with
     | .fdecl (xs := ys) (body := b) .. => do
       let s ← get
       let currVals := s.funVals[idx]!
@@ -336,8 +336,8 @@ def elimDeadBranches (decls : Array Decl) : CompilerM (Array Decl) := do
   let funVals := s.funVals
   let assignments := s.assignments
   modify fun s =>
-    let env := decls.size.fold (init := s.env) fun i _ env =>
-      addFunctionSummary env decls[i].name funVals[i]!
+    let env := decls.size.fold (init := s.env) fun i env =>
+      addFunctionSummary env decls[i]!.name funVals[i]!
     { s with env := env }
   return decls.mapIdx fun i decl => elimDead assignments[i]! decl
 

src/Lean/Compiler/IR/EmitC.lean

@@ -108,9 +108,9 @@ def emitFnDeclAux (decl : Decl) (cppBaseName : String) (isExternal : Bool) : M U
     if ps.size > closureMaxArgs && isBoxedName decl.name then
       emit "lean_object**"
     else
-      ps.size.forM fun i _ => do
+      ps.size.forM fun i => do
         if i > 0 then emit ", "
-        emit (toCType ps[i].ty)
+        emit (toCType ps[i]!.ty)
     emit ")"
   emitLn ";"
 
@@ -321,22 +321,20 @@ def emitSSet (x : VarId) (n : Nat) (offset : Nat) (y : VarId) (t : IRType) : M U
 
 def emitJmp (j : JoinPointId) (xs : Array Arg) : M Unit := do
   let ps ← getJPParams j
-  if h : xs.size = ps.size then
-    xs.size.forM fun i _ => do
-      let p := ps[i]
-      let x := xs[i]
-      emit p.x; emit " = "; emitArg x; emitLn ";"
-    emit "goto "; emit j; emitLn ";"
-  else
-    do throw "invalid goto"
+  unless xs.size == ps.size do throw "invalid goto"
+  xs.size.forM fun i => do
+    let p := ps[i]!
+    let x := xs[i]!
+    emit p.x; emit " = "; emitArg x; emitLn ";"
+  emit "goto "; emit j; emitLn ";"
 
 def emitLhs (z : VarId) : M Unit := do
   emit z; emit " = "
 
 def emitArgs (ys : Array Arg) : M Unit :=
-  ys.size.forM fun i _ => do
+  ys.size.forM fun i => do
     if i > 0 then emit ", "
-    emitArg ys[i]
+    emitArg ys[i]!
 
 def emitCtorScalarSize (usize : Nat) (ssize : Nat) : M Unit := do
   if usize == 0 then emit ssize
@@ -348,8 +346,8 @@ def emitAllocCtor (c : CtorInfo) : M Unit := do
   emitCtorScalarSize c.usize c.ssize; emitLn ");"
 
 def emitCtorSetArgs (z : VarId) (ys : Array Arg) : M Unit :=
-  ys.size.forM fun i _ => do
-    emit "lean_ctor_set("; emit z; emit ", "; emit i; emit ", "; emitArg ys[i]; emitLn ");"
+  ys.size.forM fun i => do
+    emit "lean_ctor_set("; emit z; emit ", "; emit i; emit ", "; emitArg ys[i]!; emitLn ");"
 
 def emitCtor (z : VarId) (c : CtorInfo) (ys : Array Arg) : M Unit := do
   emitLhs z;
@@ -360,7 +358,7 @@ def emitCtor (z : VarId) (c : CtorInfo) (ys : Array Arg) : M Unit := do
 
 def emitReset (z : VarId) (n : Nat) (x : VarId) : M Unit := do
   emit "if (lean_is_exclusive("; emit x; emitLn ")) {";
-  n.forM fun i _ => do
+  n.forM fun i => do
     emit " lean_ctor_release("; emit x; emit ", "; emit i; emitLn ");"
   emit " "; emitLhs z; emit x; emitLn ";";
   emitLn "} else {";
@@ -401,12 +399,12 @@ def emitSimpleExternalCall (f : String) (ps : Array Param) (ys : Array Arg) : M
   emit f; emit "("
   -- We must remove irrelevant arguments to extern calls.
   discard <| ys.size.foldM
-    (fun i _ (first : Bool) =>
+    (fun i (first : Bool) =>
       if ps[i]!.ty.isIrrelevant then
         pure first
       else do
         unless first do emit ", "
-        emitArg ys[i]
+        emitArg ys[i]!
         pure false)
     true
   emitLn ");"
@@ -433,8 +431,8 @@ def emitPartialApp (z : VarId) (f : FunId) (ys : Array Arg) : M Unit := do
   let decl ← getDecl f
   let arity := decl.params.size;
   emitLhs z; emit "lean_alloc_closure((void*)("; emitCName f; emit "), "; emit arity; emit ", "; emit ys.size; emitLn ");";
-  ys.size.forM fun i _ => do
-    let y := ys[i]
+  ys.size.forM fun i => do
+    let y := ys[i]!
     emit "lean_closure_set("; emit z; emit ", "; emit i; emit ", "; emitArg y; emitLn ");"
 
 def emitApp (z : VarId) (f : VarId) (ys : Array Arg) : M Unit :=
@@ -546,36 +544,34 @@ That is, we have
 -/
 def overwriteParam (ps : Array Param) (ys : Array Arg) : Bool :=
   let n := ps.size;
-  n.any fun i _ =>
-    let p := ps[i]
-    (i+1, n).anyI fun j _ _ => paramEqArg p ys[j]!
+  n.any fun i =>
+    let p := ps[i]!
+    (i+1, n).anyI fun j => paramEqArg p ys[j]!
 
 def emitTailCall (v : Expr) : M Unit :=
   match v with
   | Expr.fap _ ys => do
     let ctx ← read
     let ps := ctx.mainParams
-    if h : ps.size = ys.size then
-      if overwriteParam ps ys then
-        emitLn "{"
-        ps.size.forM fun i _ => do
-          let p := ps[i]
-          let y := ys[i]
-          unless paramEqArg p y do
-            emit (toCType p.ty); emit " _tmp_"; emit i; emit " = "; emitArg y; emitLn ";"
-        ps.size.forM fun i _ => do
-          let p := ps[i]
-          let y := ys[i]
-          unless paramEqArg p y do emit p.x; emit " = _tmp_"; emit i; emitLn ";"
-        emitLn "}"
-      else
-        ys.size.forM fun i _ => do
-          let p := ps[i]
-          let y := ys[i]
-          unless paramEqArg p y do emit p.x; emit " = "; emitArg y; emitLn ";"
-      emitLn "goto _start;"
+    unless ps.size == ys.size do throw "invalid tail call"
+    if overwriteParam ps ys then
+      emitLn "{"
+      ps.size.forM fun i => do
+        let p := ps[i]!
+        let y := ys[i]!
+        unless paramEqArg p y do
+          emit (toCType p.ty); emit " _tmp_"; emit i; emit " = "; emitArg y; emitLn ";"
+      ps.size.forM fun i => do
+        let p := ps[i]!
+        let y := ys[i]!
+        unless paramEqArg p y do emit p.x; emit " = _tmp_"; emit i; emitLn ";"
+      emitLn "}"
     else
-      throw "invalid tail call"
+      ys.size.forM fun i => do
+        let p := ps[i]!
+        let y := ys[i]!
+        unless paramEqArg p y do emit p.x; emit " = "; emitArg y; emitLn ";"
+    emitLn "goto _start;"
   | _ => throw "bug at emitTailCall"
 
 mutual
@@ -658,16 +654,16 @@ def emitDeclAux (d : Decl) : M Unit := do
         if xs.size > closureMaxArgs && isBoxedName d.name then
           emit "lean_object** _args"
         else
-          xs.size.forM fun i _ => do
+          xs.size.forM fun i => do
             if i > 0 then emit ", "
-            let x := xs[i]
+            let x := xs[i]!
             emit (toCType x.ty); emit " "; emit x.x
         emit ")"
       else
         emit ("_init_" ++ baseName ++ "()")
       emitLn " {";
       if xs.size > closureMaxArgs && isBoxedName d.name then
-        xs.size.forM fun i _ => do
+        xs.size.forM fun i => do
           let x := xs[i]!
           emit "lean_object* "; emit x.x; emit " = _args["; emit i; emitLn "];"
       emitLn "_start:";

src/Lean/Compiler/IR/EmitLLVM.lean

@@ -571,9 +571,9 @@ def emitAllocCtor (builder : LLVM.Builder llvmctx)
 
 def emitCtorSetArgs (builder : LLVM.Builder llvmctx)
     (z : VarId) (ys : Array Arg) : M llvmctx Unit := do
-  ys.size.forM fun i _ => do
+  ys.size.forM fun i => do
     let zv ← emitLhsVal builder z
-    let (_yty, yv) ← emitArgVal builder ys[i]
+    let (_yty, yv) ← emitArgVal builder ys[i]!
     let iv ← constIntUnsigned i
     callLeanCtorSet builder zv iv yv
     emitLhsSlotStore builder z zv
@@ -702,8 +702,8 @@ def emitPartialApp (builder : LLVM.Builder llvmctx) (z : VarId) (f : FunId) (ys
                                     (← constIntUnsigned arity)
                                     (← constIntUnsigned ys.size)
   LLVM.buildStore builder zval zslot
-  ys.size.forM fun i _ => do
-    let (yty, yslot) ← emitArgSlot_ builder ys[i]
+  ys.size.forM fun i => do
+    let (yty, yslot) ← emitArgSlot_ builder ys[i]!
     let yval ← LLVM.buildLoad2 builder yty yslot
     callLeanClosureSetFn builder zval (← constIntUnsigned i) yval
 
@@ -922,7 +922,7 @@ def emitReset (builder : LLVM.Builder llvmctx) (z : VarId) (n : Nat) (x : VarId)
   buildIfThenElse_ builder "isExclusive" isExclusive
    (fun builder => do
      let xv ← emitLhsVal builder x
-     n.forM fun i _ => do
+     n.forM fun i => do
          callLeanCtorRelease builder xv (← constIntUnsigned i)
      emitLhsSlotStore builder z xv
      return ShouldForwardControlFlow.yes

src/Lean/Compiler/IR/ExpandResetReuse.lean

@@ -134,15 +134,15 @@ abbrev M := ReaderT Context (StateM Nat)
   modifyGet fun n => ({ idx := n }, n + 1)
 
 def releaseUnreadFields (y : VarId) (mask : Mask) (b : FnBody) : M FnBody :=
-  mask.size.foldM (init := b) fun i _ b =>
-    match mask[i] with
+  mask.size.foldM (init := b) fun i b =>
+    match mask.get! i with
     | some _ => pure b -- code took ownership of this field
     | none   => do
       let fld ← mkFresh
       pure (FnBody.vdecl fld IRType.object (Expr.proj i y) (FnBody.dec fld 1 true false b))
 
 def setFields (y : VarId) (zs : Array Arg) (b : FnBody) : FnBody :=
-  zs.size.fold (init := b) fun i _ b => FnBody.set y i zs[i] b
+  zs.size.fold (init := b) fun i b => FnBody.set y i (zs.get! i) b
 
 /-- Given `set x[i] := y`, return true iff `y := proj[i] x` -/
 def isSelfSet (ctx : Context) (x : VarId) (i : Nat) (y : Arg) : Bool :=

src/Lean/Compiler/IR/RC.lean

@@ -79,13 +79,13 @@ private def addDecForAlt (ctx : Context) (caseLiveVars altLiveVars : LiveVarSet)
 /-- `isFirstOcc xs x i = true` if `xs[i]` is the first occurrence of `xs[i]` in `xs` -/
 private def isFirstOcc (xs : Array Arg) (i : Nat) : Bool :=
   let x := xs[i]!
-  i.all fun j _ => xs[j]! != x
+  i.all fun j => xs[j]! != x
 
 /-- Return true if `x` also occurs in `ys` in a position that is not consumed.
    That is, it is also passed as a borrow reference. -/
 private def isBorrowParamAux (x : VarId) (ys : Array Arg) (consumeParamPred : Nat → Bool) : Bool :=
-  ys.size.any fun i _ =>
-    let y := ys[i]
+  ys.size.any fun i =>
+    let y := ys[i]!
     match y with
     | Arg.irrelevant => false
     | Arg.var y      => x == y && !consumeParamPred i
@@ -99,15 +99,15 @@ Return `n`, the number of times `x` is consumed.
 - `consumeParamPred i = true` if parameter `i` is consumed.
 -/
 private def getNumConsumptions (x : VarId) (ys : Array Arg) (consumeParamPred : Nat → Bool) : Nat :=
-  ys.size.fold (init := 0) fun i _ n =>
-    let y := ys[i]
+  ys.size.fold (init := 0) fun i n =>
+    let y := ys[i]!
     match y with
     | Arg.irrelevant => n
     | Arg.var y      => if x == y && consumeParamPred i then n+1 else n
 
 private def addIncBeforeAux (ctx : Context) (xs : Array Arg) (consumeParamPred : Nat → Bool) (b : FnBody) (liveVarsAfter : LiveVarSet) : FnBody :=
-  xs.size.fold (init := b) fun i _ b =>
-    let x := xs[i]
+  xs.size.fold (init := b) fun i b =>
+    let x := xs[i]!
     match x with
     | Arg.irrelevant => b
     | Arg.var x =>
@@ -128,8 +128,8 @@ private def addIncBefore (ctx : Context) (xs : Array Arg) (ps : Array Param) (b
 
 /-- See `addIncBeforeAux`/`addIncBefore` for the procedure that inserts `inc` operations before an application.  -/
 private def addDecAfterFullApp (ctx : Context) (xs : Array Arg) (ps : Array Param) (b : FnBody) (bLiveVars : LiveVarSet) : FnBody :=
-xs.size.fold (init := b) fun i _ b =>
-  match xs[i] with
+xs.size.fold (init := b) fun i b =>
+  match xs[i]! with
   | Arg.irrelevant => b
   | Arg.var x      =>
     /- We must add a `dec` if `x` must be consumed, it is alive after the application,

src/Lean/Compiler/LCNF/ElimDeadBranches.lean

@@ -587,15 +587,15 @@ def Decl.elimDeadBranches (decls : Array Decl) : CompilerM (Array Decl) := do
     refer to the docstring of `Decl.safe`.
     -/
     if decls[i]!.safe then .bot else .top
-  let mut funVals := decls.size.fold (init := .empty) fun i _ p => p.push (initialVal i)
+  let mut funVals := decls.size.fold (init := .empty) fun i p => p.push (initialVal i)
   let ctx := { decls }
   let mut state := { assignments, funVals }
   (_, state) ← inferMain |>.run ctx |>.run state
   funVals := state.funVals
   assignments := state.assignments
   modifyEnv fun e =>
-    decls.size.fold (init := e) fun i _ env =>
-      addFunctionSummary env decls[i].name funVals[i]!
+    decls.size.fold (init := e) fun i env =>
+      addFunctionSummary env decls[i]!.name funVals[i]!
 
   decls.mapIdxM fun i decl => if decl.safe then elimDead assignments[i]! decl else return decl
 

src/Lean/Compiler/LCNF/InferType.lean

@@ -76,8 +76,8 @@ def getType (fvarId : FVarId) : InferTypeM Expr := do
 
 def mkForallFVars (xs : Array Expr) (type : Expr) : InferTypeM Expr :=
   let b := type.abstract xs
-  xs.size.foldRevM (init := b) fun i _ b => do
-    let x := xs[i]
+  xs.size.foldRevM (init := b) fun i b => do
+    let x := xs[i]!
     let n ← InferType.getBinderName x.fvarId!
     let ty ← InferType.getType x.fvarId!
     let ty := ty.abstractRange i xs;

src/Lean/Compiler/LCNF/PassManager.lean

@@ -157,7 +157,9 @@ def installBeforeEachOccurrence (targetName : Name) (p : Pass → Pass) : PassIn
 def replacePass (targetName : Name) (p : Pass → Pass) (occurrence : Nat := 0) : PassInstaller where
   install passes := do
     let some idx := passes.findIdx? (fun p => p.name == targetName && p.occurrence == occurrence) | throwError s!"Tried to replace {targetName}, occurrence {occurrence} but {targetName} is not in the pass list"
-    return passes.modify idx p
+    let target := passes[idx]!
+    let replacement := p target
+    return passes.set! idx replacement
 
 def replaceEachOccurrence (targetName : Name) (p : Pass → Pass) : PassInstaller :=
     withEachOccurrence targetName (replacePass targetName p ·)

src/Lean/CoreM.lean

@@ -11,7 +11,6 @@ import Lean.ResolveName
 import Lean.Elab.InfoTree.Types
 import Lean.MonadEnv
 import Lean.Elab.Exception
-import Lean.Language.Basic
 
 namespace Lean
 register_builtin_option diagnostics : Bool := {
@@ -73,13 +72,6 @@ structure State where
   messages        : MessageLog     := {}
   /-- Info tree. We have the info tree here because we want to update it while adding attributes. -/
   infoState       : Elab.InfoState := {}
-  /--
-  Snapshot trees of asynchronous subtasks. As these are untyped and reported only at the end of the
-  command's main elaboration thread, they are only useful for basic message log reporting; for
-  incremental reporting and reuse within a long-running elaboration thread, types rooted in
-  `CommandParsedSnapshot` need to be adjusted.
-  -/
-  snapshotTasks : Array (Language.SnapshotTask Language.SnapshotTree) := #[]
   deriving Nonempty
 
 /-- Context for the CoreM monad. -/
@@ -188,8 +180,7 @@ instance : Elab.MonadInfoTree CoreM where
   modifyInfoState f := modify fun s => { s with infoState := f s.infoState }
 
 @[inline] def modifyCache (f : Cache → Cache) : CoreM Unit :=
-  modify fun ⟨env, next, ngen, trace, cache, messages, infoState, snaps⟩ =>
-   ⟨env, next, ngen, trace, f cache, messages, infoState, snaps⟩
+  modify fun ⟨env, next, ngen, trace, cache, messages, infoState⟩ => ⟨env, next, ngen, trace, f cache, messages, infoState⟩
 
 @[inline] def modifyInstLevelTypeCache (f : InstantiateLevelCache → InstantiateLevelCache) : CoreM Unit :=
   modifyCache fun ⟨c₁, c₂⟩ => ⟨f c₁, c₂⟩
@@ -364,83 +355,13 @@ instance : MonadLog CoreM where
     if (← read).suppressElabErrors then
       -- discard elaboration errors, except for a few important and unlikely misleading ones, on
       -- parse error
-      unless msg.data.hasTag (· matches `Elab.synthPlaceholder | `Tactic.unsolvedGoals | `trace) do
+      unless msg.data.hasTag (· matches `Elab.synthPlaceholder | `Tactic.unsolvedGoals) do
         return
 
     let ctx ← read
     let msg := { msg with data := MessageData.withNamingContext { currNamespace := ctx.currNamespace, openDecls := ctx.openDecls } msg.data };
     modify fun s => { s with messages := s.messages.add msg }
 
-/--
-Includes a given task (such as from `wrapAsyncAsSnapshot`) in the overall snapshot tree for this
-command's elaboration, making its result available to reporting and the language server. The
-reporter will not know about this snapshot tree node until the main elaboration thread for this
-command has finished so this function is not useful for incremental reporting within a longer
-elaboration thread but only for tasks that outlive it such as background kernel checking or proof
-elaboration.
--/
-def logSnapshotTask (task : Language.SnapshotTask Language.SnapshotTree) : CoreM Unit :=
-  modify fun s => { s with snapshotTasks := s.snapshotTasks.push task }
-
-/-- Wraps the given action for use in `EIO.asTask` etc., discarding its final monadic state. -/
-def wrapAsync (act : Unit → CoreM α) : CoreM (EIO Exception α) := do
-  let st ← get
-  let ctx ← read
-  let heartbeats := (← IO.getNumHeartbeats) - ctx.initHeartbeats
-  return withCurrHeartbeats (do
-      -- include heartbeats since start of elaboration in new thread as well such that forking off
-      -- an action doesn't suddenly allow it to succeed from a lower heartbeat count
-      IO.addHeartbeats heartbeats.toUInt64
-      act () : CoreM _)
-    |>.run' ctx st
-
-/-- Option for capturing output to stderr during elaboration. -/
-register_builtin_option stderrAsMessages : Bool := {
-  defValue := true
-  group    := "server"
-  descr    := "(server) capture output to the Lean stderr channel (such as from `dbg_trace`) during elaboration of a command as a diagnostic message"
-}
-
-open Language in
-/--
-Wraps the given action for use in `BaseIO.asTask` etc., discarding its final state except for
-`logSnapshotTask` tasks, which are reported as part of the returned tree.
--/
-def wrapAsyncAsSnapshot (act : Unit → CoreM Unit) (desc : String := by exact decl_name%.toString) :
-    CoreM (BaseIO SnapshotTree) := do
-  let t ← wrapAsync fun _ => do
-    IO.FS.withIsolatedStreams (isolateStderr := stderrAsMessages.get (← getOptions)) do
-      let tid ← IO.getTID
-      -- reset trace state and message log so as not to report them twice
-      modify ({ · with messages := {}, traceState := { tid } })
-      try
-        withTraceNode `Elab.async (fun _ => return desc) do
-          act ()
-      catch e =>
-        logError e.toMessageData
-      finally
-        addTraceAsMessages
-      get
-  let ctx ← readThe Core.Context
-  return do
-    match (← t.toBaseIO) with
-    | .ok (output, st) =>
-      let mut msgs := st.messages
-      if !output.isEmpty then
-        msgs := msgs.add {
-          fileName := ctx.fileName
-          severity := MessageSeverity.information
-          pos      := ctx.fileMap.toPosition <| ctx.ref.getPos?.getD 0
-          data     := output
-        }
-      return .mk {
-        desc
-        diagnostics := (← Language.Snapshot.Diagnostics.ofMessageLog msgs)
-        traces := st.traceState
-      } st.snapshotTasks
-    -- interrupt or abort exception as `try catch` above should have caught any others
-    | .error _ => default
-
 end Core
 
 export Core (CoreM mkFreshUserName checkSystem withCurrHeartbeats)

src/Lean/Data/HashMap.lean

@@ -277,23 +277,4 @@ attribute [deprecated Std.HashMap.empty (since := "2024-08-08")] mkHashMap
 attribute [deprecated Std.HashMap.empty (since := "2024-08-08")] HashMap.empty
 attribute [deprecated Std.HashMap.ofList (since := "2024-08-08")] HashMap.ofList
 
-attribute [deprecated Std.HashMap.insert (since := "2024-08-08")] HashMap.insert
-attribute [deprecated Std.HashMap.containsThenInsert (since := "2024-08-08")] HashMap.insert'
-attribute [deprecated Std.HashMap.insertIfNew (since := "2024-08-08")] HashMap.insertIfNew
-attribute [deprecated Std.HashMap.erase (since := "2024-08-08")] HashMap.erase
-attribute [deprecated "Use `m[k]?` instead." (since := "2024-08-08")] HashMap.findEntry?
-attribute [deprecated "Use `m[k]?` instead." (since := "2024-08-08")] HashMap.find?
-attribute [deprecated "Use `m[k]?.getD` instead." (since := "2024-08-08")] HashMap.findD
-attribute [deprecated "Use `m[k]!` instead." (since := "2024-08-08")] HashMap.find!
-attribute [deprecated Std.HashMap.contains (since := "2024-08-08")] HashMap.contains
-attribute [deprecated Std.HashMap.foldM (since := "2024-08-08")] HashMap.foldM
-attribute [deprecated Std.HashMap.fold (since := "2024-08-08")] HashMap.fold
-attribute [deprecated Std.HashMap.forM (since := "2024-08-08")] HashMap.forM
-attribute [deprecated Std.HashMap.size (since := "2024-08-08")] HashMap.size
-attribute [deprecated Std.HashMap.isEmpty (since := "2024-08-08")] HashMap.isEmpty
-attribute [deprecated Std.HashMap.toList (since := "2024-08-08")] HashMap.toList
-attribute [deprecated Std.HashMap.toArray (since := "2024-08-08")] HashMap.toArray
-attribute [deprecated "Deprecateed without a replacement." (since := "2024-08-08")] HashMap.numBuckets
-attribute [deprecated "Deprecateed without a replacement." (since := "2024-08-08")] HashMap.ofListWith
-
 end Lean.HashMap

src/Lean/Data/PersistentArray.lean

@@ -4,7 +4,6 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Leonardo de Moura
 -/
 prelude
-import Init.Data.Nat.Fold
 import Init.Data.Array.Basic
 import Init.NotationExtra
 import Init.Data.ToString.Macro
@@ -372,7 +371,7 @@ instance : ToString Stats := ⟨Stats.toString⟩
 end PersistentArray
 
 def mkPersistentArray {α : Type u} (n : Nat) (v : α) : PArray α :=
-  n.fold (init := PersistentArray.empty) fun _ _ p => p.push v
+  n.fold (init := PersistentArray.empty) fun _ p => p.push v
 
 @[inline] def mkPArray {α : Type u} (n : Nat) (v : α) : PArray α :=
   mkPersistentArray n v

src/Lean/Elab.lean

@@ -23,7 +23,6 @@ import Lean.Elab.Quotation
 import Lean.Elab.Syntax
 import Lean.Elab.Do
 import Lean.Elab.StructInst
-import Lean.Elab.MutualInductive
 import Lean.Elab.Inductive
 import Lean.Elab.Structure
 import Lean.Elab.Print

src/Lean/Elab/App.lean

@@ -807,8 +807,8 @@ def getElabElimExprInfo (elimExpr : Expr) : MetaM ElabElimInfo := do
     These are the primary set of major parameters.
     -/
     let initMotiveFVars : CollectFVars.State := motiveArgs.foldl (init := {}) collectFVars
-    let motiveFVars ← xs.size.foldRevM (init := initMotiveFVars) fun i _ s => do
-      let x := xs[i]
+    let motiveFVars ← xs.size.foldRevM (init := initMotiveFVars) fun i s => do
+      let x := xs[i]!
       if s.fvarSet.contains x.fvarId! then
         return collectFVars s (← inferType x)
       else
@@ -1150,33 +1150,48 @@ private def throwLValError (e : Expr) (eType : Expr) (msg : MessageData) : TermE
   throwError "{msg}{indentExpr e}\nhas type{indentExpr eType}"
 
