.

.gitpod.Dockerfile

@@ -1,14 +0,0 @@
-# You can find the new timestamped tags here: https://hub.docker.com/r/gitpod/workspace-full/tags
-FROM gitpod/workspace-full
-
-USER root
-RUN apt-get update && apt-get install git libgmp-dev libuv1-dev cmake ccache clang -y && apt-get clean
-
-USER gitpod
-
-# Install and configure elan
-RUN curl https://raw.githubusercontent.com/leanprover/elan/master/elan-init.sh -sSf | sh -s -- -y --default-toolchain none
-ENV PATH="/home/gitpod/.elan/bin:${PATH}"
-# Create a dummy toolchain so that we can pre-register it with elan
-RUN mkdir -p /workspace/lean4/build/release/stage1/bin && touch /workspace/lean4/build/release/stage1/bin/lean && elan toolchain link lean4 /workspace/lean4/build/release/stage1
-RUN mkdir -p /workspace/lean4/build/release/stage0/bin && touch /workspace/lean4/build/release/stage0/bin/lean && elan toolchain link lean4-stage0 /workspace/lean4/build/release/stage0

.gitpod.yml

@@ -1,11 +0,0 @@
-image:
-    file: .gitpod.Dockerfile
-
-vscode:
-  extensions:
-    - leanprover.lean4
-
-tasks:
-  - name: Release build
-    init: cmake --preset release
-    command: make -C build/release -j$(nproc || sysctl -n hw.logicalcpu)

doc/examples/ICERM2022/meta.lean

@@ -29,7 +29,7 @@ def ex3 (declName : Name) : MetaM Unit := do
     for x in xs do
       trace[Meta.debug] "{x} : {← inferType x}"
 
-def myMin [LT α] [DecidableLT α] (a b : α) : α :=
+def myMin [LT α] [DecidableRel (α := α) (·<·)] (a b : α) : α :=
   if a < b then
     a
   else

releases_drafts/list_lex.md

@@ -1,16 +0,0 @@
-We replace the inductive predicate `List.lt` with an upstreamed version of `List.Lex` from Mathlib.
-(Previously `Lex.lt` was defined in terms of `<`; now it is generalized to take an arbitrary relation.)
-This subtely changes the notion of ordering on `List α`.
-
-`List.lt` was a weaker relation: in particular if `l₁ < l₂`, then
-`a :: l₁ < b :: l₂` may hold according to `List.lt` even if `a` and `b` are merely incomparable
-(either neither `a < b` nor `b < a`), whereas according to `List.Lex` this would require `a = b`.
-
-When `<` is total, in the sense that `¬ · < ·` is antisymmetric, then the two relations coincide.
-
-Mathlib was already overriding the order instances for `List α`,
-so this change should not be noticed by anyone already using Mathlib.
-
-We simultaneously add the boolean valued `List.lex` function, parameterised by a `BEq` typeclass
-and an arbitrary `lt` function. This will support the flexibility previously provided for `List.lt`,
-via a `==` function which is weaker than strict equality.

src/Init/Control/Lawful/Basic.lean

@@ -106,7 +106,7 @@ theorem seq_eq_bind_map {α β : Type u} [Monad m] [LawfulMonad m] (f : m (α
 theorem bind_congr [Bind m] {x : m α} {f g : α → m β} (h : ∀ a, f a = g a) : x >>= f = x >>= g := by
   simp [funext h]
 
-theorem bind_pure_unit [Monad m] [LawfulMonad m] {x : m PUnit} : (x >>= fun _ => pure ⟨⟩) = x := by
+@[simp] theorem bind_pure_unit [Monad m] [LawfulMonad m] {x : m PUnit} : (x >>= fun _ => pure ⟨⟩) = x := by
   rw [bind_pure]
 
 theorem map_congr [Functor m] {x : m α} {f g : α → β} (h : ∀ a, f a = g a) : (f <$> x : m β) = g <$> x := by
@@ -133,7 +133,7 @@ theorem seqLeft_eq_bind [Monad m] [LawfulMonad m] (x : m α) (y : m β) : x <* y
   rw [← bind_pure_comp]
   simp only [bind_assoc, pure_bind]
 
-theorem Functor.map_unit [Monad m] [LawfulMonad m] {a : m PUnit} : (fun _ => PUnit.unit) <$> a = a := by
+@[simp] theorem Functor.map_unit [Monad m] [LawfulMonad m] {a : m PUnit} : (fun _ => PUnit.unit) <$> a = a := by
   simp [map]
 
 /--

src/Init/Core.lean

@@ -2116,37 +2116,14 @@ instance : Commutative Or := ⟨fun _ _ => propext or_comm⟩
 instance : Commutative And := ⟨fun _ _ => propext and_comm⟩
 instance : Commutative Iff := ⟨fun _ _ => propext iff_comm⟩
 
-/-- `IsRefl X r` means the binary relation `r` on `X` is reflexive. -/
-class Refl (r : α → α → Prop) : Prop where
-  /-- A reflexive relation satisfies `r a a`. -/
-  refl : ∀ a, r a a
-
 /--
 `Antisymm (·≤·)` says that `(·≤·)` is antisymmetric, that is, `a ≤ b → b ≤ a → a = b`.
 -/
 class Antisymm (r : α → α → Prop) : Prop where
   /-- An antisymmetric relation `(·≤·)` satisfies `a ≤ b → b ≤ a → a = b`. -/
-  antisymm (a b : α) : r a b → r b a → a = b
+  antisymm {a b : α} : r a b → r b a → a = b
 
 @[deprecated Antisymm (since := "2024-10-16"), inherit_doc Antisymm]
 abbrev _root_.Antisymm (r : α → α → Prop) : Prop := Std.Antisymm r
 
-/-- `Asymm X r` means that the binary relation `r` on `X` is asymmetric, that is,
-`r a b → ¬ r b a`. -/
-class Asymm (r : α → α → Prop) : Prop where
-  /-- An asymmetric relation satisfies `r a b → ¬ r b a`. -/
-  asymm : ∀ a b, r a b → ¬r b a
-
-/-- `Total X r` means that the binary relation `r` on `X` is total, that is, that for any
-`x y : X` we have `r x y` or `r y x`. -/
-class Total (r : α → α → Prop) : Prop where
-  /-- A total relation satisfies `r a b ∨ r b a`. -/
-  total : ∀ a b, r a b ∨ r b a
-
-/-- `Irrefl X r` means the binary relation `r` on `X` is irreflexive (that is, `r x x` never
-holds). -/
-class Irrefl (r : α → α → Prop) : Prop where
-  /-- An irreflexive relation satisfies `¬ r a a`. -/
-  irrefl : ∀ a, ¬r a a
-
 end Std

src/Init/Data/Array.lean

@@ -22,4 +22,3 @@ import Init.Data.Array.Monadic
 import Init.Data.Array.FinRange
 import Init.Data.Array.Perm
 import Init.Data.Array.Find
-import Init.Data.Array.Lex

src/Init/Data/Array/Attach.lean

@@ -150,6 +150,7 @@ theorem attach_map_coe (l : Array α) (f : α → β) :
 theorem attach_map_val (l : Array α) (f : α → β) : (l.attach.map fun i => f i.val) = l.map f :=
   attach_map_coe _ _
 
+@[simp]
 theorem attach_map_subtype_val (l : Array α) : l.attach.map Subtype.val = l := by
   cases l; simp
 
@@ -161,6 +162,7 @@ theorem attachWith_map_val {p : α → Prop} (f : α → β) (l : Array α) (H :
     ((l.attachWith p H).map fun i => f i.val) = l.map f :=
   attachWith_map_coe _ _ _
 
+@[simp]
 theorem attachWith_map_subtype_val {p : α → Prop} (l : Array α) (H : ∀ a ∈ l, p a) :
     (l.attachWith p H).map Subtype.val = l := by
   cases l; simp
@@ -202,8 +204,8 @@ theorem pmap_ne_empty_iff {P : α → Prop} (f : (a : α) → P a → β) {xs :
     (H : ∀ (a : α), a ∈ xs → P a) : xs.pmap f H ≠ #[] ↔ xs ≠ #[] := by
   cases xs; simp
 
-theorem pmap_eq_self {l : Array α} {p : α → Prop} {hp : ∀ (a : α), a ∈ l → p a}
-    {f : (a : α) → p a → α} : l.pmap f hp = l ↔ ∀ a (h : a ∈ l), f a (hp a h) = a := by
+theorem pmap_eq_self {l : Array α} {p : α → Prop} (hp : ∀ (a : α), a ∈ l → p a)
+    (f : (a : α) → p a → α) : l.pmap f hp = l ↔ ∀ a (h : a ∈ l), f a (hp a h) = a := by
   cases l; simp [List.pmap_eq_self]
 
 @[simp]

src/Init/Data/Array/Basic.lean

@@ -79,8 +79,7 @@ theorem ext' {as bs : Array α} (h : as.toList = bs.toList) : as = bs := by
 @[simp] theorem toArrayAux_eq (as : List α) (acc : Array α) : (as.toArrayAux acc).toList = acc.toList ++ as := by
   induction as generalizing acc <;> simp [*, List.toArrayAux, Array.push, List.append_assoc, List.concat_eq_append]
 
--- This does not need to be a simp lemma, as already after the `whnfR` the right hand side is `as`.
-theorem toList_toArray (as : List α) : as.toArray.toList = as := rfl
+@[simp] theorem toList_toArray (as : List α) : as.toArray.toList = as := rfl
 
 @[simp] theorem size_toArray (as : List α) : as.toArray.size = as.length := by simp [size]
 
@@ -209,7 +208,7 @@ instance : EmptyCollection (Array α) := ⟨Array.empty⟩
 instance : Inhabited (Array α) where
   default := Array.empty
 
-def isEmpty (a : Array α) : Bool :=
+@[simp] def isEmpty (a : Array α) : Bool :=
   a.size = 0
 
 @[specialize]
@@ -663,15 +662,9 @@ def any (as : Array α) (p : α → Bool) (start := 0) (stop := as.size) : Bool
 def all (as : Array α) (p : α → Bool) (start := 0) (stop := as.size) : Bool :=
   Id.run <| as.allM p start stop
 
-/-- `as.contains a` is true if there is some element `b` in `as` such that `a == b`. -/
 def contains [BEq α] (as : Array α) (a : α) : Bool :=
   as.any (a == ·)
 
-/--
-Variant of `Array.contains` with arguments reversed.
-
-For verification purposes, we simplify this to `contains`.
--/
 def elem [BEq α] (a : α) (as : Array α) : Bool :=
   as.contains a
 
@@ -821,7 +814,7 @@ decreasing_by simp_wf; exact Nat.sub_succ_lt_self _ _ h
   induction a, i, h using Array.eraseIdx.induct with
   | @case1 a i h h' a' ih =>
     unfold eraseIdx
-    simp +zetaDelta [h', a', ih]
+    simp [h', a', ih]
   | case2 a i h h' =>
     unfold eraseIdx
     simp [h']
@@ -944,13 +937,6 @@ def split (as : Array α) (p : α → Bool) : Array α × Array α :=
   as.foldl (init := (#[], #[])) fun (as, bs) a =>
     if p a then (as.push a, bs) else (as, bs.push a)
 
-/-! ### Lexicographic ordering -/
-
-instance instLT [LT α] : LT (Array α) := ⟨fun as bs => as.toList < bs.toList⟩
-instance instLE [LT α] : LE (Array α) := ⟨fun as bs => as.toList ≤ bs.toList⟩
-
--- See `Init.Data.Array.Lex.Basic` for the boolean valued lexicographic comparator.
-
 /-! ## Auxiliary functions used in metaprogramming.
 
 We do not currently intend to provide verification theorems for these functions.

src/Init/Data/Array/BasicAux.lean

@@ -32,8 +32,10 @@ private theorem List.of_toArrayAux_eq_toArrayAux {as bs : List α} {cs ds : Arra
     have := Array.of_push_eq_push ih₂
     simp [this]
 
-theorem List.toArray_eq_toArray_eq (as bs : List α) : (as.toArray = bs.toArray) = (as = bs) := by
-  simp
+@[simp] theorem List.toArray_eq_toArray_eq (as bs : List α) : (as.toArray = bs.toArray) = (as = bs) := by
+  apply propext; apply Iff.intro
+  · intro h; simpa [toArray] using h
+  · intro h; rw [h]
 
 def Array.mapM' [Monad m] (f : α → m β) (as : Array α) : m { bs : Array β // bs.size = as.size } :=
   go 0 ⟨mkEmpty as.size, rfl⟩ (by simp)

src/Init/Data/Array/Bootstrap.lean

@@ -93,14 +93,11 @@ theorem foldrM_eq_reverse_foldlM_toList [Monad m] (f : α → β → m β) (init
 @[simp] theorem appendList_eq_append
     (arr : Array α) (l : List α) : arr.appendList l = arr ++ l := rfl
 
-@[simp] theorem toList_appendList (arr : Array α) (l : List α) :
+@[simp] theorem appendList_toList (arr : Array α) (l : List α) :
     (arr ++ l).toList = arr.toList ++ l := by
   rw [← appendList_eq_append]; unfold Array.appendList
   induction l generalizing arr <;> simp [*]
 
-@[deprecated toList_appendList (since := "2024-12-11")]
-abbrev appendList_toList := @toList_appendList
-
 @[deprecated "Use the reverse direction of `foldrM_toList`." (since := "2024-11-13")]
 theorem foldrM_eq_foldrM_toList [Monad m]
     (f : α → β → m β) (init : β) (arr : Array α) :
@@ -152,7 +149,7 @@ abbrev pop_data := @pop_toList
 @[deprecated toList_append (since := "2024-09-09")]
 abbrev append_data := @toList_append
 
-@[deprecated toList_appendList (since := "2024-09-09")]
-abbrev appendList_data := @toList_appendList
+@[deprecated appendList_toList (since := "2024-09-09")]
+abbrev appendList_data := @appendList_toList
 
 end Array

src/Init/Data/Array/DecidableEq.lean

@@ -42,7 +42,7 @@ theorem rel_of_isEqv {r : α → α → Bool} {a b : Array α} :
   · exact fun h' => ⟨h, fun i => rel_of_isEqvAux h (Nat.le_refl ..) h'⟩
   · intro; contradiction
 
-theorem isEqv_iff_rel {a b : Array α} {r} :
+theorem isEqv_iff_rel (a b : Array α) (r) :
     Array.isEqv a b r ↔ ∃ h : a.size = b.size, ∀ (i : Nat) (h' : i < a.size), r (a[i]) (b[i]'(h ▸ h')) :=
   ⟨rel_of_isEqv, fun ⟨h, w⟩ => by
     simp only [isEqv, ← h, ↓reduceDIte]

src/Init/Data/Array/Find.lean

@@ -99,7 +99,7 @@ theorem back?_flatten {L : Array (Array α)} :
   simp [List.getLast?_flatten, ← List.map_reverse, List.findSome?_map, Function.comp_def]
 
 theorem findSome?_mkArray : findSome? f (mkArray n a) = if n = 0 then none else f a := by
-  simp [← List.toArray_replicate, List.findSome?_replicate]
+  simp [mkArray_eq_toArray_replicate, List.findSome?_replicate]
 
 @[simp] theorem findSome?_mkArray_of_pos (h : 0 < n) : findSome? f (mkArray n a) = f a := by
   simp [findSome?_mkArray, Nat.ne_of_gt h]
@@ -246,7 +246,7 @@ theorem find?_flatMap_eq_none {xs : Array α} {f : α → Array β} {p : β →
 
 theorem find?_mkArray :
     find? p (mkArray n a) = if n = 0 then none else if p a then some a else none := by
-  simp [← List.toArray_replicate, List.find?_replicate]
+  simp [mkArray_eq_toArray_replicate, List.find?_replicate]
 
 @[simp] theorem find?_mkArray_of_length_pos (h : 0 < n) :
     find? p (mkArray n a) = if p a then some a else none := by
@@ -262,15 +262,15 @@ theorem find?_mkArray :
 -- This isn't a `@[simp]` lemma since there is already a lemma for `l.find? p = none` for any `l`.
 theorem find?_mkArray_eq_none {n : Nat} {a : α} {p : α → Bool} :
     (mkArray n a).find? p = none ↔ n = 0 ∨ !p a := by
-  simp [← List.toArray_replicate, List.find?_replicate_eq_none, Classical.or_iff_not_imp_left]
+  simp [mkArray_eq_toArray_replicate, List.find?_replicate_eq_none, Classical.or_iff_not_imp_left]
 
 @[simp] theorem find?_mkArray_eq_some {n : Nat} {a b : α} {p : α → Bool} :
     (mkArray n a).find? p = some b ↔ n ≠ 0 ∧ p a ∧ a = b := by
-  simp [← List.toArray_replicate]
+  simp [mkArray_eq_toArray_replicate]
 
 @[simp] theorem get_find?_mkArray (n : Nat) (a : α) (p : α → Bool) (h) :
     ((mkArray n a).find? p).get h = a := by
-  simp [← List.toArray_replicate]
+  simp [mkArray_eq_toArray_replicate]
 
 theorem find?_pmap {P : α → Prop} (f : (a : α) → P a → β) (xs : Array α)
     (H : ∀ (a : α), a ∈ xs → P a) (p : β → Bool) :

src/Init/Data/Array/Lemmas.lean

@@ -12,8 +12,6 @@ import Init.Data.List.Monadic
 import Init.Data.List.OfFn
 import Init.Data.Array.Mem
 import Init.Data.Array.DecidableEq
-import Init.Data.Array.Lex.Basic
-import Init.Data.Range.Lemmas
 import Init.TacticsExtra
 import Init.Data.List.ToArray
 
@@ -27,8 +25,8 @@ namespace Array
 
 /-! ### toList -/
 
-theorem toList_inj {a b : Array α} : a.toList = b.toList ↔ a = b := by
-  cases a; cases b; simp
+theorem toList_inj {a b : Array α} (h : a.toList = b.toList) : a = b := by
+  cases a; cases b; simpa using h
 
 @[simp] theorem toList_eq_nil_iff (l : Array α) : l.toList = [] ↔ l = #[] := by
   cases l <;> simp
@@ -55,7 +53,7 @@ theorem ne_empty_of_size_pos (h : 0 < l.size) : l ≠ #[] := by
   cases l
   simpa using List.ne_nil_of_length_pos h
 
-theorem size_eq_zero : l.size = 0 ↔ l = #[] :=
+@[simp] theorem size_eq_zero : l.size = 0 ↔ l = #[] :=
   ⟨eq_empty_of_size_eq_zero, fun h => h ▸ rfl⟩
 
 theorem size_pos_of_mem {a : α} {l : Array α} (h : a ∈ l) : 0 < l.size := by
@@ -145,34 +143,6 @@ theorem exists_push_of_size_eq_add_one {xs : Array α} (h : xs.size = n + 1) :
     ∃ (ys : Array α) (a : α), xs = ys.push a :=
   exists_push_of_size_pos (by simp [h])
 
-theorem singleton_inj : #[a] = #[b] ↔ a = b := by
-  simp
-
-/-! ### mkArray -/
-
-@[simp] theorem size_mkArray (n : Nat) (v : α) : (mkArray n v).size = n :=
-  List.length_replicate ..
-
-@[simp] theorem toList_mkArray : (mkArray n a).toList = List.replicate n a := by
-  simp only [mkArray]
-
-@[simp] theorem mkArray_zero : mkArray 0 a = #[] := rfl
-
-theorem mkArray_succ : mkArray (n + 1) a = (mkArray n a).push a := by
-  apply toList_inj.1
-  simp [List.replicate_succ']
-
-theorem mkArray_inj : mkArray n a = mkArray m b ↔ n = m ∧ (n = 0 ∨ a = b) := by
-  rw [← List.replicate_inj, ← toList_inj]
-  simp
-
-@[simp] theorem getElem_mkArray (n : Nat) (v : α) (h : i < (mkArray n v).size) :
-    (mkArray n v)[i] = v := by simp [← getElem_toList]
-
-theorem getElem?_mkArray (n : Nat) (v : α) (i : Nat) :
-    (mkArray n v)[i]? = if i < n then some v else none := by
-  simp [getElem?_def]
-
 /-! ## L[i] and L[i]? -/
 
 @[simp] theorem getElem?_eq_none_iff {a : Array α} : a[i]? = none ↔ a.size ≤ i := by
@@ -204,7 +174,7 @@ theorem some_eq_getElem?_iff {a : Array α} : some b = a[i]? ↔ ∃ h : i < a.s
     (a[i]? = some a[i]) ↔ True := by
   simp [h]
 