 /--
-`findMethod? S fName` tries the for each namespace `S'` in the resolution order for `S` to resolve the name `S'.fname`.
-If it resolves to `name`, returns `(S', name)`.
+`findMethod? S fName` tries the following for each namespace `S'` in the resolution order for `S`:
+- If `env` contains `S' ++ fName`, returns `(S', S' ++ fName)`
+- Otherwise if `env` contains private name `prv` for `S' ++ fName`, returns `(S', prv)`
 -/
 private partial def findMethod? (structName fieldName : Name) : MetaM (Option (Name × Name)) := do
   let env ← getEnv
   let find? structName' : MetaM (Option (Name × Name)) := do
     let fullName := structName' ++ fieldName
-    -- We do not want to make use of the current namespace for resolution.
-    let candidates := ResolveName.resolveGlobalName (← getEnv) Name.anonymous (← getOpenDecls) fullName
-      |>.filter (fun (_, fieldList) => fieldList.isEmpty)
-      |>.map Prod.fst
-    match candidates with
-    | []          => return none
-    | [fullName'] => return some (structName', fullName')
-    | _ => throwError "\
-      invalid field notation '{fieldName}', the name '{fullName}' is ambiguous, possible interpretations: \
-      {MessageData.joinSep (candidates.map (m!"'{.ofConstName ·}'")) ", "}"
+    if env.contains fullName then
+      return some (structName', fullName)
+    let fullNamePrv := mkPrivateName env fullName
+    if env.contains fullNamePrv then
+      return some (structName', fullNamePrv)
+    return none
   -- Optimization: the first element of the resolution order is `structName`,
   -- so we can skip computing the resolution order in the common case
   -- of the name resolving in the `structName` namespace.
   find? structName <||> do
     let resolutionOrder ← if isStructure env structName then getStructureResolutionOrder structName else pure #[structName]
-    for ns in resolutionOrder[1:resolutionOrder.size] do
-      if let some res ← find? ns then
+    for h : i in [1:resolutionOrder.size] do
+      if let some res ← find? resolutionOrder[i] then
         return res
     return none
 
+/--
+  Return `some (structName', fullName)` if `structName ++ fieldName` is an alias for `fullName`, and
+  `fullName` is of the form `structName' ++ fieldName`.
+
+  TODO: if there is more than one applicable alias, it returns `none`. We should consider throwing an error or
+  warning.
+-/
+private def findMethodAlias? (env : Environment) (structName fieldName : Name) : Option (Name × Name) :=
+  let fullName := structName ++ fieldName
+  -- We never skip `protected` aliases when resolving dot-notation.
+  let aliasesCandidates := getAliases env fullName (skipProtected := false) |>.filterMap fun alias =>
+    match alias.eraseSuffix? fieldName with
+    | none => none
+    | some structName' => some (structName', alias)
+  match aliasesCandidates with
+  | [r] => some r
+  | _   => none
+
 private def throwInvalidFieldNotation (e eType : Expr) : TermElabM α :=
   throwLValError e eType "invalid field notation, type is not of the form (C ...) where C is a constant"
 
@@ -1208,22 +1223,30 @@ private def resolveLValAux (e : Expr) (eType : Expr) (lval : LVal) : TermElabM L
         throwLValError e eType m!"invalid projection, structure has only {numFields} field(s)"
   | some structName, LVal.fieldName _ fieldName _ _ =>
     let env ← getEnv
+    let searchEnv : Unit → TermElabM LValResolution := fun _ => do
+      if let some (baseStructName, fullName) ← findMethod? structName (.mkSimple fieldName) then
+        return LValResolution.const baseStructName structName fullName
+      else if let some (structName', fullName) := findMethodAlias? env structName (.mkSimple fieldName) then
+        return LValResolution.const structName' structName' fullName
+      else
+        throwLValError e eType
+          m!"invalid field '{fieldName}', the environment does not contain '{Name.mkStr structName fieldName}'"
+    -- search local context first, then environment
+    let searchCtx : Unit → TermElabM LValResolution := fun _ => do
+      let fullName := Name.mkStr structName fieldName
+      for localDecl in (← getLCtx) do
+        if localDecl.isAuxDecl then
+          if let some localDeclFullName := (← read).auxDeclToFullName.find? localDecl.fvarId then
+            if fullName == (privateToUserName? localDeclFullName).getD localDeclFullName then
+              /- LVal notation is being used to make a "local" recursive call. -/
+              return LValResolution.localRec structName fullName localDecl.toExpr
+      searchEnv ()
     if isStructure env structName then
-      if let some baseStructName := findField? env structName (Name.mkSimple fieldName) then
-        return LValResolution.projFn baseStructName structName (Name.mkSimple fieldName)
-    -- Search the local context first
-    let fullName := Name.mkStr structName fieldName
-    for localDecl in (← getLCtx) do
-      if localDecl.isAuxDecl then
-        if let some localDeclFullName := (← read).auxDeclToFullName.find? localDecl.fvarId then
-          if fullName == (privateToUserName? localDeclFullName).getD localDeclFullName then
-            /- LVal notation is being used to make a "local" recursive call. -/
-            return LValResolution.localRec structName fullName localDecl.toExpr
-    -- Then search the environment
-    if let some (baseStructName, fullName) ← findMethod? structName (.mkSimple fieldName) then
-      return LValResolution.const baseStructName structName fullName
-    throwLValError e eType
-      m!"invalid field '{fieldName}', the environment does not contain '{Name.mkStr structName fieldName}'"
+      match findField? env structName (Name.mkSimple fieldName) with
+      | some baseStructName => return LValResolution.projFn baseStructName structName (Name.mkSimple fieldName)
+      | none                => searchCtx ()
+    else
+      searchCtx ()
   | none, LVal.fieldName _ _ (some suffix) _ =>
     if e.isConst then
       throwUnknownConstant (e.constName! ++ suffix)
@@ -1303,7 +1326,7 @@ Otherwise, if there isn't another parameter with the same name, we add `e` to `n
 
 Remark: `fullName` is the name of the resolved "field" access function. It is used for reporting errors
 -/
-private partial def addLValArg (baseName : Name) (fullName : Name) (e : Expr) (args : Array Arg) (namedArgs : Array NamedArg) (f : Expr) (explicit : Bool) :
+private partial def addLValArg (baseName : Name) (fullName : Name) (e : Expr) (args : Array Arg) (namedArgs : Array NamedArg) (f : Expr) :
     MetaM (Array Arg × Array NamedArg) := do
   withoutModifyingState <| go f (← inferType f) 0 namedArgs (namedArgs.map (·.name)) true
 where
@@ -1328,11 +1351,11 @@ where
         /- If there is named argument with name `xDecl.userName`, then it is accounted for and we can't make use of it. -/
         remainingNamedArgs := remainingNamedArgs.eraseIdx idx
       else
-        if ← typeMatchesBaseName xDecl.type baseName then
-          /- We found a type of the form (baseName ...), or we found the first explicit argument in useFirstExplicit mode.
-             First, we check if the current argument is one that can be used positionally,
+        if (← typeMatchesBaseName xDecl.type baseName) then
+          /- We found a type of the form (baseName ...).
+             First, we check if the current argument is an explicit one,
              and if the current explicit position "fits" at `args` (i.e., it must be ≤ arg.size) -/
-          if h : argIdx ≤ args.size ∧ (explicit || bInfo.isExplicit) then
+          if h : argIdx ≤ args.size ∧ bInfo.isExplicit then
             /- We can insert `e` as an explicit argument -/
             return (args.insertIdx argIdx (Arg.expr e), namedArgs)
           else
@@ -1340,13 +1363,13 @@ where
                if there isn't an argument with the same name occurring before it. -/
             if !allowNamed || unusableNamedArgs.contains xDecl.userName then
               throwError "\
-                invalid field notation, function '{.ofConstName fullName}' has argument with the expected type\
+                invalid field notation, function '{fullName}' has argument with the expected type\
                 {indentExpr xDecl.type}\n\
                 but it cannot be used"
             else
               return (args, namedArgs.push { name := xDecl.userName, val := Arg.expr e })
         /- Advance `argIdx` and update seen named arguments. -/
-        if explicit || bInfo.isExplicit then
+        if bInfo.isExplicit then
           argIdx := argIdx + 1
         unusableNamedArgs := unusableNamedArgs.push xDecl.userName
     /- If named arguments aren't allowed, then it must still be possible to pass the value as an explicit argument.
@@ -1357,7 +1380,7 @@ where
       if let some f' ← coerceToFunction? (mkAppN f xs) then
         return ← go f' (← inferType f') argIdx remainingNamedArgs unusableNamedArgs false
     throwError "\
-      invalid field notation, function '{.ofConstName fullName}' does not have argument with type ({.ofConstName baseName} ...) that can be used, \
+      invalid field notation, function '{fullName}' does not have argument with type ({baseName} ...) that can be used, \
       it must be explicit or implicit with a unique name"
 
 /-- Adds the `TermInfo` for the field of a projection. See `Lean.Parser.Term.identProjKind`. -/
@@ -1403,7 +1426,7 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp
       let projFn ← mkConst constName
       let projFn ← addProjTermInfo lval.getRef projFn
       if lvals.isEmpty then
-        let (args, namedArgs) ← addLValArg baseStructName constName f args namedArgs projFn explicit
+        let (args, namedArgs) ← addLValArg baseStructName constName f args namedArgs projFn
         elabAppArgs projFn namedArgs args expectedType? explicit ellipsis
       else
         let f ← elabAppArgs projFn #[] #[Arg.expr f] (expectedType? := none) (explicit := false) (ellipsis := false)
@@ -1411,7 +1434,7 @@ private def elabAppLValsAux (namedArgs : Array NamedArg) (args : Array Arg) (exp
     | LValResolution.localRec baseName fullName fvar =>
       let fvar ← addProjTermInfo lval.getRef fvar
       if lvals.isEmpty then
-        let (args, namedArgs) ← addLValArg baseName fullName f args namedArgs fvar explicit
+        let (args, namedArgs) ← addLValArg baseName fullName f args namedArgs fvar
         elabAppArgs fvar namedArgs args expectedType? explicit ellipsis
       else
         let f ← elabAppArgs fvar #[] #[Arg.expr f] (expectedType? := none) (explicit := false) (ellipsis := false)

src/Lean/Elab/Command.lean

@@ -84,7 +84,6 @@ structure State where
   ngen           : NameGenerator := {}
   infoState      : InfoState := {}
   traceState     : TraceState := {}
-  snapshotTasks  : Array (Language.SnapshotTask Language.SnapshotTree) := #[]
   deriving Nonempty
 
 structure Context where
@@ -115,7 +114,8 @@ structure Context where
   -/
   suppressElabErrors : Bool := false
 
-abbrev CommandElabM := ReaderT Context $ StateRefT State $ EIO Exception
+abbrev CommandElabCoreM (ε) := ReaderT Context $ StateRefT State $ EIO ε
+abbrev CommandElabM := CommandElabCoreM Exception
 abbrev CommandElab  := Syntax → CommandElabM Unit
 structure Linter where
   run : Syntax → CommandElabM Unit
@@ -198,6 +198,36 @@ instance : AddErrorMessageContext CommandElabM where
     let msg ← addMacroStack msg ctx.macroStack
     return (ref, msg)
 
+def mkMessageAux (ctx : Context) (ref : Syntax) (msgData : MessageData) (severity : MessageSeverity) : Message :=
+  let pos := ref.getPos?.getD ctx.cmdPos
+  let endPos := ref.getTailPos?.getD pos
+  mkMessageCore ctx.fileName ctx.fileMap msgData severity pos endPos
+
+private def addTraceAsMessagesCore (ctx : Context) (log : MessageLog) (traceState : TraceState) : MessageLog := Id.run do
+  if traceState.traces.isEmpty then return log
+  let mut traces : Std.HashMap (String.Pos × String.Pos) (Array MessageData) := ∅
+  for traceElem in traceState.traces do
+    let ref := replaceRef traceElem.ref ctx.ref
+    let pos := ref.getPos?.getD 0
+    let endPos := ref.getTailPos?.getD pos
+    traces := traces.insert (pos, endPos) <| traces.getD (pos, endPos) #[] |>.push traceElem.msg
+  let mut log := log
+  let traces' := traces.toArray.qsort fun ((a, _), _) ((b, _), _) => a < b
+  for ((pos, endPos), traceMsg) in traces' do
+    let data := .tagged `trace <| .joinSep traceMsg.toList "\n"
+    log := log.add <| mkMessageCore ctx.fileName ctx.fileMap data .information pos endPos
+  return log
+
+private def addTraceAsMessages : CommandElabM Unit := do
+  let ctx ← read
+  -- do not add trace messages if `trace.profiler.output` is set as it would be redundant and
+  -- pretty printing the trace messages is expensive
+  if trace.profiler.output.get? (← getOptions) |>.isNone then
+    modify fun s => { s with
+      messages          := addTraceAsMessagesCore ctx s.messages s.traceState
+      traceState.traces := {}
+    }
+
 private def runCore (x : CoreM α) : CommandElabM α := do
   let s ← get
   let ctx ← read
@@ -223,7 +253,6 @@ private def runCore (x : CoreM α) : CommandElabM α := do
     nextMacroScope := s.nextMacroScope
     infoState.enabled := s.infoState.enabled
     traceState := s.traceState
-    snapshotTasks := s.snapshotTasks
   }
   let (ea, coreS) ← liftM x
   modify fun s => { s with
@@ -232,7 +261,6 @@ private def runCore (x : CoreM α) : CommandElabM α := do
     ngen              := coreS.ngen
     infoState.trees   := s.infoState.trees.append coreS.infoState.trees
     traceState.traces := coreS.traceState.traces.map fun t => { t with ref := replaceRef t.ref ctx.ref }
-    snapshotTasks     := coreS.snapshotTasks
     messages          := s.messages ++ coreS.messages
   }
   return ea
@@ -240,6 +268,10 @@ private def runCore (x : CoreM α) : CommandElabM α := do
 def liftCoreM (x : CoreM α) : CommandElabM α := do
   MonadExcept.ofExcept (← runCore (observing x))
 
+private def ioErrorToMessage (ctx : Context) (ref : Syntax) (err : IO.Error) : Message :=
+  let ref := getBetterRef ref ctx.macroStack
+  mkMessageAux ctx ref (toString err) MessageSeverity.error
+
 @[inline] def liftIO {α} (x : IO α) : CommandElabM α := do
   let ctx ← read
   IO.toEIO (fun (ex : IO.Error) => Exception.error ctx.ref ex.toString) x
@@ -262,8 +294,9 @@ instance : MonadLog CommandElabM where
   logMessage msg := do
     if (← read).suppressElabErrors then
       -- discard elaboration errors on parse error
-      unless msg.data.hasTag (· matches `trace) do
-        return
+      -- NOTE: unlike `CoreM`'s `logMessage`, we do not currently have any command-level errors that
+      -- we want to allowlist
+      return
     let currNamespace ← getCurrNamespace
     let openDecls ← getOpenDecls
     let msg := { msg with data := MessageData.withNamingContext { currNamespace := currNamespace, openDecls := openDecls } msg.data }
@@ -289,61 +322,6 @@ def runLinters (stx : Syntax) : CommandElabM Unit := do
             finally
               modify fun s => { savedState with messages := s.messages }
 
-/--
-Catches and logs exceptions occurring in `x`. Unlike `try catch` in `CommandElabM`, this function
-catches interrupt exceptions as well and thus is intended for use at the top level of elaboration.
-Interrupt and abort exceptions are caught but not logged.
--/
-@[inline] def withLoggingExceptions (x : CommandElabM Unit) : CommandElabM Unit := fun ctx ref =>
-  EIO.catchExceptions (withLogging x ctx ref) (fun _ => pure ())
-
-@[inherit_doc Core.wrapAsync]
-def wrapAsync (act : Unit → CommandElabM α) : CommandElabM (EIO Exception α) := do
-  return act () |>.run (← read) |>.run' (← get)
-
-open Language in
-@[inherit_doc Core.wrapAsyncAsSnapshot]
--- `CoreM` and `CommandElabM` are too different to meaningfully share this code
-def wrapAsyncAsSnapshot (act : Unit → CommandElabM Unit)
-    (desc : String := by exact decl_name%.toString) :
-    CommandElabM (BaseIO SnapshotTree) := do
-  let t ← wrapAsync fun _ => do
-    IO.FS.withIsolatedStreams (isolateStderr := Core.stderrAsMessages.get (← getOptions)) do
-      let tid ← IO.getTID
-      -- reset trace state and message log so as not to report them twice
-      modify ({ · with messages := {}, traceState := { tid } })
-      try
-        withTraceNode `Elab.async (fun _ => return desc) do
-          act ()
-      catch e =>
-        logError e.toMessageData
-      finally
-        addTraceAsMessages
-      get
-  let ctx ← read
-  return do
-    match (← t.toBaseIO) with
-    | .ok (output, st) =>
-      let mut msgs := st.messages
-      if !output.isEmpty then
-        msgs := msgs.add {
-          fileName := ctx.fileName
-          severity := MessageSeverity.information
-          pos      := ctx.fileMap.toPosition <| ctx.ref.getPos?.getD 0
-          data     := output
-        }
-      return .mk {
-        desc
-        diagnostics := (← Language.Snapshot.Diagnostics.ofMessageLog msgs)
-        traces := st.traceState
-      } st.snapshotTasks
-    -- interrupt or abort exception as `try catch` above should have caught any others
-    | .error _ => default
-
-@[inherit_doc Core.logSnapshotTask]
-def logSnapshotTask (task : Language.SnapshotTask Language.SnapshotTree) : CommandElabM Unit :=
-  modify fun s => { s with snapshotTasks := s.snapshotTasks.push task }
-
 protected def getCurrMacroScope : CommandElabM Nat  := do pure (← read).currMacroScope
 protected def getMainModule     : CommandElabM Name := do pure (← getEnv).mainModule
 
@@ -554,6 +532,12 @@ def elabCommandTopLevel (stx : Syntax) : CommandElabM Unit := withRef stx do pro
     let mut msgs := (← get).messages
     for tree in (← getInfoTrees) do
       trace[Elab.info] (← tree.format)
+    if (← isTracingEnabledFor `Elab.snapshotTree) then
+      if let some snap := (← read).snap? then
+        -- We can assume that the root command snapshot is not involved in parallelism yet, so this
+        -- should be true iff the command supports incrementality
+        if (← IO.hasFinished snap.new.result) then
+          liftCoreM <| Language.ToSnapshotTree.toSnapshotTree snap.new.result.get |>.trace
     modify fun st => { st with
       messages := initMsgs ++ msgs
       infoState := { st.infoState with trees := initInfoTrees ++ st.infoState.trees }
@@ -684,6 +668,14 @@ def runTermElabM (elabFn : Array Expr → TermElabM α) : CommandElabM α := do
           Term.addAutoBoundImplicits' xs someType fun xs _ =>
             Term.withoutAutoBoundImplicit <| elabFn xs
 
+/--
+Catches and logs exceptions occurring in `x`. Unlike `try catch` in `CommandElabM`, this function
+catches interrupt exceptions as well and thus is intended for use at the top level of elaboration.
+Interrupt and abort exceptions are caught but not logged.
+-/
+@[inline] def withLoggingExceptions (x : CommandElabM Unit) : CommandElabCoreM Empty Unit := fun ctx ref =>
+  EIO.catchExceptions (withLogging x ctx ref) (fun _ => pure ())
+
 private def liftAttrM {α} (x : AttrM α) : CommandElabM α := do
   liftCoreM x
 

src/Lean/Elab/Declaration.lean

@@ -7,8 +7,9 @@ prelude
 import Lean.Util.CollectLevelParams
 import Lean.Elab.DeclUtil
 import Lean.Elab.DefView
+import Lean.Elab.Inductive
+import Lean.Elab.Structure
 import Lean.Elab.MutualDef
-import Lean.Elab.MutualInductive
 import Lean.Elab.DeclarationRange
 namespace Lean.Elab.Command
 
@@ -162,11 +163,15 @@ def elabDeclaration : CommandElab := fun stx => do
     if declKind == ``Lean.Parser.Command.«axiom» then
       let modifiers ← elabModifiers modifiers
       elabAxiom modifiers decl
-    else if declKind == ``Lean.Parser.Command.«inductive»
-        || declKind == ``Lean.Parser.Command.classInductive
-        || declKind == ``Lean.Parser.Command.«structure» then
+    else if declKind == ``Lean.Parser.Command.«inductive» then
       let modifiers ← elabModifiers modifiers
       elabInductive modifiers decl
+    else if declKind == ``Lean.Parser.Command.classInductive then
+      let modifiers ← elabModifiers modifiers
+      elabClassInductive modifiers decl
+    else if declKind == ``Lean.Parser.Command.«structure» then
+      let modifiers ← elabModifiers modifiers
+      elabStructure modifiers decl
     else
       throwError "unexpected declaration"
 
@@ -273,10 +278,10 @@ def elabMutual : CommandElab := fun stx => do
     -- only case implementing incrementality currently
     elabMutualDef stx[1].getArgs
   else withoutCommandIncrementality true do
-    if ← isMutualInductive stx then
+    if isMutualInductive stx then
       elabMutualInductive stx[1].getArgs
     else
-      throwError "invalid mutual block: either all elements of the block must be inductive/structure declarations, or they must all be definitions/theorems/abbrevs"
+      throwError "invalid mutual block: either all elements of the block must be inductive declarations, or they must all be definitions/theorems/abbrevs"
 
 /- leading_parser "attribute " >> "[" >> sepBy1 (eraseAttr <|> Term.attrInstance) ", " >> "]" >> many1 ident -/
 @[builtin_command_elab «attribute»] def elabAttr : CommandElab := fun stx => do

src/Lean/Elab/Inductive.lean

@@ -1,36 +1,102 @@
 /-
 Copyright (c) 2020 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura, Kyle Miller
+Authors: Leonardo de Moura
 -/
 prelude
-import Lean.Elab.MutualInductive
+import Lean.Util.ForEachExprWhere
+import Lean.Util.ReplaceLevel
+import Lean.Util.ReplaceExpr
+import Lean.Util.CollectLevelParams
+import Lean.Meta.Constructions
+import Lean.Meta.CollectFVars
+import Lean.Meta.SizeOf
+import Lean.Meta.Injective
+import Lean.Meta.IndPredBelow
+import Lean.Elab.Command
+import Lean.Elab.ComputedFields
+import Lean.Elab.DefView
+import Lean.Elab.DeclUtil
+import Lean.Elab.Deriving.Basic
+import Lean.Elab.DeclarationRange
 
 namespace Lean.Elab.Command
 open Meta
 
-/-
-```
-def Lean.Parser.Command.«inductive» :=
-  leading_parser "inductive " >> declId >> optDeclSig >> optional ("where" <|> ":=") >> many ctor
+builtin_initialize
+  registerTraceClass `Elab.inductive
 
-def Lean.Parser.Command.classInductive :=
-  leading_parser atomic (group ("class " >> "inductive ")) >> declId >> optDeclSig >> optional ("where" <|> ":=") >> many ctor >> optDeriving
-```
+register_builtin_option inductive.autoPromoteIndices : Bool := {
+    defValue := true
+    descr    := "Promote indices to parameters in inductive types whenever possible."
+  }
+
+def checkValidInductiveModifier [Monad m] [MonadError m] (modifiers : Modifiers) : m Unit := do
+  if modifiers.isNoncomputable then
+    throwError "invalid use of 'noncomputable' in inductive declaration"
+  if modifiers.isPartial then
+    throwError "invalid use of 'partial' in inductive declaration"
+
+def checkValidCtorModifier [Monad m] [MonadError m] (modifiers : Modifiers) : m Unit := do
+  if modifiers.isNoncomputable then
+    throwError "invalid use of 'noncomputable' in constructor declaration"
+  if modifiers.isPartial then
+    throwError "invalid use of 'partial' in constructor declaration"
+  if modifiers.isUnsafe then
+    throwError "invalid use of 'unsafe' in constructor declaration"
+  if modifiers.attrs.size != 0 then
+    throwError "invalid use of attributes in constructor declaration"
+
+structure CtorView where
+  ref       : Syntax
+  modifiers : Modifiers
+  declName  : Name
+  binders   : Syntax
+  type?     : Option Syntax
+  deriving Inhabited
+
+structure ComputedFieldView where
+  ref       : Syntax
+  modifiers : Syntax
+  fieldId   : Name
+  type      : Syntax.Term
+  matchAlts : TSyntax ``Parser.Term.matchAlts
+
+structure InductiveView where
+  ref             : Syntax
+  declId          : Syntax
+  modifiers       : Modifiers
+  shortDeclName   : Name
+  declName        : Name
+  levelNames      : List Name
+  binders         : Syntax
+  type?           : Option Syntax
+  ctors           : Array CtorView
+  derivingClasses : Array DerivingClassView
+  computedFields  : Array ComputedFieldView
+  deriving Inhabited
+
+structure ElabHeaderResult where
+  view       : InductiveView
+  lctx       : LocalContext
+  localInsts : LocalInstances
+  levelNames : List Name
+  params     : Array Expr
+  type       : Expr
+  deriving Inhabited
+
+/-
+leading_parser "inductive " >> declId >> optDeclSig >> optional ("where" <|> ":=") >> many ctor
+leading_parser atomic (group ("class " >> "inductive ")) >> declId >> optDeclSig >> optional ("where" <|> ":=") >> many ctor >> optDeriving
 -/
 private def inductiveSyntaxToView (modifiers : Modifiers) (decl : Syntax) : TermElabM InductiveView := do
-  let isClass := decl.isOfKind ``Parser.Command.classInductive
-  let modifiers := if isClass then modifiers.addAttr { name := `class } else modifiers
+  checkValidInductiveModifier modifiers
   let (binders, type?) := expandOptDeclSig decl[2]
   let declId           := decl[1]
   let ⟨name, declName, levelNames⟩ ← Term.expandDeclId (← getCurrNamespace) (← Term.getLevelNames) declId modifiers
   addDeclarationRangesForBuiltin declName modifiers.stx decl
   let ctors      ← decl[4].getArgs.mapM fun ctor => withRef ctor do
-    /-
-    ```
-    def ctor := leading_parser optional docComment >> "\n| " >> declModifiers >> rawIdent >> optDeclSig
-    ```
-    -/
+    -- def ctor := leading_parser optional docComment >> "\n| " >> declModifiers >> rawIdent >> optDeclSig
     let mut ctorModifiers ← elabModifiers ⟨ctor[2]⟩
     if let some leadingDocComment := ctor[0].getOptional? then
       if ctorModifiers.docString?.isSome then
@@ -47,7 +113,7 @@ private def inductiveSyntaxToView (modifiers : Modifiers) (decl : Syntax) : Term
     let (binders, type?) := expandOptDeclSig ctor[4]
     addDocString' ctorName ctorModifiers.docString?
     addDeclarationRangesFromSyntax ctorName ctor ctor[3]
-    return { ref := ctor, declId := ctor[3], modifiers := ctorModifiers, declName := ctorName, binders := binders, type? := type? : CtorView }
+    return { ref := ctor, modifiers := ctorModifiers, declName := ctorName, binders := binders, type? := type? : CtorView }
   let computedFields ← (decl[5].getOptional?.map (·[1].getArgs) |>.getD #[]).mapM fun cf => withRef cf do
     return { ref := cf, modifiers := cf[0], fieldId := cf[1].getId, type := ⟨cf[3]⟩, matchAlts := ⟨cf[4]⟩ }
   let classes ← getOptDerivingClasses decl[6]
@@ -59,13 +125,137 @@ private def inductiveSyntaxToView (modifiers : Modifiers) (decl : Syntax) : Term
     ref             := decl
     shortDeclName   := name
     derivingClasses := classes
-    allowIndices    := true
-    allowSortPolymorphism := true
-    declId, modifiers, isClass, declName, levelNames
+    declId, modifiers, declName, levelNames
     binders, type?, ctors
     computedFields
   }
 