-theorem getElem_eq_iff {a : Array α} {i : Nat} {h : i < a.size} : a[i] = x ↔ a[i]? = some x := by
+theorem getElem_eq_iff {a : Array α} {n : Nat} {h : n < a.size} : a[n] = x ↔ a[n]? = some x := by
   simp only [getElem?_eq_some_iff]
   exact ⟨fun w => ⟨h, w⟩, fun h => h.2⟩
 
@@ -220,7 +190,7 @@ theorem getD_getElem? (a : Array α) (i : Nat) (d : α) :
     have p : i ≥ a.size := Nat.le_of_not_gt h
     simp [getElem?_eq_none p, h]
 
-@[simp] theorem getElem?_empty {i : Nat} : (#[] : Array α)[i]? = none := rfl
+@[simp] theorem getElem?_empty {n : Nat} : (#[] : Array α)[n]? = none := rfl
 
 theorem getElem_push_lt (a : Array α) (x : α) (i : Nat) (h : i < a.size) :
     have : i < (a.push x).size := by simp [*, Nat.lt_succ_of_le, Nat.le_of_lt]
@@ -254,7 +224,7 @@ theorem getElem?_singleton (a : α) (i : Nat) : #[a][i]? = if i = 0 then some a
 
 /-! ### mem -/
 
-theorem not_mem_empty (a : α) : ¬ a ∈ #[] := by simp
+@[simp] theorem not_mem_empty (a : α) : ¬ a ∈ #[] := nofun
 
 @[simp] theorem mem_push {a : Array α} {x y : α} : x ∈ a.push y ↔ x ∈ a ∨ x = y := by
   simp only [mem_def]
@@ -281,19 +251,19 @@ theorem eq_empty_iff_forall_not_mem {l : Array α} : l = #[] ↔ ∀ a, a ∉ l
   cases l
   simp [List.eq_nil_iff_forall_not_mem]
 
-@[simp] theorem mem_dite_empty_left {x : α} [Decidable p] {l : ¬ p → Array α} :
+@[simp] theorem mem_dite_nil_left {x : α} [Decidable p] {l : ¬ p → Array α} :
     (x ∈ if h : p then #[] else l h) ↔ ∃ h : ¬ p, x ∈ l h := by
   split <;> simp_all
 
-@[simp] theorem mem_dite_empty_right {x : α} [Decidable p] {l : p → Array α} :
+@[simp] theorem mem_dite_nil_right {x : α} [Decidable p] {l : p → Array α} :
     (x ∈ if h : p then l h else #[]) ↔ ∃ h : p, x ∈ l h := by
   split <;> simp_all
 
-@[simp] theorem mem_ite_empty_left {x : α} [Decidable p] {l : Array α} :
+@[simp] theorem mem_ite_nil_left {x : α} [Decidable p] {l : Array α} :
     (x ∈ if p then #[] else l) ↔ ¬ p ∧ x ∈ l := by
   split <;> simp_all
 
-@[simp] theorem mem_ite_empty_right {x : α} [Decidable p] {l : Array α} :
+@[simp] theorem mem_ite_nil_right {x : α} [Decidable p] {l : Array α} :
     (x ∈ if p then l else #[]) ↔ p ∧ x ∈ l := by
   split <;> simp_all
 
@@ -320,7 +290,7 @@ theorem forall_mem_empty (p : α → Prop) : ∀ (x) (_ : x ∈ #[]), p x := nof
 
 theorem exists_mem_push {p : α → Prop} {a : α} {xs : Array α} :
     (∃ x, ∃ _ : x ∈ xs.push a, p x) ↔ p a ∨ ∃ x, ∃ _ : x ∈ xs, p x := by
-  simp only [mem_push, exists_prop]
+  simp
   constructor
   · rintro ⟨x, (h | rfl), h'⟩
     · exact .inr ⟨x, h, h'⟩
@@ -349,7 +319,7 @@ theorem eq_or_ne_mem_of_mem {a b : α} {l : Array α} (h' : a ∈ l.push b) :
   if h : a = b then
     exact .inl h
   else
-    simp only [mem_push, h, or_false] at h'
+    simp [h] at h'
     exact .inr ⟨h, h'⟩
 
 theorem ne_empty_of_mem {a : α} {l : Array α} (h : a ∈ l) : l ≠ #[] := by
@@ -373,27 +343,27 @@ theorem not_mem_push_of_ne_of_not_mem {a y : α} {l : Array α} : a ≠ y → a
 theorem ne_and_not_mem_of_not_mem_push {a y : α} {l : Array α} : a ∉ l.push y → a ≠ y ∧ a ∉ l := by
   simp +contextual
 
-theorem getElem_of_mem {a} {l : Array α} (h : a ∈ l) : ∃ (i : Nat) (h : i < l.size), l[i]'h = a := by
+theorem getElem_of_mem {a} {l : Array α} (h : a ∈ l) : ∃ (n : Nat) (h : n < l.size), l[n]'h = a := by
   cases l
   simp [List.getElem_of_mem (by simpa using h)]
 
-theorem getElem?_of_mem {a} {l : Array α} (h : a ∈ l) : ∃ i : Nat, l[i]? = some a :=
+theorem getElem?_of_mem {a} {l : Array α} (h : a ∈ l) : ∃ n : Nat, l[n]? = some a :=
   let ⟨n, _, e⟩ := getElem_of_mem h; ⟨n, e ▸ getElem?_eq_getElem _⟩
 
-theorem mem_of_getElem? {l : Array α} {i : Nat} {a : α} (e : l[i]? = some a) : a ∈ l :=
+theorem mem_of_getElem? {l : Array α} {n : Nat} {a : α} (e : l[n]? = some a) : a ∈ l :=
   let ⟨_, e⟩ := getElem?_eq_some_iff.1 e; e ▸ getElem_mem ..
 
-theorem mem_iff_getElem {a} {l : Array α} : a ∈ l ↔ ∃ (i : Nat) (h : i < l.size), l[i]'h = a :=
+theorem mem_iff_getElem {a} {l : Array α} : a ∈ l ↔ ∃ (n : Nat) (h : n < l.size), l[n]'h = a :=
   ⟨getElem_of_mem, fun ⟨_, _, e⟩ => e ▸ getElem_mem ..⟩
 
-theorem mem_iff_getElem? {a} {l : Array α} : a ∈ l ↔ ∃ i : Nat, l[i]? = some a := by
+theorem mem_iff_getElem? {a} {l : Array α} : a ∈ l ↔ ∃ n : Nat, l[n]? = some a := by
   simp [getElem?_eq_some_iff, mem_iff_getElem]
 
 theorem forall_getElem {l : Array α} {p : α → Prop} :
-    (∀ (i : Nat) h, p (l[i]'h)) ↔ ∀ a, a ∈ l → p a := by
+    (∀ (n : Nat) h, p (l[n]'h)) ↔ ∀ a, a ∈ l → p a := by
   cases l; simp [List.forall_getElem]
 
-/-! ### isEmpty -/
+/-! ### isEmpty-/
 
 @[simp] theorem isEmpty_toList {l : Array α} : l.toList.isEmpty = l.isEmpty := by
   rcases l with ⟨_ | _⟩ <;> simp
@@ -513,7 +483,7 @@ theorem any_iff_exists {p : α → Bool} {as : Array α} {start stop} :
   rw [Bool.eq_false_iff, Ne, any_eq_true]
   simp
 
-@[simp] theorem any_toList {p : α → Bool} (as : Array α) : as.toList.any p = as.any p := by
+theorem any_toList {p : α → Bool} (as : Array α) : as.toList.any p = as.any p := by
   rw [Bool.eq_iff_iff, any_eq_true, List.any_eq_true]
   simp only [List.mem_iff_getElem, getElem_toList]
   exact ⟨fun ⟨_, ⟨i, w, rfl⟩, h⟩ => ⟨i, w, h⟩, fun ⟨i, w, h⟩ => ⟨_, ⟨i, w, rfl⟩, h⟩⟩
@@ -552,7 +522,7 @@ theorem all_iff_forall {p : α → Bool} {as : Array α} {start stop} :
   rw [Bool.eq_false_iff, Ne, all_eq_true]
   simp
 
-@[simp] theorem all_toList {p : α → Bool} (as : Array α) : as.toList.all p = as.all p := by
+theorem all_toList {p : α → Bool} (as : Array α) : as.toList.all p = as.all p := by
   rw [Bool.eq_iff_iff, all_eq_true, List.all_eq_true]
   simp only [List.mem_iff_getElem, getElem_toList]
   constructor
@@ -564,6 +534,20 @@ theorem all_iff_forall {p : α → Bool} {as : Array α} {start stop} :
 theorem all_eq_true_iff_forall_mem {l : Array α} : l.all p ↔ ∀ x, x ∈ l → p x := by
   simp only [← all_toList, List.all_eq_true, mem_def]
 
+theorem _root_.List.anyM_toArray [Monad m] [LawfulMonad m] (p : α → m Bool) (l : List α) :
+    l.toArray.anyM p = l.anyM p := by
+  rw [← anyM_toList]
+
+theorem _root_.List.any_toArray (p : α → Bool) (l : List α) : l.toArray.any p = l.any p := by
+  rw [any_toList]
+
+theorem _root_.List.allM_toArray [Monad m] [LawfulMonad m] (p : α → m Bool) (l : List α) :
+    l.toArray.allM p = l.allM p := by
+  rw [← allM_toList]
+
+theorem _root_.List.all_toArray (p : α → Bool) (l : List α) : l.toArray.all p = l.all p := by
+  rw [all_toList]
+
 /-- Variant of `anyM_toArray` with a side condition on `stop`. -/
 @[simp] theorem _root_.List.anyM_toArray' [Monad m] [LawfulMonad m] (p : α → m Bool) (l : List α)
     (h : stop = l.toArray.size) :
@@ -590,20 +574,6 @@ theorem all_eq_true_iff_forall_mem {l : Array α} : l.all p ↔ ∀ x, x ∈ l
   subst h
   rw [all_toList]
 
-theorem _root_.List.anyM_toArray [Monad m] [LawfulMonad m] (p : α → m Bool) (l : List α) :
-    l.toArray.anyM p = l.anyM p := by
-  rw [← anyM_toList]
-
-theorem _root_.List.any_toArray (p : α → Bool) (l : List α) : l.toArray.any p = l.any p := by
-  rw [any_toList]
-
-theorem _root_.List.allM_toArray [Monad m] [LawfulMonad m] (p : α → m Bool) (l : List α) :
-    l.toArray.allM p = l.allM p := by
-  rw [← allM_toList]
-
-theorem _root_.List.all_toArray (p : α → Bool) (l : List α) : l.toArray.all p = l.all p := by
-  rw [all_toList]
-
 /-- Variant of `any_eq_true` in terms of membership rather than an array index. -/
 theorem any_eq_true' {p : α → Bool} {as : Array α} :
     as.any p = true ↔ (∃ x, x ∈ as ∧ p x) := by
@@ -671,7 +641,7 @@ theorem decide_forall_mem {xs : Array α} {p : α → Prop} [DecidablePred p] :
     l.toArray.contains a = l.contains a := by
   simp [Array.contains, List.any_beq]
 
-theorem _root_.List.elem_toArray [BEq α] {l : List α} {a : α} :
+@[simp] theorem _root_.List.elem_toArray [BEq α] {l : List α} {a : α} :
     Array.elem a l.toArray = List.elem a l := by
   simp [Array.elem]
 
@@ -693,32 +663,26 @@ theorem all_bne' [BEq α] [PartialEquivBEq α] {xs : Array α} :
     (xs.all fun x => x != a) = !xs.contains a := by
   simp only [bne_comm, all_bne]
 
-theorem mem_of_contains_eq_true [BEq α] [LawfulBEq α] {a : α} {as : Array α} : as.contains a = true → a ∈ as := by
+theorem mem_of_elem_eq_true [BEq α] [LawfulBEq α] {a : α} {as : Array α} : elem a as = true → a ∈ as := by
   cases as
   simp
 
-@[deprecated mem_of_contains_eq_true (since := "2024-12-12")]
-abbrev mem_of_elem_eq_true := @mem_of_contains_eq_true
-
-theorem contains_eq_true_of_mem [BEq α] [LawfulBEq α] {a : α} {as : Array α} (h : a ∈ as) : as.contains a = true := by
+theorem elem_eq_true_of_mem [BEq α] [LawfulBEq α] {a : α} {as : Array α} (h : a ∈ as) : elem a as = true := by
   cases as
   simpa using h
 
-@[deprecated contains_eq_true_of_mem (since := "2024-12-12")]
-abbrev elem_eq_true_of_mem := @contains_eq_true_of_mem
-
 instance [BEq α] [LawfulBEq α] (a : α) (as : Array α) : Decidable (a ∈ as) :=
-  decidable_of_decidable_of_iff (Iff.intro mem_of_contains_eq_true contains_eq_true_of_mem)
+  decidable_of_decidable_of_iff (Iff.intro mem_of_elem_eq_true elem_eq_true_of_mem)
 
 @[simp] theorem elem_eq_contains [BEq α] {a : α} {l : Array α} :
     elem a l = l.contains a := by
   simp [elem]
 
 theorem elem_iff [BEq α] [LawfulBEq α] {a : α} {as : Array α} :
-    elem a as = true ↔ a ∈ as := ⟨mem_of_contains_eq_true, contains_eq_true_of_mem⟩
+    elem a as = true ↔ a ∈ as := ⟨mem_of_elem_eq_true, elem_eq_true_of_mem⟩
 
 theorem contains_iff [BEq α] [LawfulBEq α] {a : α} {as : Array α} :
-    as.contains a = true ↔ a ∈ as := ⟨mem_of_contains_eq_true, contains_eq_true_of_mem⟩
+    as.contains a = true ↔ a ∈ as := ⟨mem_of_elem_eq_true, elem_eq_true_of_mem⟩
 
 theorem elem_eq_mem [BEq α] [LawfulBEq α] (a : α) (as : Array α) :
     elem a as = decide (a ∈ as) := by rw [Bool.eq_iff_iff, elem_iff, decide_eq_true_iff]
@@ -754,6 +718,9 @@ theorem all_push [BEq α] {as : Array α} {a : α} {p : α → Bool} :
 
 /-! ### set -/
 
+
+/-! # set -/
+
 @[simp] theorem getElem_set_self (a : Array α) (i : Nat) (h : i < a.size) (v : α) {j : Nat}
       (eq : i = j) (p : j < (a.set i v).size) :
     (a.set i v)[j]'p = v := by
@@ -798,36 +765,30 @@ theorem getElem?_set (a : Array α) (i : Nat) (h : i < a.size) (v : α) (j : Nat
   cases as <;> cases n <;> simp [set]
 
 theorem set_comm (a b : α)
-    {i j : Nat} (as : Array α) {hi : i < as.size} {hj : j < (as.set i a).size} (h : i ≠ j) :
-    (as.set i a).set j b = (as.set j b (by simpa using hj)).set i a (by simpa using hi) := by
+    {n m : Nat} (as : Array α) {hn : n < as.size} {hm : m < (as.set n a).size} (h : n ≠ m) :
+    (as.set n a).set m b = (as.set m b (by simpa using hm)).set n a (by simpa using hn) := by
   cases as
   simp [List.set_comm _ _ _ h]
 
 @[simp]
-theorem set_set (a b : α) (as : Array α) (i : Nat) (h : i < as.size) :
-    (as.set i a).set i b (by simpa using h) = as.set i b := by
+theorem set_set (a b : α) (as : Array α) (n : Nat) (h : n < as.size) :
+    (as.set n a).set n b (by simpa using h) = as.set n b := by
   cases as
   simp
 
-theorem mem_set (as : Array α) (i : Nat) (h : i < as.size) (a : α) :
-    a ∈ as.set i a := by
+theorem mem_set (as : Array α) (n : Nat) (h : n < as.size) (a : α) :
+    a ∈ as.set n a := by
   simp [mem_iff_getElem]
-  exact ⟨i, (by simpa using h), by simp⟩
+  exact ⟨n, (by simpa using h), by simp⟩
 
 theorem mem_or_eq_of_mem_set
-    {as : Array α} {i : Nat} {a b : α} {w : i < as.size} (h : a ∈ as.set i b) : a ∈ as ∨ a = b := by
+    {as : Array α} {n : Nat} {a b : α} {w : n < as.size} (h : a ∈ as.set n b) : a ∈ as ∨ a = b := by
   cases as
   simpa using List.mem_or_eq_of_mem_set (by simpa using h)
 
-@[simp] theorem toList_set (a : Array α) (i x h) :
-    (a.set i x).toList = a.toList.set i x := rfl
+/-! # setIfInBounds -/
 
-/-! ### setIfInBounds -/
-
-@[simp] theorem set!_eq_setIfInBounds : @set! = @setIfInBounds := rfl
-
-@[deprecated set!_eq_setIfInBounds (since := "2024-12-12")]
-abbrev set!_is_setIfInBounds := @set!_eq_setIfInBounds
+@[simp] theorem set!_is_setIfInBounds : @set! = @setIfInBounds := rfl
 
 @[simp] theorem size_setIfInBounds (as : Array α) (index : Nat) (val : α) :
     (as.setIfInBounds index val).size = as.size := by
@@ -859,23 +820,19 @@ abbrev getElem_setIfInBounds_eq := @getElem_setIfInBounds_self
     (as.setIfInBounds i v)[j]'hj = as[j]'(by simpa using hj) := by
   simp [getElem_setIfInBounds, h]
 
+@[simp]
+theorem getElem?_setIfInBounds_self (as : Array α) {i : Nat} (p : i < as.size) (v : α) :
+    (as.setIfInBounds i v)[i]? = some v := by
+  simp [getElem?_eq_getElem, p]
+
+@[deprecated getElem?_setIfInBounds_self (since := "2024-12-11")]
+abbrev getElem?_setIfInBounds_eq := @getElem?_setIfInBounds_self
+
 theorem getElem?_setIfInBounds {as : Array α} {i j : Nat} {a : α}  :
     (as.setIfInBounds i a)[j]? = if i = j then if i < as.size then some a else none else as[j]? := by
   cases as
   simp [List.getElem?_set]
 
-theorem getElem?_setIfInBounds_self (as : Array α) {i : Nat} (v : α) :
-    (as.setIfInBounds i v)[i]? = if i < as.size then some v else none := by
-  simp [getElem?_setIfInBounds]
-
-@[simp]
-theorem getElem?_setIfInBounds_self_of_lt (as : Array α) {i : Nat} (v : α) (h : i < as.size) :
-    (as.setIfInBounds i v)[i]? = some v := by
-  simp [getElem?_setIfInBounds, h]
-
-@[deprecated getElem?_setIfInBounds_self (since := "2024-12-11")]
-abbrev getElem?_setIfInBounds_eq := @getElem?_setIfInBounds_self
-
 @[simp] theorem getElem?_setIfInBounds_ne {as : Array α} {i j : Nat} (h : i ≠ j) {a : α}  :
     (as.setIfInBounds i a)[j]? = as[j]? := by
   simp [getElem?_setIfInBounds, h]
@@ -890,24 +847,24 @@ theorem setIfInBounds_eq_of_size_le {l : Array α} {n : Nat} (h : l.size ≤ n)
   cases as <;> cases n <;> simp
 
 theorem setIfInBounds_comm (a b : α)
-    {i j : Nat} (as : Array α) (h : i ≠ j) :
-    (as.setIfInBounds i a).setIfInBounds j b = (as.setIfInBounds j b).setIfInBounds i a := by
+    {n m : Nat} (as : Array α) (h : n ≠ m) :
+    (as.setIfInBounds n a).setIfInBounds m b = (as.setIfInBounds m b).setIfInBounds n a := by
   cases as
   simp [List.set_comm _ _ _ h]
 
 @[simp]
-theorem setIfInBounds_setIfInBounds (a b : α) (as : Array α) (i : Nat) :
-    (as.setIfInBounds i a).setIfInBounds i b = as.setIfInBounds i b := by
+theorem setIfInBounds_setIfInBounds (a b : α) (as : Array α) (n : Nat) :
+    (as.setIfInBounds n a).setIfInBounds n b = as.setIfInBounds n b := by
   cases as
   simp
 
-theorem mem_setIfInBounds (as : Array α) (i : Nat) (h : i < as.size) (a : α) :
-    a ∈ as.setIfInBounds i a := by
+theorem mem_setIfInBounds (as : Array α) (n : Nat) (h : n < as.size) (a : α) :
+    a ∈ as.setIfInBounds n a := by
   simp [mem_iff_getElem]
-  exact ⟨i, (by simpa using h), by simp⟩
+  exact ⟨n, (by simpa using h), by simp⟩
 
 theorem mem_or_eq_of_mem_setIfInBounds
-    {as : Array α} {i : Nat} {a b : α} (h : a ∈ as.setIfInBounds i b) : a ∈ as ∨ a = b := by
+    {as : Array α} {n : Nat} {a b : α} (h : a ∈ as.setIfInBounds n b) : a ∈ as ∨ a = b := by
   cases as
   simpa using List.mem_or_eq_of_mem_set (by simpa using h)
 
@@ -917,87 +874,9 @@ theorem mem_or_eq_of_mem_setIfInBounds
   by_cases h : i < a.size <;>
     simp [setIfInBounds, Nat.not_lt_of_le, h,  getD_getElem?]
 
-@[simp] theorem toList_setIfInBounds (a : Array α) (i x) :
-    (a.setIfInBounds i x).toList = a.toList.set i x := by
-  simp only [setIfInBounds]
-  split <;> rename_i h
-  · simp
-  · simp [List.set_eq_of_length_le (by simpa using h)]
-
-/-! ### BEq -/
-
-@[simp] theorem beq_empty_iff [BEq α] {xs : Array α} : (xs == #[]) = xs.isEmpty := by
-  cases xs
+theorem singleton_inj : #[a] = #[b] ↔ a = b := by
   simp
 
-@[simp] theorem empty_beq_iff [BEq α] {xs : Array α} : (#[] == xs) = xs.isEmpty := by
-  cases xs
-  simp
-
-@[simp] theorem push_beq_push [BEq α] {a b : α} {v : Array α} {w : Array α} :
-    (v.push a == w.push b) = (v == w && a == b) := by
-  cases v
-  cases w
-  simp
-
-theorem size_eq_of_beq [BEq α] {xs ys : Array α} (h : xs == ys) : xs.size = ys.size := by
-  cases xs
-  cases ys
-  simp [List.length_eq_of_beq (by simpa using h)]
-
-@[simp] theorem mkArray_beq_mkArray [BEq α] {a b : α} {n : Nat} :
-    (mkArray n a == mkArray n b) = (n == 0 || a == b) := by
-  cases n with
-  | zero => simp
-  | succ n =>
-    rw [mkArray_succ, mkArray_succ, push_beq_push, mkArray_beq_mkArray]
-    rw [Bool.eq_iff_iff]
-    simp +contextual
-
-@[simp] theorem reflBEq_iff [BEq α] : ReflBEq (Array α) ↔ ReflBEq α := by
-  constructor
-  · intro h
-    constructor
-    intro a
-    suffices (#[a] == #[a]) = true by
-      simpa only [instBEq, isEqv, isEqvAux, Bool.and_true]
-    simp
-  · intro h
-    constructor
-    apply Array.isEqv_self_beq
-
-@[simp] theorem lawfulBEq_iff [BEq α] : LawfulBEq (Array α) ↔ LawfulBEq α := by
-  constructor
-  · intro h
-    constructor
-    · intro a b h
-      apply singleton_inj.1
-      apply eq_of_beq
-      simp only [instBEq, isEqv, isEqvAux]
-      simpa
-    · intro a
-      suffices (#[a] == #[a]) = true by
-        simpa only [instBEq, isEqv, isEqvAux, Bool.and_true]
-      simp
-  · intro h
-    constructor
-    · intro a b h
-      obtain ⟨hs, hi⟩ := rel_of_isEqv h
-      ext i h₁ h₂
-      · exact hs
-      · simpa using hi _ h₁
-    · intro a
-      apply Array.isEqv_self_beq
-
-/-! ### isEqv -/
-
-@[simp] theorem isEqv_eq [DecidableEq α] {l₁ l₂ : Array α} : l₁.isEqv l₂ (· == ·) = (l₁ = l₂) := by
-  cases l₁
-  cases l₂
-  simp
-
-/-! Content below this point has not yet been aligned with `List`. -/
-
 theorem singleton_eq_toArray_singleton (a : α) : #[a] = [a].toArray := rfl
 
 @[simp] theorem singleton_def (v : α) : singleton v = #[v] := rfl
@@ -1011,8 +890,8 @@ theorem singleton_eq_toArray_singleton (a : α) : #[a] = [a].toArray := rfl
 
 @[simp] theorem mkEmpty_eq (α n) : @mkEmpty α n = #[] := rfl
 
-@[deprecated size_toArray (since := "2024-12-11")]
-theorem size_mk (as : List α) : (Array.mk as).size = as.length := by simp [size]
+@[simp] theorem size_mk (as : List α) : (Array.mk as).size = as.length := by simp [size]
+
 
 theorem foldrM_push [Monad m] (f : α → β → m β) (init : β) (arr : Array α) (a : α) :
     (arr.push a).foldrM f init = f a init >>= arr.foldrM f := by
@@ -1081,6 +960,11 @@ where
 @[simp] theorem appendList_cons (arr : Array α) (a : α) (l : List α) :
     arr ++ (a :: l) = arr.push a ++ l := Array.ext' (by simp)
 
+@[simp] theorem toList_appendList (arr : Array α) (l : List α) :
+    (arr ++ l).toList = arr.toList ++ l := by
+  cases arr
+  simp
+
 theorem foldl_toList_eq_flatMap (l : List α) (acc : Array β)
     (F : Array β → α → Array β) (G : α → List β)
     (H : ∀ acc a, (F acc a).toList = acc.toList ++ G a) :
@@ -1116,12 +1000,12 @@ theorem getElem?_len_le (a : Array α) {i : Nat} (h : a.size ≤ i) : a[i]? = no
 
 @[deprecated getD_getElem? (since := "2024-12-11")] abbrev getD_get? := @getD_getElem?
 
-@[simp] theorem getD_eq_get? (a : Array α) (i d) : a.getD i d = (a[i]?).getD d := by
+@[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_getElem?, *]
 
 theorem get!_eq_getD [Inhabited α] (a : Array α) : a.get! n = a.getD n default := rfl
 
-theorem get!_eq_getElem? [Inhabited α] (a : Array α) (i : Nat) :
+@[simp] theorem get!_eq_getElem? [Inhabited α] (a : Array α) (i : Nat) :
     a.get! i = (a.get? i).getD default := by
   by_cases p : i < a.size <;>
   simp only [get!_eq_getD, getD_eq_get?, getD_getElem?, p, get?_eq_getElem?]
@@ -1182,12 +1066,44 @@ theorem ofFn_succ (f : Fin (n+1) → α) :
       simp at h₁ h₂
       omega
 
+/-! # mkArray -/
+
+@[simp] theorem size_mkArray (n : Nat) (v : α) : (mkArray n v).size = n :=
+  List.length_replicate ..
+
+@[simp] theorem toList_mkArray (n : Nat) (v : α) : (mkArray n v).toList = List.replicate n v := rfl
+
+theorem mkArray_eq_toArray_replicate (n : Nat) (v : α) : mkArray n v = (List.replicate n v).toArray := rfl
+
+@[simp] theorem getElem_mkArray (n : Nat) (v : α) (h : i < (mkArray n v).size) :
+    (mkArray n v)[i] = v := by simp [← getElem_toList]
+
+theorem getElem?_mkArray (n : Nat) (v : α) (i : Nat) :
+    (mkArray n v)[i]? = if i < n then some v else none := by
+  simp [getElem?_def]
+
 /-! # mem -/
 
 @[simp] theorem mem_toList {a : α} {l : Array α} : a ∈ l.toList ↔ a ∈ l := mem_def.symm
 
 theorem not_mem_nil (a : α) : ¬ a ∈ #[] := nofun
 
+@[simp] theorem mem_dite_empty_left {x : α} [Decidable p] {l : ¬ p → Array α} :
+    (x ∈ if h : p then #[] else l h) ↔ ∃ h : ¬ p, x ∈ l h := by
+  split <;> simp_all
+
+@[simp] theorem mem_dite_empty_right {x : α} [Decidable p] {l : p → Array α} :
+    (x ∈ if h : p then l h else #[]) ↔ ∃ h : p, x ∈ l h := by
+  split <;> simp_all
+
+@[simp] theorem mem_ite_empty_left {x : α} [Decidable p] {l : Array α} :
+    (x ∈ if p then #[] else l) ↔ ¬ p ∧ x ∈ l := by
+  split <;> simp_all
+
+@[simp] theorem mem_ite_empty_right {x : α} [Decidable p] {l : Array α} :
+    (x ∈ if p then l else #[]) ↔ p ∧ x ∈ l := by
+  split <;> simp_all
+
 /-! # get lemmas -/
 
 theorem lt_of_getElem {x : α} {a : Array α} {idx : Nat} {hidx : idx < a.size} (_ : a[idx] = x) :
@@ -1244,6 +1160,8 @@ theorem getElem?_push_eq (a : Array α) (x : α) : (a.push x)[a.size]? = some x
 
 @[deprecated getElem?_size (since := "2024-10-21")] abbrev get?_size := @getElem?_size
 
+@[simp] theorem toList_set (a : Array α) (i v h) : (a.set i v).toList = a.toList.set i v := rfl
+
 theorem get_set_eq (a : Array α) (i : Nat) (v : α) (h : i < a.size) :
     (a.set i v h)[i]'(by simp [h]) = v := by
   simp only [set, ← getElem_toList, List.getElem_set_self]
@@ -1283,8 +1201,8 @@ theorem getElem?_swap (a : Array α) (i j : Nat) (hi hj) (k : Nat) : (a.swap i j
 @[simp] theorem swapAt_def (a : Array α) (i : Nat) (v : α) (hi) :
     a.swapAt i v hi = (a[i], a.set i v) := rfl
 
-theorem size_swapAt (a : Array α) (i : Nat) (v : α) (hi) :
-    (a.swapAt i v hi).2.size = a.size := by simp
+@[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 swapAt!_def (a : Array α) (i : Nat) (v : α) (h : i < a.size) :
@@ -1393,6 +1311,43 @@ theorem getElem_range {n : Nat} {x : Nat} (h : x < (Array.range n).size) : (Arra
         true_and, Nat.not_lt] at h
       rw [List.getElem?_eq_none_iff.2 ‹_›, List.getElem?_eq_none_iff.2 (a.toList.length_reverse ▸ ‹_›)]
 
+/-! ### BEq -/
+
+@[simp] theorem reflBEq_iff [BEq α] : ReflBEq (Array α) ↔ ReflBEq α := by
+  constructor
+  · intro h
+    constructor
+    intro a
+    suffices (#[a] == #[a]) = true by
+      simpa only [instBEq, isEqv, isEqvAux, Bool.and_true]
+    simp
+  · intro h
+    constructor
+    apply Array.isEqv_self_beq
+
+@[simp] theorem lawfulBEq_iff [BEq α] : LawfulBEq (Array α) ↔ LawfulBEq α := by
+  constructor
+  · intro h
+    constructor
+    · intro a b h
+      apply singleton_inj.1
+      apply eq_of_beq
+      simp only [instBEq, isEqv, isEqvAux]
+      simpa
+    · intro a
+      suffices (#[a] == #[a]) = true by
+        simpa only [instBEq, isEqv, isEqvAux, Bool.and_true]
+      simp
+  · intro h
+    constructor
+    · intro a b h
+      obtain ⟨hs, hi⟩ := rel_of_isEqv h
+      ext i h₁ h₂
+      · exact hs
+      · simpa using hi _ h₁
+    · intro a
+      apply Array.isEqv_self_beq
+
 /-! ### take -/
 
 @[simp] theorem size_take_loop (a : Array α) (n : Nat) : (take.loop n a).size = a.size - n := by
@@ -1741,9 +1696,13 @@ theorem mem_append_right {a : α} (l₁ : Array α) {l₂ : Array α} (h : a ∈
 @[simp] theorem size_append (as bs : Array α) : (as ++ bs).size = as.size + bs.size := by
   simp only [size, toList_append, List.length_append]
 
-theorem empty_append (as : Array α) : #[] ++ as = as := by simp
+@[simp] theorem empty_append (as : Array α) : #[] ++ as = as := by
+  cases as
+  simp
 
-theorem append_empty (as : Array α) : as ++ #[] = as := by simp
+@[simp] theorem append_empty (as : Array α) : as ++ #[] = as := by
+  cases as
+  simp
 
 theorem getElem_append {as bs : Array α} (h : i < (as ++ bs).size) :
     (as ++ bs)[i] = if h' : i < as.size then as[i] else bs[i - as.size]'(by simp at h; omega) := by
@@ -1757,28 +1716,29 @@ theorem getElem_append_left {as bs : Array α} {h : i < (as ++ bs).size} (hlt :
   conv => rhs; rw [← List.getElem_append_left (bs := bs.toList) (h' := h')]
   apply List.get_of_eq; rw [toList_append]
 
-theorem getElem_append_right {as bs : Array α} {h : i < (as ++ bs).size} (hle : as.size ≤ i) :
-    (as ++ bs)[i] = bs[i - as.size]'(Nat.sub_lt_left_of_lt_add hle (size_append .. ▸ h)) := by
+theorem getElem_append_right {as bs : Array α} {h : i < (as ++ bs).size} (hle : as.size ≤ i)
+    (hlt : i - as.size < bs.size := Nat.sub_lt_left_of_lt_add hle (size_append .. ▸ h)) :
+    (as ++ bs)[i] = bs[i - as.size] := by
   simp only [← getElem_toList]
   have h' : i < (as.toList ++ bs.toList).length := by rwa [← length_toList, toList_append] at h
   conv => rhs; rw [← List.getElem_append_right (h₁ := hle) (h₂ := h')]
   apply List.get_of_eq; rw [toList_append]
 
-theorem getElem?_append_left {as bs : Array α} {i : Nat} (hn : i < as.size) :
-    (as ++ bs)[i]? = as[i]? := by
-  have hn' : i < (as ++ bs).size := Nat.lt_of_lt_of_le hn <|
+theorem getElem?_append_left {as bs : Array α} {n : Nat} (hn : n < as.size) :
+    (as ++ bs)[n]? = as[n]? := by
+  have hn' : n < (as ++ bs).size := Nat.lt_of_lt_of_le hn <|
     size_append .. ▸ Nat.le_add_right ..
   simp_all [getElem?_eq_getElem, getElem_append]
 
-theorem getElem?_append_right {as bs : Array α} {i : Nat} (h : as.size ≤ i) :
-    (as ++ bs)[i]? = bs[i - as.size]? := by
+theorem getElem?_append_right {as bs : Array α} {n : Nat} (h : as.size ≤ n) :
+    (as ++ bs)[n]? = bs[n - as.size]? := by
   cases as
   cases bs
   simp at h
   simp [List.getElem?_append_right, h]
 
-theorem getElem?_append {as bs : Array α} {i : Nat} :
-    (as ++ bs)[i]? = if i < as.size then as[i]? else bs[i - as.size]? := by
+theorem getElem?_append {as bs : Array α} {n : Nat} :
+    (as ++ bs)[n]? = if n < as.size then as[n]? else bs[n - as.size]? := by
   split <;> rename_i h
   · exact getElem?_append_left h
   · exact getElem?_append_right (by simpa using h)
@@ -2098,10 +2058,12 @@ namespace List
 Our goal is to have `simp` "pull `List.toArray` outwards" as much as possible.
 -/
 
-theorem toListRev_toArray (l : List α) : l.toArray.toListRev = l.reverse := by simp
+@[simp] theorem toListRev_toArray (l : List α) : l.toArray.toListRev = l.reverse := by
+  simp
 
 @[simp] theorem take_toArray (l : List α) (n : Nat) : l.toArray.take n = (l.take n).toArray := by
-  apply Array.ext <;> simp
+  apply ext'
+  simp
 
 @[simp] theorem mapM_toArray [Monad m] [LawfulMonad m] (f : α → m β) (l : List α) :
     l.toArray.mapM f = List.toArray <$> l.mapM f := by
@@ -2121,8 +2083,10 @@ theorem toListRev_toArray (l : List α) : l.toArray.toListRev = l.reverse := by
   apply ext'
   simp
 
-theorem uset_toArray (l : List α) (i : USize) (a : α) (h : i.toNat < l.toArray.size) :
-    l.toArray.uset i a h = (l.set i.toNat a).toArray := by simp
+@[simp] theorem uset_toArray (l : List α) (i : USize) (a : α) (h : i.toNat < l.toArray.size) :
+    l.toArray.uset i a h = (l.set i.toNat a).toArray := by
+  apply ext'
+  simp
 
 @[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
@@ -2158,8 +2122,7 @@ theorem filterMap_toArray (f : α → Option β) (l : List α) :
     l.toArray.filterMap f = (l.filterMap f).toArray := by
   simp
 
-@[simp] theorem flatten_toArray (l : List (List α)) :
-    (l.toArray.map List.toArray).flatten = l.flatten.toArray := by
+@[simp] theorem flatten_toArray (l : List (List α)) : (l.toArray.map List.toArray).flatten = l.flatten.toArray := by
   apply ext'
   simp [Function.comp_def]
 
@@ -2355,12 +2318,6 @@ theorem foldr_map' (g : α → β) (f : α → α → α) (f' : β → β → β
   rw [← List.foldl_hom (f := Prod.snd) (g₂ := fun bs x => bs.push x.2) (H := by simp), ← List.foldl_map]
   simp
 
-/-! ### take -/
-
-@[simp] theorem take_size (a : Array α) : a.take a.size = a := by
-  cases a
-  simp
-
 end Array
 
 namespace List
@@ -2373,15 +2330,19 @@ end List
 
 namespace Array
 
-theorem toList_fst_unzip (as : Array (α × β)) :
-    as.unzip.1.toList = as.toList.unzip.1 := by simp
+@[simp] theorem toList_fst_unzip (as : Array (α × β)) :
+    as.unzip.1.toList = as.toList.unzip.1 := by
+  cases as
+  simp
 
-theorem toList_snd_unzip (as : Array (α × β)) :
-    as.unzip.2.toList = as.toList.unzip.2 := by simp
+@[simp] theorem toList_snd_unzip (as : Array (α × β)) :
+    as.unzip.2.toList = as.toList.unzip.2 := by
+  cases as
+  simp
 
 @[simp] theorem flatMap_empty {β} (f : α → Array β) : (#[] : Array α).flatMap f = #[] := rfl
 