+private partial def elabHeaderAux (views : Array InductiveView) (i : Nat) (acc : Array ElabHeaderResult) : TermElabM (Array ElabHeaderResult) :=
+  Term.withAutoBoundImplicitForbiddenPred (fun n => views.any (·.shortDeclName == n)) do
+    if h : i < views.size then
+      let view := views[i]
+      let acc ← Term.withAutoBoundImplicit <| Term.elabBinders view.binders.getArgs fun params => do
+        match view.type? with
+        | none         =>
+          let u ← mkFreshLevelMVar
+          let type := mkSort u
+          Term.synthesizeSyntheticMVarsNoPostponing
+          Term.addAutoBoundImplicits' params type fun params type => do
+            let levelNames ← Term.getLevelNames
+            return acc.push { lctx := (← getLCtx), localInsts := (← getLocalInstances), levelNames, params, type, view }
+        | some typeStx =>
+          let (type, _) ← Term.withAutoBoundImplicit do
+            let type ← Term.elabType typeStx
+            unless (← isTypeFormerType type) do
+              throwErrorAt typeStx "invalid inductive type, resultant type is not a sort"
+            Term.synthesizeSyntheticMVarsNoPostponing
+            let indices ← Term.addAutoBoundImplicits #[]
+            return (← mkForallFVars indices type, indices.size)
+          Term.addAutoBoundImplicits' params type fun params type => do
+            trace[Elab.inductive] "header params: {params}, type: {type}"
+            let levelNames ← Term.getLevelNames
+            return acc.push { lctx := (← getLCtx), localInsts := (← getLocalInstances), levelNames, params, type, view }
+      elabHeaderAux views (i+1) acc
+    else
+      return acc
+
+private def checkNumParams (rs : Array ElabHeaderResult) : TermElabM Nat := do
+  let numParams := rs[0]!.params.size
+  for r in rs do
+    unless r.params.size == numParams do
+      throwErrorAt r.view.ref "invalid inductive type, number of parameters mismatch in mutually inductive datatypes"
+  return numParams
+
+private def checkUnsafe (rs : Array ElabHeaderResult) : TermElabM Unit := do
+  let isUnsafe := rs[0]!.view.modifiers.isUnsafe
+  for r in rs do
+    unless r.view.modifiers.isUnsafe == isUnsafe do
+      throwErrorAt r.view.ref "invalid inductive type, cannot mix unsafe and safe declarations in a mutually inductive datatypes"
+
+private def InductiveView.checkLevelNames (views : Array InductiveView) : TermElabM Unit := do
+  if h : views.size > 1 then
+    let levelNames := views[0].levelNames
+    for view in views do
+      unless view.levelNames == levelNames do
+        throwErrorAt view.ref "invalid inductive type, universe parameters mismatch in mutually inductive datatypes"
+
+private def ElabHeaderResult.checkLevelNames (rs : Array ElabHeaderResult) : TermElabM Unit := do
+  if h : rs.size > 1 then
+    let levelNames := rs[0].levelNames
+    for r in rs do
+      unless r.levelNames == levelNames do
+        throwErrorAt r.view.ref "invalid inductive type, universe parameters mismatch in mutually inductive datatypes"
+
+private def mkTypeFor (r : ElabHeaderResult) : TermElabM Expr := do
+  withLCtx r.lctx r.localInsts do
+    mkForallFVars r.params r.type
+
+private def throwUnexpectedInductiveType : TermElabM α :=
+  throwError "unexpected inductive resulting type"
+
+private def eqvFirstTypeResult (firstType type : Expr) : MetaM Bool :=
+  forallTelescopeReducing firstType fun _ firstTypeResult => isDefEq firstTypeResult type
+
+-- Auxiliary function for checking whether the types in mutually inductive declaration are compatible.
+private partial def checkParamsAndResultType (type firstType : Expr) (numParams : Nat) : TermElabM Unit := do
+  try
+    forallTelescopeCompatible type firstType numParams fun _ type firstType =>
+    forallTelescopeReducing type fun _ type =>
+    forallTelescopeReducing firstType fun _ firstType => do
+      let type ← whnfD type
+      match type with
+      | .sort .. =>
+        unless (← isDefEq firstType type) do
+          throwError "resulting universe mismatch, given{indentExpr type}\nexpected type{indentExpr firstType}"
+      | _ =>
+        throwError "unexpected inductive resulting type"
+  catch
+    | Exception.error ref msg => throw (Exception.error ref m!"invalid mutually inductive types, {msg}")
+    | ex => throw ex
+
+-- Auxiliary function for checking whether the types in mutually inductive declaration are compatible.
+private def checkHeader (r : ElabHeaderResult) (numParams : Nat) (firstType? : Option Expr) : TermElabM Expr := do
+  let type ← mkTypeFor r
+  match firstType? with
+  | none           => return type
+  | some firstType =>
+    withRef r.view.ref <| checkParamsAndResultType type firstType numParams
+    return firstType
+
+-- Auxiliary function for checking whether the types in mutually inductive declaration are compatible.
+private partial def checkHeaders (rs : Array ElabHeaderResult) (numParams : Nat) (i : Nat) (firstType? : Option Expr) : TermElabM Unit := do
+  if h : i < rs.size then
+    let type ← checkHeader rs[i] numParams firstType?
+    checkHeaders rs numParams (i+1) type
+
+private def elabHeader (views : Array InductiveView) : TermElabM (Array ElabHeaderResult) := do
+  let rs ← elabHeaderAux views 0 #[]
+  if rs.size > 1 then
+    checkUnsafe rs
+    let numParams ← checkNumParams rs
+    checkHeaders rs numParams 0 none
+  return rs
+
+/-- Create a local declaration for each inductive type in `rs`, and execute `x params indFVars`, where `params` are the inductive type parameters and
+   `indFVars` are the new local declarations.
+   We use the local context/instances and parameters of rs[0].
+   Note that this method is executed after we executed `checkHeaders` and established all
+   parameters are compatible. -/
+private partial def withInductiveLocalDecls (rs : Array ElabHeaderResult) (x : Array Expr → Array Expr → TermElabM α) : TermElabM α := do
+  let namesAndTypes ← rs.mapM fun r => do
+    let type ← mkTypeFor r
+    pure (r.view.declName, r.view.shortDeclName, type)
+  let r0     := rs[0]!
+  let params := r0.params
+  withLCtx r0.lctx r0.localInsts <| withRef r0.view.ref do
+    let rec loop (i : Nat) (indFVars : Array Expr) := do
+      if h : i < namesAndTypes.size then
+        let (declName, shortDeclName, type) := namesAndTypes[i]
+        Term.withAuxDecl shortDeclName type declName fun indFVar => loop (i+1) (indFVars.push indFVar)
+      else
+        x params indFVars
+    loop 0 #[]
+
 private def isInductiveFamily (numParams : Nat) (indFVar : Expr) : TermElabM Bool := do
   let indFVarType ← inferType indFVar
   forallTelescopeReducing indFVarType fun xs _ =>
@@ -81,8 +271,8 @@ where
     | _ => acc
 
 /--
-Replaces binder names in `type` with `newNames`.
-Remark: we only replace the names for binder containing macroscopes.
+  Replace binder names in `type` with `newNames`.
+  Remark: we only replace the names for binder containing macroscopes.
 -/
 private def replaceArrowBinderNames (type : Expr) (newNames : Array Name) : Expr :=
   go type 0
@@ -100,20 +290,20 @@ where
       type
 
 /--
-Reorders constructor arguments to improve the effectiveness of the `fixedIndicesToParams` method.
+  Reorder constructor arguments to improve the effectiveness of the `fixedIndicesToParams` method.
 
-The idea is quite simple. Given a constructor type of the form
-```
-(a₁ : A₁) → ... → (aₙ : Aₙ) → C b₁ ... bₘ
-```
-We try to find the longest prefix `b₁ ... bᵢ`, `i ≤ m` s.t.
-- each `bₖ` is in `{a₁, ..., aₙ}`
-- each `bₖ` only depends on variables in `{b₁, ..., bₖ₋₁}`
+  The idea is quite simple. Given a constructor type of the form
+  ```
+  (a₁ : A₁) → ... → (aₙ : Aₙ) → C b₁ ... bₘ
+  ```
+  We try to find the longest prefix `b₁ ... bᵢ`, `i ≤ m` s.t.
+  - each `bₖ` is in `{a₁, ..., aₙ}`
+  - each `bₖ` only depends on variables in `{b₁, ..., bₖ₋₁}`
 
-Then, it moves this prefix `b₁ ... bᵢ` to the front.
+  Then, it moves this prefix `b₁ ... bᵢ` to the front.
 
-Remark: We only reorder implicit arguments that have macroscopes. See issue #1156.
-The macroscope test is an approximation, we could have restricted ourselves to auto-implicit arguments.
+  Remark: We only reorder implicit arguments that have macroscopes. See issue #1156.
+  The macroscope test is an approximation, we could have restricted ourselves to auto-implicit arguments.
 -/
 private def reorderCtorArgs (ctorType : Expr) : MetaM Expr := do
   forallTelescopeReducing ctorType fun as type => do
@@ -158,6 +348,16 @@ private def reorderCtorArgs (ctorType : Expr) : MetaM Expr := do
       let binderNames := getArrowBinderNames (← instantiateMVars (← inferType C))
       return replaceArrowBinderNames r binderNames[:bsPrefix.size]
 
+/--
+  Execute `k` with updated binder information for `xs`. Any `x` that is explicit becomes implicit.
+-/
+private def withExplicitToImplicit (xs : Array Expr) (k : TermElabM α) : TermElabM α := do
+  let mut toImplicit := #[]
+  for x in xs do
+    if (← getFVarLocalDecl x).binderInfo.isExplicit then
+      toImplicit := toImplicit.push (x.fvarId!, BinderInfo.implicit)
+  withNewBinderInfos toImplicit k
+
 /--
   Elaborate constructor types.
 
@@ -166,20 +366,17 @@ private def reorderCtorArgs (ctorType : Expr) : MetaM Expr := do
   - Positivity (it is a rare failure, and the kernel already checks for it).
   - Universe constraints (the kernel checks for it).
 -/
-private def elabCtors (indFVars : Array Expr) (params : Array Expr) (r : ElabHeaderResult) : TermElabM (List Constructor) :=
-  withRef r.view.ref do
-  withExplicitToImplicit params do
-  let indFVar := r.indFVar
+private def elabCtors (indFVars : Array Expr) (indFVar : Expr) (params : Array Expr) (r : ElabHeaderResult) : TermElabM (List Constructor) := withRef r.view.ref do
   let indFamily ← isInductiveFamily params.size indFVar
   r.view.ctors.toList.mapM fun ctorView =>
     Term.withAutoBoundImplicit <| Term.elabBinders ctorView.binders.getArgs fun ctorParams =>
       withRef ctorView.ref do
-        let elabCtorType : TermElabM Expr := do
+        let rec elabCtorType (k : Expr → TermElabM Constructor) : TermElabM Constructor := do
           match ctorView.type? with
           | none          =>
             if indFamily then
               throwError "constructor resulting type must be specified in inductive family declaration"
-            return mkAppN indFVar params
+            k <| mkAppN indFVar params
           | some ctorType =>
             let type ← Term.elabType ctorType
             trace[Elab.inductive] "elabType {ctorView.declName} : {type} "
@@ -191,43 +388,43 @@ private def elabCtors (indFVars : Array Expr) (params : Array Expr) (r : ElabHea
                 throwError "unexpected constructor resulting type{indentExpr resultingType}"
               unless (← isType resultingType) do
                 throwError "unexpected constructor resulting type, type expected{indentExpr resultingType}"
-            return type
-        let type ← elabCtorType
-        Term.synthesizeSyntheticMVarsNoPostponing
-        let ctorParams ← Term.addAutoBoundImplicits ctorParams
-        let except (mvarId : MVarId) := ctorParams.any fun ctorParam => ctorParam.isMVar && ctorParam.mvarId! == mvarId
-        /-
-          We convert metavariables in the resulting type into extra parameters. Otherwise, we would not be able to elaborate
-          declarations such as
-          ```
-          inductive Palindrome : List α → Prop where
-            | nil      : Palindrome [] -- We would get an error here saying "failed to synthesize implicit argument" at `@List.nil ?m`
-            | single   : (a : α) → Palindrome [a]
-            | sandwich : (a : α) → Palindrome as → Palindrome ([a] ++ as ++ [a])
-          ```
-          We used to also collect unassigned metavariables on `ctorParams`, but it produced counterintuitive behavior.
-          For example, the following declaration used to be accepted.
-          ```
-          inductive Foo
-          | bar (x)
+            k type
+        elabCtorType fun type => do
+          Term.synthesizeSyntheticMVarsNoPostponing
+          let ctorParams ← Term.addAutoBoundImplicits ctorParams
+          let except (mvarId : MVarId) := ctorParams.any fun ctorParam => ctorParam.isMVar && ctorParam.mvarId! == mvarId
+          /-
+            We convert metavariables in the resulting type info extra parameters. Otherwise, we would not be able to elaborate
+            declarations such as
+            ```
+            inductive Palindrome : List α → Prop where
+              | nil      : Palindrome [] -- We would get an error here saying "failed to synthesize implicit argument" at `@List.nil ?m`
+              | single   : (a : α) → Palindrome [a]
+              | sandwich : (a : α) → Palindrome as → Palindrome ([a] ++ as ++ [a])
+            ```
+            We used to also collect unassigned metavariables on `ctorParams`, but it produced counterintuitive behavior.
+            For example, the following declaration used to be accepted.
+            ```
+            inductive Foo
+            | bar (x)
 
-          #check Foo.bar
-          -- @Foo.bar : {x : Sort u_1} → x → Foo
-          ```
-          which is also inconsistent with the behavior of auto implicits in definitions. For example, the following example was never accepted.
-          ```
-          def bar (x) := 1
-          ```
-        -/
-        let extraCtorParams ← Term.collectUnassignedMVars (← instantiateMVars type) #[] except
-        trace[Elab.inductive] "extraCtorParams: {extraCtorParams}"
-        /- We must abstract `extraCtorParams` and `ctorParams` simultaneously to make
-            sure we do not create auxiliary metavariables. -/
-        let type ← mkForallFVars (extraCtorParams ++ ctorParams) type
-        let type ← reorderCtorArgs type
-        let type ← mkForallFVars params type
-        trace[Elab.inductive] "{ctorView.declName} : {type}"
-        return { name := ctorView.declName, type }
+            #check Foo.bar
+            -- @Foo.bar : {x : Sort u_1} → x → Foo
+            ```
+            which is also inconsistent with the behavior of auto implicits in definitions. For example, the following example was never accepted.
+            ```
+            def bar (x) := 1
+            ```
+          -/
+          let extraCtorParams ← Term.collectUnassignedMVars (← instantiateMVars type) #[] except
+          trace[Elab.inductive] "extraCtorParams: {extraCtorParams}"
+          /- We must abstract `extraCtorParams` and `ctorParams` simultaneously to make
+             sure we do not create auxiliary metavariables. -/
+          let type  ← mkForallFVars (extraCtorParams ++ ctorParams) type
+          let type ← reorderCtorArgs type
+          let type ← mkForallFVars params type
+          trace[Elab.inductive] "{ctorView.declName} : {type}"
+          return { name := ctorView.declName, type }
 where
   checkParamOccs (ctorType : Expr) : MetaM Expr :=
     let visit (e : Expr) : MetaM TransformStep := do
@@ -247,15 +444,555 @@ where
         return .continue
     transform ctorType (pre := visit)
 