-theorem flatMap_toArray_cons {β} (f : α → Array β) (a : α) (as : List α) :
+@[simp] theorem flatMap_toArray_cons {β} (f : α → Array β) (a : α) (as : List α) :
     (a :: as).toArray.flatMap f = f a ++ as.toArray.flatMap f := by
   simp [flatMap]
   suffices ∀ cs, List.foldl (fun bs a => bs ++ f a) (f a ++ cs) as =
@@ -2397,7 +2358,8 @@ theorem flatMap_toArray_cons {β} (f : α → Array β) (a : α) (as : List α)
   | nil => simp
   | cons a as ih =>
     apply ext'
-    simp [ih, flatMap_toArray_cons]
+    simp [ih]
+
 
 end Array
 
@@ -2442,7 +2404,7 @@ abbrev get?_eq_toList_get? := @get?_eq_get?_toList
 @[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!_eq_setIfInBounds
+@[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_self
 @[deprecated getElem?_setIfInBounds_eq (since := "2024-11-24")] abbrev get?_setD_eq := @getElem?_setIfInBounds_self

src/Init/Data/Array/Lex.lean

@@ -1,8 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Author: Kim Morrison
--/
-prelude
-import Init.Data.Array.Lex.Basic
-import Init.Data.Array.Lex.Lemmas

src/Init/Data/Array/Lex/Basic.lean

@@ -1,30 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Author: Kim Morrison
--/
-prelude
-import Init.Data.Array.Basic
-import Init.Data.Nat.Lemmas
-import Init.Data.Range
-
-namespace Array
-
-/--
-Lexicographic comparator for arrays.
-
-`lex as bs lt` is true if
-- `bs` is larger than `as` and `as` is pairwise equivalent via `==` to the initial segment of `bs`, or
-- there is an index `i` such that `lt as[i] bs[i]`, and for all `j < i`, `as[j] == bs[j]`.
--/
-def lex [BEq α] (as bs : Array α) (lt : α → α → Bool := by exact (· < ·)) : Bool := Id.run do
-  for h : i in [0 : min as.size bs.size] do
-    -- TODO: `omega` should be able to find this itself.
-    have : i < min as.size bs.size := Membership.get_elem_helper h rfl
-    if lt as[i] bs[i] then
-      return true
-    else if as[i] != bs[i] then
-      return false
-  return as.size < bs.size
-
-end Array

src/Init/Data/Array/Lex/Lemmas.lean

@@ -1,216 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Author: Kim Morrison
--/
-prelude
-import Init.Data.Array.Lemmas
-import Init.Data.List.Lex
-
-namespace Array
-
-/-! ### Lexicographic ordering -/
-
-@[simp] theorem lt_toArray [LT α] (l₁ l₂ : List α) : l₁.toArray < l₂.toArray ↔ l₁ < l₂ := Iff.rfl
-@[simp] theorem le_toArray [LT α] (l₁ l₂ : List α) : l₁.toArray ≤ l₂.toArray ↔ l₁ ≤ l₂ := Iff.rfl
-
-theorem not_lt_iff_ge [LT α] (l₁ l₂ : List α) : ¬ l₁ < l₂ ↔ l₂ ≤ l₁ := Iff.rfl
-theorem not_le_iff_gt [DecidableEq α] [LT α] [DecidableLT α] (l₁ l₂ : List α) :
-    ¬ l₁ ≤ l₂ ↔ l₂ < l₁ :=
-  Decidable.not_not
-
-@[simp] theorem lex_empty [BEq α] {lt : α → α → Bool} (l : Array α) : l.lex #[] lt = false := by
-  simp [lex, Id.run]
-
-@[simp] theorem singleton_lex_singleton [BEq α] {lt : α → α → Bool} : #[a].lex #[b] lt = lt a b := by
-  simp only [lex, List.getElem_toArray, List.getElem_singleton]
-  cases lt a b <;> cases a != b <;> simp [Id.run]
-
-private theorem cons_lex_cons [BEq α] {lt : α → α → Bool} {a b : α} {xs ys : Array α} :
-     (#[a] ++ xs).lex (#[b] ++ ys) lt =
-       (lt a b || a == b && xs.lex ys lt) := by
-  simp only [lex, Id.run]
-  simp only [Std.Range.forIn'_eq_forIn'_range', size_append, size_toArray, List.length_singleton,
-    Nat.add_comm 1]
-  simp [Nat.add_min_add_right, List.range'_succ, getElem_append_left, List.range'_succ_left,
-    getElem_append_right]
-  cases lt a b
-  · rw [bne]
-    cases a == b <;> simp
-  · simp
-
-@[simp] theorem _root_.List.lex_toArray [BEq α] (lt : α → α → Bool) (l₁ l₂ : List α) :
-    l₁.toArray.lex l₂.toArray lt = l₁.lex l₂ lt := by
-  induction l₁ generalizing l₂ with
-  | nil => cases l₂ <;> simp [lex, Id.run]
-  | cons x l₁ ih =>
-    cases l₂ with
-    | nil => simp [lex, Id.run]
-    | cons y l₂ =>
-      rw [List.toArray_cons, List.toArray_cons y, cons_lex_cons, List.lex, ih]
-
-@[simp] theorem lex_toList [BEq α] (lt : α → α → Bool) (l₁ l₂ : Array α) :
-    l₁.toList.lex l₂.toList lt = l₁.lex l₂ lt := by
-  cases l₁ <;> cases l₂ <;> simp
-
-protected theorem lt_irrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] (l : Array α) : ¬ l < l :=
-  List.lt_irrefl l.toList
-
-instance ltIrrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Irrefl (α := Array α) (· < ·) where
-  irrefl := Array.lt_irrefl
-
-@[simp] theorem empty_le [LT α] (l : Array α) : #[] ≤ l := List.nil_le l.toList
-
-@[simp] theorem le_empty [LT α] (l : Array α) : l ≤ #[] ↔ l = #[] := by
-  cases l
-  simp
-
-@[simp] theorem empty_lt_push [LT α] (l : Array α) (a : α) : #[] < l.push a := by
-  rcases l with (_ | ⟨x, l⟩) <;> simp
-
-protected theorem le_refl [LT α] [i₀ : Std.Irrefl (· < · : α → α → Prop)] (l : Array α) : l ≤ l :=
-  List.le_refl l.toList
-
-instance [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Refl (· ≤ · : Array α → Array α → Prop) where
-  refl := Array.le_refl
-
-protected theorem lt_trans [LT α] [DecidableLT α]
-    [i₁ : Trans (· < · : α → α → Prop) (· < ·) (· < ·)]
-    {l₁ l₂ l₃ : Array α} (h₁ : l₁ < l₂) (h₂ : l₂ < l₃) : l₁ < l₃ :=
-  List.lt_trans h₁ h₂
-
-instance [LT α] [DecidableLT α]
-    [Trans (· < · : α → α → Prop) (· < ·) (· < ·)] :
-    Trans (· < · : Array α → Array α → Prop) (· < ·) (· < ·) where
-  trans h₁ h₂ := Array.lt_trans h₁ h₂
-
-protected theorem lt_of_le_of_lt [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    [i₃ : Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : Array α} (h₁ : l₁ ≤ l₂) (h₂ : l₂ < l₃) : l₁ < l₃ :=
-  List.lt_of_le_of_lt h₁ h₂
-
-protected theorem le_trans [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : Array α} (h₁ : l₁ ≤ l₂) (h₂ : l₂ ≤ l₃) : l₁ ≤ l₃ :=
-  fun h₃ => h₁ (Array.lt_of_le_of_lt h₂ h₃)
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)] :
-    Trans (· ≤ · : Array α → Array α → Prop) (· ≤ ·) (· ≤ ·) where
-  trans h₁ h₂ := Array.le_trans h₁ h₂
-
-protected theorem lt_asymm [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Asymm (· < · : α → α → Prop)]
-    {l₁ l₂ : Array α} (h : l₁ < l₂) : ¬ l₂ < l₁ := List.lt_asymm h
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Asymm (· < · : α → α → Prop)] :
-    Std.Asymm (· < · : Array α → Array α → Prop) where
-  asymm _ _ := Array.lt_asymm
-
-protected theorem le_total [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Total (¬ · < · : α → α → Prop)] {l₁ l₂ : Array α} : l₁ ≤ l₂ ∨ l₂ ≤ l₁ :=
-  List.le_total
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Total (¬ · < · : α → α → Prop)] :
-    Std.Total (· ≤ · : Array α → Array α → Prop) where
-  total _ _ := Array.le_total
-
-@[simp] theorem lex_eq_true_iff_lt [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : Array α} : lex l₁ l₂ = true ↔ l₁ < l₂ := by
-  cases l₁
-  cases l₂
-  simp
-
-@[simp] theorem lex_eq_false_iff_ge [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : Array α} : lex l₁ l₂ = false ↔ l₂ ≤ l₁ := by
-  cases l₁
-  cases l₂
-  simp [List.not_lt_iff_ge]
-
-instance [DecidableEq α] [LT α] [DecidableLT α] : DecidableLT (Array α) :=
-  fun l₁ l₂ => decidable_of_iff (lex l₁ l₂ = true) lex_eq_true_iff_lt
-
-instance [DecidableEq α] [LT α] [DecidableLT α] : DecidableLE (Array α) :=
-  fun l₁ l₂ => decidable_of_iff (lex l₂ l₁ = false) lex_eq_false_iff_ge
-
-/--
-`l₁` is lexicographically less than `l₂` if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.size`,
-  and `l₁` is shorter than `l₂` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₁[i] < l₂[i]`
--/
-theorem lex_eq_true_iff_exists [BEq α] (lt : α → α → Bool) :
-    lex l₁ l₂ lt = true ↔
-      (l₁.isEqv (l₂.take l₁.size) (· == ·) ∧ l₁.size < l₂.size) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.size) (h₂ : i < l₂.size),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) == l₂[j]'(Nat.lt_trans hj h₂)) ∧ lt l₁[i] l₂[i]) := by
-  cases l₁
-  cases l₂
-  simp [List.lex_eq_true_iff_exists]
-
-/--
-`l₁` is *not* lexicographically less than `l₂`
-(which you might think of as "`l₂` is lexicographically greater than or equal to `l₁`"") if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.length` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₂[i] < l₁[i]`
-
-This formulation requires that `==` and `lt` are compatible in the following senses:
-- `==` is symmetric
-  (we unnecessarily further assume it is transitive, to make use of the existing typeclasses)
-- `lt` is irreflexive with respect to `==` (i.e. if `x == y` then `lt x y = false`
-- `lt` is asymmmetric  (i.e. `lt x y = true → lt y x = false`)
-- `lt` is antisymmetric with respect to `==` (i.e. `lt x y = false → lt y x = false → x == y`)
--/
-theorem lex_eq_false_iff_exists [BEq α] [PartialEquivBEq α] (lt : α → α → Bool)
-    (lt_irrefl : ∀ x y, x == y → lt x y = false)
-    (lt_asymm : ∀ x y, lt x y = true → lt y x = false)
-    (lt_antisymm : ∀ x y, lt x y = false → lt y x = false → x == y) :
-    lex l₁ l₂ lt = false ↔
-      (l₂.isEqv (l₁.take l₂.size) (· == ·)) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.size) (h₂ : i < l₂.size),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) == l₂[j]'(Nat.lt_trans hj h₂)) ∧ lt l₂[i] l₁[i]) := by
-  cases l₁
-  cases l₂
-  simp_all [List.lex_eq_false_iff_exists]
-
-theorem lt_iff_exists [DecidableEq α] [LT α] [DecidableLT α] {l₁ l₂ : Array α} :
-    l₁ < l₂ ↔
-      (l₁ = l₂.take l₁.size ∧ l₁.size < l₂.size) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.size) (h₂ : i < l₂.size),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) = l₂[j]'(Nat.lt_trans hj h₂)) ∧ l₁[i] < l₂[i]) := by
-  cases l₁
-  cases l₂
-  simp [List.lt_iff_exists]
-
-theorem le_iff_exists [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)] {l₁ l₂ : Array α} :
-    l₁ ≤ l₂ ↔
-      (l₁ = l₂.take l₁.size) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.size) (h₂ : i < l₂.size),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) = l₂[j]'(Nat.lt_trans hj h₂)) ∧ l₁[i] < l₂[i]) := by
-  cases l₁
-  cases l₂
-  simp [List.le_iff_exists]
-
-end Array

src/Init/Data/Array/Monadic.lean

@@ -79,31 +79,8 @@ theorem foldrM_filter [Monad m] [LawfulMonad m] (p : α → Bool) (g : α → β
   rw [List.filter_toArray] -- Why doesn't this fire via `simp`?
   simp [List.foldrM_filter]
 
-/-! ### forM -/
-
-@[congr] theorem forM_congr [Monad m] {as bs : Array α} (w : as = bs)
-    {f : α → m PUnit} :
-    forM f as = forM f bs := by
-  cases as <;> cases bs
-  simp_all
-
-@[simp] theorem forM_map [Monad m] [LawfulMonad m] (l : Array α) (g : α → β) (f : β → m PUnit) :
-    (l.map g).forM f = l.forM (fun a => f (g a)) := by
-  cases l
-  simp
-
 /-! ### forIn' -/
 
-@[congr] theorem forIn'_congr [Monad m] {as bs : Array α} (w : as = bs)
-    {b b' : β} (hb : b = b')
-    {f : (a' : α) → a' ∈ as → β → m (ForInStep β)}
-    {g : (a' : α) → a' ∈ bs → β → m (ForInStep β)}
-    (h : ∀ a m b, f a (by simpa [w] using m) b = g a m b) :
-    forIn' as b f = forIn' bs b' g := by
-  cases as <;> cases bs
-  simp only [mk.injEq, mem_toArray, List.forIn'_toArray] at w h ⊢
-  exact List.forIn'_congr w hb h
-
 /--
 We can express a for loop over an array as a fold,
 in which whenever we reach `.done b` we keep that value through the rest of the fold.
@@ -143,12 +120,6 @@ theorem forIn'_pure_yield_eq_foldl [Monad m] [LawfulMonad m]
   cases l
   simp [List.foldl_map]
 
-@[simp] theorem forIn'_map [Monad m] [LawfulMonad m]
-    (l : Array α) (g : α → β) (f : (b : β) → b ∈ l.map g → γ → m (ForInStep γ)) :
-    forIn' (l.map g) init f = forIn' l init fun a h y => f (g a) (mem_map_of_mem g h) y := by
-  cases l
-  simp
-
 /--
 We can express a for loop over an array as a fold,
 in which whenever we reach `.done b` we keep that value through the rest of the fold.
@@ -185,10 +156,4 @@ theorem forIn_pure_yield_eq_foldl [Monad m] [LawfulMonad m]
   cases l
   simp [List.foldl_map]
 
-@[simp] theorem forIn_map [Monad m] [LawfulMonad m]
-    (l : Array α) (g : α → β) (f : β → γ → m (ForInStep γ)) :
-    forIn (l.map g) init f = forIn l init fun a y => f (g a) y := by
-  cases l
-  simp
-
 end Array

src/Init/Data/BitVec/Lemmas.lean

@@ -332,11 +332,11 @@ theorem getLsbD_ofNat (n : Nat) (x : Nat) (i : Nat) :
 private theorem lt_two_pow_of_le {x m n : Nat} (lt : x < 2 ^ m) (le : m ≤ n) : x < 2 ^ n :=
   Nat.lt_of_lt_of_le lt (Nat.pow_le_pow_of_le_right (by trivial : 0 < 2) le)
 
-theorem getElem_zero_ofNat_zero (i : Nat) (h : i < w) : (BitVec.ofNat w 0)[i] = false := by
-  simp
+@[simp] theorem getElem_zero_ofNat_zero (i : Nat) (h : i < w) : (BitVec.ofNat w 0)[i] = false := by
+  simp [getElem_eq_testBit_toNat]
 
-theorem getElem_zero_ofNat_one (h : 0 < w) : (BitVec.ofNat w 1)[0] = true := by
-  simp
+@[simp] theorem getElem_zero_ofNat_one (h : 0 < w) : (BitVec.ofNat w 1)[0] = true := by
+  simp [getElem_eq_testBit_toNat, h]
 
 theorem getElem?_zero_ofNat_zero : (BitVec.ofNat (w+1) 0)[0]? = some false := by
   simp
@@ -362,7 +362,12 @@ theorem getLsbD_ofBool (b : Bool) (i : Nat) : (ofBool b).getLsbD i = ((i = 0) &&
   · simp only [ofBool, ofNat_eq_ofNat, cond_true, getLsbD_ofNat, Bool.and_true]
     by_cases hi : i = 0 <;> simp [hi] <;> omega
 
-theorem getElem_ofBool {b : Bool} : (ofBool b)[0] = b := by simp
+@[simp]
+theorem getElem_ofBool {b : Bool} {i : Nat} : (ofBool b)[0] = b := by
+  rcases b with rfl | rfl
+  · simp [ofBool]
+  · simp only [ofBool]
+    by_cases hi : i = 0 <;> simp [hi] <;> omega
 
 @[simp] theorem getMsbD_ofBool (b : Bool) : (ofBool b).getMsbD i = (decide (i = 0) && b) := by
   cases b <;> simp [getMsbD]
@@ -533,7 +538,7 @@ theorem toInt_zero {w : Nat} : (0#w).toInt = 0 := by
 A bitvector, when interpreted as an integer, is less than zero iff
 its most significant bit is true.
 -/
-theorem slt_zero_iff_msb_cond {x : BitVec w} : x.slt 0#w ↔ x.msb = true := by
+theorem slt_zero_iff_msb_cond (x : BitVec w) : x.slt 0#w ↔ x.msb = true := by
   have := toInt_eq_msb_cond x
   constructor
   · intros h
@@ -1115,8 +1120,12 @@ theorem not_eq_comm {x y : BitVec w} : ~~~ x = y ↔ x = ~~~ y := by
     rw [h]
     simp
 
-theorem getMsb_not {x : BitVec w} :
-    (~~~x).getMsbD i = (decide (i < w) && !(x.getMsbD i)) := by simp
+@[simp] theorem getMsb_not {x : BitVec w} :
+    (~~~x).getMsbD i = (decide (i < w) && !(x.getMsbD i)) := by
+  simp only [getMsbD]
+  by_cases h : i < w
+  · simp [h]; omega
+  · simp [h];
 
 @[simp] theorem msb_not {x : BitVec w} : (~~~x).msb = (decide (0 < w) && !x.msb) := by
   simp [BitVec.msb]
@@ -1234,6 +1243,7 @@ theorem shiftLeftZeroExtend_eq {x : BitVec w} :
 
 @[simp] theorem getMsbD_shiftLeftZeroExtend (x : BitVec m) (n : Nat) :
     getMsbD (shiftLeftZeroExtend x n) i = getMsbD x i := by
+  have : n ≤ i + n := by omega
   simp_all [shiftLeftZeroExtend_eq]
 
 @[simp] theorem msb_shiftLeftZeroExtend (x : BitVec w) (i : Nat) :
@@ -1281,9 +1291,10 @@ theorem getLsbD_shiftLeft' {x : BitVec w₁} {y : BitVec w₂} {i : Nat} :
     (x <<< y).getLsbD i = (decide (i < w₁) && !decide (i < y.toNat) && x.getLsbD (i - y.toNat)) := by
   simp [shiftLeft_eq', getLsbD_shiftLeft]
 
+@[simp]
 theorem getElem_shiftLeft' {x : BitVec w₁} {y : BitVec w₂} {i : Nat} (h : i < w₁) :
     (x <<< y)[i] = (!decide (i < y.toNat) && x.getLsbD (i - y.toNat)) := by
-  simp
+  simp [shiftLeft_eq', getLsbD_shiftLeft]
 
 /-! ### ushiftRight -/
 
@@ -1586,25 +1597,39 @@ theorem getMsbD_sshiftRight {x : BitVec w} {i n : Nat} :
 @[simp]
 theorem sshiftRight_eq' (x : BitVec w) : x.sshiftRight' y = x.sshiftRight y.toNat := rfl
 
--- This should not be a `@[simp]` lemma as the left hand side is not in simp normal form.
-theorem getLsbD_sshiftRight' {x y : BitVec w} {i : Nat} :
+@[simp]
+theorem getLsbD_sshiftRight' {x y: BitVec w} {i : Nat} :
     getLsbD (x.sshiftRight' y) i =
       (!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]
 
--- This should not be a `@[simp]` lemma as the left hand side is not in simp normal form.
+@[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
-  simp
+    (x.sshiftRight y.toNat).getMsbD i = (decide (i < w) && if i < y.toNat then x.msb else x.getMsbD (i - y.toNat)) := by
+  simp only [BitVec.sshiftRight', getMsbD, BitVec.getLsbD_sshiftRight]
+  by_cases h : i < w
+  · simp only [h, decide_true, Bool.true_and]
+    by_cases h₁ : w ≤ w - 1 - i
+    · simp [h₁]
+      omega
+    · simp only [h₁, decide_false, Bool.not_false, Bool.true_and]
+      by_cases h₂ : i < y.toNat
+      · simp only [h₂, ↓reduceIte, ite_eq_right_iff]
+        omega
+      · simp only [show i - y.toNat < w by omega, h₂, ↓reduceIte, decide_true, Bool.true_and]
+        by_cases h₄ : y.toNat + (w - 1 - i) < w <;> (simp only [h₄, ↓reduceIte]; congr; omega)
+  · simp [h]
 
+@[simp]
 theorem msb_sshiftRight' {x y: BitVec w} :
-    (x.sshiftRight' y).msb = x.msb := by simp
+    (x.sshiftRight' y).msb = x.msb := by
+  simp [BitVec.sshiftRight', BitVec.msb_sshiftRight]
 
 /-! ### signExtend -/
 
@@ -1858,6 +1883,7 @@ theorem setWidth_append {x : BitVec w} {y : BitVec v} :
   · simp_all
   · simp_all only [Bool.iff_and_self, decide_eq_true_eq]
     intro h
+    have := BitVec.lt_of_getLsbD h
     omega
 
 @[simp] theorem setWidth_cons {x : BitVec w} : (cons a x).setWidth w = x := by
@@ -2065,9 +2091,8 @@ theorem getElem_concat (x : BitVec w) (b : Bool) (i : Nat) (h : i < w + 1) :
 @[simp] theorem getLsbD_concat_succ : (concat x b).getLsbD (i + 1) = x.getLsbD i := by
   simp [getLsbD_concat]
 
-@[simp] theorem getElem_concat_succ {x : BitVec w} {i : Nat} (h : i + 1 < w + 1) :
+@[simp] theorem getElem_concat_succ {x : BitVec w} {i : Nat} (h : i < w) :
     (concat x b)[i + 1] = x[i] := by
-  simp only [Nat.add_lt_add_iff_right] at h
   simp [getElem_concat, h, getLsbD_eq_getElem]
 
 @[simp]
@@ -2170,6 +2195,7 @@ theorem toNat_shiftConcat_lt_of_lt {x : BitVec w} {b : Bool} {k : Nat}
     (hk : k < w) (hx : x.toNat < 2 ^ k) :
     (x.shiftConcat b).toNat < 2 ^ (k + 1) := by
   rw [toNat_shiftConcat_eq_of_lt hk hx]
+  have : 2 ^ (k + 1) ≤ 2 ^ w := Nat.pow_le_pow_of_le_right (by decide) (by assumption)
   have := Bool.toNat_lt b
   omega
 
@@ -2678,7 +2704,7 @@ theorem smtSDiv_eq (x y : BitVec w) : smtSDiv x y =
 
 @[simp]
 theorem smtSDiv_zero {x : BitVec n} : x.smtSDiv 0#n = if x.slt 0#n then 1#n else (allOnes n) := by
-  rcases hx : x.msb <;> simp [smtSDiv, slt_zero_iff_msb_cond, hx, ← negOne_eq_allOnes]
+  rcases hx : x.msb <;> simp [smtSDiv, slt_zero_iff_msb_cond x, hx, ← negOne_eq_allOnes]
 
 /-! ### srem -/
 
@@ -2998,10 +3024,10 @@ theorem getMsbD_rotateRightAux_of_ge {x : BitVec w} {r : Nat} {i : Nat} (hi : i
   simp [rotateRightAux, show ¬ i < r by omega, show i + (w - r) ≥ w by omega]
 
 /-- When `m < w`, we give a formula for `(x.rotateLeft m).getMsbD i`. -/
--- This should not be a simp lemma as `getMsbD_rotateRight` will apply first.
-theorem getMsbD_rotateRight_of_lt {w n m : Nat} {x : BitVec w} (hr : m < w) :
+@[simp]
+theorem getMsbD_rotateRight_of_lt {w n m : Nat} {x : BitVec w} (hr : m < w):
     (x.rotateRight m).getMsbD n = (decide (n < w) && (if (n < m % w)
-    then x.getMsbD ((w + n - m % w) % w) else x.getMsbD (n - m % w))) := by
+    then x.getMsbD ((w + n - m % w) % w) else x.getMsbD (n - m % w))):= by
   rcases w with rfl | w
   · simp
   · rw [rotateRight_eq_rotateRightAux_of_lt (by omega)]
@@ -3564,7 +3590,9 @@ Note, however, that for large numerals the decision procedure may be very slow.
 instance instDecidableExistsBitVec :
     ∀ (n : Nat) (P : BitVec n → Prop) [DecidablePred P], Decidable (∃ v, P v)
   | 0, _, _ => inferInstance
-  | _ + 1, _, _ => inferInstance
+  | n + 1, _, _ =>
+    have := instDecidableExistsBitVec n
+    inferInstance
 
 /-! ### Deprecations -/
 

src/Init/Data/Bool.lean

@@ -225,7 +225,7 @@ theorem bne_not_self : ∀ (x : Bool), (x   != !x) = true := by decide
 Added for equivalence with `Bool.not_beq_self` and needed for confluence
 due to `beq_iff_eq`.
 -/
-theorem not_eq_self : ∀(b : Bool), ((!b) = b) ↔ False := by simp
+@[simp] theorem not_eq_self : ∀(b : Bool), ((!b) = b) ↔ False := by decide
 @[simp] theorem eq_not_self : ∀(b : Bool), (b = (!b)) ↔ False := by decide
 
 @[simp] theorem beq_self_left  : ∀(a b : Bool), (a == (a == b)) = b := by decide
@@ -420,7 +420,7 @@ def toInt (b : Bool) : Int := cond b 1 0
 
 @[simp] theorem ite_eq_true_else_eq_false {q : Prop} :
     (if b = true then q else b = false) ↔ (b = true → q) := by
-  cases b <;> simp [not_eq_self]
+  cases b <;> simp
 
 /-
 `not_ite_eq_true_eq_true` and related theorems below are added for

src/Init/Data/Char/Lemmas.lean

@@ -9,9 +9,6 @@ import Init.Data.UInt.Lemmas
 
 namespace Char
 
-@[ext] protected theorem ext : {a b : Char} → a.val = b.val → a = b
-  | ⟨_,_⟩, ⟨_,_⟩, rfl => rfl
-
 theorem le_def {a b : Char} : a ≤ b ↔ a.1 ≤ b.1 := .rfl
 theorem lt_def {a b : Char} : a < b ↔ a.1 < b.1 := .rfl
 theorem lt_iff_val_lt_val {a b : Char} : a < b ↔ a.val < b.val := Iff.rfl
@@ -22,44 +19,9 @@ theorem lt_iff_val_lt_val {a b : Char} : a < b ↔ a.val < b.val := Iff.rfl
 protected theorem le_trans {a b c : Char} : a ≤ b → b ≤ c → a ≤ c := UInt32.le_trans
 protected theorem lt_trans {a b c : Char} : a < b → b < c → a < c := UInt32.lt_trans
 protected theorem le_total (a b : Char) : a ≤ b ∨ b ≤ a := UInt32.le_total a.1 b.1
-protected theorem le_antisymm {a b : Char} : a ≤ b → b ≤ a → a = b :=
-  fun h₁ h₂ => Char.ext (UInt32.le_antisymm h₁ h₂)
 protected theorem lt_asymm {a b : Char} (h : a < b) : ¬ b < a := UInt32.lt_asymm h
 protected theorem ne_of_lt {a b : Char} (h : a < b) : a ≠ b := Char.ne_of_val_ne (UInt32.ne_of_lt h)
 
-instance ltIrrefl : Std.Irrefl (· < · : Char → Char → Prop) where
-  irrefl := Char.lt_irrefl
-
-instance leRefl : Std.Refl (· ≤ · : Char → Char → Prop) where
-  refl := Char.le_refl
-
-instance leTrans : Trans (· ≤ · : Char → Char → Prop) (· ≤ ·) (· ≤ ·) where
-  trans := Char.le_trans
-
-instance ltTrans : Trans (· < · : Char → Char → Prop) (· < ·) (· < ·) where
-  trans := Char.lt_trans
-
--- This instance is useful while setting up instances for `String`.
-def notLTTrans : Trans (¬ · < · : Char → Char → Prop) (¬ · < ·) (¬ · < ·) where
-  trans h₁ h₂ := by simpa using Char.le_trans (by simpa using h₂) (by simpa using h₁)
-
-instance leAntisymm : Std.Antisymm (· ≤ · : Char → Char → Prop) where
-  antisymm _ _ := Char.le_antisymm
-
--- This instance is useful while setting up instances for `String`.
-def notLTAntisymm : Std.Antisymm (¬ · < · : Char → Char → Prop) where
-  antisymm _ _ h₁ h₂ := Char.le_antisymm (by simpa using h₂) (by simpa using h₁)
-
-instance ltAsymm : Std.Asymm (· < · : Char → Char → Prop) where
-  asymm _ _ := Char.lt_asymm
-
-instance leTotal : Std.Total (· ≤ · : Char → Char → Prop) where
-  total := Char.le_total
-
--- This instance is useful while setting up instances for `String`.
-def notLTTotal : Std.Total (¬ · < · : Char → Char → Prop) where
-  total := fun x y => by simpa using Char.le_total y x
-
 theorem utf8Size_eq (c : Char) : c.utf8Size = 1 ∨ c.utf8Size = 2 ∨ c.utf8Size = 3 ∨ c.utf8Size = 4 := by
   have := c.utf8Size_pos
   have := c.utf8Size_le_four
@@ -69,6 +31,9 @@ theorem utf8Size_eq (c : Char) : c.utf8Size = 1 ∨ c.utf8Size = 2 ∨ c.utf8Siz
   rw [Char.ofNat, dif_pos]
   rfl
 
+@[ext] protected theorem ext : {a b : Char} → a.val = b.val → a = b
+  | ⟨_,_⟩, ⟨_,_⟩, rfl => rfl
+
 end Char
 
 @[deprecated Char.utf8Size (since := "2024-06-04")] abbrev String.csize := Char.utf8Size

src/Init/Data/Fin/Lemmas.lean

@@ -545,8 +545,10 @@ theorem natAdd_natAdd (m n : Nat) {p : Nat} (i : Fin p) :
     natAdd m (natAdd n i) = (natAdd (m + n) i).cast (Nat.add_assoc ..) :=
   Fin.ext <| (Nat.add_assoc ..).symm
 
+@[simp]
 theorem cast_natAdd_zero {n n' : Nat} (i : Fin n) (h : 0 + n = n') :
-    (natAdd 0 i).cast h = i.cast ((Nat.zero_add _).symm.trans h) := by simp
+    (natAdd 0 i).cast h = i.cast ((Nat.zero_add _).symm.trans h) :=
+  Fin.ext <| Nat.zero_add _
 
 @[simp]
 theorem cast_natAdd (n : Nat) {m : Nat} (i : Fin m) :

src/Init/Data/Float32.lean

@@ -9,6 +9,9 @@ import Init.Data.Int.Basic
 import Init.Data.ToString.Basic
 import Init.Data.Float
 
+/-
+#exit -- TODO: Remove after update stage0
+
 -- Just show FloatSpec is inhabited.
 opaque float32Spec : FloatSpec := {
   float := Unit,
@@ -127,7 +130,7 @@ Returns an undefined value if `x` is not finite.
 instance : ToString Float32 where
   toString := Float32.toString
 
-@[extern "lean_uint64_to_float32"] opaque UInt64.toFloat32 (n : UInt64) : Float32
+@[extern "lean_uint64_to_float"] opaque UInt64.toFloat32 (n : UInt64) : Float32
 
 instance : Inhabited Float32 where
   default := UInt64.toFloat32 0
@@ -174,6 +177,4 @@ Efficiently computes `x * 2^i`.
 -/
 @[extern "lean_float32_scaleb"]
 opaque Float32.scaleB (x : Float32) (i : @& Int) : Float32
-
-@[extern "lean_float32_to_float"] opaque Float32.toFloat : Float32 → Float
-@[extern "lean_float_to_float32"] opaque Float.toFloat32 : Float → Float32
+-/

src/Init/Data/Int/Basic.lean

@@ -7,7 +7,7 @@ The integers, with addition, multiplication, and subtraction.
 -/
 prelude
 import Init.Data.Cast
-import Init.Data.Nat.Div.Basic
+import Init.Data.Nat.Div
 
 set_option linter.missingDocs true -- keep it documented
 open Nat

src/Init/Data/List.lean

@@ -28,4 +28,3 @@ import Init.Data.List.ToArrayImpl
 import Init.Data.List.MapIdx
 import Init.Data.List.OfFn
 import Init.Data.List.FinRange
-import Init.Data.List.Lex

src/Init/Data/List/Attach.lean

@@ -118,6 +118,7 @@ theorem attach_map_coe (l : List α) (f : α → β) :
 theorem attach_map_val (l : List α) (f : α → β) : (l.attach.map fun i => f i.val) = l.map f :=
   attach_map_coe _ _
 
+@[simp]
 theorem attach_map_subtype_val (l : List α) : l.attach.map Subtype.val = l :=
   (attach_map_coe _ _).trans (List.map_id _)
 
@@ -129,6 +130,7 @@ theorem attachWith_map_val {p : α → Prop} (f : α → β) (l : List α) (H :
     ((l.attachWith p H).map fun i => f i.val) = l.map f :=
   attachWith_map_coe _ _ _
 
+@[simp]
 theorem attachWith_map_subtype_val {p : α → Prop} (l : List α) (H : ∀ a ∈ l, p a) :
     (l.attachWith p H).map Subtype.val = l :=
   (attachWith_map_coe _ _ _).trans (List.map_id _)
@@ -172,8 +174,8 @@ theorem pmap_ne_nil_iff {P : α → Prop} (f : (a : α) → P a → β) {xs : Li
     (H : ∀ (a : α), a ∈ xs → P a) : xs.pmap f H ≠ [] ↔ xs ≠ [] := by
   simp
 
-theorem pmap_eq_self {l : List α} {p : α → Prop} {hp : ∀ (a : α), a ∈ l → p a}
-    {f : (a : α) → p a → α} : l.pmap f hp = l ↔ ∀ a (h : a ∈ l), f a (hp a h) = a := by
+theorem pmap_eq_self {l : List α} {p : α → Prop} (hp : ∀ (a : α), a ∈ l → p a)
+    (f : (a : α) → p a → α) : l.pmap f hp = l ↔ ∀ a (h : a ∈ l), f a (hp a h) = a := by
   rw [pmap_eq_map_attach]
   conv => lhs; rhs; rw [← attach_map_subtype_val l]
   rw [map_inj_left]

src/Init/Data/List/Basic.lean

@@ -162,74 +162,46 @@ theorem isEqv_cons₂ : isEqv (a::as) (b::bs) eqv = (eqv a b && isEqv as bs eqv)
 
 /-! ## Lexicographic ordering -/
 
-/-- Lexicographic ordering for lists. -/
-inductive Lex (r : α → α → Prop) : List α → List α → Prop
+/--
+The lexicographic order on lists.
+`[] < a::as`, and `a::as < b::bs` if `a < b` or if `a` and `b` are equivalent and `as < bs`.
+-/
+inductive lt [LT α] : List α → List α → Prop where
   /-- `[]` is the smallest element in the order. -/
-  | nil {a l} : Lex r [] (a :: l)
-  /-- If `a` is indistinguishable from `b` and `as < bs`, then `a::as < b::bs`. -/
-  | cons {a l₁ l₂} (h : Lex r l₁ l₂) : Lex r (a :: l₁) (a :: l₂)
+  | nil  (b : α) (bs : List α) : lt [] (b::bs)
   /-- If `a < b` then `a::as < b::bs`. -/
-  | rel {a₁ l₁ a₂ l₂} (h : r a₁ a₂) : Lex r (a₁ :: l₁) (a₂ :: l₂)
+  | head {a : α} (as : List α) {b : α} (bs : List α) : a < b → lt (a::as) (b::bs)
+  /-- If `a` and `b` are equivalent and `as < bs`, then `a::as < b::bs`. -/
+  | tail {a : α} {as : List α} {b : α} {bs : List α} : ¬ a < b → ¬ b < a → lt as bs → lt (a::as) (b::bs)
 
-instance decidableLex [DecidableEq α] (r : α → α → Prop) [h : DecidableRel r] :
-    (l₁ l₂ : List α) → Decidable (Lex r l₁ l₂)
-  | [], [] => isFalse nofun
-  | [], _::_ => isTrue Lex.nil
-  | _::_, [] => isFalse nofun
+instance [LT α] : LT (List α) := ⟨List.lt⟩
+
+instance hasDecidableLt [LT α] [h : DecidableRel (α := α) (· < ·)] : (l₁ l₂ : List α) → Decidable (l₁ < l₂)
+  | [],    []    => isFalse nofun
+  | [],    _::_  => isTrue (List.lt.nil _ _)
+  | _::_, []     => isFalse nofun
   | a::as, b::bs =>
     match h a b with
-    | isTrue h₁ => isTrue (Lex.rel h₁)
+    | isTrue h₁  => isTrue (List.lt.head _ _ h₁)
     | isFalse h₁ =>
-      if h₂ : a = b then
-        match decidableLex r as bs with
-        | isTrue h₃ => isTrue (h₂ ▸ Lex.cons h₃)
+      match h b a with
+      | isTrue h₂  => isFalse (fun h => match h with
+         | List.lt.head _ _ h₁' => absurd h₁' h₁
+         | List.lt.tail _ h₂' _ => absurd h₂ h₂')
+      | isFalse h₂ =>
+        match hasDecidableLt as bs with
+        | isTrue h₃  => isTrue (List.lt.tail h₁ h₂ h₃)
         | isFalse h₃ => isFalse (fun h => match h with
-          | Lex.rel h₁' => absurd h₁' h₁
-          | Lex.cons h₃' => absurd h₃' h₃)
-      else
-        isFalse (fun h => match h with
-          | Lex.rel h₁' => absurd h₁' h₁
-          | Lex.cons h₂' => h₂ rfl)
-
-@[inherit_doc Lex]
-protected abbrev lt [LT α] : List α → List α → Prop := Lex (· < ·)
-
-instance instLT [LT α] : LT (List α) := ⟨List.lt⟩
-
-/-- Decidability of lexicographic ordering. -/
-instance decidableLT [DecidableEq α] [LT α] [DecidableLT α] (l₁ l₂ : List α) :
-    Decidable (l₁ < l₂) := decidableLex (· < ·) l₁ l₂
-
-@[deprecated decidableLT (since := "2024-12-13"), inherit_doc decidableLT]
-abbrev hasDecidableLt := @decidableLT
+           | List.lt.head _ _ h₁' => absurd h₁' h₁
+           | List.lt.tail _ _ h₃' => absurd h₃' h₃)
 
 /-- The lexicographic order on lists. -/
 @[reducible] protected def le [LT α] (a b : List α) : Prop := ¬ b < a
 
-instance instLE [LT α] : LE (List α) := ⟨List.le⟩
+instance [LT α] : LE (List α) := ⟨List.le⟩
 
-instance decidableLE [DecidableEq α] [LT α] [DecidableLT α] (l₁ l₂ : List α) :
-    Decidable (l₁ ≤ l₂) :=
-  inferInstanceAs (Decidable (Not _))
-
-/--
-Lexicographic comparator for lists.
-
-* `lex lt [] (b :: bs)` is true.
-* `lex lt as []` is false.
-* `lex lt (a :: as) (b :: bs)` is true if `lt a b` or `a == b` and `lex lt as bs` is true.
--/
-def lex [BEq α] (l₁ l₂ : List α) (lt : α → α → Bool := by exact (· < ·)) : Bool :=
-  match l₁, l₂ with
-  | [],      _ :: _  => true
-  | _,      []       => false
-  | a :: as, b :: bs => lt a b || (a == b && lex as bs lt)
-
-@[simp] theorem lex_nil_nil [BEq α] : lex ([] : List α) [] lt = false := rfl
-@[simp] theorem lex_nil_cons [BEq α] {b} {bs : List α} : lex [] (b :: bs) lt = true := rfl
-@[simp] theorem lex_cons_nil [BEq α] {a} {as : List α} : lex (a :: as) [] lt = false := rfl
-@[simp] theorem lex_cons_cons [BEq α] {a b} {as bs : List α} :
-    lex (a :: as) (b :: bs) lt = (lt a b || (a == b && lex as bs lt)) := rfl
+instance [LT α] [DecidableRel ((· < ·) : α → α → Prop)] : (l₁ l₂ : List α) → Decidable (l₁ ≤ l₂) :=
+  fun _ _ => inferInstanceAs (Decidable (Not _))
 
 /-! ## Alternative getters -/
 

src/Init/Data/List/BasicAux.lean

@@ -233,34 +233,25 @@ theorem sizeOf_get [SizeOf α] (as : List α) (i : Fin as.length) : sizeOf (as.g
     apply Nat.lt_trans ih
     simp_arith
 
-theorem not_lex_antisymm [DecidableEq α] {r : α → α → Prop} [DecidableRel r]
-    (antisymm : ∀ x y : α, ¬ r x y → ¬ r y x → x = y)
-    {as bs : List α} (h₁ : ¬ Lex r bs as) (h₂ : ¬ Lex r as bs) : as = bs :=
+theorem le_antisymm [LT α] [s : Std.Antisymm (¬ · < · : α → α → Prop)]
+    {as bs : List α} (h₁ : as ≤ bs) (h₂ : bs ≤ as) : as = bs :=
   match as, bs with
   | [],    []    => rfl
-  | [],    _::_ => False.elim <| h₂ (List.Lex.nil ..)
-  | _::_, []    => False.elim <| h₁ (List.Lex.nil ..)
+  | [],    _::_ => False.elim <| h₂ (List.lt.nil ..)
+  | _::_, []    => False.elim <| h₁ (List.lt.nil ..)
   | a::as, b::bs => by
-    by_cases hab : r a b
-    · exact False.elim <| h₂ (List.Lex.rel hab)
-    · by_cases eq : a = b
-      · subst eq
-        have h₁ : ¬ Lex r bs as := fun h => h₁ (List.Lex.cons h)
-        have h₂ : ¬ Lex r as bs := fun h => h₂ (List.Lex.cons h)
-        simp [not_lex_antisymm antisymm h₁ h₂]
-      · exfalso
-        by_cases hba : r b a
-        · exact h₁ (Lex.rel hba)
-        · exact eq (antisymm _ _ hab hba)
+    by_cases hab : a < b
+    · exact False.elim <| h₂ (List.lt.head _ _ hab)
+    · by_cases hba : b < a
+      · exact False.elim <| h₁ (List.lt.head _ _ hba)
+      · have h₁ : as ≤ bs := fun h => h₁ (List.lt.tail hba hab h)
+        have h₂ : bs ≤ as := fun h => h₂ (List.lt.tail hab hba h)
+        have ih : as = bs := le_antisymm h₁ h₂
+        have : a = b := s.antisymm hab hba
+        simp [this, ih]
 
-protected theorem le_antisymm [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Antisymm (¬ · < · : α → α → Prop)]
-    {as bs : List α} (h₁ : as ≤ bs) (h₂ : bs ≤ as) : as = bs :=
-  not_lex_antisymm i.antisymm h₁ h₂
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [s : Std.Antisymm (¬ · < · : α → α → Prop)] :
+instance [LT α] [Std.Antisymm (¬ · < · : α → α → Prop)] :
     Std.Antisymm (· ≤ · : List α → List α → Prop) where
-  antisymm _ _ h₁ h₂ := List.le_antisymm h₁ h₂
+  antisymm h₁ h₂ := le_antisymm h₁ h₂
 
 end List

src/Init/Data/List/Find.lean

@@ -566,6 +566,7 @@ theorem not_of_lt_findIdx {p : α → Bool} {xs : List α} {i : Nat} (h : i < xs
     | inl e => simpa [e, Fin.zero_eta, get_cons_zero]
     | inr e =>
       have ipm := Nat.succ_pred_eq_of_pos e
+      have ilt := Nat.le_trans ho (findIdx_le_length p)
       simp +singlePass only [← ipm, getElem_cons_succ]
       rw [← ipm, Nat.succ_lt_succ_iff] at h
       simpa using ih h

src/Init/Data/List/Impl.lean

@@ -332,7 +332,7 @@ def enumFromTR (n : Nat) (l : List α) : List (Nat × α) :=
       rw [← show _ + as.length = n + (a::as).length from Nat.succ_add .., foldr, go as]
       simp [enumFrom, f]
   rw [← Array.foldr_toList]
-  simp +zetaDelta [go]
+  simp [go]
 
 /-! ## Other list operations -/
 

src/Init/Data/List/Lemmas.lean

@@ -154,9 +154,6 @@ theorem ne_nil_iff_exists_cons {l : List α} : l ≠ [] ↔ ∃ b L, l = b :: L
 theorem singleton_inj {α : Type _} {a b : α} : [a] = [b] ↔ a = b := by
   simp
 
-@[simp] theorem concat_ne_nil (a : α) (l : List α) : l ++ [a] ≠ [] := by
-  cases l <;> simp
-
 /-! ## L[i] and L[i]? -/
 
 /-! ### `get` and `get?`.
@@ -194,52 +191,50 @@ We simplify away `getD`, replacing `getD l n a` with `(l[n]?).getD a`.
 Because of this, there is only minimal API for `getD`.
 -/
 
-@[simp] theorem getD_eq_getElem?_getD (l) (i) (a : α) : getD l i a = (l[i]?).getD a := by
+@[simp] theorem getD_eq_getElem?_getD (l) (n) (a : α) : getD l n a = (l[n]?).getD a := by
   simp [getD]
 
 /-! ### get!
 