-@[builtin_inductive_elab Lean.Parser.Command.inductive, builtin_inductive_elab Lean.Parser.Command.classInductive]
-def elabInductiveCommand : InductiveElabDescr where
-  mkInductiveView (modifiers : Modifiers) (stx : Syntax) := do
-    let view ← inductiveSyntaxToView modifiers stx
-    return {
-      view
-      elabCtors := fun rs r params => do
-        let ctors ← elabCtors (rs.map (·.indFVar)) params r
-        return { ctors }
-    }
+private def getResultingUniverse : List InductiveType → TermElabM Level
+  | []           => throwError "unexpected empty inductive declaration"
+  | indType :: _ => forallTelescopeReducing indType.type fun _ r => do
+    let r ← whnfD r
+    match r with
+    | Expr.sort u => return u
+    | _           => throwError "unexpected inductive type resulting type{indentExpr r}"
+
+/--
+  Return `some ?m` if `u` is of the form `?m + k`.
+  Return none if `u` does not contain universe metavariables.
+  Throw exception otherwise. -/
+def shouldInferResultUniverse (u : Level) : TermElabM (Option LMVarId) := do
+  let u ← instantiateLevelMVars u
+  if u.hasMVar then
+    match u.getLevelOffset with
+    | Level.mvar mvarId => return some mvarId
+    | _ =>
+      throwError "cannot infer resulting universe level of inductive datatype, given level contains metavariables {mkSort u}, provide universe explicitly"
+  else
+    return none
+
+/--
+  Convert universe metavariables into new parameters. It skips `univToInfer?` (the inductive datatype resulting universe) because
+  it should be inferred later using `inferResultingUniverse`.
+-/
+private def levelMVarToParam (indTypes : List InductiveType) (univToInfer? : Option LMVarId) : TermElabM (List InductiveType) :=
+  indTypes.mapM fun indType => do
+    let type  ← levelMVarToParam' indType.type
+    let ctors ← indType.ctors.mapM fun ctor => do
+      let ctorType ← levelMVarToParam' ctor.type
+      return { ctor with type := ctorType }
+    return { indType with ctors, type }
+where
+  levelMVarToParam' (type : Expr) : TermElabM Expr := do
+    Term.levelMVarToParam type (except := fun mvarId => univToInfer? == some mvarId)
+
+def mkResultUniverse (us : Array Level) (rOffset : Nat) (preferProp : Bool) : Level :=
+  if us.isEmpty && rOffset == 0 then
+    if preferProp then levelZero else levelOne
+  else
+    let r := Level.mkNaryMax us.toList
+    if rOffset == 0 && !r.isZero && !r.isNeverZero then
+      mkLevelMax r levelOne |>.normalize
+    else
+      r.normalize
+
+ /--
+   Auxiliary function for `updateResultingUniverse`
+   `accLevel u r rOffset` add `u` to state if it is not already there and
+   it is different from the resulting universe level `r+rOffset`.
+
+
+   If `u` is a `max`, then its components are recursively processed.
+   If `u` is a `succ` and `rOffset > 0`, we process the `u`s child using `rOffset-1`.
+
+   This method is used to infer the resulting universe level of an inductive datatype.
+ -/
+def accLevel (u : Level) (r : Level) (rOffset : Nat) : OptionT (StateT (Array Level) Id) Unit := do
+  go u rOffset
+where
+  go (u : Level) (rOffset : Nat) : OptionT (StateT (Array Level) Id) Unit := do
+    match u, rOffset with
+    | .max u v,  rOffset   => go u rOffset; go v rOffset
+    | .imax u v, rOffset   => go u rOffset; go v rOffset
+    | .zero,     _         => return ()
+    | .succ u,   rOffset+1 => go u rOffset
+    | u,         rOffset   =>
+      if rOffset == 0 && u == r then
+        return ()
+      else if r.occurs u  then
+        failure
+      else if rOffset > 0 then
+        failure
+      else if (← get).contains u then
+        return ()
+      else
+        modify fun us => us.push u
+
+/--
+  Auxiliary function for `updateResultingUniverse`
+  `accLevelAtCtor ctor ctorParam r rOffset` add `u` (`ctorParam`'s universe) to state if it is not already there and
+  it is different from the resulting universe level `r+rOffset`.
+
+  See `accLevel`.
+-/
+def accLevelAtCtor (ctor : Constructor) (ctorParam : Expr) (r : Level) (rOffset : Nat) : StateRefT (Array Level) TermElabM Unit := do
+  let type ← inferType ctorParam
+  let u ← instantiateLevelMVars (← getLevel type)
+  match (← modifyGet fun s => accLevel u r rOffset |>.run |>.run s) with
+  | some _ => pure ()
+  | none =>
+    let typeType ← inferType type
+    let mut msg := m!"failed to compute resulting universe level of inductive datatype, constructor '{ctor.name}' has type{indentExpr ctor.type}\nparameter"
+    let localDecl ← getFVarLocalDecl ctorParam
+    unless localDecl.userName.hasMacroScopes do
+      msg := msg ++ m!" '{ctorParam}'"
+    msg := msg ++ m!" has type{indentD m!"{type} : {typeType}"}\ninductive type resulting type{indentExpr (mkSort (r.addOffset rOffset))}"
+    if r.isMVar then
+      msg := msg ++ "\nrecall that Lean only infers the resulting universe level automatically when there is a unique solution for the universe level constraints, consider explicitly providing the inductive type resulting universe level"
+    throwError msg
+
+/--
+  Execute `k` using the `Syntax` reference associated with constructor `ctorName`.
+-/
+def withCtorRef [Monad m] [MonadRef m] (views : Array InductiveView) (ctorName : Name) (k : m α) : m α := do
+  for view in views do
+    for ctorView in view.ctors do
+      if ctorView.declName == ctorName then
+        return (← withRef ctorView.ref k)
+  k
+
+/-- Auxiliary function for `updateResultingUniverse` -/
+private partial def collectUniverses (views : Array InductiveView) (r : Level) (rOffset : Nat) (numParams : Nat) (indTypes : List InductiveType) : TermElabM (Array Level) := do
+  let (_, us) ← go |>.run #[]
+  return us
+where
+  go : StateRefT (Array Level) TermElabM Unit :=
+    indTypes.forM fun indType => indType.ctors.forM fun ctor =>
+      withCtorRef views ctor.name do
+        forallTelescopeReducing ctor.type fun ctorParams _ =>
+          for ctorParam in ctorParams[numParams:] do
+            accLevelAtCtor ctor ctorParam r rOffset
+
+/--
+Decides whether the inductive type should be `Prop`-valued when the universe is not given
+and when the universe inference algorithm `collectUniverses` determines
+that the inductive type could naturally be `Prop`-valued.
+Recall: the natural universe level is the mimimum universe level for all the types of all the constructor parameters.
+
+Heuristic:
+- We want `Prop` when each inductive type is a syntactic subsingleton.
+  That's to say, when each inductive type has at most one constructor.
+  Such types carry no data anyway.
+- Exception: if no inductive type has any constructors, these are likely stubbed-out declarations,
+  so we prefer `Type` instead.
+- Exception: if each constructor has no parameters, then these are likely partially-written enumerations,
+  so we prefer `Type` instead.
+-/
+private def isPropCandidate (numParams : Nat) (indTypes : List InductiveType) : MetaM Bool := do
+  unless indTypes.foldl (fun n indType => max n indType.ctors.length) 0 == 1 do
+    return false
+  for indType in indTypes do
+    for ctor in indType.ctors do
+      let cparams ← forallTelescopeReducing ctor.type fun ctorParams _ => pure (ctorParams.size - numParams)
+      unless cparams == 0 do
+        return true
+  return false
+
+private def updateResultingUniverse (views : Array InductiveView) (numParams : Nat) (indTypes : List InductiveType) : TermElabM (List InductiveType) := do
+  let r ← getResultingUniverse indTypes
+  let rOffset : Nat   := r.getOffset
+  let r       : Level := r.getLevelOffset
+  unless r.isMVar do
+    throwError "failed to compute resulting universe level of inductive datatype, provide universe explicitly: {r}"
+  let us ← collectUniverses views r rOffset numParams indTypes
+  trace[Elab.inductive] "updateResultingUniverse us: {us}, r: {r}, rOffset: {rOffset}"
+  let rNew := mkResultUniverse us rOffset (← isPropCandidate numParams indTypes)
+  assignLevelMVar r.mvarId! rNew
+  indTypes.mapM fun indType => do
+    let type ← instantiateMVars indType.type
+    let ctors ← indType.ctors.mapM fun ctor => return { ctor with type := (← instantiateMVars ctor.type) }
+    return { indType with type, ctors }
+
+register_builtin_option bootstrap.inductiveCheckResultingUniverse : Bool := {
+    defValue := true,
+    group    := "bootstrap",
+    descr    := "by default the `inductive`/`structure` commands report an error if the resulting universe is not zero, but may be zero for some universe parameters. Reason: unless this type is a subsingleton, it is hardly what the user wants since it can only eliminate into `Prop`. In the `Init` package, we define subsingletons, and we use this option to disable the check. This option may be deleted in the future after we improve the validator"
+}
+
+def checkResultingUniverse (u : Level) : TermElabM Unit := do
+  if bootstrap.inductiveCheckResultingUniverse.get (← getOptions) then
+    let u ← instantiateLevelMVars u
+    if !u.isZero && !u.isNeverZero then
+      throwError "invalid universe polymorphic type, the resultant universe is not Prop (i.e., 0), but it may be Prop for some parameter values (solution: use 'u+1' or 'max 1 u'){indentD u}"
+
+private def checkResultingUniverses (views : Array InductiveView) (numParams : Nat) (indTypes : List InductiveType) : TermElabM Unit := do
+  let u := (← instantiateLevelMVars (← getResultingUniverse indTypes)).normalize
+  checkResultingUniverse u
+  unless u.isZero do
+    indTypes.forM fun indType => indType.ctors.forM fun ctor =>
+      forallTelescopeReducing ctor.type fun ctorArgs _ => do
+        for ctorArg in ctorArgs[numParams:] do
+          let type ← inferType ctorArg
+          let v := (← instantiateLevelMVars (← getLevel type)).normalize
+          let rec check (v' : Level) (u' : Level) : TermElabM Unit :=
+            match v', u' with
+            | .succ v', .succ u' => check v' u'
+            | .mvar id, .param ..  =>
+              /- Special case:
+                 The constructor parameter `v` is at unverse level `?v+k` and
+                 the resulting inductive universe level is `u'+k`, where `u'` is a parameter (or zero).
+                 Thus, `?v := u'` is the only choice for satisfying the universe constraint `?v+k <= u'+k`.
+                 Note that, we still generate an error for cases where there is more than one of satisfying the constraint.
+                 Examples:
+                 -----------------------------------------------------------
+                 | ctor universe level | inductive datatype universe level |
+                 -----------------------------------------------------------
+                 |   ?v                | max u w                           |
+                 -----------------------------------------------------------
+                 |   ?v                | u + 1                             |
+                 -----------------------------------------------------------
+              -/
+              assignLevelMVar id u'
+            | .mvar id, .zero => assignLevelMVar id u' -- TODO: merge with previous case
+            | _, _ =>
+              unless u.geq v do
+                let mut msg := m!"invalid universe level in constructor '{ctor.name}', parameter"
+                let localDecl ← getFVarLocalDecl ctorArg
+                unless localDecl.userName.hasMacroScopes do
+                  msg := msg ++ m!" '{ctorArg}'"
+                msg := msg ++ m!" has type{indentExpr type}"
+                msg := msg ++ m!"\nat universe level{indentD v}"
+                msg := msg ++ m!"\nit must be smaller than or equal to the inductive datatype universe level{indentD u}"
+                withCtorRef views ctor.name <| throwError msg
+          check v u
+
+private def collectUsed (indTypes : List InductiveType) : StateRefT CollectFVars.State MetaM Unit := do
+  indTypes.forM fun indType => do
+    indType.type.collectFVars
+    indType.ctors.forM fun ctor =>
+      ctor.type.collectFVars
+
+private def removeUnused (vars : Array Expr) (indTypes : List InductiveType) : TermElabM (LocalContext × LocalInstances × Array Expr) := do
+  let (_, used) ← (collectUsed indTypes).run {}
+  Meta.removeUnused vars used
+
+private def withUsed {α} (vars : Array Expr) (indTypes : List InductiveType) (k : Array Expr → TermElabM α) : TermElabM α := do
+  let (lctx, localInsts, vars) ← removeUnused vars indTypes
+  withLCtx lctx localInsts <| k vars
+
+private def updateParams (vars : Array Expr) (indTypes : List InductiveType) : TermElabM (List InductiveType) :=
+  indTypes.mapM fun indType => do
+    let type ← mkForallFVars vars indType.type
+    let ctors ← indType.ctors.mapM fun ctor => do
+      let ctorType ← withExplicitToImplicit vars (mkForallFVars vars ctor.type)
+      return { ctor with type := ctorType }
+    return { indType with type, ctors }
+
+private def collectLevelParamsInInductive (indTypes : List InductiveType) : Array Name := Id.run do
+  let mut usedParams : CollectLevelParams.State := {}
+  for indType in indTypes do
+    usedParams := collectLevelParams usedParams indType.type
+    for ctor in indType.ctors do
+      usedParams := collectLevelParams usedParams ctor.type
+  return usedParams.params
+
+private def mkIndFVar2Const (views : Array InductiveView) (indFVars : Array Expr) (levelNames : List Name) : ExprMap Expr := Id.run do
+  let levelParams := levelNames.map mkLevelParam;
+  let mut m : ExprMap Expr := {}
+  for h : i in [:views.size] do
+    let view    := views[i]
+    let indFVar := indFVars[i]!
+    m := m.insert indFVar (mkConst view.declName levelParams)
+  return m
+
+/-- Remark: `numVars <= numParams`. `numVars` is the number of context `variables` used in the inductive declaration,
+   and `numParams` is `numVars` + number of explicit parameters provided in the declaration. -/
+private def replaceIndFVarsWithConsts (views : Array InductiveView) (indFVars : Array Expr) (levelNames : List Name)
+    (numVars : Nat) (numParams : Nat) (indTypes : List InductiveType) : TermElabM (List InductiveType) :=
+  let indFVar2Const := mkIndFVar2Const views indFVars levelNames
+  indTypes.mapM fun indType => do
+    let ctors ← indType.ctors.mapM fun ctor => do
+      let type ← forallBoundedTelescope ctor.type numParams fun params type => do
+        let type := type.replace fun e =>
+          if !e.isFVar then
+            none
+          else match indFVar2Const[e]? with
+            | none   => none
+            | some c => mkAppN c (params.extract 0 numVars)
+        instantiateMVars (← mkForallFVars params type)
+      return { ctor with type }
+    return { indType with ctors }
+
+private def mkAuxConstructions (views : Array InductiveView) : TermElabM Unit := do
+  let env ← getEnv
+  let hasEq   := env.contains ``Eq
+  let hasHEq  := env.contains ``HEq
+  let hasUnit := env.contains ``PUnit
+  let hasProd := env.contains ``Prod
+  for view in views do
+    let n := view.declName
+    mkRecOn n
+    if hasUnit then mkCasesOn n
+    if hasUnit && hasEq && hasHEq then mkNoConfusion n
+    if hasUnit && hasProd then mkBelow n
+    if hasUnit && hasProd then mkIBelow n
+  for view in views do
+    let n := view.declName;
+    if hasUnit && hasProd then mkBRecOn n
+    if hasUnit && hasProd then mkBInductionOn n
+
+private def getArity (indType : InductiveType) : MetaM Nat :=
+  forallTelescopeReducing indType.type fun xs _ => return xs.size
+
+private def resetMaskAt (mask : Array Bool) (i : Nat) : Array Bool :=
+  mask.setD i false
+
+/--
+  Compute a bit-mask that for `indType`. The size of the resulting array `result` is the arity of `indType`.
+  The first `numParams` elements are `false` since they are parameters.
+  For `i ∈ [numParams, arity)`, we have that `result[i]` if this index of the inductive family is fixed.
+-/
+private def computeFixedIndexBitMask (numParams : Nat) (indType : InductiveType) (indFVars : Array Expr) : MetaM (Array Bool) := do
+  let arity ← getArity indType
+  if arity ≤ numParams then
+    return mkArray arity false
+  else
+    let maskRef ← IO.mkRef (mkArray numParams false ++ mkArray (arity - numParams) true)
+    let rec go (ctors : List Constructor) : MetaM (Array Bool) := do
+      match ctors with
+      | [] => maskRef.get
+      | ctor :: ctors =>
+        forallTelescopeReducing ctor.type fun xs type => do
+          let typeArgs := type.getAppArgs
+          for i in [numParams:arity] do
+            unless i < xs.size && xs[i]! == typeArgs[i]! do -- Remark: if we want to allow arguments to be rearranged, this test should be xs.contains typeArgs[i]
+              maskRef.modify fun mask => mask.set! i false
+          for x in xs[numParams:] do
+            let xType ← inferType x
+            let cond (e : Expr) := indFVars.any (fun indFVar => e.getAppFn == indFVar)
+            xType.forEachWhere (stopWhenVisited := true) cond fun e => do
+              let eArgs := e.getAppArgs
+              for i in [numParams:eArgs.size] do
+                if i >= typeArgs.size then
+                  maskRef.modify (resetMaskAt · i)
+                else
+                  unless eArgs[i]! == typeArgs[i]! do
+                    maskRef.modify (resetMaskAt · i)
+              /-If an index is missing in the arguments of the inductive type, then it must be non-fixed.
+                Consider the following example:
+                ```lean
+                inductive All {I : Type u} (P : I → Type v) : List I → Type (max u v) where
+                  | cons : P x → All P xs → All P (x :: xs)
+
+                inductive Iμ {I : Type u}  : I → Type (max u v) where
+                  | mk : (i : I)  → All Iμ [] → Iμ i
+                ```
+                because `i` doesn't appear in `All Iμ []`, the index shouldn't be fixed.
+              -/
+              for i in [eArgs.size:arity] do
+                maskRef.modify (resetMaskAt · i)
+        go ctors
+    go indType.ctors
+
+/-- Return true iff `arrowType` is an arrow and its domain is defeq to `type` -/
+private def isDomainDefEq (arrowType : Expr) (type : Expr) : MetaM Bool := do
+  if !arrowType.isForall then
+    return false
+  else
+    /-
+      We used to use `withNewMCtxDepth` to make sure we do not assign universe metavariables,
+      but it was not satisfactory. For example, in declarations such as
+      ```
+      inductive Eq : α → α → Prop where
+      | refl (a : α) : Eq a a
+      ```
+      We want the first two indices to be promoted to parameters, and this will only
+      happen if we can assign universe metavariables.
+    -/
+    isDefEq arrowType.bindingDomain! type
+
+/--
+  Convert fixed indices to parameters.
+-/
+private partial def fixedIndicesToParams (numParams : Nat) (indTypes : Array InductiveType) (indFVars : Array Expr) : MetaM Nat := do
+  if !inductive.autoPromoteIndices.get (← getOptions) then
+    return numParams
+  let masks ← indTypes.mapM (computeFixedIndexBitMask numParams · indFVars)
+  trace[Elab.inductive] "masks: {masks}"
+  if masks.all fun mask => !mask.contains true then
+    return numParams
+  -- We process just a non-fixed prefix of the indices for now. Reason: we don't want to change the order.
+  -- TODO: extend it in the future. For example, it should be reasonable to change
+  -- the order of indices generated by the auto implicit feature.
+  let mask := masks[0]!
+  forallBoundedTelescope indTypes[0]!.type numParams fun params type => do
+    let otherTypes ← indTypes[1:].toArray.mapM fun indType => do whnfD (← instantiateForall indType.type params)
+    let ctorTypes ← indTypes.toList.mapM fun indType => indType.ctors.mapM fun ctor => do whnfD (← instantiateForall ctor.type params)
+    let typesToCheck := otherTypes.toList ++ ctorTypes.flatten
+    let rec go (i : Nat) (type : Expr) (typesToCheck : List Expr) : MetaM Nat := do
+      if i < mask.size then
+        if !masks.all fun mask => i < mask.size && mask[i]! then
+           return i
+        if !type.isForall then
+          return i
+        let paramType := type.bindingDomain!
+        if !(← typesToCheck.allM fun type => isDomainDefEq type paramType) then
+          trace[Elab.inductive] "domain not def eq: {i}, {type} =?= {paramType}"
+          return i
+        withLocalDeclD `a paramType fun paramNew => do
+          let typesToCheck ← typesToCheck.mapM fun type => whnfD (type.bindingBody!.instantiate1 paramNew)
+          go (i+1) (type.bindingBody!.instantiate1 paramNew) typesToCheck
+      else
+        return i
+    go numParams type typesToCheck
+
+private def mkInductiveDecl (vars : Array Expr) (views : Array InductiveView) : TermElabM Unit := Term.withoutSavingRecAppSyntax do
+  let view0 := views[0]!
+  let scopeLevelNames ← Term.getLevelNames
+  InductiveView.checkLevelNames views
+  let allUserLevelNames := view0.levelNames
+  let isUnsafe          := view0.modifiers.isUnsafe
+  withRef view0.ref <| Term.withLevelNames allUserLevelNames do
+    let rs ← elabHeader views
+    Term.synthesizeSyntheticMVarsNoPostponing
+    ElabHeaderResult.checkLevelNames rs
+    let allUserLevelNames := rs[0]!.levelNames
+    trace[Elab.inductive] "level names: {allUserLevelNames}"
+    withInductiveLocalDecls rs fun params indFVars => do
+      trace[Elab.inductive] "indFVars: {indFVars}"
+      let mut indTypesArray := #[]
+      for h : i in [:views.size] do
+        let indFVar := indFVars[i]!
+        Term.addLocalVarInfo views[i].declId indFVar
+        let r     := rs[i]!
+        /- At this point, because of `withInductiveLocalDecls`, the only fvars that are in context are the ones related to the first inductive type.
+           Because of this, we need to replace the fvars present in each inductive type's header of the mutual block with those of the first inductive.
+           However, some mvars may still be uninstantiated there, and might hide some of the old fvars.
+           As such we first need to synthesize all possible mvars at this stage, instantiate them in the header types and only
+           then replace the parameters' fvars in the header type.
+
+           See issue #3242 (`https://github.com/leanprover/lean4/issues/3242`)
+        -/
+        let type  ←  instantiateMVars r.type
+        let type  := type.replaceFVars r.params params
+        let type  ← mkForallFVars params type
+        let ctors ← withExplicitToImplicit params (elabCtors indFVars indFVar params r)
+        indTypesArray := indTypesArray.push { name := r.view.declName, type, ctors }
+      let numExplicitParams ← fixedIndicesToParams params.size indTypesArray indFVars
+      trace[Elab.inductive] "numExplicitParams: {numExplicitParams}"
+      let indTypes := indTypesArray.toList
+      let u ← getResultingUniverse indTypes
+      let univToInfer? ← shouldInferResultUniverse u
+      withUsed vars indTypes fun vars => do
+        let numVars   := vars.size
+        let numParams := numVars + numExplicitParams
+        let indTypes ← updateParams vars indTypes
+        let indTypes ← if let some univToInfer := univToInfer? then
+          updateResultingUniverse views numParams (← levelMVarToParam indTypes univToInfer)
+        else
+          checkResultingUniverses views numParams indTypes
+          levelMVarToParam indTypes none
+        let usedLevelNames := collectLevelParamsInInductive indTypes
+        match sortDeclLevelParams scopeLevelNames allUserLevelNames usedLevelNames with
+        | .error msg      => throwError msg
+        | .ok levelParams => do
+          let indTypes ← replaceIndFVarsWithConsts views indFVars levelParams numVars numParams indTypes
+          let decl := Declaration.inductDecl levelParams numParams indTypes isUnsafe
+          Term.ensureNoUnassignedMVars decl
+          addDecl decl
+          mkAuxConstructions views
+    withSaveInfoContext do  -- save new env
+      for view in views do
+        Term.addTermInfo' view.ref[1] (← mkConstWithLevelParams view.declName) (isBinder := true)
+        for ctor in view.ctors do
+          Term.addTermInfo' ctor.ref[3] (← mkConstWithLevelParams ctor.declName) (isBinder := true)
+        -- We need to invoke `applyAttributes` because `class` is implemented as an attribute.
+        Term.applyAttributesAt view.declName view.modifiers.attrs .afterTypeChecking
+
+private def applyDerivingHandlers (views : Array InductiveView) : CommandElabM Unit := do
+  let mut processed : NameSet := {}
+  for view in views do
+    for classView in view.derivingClasses do
+      let className := classView.className
+      unless processed.contains className do
+        processed := processed.insert className
+        let mut declNames := #[]
+        for view in views do
+          if view.derivingClasses.any fun classView => classView.className == className then
+            declNames := declNames.push view.declName
+        classView.applyHandlers declNames
+
+private def applyComputedFields (indViews : Array InductiveView) : CommandElabM Unit := do
+  if indViews.all (·.computedFields.isEmpty) then return
+
+  let mut computedFields := #[]
+  let mut computedFieldDefs := #[]
+  for indView@{declName, ..} in indViews do
+    for {ref, fieldId, type, matchAlts, modifiers, ..} in indView.computedFields do
+      computedFieldDefs := computedFieldDefs.push <| ← do
+        let modifiers ← match modifiers with
+          | `(Lean.Parser.Command.declModifiersT| $[$doc:docComment]? $[$attrs:attributes]? $[$vis]? $[noncomputable]?) =>
+            `(Lean.Parser.Command.declModifiersT| $[$doc]? $[$attrs]? $[$vis]? noncomputable)
+          | _ => do
+            withRef modifiers do logError "unsupported modifiers for computed field"
+            `(Parser.Command.declModifiersT| noncomputable)
+        `($(⟨modifiers⟩):declModifiers
+          def%$ref $(mkIdent <| `_root_ ++ declName ++ fieldId):ident : $type $matchAlts:matchAlts)
+    let computedFieldNames := indView.computedFields.map fun {fieldId, ..} => declName ++ fieldId
+    computedFields := computedFields.push (declName, computedFieldNames)
+  withScope (fun scope => { scope with
+      opts := scope.opts
+        |>.setBool `bootstrap.genMatcherCode false
+        |>.setBool `elaboratingComputedFields true}) <|
+    elabCommand <| ← `(mutual $computedFieldDefs* end)
+
+  liftTermElabM do Term.withDeclName indViews[0]!.declName do
+    ComputedFields.setComputedFields computedFields
+
+def elabInductiveViews (vars : Array Expr) (views : Array InductiveView) : TermElabM Unit := do
+  let view0 := views[0]!
+  let ref := view0.ref
+  Term.withDeclName view0.declName do withRef ref do
+    mkInductiveDecl vars views
+    mkSizeOfInstances view0.declName
+    Lean.Meta.IndPredBelow.mkBelow view0.declName
+    for view in views do
+      mkInjectiveTheorems view.declName
+
+def elabInductiveViewsPostprocessing (views : Array InductiveView) : CommandElabM Unit := do
+  let view0 := views[0]!
+  let ref := view0.ref
+  applyComputedFields views -- NOTE: any generated code before this line is invalid
+  applyDerivingHandlers views
+  runTermElabM fun _ => Term.withDeclName view0.declName do withRef ref do
+    for view in views do
+      Term.applyAttributesAt view.declName view.modifiers.attrs .afterCompilation
+
+def elabInductives (inductives : Array (Modifiers × Syntax)) : CommandElabM Unit := do
+  let vs ← runTermElabM fun vars => do
+    let vs ← inductives.mapM fun (modifiers, stx) => inductiveSyntaxToView modifiers stx
+    elabInductiveViews vars vs
+    pure vs
+  elabInductiveViewsPostprocessing vs
+
+def elabInductive (modifiers : Modifiers) (stx : Syntax) : CommandElabM Unit := do
+  elabInductives #[(modifiers, stx)]
+
+def elabClassInductive (modifiers : Modifiers) (stx : Syntax) : CommandElabM Unit := do
+  let modifiers := modifiers.addAttr { name := `class }
+  elabInductive modifiers stx
+
+/--
+Returns true if all elements of the `mutual` block (`Lean.Parser.Command.mutual`) are inductive declarations.
+-/
+def isMutualInductive (stx : Syntax) : Bool :=
+  stx[1].getArgs.all fun elem =>
+    let decl     := elem[1]
+    let declKind := decl.getKind
+    declKind == `Lean.Parser.Command.inductive
+
+/--
+Elaborates a `mutual` block satisfying `Lean.Elab.Command.isMutualInductive`.
+-/
+def elabMutualInductive (elems : Array Syntax) : CommandElabM Unit := do
+  let inductives ← elems.mapM fun stx => do
+    let modifiers ← elabModifiers ⟨stx[0]⟩
+    pure (modifiers, stx[1])
+  elabInductives inductives
 
 end Lean.Elab.Command

src/Lean/Elab/MutualDef.lean

@@ -840,8 +840,8 @@ private def mkLetRecClosures (sectionVars : Array Expr) (mainFVarIds : Array FVa
 abbrev Replacement := FVarIdMap Expr
 
 def insertReplacementForMainFns (r : Replacement) (sectionVars : Array Expr) (mainHeaders : Array DefViewElabHeader) (mainFVars : Array Expr) : Replacement :=
-  mainFVars.size.fold (init := r) fun i _ r =>
-    r.insert mainFVars[i].fvarId! (mkAppN (Lean.mkConst mainHeaders[i]!.declName) sectionVars)
+  mainFVars.size.fold (init := r) fun i r =>
+    r.insert mainFVars[i]!.fvarId! (mkAppN (Lean.mkConst mainHeaders[i]!.declName) sectionVars)
 
 
 def insertReplacementForLetRecs (r : Replacement) (letRecClosures : List LetRecClosure) : Replacement :=
@@ -871,8 +871,8 @@ def Replacement.apply (r : Replacement) (e : Expr) : Expr :=
 
 def pushMain (preDefs : Array PreDefinition) (sectionVars : Array Expr) (mainHeaders : Array DefViewElabHeader) (mainVals : Array Expr)
     : TermElabM (Array PreDefinition) :=
-  mainHeaders.size.foldM (init := preDefs) fun i _ preDefs => do
-    let header := mainHeaders[i]
+  mainHeaders.size.foldM (init := preDefs) fun i preDefs => do
+    let header := mainHeaders[i]!
     let termination ← declValToTerminationHint header.value
     let termination := termination.rememberExtraParams header.numParams mainVals[i]!
     let value ← mkLambdaFVars sectionVars mainVals[i]!

src/Lean/Elab/Notation.lean

@@ -17,7 +17,7 @@ open Lean.Parser.Command
 private partial def antiquote (vars : Array Syntax) : Syntax → Syntax
   | stx => match stx with
   | `($id:ident) =>
-    if vars.any (fun var => var.getId == id.getId) then
+    if (vars.findIdx? (fun var => var.getId == id.getId)).isSome then
       mkAntiquotNode id (kind := `term) (isPseudoKind := true)
     else
       stx

src/Lean/Elab/PreDefinition/Structural/BRecOn.lean

@@ -145,8 +145,8 @@ private partial def replaceRecApps (recArgInfos : Array RecArgInfo) (positions :
     | Expr.app _ _ =>
       let processApp (e : Expr) : StateRefT (HasConstCache recFnNames) M Expr :=
         e.withApp fun f args => do
-          if let .some fnIdx := recArgInfos.findFinIdx? (f.isConstOf ·.fnName) then
-            let recArgInfo := recArgInfos[fnIdx]
+          if let .some fnIdx := recArgInfos.findIdx? (f.isConstOf ·.fnName) then
+            let recArgInfo := recArgInfos[fnIdx]!
             let some recArg := args[recArgInfo.recArgPos]?
               | throwError "insufficient number of parameters at recursive application {indentExpr e}"
             -- For reflexive type, we may have nested recursive applications in recArg

src/Lean/Elab/StructInst.lean

@@ -302,58 +302,59 @@ instance : ToFormat FieldLHS where
     | .fieldIndex _ i => format i
     | .modifyOp _ i   => "[" ++ i.prettyPrint ++ "]"
 
-mutual
-  /--
-  `FieldVal StructInstView` is a representation of a field value in the structure instance.
-  -/
-  inductive FieldVal where
-    /-- A `term` to use for the value of the field. -/
-    | term (stx : Syntax)         : FieldVal
-    /-- A `StructInstView` to use for the value of a subobject field. -/
-    | nested (s : StructInstView) : FieldVal
-    /-- A field that was not provided and should be synthesized using default values. -/
-    | default                     : FieldVal
-    deriving Inhabited
+/--
+`FieldVal StructInstView` is a representation of a field value in the structure instance.
+-/
+inductive FieldVal (σ : Type) where
+  /-- A `term` to use for the value of the field. -/
+  | term (stx : Syntax)  : FieldVal σ
+  /-- A `StructInstView` to use for the value of a subobject field. -/
+  | nested (s : σ)       : FieldVal σ
+  /-- A field that was not provided and should be synthesized using default values. -/
+  | default              : FieldVal σ
+  deriving Inhabited
 
-  /--
-  `Field StructInstView` is a representation of a field in the structure instance.
-  -/
-  structure Field where
-    /-- The whole field syntax. -/
-    ref   : Syntax
-    /-- The LHS decomposed into components. -/
-    lhs   : List FieldLHS
-    /-- The value of the field. -/
-    val   : FieldVal
-    /-- The elaborated field value, filled in at `elabStruct`.
-    Missing fields use a metavariable for the elaborated value and are later solved for in `DefaultFields.propagate`. -/
-    expr? : Option Expr := none
-    deriving Inhabited
-
-  /--
-  The view for structure instance notation.
-  -/
-  structure StructInstView where
-    /-- The syntax for the whole structure instance. -/
-    ref : Syntax
-    /-- The name of the structure for the type of the structure instance. -/
-    structName : Name
-    /-- Used for default values, to propagate structure type parameters. It is initially empty, and then set at `elabStruct`. -/
-    params : Array (Name × Expr)
-    /-- The fields of the structure instance. -/
-    fields : List Field
-    /-- The additional sources for fields for the structure instance. -/
-    sources : SourcesView
-    deriving Inhabited
-end
+/--
+`Field StructInstView` is a representation of a field in the structure instance.
+-/
+structure Field (σ : Type) where
+  /-- The whole field syntax. -/
+  ref   : Syntax
+  /-- The LHS decomposed into components. -/
+  lhs   : List FieldLHS
+  /-- The value of the field. -/
+  val   : FieldVal σ
+  /-- The elaborated field value, filled in at `elabStruct`.
+  Missing fields use a metavariable for the elaborated value and are later solved for in `DefaultFields.propagate`. -/
+  expr? : Option Expr := none
+  deriving Inhabited
 
 /--
 Returns if the field has a single component in its LHS.
 -/
-def Field.isSimple : Field → Bool
+def Field.isSimple {σ} : Field σ → Bool
   | { lhs := [_], .. } => true
   | _                  => false
 
+/--
+The view for structure instance notation.
+-/
+structure StructInstView where
+  /-- The syntax for the whole structure instance. -/
+  ref : Syntax
+  /-- The name of the structure for the type of the structure instance. -/
+  structName : Name
+  /-- Used for default values, to propagate structure type parameters. It is initially empty, and then set at `elabStruct`. -/
+  params : Array (Name × Expr)
+  /-- The fields of the structure instance. -/
+  fields : List (Field StructInstView)
+  /-- The additional sources for fields for the structure instance. -/
+  sources : SourcesView
+  deriving Inhabited
+
+/-- Abbreviation for the type of `StructInstView.fields`, namely `List (Field StructInstView)`. -/
+abbrev Fields := List (Field StructInstView)
+
 /-- `true` iff all fields of the given structure are marked as `default` -/
 partial def StructInstView.allDefault (s : StructInstView) : Bool :=
   s.fields.all fun { val := val,  .. } => match val with
@@ -361,7 +362,7 @@ partial def StructInstView.allDefault (s : StructInstView) : Bool :=
     | .default  => true
     | .nested s => allDefault s
 
-def formatField (formatStruct : StructInstView → Format) (field : Field) : Format :=
+def formatField (formatStruct : StructInstView → Format) (field : Field StructInstView) : Format :=
   Format.joinSep field.lhs " . " ++ " := " ++
     match field.val with
     | .term v   => v.prettyPrint
@@ -377,11 +378,11 @@ partial def formatStruct : StructInstView → Format
     else
       "{" ++ format (source.explicit.map (·.stx)) ++ " with " ++ fieldsFmt ++ implicitFmt ++ "}"
 
-instance : ToFormat StructInstView := ⟨formatStruct⟩
+instance : ToFormat StructInstView     := ⟨formatStruct⟩
 instance : ToString StructInstView := ⟨toString ∘ format⟩
 
-instance : ToFormat Field := ⟨formatField formatStruct⟩
-instance : ToString Field := ⟨toString ∘ format⟩
+instance : ToFormat (Field StructInstView) := ⟨formatField formatStruct⟩
+instance : ToString (Field StructInstView) := ⟨toString ∘ format⟩
 
 /--
 Converts a `FieldLHS` back into syntax. This assumes the `ref` fields have the correct structure.
@@ -402,14 +403,14 @@ private def FieldLHS.toSyntax (first : Bool) : FieldLHS → Syntax
 /--
 Converts a `FieldVal StructInstView` back into syntax. Only supports `.term`, and it assumes the `stx` field has the correct structure.
 -/
-private def FieldVal.toSyntax : FieldVal → Syntax
+private def FieldVal.toSyntax : FieldVal Struct → Syntax
   | .term stx => stx
   | _         => unreachable!
 