-We simplify `l.get! i` to `l[i]!`.
+We simplify `l.get! n` to `l[n]!`.
 -/
 
-theorem get!_eq_getD [Inhabited α] : ∀ (l : List α) i, l.get! i = l.getD i default
+theorem get!_eq_getD [Inhabited α] : ∀ (l : List α) n, l.get! n = l.getD n default
   | [], _      => rfl
   | _a::_, 0   => rfl
   | _a::l, n+1 => get!_eq_getD l n
 
-@[simp] theorem get!_eq_getElem! [Inhabited α] (l : List α) (i) : l.get! i = l[i]! := by
+@[simp] theorem get!_eq_getElem! [Inhabited α] (l : List α) (n) : l.get! n = l[n]! := by
   simp [get!_eq_getD]
   rfl
 
 /-! ### getElem!
 
-We simplify `l[i]!` to `(l[i]?).getD default`.
+We simplify `l[n]!` to `(l[n]?).getD default`.
 -/
 
-@[simp] theorem getElem!_eq_getElem?_getD [Inhabited α] (l : List α) (i : Nat) :
-    l[i]! = (l[i]?).getD (default : α) := by
+@[simp] theorem getElem!_eq_getElem?_getD [Inhabited α] (l : List α) (n : Nat) :
+    l[n]! = (l[n]?).getD (default : α) := by
   simp only [getElem!_def]
-  match l[i]? with
-  | some _ => simp
-  | none => simp
+  split <;> simp_all
 
 /-! ### getElem? and getElem -/
 
-@[simp] theorem getElem?_eq_none_iff : l[i]? = none ↔ length l ≤ i := by
+@[simp] theorem getElem?_eq_none_iff : l[n]? = none ↔ length l ≤ n := by
   simp only [← get?_eq_getElem?, get?_eq_none_iff]
 
-@[simp] theorem none_eq_getElem?_iff {l : List α} {i : Nat} : none = l[i]? ↔ length l ≤ i := by
+@[simp] theorem none_eq_getElem?_iff {l : List α} {n : Nat} : none = l[n]? ↔ length l ≤ n := by
   simp [eq_comm (a := none)]
 
-theorem getElem?_eq_none (h : length l ≤ i) : l[i]? = none := getElem?_eq_none_iff.mpr h
+theorem getElem?_eq_none (h : length l ≤ n) : l[n]? = none := getElem?_eq_none_iff.mpr h
 
-@[simp] theorem getElem?_eq_getElem {l : List α} {i} (h : i < l.length) : l[i]? = some l[i] :=
+@[simp] theorem getElem?_eq_getElem {l : List α} {n} (h : n < l.length) : l[n]? = some l[n] :=
   getElem?_pos ..
 
-theorem getElem?_eq_some_iff {l : List α} : l[i]? = some a ↔ ∃ h : i < l.length, l[i] = a := by
+theorem getElem?_eq_some_iff {l : List α} : l[n]? = some a ↔ ∃ h : n < l.length, l[n] = a := by
   simp only [← get?_eq_getElem?, get?_eq_some_iff, get_eq_getElem]
 
-theorem some_eq_getElem?_iff {l : List α} : some a = l[i]? ↔ ∃ h : i < l.length, l[i] = a := by
+theorem some_eq_getElem?_iff {l : List α} : some a = l[n]? ↔ ∃ h : n < l.length, l[n] = a := by
   rw [eq_comm, getElem?_eq_some_iff]
 
 @[simp] theorem some_getElem_eq_getElem?_iff (xs : List α) (i : Nat) (h : i < xs.length) :
@@ -250,7 +245,7 @@ theorem some_eq_getElem?_iff {l : List α} : some a = l[i]? ↔ ∃ h : i < l.le
     (xs[i]? = some xs[i]) ↔ True := by
   simp [h]
 
-theorem getElem_eq_iff {l : List α} {i : Nat} {h : i < l.length} : l[i] = x ↔ l[i]? = some x := by
+theorem getElem_eq_iff {l : List α} {n : Nat} {h : n < l.length} : l[n] = x ↔ l[n]? = some x := by
   simp only [getElem?_eq_some_iff]
   exact ⟨fun w => ⟨h, w⟩, fun h => h.2⟩
 
@@ -266,7 +261,7 @@ theorem getD_getElem? (l : List α) (i : Nat) (d : α) :
     have p : i ≥ l.length := Nat.le_of_not_gt h
     simp [getElem?_eq_none p, h]
 
-@[simp] theorem getElem?_nil {i : Nat} : ([] : List α)[i]? = none := rfl
+@[simp] theorem getElem?_nil {n : Nat} : ([] : List α)[n]? = none := rfl
 
 theorem getElem_cons {l : List α} (w : i < (a :: l).length) :
     (a :: l)[i] =
@@ -275,7 +270,7 @@ theorem getElem_cons {l : List α} (w : i < (a :: l).length) :
 
 theorem getElem?_cons_zero {l : List α} : (a::l)[0]? = some a := by simp
 
-@[simp] theorem getElem?_cons_succ {l : List α} : (a::l)[i+1]? = l[i]? := by
+@[simp] theorem getElem?_cons_succ {l : List α} : (a::l)[n+1]? = l[n]? := by
   simp only [← get?_eq_getElem?]
   rfl
 
@@ -302,11 +297,11 @@ theorem getElem_zero {l : List α} (h : 0 < l.length) : l[0] = l.head (length_po
   match l, h with
   | _ :: _, _ => rfl
 
-@[ext] theorem ext_getElem? {l₁ l₂ : List α} (h : ∀ i : Nat, l₁[i]? = l₂[i]?) : l₁ = l₂ :=
+@[ext] theorem ext_getElem? {l₁ l₂ : List α} (h : ∀ n : Nat, l₁[n]? = l₂[n]?) : l₁ = l₂ :=
   ext_get? fun n => by simp_all
 
 theorem ext_getElem {l₁ l₂ : List α} (hl : length l₁ = length l₂)
-    (h : ∀ (i : Nat) (h₁ : i < l₁.length) (h₂ : i < l₂.length), l₁[i]'h₁ = l₂[i]'h₂) : l₁ = l₂ :=
+    (h : ∀ (n : Nat) (h₁ : n < l₁.length) (h₂ : n < l₂.length), l₁[n]'h₁ = l₂[n]'h₂) : l₁ = l₂ :=
   ext_getElem? fun n =>
     if h₁ : n < length l₁ then by
       simp_all [getElem?_eq_getElem]
@@ -427,25 +422,25 @@ theorem not_mem_cons_of_ne_of_not_mem {a y : α} {l : List α} : a ≠ y → a
 theorem ne_and_not_mem_of_not_mem_cons {a y : α} {l : List α} : a ∉ y :: l → a ≠ y ∧ a ∉ l :=
   fun p => ⟨ne_of_not_mem_cons p, not_mem_of_not_mem_cons p⟩
 
-theorem getElem_of_mem : ∀ {a} {l : List α}, a ∈ l → ∃ (i : Nat) (h : i < l.length), l[i]'h = a
+theorem getElem_of_mem : ∀ {a} {l : List α}, a ∈ l → ∃ (n : Nat) (h : n < l.length), l[n]'h = a
   | _, _ :: _, .head .. => ⟨0, Nat.succ_pos _, rfl⟩
-  | _, _ :: _, .tail _ m => let ⟨i, h, e⟩ := getElem_of_mem m; ⟨i+1, Nat.succ_lt_succ h, e⟩
+  | _, _ :: _, .tail _ m => let ⟨n, h, e⟩ := getElem_of_mem m; ⟨n+1, Nat.succ_lt_succ h, e⟩
 
-theorem getElem?_of_mem {a} {l : List α} (h : a ∈ l) : ∃ i : Nat, l[i]? = some a := by
+theorem getElem?_of_mem {a} {l : List α} (h : a ∈ l) : ∃ n : Nat, l[n]? = some a := by
   let ⟨n, _, e⟩ := getElem_of_mem h
   exact ⟨n, e ▸ getElem?_eq_getElem _⟩
 
-theorem mem_of_getElem? {l : List α} {i : Nat} {a : α} (e : l[i]? = some a) : a ∈ l :=
+theorem mem_of_getElem? {l : List α} {n : Nat} {a : α} (e : l[n]? = some a) : a ∈ l :=
   let ⟨_, e⟩ := getElem?_eq_some_iff.1 e; e ▸ getElem_mem ..
 
-theorem mem_iff_getElem {a} {l : List α} : a ∈ l ↔ ∃ (i : Nat) (h : i < l.length), l[i]'h = a :=
+theorem mem_iff_getElem {a} {l : List α} : a ∈ l ↔ ∃ (n : Nat) (h : n < l.length), l[n]'h = a :=
   ⟨getElem_of_mem, fun ⟨_, _, e⟩ => e ▸ getElem_mem ..⟩
 
-theorem mem_iff_getElem? {a} {l : List α} : a ∈ l ↔ ∃ i : Nat, l[i]? = some a := by
+theorem mem_iff_getElem? {a} {l : List α} : a ∈ l ↔ ∃ n : Nat, l[n]? = some a := by
   simp [getElem?_eq_some_iff, mem_iff_getElem]
 
 theorem forall_getElem {l : List α} {p : α → Prop} :
-    (∀ (i : Nat) h, p (l[i]'h)) ↔ ∀ a, a ∈ l → p a := by
+    (∀ (n : Nat) h, p (l[n]'h)) ↔ ∀ a, a ∈ l → p a := by
   induction l with
   | nil => simp
   | cons a l ih =>
@@ -598,10 +593,10 @@ theorem getElem?_set_self' {l : List α} {i : Nat} {a : α} :
     simp_all
   · rw [getElem?_eq_none (by simp_all), getElem?_eq_none (by simp_all)]
 
-theorem getElem_set {l : List α} {i j} {a} (h) :
-    (set l i a)[j]'h = if i = j then a else l[j]'(length_set .. ▸ h) := by
-  if h : i = j then
-    subst h; simp only [getElem_set_self, ↓reduceIte]
+theorem getElem_set {l : List α} {m n} {a} (h) :
+    (set l m a)[n]'h = if m = n then a else l[n]'(length_set .. ▸ h) := by
+  if h : m = n then
+    subst m; simp only [getElem_set_self, ↓reduceIte]
   else
     simp [h]
 
@@ -674,42 +669,6 @@ theorem mem_or_eq_of_mem_set : ∀ {l : List α} {n : Nat} {a b : α}, a ∈ l.s
 
 /-! ### BEq -/
 
-@[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
-
-@[simp] theorem concat_beq_concat [BEq α] {a b : α} {l₁ l₂ : List α} :
-    (l₁ ++ [a] == l₂ ++ [b]) = (l₁ == l₂ && a == b) := by
-  induction l₁ generalizing l₂ with
-  | nil => cases l₂ <;> simp
-  | cons x l₁ ih =>
-    cases l₂ with
-    | nil => simp
-    | cons y l₂ => simp [ih, Bool.and_assoc]
-
-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
-
-@[simp] theorem replicate_beq_replicate [BEq α] {a b : α} {n : Nat} :
-    (replicate n a == replicate n b) = (n == 0 || a == b) := by
-  cases n with
-  | zero => simp
-  | succ n =>
-    rw [replicate_succ, replicate_succ, cons_beq_cons, replicate_beq_replicate]
-    rw [Bool.eq_iff_iff]
-    simp +contextual
-
 @[simp] theorem reflBEq_iff [BEq α] : ReflBEq (List α) ↔ ReflBEq α := by
   constructor
   · intro h
@@ -747,15 +706,66 @@ theorem length_eq_of_beq [BEq α] {l₁ l₂ : List α} (h : l₁ == l₂) : l
     · intro a
       simp
 
-/-! ### isEqv -/
+@[simp] theorem beq_nil_iff [BEq α] {l : List α} : (l == []) = l.isEmpty := by
+  cases l <;> rfl
 
-@[simp] theorem isEqv_eq [DecidableEq α] {l₁ l₂ : List α} : l₁.isEqv l₂ (· == ·) = (l₁ = l₂) := by
+@[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
+  induction l with
+  | nil => nofun
+  | cons a l ih => intro
+    | .head _ _ h => exact lt_irrefl _ h
+    | .tail _ _ h => exact ih h
+
+protected theorem lt_trans [LT α] [DecidableRel (@LT.lt α _)]
+    (lt_trans : ∀ {x y z : α}, x < y → y < z → x < z)
+    (le_trans : ∀ {x y z : α}, ¬x < y → ¬y < z → ¬x < z)
+    {l₁ l₂ l₃ : List α} (h₁ : l₁ < l₂) (h₂ : l₂ < l₃) : l₁ < l₃ := by
+  induction h₁ generalizing l₃ with
+  | nil => let _::_ := l₃; exact List.lt.nil ..
+  | @head a l₁ b l₂ ab =>
+    match h₂ with
+    | .head l₂ l₃ bc => exact List.lt.head _ _ (lt_trans ab bc)
+    | .tail _ cb ih =>
+      exact List.lt.head _ _ <| Decidable.by_contra (le_trans · cb ab)
+  | @tail a l₁ b l₂ ab ba h₁ ih2 =>
+    match h₂ with
+    | .head l₂ l₃ bc =>
+      exact List.lt.head _ _ <| Decidable.by_contra (le_trans ba · bc)
+    | .tail bc cb ih =>
+      exact List.lt.tail (le_trans ab bc) (le_trans cb ba) (ih2 ih)
+
+protected theorem lt_antisymm [LT α]
+    (lt_antisymm : ∀ {x y : α}, ¬x < y → ¬y < x → x = y)
+    {l₁ l₂ : List α} (h₁ : ¬l₁ < l₂) (h₂ : ¬l₂ < l₁) : l₁ = l₂ := by
   induction l₁ generalizing l₂ with
-  | nil => cases l₂ <;> simp
+  | nil =>
+    cases l₂ with
+    | nil => rfl
+    | cons b l₂ => cases h₁ (.nil ..)
   | cons a l₁ ih =>
     cases l₂ with
-    | nil => simp
-    | cons b l₂ => simp [isEqv, ih]
+    | nil => cases h₂ (.nil ..)
+    | cons b l₂ =>
+      have ab : ¬a < b := fun ab => h₁ (.head _ _ ab)
+      cases lt_antisymm ab (fun ba => h₂ (.head _ _ ba))
+      rw [ih (fun ll => h₁ (.tail ab ab ll)) (fun ll => h₂ (.tail ab ab ll))]
 
 /-! ### foldlM and foldrM -/
 
@@ -1009,8 +1019,8 @@ theorem getLastD_mem_cons : ∀ (l : List α) (a : α), getLastD l a ∈ a::l
   | [], _ => .head ..
   | _::_, _ => .tail _ <| getLast_mem _
 
-theorem getElem_cons_length (x : α) (xs : List α) (i : Nat) (h : i = xs.length) :
-    (x :: xs)[i]'(by simp [h]) = (x :: xs).getLast (cons_ne_nil x xs) := by
+theorem getElem_cons_length (x : α) (xs : List α) (n : Nat) (h : n = xs.length) :
+    (x :: xs)[n]'(by simp [h]) = (x :: xs).getLast (cons_ne_nil x xs) := by
   rw [getLast_eq_getElem]; cases h; rfl
 
 @[deprecated getElem_cons_length (since := "2024-06-12")]
@@ -1242,24 +1252,24 @@ theorem map_singleton (f : α → β) (a : α) : map f [a] = [f a] := rfl
   | nil => simp [List.map]
   | cons _ as ih => simp [List.map, ih]
 
-@[simp] theorem getElem?_map (f : α → β) : ∀ (l : List α) (i : Nat), (map f l)[i]? = Option.map f l[i]?
+@[simp] theorem getElem?_map (f : α → β) : ∀ (l : List α) (n : Nat), (map f l)[n]? = Option.map f l[n]?
   | [], _ => rfl
   | _ :: _, 0 => by simp
-  | _ :: l, i+1 => by simp [getElem?_map f l i]
+  | _ :: l, n+1 => by simp [getElem?_map f l n]
 
 @[deprecated getElem?_map (since := "2024-06-12")]
-theorem get?_map (f : α → β) : ∀ l i, (map f l).get? i = (l.get? i).map f
+theorem get?_map (f : α → β) : ∀ l n, (map f l).get? n = (l.get? n).map f
   | [], _ => rfl
   | _ :: _, 0 => rfl
-  | _ :: l, i+1 => get?_map f l i
+  | _ :: l, n+1 => get?_map f l n
 
-@[simp] theorem getElem_map (f : α → β) {l} {i : Nat} {h : i < (map f l).length} :
-    (map f l)[i] = f (l[i]'(length_map l f ▸ h)) :=
+@[simp] theorem getElem_map (f : α → β) {l} {n : Nat} {h : n < (map f l).length} :
+    (map f l)[n] = f (l[n]'(length_map l f ▸ h)) :=
   Option.some.inj <| by rw [← getElem?_eq_getElem, getElem?_map, getElem?_eq_getElem]; rfl
 
 @[deprecated getElem_map (since := "2024-06-12")]
-theorem get_map (f : α → β) {l i} :
-    get (map f l) i = f (get l ⟨i, length_map l f ▸ i.2⟩) := by
+theorem get_map (f : α → β) {l n} :
+    get (map f l) n = f (get l ⟨n, length_map l f ▸ n.2⟩) := by
   simp
 
 @[simp] theorem mem_map {f : α → β} : ∀ {l : List α}, b ∈ l.map f ↔ ∃ a, a ∈ l ∧ f a = b
@@ -1690,71 +1700,71 @@ theorem filterMap_eq_cons_iff {l} {b} {bs} :
 @[simp] theorem cons_append_fun (a : α) (as : List α) :
     (fun bs => ((a :: as) ++ bs)) = fun bs => a :: (as ++ bs) := rfl
 