 /--
 Converts a `Field StructInstView` back into syntax. Used to construct synthetic structure instance notation for subobjects in `StructInst.expandStruct` processing.
 -/
-private def Field.toSyntax : Field → Syntax
+private def Field.toSyntax : Field Struct → Syntax
   | field =>
     let stx := field.ref
     let stx := stx.setArg 2 field.val.toSyntax
@@ -451,14 +452,14 @@ private def mkStructView (stx : Syntax) (structName : Name) (sources : SourcesVi
     let val      := fieldStx[2]
     let first    ← toFieldLHS fieldStx[0][0]
     let rest     ← fieldStx[0][1].getArgs.toList.mapM toFieldLHS
-    return { ref := fieldStx, lhs := first :: rest, val := FieldVal.term val : Field }
+    return { ref := fieldStx, lhs := first :: rest, val := FieldVal.term val : Field StructInstView }
   return { ref := stx, structName, params := #[], fields, sources }
 
-def StructInstView.modifyFieldsM {m : Type → Type} [Monad m] (s : StructInstView) (f : List Field → m (List Field)) : m StructInstView :=
+def StructInstView.modifyFieldsM {m : Type → Type} [Monad m] (s : StructInstView) (f : Fields → m Fields) : m StructInstView :=
   match s with
   | { ref, structName, params, fields, sources } => return { ref, structName, params, fields := (← f fields), sources }
 
-def StructInstView.modifyFields (s : StructInstView) (f : List Field → List Field) : StructInstView :=
+def StructInstView.modifyFields (s : StructInstView) (f : Fields → Fields) : StructInstView :=
   Id.run <| s.modifyFieldsM f
 
 /-- Expands name field LHSs with multi-component names into multi-component LHSs. -/
@@ -524,14 +525,14 @@ private def expandParentFields (s : StructInstView) : TermElabM StructInstView :
           | _ => throwErrorAt ref "failed to access field '{fieldName}' in parent structure"
     | _ => return field
 
-private abbrev FieldMap := Std.HashMap Name (List Field)
+private abbrev FieldMap := Std.HashMap Name Fields
 
 /--
 Creates a hash map collecting all fields with the same first name component.
 Throws an error if there are multiple simple fields with the same name.
 Used by `StructInst.expandStruct` processing.
 -/
-private def mkFieldMap (fields : List Field) : TermElabM FieldMap :=
+private def mkFieldMap (fields : Fields) : TermElabM FieldMap :=
   fields.foldlM (init := {}) fun fieldMap field =>
     match field.lhs with
     | .fieldName _ fieldName :: _    =>
@@ -547,7 +548,7 @@ private def mkFieldMap (fields : List Field) : TermElabM FieldMap :=
 /--
 Given a value of the hash map created by `mkFieldMap`, returns true if the value corresponds to a simple field.
 -/
-private def isSimpleField? : List Field → Option Field
+private def isSimpleField? : Fields → Option (Field StructInstView)
   | [field] => if field.isSimple then some field else none
   | _       => none
 
@@ -565,7 +566,7 @@ def mkProjStx? (s : Syntax) (structName : Name) (fieldName : Name) : TermElabM (
 /--
 Finds a simple field of the given name.
 -/
-def findField? (fields : List Field) (fieldName : Name) : Option Field :=
+def findField? (fields : Fields) (fieldName : Name) : Option (Field StructInstView) :=
   fields.find? fun field =>
     match field.lhs with
     | [.fieldName _ n] => n == fieldName
@@ -619,7 +620,7 @@ mutual
         match findField? s.fields fieldName with
         | some field => return field::fields
         | none       =>
-          let addField (val : FieldVal) : TermElabM (List Field) := do
+          let addField (val : FieldVal StructInstView) : TermElabM Fields := do
             return { ref, lhs := [FieldLHS.fieldName ref fieldName], val := val } :: fields
           match Lean.isSubobjectField? env s.structName fieldName with
           | some substructName =>
@@ -772,7 +773,7 @@ private partial def elabStructInstView (s : StructInstView) (expectedType? : Opt
       trace[Elab.struct] "elabStruct {field}, {type}"
       match type with
       | .forallE _ d b bi =>
-        let cont (val : Expr) (field : Field) (instMVars := instMVars) : TermElabM (Expr × Expr × List Field × Array MVarId) := do
+        let cont (val : Expr) (field : Field StructInstView) (instMVars := instMVars) : TermElabM (Expr × Expr × Fields × Array MVarId) := do
           pushInfoTree <| InfoTree.node (children := {}) <| Info.ofFieldInfo {
             projName := s.structName.append fieldName, fieldName, lctx := (← getLCtx), val, stx := ref }
           let e     := mkApp e val
@@ -878,7 +879,7 @@ partial def getHierarchyDepth (struct : StructInstView) : Nat :=
     | _ => max
 
 /-- Returns whether the field is still missing. -/
-def isDefaultMissing? [Monad m] [MonadMCtx m] (field : Field) : m Bool := do
+def isDefaultMissing? [Monad m] [MonadMCtx m] (field : Field Struct) : m Bool := do
   if let some expr := field.expr? then
     if let some (.mvar mvarId) := defaultMissing? expr then
       unless (← mvarId.isAssigned) do
@@ -886,17 +887,17 @@ def isDefaultMissing? [Monad m] [MonadMCtx m] (field : Field) : m Bool := do
   return false
 
 /-- Returns a field that is still missing. -/
-partial def findDefaultMissing? [Monad m] [MonadMCtx m] (struct : StructInstView) : m (Option Field) :=
+partial def findDefaultMissing? [Monad m] [MonadMCtx m] (struct : StructInstView) : m (Option (Field StructInstView)) :=
   struct.fields.findSomeM? fun field => do
    match field.val with
    | .nested struct => findDefaultMissing? struct
    | _ => return if (← isDefaultMissing? field) then field else none
 
 /-- Returns all fields that are still missing. -/
-partial def allDefaultMissing [Monad m] [MonadMCtx m] (struct : StructInstView) : m (Array Field) :=
+partial def allDefaultMissing [Monad m] [MonadMCtx m] (struct : StructInstView) : m (Array (Field StructInstView)) :=
   go struct *> get |>.run' #[]
 where
-  go (struct : StructInstView) : StateT (Array Field) m Unit :=
+  go (struct : StructInstView) : StateT (Array (Field StructInstView)) m Unit :=
     for field in struct.fields do
       if let .nested struct := field.val then
         go struct
@@ -904,7 +905,7 @@ where
         modify (·.push field)
 
 /-- Returns the name of the field. Assumes all fields under consideration are simple and named. -/
-def getFieldName (field : Field) : Name :=
+def getFieldName (field : Field StructInstView) : Name :=
   match field.lhs with
   | [.fieldName _ fieldName] => fieldName
   | _ => unreachable!

src/Lean/Elab/Structure.lean

@@ -4,15 +4,22 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Leonardo de Moura
 -/
 prelude
+import Lean.Class
+import Lean.Parser.Command
+import Lean.Meta.Closure
+import Lean.Meta.SizeOf
+import Lean.Meta.Injective
 import Lean.Meta.Structure
-import Lean.Elab.MutualInductive
+import Lean.Meta.AppBuilder
+import Lean.Elab.Command
+import Lean.Elab.DeclModifiers
+import Lean.Elab.DeclUtil
+import Lean.Elab.Inductive
+import Lean.Elab.DeclarationRange
+import Lean.Elab.Binders
 
 namespace Lean.Elab.Command
 
-builtin_initialize
-  registerTraceClass `Elab.structure
-  registerTraceClass `Elab.structure.resolutionOrder
-
 register_builtin_option structureDiamondWarning : Bool := {
   defValue := false
   descr    := "if true, enable warnings when a structure has diamond inheritance"
@@ -32,6 +39,13 @@ leading_parser (structureTk <|> classTk) >> declId >> many Term.bracketedBinder
 ```
 -/
 
+structure StructCtorView where
+  ref       : Syntax
+  modifiers : Modifiers
+  name      : Name
+  declName  : Name
+  deriving Inhabited
+
 structure StructFieldView where
   ref        : Syntax
   modifiers  : Modifiers
@@ -47,15 +61,22 @@ structure StructFieldView where
   type?      : Option Syntax
   value?     : Option Syntax
 
-structure StructView extends InductiveView where
-  parents         : Array Syntax
-  fields          : Array StructFieldView
+structure StructView where
+  ref             : Syntax
+  declId          : Syntax
+  modifiers       : Modifiers
+  isClass         : Bool -- struct-only
+  shortDeclName   : Name
+  declName        : Name
+  levelNames      : List Name
+  binders         : Syntax
+  type            : Syntax -- modified (inductive has type?)
+  parents         : Array Syntax -- struct-only
+  ctor            : StructCtorView -- struct-only
+  fields          : Array StructFieldView -- struct-only
+  derivingClasses : Array DerivingClassView
   deriving Inhabited
 
-def StructView.ctor : StructView → CtorView
-  | { ctors := #[ctor], ..} => ctor
-  | _ => unreachable!
-
 structure StructParentInfo where
   ref        : Syntax
   fvar?      : Option Expr
@@ -81,6 +102,18 @@ structure StructFieldInfo where
   value?   : Option Expr := none
   deriving Inhabited, Repr
 
+structure ElabStructHeaderResult where
+  view             : StructView
+  lctx             : LocalContext
+  localInsts       : LocalInstances
+  levelNames       : List Name
+  params           : Array Expr
+  type             : Expr
+  parents          : Array StructParentInfo
+  /-- Field infos from parents. -/
+  parentFieldInfos : Array StructFieldInfo
+  deriving Inhabited
+
 def StructFieldInfo.isFromParent (info : StructFieldInfo) : Bool :=
   match info.kind with
   | StructFieldKind.fromParent => true
@@ -97,12 +130,12 @@ The structure constructor syntax is
 leading_parser try (declModifiers >> ident >> " :: ")
 ```
 -/
-private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (structDeclName : Name) : TermElabM CtorView := do
+private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (structDeclName : Name) : TermElabM StructCtorView := do
   let useDefault := do
     let declName := structDeclName ++ defaultCtorName
     let ref := structStx[1].mkSynthetic
     addDeclarationRangesFromSyntax declName ref
-    pure { ref, declId := ref, modifiers := default, declName }
+    pure { ref, modifiers := default, name := defaultCtorName, declName }
   if structStx[5].isNone then
     useDefault
   else
@@ -123,7 +156,7 @@ private def expandCtor (structStx : Syntax) (structModifiers : Modifiers) (struc
       let declName ← applyVisibility ctorModifiers.visibility declName
       addDocString' declName ctorModifiers.docString?
       addDeclarationRangesFromSyntax declName ctor[1]
-      pure { ref := ctor[1], declId := ctor[1], modifiers := ctorModifiers, declName }
+      pure { ref := ctor[1], name, modifiers := ctorModifiers, declName }
 
 def checkValidFieldModifier (modifiers : Modifiers) : TermElabM Unit := do
   if modifiers.isNoncomputable then
@@ -238,7 +271,7 @@ def structureSyntaxToView (modifiers : Modifiers) (stx : Syntax) : TermElabM Str
   let parents   := if exts.isNone then #[] else exts[0][1].getSepArgs
   let optType   := stx[4]
   let derivingClasses ← getOptDerivingClasses stx[6]
-  let type?     := if optType.isNone then none else some optType[0][1]
+  let type      ← if optType.isNone then `(Sort _) else pure optType[0][1]
   let ctor ← expandCtor stx modifiers declName
   let fields ← expandFields stx modifiers declName
   fields.forM fun field => do
@@ -254,13 +287,10 @@ def structureSyntaxToView (modifiers : Modifiers) (stx : Syntax) : TermElabM Str
     declName
     levelNames
     binders
-    type?
-    allowIndices := false
-    allowSortPolymorphism := false
-    ctors := #[ctor]
+    type
     parents
+    ctor
     fields
-    computedFields := #[]
     derivingClasses
   }
 
@@ -285,7 +315,7 @@ private def findExistingField? (infos : Array StructFieldInfo) (parentStructName
       return some fieldName
   return none
 
-private def processSubfields (structDeclName : Name) (parentFVar : Expr) (parentStructName : Name) (subfieldNames : Array Name)
+private partial def processSubfields (structDeclName : Name) (parentFVar : Expr) (parentStructName : Name) (subfieldNames : Array Name)
     (infos : Array StructFieldInfo) (k : Array StructFieldInfo → TermElabM α) : TermElabM α :=
   go 0 infos
 where
@@ -506,7 +536,7 @@ private partial def mkToParentName (parentStructName : Name) (p : Name → Bool)
       if p curr then curr else go (i+1)
     go 1
 
-private def withParents (view : StructView) (rs : Array ElabHeaderResult) (indFVar : Expr)
+private partial def elabParents (view : StructView)
     (k : Array StructFieldInfo → Array StructParentInfo → TermElabM α) : TermElabM α := do
   go 0 #[] #[]
 where
@@ -514,17 +544,11 @@ where
     if h : i < view.parents.size then
       let parent := view.parents[i]
       withRef parent do
-      -- The only use case for autobound implicits for parents might be outParams, but outParam is not propagated.
-      let type ← Term.withoutAutoBoundImplicit <| Term.elabType parent
+      let type ← Term.elabType parent
       let parentType ← whnf type
-      if parentType.getAppFn == indFVar then
-        logWarning "structure extends itself, skipping"
-        return ← go (i + 1) infos parents
-      if rs.any (fun r => r.indFVar == parentType.getAppFn) then
-        throwError "structure cannot extend types defined in the same mutual block"
       let parentStructName ← getStructureName parentType
       if parents.any (fun info => info.structName == parentStructName) then
-        logWarning m!"duplicate parent structure '{.ofConstName parentStructName}', skipping"
+        logWarningAt parent m!"duplicate parent structure '{.ofConstName parentStructName}', skipping"
         go (i + 1) infos parents
       else if let some existingFieldName ← findExistingField? infos parentStructName then
         if structureDiamondWarning.get (← getOptions) then
@@ -546,13 +570,6 @@ where
     else
       k infos parents
 
-private def registerFailedToInferFieldType (fieldName : Name) (e : Expr) (ref : Syntax) : TermElabM Unit := do
-  Term.registerCustomErrorIfMVar (← instantiateMVars e) ref m!"failed to infer type of field '{.ofConstName fieldName}'"
-
-private def registerFailedToInferDefaultValue (fieldName : Name) (e : Expr) (ref : Syntax) : TermElabM Unit := do
-  Term.registerCustomErrorIfMVar (← instantiateMVars e) ref m!"failed to infer default value for field '{.ofConstName fieldName}'"
-  Term.registerLevelMVarErrorExprInfo e ref m!"failed to infer universe levels in default value for field '{.ofConstName fieldName}'"
-
 private def elabFieldTypeValue (view : StructFieldView) : TermElabM (Option Expr × Option Expr) :=
   Term.withAutoBoundImplicit <| Term.withAutoBoundImplicitForbiddenPred (fun n => view.name == n) <| Term.elabBinders view.binders.getArgs fun params => do
     match view.type? with
@@ -564,13 +581,10 @@ private def elabFieldTypeValue (view : StructFieldView) : TermElabM (Option Expr
         -- TODO: add forbidden predicate using `shortDeclName` from `view`
         let params ← Term.addAutoBoundImplicits params
         let value ← Term.withoutAutoBoundImplicit <| Term.elabTerm valStx none
-        registerFailedToInferFieldType view.name (← inferType value) view.nameId
-        registerFailedToInferDefaultValue view.name value valStx
         let value ← mkLambdaFVars params value
         return (none, value)
     | some typeStx =>
       let type ← Term.elabType typeStx
-      registerFailedToInferFieldType view.name type typeStx
       Term.synthesizeSyntheticMVarsNoPostponing
       let params ← Term.addAutoBoundImplicits params
       match view.value? with
@@ -579,7 +593,6 @@ private def elabFieldTypeValue (view : StructFieldView) : TermElabM (Option Expr
         return (type, none)
       | some valStx =>
         let value ← Term.withoutAutoBoundImplicit <| Term.elabTermEnsuringType valStx type
-        registerFailedToInferDefaultValue view.name value valStx
         Term.synthesizeSyntheticMVarsNoPostponing
         let type  ← mkForallFVars params type
         let value ← mkLambdaFVars params value
@@ -626,7 +639,6 @@ where
                 valStx ← `(fun $(view.binders.getArgs)* => $valStx:term)
               let fvarType ← inferType info.fvar
               let value ← Term.elabTermEnsuringType valStx fvarType
-              registerFailedToInferDefaultValue view.name value valStx
               pushInfoLeaf <| .ofFieldRedeclInfo { stx := view.ref }
               let infos := replaceFieldInfo infos { info with ref := view.nameId, value? := value }
               go (i+1) defaultValsOverridden infos
@@ -638,14 +650,113 @@ where
     else
       k infos
 
-private def collectUsedFVars (lctx : LocalContext) (localInsts : LocalInstances) (fieldInfos : Array StructFieldInfo) :
-    StateRefT CollectFVars.State MetaM Unit := do
-  withLCtx lctx localInsts do
-    fieldInfos.forM fun info => do
-      let fvarType ← inferType info.fvar
-      fvarType.collectFVars
-      if let some value := info.value? then
-        value.collectFVars
+private def getResultUniverse (type : Expr) : TermElabM Level := do
+  let type ← whnf type
+  match type with
+  | Expr.sort u => pure u
+  | _           => throwError "unexpected structure resulting type"
+
+private def collectUsed (params : Array Expr) (fieldInfos : Array StructFieldInfo) : StateRefT CollectFVars.State MetaM Unit := do
+  params.forM fun p => do
+    let type ← inferType p
+    type.collectFVars
+  fieldInfos.forM fun info => do
+    let fvarType ← inferType info.fvar
+    fvarType.collectFVars
+    match info.value? with
+    | none       => pure ()
+    | some value => value.collectFVars
+
+private def removeUnused (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo)
+    : TermElabM (LocalContext × LocalInstances × Array Expr) := do
+  let (_, used) ← (collectUsed params fieldInfos).run {}
+  Meta.removeUnused scopeVars used
+
+private def withUsed {α} (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo) (k : Array Expr → TermElabM α)
+    : TermElabM α := do
+  let (lctx, localInsts, vars) ← removeUnused scopeVars params fieldInfos
+  withLCtx lctx localInsts <| k vars
+
+private def levelMVarToParam (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo) (univToInfer? : Option LMVarId) : TermElabM (Array StructFieldInfo) := do
+  levelMVarToParamFVars scopeVars
+  levelMVarToParamFVars params
+  fieldInfos.mapM fun info => do
+    levelMVarToParamFVar info.fvar
+    match info.value? with
+    | none       => pure info
+    | some value =>
+      let value ← levelMVarToParam' value
+      pure { info with value? := value }
+where
+  levelMVarToParam' (type : Expr) : TermElabM Expr := do
+    Term.levelMVarToParam type (except := fun mvarId => univToInfer? == some mvarId)
+
+  levelMVarToParamFVars (fvars : Array Expr) : TermElabM Unit :=
+    fvars.forM levelMVarToParamFVar
+
+  levelMVarToParamFVar (fvar : Expr) : TermElabM Unit := do
+    let type ← inferType fvar
+    discard <| levelMVarToParam' type
+
+
+private partial def collectUniversesFromFields (r : Level) (rOffset : Nat) (fieldInfos : Array StructFieldInfo) : TermElabM (Array Level) := do
+  let (_, us) ← go |>.run #[]
+  return us
+where
+  go : StateRefT (Array Level) TermElabM Unit :=
+    for info in fieldInfos do
+      let type ← inferType info.fvar
+      let u ← getLevel type
+      let u ← instantiateLevelMVars u
+      match (← modifyGet fun s => accLevel u r rOffset |>.run |>.run s) with
+      | some _ => pure ()
+      | none =>
+        let typeType ← inferType type
+        let mut msg := m!"failed to compute resulting universe level of structure, field '{info.declName}' has type{indentD m!"{type} : {typeType}"}\nstructure resulting type{indentExpr (mkSort (r.addOffset rOffset))}"
+        if r.isMVar then
+          msg := msg ++ "\nrecall that Lean only infers the resulting universe level automatically when there is a unique solution for the universe level constraints, consider explicitly providing the structure resulting universe level"
+        throwError msg
+
+/--
+Decides whether the structure should be `Prop`-valued when the universe is not given
+and when the universe inference algorithm `collectUniversesFromFields` determines
+that the inductive type could naturally be `Prop`-valued.
+
+See `Lean.Elab.Command.isPropCandidate` for an explanation.
+Specialized to structures, the heuristic is that we prefer a `Prop` instead of a `Type` structure
+when it could be a syntactic subsingleton.
+Exception: no-field structures are `Type` since they are likely stubbed-out declarations.
+-/
+private def isPropCandidate (fieldInfos : Array StructFieldInfo) : Bool :=
+  !fieldInfos.isEmpty
+
+private def updateResultingUniverse (fieldInfos : Array StructFieldInfo) (type : Expr) : TermElabM Expr := do
+  let r ← getResultUniverse type
+  let rOffset : Nat   := r.getOffset
+  let r       : Level := r.getLevelOffset
+  unless r.isMVar do
+    throwError "failed to compute resulting universe level of inductive datatype, provide universe explicitly: {r}"
+  let us ← collectUniversesFromFields r rOffset fieldInfos
+  trace[Elab.structure] "updateResultingUniverse us: {us}, r: {r}, rOffset: {rOffset}"
+  let rNew := mkResultUniverse us rOffset (isPropCandidate fieldInfos)
+  assignLevelMVar r.mvarId! rNew
+  instantiateMVars type
+
+private def collectLevelParamsInFVar (s : CollectLevelParams.State) (fvar : Expr) : TermElabM CollectLevelParams.State := do
+  let type ← inferType fvar
+  let type ← instantiateMVars type
+  return collectLevelParams s type
+
+private def collectLevelParamsInFVars (fvars : Array Expr) (s : CollectLevelParams.State) : TermElabM CollectLevelParams.State :=
+  fvars.foldlM collectLevelParamsInFVar s
+
+private def collectLevelParamsInStructure (structType : Expr) (scopeVars : Array Expr) (params : Array Expr) (fieldInfos : Array StructFieldInfo)
+    : TermElabM (Array Name) := do
+  let s := collectLevelParams {} structType
+  let s ← collectLevelParamsInFVars scopeVars s
+  let s ← collectLevelParamsInFVars params s
+  let s ← fieldInfos.foldlM (init := s) fun s info => collectLevelParamsInFVar s info.fvar
+  return s.params
 
 private def addCtorFields (fieldInfos : Array StructFieldInfo) : Nat → Expr → TermElabM Expr
   | 0,   type => pure type
@@ -661,29 +772,19 @@ private def addCtorFields (fieldInfos : Array StructFieldInfo) : Nat → Expr
     | _  =>
       addCtorFields fieldInfos i (mkForall decl.userName decl.binderInfo decl.type type)
 
-private def mkCtor (view : StructView) (r : ElabHeaderResult) (params : Array Expr) (fieldInfos : Array StructFieldInfo) : TermElabM Constructor :=
+private def mkCtor (view : StructView) (levelParams : List Name) (params : Array Expr) (fieldInfos : Array StructFieldInfo) : TermElabM Constructor :=
   withRef view.ref do
-  let type := mkAppN r.indFVar params
+  let type := mkAppN (mkConst view.declName (levelParams.map mkLevelParam)) params
   let type ← addCtorFields fieldInfos fieldInfos.size type
   let type ← mkForallFVars params type
   let type ← instantiateMVars type
   let type := type.inferImplicit params.size true
   pure { name := view.ctor.declName, type }
 
-private partial def checkResultingUniversesForFields (fieldInfos : Array StructFieldInfo) (u : Level) : TermElabM Unit := do
-  for info in fieldInfos do
-    let type ← inferType info.fvar
-    let v := (← instantiateLevelMVars (← getLevel type)).normalize
-    unless u.geq v do
-      let msg := m!"invalid universe level for field '{info.name}', has type{indentExpr type}\n\
-        at universe level{indentD v}\n\
-        which is not less than or equal to the structure's resulting universe level{indentD u}"
-      throwErrorAt info.ref msg
-
 @[extern "lean_mk_projections"]
 private opaque mkProjections (env : Environment) (structName : Name) (projs : List Name) (isClass : Bool) : Except KernelException Environment
 
-private def addProjections (r : ElabHeaderResult) (fieldInfos : Array StructFieldInfo) : TermElabM Unit := do
+private def addProjections (r : ElabStructHeaderResult) (fieldInfos : Array StructFieldInfo) : TermElabM Unit := do
   if r.type.isProp then
     if let some fieldInfo ← fieldInfos.findM? (not <$> Meta.isProof ·.fvar) then
       throwErrorAt fieldInfo.ref m!"failed to generate projections for 'Prop' structure, field '{format fieldInfo.name}' is not a proof"
@@ -694,71 +795,49 @@ private def addProjections (r : ElabHeaderResult) (fieldInfos : Array StructFiel
 
 private def registerStructure (structName : Name) (infos : Array StructFieldInfo) : TermElabM Unit := do
   let fields ← infos.filterMapM fun info => do
-    if info.kind == StructFieldKind.fromParent then
-      return none
-    else
-      return some {
-        fieldName  := info.name
-        projFn     := info.declName
-        binderInfo := (← getFVarLocalDecl info.fvar).binderInfo
-        autoParam? := (← inferType info.fvar).getAutoParamTactic?
-        subobject? := if let .subobject parentName := info.kind then parentName else none
-      }
+      if info.kind == StructFieldKind.fromParent then
+        return none
+      else
+        return some {
+          fieldName  := info.name
+          projFn     := info.declName
+          binderInfo := (← getFVarLocalDecl info.fvar).binderInfo
+          autoParam? := (← inferType info.fvar).getAutoParamTactic?
+          subobject? := if let .subobject parentName := info.kind then parentName else none
+        }
   modifyEnv fun env => Lean.registerStructure env { structName, fields }
 
-private def checkDefaults (fieldInfos : Array StructFieldInfo) : TermElabM Unit := do
-  let mut mvars := {}
-  let mut lmvars := {}
-  for fieldInfo in fieldInfos do
-    if let some value := fieldInfo.value? then
-      let value ← instantiateMVars value
-      mvars := Expr.collectMVars mvars value
-      lmvars := collectLevelMVars lmvars value
-  -- Log errors and ignore the failure; we later will just omit adding a default value.
-  if ← Term.logUnassignedUsingErrorInfos mvars.result then
-    return
-  else if ← Term.logUnassignedLevelMVarsUsingErrorInfos lmvars.result then
-    return
+private def mkAuxConstructions (declName : Name) : TermElabM Unit := do
+  let env ← getEnv
+  let hasEq   := env.contains ``Eq
+  let hasHEq  := env.contains ``HEq
+  let hasUnit := env.contains ``PUnit
+  let hasProd := env.contains ``Prod
+  mkRecOn declName
+  if hasUnit then mkCasesOn declName
+  if hasUnit && hasEq && hasHEq then mkNoConfusion declName
+  let ival ← getConstInfoInduct declName
+  if ival.isRec then
+    if hasUnit && hasProd then mkBelow declName
+    if hasUnit && hasProd then mkIBelow declName
+    if hasUnit && hasProd then mkBRecOn declName
+    if hasUnit && hasProd then mkBInductionOn declName
 
-private def addDefaults (params : Array Expr) (replaceIndFVars : Expr → MetaM Expr) (fieldInfos : Array StructFieldInfo) : TermElabM Unit := do
-  let lctx ← getLCtx
-  /- The `lctx` and `defaultAuxDecls` are used to create the auxiliary "default value" declarations
-    The parameters `params` for these definitions must be marked as implicit, and all others as explicit. -/
-  let lctx :=
-    params.foldl (init := lctx) fun (lctx : LocalContext) (p : Expr) =>
-      if p.isFVar then
-        lctx.setBinderInfo p.fvarId! BinderInfo.implicit
-      else
-        lctx
-  let lctx :=
-    fieldInfos.foldl (init := lctx) fun (lctx : LocalContext) (info : StructFieldInfo) =>
-      if info.isFromParent then lctx -- `fromParent` fields are elaborated as let-decls, and are zeta-expanded when creating "default value" auxiliary functions
-      else lctx.setBinderInfo info.fvar.fvarId! BinderInfo.default
-  -- Make all indFVar replacements in the local context.
-  let lctx ←
-    lctx.foldlM (init := {}) fun lctx ldecl => do
-     match ldecl with
-     | .cdecl _ fvarId userName type bi k =>
-       let type ← replaceIndFVars type
-       return lctx.mkLocalDecl fvarId userName type bi k
-     | .ldecl _ fvarId userName type value nonDep k =>
-       let type ← replaceIndFVars type
-       let value ← replaceIndFVars value
-       return lctx.mkLetDecl fvarId userName type value nonDep k
+private def addDefaults (lctx : LocalContext) (fieldInfos : Array StructFieldInfo) : TermElabM Unit := do
   withLCtx lctx (← getLocalInstances) do
     fieldInfos.forM fun fieldInfo => do
       if let some value := fieldInfo.value? then
         let declName := mkDefaultFnOfProjFn fieldInfo.declName
-        let type ← replaceIndFVars (← inferType fieldInfo.fvar)
-        let value ← instantiateMVars (← replaceIndFVars value)
-        trace[Elab.structure] "default value after 'replaceIndFVars': {indentExpr value}"
-        -- If there are mvars, `checkDefaults` already logged an error.
-        unless value.hasMVar || value.hasSyntheticSorry do
-          /- The identity function is used as "marker". -/
-          let value ← mkId value
-          -- No need to compile the definition, since it is only used during elaboration.
-          discard <| mkAuxDefinition declName type value (zetaDelta := true) (compile := false)
-          setReducibleAttribute declName
+        let type ← inferType fieldInfo.fvar
+        let value ← instantiateMVars value
+        if value.hasExprMVar then
+          discard <| Term.logUnassignedUsingErrorInfos (← getMVars value)
+          throwErrorAt fieldInfo.ref "invalid default value for field '{format fieldInfo.name}', it contains metavariables{indentExpr value}"
+        /- The identity function is used as "marker". -/
+        let value ← mkId value
+        -- No need to compile the definition, since it is only used during elaboration.
+        discard <| mkAuxDefinition declName type value (zetaDelta := true) (compile := false)
+        setReducibleAttribute declName
 
 /--
 Given `type` of the form `forall ... (source : A), B`, return `forall ... [source : A], B`.
@@ -775,81 +854,108 @@ private def setSourceInstImplicit (type : Expr) : Expr :=
 /--
 Creates a projection function to a non-subobject parent.
 -/
-private partial def mkCoercionToCopiedParent (levelParams : List Name) (params : Array Expr) (view : StructView) (source : Expr) (parentStructName : Name) (parentType : Expr) : MetaM StructureParentInfo := do
+private partial def mkCoercionToCopiedParent (levelParams : List Name) (params : Array Expr) (view : StructView) (parentStructName : Name) (parentType : Expr) : MetaM StructureParentInfo := do
   let isProp ← Meta.isProp parentType
   let env ← getEnv
   let structName := view.declName
   let sourceFieldNames := getStructureFieldsFlattened env structName
+  let structType := mkAppN (Lean.mkConst structName (levelParams.map mkLevelParam)) params
   let binfo := if view.isClass && isClass env parentStructName then BinderInfo.instImplicit else BinderInfo.default
-  let mut declType ← instantiateMVars (← mkForallFVars params (← mkForallFVars #[source] parentType))
-  if view.isClass && isClass env parentStructName then
-    declType := setSourceInstImplicit declType
-  declType := declType.inferImplicit params.size true
-  let rec copyFields (parentType : Expr) : MetaM Expr := do
-    let Expr.const parentStructName us ← pure parentType.getAppFn | unreachable!
-    let parentCtor := getStructureCtor env parentStructName
-    let mut result := mkAppN (mkConst parentCtor.name us) parentType.getAppArgs
-    for fieldName in getStructureFields env parentStructName do
-      if sourceFieldNames.contains fieldName then
-        let fieldVal ← mkProjection source fieldName
-        result := mkApp result fieldVal
-      else
-        -- fieldInfo must be a field of `parentStructName`
-        let some fieldInfo := getFieldInfo? env parentStructName fieldName | unreachable!
-        if fieldInfo.subobject?.isNone then throwError "failed to build coercion to parent structure"
-        let resultType ← whnfD (← inferType result)
-        unless resultType.isForall do throwError "failed to build coercion to parent structure, unexpected type{indentExpr resultType}"
-        let fieldVal ← copyFields resultType.bindingDomain!
-        result := mkApp result fieldVal
-    return result
-  let declVal ← instantiateMVars (← mkLambdaFVars params (← mkLambdaFVars #[source] (← copyFields parentType)))
-  let declName := structName ++ mkToParentName (← getStructureName parentType) fun n => !env.contains (structName ++ n)
-  -- Logic from `mk_projections`: prop-valued projections are theorems (or at least opaque)
-  let cval : ConstantVal := { name := declName, levelParams, type := declType }
-  if isProp then
-    addDecl <|
-      if view.modifiers.isUnsafe then
-        -- Theorems cannot be unsafe.
-        Declaration.opaqueDecl { cval with value := declVal, isUnsafe := true }
-      else
-        Declaration.thmDecl { cval with value := declVal }
-  else
-    addAndCompile <| Declaration.defnDecl { cval with
-      value       := declVal
-      hints       := ReducibilityHints.abbrev
-      safety      := if view.modifiers.isUnsafe then DefinitionSafety.unsafe else DefinitionSafety.safe
-    }
-  -- Logic from `mk_projections`: non-instance-implicits that aren't props become reducible.
-  -- (Instances will get instance reducibility in `Lean.Elab.Command.addParentInstances`.)
-  if !binfo.isInstImplicit && !(← Meta.isProp parentType) then
-    setReducibleAttribute declName
-  return { structName := parentStructName, subobject := false, projFn := declName }
-
-private def mkRemainingProjections (levelParams : List Name) (params : Array Expr) (view : StructView)
-    (parents : Array StructParentInfo) (fieldInfos : Array StructFieldInfo) : TermElabM (Array StructureParentInfo) := do
-  let structType := mkAppN (Lean.mkConst view.declName (levelParams.map mkLevelParam)) params
   withLocalDeclD `self structType fun source => do
-    /-
-    Remark: copied parents might still be referring to the fvars of other parents. We need to replace these fvars with projection constants.
-    For subobject parents, this has already been done by `mkProjections`.
-    https://github.com/leanprover/lean4/issues/2611
-    -/
-    let mut parentInfos := #[]
-    let mut parentFVarToConst : ExprMap Expr := {}
-    for h : i in [0:parents.size] do
-      let parent := parents[i]
-      let parentInfo : StructureParentInfo ← (do
-        if parent.subobject then
-          let some info := fieldInfos.find? (·.kind == .subobject parent.structName) | unreachable!
-          pure { structName := parent.structName, subobject := true, projFn := info.declName }
+    let mut declType ← instantiateMVars (← mkForallFVars params (← mkForallFVars #[source] parentType))
+    if view.isClass && isClass env parentStructName then
+      declType := setSourceInstImplicit declType
+    declType := declType.inferImplicit params.size true
+    let rec copyFields (parentType : Expr) : MetaM Expr := do
+      let Expr.const parentStructName us ← pure parentType.getAppFn | unreachable!
+      let parentCtor := getStructureCtor env parentStructName
+      let mut result := mkAppN (mkConst parentCtor.name us) parentType.getAppArgs
+      for fieldName in getStructureFields env parentStructName do
+        if sourceFieldNames.contains fieldName then
+          let fieldVal ← mkProjection source fieldName
+          result := mkApp result fieldVal
         else
-          let parent_type := (← instantiateMVars parent.type).replace fun e => parentFVarToConst[e]?
-          mkCoercionToCopiedParent levelParams params view source parent.structName parent_type)
-      parentInfos := parentInfos.push parentInfo
-      if let some fvar := parent.fvar? then
-        parentFVarToConst := parentFVarToConst.insert fvar <|
-          mkApp (mkAppN (.const parentInfo.projFn (levelParams.map mkLevelParam)) params) source
-    pure parentInfos
+          -- fieldInfo must be a field of `parentStructName`
+          let some fieldInfo := getFieldInfo? env parentStructName fieldName | unreachable!
+          if fieldInfo.subobject?.isNone then throwError "failed to build coercion to parent structure"
+          let resultType ← whnfD (← inferType result)
+          unless resultType.isForall do throwError "failed to build coercion to parent structure, unexpected type{indentExpr resultType}"
+          let fieldVal ← copyFields resultType.bindingDomain!
+          result := mkApp result fieldVal
+      return result
+    let declVal ← instantiateMVars (← mkLambdaFVars params (← mkLambdaFVars #[source] (← copyFields parentType)))
+    let declName := structName ++ mkToParentName (← getStructureName parentType) fun n => !env.contains (structName ++ n)
+    -- Logic from `mk_projections`: prop-valued projections are theorems (or at least opaque)
+    let cval : ConstantVal := { name := declName, levelParams, type := declType }
+    if isProp then
+      addDecl <|
+        if view.modifiers.isUnsafe then
+          -- Theorems cannot be unsafe.
+          Declaration.opaqueDecl { cval with value := declVal, isUnsafe := true }
+        else
+          Declaration.thmDecl { cval with value := declVal }
+    else
+      addAndCompile <| Declaration.defnDecl { cval with
+        value       := declVal
+        hints       := ReducibilityHints.abbrev
+        safety      := if view.modifiers.isUnsafe then DefinitionSafety.unsafe else DefinitionSafety.safe
+      }
+    -- Logic from `mk_projections`: non-instance-implicits that aren't props become reducible.
+    -- (Instances will get instance reducibility in `Lean.Elab.Command.addParentInstances`.)
+    if !binfo.isInstImplicit && !(← Meta.isProp parentType) then
+      setReducibleAttribute declName
+    return { structName := parentStructName, subobject := false, projFn := declName }
+
+private def elabStructHeader (view : StructView) : TermElabM ElabStructHeaderResult :=
+  Term.withAutoBoundImplicitForbiddenPred (fun n => view.shortDeclName == n) do
+  Term.withAutoBoundImplicit do
+  Term.elabBinders view.binders.getArgs fun params => do
+  elabParents view fun parentFieldInfos parents => do
+    let type ← Term.elabType view.type
+    Term.synthesizeSyntheticMVarsNoPostponing
+    let u ← mkFreshLevelMVar
+    unless ← isDefEq type (mkSort u) do
+      throwErrorAt view.type "invalid structure type, expecting 'Type _' or 'Prop'"
+    let type ← instantiateMVars (← whnf type)
+    Term.addAutoBoundImplicits' params type fun params type => do
+      let levelNames ← Term.getLevelNames
+      trace[Elab.structure] "header params: {params}, type: {type}, levelNames: {levelNames}"
+      return { lctx := (← getLCtx), localInsts := (← getLocalInstances), levelNames, params, type, view, parents, parentFieldInfos }
+
+private def mkTypeFor (r : ElabStructHeaderResult) : TermElabM Expr := do
+  withLCtx r.lctx r.localInsts do
+    mkForallFVars r.params r.type
+
+/--
+Create a local declaration for the structure and execute `x params indFVar`, where `params` are the structure's type parameters and
+`indFVar` is the new local declaration.
+-/
+private partial def withStructureLocalDecl (r : ElabStructHeaderResult) (x : Array Expr → Expr → TermElabM α) : TermElabM α := do
+  let declName := r.view.declName
+  let shortDeclName := r.view.shortDeclName
+  let type ← mkTypeFor r
+  let params := r.params
+  withLCtx r.lctx r.localInsts <| withRef r.view.ref do
+    Term.withAuxDecl shortDeclName type declName fun indFVar =>
+      x params indFVar
+
+/--
+Remark: `numVars <= numParams`.
+`numVars` is the number of context `variables` used in the declaration,
+and `numParams - numVars` is the number of parameters provided as binders in the declaration.
+-/
+private def mkInductiveType (view : StructView) (indFVar : Expr) (levelNames : List Name)
+    (numVars : Nat) (numParams : Nat) (type : Expr) (ctor : Constructor) : TermElabM InductiveType := do
+  let levelParams := levelNames.map mkLevelParam
+  let const := mkConst view.declName levelParams
+  let ctorType ← forallBoundedTelescope ctor.type numParams fun params type => do
+    let type := type.replace fun e =>
+      if e == indFVar then
+        mkAppN const (params.extract 0 numVars)
+      else
+        none
+    instantiateMVars (← mkForallFVars params type)
+  return { name := view.declName, type := ← instantiateMVars type, ctors := [{ ctor with type := ← instantiateMVars ctorType }] }
 
 /--
 Precomputes the structure's resolution order.
@@ -881,45 +987,109 @@ private def addParentInstances (parents : Array StructureParentInfo) : MetaM Uni
   for instParent in instParents do
     addInstance instParent.projFn AttributeKind.global (eval_prio default)
 
-@[builtin_inductive_elab Lean.Parser.Command.«structure»]
-def elabStructureCommand : InductiveElabDescr where
-  mkInductiveView (modifiers : Modifiers) (stx : Syntax) := do
+def mkStructureDecl (vars : Array Expr) (view : StructView) : TermElabM Unit := Term.withoutSavingRecAppSyntax do
+  let scopeLevelNames ← Term.getLevelNames
+  let isUnsafe := view.modifiers.isUnsafe
+  withRef view.ref <| Term.withLevelNames view.levelNames do
+    let r ← elabStructHeader view
+    Term.synthesizeSyntheticMVarsNoPostponing
+    withLCtx r.lctx r.localInsts do
+    withStructureLocalDecl r fun params indFVar => do
+    trace[Elab.structure] "indFVar: {indFVar}"
+    Term.addLocalVarInfo view.declId indFVar
+    withFields view.fields r.parentFieldInfos fun fieldInfos =>
+    withRef view.ref do
+      Term.synthesizeSyntheticMVarsNoPostponing
+      let type ← instantiateMVars r.type
+      let u ← getResultUniverse type
+      let univToInfer? ← shouldInferResultUniverse u
+      withUsed vars params fieldInfos fun scopeVars => do
+        let fieldInfos ← levelMVarToParam scopeVars params fieldInfos univToInfer?
+        let type ← withRef view.ref do
+          if univToInfer?.isSome then
+            updateResultingUniverse fieldInfos type
+          else
+            checkResultingUniverse (← getResultUniverse type)
+            pure type
+        trace[Elab.structure] "type: {type}"
+        let usedLevelNames ← collectLevelParamsInStructure type scopeVars params fieldInfos
+        match sortDeclLevelParams scopeLevelNames r.levelNames usedLevelNames with
+        | Except.error msg      => throwErrorAt view.declId msg
+        | Except.ok levelParams =>
+          let params := scopeVars ++ params
+          let ctor ← mkCtor view levelParams params fieldInfos
+          let type ← mkForallFVars params type
+          let type ← instantiateMVars type
+          let indType ← mkInductiveType view indFVar levelParams scopeVars.size params.size type ctor
+          let decl    := Declaration.inductDecl levelParams params.size [indType] isUnsafe
+          Term.ensureNoUnassignedMVars decl
+          addDecl decl
+          -- rename indFVar so that it does not shadow the actual declaration:
+          let lctx := (← getLCtx).modifyLocalDecl indFVar.fvarId! fun decl => decl.setUserName .anonymous
+          withLCtx lctx (← getLocalInstances) do
+          addProjections r fieldInfos
+          registerStructure view.declName fieldInfos
+          mkAuxConstructions view.declName
+          withSaveInfoContext do  -- save new env
+            Term.addLocalVarInfo view.ref[1] (← mkConstWithLevelParams view.declName)
+            if let some _ := view.ctor.ref.getPos? (canonicalOnly := true) then
+              Term.addTermInfo' view.ctor.ref (← mkConstWithLevelParams view.ctor.declName) (isBinder := true)
+            for field in view.fields do
+              -- may not exist if overriding inherited field
+              if (← getEnv).contains field.declName then
+                Term.addTermInfo' field.ref (← mkConstWithLevelParams field.declName) (isBinder := true)
+          withRef view.declId do
+            Term.applyAttributesAt view.declName view.modifiers.attrs AttributeApplicationTime.afterTypeChecking
+          let parentInfos ← r.parents.mapM fun parent => do
+            if parent.subobject then
+              let some info := fieldInfos.find? (·.kind == .subobject parent.structName) | unreachable!
+              pure { structName := parent.structName, subobject := true, projFn := info.declName }
+            else
+              mkCoercionToCopiedParent levelParams params view parent.structName parent.type
+          setStructureParents view.declName parentInfos
+          checkResolutionOrder view.declName
+          if view.isClass then
+            addParentInstances parentInfos
+
+          let lctx ← getLCtx
+          /- The `lctx` and `defaultAuxDecls` are used to create the auxiliary "default value" declarations
+            The parameters `params` for these definitions must be marked as implicit, and all others as explicit. -/
+          let lctx :=
+            params.foldl (init := lctx) fun (lctx : LocalContext) (p : Expr) =>
+              if p.isFVar then
+                lctx.setBinderInfo p.fvarId! BinderInfo.implicit
+              else
+                lctx
+          let lctx :=
+            fieldInfos.foldl (init := lctx) fun (lctx : LocalContext) (info : StructFieldInfo) =>
+              if info.isFromParent then lctx -- `fromParent` fields are elaborated as let-decls, and are zeta-expanded when creating "default value" auxiliary functions
+              else lctx.setBinderInfo info.fvar.fvarId! BinderInfo.default
+          addDefaults lctx fieldInfos
+
+
+def elabStructureView (vars : Array Expr) (view : StructView) : TermElabM Unit := do
+  Term.withDeclName view.declName <| withRef view.ref do
+    mkStructureDecl vars view
+    unless view.isClass do
+      Lean.Meta.IndPredBelow.mkBelow view.declName
+      mkSizeOfInstances view.declName
+      mkInjectiveTheorems view.declName
+
+def elabStructureViewPostprocessing (view : StructView) : CommandElabM Unit := do
+  view.derivingClasses.forM fun classView => classView.applyHandlers #[view.declName]
+  runTermElabM fun _ => Term.withDeclName view.declName <| withRef view.declId do
+    Term.applyAttributesAt view.declName view.modifiers.attrs .afterCompilation
+
+def elabStructure (modifiers : Modifiers) (stx : Syntax) : CommandElabM Unit := do
+  let view ← runTermElabM fun vars => do
     let view ← structureSyntaxToView modifiers stx
     trace[Elab.structure] "view.levelNames: {view.levelNames}"
-    return {
-      view := view.toInductiveView
-      elabCtors := fun rs r params => do
-        withParents view rs r.indFVar fun parentFieldInfos parents =>
-        withFields view.fields parentFieldInfos fun fieldInfos => do
-        withRef view.ref do
-          Term.synthesizeSyntheticMVarsNoPostponing
-          let lctx ← getLCtx
-          let localInsts ← getLocalInstances
-          let ctor ← mkCtor view r params fieldInfos
-          return {
-            ctors := [ctor]
-            collectUsedFVars := collectUsedFVars lctx localInsts fieldInfos
-            checkUniverses := fun _ u => withLCtx lctx localInsts do checkResultingUniversesForFields fieldInfos u
-            finalizeTermElab := withLCtx lctx localInsts do checkDefaults fieldInfos
-            prefinalize := fun _ _ _ => do
-              withLCtx lctx localInsts do
-                addProjections r fieldInfos
-                registerStructure view.declName fieldInfos
-              withSaveInfoContext do  -- save new env
-                for field in view.fields do
-                  -- may not exist if overriding inherited field
-                  if (← getEnv).contains field.declName then
-                    Term.addTermInfo' field.ref (← mkConstWithLevelParams field.declName) (isBinder := true)
-            finalize := fun levelParams params replaceIndFVars => do
-              let parentInfos ← mkRemainingProjections levelParams params view parents fieldInfos
-              setStructureParents view.declName parentInfos
-              checkResolutionOrder view.declName
-              if view.isClass then
-                addParentInstances parentInfos
+    elabStructureView vars view
+    pure view
+  elabStructureViewPostprocessing view
 
-              withLCtx lctx localInsts do
-                addDefaults params replaceIndFVars fieldInfos
-          }
-    }
+builtin_initialize
+  registerTraceClass `Elab.structure
+  registerTraceClass `Elab.structure.resolutionOrder
 
 end Lean.Elab.Command

src/Lean/Elab/Tactic/BVDecide/Frontend/BVDecide/ReifiedLemmas.lean

@@ -58,28 +58,15 @@ where
     let some eqBVPred ← ReifiedBVPred.mkBinPred atom resValExpr atomExpr resExpr .eq | return none
     let eqBV ← ReifiedBVLogical.ofPred eqBVPred
 
+    let trueExpr := mkConst ``Bool.true
+    let impExpr ← mkArrow (← mkEq eqDiscrExpr trueExpr) (← mkEq eqBVExpr trueExpr)
+    let decideImpExpr ← mkAppOptM ``Decidable.decide #[some impExpr, none]
     let imp ← ReifiedBVLogical.mkGate eqDiscr eqBV eqDiscrExpr eqBVExpr .imp
 
     let proof := do
       let evalExpr ← ReifiedBVLogical.mkEvalExpr imp.expr
       let congrProof ← imp.evalsAtAtoms
       let lemmaProof := mkApp4 (mkConst lemmaName) (toExpr lhs.width) discrExpr lhsExpr rhsExpr
-
-      let trueExpr := mkConst ``Bool.true
-      let eqDiscrTrueExpr ← mkEq eqDiscrExpr trueExpr
-      let eqBVExprTrueExpr ← mkEq eqBVExpr trueExpr
-      let impExpr ← mkArrow eqDiscrTrueExpr eqBVExprTrueExpr
-      -- construct a `Decidable` instance for the implication using forall_prop_decidable
-      let decEqDiscrTrue := mkApp2 (mkConst ``instDecidableEqBool) eqDiscrExpr trueExpr
-      let decEqBVExprTrue := mkApp2 (mkConst ``instDecidableEqBool) eqBVExpr trueExpr
-      let impDecidable := mkApp4 (mkConst ``forall_prop_decidable)
-        eqDiscrTrueExpr
-        (.lam .anonymous eqDiscrTrueExpr eqBVExprTrueExpr .default)
-        decEqDiscrTrue
-        (.lam .anonymous eqDiscrTrueExpr decEqBVExprTrue .default)
-
-      let decideImpExpr := mkApp2 (mkConst ``Decidable.decide) impExpr impDecidable
-
       return mkApp4
         (mkConst ``Std.Tactic.BVDecide.Reflect.Bool.lemma_congr)
         decideImpExpr

src/Lean/Elab/Tactic/Injection.lean

@@ -40,7 +40,7 @@ private def tryAssumption (mvarId : MVarId) : MetaM (List MVarId) := do
   let ids := stx[1].getArgs.toList.map getNameOfIdent'
   liftMetaTactic fun mvarId => do
     match (← Meta.injections mvarId ids) with
-    | .solved                      => checkUnusedIds `injections mvarId ids; return []
-    | .subgoal mvarId' unusedIds _ => checkUnusedIds `injections mvarId unusedIds; tryAssumption mvarId'
+    | .solved                    => checkUnusedIds `injections mvarId ids; return []
+    | .subgoal mvarId' unusedIds => checkUnusedIds `injections mvarId unusedIds; tryAssumption mvarId'
 
 end Lean.Elab.Tactic

src/Lean/Elab/Term.lean

@@ -473,26 +473,6 @@ def withoutTacticReuse [Monad m] [MonadWithReaderOf Context m] [MonadOptions m]
       return !cond }
   }) act
 
-@[inherit_doc Core.wrapAsync]
-def wrapAsync (act : Unit → TermElabM α) : TermElabM (EIO Exception α) := do
-  let ctx ← read
-  let st ← get
-  let metaCtx ← readThe Meta.Context
-  let metaSt ← getThe Meta.State
-  Core.wrapAsync fun _ =>
-    act () |>.run ctx |>.run' st |>.run' metaCtx metaSt
-
-@[inherit_doc Core.wrapAsyncAsSnapshot]
-def wrapAsyncAsSnapshot (act : Unit → TermElabM Unit)
-    (desc : String := by exact decl_name%.toString) :
-    TermElabM (BaseIO Language.SnapshotTree) := do
-  let ctx ← read
-  let st ← get
-  let metaCtx ← readThe Meta.Context
-  let metaSt ← getThe Meta.State
-  Core.wrapAsyncAsSnapshot (desc := desc) fun _ =>
-    act () |>.run ctx |>.run' st |>.run' metaCtx metaSt
-
 abbrev TermElabResult (α : Type) := EStateM.Result Exception SavedState α
 