-theorem getElem_append {l₁ l₂ : List α} (i : Nat) (h : i < (l₁ ++ l₂).length) :
-    (l₁ ++ l₂)[i] = if h' : i < l₁.length then l₁[i] else l₂[i - l₁.length]'(by simp at h h'; exact Nat.sub_lt_left_of_lt_add h' h) := by
+theorem getElem_append {l₁ l₂ : List α} (n : Nat) (h : n < (l₁ ++ l₂).length) :
+    (l₁ ++ l₂)[n] = if h' : n < l₁.length then l₁[n] else l₂[n - l₁.length]'(by simp at h h'; exact Nat.sub_lt_left_of_lt_add h' h) := by
   split <;> rename_i h'
   · rw [getElem_append_left h']
   · rw [getElem_append_right (by simpa using h')]
 
-theorem getElem?_append_left {l₁ l₂ : List α} {i : Nat} (hn : i < l₁.length) :
-    (l₁ ++ l₂)[i]? = l₁[i]? := by
-  have hn' : i < (l₁ ++ l₂).length := Nat.lt_of_lt_of_le hn <|
+theorem getElem?_append_left {l₁ l₂ : List α} {n : Nat} (hn : n < l₁.length) :
+    (l₁ ++ l₂)[n]? = l₁[n]? := by
+  have hn' : n < (l₁ ++ l₂).length := Nat.lt_of_lt_of_le hn <|
     length_append .. ▸ Nat.le_add_right ..
   simp_all [getElem?_eq_getElem, getElem_append]
 
-theorem getElem?_append_right : ∀ {l₁ l₂ : List α} {i : Nat}, l₁.length ≤ i →
-  (l₁ ++ l₂)[i]? = l₂[i - l₁.length]?
+theorem getElem?_append_right : ∀ {l₁ l₂ : List α} {n : Nat}, l₁.length ≤ n →
+  (l₁ ++ l₂)[n]? = l₂[n - l₁.length]?
 | [], _, _, _ => rfl
-| a :: l, _, i+1, h₁ => by
+| a :: l, _, n+1, h₁ => by
   rw [cons_append]
   simp [Nat.succ_sub_succ_eq_sub, getElem?_append_right (Nat.lt_succ.1 h₁)]
 
-theorem getElem?_append {l₁ l₂ : List α} {i : Nat} :
-    (l₁ ++ l₂)[i]? = if i < l₁.length then l₁[i]? else l₂[i - l₁.length]? := by
+theorem getElem?_append {l₁ l₂ : List α} {n : Nat} :
+    (l₁ ++ l₂)[n]? = if n < l₁.length then l₁[n]? else l₂[n - l₁.length]? := by
   split <;> rename_i h
   · exact getElem?_append_left h
   · exact getElem?_append_right (by simpa using h)
 
 @[deprecated getElem?_append_right (since := "2024-06-12")]
-theorem get?_append_right {l₁ l₂ : List α} {i : Nat} (h : l₁.length ≤ i) :
-    (l₁ ++ l₂).get? i = l₂.get? (i - l₁.length) := by
+theorem get?_append_right {l₁ l₂ : List α} {n : Nat} (h : l₁.length ≤ n) :
+    (l₁ ++ l₂).get? n = l₂.get? (n - l₁.length) := by
   simp [getElem?_append_right, h]
 
 /-- Variant of `getElem_append_left` useful for rewriting from the small list to the big list. -/
-theorem getElem_append_left' (l₂ : List α) {l₁ : List α} {i : Nat} (hi : i < l₁.length) :
-    l₁[i] = (l₁ ++ l₂)[i]'(by simpa using Nat.lt_add_right l₂.length hi) := by
+theorem getElem_append_left' (l₂ : List α) {l₁ : List α} {n : Nat} (hn : n < l₁.length) :
+    l₁[n] = (l₁ ++ l₂)[n]'(by simpa using Nat.lt_add_right l₂.length hn) := by
   rw [getElem_append_left] <;> simp
 
 /-- Variant of `getElem_append_right` useful for rewriting from the small list to the big list. -/
-theorem getElem_append_right' (l₁ : List α) {l₂ : List α} {i : Nat} (hi : i < l₂.length) :
-    l₂[i] = (l₁ ++ l₂)[i + l₁.length]'(by simpa [Nat.add_comm] using Nat.add_lt_add_left hi _) := by
+theorem getElem_append_right' (l₁ : List α) {l₂ : List α} {n : Nat} (hn : n < l₂.length) :
+    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")]
-theorem get_append_right_aux {l₁ l₂ : List α} {i : Nat}
-  (h₁ : l₁.length ≤ i) (h₂ : i < (l₁ ++ l₂).length) : i - l₁.length < l₂.length := by
+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
   exact Nat.sub_lt_left_of_lt_add h₁ h₂
 
 set_option linter.deprecated false in
 @[deprecated getElem_append_right (since := "2024-06-12")]
-theorem get_append_right' {l₁ l₂ : List α} {i : Nat} (h₁ : l₁.length ≤ i) (h₂) :
-    (l₁ ++ l₂).get ⟨i, h₂⟩ = l₂.get ⟨i - l₁.length, get_append_right_aux h₁ h₂⟩ :=
+theorem get_append_right' {l₁ l₂ : List α} {n : Nat} (h₁ : l₁.length ≤ n) (h₂) :
+    (l₁ ++ l₂).get ⟨n, h₂⟩ = l₂.get ⟨n - l₁.length, get_append_right_aux h₁ h₂⟩ :=
   Option.some.inj <| by rw [← get?_eq_get, ← get?_eq_get, get?_append_right h₁]
 
-theorem getElem_of_append {l : List α} (eq : l = l₁ ++ a :: l₂) (h : l₁.length = i) :
-    l[i]'(eq ▸ h ▸ by simp_arith) = a := Option.some.inj <| by
+theorem getElem_of_append {l : List α} (eq : l = l₁ ++ a :: l₂) (h : l₁.length = n) :
+    l[n]'(eq ▸ h ▸ by simp_arith) = a := Option.some.inj <| by
   rw [← getElem?_eq_getElem, eq, getElem?_append_right (h ▸ Nat.le_refl _), h]
   simp
 
 @[deprecated "Deprecated without replacement." (since := "2024-06-12")]
 theorem get_of_append_proof {l : List α}
-    (eq : l = l₁ ++ a :: l₂) (h : l₁.length = i) : i < length l := eq ▸ h ▸ by simp_arith
+    (eq : l = l₁ ++ a :: l₂) (h : l₁.length = n) : n < length l := eq ▸ h ▸ by simp_arith
 
 set_option linter.deprecated false in
 @[deprecated getElem_of_append (since := "2024-06-12")]
-theorem get_of_append {l : List α} (eq : l = l₁ ++ a :: l₂) (h : l₁.length = i) :
-    l.get ⟨i, get_of_append_proof eq h⟩ = a := Option.some.inj <| by
+theorem get_of_append {l : List α} (eq : l = l₁ ++ a :: l₂) (h : l₁.length = n) :
+    l.get ⟨n, get_of_append_proof eq h⟩ = a := Option.some.inj <| by
   rw [← get?_eq_get, eq, get?_append_right (h ▸ Nat.le_refl _), h, Nat.sub_self]; rfl
 
 /--
@@ -2062,6 +2072,8 @@ theorem concat_inj_right {l : List α} {a a' : α} : concat l a = concat l a'
 
 @[deprecated concat_inj (since := "2024-09-05")] abbrev concat_eq_concat := @concat_inj
 
+theorem concat_ne_nil (a : α) (l : List α) : concat l a ≠ [] := by cases l <;> simp
+
 theorem concat_append (a : α) (l₁ l₂ : List α) : concat l₁ a ++ l₂ = l₁ ++ a :: l₂ := by simp
 
 theorem append_concat (a : α) (l₁ l₂ : List α) : l₁ ++ concat l₂ a = concat (l₁ ++ l₂) a := by simp
@@ -2314,10 +2326,6 @@ theorem flatMap_eq_foldl (f : α → List β) (l : List α) :
 
 @[simp] theorem replicate_one : replicate 1 a = [a] := rfl
 
-/-- Variant of `replicate_succ` that concatenates `a` to the end of the list. -/
-theorem replicate_succ' : replicate (n + 1) a = replicate n a ++ [a] := by
-  induction n <;> simp_all [replicate_succ, ← cons_append]
-
 @[simp] theorem mem_replicate {a b : α} : ∀ {n}, b ∈ replicate n a ↔ n ≠ 0 ∧ b = a
   | 0 => by simp
   | n+1 => by simp [replicate_succ, mem_replicate, Nat.succ_ne_zero]
@@ -3396,12 +3404,12 @@ theorem getElem!_nil [Inhabited α] {n : Nat} : ([] : List α)[n]! = default :=
 theorem getElem!_cons_zero [Inhabited α] {l : List α} : (a::l)[0]! = a := by
   rw [getElem!_pos] <;> simp
 
-theorem getElem!_cons_succ [Inhabited α] {l : List α} : (a::l)[i+1]! = l[i]! := by
-  by_cases h : i < l.length
+theorem getElem!_cons_succ [Inhabited α] {l : List α} : (a::l)[n+1]! = l[n]! := by
+  by_cases h : n < l.length
   · rw [getElem!_pos, getElem!_pos] <;> simp_all [Nat.succ_lt_succ_iff]
   · rw [getElem!_neg, getElem!_neg] <;> simp_all [Nat.succ_lt_succ_iff]
 
-theorem getElem!_of_getElem? [Inhabited α] : ∀ {l : List α} {i : Nat}, l[i]? = some a → l[i]! = a
+theorem getElem!_of_getElem? [Inhabited α] : ∀ {l : List α} {n : Nat}, l[n]? = some a → l[n]! = a
   | _a::_, 0, _ => by
     rw [getElem!_pos] <;> simp_all
   | _::l, _+1, e => by
@@ -3550,7 +3558,7 @@ theorem isSome_getElem? {l : List α} {n : Nat} : l[n]?.isSome ↔ n < l.length
   simp
 
 @[deprecated _root_.isNone_getElem? (since := "2024-12-09")]
-theorem isNone_getElem? {l : List α} {i : Nat} : l[i]?.isNone ↔ l.length ≤ i := by
+theorem isNone_getElem? {l : List α} {n : Nat} : l[n]?.isNone ↔ l.length ≤ n := by
   simp
 
 end List

src/Init/Data/List/Lex.lean

@@ -1,430 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
--/
-prelude
-import Init.Data.List.Lemmas
-
-namespace List
-
-/-! ### Lexicographic ordering -/
-
-@[simp] theorem lex_lt [LT α] (l₁ l₂ : List α) : Lex (· < ·) l₁ l₂ ↔ l₁ < l₂ := Iff.rfl
-@[simp] theorem not_lex_lt [LT α] (l₁ l₂ : List α) : ¬ Lex (· < ·) l₁ l₂ ↔ l₂ ≤ l₁ := Iff.rfl
-
-theorem not_lt_iff_ge [LT α] (l₁ l₂ : List α) : ¬ l₁ < l₂ ↔ l₂ ≤ l₁ := Iff.rfl
-theorem not_le_iff_gt [DecidableEq α] [LT α] [DecidableLT α] (l₁ l₂ : List α) :
-    ¬ l₁ ≤ l₂ ↔ l₂ < l₁ :=
-  Decidable.not_not
-
-theorem lex_irrefl {r : α → α → Prop} (irrefl : ∀ x, ¬r x x) (l : List α) : ¬Lex r l l := by
-  induction l with
-  | nil => nofun
-  | cons a l ih => intro
-    | .rel h => exact irrefl _ h
-    | .cons h => exact ih h
-
-protected theorem lt_irrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] (l : List α) : ¬ l < l :=
-  lex_irrefl Std.Irrefl.irrefl l
-
-instance ltIrrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Irrefl (α := List α) (· < ·) where
-  irrefl := List.lt_irrefl
-
-@[simp] theorem not_lex_nil : ¬Lex r l [] := fun h => nomatch h
-
-@[simp] theorem nil_le [LT α] (l : List α) : [] ≤ l := fun h => nomatch h
-
-@[simp] theorem not_nil_lex_iff : ¬Lex r [] l ↔ l = [] := by
-  constructor
-  · rintro h
-    match l, h with
-    | [], h => rfl
-    | a :: _, h => exact False.elim (h Lex.nil)
-  · rintro rfl
-    exact not_lex_nil
-
-@[simp] theorem le_nil [LT α] (l : List α) : l ≤ [] ↔ l = [] := not_nil_lex_iff
-
-@[simp] theorem nil_lex_cons : Lex r [] (a :: l) := Lex.nil
-
-@[simp] theorem nil_lt_cons [LT α] (a : α) (l : List α) : [] < a :: l := Lex.nil
-
-theorem cons_lex_cons_iff : Lex r (a :: l₁) (b :: l₂) ↔ r a b ∨ a = b ∧ Lex r l₁ l₂ :=
-  ⟨fun | .rel h => .inl h | .cons h => .inr ⟨rfl, h⟩,
-    fun | .inl h => Lex.rel h | .inr ⟨rfl, h⟩ => Lex.cons h⟩
-
-theorem cons_lt_cons_iff [LT α] {a b} {l₁ l₂ : List α} :
-    (a :: l₁) < (b :: l₂) ↔ a < b ∨ a = b ∧ l₁ < l₂ := by
-  dsimp only [instLT, List.lt]
-  simp [cons_lex_cons_iff]
-
-theorem not_cons_lex_cons_iff [DecidableEq α] [DecidableRel r] {a b} {l₁ l₂ : List α} :
-    ¬ Lex r (a :: l₁) (b :: l₂) ↔ (¬ r a b ∧ a ≠ b) ∨ (¬ r a b ∧ ¬ Lex r l₁ l₂) := by
-  rw [cons_lex_cons_iff, not_or, Decidable.not_and_iff_or_not, and_or_left]
-
-theorem cons_le_cons_iff [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    {a b} {l₁ l₂ : List α} :
-    (a :: l₁) ≤ (b :: l₂) ↔ a < b ∨ a = b ∧ l₁ ≤ l₂ := by
-  dsimp only [instLE, instLT, List.le, List.lt]
-  simp only [not_cons_lex_cons_iff, ne_eq]
-  constructor
-  · rintro (⟨h₁, h₂⟩ | ⟨h₁, h₂⟩)
-    · left
-      apply Decidable.byContradiction
-      intro h₃
-      apply h₂
-      exact i₂.antisymm _ _ h₁ h₃
-    · if h₃ : a < b then
-        exact .inl h₃
-      else
-        right
-        exact ⟨i₂.antisymm _ _ h₃ h₁, h₂⟩
-  · rintro (h | ⟨h₁, h₂⟩)
-    · left
-      exact ⟨i₁.asymm _ _ h, fun w => i₀.irrefl _ (w ▸ h)⟩
-    · right
-      exact ⟨fun w => i₀.irrefl _ (h₁ ▸ w), h₂⟩
-
-theorem not_lt_of_cons_le_cons [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    {a b : α} {l₁ l₂ : List α} (h : a :: l₁ ≤ b :: l₂) : ¬ b < a := by
-  rw [cons_le_cons_iff] at h
-  rcases h with h | ⟨rfl, h⟩
-  · exact i₁.asymm _ _ h
-  · exact i₀.irrefl _
-
-theorem le_of_cons_le_cons [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    {a} {l₁ l₂ : List α} (h : a :: l₁ ≤ a :: l₂) : l₁ ≤ l₂ := by
-  rw [cons_le_cons_iff] at h
-  rcases h with h | ⟨_, h⟩
-  · exact False.elim (i₀.irrefl _ h)
-  · exact h
-
-protected theorem le_refl [LT α] [i₀ : Std.Irrefl (· < · : α → α → Prop)] (l : List α) : l ≤ l := by
-  induction l with
-  | nil => simp
-  | cons a l ih =>
-    intro
-    | .rel h => exact i₀.irrefl _ h
-    | .cons h₃ => exact ih h₃
-
-instance [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Refl (· ≤ · : List α → List α → Prop) where
-  refl := List.le_refl
-
-theorem lex_trans {r : α → α → Prop} [DecidableRel r]
-    (lt_trans : ∀ {x y z : α}, r x y → r y z → r x z)
-    (h₁ : Lex r l₁ l₂) (h₂ : Lex r l₂ l₃) : Lex r l₁ l₃ := by
-  induction h₁ generalizing l₃ with
-  | nil => let _::_ := l₃; exact List.Lex.nil ..
-  | @rel a l₁ b l₂ ab =>
-    match h₂ with
-    | .rel bc => exact List.Lex.rel (lt_trans ab bc)
-    | .cons ih =>
-      exact List.Lex.rel ab
-  | @cons a l₁ l₂ h₁ ih2 =>
-    match h₂ with
-    | .rel bc =>
-      exact List.Lex.rel bc
-    | .cons ih =>
-      exact List.Lex.cons (ih2 ih)
-
-protected theorem lt_trans [LT α] [DecidableLT α]
-    [i₁ : Trans (· < · : α → α → Prop) (· < ·) (· < ·)]
-    {l₁ l₂ l₃ : List α} (h₁ : l₁ < l₂) (h₂ : l₂ < l₃) : l₁ < l₃ := by
-  simp only [instLT, List.lt] at h₁ h₂ ⊢
-  exact lex_trans (fun h₁ h₂ => i₁.trans h₁ h₂) h₁ h₂
-
-instance [LT α] [DecidableLT α]
-    [Trans (· < · : α → α → Prop) (· < ·) (· < ·)] :
-    Trans (· < · : List α → List α → Prop) (· < ·) (· < ·) where
-  trans h₁ h₂ := List.lt_trans h₁ h₂
-
-@[deprecated List.le_antisymm (since := "2024-12-13")]
-protected abbrev lt_antisymm := @List.le_antisymm
-
-protected theorem lt_of_le_of_lt [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    [i₃ : Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : List α} (h₁ : l₁ ≤ l₂) (h₂ : l₂ < l₃) : l₁ < l₃ := by
-  induction h₂ generalizing l₁ with
-  | nil => simp_all
-  | rel hab =>
-    rename_i a b
-    cases l₁ with
-    | nil => simp_all
-    | cons c l₁ =>
-      apply Lex.rel
-      replace h₁ := not_lt_of_cons_le_cons h₁
-      apply Decidable.byContradiction
-      intro h₂
-      have := i₃.trans h₁ h₂
-      contradiction
-  | cons w₃ ih =>
-    rename_i a as bs
-    cases l₁ with
-    | nil => simp_all
-    | cons c l₁ =>
-      have w₄ := not_lt_of_cons_le_cons h₁
-      by_cases w₅ : a = c
-      · subst w₅
-        exact Lex.cons (ih (le_of_cons_le_cons h₁))
-      · exact Lex.rel (Decidable.byContradiction fun w₆ => w₅ (i₂.antisymm _ _ w₄ w₆))
-
-protected theorem le_trans [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : List α} (h₁ : l₁ ≤ l₂) (h₂ : l₂ ≤ l₃) : l₁ ≤ l₃ :=
-  fun h₃ => h₁ (List.lt_of_le_of_lt h₂ h₃)
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)] :
-    Trans (· ≤ · : List α → List α → Prop) (· ≤ ·) (· ≤ ·) where
-  trans h₁ h₂ := List.le_trans h₁ h₂
-
-theorem lex_asymm {r : α → α → Prop} [DecidableRel r]
-    (h : ∀ {x y : α}, r x y → ¬ r y x) : ∀ {l₁ l₂ : List α}, Lex r l₁ l₂ → ¬ Lex r l₂ l₁
-  | nil, _, .nil => by simp
-  | x :: l₁, y :: l₂, .rel h₁ =>
-    fun
-    | .rel h₂ => h h₁ h₂
-    | .cons h₂ => h h₁ h₁
-  | x :: l₁, _ :: l₂, .cons h₁ =>
-    fun
-    | .rel h₂ => h h₂ h₂
-    | .cons h₂ => lex_asymm h h₁ h₂
-
-protected theorem lt_asymm [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Asymm (· < · : α → α → Prop)]
-    {l₁ l₂ : List α} (h : l₁ < l₂) : ¬ l₂ < l₁ := lex_asymm (i.asymm _ _) h
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Asymm (· < · : α → α → Prop)] :
-    Std.Asymm (· < · : List α → List α → Prop) where
-  asymm _ _ := List.lt_asymm
-
-theorem not_lex_total [DecidableEq α] {r : α → α → Prop} [DecidableRel r]
-    (h : ∀ x y : α, ¬ r x y ∨ ¬ r y x) (l₁ l₂ : List α) : ¬ Lex r l₁ l₂ ∨ ¬ Lex r l₂ l₁ := by
-  rw [Decidable.or_iff_not_imp_left, Decidable.not_not]
-  intro w₁ w₂
-  match l₁, l₂, w₁, w₂ with
-  | nil, _ :: _, .nil, w₂ => simp at w₂
-  | x :: _, y :: _, .rel _, .rel _ =>
-    obtain (_ | _) := h x y <;> contradiction
-  | x :: _, _ :: _, .rel _, .cons _ =>
-    obtain (_ | _) := h x x <;> contradiction
-  | x :: _, _ :: _, .cons  _, .rel _ =>
-    obtain (_ | _) := h x x <;> contradiction
-  | _ :: l₁, _ :: l₂, .cons _, .cons _ =>
-    obtain (_ | _) := not_lex_total h l₁ l₂ <;> contradiction
-
-protected theorem le_total [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Total (¬ · < · : α → α → Prop)] {l₁ l₂ : List α} : l₁ ≤ l₂ ∨ l₂ ≤ l₁ :=
-  not_lex_total i.total l₂ l₁
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Total (¬ · < · : α → α → Prop)] :
-    Std.Total (· ≤ · : List α → List α → Prop) where
-  total _ _ := List.le_total
-
-theorem lex_eq_decide_lex [DecidableEq α] (lt : α → α → Bool) :
-    lex l₁ l₂ lt = decide (Lex (fun x y => lt x y) l₁ l₂) := by
-  induction l₁ generalizing l₂ with
-  | nil =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b bs => simp [lex]
-  | cons a l₁ ih =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b bs =>
-      simp [lex, ih, cons_lex_cons_iff, Bool.beq_eq_decide_eq]
-
-/-- Variant of `lex_eq_true_iff` using an arbitrary comparator. -/
-@[simp] theorem lex_eq_true_iff_lex [DecidableEq α] (lt : α → α → Bool) :
-    lex l₁ l₂ lt = true ↔ Lex (fun x y => lt x y) l₁ l₂ := by
-  simp [lex_eq_decide_lex]
-
-/-- Variant of `lex_eq_false_iff` using an arbitrary comparator. -/
-@[simp] theorem lex_eq_false_iff_not_lex [DecidableEq α] (lt : α → α → Bool) :
-    lex l₁ l₂ lt = false ↔ ¬ Lex (fun x y => lt x y) l₁ l₂ := by
-  simp [Bool.eq_false_iff, lex_eq_true_iff_lex]
-
-@[simp] theorem lex_eq_true_iff_lt [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : List α} : lex l₁ l₂ = true ↔ l₁ < l₂ := by
-  simp only [lex_eq_true_iff_lex, decide_eq_true_eq]
-  exact Iff.rfl
-
-@[simp] theorem lex_eq_false_iff_ge [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : List α} : lex l₁ l₂ = false ↔ l₂ ≤ l₁ := by
-  simp only [lex_eq_false_iff_not_lex, decide_eq_true_eq]
-  exact Iff.rfl
-
-attribute [local simp] Nat.add_one_lt_add_one_iff in
-/--
-`l₁` is lexicographically less than `l₂` if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.length`,
-  and `l₁` is shorter than `l₂` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₁[i] < l₂[i]`
--/
-theorem lex_eq_true_iff_exists [BEq α] (lt : α → α → Bool) :
-    lex l₁ l₂ lt = true ↔
-      (l₁.isEqv (l₂.take l₁.length) (· == ·) ∧ l₁.length < l₂.length) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.length) (h₂ : i < l₂.length),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) == l₂[j]'(Nat.lt_trans hj h₂)) ∧ lt l₁[i] l₂[i]) := by
-  induction l₁ generalizing l₂ with
-  | nil =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b bs => simp [lex]
-  | cons a l₁ ih =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b l₂ =>
-      simp only [lex_cons_cons, Bool.or_eq_true, Bool.and_eq_true, ih, isEqv, length_cons]
-      constructor
-      · rintro (hab | ⟨hab, ⟨h₁, h₂⟩ | ⟨i, h₁, h₂, w₁, w₂⟩⟩)
-        · exact .inr ⟨0, by simp [hab]⟩
-        · exact .inl ⟨⟨hab, h₁⟩, by simpa using h₂⟩
-        · refine .inr ⟨i + 1, by simp [h₁],
-            by simp [h₂], ?_, ?_⟩
-          · intro j hj
-            cases j with
-            | zero => simp [hab]
-            | succ j =>
-              simp only [getElem_cons_succ]
-              rw [w₁]
-              simpa using hj
-          · simpa using w₂
-      · rintro (⟨⟨h₁, h₂⟩, h₃⟩ | ⟨i, h₁, h₂, w₁, w₂⟩)
-        · exact .inr ⟨h₁, .inl ⟨h₂, by simpa using h₃⟩⟩
-        · cases i with
-          | zero =>
-            left
-            simpa using w₂
-          | succ i =>
-            right
-            refine ⟨by simpa using w₁ 0 (by simp), ?_⟩
-            right
-            refine ⟨i, by simpa using h₁, by simpa using h₂, ?_, ?_⟩
-            · intro j hj
-              simpa using w₁ (j + 1) (by simpa)
-            · simpa using w₂
-
-attribute [local simp] Nat.add_one_lt_add_one_iff in
-/--
-`l₁` is *not* lexicographically less than `l₂`
-(which you might think of as "`l₂` is lexicographically greater than or equal to `l₁`"") if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.length` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₂[i] < l₁[i]`
-
-This formulation requires that `==` and `lt` are compatible in the following senses:
-- `==` is symmetric
-  (we unnecessarily further assume it is transitive, to make use of the existing typeclasses)
-- `lt` is irreflexive with respect to `==` (i.e. if `x == y` then `lt x y = false`
-- `lt` is asymmmetric  (i.e. `lt x y = true → lt y x = false`)
-- `lt` is antisymmetric with respect to `==` (i.e. `lt x y = false → lt y x = false → x == y`)
--/
-theorem lex_eq_false_iff_exists [BEq α] [PartialEquivBEq α] (lt : α → α → Bool)
-    (lt_irrefl : ∀ x y, x == y → lt x y = false)
-    (lt_asymm : ∀ x y, lt x y = true → lt y x = false)
-    (lt_antisymm : ∀ x y, lt x y = false → lt y x = false → x == y) :
-    lex l₁ l₂ lt = false ↔
-      (l₂.isEqv (l₁.take l₂.length) (· == ·)) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.length) (h₂ : i < l₂.length),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) == l₂[j]'(Nat.lt_trans hj h₂)) ∧ lt l₂[i] l₁[i]) := by
-  induction l₁ generalizing l₂ with
-  | nil =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b bs => simp [lex]
-  | cons a l₁ ih =>
-    cases l₂ with
-    | nil => simp [lex]
-    | cons b l₂ =>
-      simp only [lex_cons_cons, Bool.or_eq_false_iff, Bool.and_eq_false_imp, ih, isEqv,
-        Bool.and_eq_true, length_cons]
-      constructor
-      · rintro ⟨hab, h⟩
-        if eq : b == a then
-          specialize h (BEq.symm eq)
-          obtain (h | ⟨i, h₁, h₂, w₁, w₂⟩) := h
-          · exact .inl ⟨eq, h⟩
-          · refine .inr ⟨i + 1, by simpa using h₁, by simpa using h₂, ?_, ?_⟩
-            · intro j hj
-              cases j with
-              | zero => simpa using BEq.symm eq
-              | succ j =>
-                simp only [getElem_cons_succ]
-                rw [w₁]
-                simpa using hj
-            · simpa using w₂
-        else
-          right
-          have hba : lt b a :=
-            Decidable.byContradiction fun hba => eq (lt_antisymm _ _ (by simpa using hba) hab)
-          exact ⟨0, by simp, by simp, by simpa⟩
-      · rintro (⟨eq, h⟩ | ⟨i, h₁, h₂, w₁, w₂⟩)
-        · exact ⟨lt_irrefl _ _ (BEq.symm eq), fun _ => .inl h⟩
-        · cases i with
-          | zero =>
-            simp at w₂
-            refine ⟨lt_asymm _ _ w₂, ?_⟩
-            intro eq
-            exfalso
-            simp [lt_irrefl _ _ (BEq.symm eq)] at w₂
-          | succ i =>
-            refine ⟨lt_irrefl _ _ (by simpa using w₁ 0 (by simp)), ?_⟩
-            refine fun _ => .inr ⟨i, by simpa using h₁, by simpa using h₂, ?_, ?_⟩
-            · intro j hj
-              simpa using w₁ (j + 1) (by simpa)
-            · simpa using w₂
-
-theorem lt_iff_exists [DecidableEq α] [LT α] [DecidableLT α] {l₁ l₂ : List α} :
-    l₁ < l₂ ↔
-      (l₁ = l₂.take l₁.length ∧ l₁.length < l₂.length) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.length) (h₂ : i < l₂.length),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) = l₂[j]'(Nat.lt_trans hj h₂)) ∧ l₁[i] < l₂[i]) := by
-  rw [← lex_eq_true_iff_lt, lex_eq_true_iff_exists]
-  simp
-
-theorem le_iff_exists [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)] {l₁ l₂ : List α} :
-    l₁ ≤ l₂ ↔
-      (l₁ = l₂.take l₁.length) ∨
-        (∃ (i : Nat) (h₁ : i < l₁.length) (h₂ : i < l₂.length),
-          (∀ j, (hj : j < i) →
-            l₁[j]'(Nat.lt_trans hj h₁) = l₂[j]'(Nat.lt_trans hj h₂)) ∧ l₁[i] < l₂[i]) := by
-  rw [← lex_eq_false_iff_ge, lex_eq_false_iff_exists]
-  · simp only [isEqv_eq, beq_iff_eq, decide_eq_true_eq]
-    simp only [eq_comm]
-    conv => lhs; simp +singlePass [exists_comm]
-  · simpa using Std.Irrefl.irrefl
-  · simpa using Std.Asymm.asymm
-  · simpa using Std.Antisymm.antisymm
-
-end List