 /--

src/Lean/Language/Basic.lean

@@ -10,8 +10,9 @@ Authors: Sebastian Ullrich
 
 prelude
 import Init.System.Promise
+import Lean.Message
 import Lean.Parser.Types
-import Lean.Util.Trace
+import Lean.Elab.InfoTree
 
 set_option linter.missingDocs true
 
@@ -197,13 +198,32 @@ def withAlwaysResolvedPromises [Monad m] [MonadLiftT BaseIO m] [MonadFinally m]
   for asynchronously collecting information about the entirety of snapshots in the language server.
   The involved tasks may form a DAG on the `Task` dependency level but this is not captured by this
   data structure. -/
-structure SnapshotTree where
-  /-- The immediately available element of the snapshot tree node. -/
-  element : Snapshot
-  /-- The asynchronously available children of the snapshot tree node. -/
-  children : Array (SnapshotTask SnapshotTree)
+inductive SnapshotTree where
+  /-- Creates a snapshot tree node. -/
+  | mk (element : Snapshot) (children : Array (SnapshotTask SnapshotTree))
 deriving Inhabited
 
+/-- The immediately available element of the snapshot tree node. -/
+abbrev SnapshotTree.element : SnapshotTree → Snapshot
+  | mk s _ => s
+/-- The asynchronously available children of the snapshot tree node. -/
+abbrev SnapshotTree.children : SnapshotTree → Array (SnapshotTask SnapshotTree)
+  | mk _ children => children
+
+/-- Produces trace of given snapshot tree, synchronously waiting on all children. -/
+partial def SnapshotTree.trace (s : SnapshotTree) : CoreM Unit :=
+  go none s
+where go range? s := do
+  let file ← getFileMap
+  let mut desc := f!"{s.element.desc}"
+  if let some range := range? then
+    desc := desc ++ f!"{file.toPosition range.start}-{file.toPosition range.stop} "
+  desc := desc ++ .prefixJoin "\n• " (← s.element.diagnostics.msgLog.toList.mapM (·.toString))
+  if let some t := s.element.infoTree? then
+    trace[Elab.info] (← t.format)
+  withTraceNode `Elab.snapshotTree (fun _ => pure desc) do
+    s.children.toList.forM fun c => go c.range? c.get
+
 /--
   Helper class for projecting a heterogeneous hierarchy of snapshot classes to a homogeneous
   representation. -/
@@ -288,14 +308,6 @@ def SnapshotTree.runAndReport (s : SnapshotTree) (opts : Options) (json := false
 def SnapshotTree.getAll (s : SnapshotTree) : Array Snapshot :=
   s.forM (m := StateM _) (fun s => modify (·.push s)) |>.run #[] |>.2
 
-/-- Returns a task that waits on all snapshots in the tree. -/
-def SnapshotTree.waitAll : SnapshotTree → BaseIO (Task Unit)
-  | mk _ children => go children.toList
-where
-  go : List (SnapshotTask SnapshotTree) → BaseIO (Task Unit)
-    | [] => return .pure ()
-    | t::ts => BaseIO.bindTask t.task fun _ => go ts
-
 /-- Context of an input processing invocation. -/
 structure ProcessingContext extends Parser.InputContext
 

src/Lean/Language/Lean.lean

@@ -10,7 +10,6 @@ Authors: Sebastian Ullrich
 
 prelude
 import Lean.Language.Basic
-import Lean.Language.Util
 import Lean.Language.Lean.Types
 import Lean.Parser.Module
 import Lean.Elab.Import
@@ -167,6 +166,13 @@ namespace Lean.Language.Lean
 open Lean.Elab Command
 open Lean.Parser
 
+/-- Option for capturing output to stderr during elaboration. -/
+register_builtin_option stderrAsMessages : Bool := {
+  defValue := true
+  group    := "server"
+  descr    := "(server) capture output to the Lean stderr channel (such as from `dbg_trace`) during elaboration of a command as a diagnostic message"
+}
+
 /-- Lean-specific processing context. -/
 structure LeanProcessingContext extends ProcessingContext where
   /-- Position of the first file difference if there was a previous invocation. -/
@@ -513,7 +519,6 @@ where
         diagnostics := .empty, stx := .missing, parserState
         elabSnap := .pure <| .ofTyped { diagnostics := .empty : SnapshotLeaf }
         finishedSnap := .pure { diagnostics := .empty, cmdState }
-        reportSnap := default
         tacticCache := (← IO.mkRef {})
         nextCmdSnap? := none
       }
@@ -524,7 +529,6 @@ where
       -- definitely resolved in `doElab` task
       let elabPromise ← IO.Promise.new
       let finishedPromise ← IO.Promise.new
-      let reportPromise ← IO.Promise.new
       -- (Try to) use last line of command as range for final snapshot task. This ensures we do not
       -- retract the progress bar to a previous position in case the command support incremental
       -- reporting but has significant work after resolving its last incremental promise, such as
@@ -543,46 +547,22 @@ where
       let nextCmdSnap? := next?.map
         ({ range? := some ⟨parserState.pos, ctx.input.endPos⟩, task := ·.result })
       let diagnostics ← Snapshot.Diagnostics.ofMessageLog msgLog
-      let (stx', parserState') := if minimalSnapshots && !Parser.isTerminalCommand stx then
-        (default, default)
+      if minimalSnapshots && !Parser.isTerminalCommand stx then
+        prom.resolve {
+          diagnostics, finishedSnap, tacticCache, nextCmdSnap?
+          stx := .missing
+          parserState := {}
+          elabSnap := { range? := stx.getRange?, task := elabPromise.result }
+        }
       else
-        (stx, parserState)
-      prom.resolve {
-        diagnostics, finishedSnap, tacticCache, nextCmdSnap?
-        stx := stx', parserState := parserState'
-        elabSnap := { range? := stx.getRange?, task := elabPromise.result }
-        reportSnap := { range? := endRange?, task := reportPromise.result }
-      }
+        prom.resolve {
+          diagnostics, stx, parserState, tacticCache, nextCmdSnap?
+          elabSnap := { range? := stx.getRange?, task := elabPromise.result }
+          finishedSnap
+        }
       let cmdState ← doElab stx cmdState beginPos
         { old? := old?.map fun old => ⟨old.stx, old.elabSnap⟩, new := elabPromise }
         finishedPromise tacticCache ctx
-      let traceTask ←
-        if (← isTracingEnabledForCore `Elab.snapshotTree cmdState.scopes.head!.opts) then
-          -- We want to trace all of `CommandParsedSnapshot` but `traceTask` is part of it, so let's
-          -- create a temporary snapshot tree containing all tasks but it
-          let snaps := #[
-            { range? := none, task := elabPromise.result.map (sync := true) toSnapshotTree },
-            { range? := none, task := finishedPromise.result.map (sync := true) toSnapshotTree }] ++
-            cmdState.snapshotTasks
-          let tree := SnapshotTree.mk { diagnostics := .empty } snaps
-          BaseIO.bindTask (← tree.waitAll) fun _ => do
-            let .ok (_, s) ← EIO.toBaseIO <| tree.trace |>.run
-              { ctx with options := cmdState.scopes.head!.opts } { env := cmdState.env }
-              | pure <| .pure <| .mk { diagnostics := .empty } #[]
-            let mut msgLog := MessageLog.empty
-            for trace in s.traceState.traces do
-              msgLog := msgLog.add {
-                fileName := ctx.fileName
-                severity := MessageSeverity.information
-                pos      := ctx.fileMap.toPosition beginPos
-                data     := trace.msg
-              }
-            return .pure <| .mk { diagnostics := (← Snapshot.Diagnostics.ofMessageLog msgLog) } #[]
-        else
-          pure <| .pure <| .mk { diagnostics := .empty } #[]
-      reportPromise.resolve <|
-        .mk { diagnostics := .empty } <|
-          cmdState.snapshotTasks.push { range? := endRange?, task := traceTask }
       if let some next := next? then
         -- We're definitely off the fast-forwarding path now
         parseCmd none parserState cmdState next (sync := false) ctx
@@ -593,9 +573,7 @@ where
       LeanProcessingM Command.State := do
     let ctx ← read
     let scope := cmdState.scopes.head!
-    -- reset per-command state
-    let cmdStateRef ← IO.mkRef { cmdState with
-      messages := .empty, traceState := {}, snapshotTasks := #[] }
+    let cmdStateRef ← IO.mkRef { cmdState with messages := .empty, traceState := {} }
     /-
     The same snapshot may be executed by different tasks. So, to make sure `elabCommandTopLevel`
     has exclusive access to the cache, we create a fresh reference here. Before this change, the
@@ -610,8 +588,8 @@ where
       cancelTk?    := some ctx.newCancelTk
     }
     let (output, _) ←
-      IO.FS.withIsolatedStreams (isolateStderr := Core.stderrAsMessages.get scope.opts) do
-        EIO.toBaseIO do
+      IO.FS.withIsolatedStreams (isolateStderr := stderrAsMessages.get scope.opts) do
+        liftM (m := BaseIO) do
           withLoggingExceptions
             (getResetInfoTrees *> Elab.Command.elabCommandTopLevel stx)
             cmdCtx cmdStateRef

src/Lean/Language/Lean/Types.lean

@@ -46,8 +46,6 @@ structure CommandParsedSnapshot extends Snapshot where
   elabSnap : SnapshotTask DynamicSnapshot
   /-- State after processing is finished. -/
   finishedSnap : SnapshotTask CommandFinishedSnapshot
-  /-- Additional, untyped snapshots used for reporting, not reuse. -/
-  reportSnap : SnapshotTask SnapshotTree
   /-- Cache for `save`; to be replaced with incrementality. -/
   tacticCache : IO.Ref Tactic.Cache
   /-- Next command, unless this is a terminal command. -/
@@ -57,8 +55,7 @@ partial instance : ToSnapshotTree CommandParsedSnapshot where
   toSnapshotTree := go where
     go s := ⟨s.toSnapshot,
       #[s.elabSnap.map (sync := true) toSnapshotTree,
-        s.finishedSnap.map (sync := true) toSnapshotTree,
-        s.reportSnap] |>
+        s.finishedSnap.map (sync := true) toSnapshotTree] |>
         pushOpt (s.nextCmdSnap?.map (·.map (sync := true) go))⟩
 
 /-- State after successful importing. -/

src/Lean/Language/Util.lean

@@ -1,29 +0,0 @@
-/-
-Copyright (c) 2023 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-
-Additional snapshot functionality that needs further imports.
-
-Authors: Sebastian Ullrich
--/
-
-prelude
-import Lean.Language.Basic
-import Lean.CoreM
-import Lean.Elab.InfoTree
-
-namespace Lean.Language
-
-/-- Produces trace of given snapshot tree, synchronously waiting on all children. -/
-partial def SnapshotTree.trace (s : SnapshotTree) : CoreM Unit :=
-  go none s
-where go range? s := do
-  let file ← getFileMap
-  let mut desc := f!"{s.element.desc}"
-  if let some range := range? then
-    desc := desc ++ f!"{file.toPosition range.start}-{file.toPosition range.stop} "
-  desc := desc ++ .prefixJoin "\n• " (← s.element.diagnostics.msgLog.toList.mapM (·.toString))
-  if let some t := s.element.infoTree? then
-    trace[Elab.info] (← t.format)
-  withTraceNode `Elab.snapshotTree (fun _ => pure desc) do
-    s.children.toList.forM fun c => go c.range? c.get

src/Lean/Linter/Deprecated.lean

@@ -31,10 +31,6 @@ builtin_initialize deprecatedAttr : ParametricAttribute DeprecationEntry ←
       let newName? ← id?.mapM Elab.realizeGlobalConstNoOverloadWithInfo
       let text? := text?.map TSyntax.getString
       let since? := since?.map TSyntax.getString
-      if id?.isNone && text?.isNone then
-        logWarning "`[deprecated]` attribute should specify either a new name or a deprecation message"
-      if since?.isNone then
-        logWarning "`[deprecated]` attribute should specify the date or library version at which the deprecation was introduced, using `(since := \"...\")`"
       return { newName?, text?, since? }
   }
 
@@ -50,9 +46,7 @@ def getDeprecatedNewName (env : Environment) (declName : Name) : Option Name :=
 def checkDeprecated [Monad m] [MonadEnv m] [MonadLog m] [AddMessageContext m] [MonadOptions m] (declName : Name) : m Unit := do
   if getLinterValue linter.deprecated (← getOptions) then
     let some attr := deprecatedAttr.getParam? (← getEnv) declName | pure ()
-    logWarning <| .tagged ``deprecatedAttr <|
-      s!"`{declName}` has been deprecated" ++ match attr.text? with
-      | some text => s!": {text}"
-      | none => match attr.newName? with
-        | some newName => s!": use `{newName}` instead"
-        | none => ""
+    logWarning <| .tagged ``deprecatedAttr <| attr.text?.getD <|
+      match attr.newName? with
+      | none => s!"`{declName}` has been deprecated"
+      | some newName => s!"`{declName}` has been deprecated, use `{newName}` instead"

src/Lean/LocalContext.lean

@@ -406,8 +406,8 @@ def isSubPrefixOf (lctx₁ lctx₂ : LocalContext) (exceptFVars : Array Expr :=
 
 @[inline] def mkBinding (isLambda : Bool) (lctx : LocalContext) (xs : Array Expr) (b : Expr) : Expr :=
   let b := b.abstract xs
-  xs.size.foldRev (init := b) fun i _ b =>
-    let x := xs[i]
+  xs.size.foldRev (init := b) fun i b =>
+    let x := xs[i]!
     match lctx.findFVar? x with
     | some (.cdecl _ _ n ty bi _)  =>
       let ty := ty.abstractRange i xs;
@@ -457,7 +457,7 @@ def sanitizeNames (lctx : LocalContext) : StateM NameSanitizerState LocalContext
   let st ← get
   if !getSanitizeNames st.options then pure lctx else
     StateT.run' (s := ({} : NameSet)) <|
-      lctx.decls.size.foldRevM (init := lctx) fun i _ lctx => do
+      lctx.decls.size.foldRevM (init := lctx) fun i lctx => do
         match lctx.decls[i]! with
         | none      => pure lctx
         | some decl =>

src/Lean/Meta/Basic.lean

@@ -825,7 +825,7 @@ def mkFreshExprMVarWithId (mvarId : MVarId) (type? : Option Expr := none) (kind
     mkFreshExprMVarWithIdCore mvarId type kind userName
 
 def mkFreshLevelMVars (num : Nat) : MetaM (List Level) :=
-  num.foldM (init := []) fun _ _ us =>
+  num.foldM (init := []) fun _ us =>
     return (← mkFreshLevelMVar)::us
 
 def mkFreshLevelMVarsFor (info : ConstantInfo) : MetaM (List Level) :=

src/Lean/Meta/Closure.lean

@@ -286,8 +286,8 @@ partial def process : ClosureM Unit := do
 @[inline] def mkBinding (isLambda : Bool) (decls : Array LocalDecl) (b : Expr) : Expr :=
   let xs := decls.map LocalDecl.toExpr
   let b  := b.abstract xs
-  decls.size.foldRev (init := b) fun i _ b =>
-    let decl := decls[i]
+  decls.size.foldRev (init := b) fun i b =>
+    let decl := decls[i]!
     match decl with
     | .cdecl _ _ n ty bi _ =>
       let ty := ty.abstractRange i xs

src/Lean/Meta/IndPredBelow.lean

@@ -152,7 +152,7 @@ where
     let run (x : StateRefT Nat MetaM Expr) : MetaM (Expr × Nat) := StateRefT'.run x 0
     let (_, cnt) ← run <| transform domain fun e => do
       if let some name := e.constName? then
-        if ctx.typeInfos.any fun indVal => indVal.name == name then
+        if let some _ := ctx.typeInfos.findIdx? fun indVal => indVal.name == name then
           modify (· + 1)
       return .continue
 

src/Lean/Meta/LazyDiscrTree.lean

@@ -566,9 +566,9 @@ Append results to array
 partial def appendResultsAux (mr : MatchResult α) (a : Array β) (f : Nat → α → β) : Array β :=
   let aa := mr.elts
   let n := aa.size
-  Nat.fold (n := n) (init := a) fun i _ r =>
+  Nat.fold (n := n) (init := a) fun i r =>
     let j := n-1-i
-    let b := aa[j]
+    let b := aa[j]!
     b.foldl (init := r) (· ++ ·.map (f j))
 
 partial def appendResults (mr : MatchResult α) (a : Array α) : Array α :=

src/Lean/Meta/Match/Match.lean

@@ -882,7 +882,7 @@ def mkMatcher (input : MkMatcherInput) (exceptionIfContainsSorry := false) : Met
       | none => pure ()
 
     trace[Meta.Match.debug] "matcher: {matcher}"
-    let unusedAltIdxs := lhss.length.fold (init := []) fun i _ r =>
+    let unusedAltIdxs := lhss.length.fold (init := []) fun i r =>
       if s.used.contains i then r else i::r
     return {
       matcher,

src/Lean/Meta/Match/MatchEqs.lean

@@ -222,16 +222,16 @@ private def contradiction (mvarId : MVarId) : MetaM Bool :=
   Auxiliary tactic that tries to replace as many variables as possible and then apply `contradiction`.
   We use it to discard redundant hypotheses.
 -/
-partial def trySubstVarsAndContradiction (mvarId : MVarId) (forbidden : FVarIdSet := {}) : MetaM Bool :=
+partial def trySubstVarsAndContradiction (mvarId : MVarId) : MetaM Bool :=
   commitWhen do
     let mvarId ← substVars mvarId
-    match (← injections mvarId (forbidden := forbidden)) with
+    match (← injections mvarId) with
     | .solved => return true -- closed goal
-    | .subgoal mvarId' _ forbidden =>
+    | .subgoal mvarId' _ =>
       if mvarId' == mvarId then
         contradiction mvarId
       else
-        trySubstVarsAndContradiction mvarId' forbidden
+        trySubstVarsAndContradiction mvarId'
 
 private def processNextEq : M Bool := do
   let s ← get
@@ -375,8 +375,7 @@ private partial def withSplitterAlts (altTypes : Array Expr) (f : Array Expr →
 inductive InjectionAnyResult where
   | solved
   | failed
-  /-- `fvarId` refers to the local declaration selected for the application of the `injection` tactic. -/
-  | subgoal (fvarId : FVarId) (mvarId : MVarId)
+  | subgoal (mvarId : MVarId)
 
 private def injectionAnyCandidate? (type : Expr) : MetaM (Option (Expr × Expr)) := do
   if let some (_, lhs, rhs) ← matchEq? type then
@@ -386,28 +385,21 @@ private def injectionAnyCandidate? (type : Expr) : MetaM (Option (Expr × Expr))
       return some (lhs, rhs)
   return none
 
-/--
-Try applying `injection` to a local declaration that is not in `forbidden`.
-
-We use `forbidden` because the `injection` tactic might fail to clear the variable if there are forward dependencies.
-See `proveSubgoalLoop` for additional details.
--/
-private def injectionAny (mvarId : MVarId) (forbidden : FVarIdSet := {}) : MetaM InjectionAnyResult := do
+private def injectionAny (mvarId : MVarId) : MetaM InjectionAnyResult := do
   mvarId.withContext do
     for localDecl in (← getLCtx) do
-      unless forbidden.contains localDecl.fvarId do
-        if let some (lhs, rhs) ← injectionAnyCandidate? localDecl.type then
-          unless (← isDefEq lhs rhs) do
-            let lhs ← whnf lhs
-            let rhs ← whnf rhs
-            unless lhs.isRawNatLit && rhs.isRawNatLit do
-              try
-                match (← injection mvarId localDecl.fvarId) with
-                | InjectionResult.solved  => return InjectionAnyResult.solved
-                | InjectionResult.subgoal mvarId .. => return InjectionAnyResult.subgoal localDecl.fvarId mvarId
-              catch ex =>
-                trace[Meta.Match.matchEqs] "injectionAnyFailed at {localDecl.userName}, error\n{ex.toMessageData}"
-                pure ()
+      if let some (lhs, rhs) ← injectionAnyCandidate? localDecl.type then
+        unless (← isDefEq lhs rhs) do
+          let lhs ← whnf lhs
+          let rhs ← whnf rhs
+          unless lhs.isRawNatLit && rhs.isRawNatLit do
+            try
+              match (← injection mvarId localDecl.fvarId) with
+              | InjectionResult.solved  => return InjectionAnyResult.solved
+              | InjectionResult.subgoal mvarId .. => return InjectionAnyResult.subgoal mvarId
+            catch ex =>
+              trace[Meta.Match.matchEqs] "injectionAnyFailed at {localDecl.userName}, error\n{ex.toMessageData}"
+              pure ()
     return InjectionAnyResult.failed
 
 
@@ -609,32 +601,27 @@ where
         let eNew := mkAppN eNew mvars
         return TransformStep.done eNew
 
-  /-
-  `forbidden` tracks variables that we have already applied `injection`.
-  Recall that the `injection` tactic may not be able to eliminate them when
-  they have forward dependencies.
-  -/
-  proveSubgoalLoop (mvarId : MVarId) (forbidden : FVarIdSet) : MetaM Unit := do
+  proveSubgoalLoop (mvarId : MVarId) : MetaM Unit := do
     trace[Meta.Match.matchEqs] "proveSubgoalLoop\n{mvarId}"
     if (← mvarId.contradictionQuick) then
       return ()
-    match (← injectionAny mvarId forbidden) with
-    | .solved => return ()
-    | .failed =>
+    match (← injectionAny mvarId) with
+    | InjectionAnyResult.solved => return ()
+    | InjectionAnyResult.failed =>
       let mvarId' ← substVars mvarId
       if mvarId' == mvarId then
         if (← mvarId.contradictionCore {}) then
           return ()
         throwError "failed to generate splitter for match auxiliary declaration '{matchDeclName}', unsolved subgoal:\n{MessageData.ofGoal mvarId}"
       else
-        proveSubgoalLoop mvarId' forbidden
-    | .subgoal fvarId mvarId => proveSubgoalLoop mvarId (forbidden.insert fvarId)
+        proveSubgoalLoop mvarId'
+    | InjectionAnyResult.subgoal mvarId => proveSubgoalLoop mvarId
 
   proveSubgoal (mvarId : MVarId) : MetaM Unit := do
     trace[Meta.Match.matchEqs] "subgoal {mkMVar mvarId}, {repr (← mvarId.getDecl).kind}, {← mvarId.isAssigned}\n{MessageData.ofGoal mvarId}"
     let (_, mvarId) ← mvarId.intros
     let mvarId ← mvarId.tryClearMany (alts.map (·.fvarId!))
-    proveSubgoalLoop mvarId {}
+    proveSubgoalLoop mvarId
 
 /--
   Create new alternatives (aka minor premises) by replacing `discrs` with `patterns` at `alts`.
@@ -659,7 +646,7 @@ where
 /--
   Create conditional equations and splitter for the given match auxiliary declaration. -/
 private partial def mkEquationsFor (matchDeclName : Name) :  MetaM MatchEqns := withLCtx {} {} do
-  withTraceNode `Meta.Match.matchEqs (fun _ => return m!"mkEquationsFor '{matchDeclName}'") do
+  trace[Meta.Match.matchEqs] "mkEquationsFor '{matchDeclName}'"
   withConfig (fun c => { c with etaStruct := .none }) do
   /-
   Remark: user have requested the `split` tactic to be available for writing code.

src/Lean/Meta/Match/MatcherApp/Transform.lean

@@ -59,9 +59,9 @@ def addArg (matcherApp : MatcherApp) (e : Expr) : MetaM MatcherApp :=
       -- This error can only happen if someone implemented a transformation that rewrites the motive created by `mkMatcher`.
       throwError "unexpected matcher application, motive must be lambda expression with #{matcherApp.discrs.size} arguments"
     let eType ← inferType e
-    let eTypeAbst ← matcherApp.discrs.size.foldRevM (init := eType) fun i _ eTypeAbst => do
+    let eTypeAbst ← matcherApp.discrs.size.foldRevM (init := eType) fun i eTypeAbst => do
       let motiveArg := motiveArgs[i]!
-      let discr     := matcherApp.discrs[i]
+      let discr     := matcherApp.discrs[i]!
       let eTypeAbst ← kabstract eTypeAbst discr
       return eTypeAbst.instantiate1 motiveArg
     let motiveBody ← mkArrow eTypeAbst motiveBody
@@ -118,9 +118,9 @@ def refineThrough (matcherApp : MatcherApp) (e : Expr) : MetaM (Array Expr) :=
       -- This error can only happen if someone implemented a transformation that rewrites the motive created by `mkMatcher`.
       throwError "failed to transfer argument through matcher application, motive must be lambda expression with #{matcherApp.discrs.size} arguments"
 
-    let eAbst ← matcherApp.discrs.size.foldRevM (init := e) fun i _ eAbst => do
+    let eAbst ← matcherApp.discrs.size.foldRevM (init := e) fun i eAbst => do
       let motiveArg := motiveArgs[i]!
-      let discr     := matcherApp.discrs[i]
+      let discr     := matcherApp.discrs[i]!
       let eTypeAbst ← kabstract eAbst discr
       return eTypeAbst.instantiate1 motiveArg
     -- Let's create something that’s a `Sort` and mentions `e`

src/Lean/Meta/Tactic/Apply.lean

@@ -104,8 +104,8 @@ def appendParentTag (mvarId : MVarId) (newMVars : Array Expr) (binderInfos : Arr
     newMVars[0]!.mvarId!.setTag parentTag
   else
     unless parentTag.isAnonymous do
-      newMVars.size.forM fun i _ => do
-        let mvarIdNew := newMVars[i].mvarId!
+      newMVars.size.forM fun i => do
+        let mvarIdNew := newMVars[i]!.mvarId!
         unless (← mvarIdNew.isAssigned) do
           unless binderInfos[i]!.isInstImplicit do
             let currTag ← mvarIdNew.getTag

src/Lean/Meta/Tactic/Cases.lean

@@ -168,7 +168,7 @@ private def hasIndepIndices (ctx : Context) : MetaM Bool := do
   else if ctx.majorTypeIndices.any fun idx => !idx.isFVar then
     /- One of the indices is not a free variable. -/
     return false
-  else if ctx.majorTypeIndices.size.any fun i _ => i.any fun j _ => ctx.majorTypeIndices[i] == ctx.majorTypeIndices[j] then
+  else if ctx.majorTypeIndices.size.any fun i => i.any fun j => ctx.majorTypeIndices[i]! == ctx.majorTypeIndices[j]! then
     /- An index occurs more than once -/
     return false
   else

src/Lean/Meta/Tactic/FunInd.lean

@@ -283,9 +283,9 @@ partial def foldAndCollect (oldIH newIH : FVarId) (isRecCall : Expr → Option E
           (onMotive := fun xs _body => do
             -- Remove the old IH that was added in mkFix
             let eType ← newIH.getType
-            let eTypeAbst ← matcherApp.discrs.size.foldRevM (init := eType) fun i _ eTypeAbst => do
+            let eTypeAbst ← matcherApp.discrs.size.foldRevM (init := eType) fun i eTypeAbst => do
               let motiveArg := xs[i]!
-              let discr     := matcherApp.discrs[i]
+              let discr     := matcherApp.discrs[i]!
               let eTypeAbst ← kabstract eTypeAbst discr
               return eTypeAbst.instantiate1 motiveArg
 

src/Lean/Meta/Tactic/Induction.lean

@@ -105,10 +105,10 @@ private partial def finalize
             let mvarId' ← mvar.mvarId!.tryClear major.fvarId!
             let (fields, mvarId') ←  mvarId'.introN nparams minorGivenNames.varNames (useNamesForExplicitOnly := !minorGivenNames.explicit)
             let (extra,  mvarId') ← mvarId'.introNP nextra
-            let subst := reverted.size.fold (init := baseSubst) fun i _ (subst : FVarSubst) =>
+            let subst := reverted.size.fold (init := baseSubst) fun i (subst : FVarSubst) =>
               if i < indices.size + 1 then subst
               else
-                let revertedFVarId := reverted[i]
+                let revertedFVarId := reverted[i]!
                 let newFVarId      := extra[i - indices.size - 1]!
                 subst.insert revertedFVarId (mkFVar newFVarId)
             let fields := fields.map mkFVar
@@ -134,8 +134,8 @@ def getMajorTypeIndices (mvarId : MVarId) (tacticName : Name) (recursorInfo : Re
     if idxPos ≥ majorTypeArgs.size then throwTacticEx tacticName mvarId m!"major premise type is ill-formed{indentExpr majorType}"
     let idx := majorTypeArgs.get! idxPos
     unless idx.isFVar do throwTacticEx tacticName mvarId m!"major premise type index {idx} is not a variable{indentExpr majorType}"
-    majorTypeArgs.size.forM fun i _ => do
-      let arg := majorTypeArgs[i]
+    majorTypeArgs.size.forM fun i => do
+      let arg := majorTypeArgs[i]!
       if i != idxPos && arg == idx then
         throwTacticEx tacticName mvarId m!"'{idx}' is an index in major premise, but it occurs more than once{indentExpr majorType}"
       if i < idxPos then

src/Lean/Meta/Tactic/Injection.lean

@@ -94,48 +94,31 @@ def injection (mvarId : MVarId) (fvarId : FVarId) (newNames : List Name := []) :
   | .subgoal mvarId numEqs => injectionIntro mvarId numEqs newNames
 
 inductive InjectionsResult where
-  /-- `injections` closed the input goal. -/
   | solved
-  /--
-  `injections` produces a new goal `mvarId`. `remainingNames` contains the user-facing names that have not been used.
-  `forbidden` contains all local declarations to which `injection` has been applied.
-  Recall that some of these declarations may not have been eliminated from the local context due to forward dependencies, and
-  we use `forbidden` to avoid non-termination when using `injections` in a loop.
-  -/
-  | subgoal (mvarId : MVarId) (remainingNames : List Name) (forbidden : FVarIdSet)
+  | subgoal (mvarId : MVarId) (remainingNames : List Name)
 
-/--
-Applies `injection` to local declarations in `mvarId`. It uses `newNames` to name the new local declarations.
-`maxDepth` is the maximum recursion depth. Only local declarations that are not in `forbidden` are considered.
-Recall that some of local declarations may not have been eliminated from the local context due to forward dependencies, and
-we use `forbidden` to avoid non-termination when using `injections` in a loop.
--/
-partial def injections (mvarId : MVarId) (newNames : List Name := []) (maxDepth : Nat := 5) (forbidden : FVarIdSet := {}) : MetaM InjectionsResult :=
+partial def injections (mvarId : MVarId) (newNames : List Name := []) (maxDepth : Nat := 5) : MetaM InjectionsResult :=
   mvarId.withContext do
     let fvarIds := (← getLCtx).getFVarIds
-    go maxDepth fvarIds.toList mvarId newNames forbidden
+    go maxDepth fvarIds.toList mvarId newNames
 where
-  go (depth : Nat) (fvarIds : List FVarId) (mvarId : MVarId) (newNames : List Name) (forbidden : FVarIdSet) : MetaM InjectionsResult := do
-    match depth, fvarIds with
-    | 0,   _                 => throwTacticEx `injections mvarId "recursion depth exceeded"
-    | _,   []                => return .subgoal mvarId newNames forbidden
-    | d+1, fvarId :: fvarIds => do
+  go : Nat → List FVarId → MVarId → List Name → MetaM InjectionsResult
+    | 0,   _,  _,      _        => throwTacticEx `injections mvarId "recursion depth exceeded"
+    | _,   [], mvarId, newNames => return .subgoal mvarId newNames
+    | d+1, fvarId :: fvarIds, mvarId, newNames => do
       let cont := do
-        go (d+1) fvarIds mvarId newNames forbidden
-      if forbidden.contains fvarId then
-        cont
-      else if let some (_, lhs, rhs) ← matchEqHEq? (← fvarId.getType) then
+        go (d+1) fvarIds mvarId newNames
+      if let some (_, lhs, rhs) ← matchEqHEq? (← fvarId.getType) then
         let lhs ← whnf lhs
         let rhs ← whnf rhs
-        if lhs.isRawNatLit && rhs.isRawNatLit then
-          cont
+        if lhs.isRawNatLit && rhs.isRawNatLit then cont
         else
           try
             commitIfNoEx do
               match (← injection mvarId fvarId newNames) with
               | .solved  => return .solved
               | .subgoal mvarId newEqs remainingNames =>
-                mvarId.withContext <| go d (newEqs.toList ++ fvarIds) mvarId remainingNames (forbidden.insert fvarId)
+                mvarId.withContext <| go d (newEqs.toList ++ fvarIds) mvarId remainingNames
           catch _ => cont
       else cont
 

src/Lean/Meta/Tactic/Revert.lean

@@ -43,7 +43,6 @@ def _root_.Lean.MVarId.revert (mvarId : MVarId) (fvarIds : Array FVarId) (preser
       finally
         mvarId.setKind .syntheticOpaque
     let mvar := e.getAppFn
-    mvar.mvarId!.setKind .syntheticOpaque
     mvar.mvarId!.setTag tag
     return (toRevert.map Expr.fvarId!, mvar.mvarId!)
 

src/Lean/Meta/Tactic/Rewrite.lean

@@ -45,26 +45,12 @@ def _root_.Lean.MVarId.rewrite (mvarId : MVarId) (e : Expr) (heq : Expr)
           let eNew ← instantiateMVars eNew
           let eType ← inferType e
           let motive := Lean.mkLambda `_a BinderInfo.default α eAbst
-          try
-            check motive
-          catch ex =>
-            throwTacticEx `rewrite mvarId m!"\
-              motive is not type correct:{indentD motive}\nError: {ex.toMessageData}\
-              \n\n\
-              Explanation: The rewrite tactic rewrites an expression 'e' using an equality 'a = b' by the following process. \
-              First, it looks for all 'a' in 'e'. Second, it tries to abstract these occurrences of 'a' to create a function 'm := fun _a => ...', called the *motive*, \
-              with the property that 'm a' is definitionally equal to 'e'. \
-              Third, we observe that '{.ofConstName ``congrArg}' implies that 'm a = m b', which can be used with lemmas such as '{.ofConstName ``Eq.mpr}' to change the goal. \
-              However, if 'e' depends on specific properties of 'a', then the motive 'm' might not typecheck.\
-              \n\n\
-              Possible solutions: use rewrite's 'occs' configuration option to limit which occurrences are rewritten, \
-              or use 'simp' or 'conv' mode, which have strategies for certain kinds of dependencies \
-              (these tactics can handle proofs and '{.ofConstName ``Decidable}' instances whose types depend on the rewritten term, \
-              and 'simp' can apply user-defined '@[congr]' theorems as well)."
+          unless (← isTypeCorrect motive) do
+            throwTacticEx `rewrite mvarId "motive is not type correct"
           unless (← withLocalDeclD `_a α fun a => do isDefEq (← inferType (eAbst.instantiate1 a)) eType) do
             -- NB: using motive.arrow? would disallow motives where the dependency
             -- can be reduced away
-            throwTacticEx `rewrite mvarId m!"motive is dependent{indentD motive}"
+            throwTacticEx `rewrite mvarId "motive is dependent"
           let u1 ← getLevel α
           let u2 ← getLevel eType
           let eqPrf := mkApp6 (.const ``congrArg [u1, u2]) α eType lhs rhs motive heq

src/Lean/Meta/Tactic/Simp/Main.lean

@@ -571,127 +571,10 @@ def congr (e : Expr) : SimpM Result := do
   else
     congrDefault e
 
-/--
-Returns `true` if `e` is of the form `@letFun _ (fun _ => β) _ _`
-
-`β` must not contain loose bound variables. Recall that `simp` does not have support for `let_fun`s
-where resulting type depends on the `let`-value. Example:
-```
-let_fun n := 10;
-BitVec.zero n
-```
--/
-def isNonDepLetFun (e : Expr) : Bool :=
-  let_expr letFun _ beta _ body := e | false
-  beta.isLambda && !beta.bindingBody!.hasLooseBVars && body.isLambda
-
-/--
-Auxiliary structure used to represent the return value of `simpNonDepLetFun.go`.
--/
-private structure SimpLetFunResult where
-  /--
-  The simplified expression. Note that is may contain loose bound variables.
-  `simpNonDepLetFun.go` attempts to minimize the quadratic overhead imposed
-  by the locally nameless discipline in a sequence of `let_fun` declarations.
-  -/
-  expr     : Expr
-  /--
-  The proof that the simplified expression is equal to the input one.
-  It may containt loose bound variables. See `expr` field.
-  -/
-  proof    : Expr
-  /--
-  `modified := false` iff `expr` is structurally equal to the input expression.
-  -/
-  modified : Bool
-
-/--
-Simplifies a sequence of `let_fun` declarations.
-It attempts to minimize the quadratic overhead imposed by
-the locally nameless discipline.
--/
-partial def simpNonDepLetFun (e : Expr) : SimpM Result := do
-  let rec go (xs : Array Expr) (e : Expr) : SimpM SimpLetFunResult := do
-    /-
-    Helper function applied when `e` is not a `let_fun` or
-    is a non supported `let_fun` (e.g., the resulting type depends on the value).
-    -/
-    let stop : SimpM SimpLetFunResult := do
-      let e := e.instantiateRev xs
-      let r ← simp e
-      return { expr := r.expr.abstract xs, proof := (← r.getProof).abstract xs, modified :=  r.expr != e }
-    let_expr f@letFun alpha betaFun val body := e | stop
-    let us := f.constLevels!
-    let [_, v] := us | stop
-    /-
-    Recall that `let_fun x : α := val; e[x]` is encoded at
-    ```
-    @letFun α (fun x : α => β[x]) val (fun x : α => e[x])
-    ```
-    `betaFun` is `(fun x : α => β[x])`. If `β[x]` does not have loose bound variables then the resulting type
-    does not depend on the value since it does not depend on `x`.
-
-    We also check whether `alpha` does not depend on the previous `let_fun`s in the sequence.
-    This check is just to make the code simpler. It is not common to have a type depending on the value of a previous `let_fun`.
-    -/
-    if alpha.hasLooseBVars || !betaFun.isLambda || !body.isLambda || betaFun.bindingBody!.hasLooseBVars then
-      stop
-    else if !body.bindingBody!.hasLooseBVar 0 then
-      /-
-      Redundant `let_fun`. The simplifier will remove it.
-      Remark: the `hasLooseBVar` check here may introduce a quadratic overhead in the worst case.
-      If observe that in practice, we may use a separate step for removing unused variables.
-
-      Remark: note that we do **not** simplify the value in this case.
-      -/
-      let x := mkConst `__no_used_dummy__ -- dummy value
-      let { expr, proof, .. } ← go (xs.push x) body.bindingBody!
-      let proof := mkApp6 (mkConst ``letFun_unused us) alpha betaFun.bindingBody! val body.bindingBody! expr proof
-      return { expr, proof, modified := true }
-    else
-      let beta    := betaFun.bindingBody!
-      let valInst := val.instantiateRev xs
-      let valResult ← simp valInst
-      withLocalDecl body.bindingName! body.bindingInfo! alpha fun x => do
-        let valIsNew := valResult.expr != valInst
-        let { expr, proof, modified := bodyIsNew } ← go (xs.push x) body.bindingBody!
-        if !valIsNew && !bodyIsNew then
-          /-
-          Value and body were not simplified. We just return `e` and a new refl proof.
-          We must use the low-level `Expr` APIs because `e` may contain loose bound variables.
-          -/
-          let proof := mkApp2 (mkConst ``Eq.refl [v]) beta e
-          return { expr := e, proof, modified := false }
-        else
-          let body' := mkLambda body.bindingName! body.bindingInfo! alpha expr
-          let val'  := valResult.expr.abstract xs
-          let e'    := mkApp4 f alpha betaFun val' body'
-          if valIsNew && bodyIsNew then
-            -- Value and body were simplified
-            let valProof := (← valResult.getProof).abstract xs
-            let proof := mkApp8 (mkConst ``letFun_congr us) alpha beta val val' body body' valProof (mkLambda body.bindingName! body.bindingInfo! alpha proof)
-            return { expr := e', proof, modified := true }
-          else if valIsNew then
-            -- Only the value was simplified.
-            let valProof := (← valResult.getProof).abstract xs
-            let proof := mkApp6 (mkConst ``letFun_val_congr us) alpha beta val val' body valProof
-            return { expr := e', proof, modified := true }
-          else
-            -- Only the body was simplified.
-            let proof := mkApp6 (mkConst ``letFun_body_congr us) alpha beta val body body' (mkLambda body.bindingName! body.bindingInfo! alpha proof)
-            return { expr := e', proof, modified := true }
-  let { expr, proof, modified } ← go #[] e
-  if !modified then
-    return { expr := e }
-  else
-    return { expr, proof? := proof }
-
 def simpApp (e : Expr) : SimpM Result := do
   if isOfNatNatLit e || isOfScientificLit e || isCharLit e then
     -- Recall that we fold "orphan" kernel Nat literals `n` into `OfNat.ofNat n`
     return { expr := e }
-  else if isNonDepLetFun e then
-    simpNonDepLetFun e
   else
     congr e
 

src/Lean/Meta/Tactic/Simp/Types.lean

@@ -146,8 +146,12 @@ def mkContext (config : Config := {}) (simpTheorems : SimpTheoremsArray := {}) (
     indexConfig := mkIndexConfig config
   }
 
-def Context.setConfig (context : Context) (config : Config) : Context :=
-  { context with config }
+def Context.setConfig (context : Context) (config : Config) : MetaM Context := do
+  return { context with
+    config
+    metaConfig := (← mkMetaConfig config)
+    indexConfig := (← mkIndexConfig config)
+  }
 
 def Context.setSimpTheorems (c : Context) (simpTheorems : SimpTheoremsArray) : Context :=
   { c with simpTheorems }

src/Lean/Meta/Tactic/Subst.lean

@@ -80,9 +80,9 @@ def substCore (mvarId : MVarId) (hFVarId : FVarId) (symm := false) (fvarSubst :
                   pure mvarId
                 let (newFVars, mvarId) ← mvarId.introNP (vars.size - 2)
                 trace[Meta.Tactic.subst] "after intro rest {vars.size - 2} {MessageData.ofGoal mvarId}"
-                let fvarSubst ← newFVars.size.foldM (init := fvarSubst) fun i _ (fvarSubst : FVarSubst) =>
+                let fvarSubst ← newFVars.size.foldM (init := fvarSubst) fun i (fvarSubst : FVarSubst) =>
                     let var     := vars[i+2]!
-                    let newFVar := newFVars[i]
+                    let newFVar := newFVars[i]!
                     pure $ fvarSubst.insert var (mkFVar newFVar)
                 let fvarSubst := fvarSubst.insert aFVarIdOriginal (if clearH then b else mkFVar aFVarId)
                 let fvarSubst := fvarSubst.insert hFVarIdOriginal (mkFVar hFVarId)

src/Lean/MetavarContext.lean

@@ -979,10 +979,10 @@ def collectForwardDeps (lctx : LocalContext) (toRevert : Array Expr) : M (Array
   else
     if (← preserveOrder) then
       -- Make sure toRevert[j] does not depend on toRevert[i] for j < i
-      toRevert.size.forM fun i _ => do
-        let fvar := toRevert[i]
-        i.forM fun j _ => do
-          let prevFVar := toRevert[j]
+      toRevert.size.forM fun i => do
+        let fvar := toRevert[i]!
+        i.forM fun j => do
+          let prevFVar := toRevert[j]!
           let prevDecl := lctx.getFVar! prevFVar
           if (← localDeclDependsOn prevDecl fvar.fvarId!) then
             throw (Exception.revertFailure (← getMCtx) lctx toRevert prevDecl.userName.toString)
@@ -990,7 +990,7 @@ def collectForwardDeps (lctx : LocalContext) (toRevert : Array Expr) : M (Array
     let firstDeclToVisit := getLocalDeclWithSmallestIdx lctx toRevert
     let initSize         := newToRevert.size
     lctx.foldlM (init := newToRevert) (start := firstDeclToVisit.index) fun (newToRevert : Array Expr) decl => do
-      if initSize.any fun i _ => decl.fvarId == newToRevert[i]!.fvarId! then
+      if initSize.any fun i => decl.fvarId == newToRevert[i]!.fvarId! then
         return newToRevert
       else if toRevert.any fun x => decl.fvarId == x.fvarId! then
         return newToRevert.push decl.toExpr
@@ -1061,8 +1061,8 @@ mutual
   -/
   private partial def mkAuxMVarType (lctx : LocalContext) (xs : Array Expr) (kind : MetavarKind) (e : Expr) (usedLetOnly : Bool) : M Expr := do
     let e ← abstractRangeAux xs xs.size e
-    xs.size.foldRevM (init := e) fun i _ e => do
-      let x := xs[i]
+    xs.size.foldRevM (init := e) fun i e => do
+      let x := xs[i]!
       if x.isFVar then
         match lctx.getFVar! x with
         | LocalDecl.cdecl _ _ n type bi _ =>
@@ -1231,8 +1231,8 @@ private def mkLambda' (x : Name) (bi : BinderInfo) (t : Expr) (b : Expr) (etaRed
   If `usedLetOnly == true` then `let` expressions are created only for used (let-) variables. -/
 def mkBinding (isLambda : Bool) (lctx : LocalContext) (xs : Array Expr) (e : Expr) (usedOnly : Bool) (usedLetOnly : Bool) (etaReduce : Bool) : M Expr := do
   let e ← abstractRange xs xs.size e
-  xs.size.foldRevM (init := e) fun i _ e => do
-      let x := xs[i]
+  xs.size.foldRevM (init := e) fun i e => do
+      let x := xs[i]!
       if x.isFVar then
         match lctx.getFVar! x with
         | LocalDecl.cdecl _ _ n type bi _ =>

src/Lean/PrettyPrinter.lean

@@ -91,12 +91,9 @@ open Delaborator in
 /-- Pretty-prints a declaration `c` as `c.{<levels>} <params> : <type>`. -/
 def ppSignature (c : Name) : MetaM FormatWithInfos := do
   let decl ← getConstInfo c
-  let e := Expr.const c (decl.levelParams.map mkLevelParam)
-  if pp.raw.get (← getOptions) then
-    return s!"{e} : {decl.type}"
-  else
-    let (stx, infos) ← delabCore e (delab := delabConstWithSignature)
-    return ⟨← ppTerm ⟨stx⟩, infos⟩  -- HACK: not a term
+  let e := .const c (decl.levelParams.map mkLevelParam)
+  let (stx, infos) ← delabCore e (delab := delabConstWithSignature)
+  return ⟨← ppTerm ⟨stx⟩, infos⟩  -- HACK: not a term
 
 private partial def noContext : MessageData → MessageData
   | MessageData.withContext _   msg => noContext msg

src/Lean/PrettyPrinter/Delaborator/Builtins.lean

@@ -1115,18 +1115,17 @@ def coeDelaborator : Delab := whenPPOption getPPCoercions do
     delabAppCore nargs (delabHead info nargs) (unexpand := false)
 where
   delabHead (info : CoeFnInfo) (nargs : Nat) (insertExplicit : Bool) : Delab := do
-    withTypeAscription (cond := ← getPPOption getPPCoercionsTypes) do
-      guard <| !insertExplicit
-      if info.type == .coeFun && nargs > 0 then
-        -- In the CoeFun case, annotate with the coercee itself.
-        -- We can still see the whole coercion expression by hovering over the whitespace between the arguments.
-        withNaryArg info.coercee <| withAnnotateTermInfo delab
-      else
-        withAnnotateTermInfo do
-          match info.type with
-          | .coe     => `(↑$(← withNaryArg info.coercee delab))
-          | .coeFun  => `(⇑$(← withNaryArg info.coercee delab))
-          | .coeSort => `(↥$(← withNaryArg info.coercee delab))
+    guard <| !insertExplicit
+    if info.type == .coeFun && nargs > 0 then
+      -- In the CoeFun case, annotate with the coercee itself.
+      -- We can still see the whole coercion expression by hovering over the whitespace between the arguments.
+      withNaryArg info.coercee <| withAnnotateTermInfo delab
+    else
+      withAnnotateTermInfo do
+        match info.type with
+        | .coe     => `(↑$(← withNaryArg info.coercee delab))
+        | .coeFun  => `(⇑$(← withNaryArg info.coercee delab))
+        | .coeSort => `(↥$(← withNaryArg info.coercee delab))
 
 @[builtin_delab app.dite]
 def delabDIte : Delab := whenNotPPOption getPPExplicit <| whenPPOption getPPNotation <| withOverApp 5 do

src/Lean/PrettyPrinter/Delaborator/Options.lean

@@ -44,11 +44,6 @@ register_builtin_option pp.coercions : Bool := {
   group    := "pp"
   descr    := "(pretty printer) hide coercion applications"
 }
-register_builtin_option pp.coercions.types : Bool := {
-  defValue := false
-  group    := "pp"
-  descr    := "(pretty printer) display coercion applications with a type ascription"
-}
 register_builtin_option pp.universes : Bool := {
   defValue := false
   group    := "pp"
@@ -256,7 +251,6 @@ def getPPLetVarTypes (o : Options) : Bool := o.get pp.letVarTypes.name (getPPAll
 def getPPNumericTypes (o : Options) : Bool := o.get pp.numericTypes.name pp.numericTypes.defValue
 def getPPNatLit (o : Options) : Bool := o.get pp.natLit.name (getPPNumericTypes o && !getPPAll o)
 def getPPCoercions (o : Options) : Bool := o.get pp.coercions.name (!getPPAll o)
-def getPPCoercionsTypes (o : Options) : Bool := o.get pp.coercions.types.name pp.coercions.types.defValue
 def getPPExplicit (o : Options) : Bool := o.get pp.explicit.name (getPPAll o)
 def getPPNotation (o : Options) : Bool := o.get pp.notation.name (!getPPAll o)
 def getPPParens (o : Options) : Bool := o.get pp.parens.name pp.parens.defValue

src/Lean/PrettyPrinter/Formatter.lean

@@ -467,7 +467,7 @@ def visitAtom (k : SyntaxNodeKind) : Formatter := do
 @[combinator_formatter manyNoAntiquot]
 def manyNoAntiquot.formatter (p : Formatter) : Formatter := do
   let stx ← getCur
-  visitArgs $ stx.getArgs.size.forM fun _ _ => p
+  visitArgs $ stx.getArgs.size.forM fun _ => p
 
 @[combinator_formatter many1NoAntiquot] def many1NoAntiquot.formatter (p : Formatter) : Formatter := manyNoAntiquot.formatter p
 
@@ -487,7 +487,7 @@ def many1Unbox.formatter (p : Formatter) : Formatter := do
 @[combinator_formatter sepByNoAntiquot]
 def sepByNoAntiquot.formatter (p pSep : Formatter) : Formatter := do
   let stx ← getCur
-  visitArgs <| stx.getArgs.size.forRevM fun i _ => if i % 2 == 0 then p else pSep
+  visitArgs <| stx.getArgs.size.forRevM fun i => if i % 2 == 0 then p else pSep
 
 @[combinator_formatter sepBy1NoAntiquot] def sepBy1NoAntiquot.formatter := sepByNoAntiquot.formatter
 

src/Lean/PrettyPrinter/Parenthesizer.lean

@@ -268,7 +268,7 @@ def visitToken : Parenthesizer := do
   let stx ← getCur
   -- `orelse` may produce `choice` nodes for antiquotations
   if stx.getKind == `choice then
-    visitArgs $ stx.getArgs.size.forM fun _ _ => do
+    visitArgs $ stx.getArgs.size.forM fun _ => do
       orelse.parenthesizer p1 p2
   else
     -- HACK: We have no (immediate) information on which side of the orelse could have produced the current node, so try
@@ -332,7 +332,7 @@ partial def parenthesizeCategoryCore (cat : Name) (_prec : Nat) : Parenthesizer
   withReader (fun ctx => { ctx with cat := cat }) do
     let stx ← getCur
     if stx.getKind == `choice then
-      visitArgs $ stx.getArgs.size.forM fun _ _ => do
+      visitArgs $ stx.getArgs.size.forM fun _ => do
         parenthesizeCategoryCore cat _prec
     else
       withAntiquot.parenthesizer (mkAntiquot.parenthesizer' cat.toString cat (isPseudoKind := true)) (parenthesizerForKind stx.getKind)
@@ -470,7 +470,7 @@ def trailingNode.parenthesizer (k : SyntaxNodeKind) (prec lhsPrec : Nat) (p : Pa
 @[combinator_parenthesizer manyNoAntiquot]
 def manyNoAntiquot.parenthesizer (p : Parenthesizer) : Parenthesizer := do
   let stx ← getCur
-  visitArgs $ stx.getArgs.size.forM fun _ _ => p
+  visitArgs $ stx.getArgs.size.forM fun _ => p
 
 @[combinator_parenthesizer many1NoAntiquot]
 def many1NoAntiquot.parenthesizer (p : Parenthesizer) : Parenthesizer := do