src/Init/Data/List/MinMax.lean

@@ -85,7 +85,7 @@ theorem min?_eq_some_iff [Min α] [LE α] [anti : Std.Antisymm ((· : α) ≤ ·
   cases xs with
   | nil => simp at h₁
   | cons x xs =>
-    exact congrArg some <| anti.1 _ _
+    exact congrArg some <| anti.1
       ((le_min?_iff le_min_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)
       (h₂ _ (min?_mem min_eq_or (xs := x::xs) rfl))
 
@@ -156,7 +156,7 @@ theorem max?_eq_some_iff [Max α] [LE α] [anti : Std.Antisymm ((· : α) ≤ ·
   cases xs with
   | nil => simp at h₁
   | cons x xs =>
-    exact congrArg some <| anti.1 _ _
+    exact congrArg some <| anti.1
       (h₂ _ (max?_mem max_eq_or (xs := x::xs) rfl))
       ((max?_le_iff max_le_iff (xs := x::xs) rfl).1 (le_refl _) _ h₁)
 

src/Init/Data/List/Monadic.lean

@@ -124,8 +124,7 @@ theorem foldrM_filter [Monad m] [LawfulMonad m] (p : α → Bool) (g : α → β
 
 /-! ### forM -/
 
--- We currently use `List.forM` as the simp normal form, rather that `ForM.forM`.
--- (This should probably be revisited.)
+-- We use `List.forM` as the simp normal form, rather that `ForM.forM`.
 -- As such we need to replace `List.forM_nil` and `List.forM_cons`:
 
 @[simp] theorem forM_nil' [Monad m] : ([] : List α).forM f = (pure .unit : m PUnit) := rfl
@@ -138,10 +137,6 @@ theorem foldrM_filter [Monad m] [LawfulMonad m] (p : α → Bool) (g : α → β
     (l₁ ++ l₂).forM f = (do l₁.forM f; l₂.forM f) := by
   induction l₁ <;> simp [*]
 
-@[simp] theorem forM_map [Monad m] [LawfulMonad m] (l : List α) (g : α → β) (f : β → m PUnit) :
-    (l.map g).forM f = l.forM (fun a => f (g a)) := by
-  induction l <;> simp [*]
-
 /-! ### forIn' -/
 
 theorem forIn'_loop_congr [Monad m] {as bs : List α}
@@ -264,11 +259,6 @@ theorem forIn'_pure_yield_eq_foldl [Monad m] [LawfulMonad m]
   generalize l.attach = l'
   induction l' generalizing init <;> simp_all
 
-@[simp] theorem forIn'_map [Monad m] [LawfulMonad m]
-    (l : List α) (g : α → β) (f : (b : β) → b ∈ l.map g → γ → m (ForInStep γ)) :
-    forIn' (l.map g) init f = forIn' l init fun a h y => f (g a) (mem_map_of_mem g h) y := by
-  induction l generalizing init <;> simp_all
-
 /--
 We can express a for loop over a list as a fold,
 in which whenever we reach `.done b` we keep that value through the rest of the fold.
@@ -317,11 +307,6 @@ theorem forIn_pure_yield_eq_foldl [Monad m] [LawfulMonad m]
   simp only [forIn_eq_foldlM]
   induction l generalizing init <;> simp_all
 
-@[simp] theorem forIn_map [Monad m] [LawfulMonad m]
-    (l : List α) (g : α → β) (f : β → γ → m (ForInStep γ)) :
-    forIn (l.map g) init f = forIn l init fun a y => f (g a) y := by
-  induction l generalizing init <;> simp_all
-
 /-! ### allM -/
 
 theorem allM_eq_not_anyM_not [Monad m] [LawfulMonad m] (p : α → m Bool) (as : List α) :

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

@@ -68,8 +68,8 @@ theorem getElem?_modifyHead {l : List α} {f : α → α} {n} :
     (l.modifyHead f).drop n = l.drop n := by
   cases l <;> cases n <;> simp_all
 
-theorem eraseIdx_modifyHead_zero {f : α → α} {l : List α} :
-    (l.modifyHead f).eraseIdx 0 = l.eraseIdx 0 := by simp
+@[simp] theorem eraseIdx_modifyHead_zero {f : α → α} {l : List α} :
+    (l.modifyHead f).eraseIdx 0 = l.eraseIdx 0 := by cases l <;> simp
 
 @[simp] theorem eraseIdx_modifyHead_of_pos {f : α → α} {l : List α} {n} (h : 0 < n) :
     (l.modifyHead f).eraseIdx n = (l.eraseIdx n).modifyHead f := by cases l <;> cases n <;> simp_all
@@ -142,7 +142,7 @@ theorem modifyTailIdx_modifyTailIdx_self {f g : List α → List α} (n : Nat) (
 theorem modifyHead_eq_modify_zero (f : α → α) (l : List α) :
     l.modifyHead f = l.modify f 0 := by cases l <;> simp
 
-@[simp] theorem modify_eq_nil_iff {f : α → α} {n} {l : List α} :
+@[simp] theorem modify_eq_nil_iff (f : α → α) (n) (l : List α) :
     l.modify f n = [] ↔ l = [] := by cases l <;> cases n <;> simp
 
 theorem getElem?_modify (f : α → α) :

src/Init/Data/List/Notation.lean

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Author: Leonardo de Moura
 -/
 prelude
-import Init.Data.Nat.Div.Basic
+import Init.Data.Nat.Div
 
 /-!
 # Notation for `List` literals.

src/Init/Data/List/Range.lean

@@ -84,15 +84,11 @@ theorem head?_range' (n : Nat) : (range' s n).head? = if n = 0 then none else so
 @[simp] theorem head_range' (n : Nat) (h) : (range' s n).head h = s := by
   repeat simp_all [head?_range', head_eq_iff_head?_eq_some]
 
+@[simp]
 theorem map_add_range' (a) : ∀ s n step, map (a + ·) (range' s n step) = range' (a + s) n step
   | _, 0, _ => rfl
   | s, n + 1, step => by simp [range', map_add_range' _ (s + step) n step, Nat.add_assoc]
 
-theorem range'_succ_left : range' (s + 1) n step = (range' s n step).map (· + 1) := by
-  apply ext_getElem
-  · simp
-  · simp [Nat.add_right_comm]
-
 theorem range'_append : ∀ s m n step : Nat,
     range' s m step ++ range' (s + step * m) n step = range' s (n + m) step
   | _, 0, _, _ => rfl

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

@@ -40,15 +40,12 @@ def merge (xs ys : List α) (le : α → α → Bool := by exact fun a b => a
 
 /--
 Split a list in two equal parts. If the length is odd, the first part will be one element longer.
-
-This is an implementation detail of `mergeSort`.
 -/
-def MergeSort.Internal.splitInTwo (l : { l : List α // l.length = n }) :
+def splitInTwo (l : { l : List α // l.length = n }) :
     { l : List α // l.length = (n+1)/2 } × { l : List α // l.length = n/2 } :=
   let r := splitAt ((n+1)/2) l.1
   (⟨r.1, by simp [r, splitAt_eq, l.2]; omega⟩, ⟨r.2, by simp [r, splitAt_eq, l.2]; omega⟩)
 
-open MergeSort.Internal in
 set_option linter.unusedVariables false in
 /--
 Simplified implementation of stable merge sort.

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

@@ -147,21 +147,23 @@ where
     mergeTR (run' r) (run l) le
 
 theorem splitRevInTwo'_fst (l : { l : List α // l.length = n }) :
-    (splitRevInTwo' l).1 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).2.1, by simp; omega⟩ := by
+    (splitRevInTwo' l).1 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).2.1, by have := l.2; simp; omega⟩ := by
   simp only [splitRevInTwo', splitRevAt_eq, reverse_take, splitInTwo_snd]
   congr
+  have := l.2
   omega
 theorem splitRevInTwo'_snd (l : { l : List α // l.length = n }) :
-    (splitRevInTwo' l).2 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).1.1.reverse, by simp; omega⟩ := by
+    (splitRevInTwo' l).2 = ⟨(splitInTwo ⟨l.1.reverse, by simpa using l.2⟩).1.1.reverse, by have := l.2; simp; omega⟩ := by
   simp only [splitRevInTwo', splitRevAt_eq, reverse_take, splitInTwo_fst, reverse_reverse]
   congr 2
+  have := l.2
   simp
   omega
 theorem splitRevInTwo_fst (l : { l : List α // l.length = n }) :
-    (splitRevInTwo l).1 = ⟨(splitInTwo l).1.1.reverse, by simp; omega⟩ := by
+    (splitRevInTwo l).1 = ⟨(splitInTwo l).1.1.reverse, by have := l.2; simp; omega⟩ := by
   simp only [splitRevInTwo, splitRevAt_eq, reverse_take, splitInTwo_fst]
 theorem splitRevInTwo_snd (l : { l : List α // l.length = n }) :
-    (splitRevInTwo l).2 = ⟨(splitInTwo l).2.1, by simp; omega⟩ := by
+    (splitRevInTwo l).2 = ⟨(splitInTwo l).2.1, by have := l.2; simp; omega⟩ := by
   simp only [splitRevInTwo, splitRevAt_eq, reverse_take, splitInTwo_snd]
 
 theorem mergeSortTR_run_eq_mergeSort : {n : Nat} → (l : { l : List α // l.length = n }) → mergeSortTR.run le l = mergeSort l.1 le

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

@@ -25,8 +25,6 @@ namespace List
 
 /-! ### splitInTwo -/
 
-namespace MergeSort.Internal
-
 @[simp] theorem splitInTwo_fst (l : { l : List α // l.length = n }) :
     (splitInTwo l).1 = ⟨l.1.take ((n+1)/2), by simp [splitInTwo, splitAt_eq, l.2]; omega⟩ := by
   simp [splitInTwo, splitAt_eq]
@@ -84,10 +82,6 @@ theorem splitInTwo_fst_le_splitInTwo_snd {l : { l : List α // l.length = n }} (
   intro a b ma mb
   exact h.rel_of_mem_take_of_mem_drop ma mb
 
-end MergeSort.Internal
-
-open MergeSort.Internal
-
 /-! ### enumLE -/
 
 variable {le : α → α → Bool}
@@ -291,6 +285,8 @@ theorem sorted_mergeSort
   | [] => by simp [mergeSort]
   | [a] => by simp [mergeSort]
   | a :: b :: xs => by
+    have : (splitInTwo ⟨a :: b :: xs, rfl⟩).1.1.length < xs.length + 1 + 1 := by simp [splitInTwo_fst]; omega
+    have : (splitInTwo ⟨a :: b :: xs, rfl⟩).2.1.length < xs.length + 1 + 1 := by simp [splitInTwo_snd]; omega
     rw [mergeSort]
     apply sorted_merge @trans @total
     apply sorted_mergeSort trans total

src/Init/Data/List/ToArray.lean

@@ -7,7 +7,6 @@ prelude
 import Init.Data.List.Impl
 import Init.Data.List.Nat.Erase
 import Init.Data.List.Monadic
-import Init.Data.Array.Lex.Basic
 
 /-! ### Lemmas about `List.toArray`.
 
@@ -29,11 +28,6 @@ theorem toArray_inj {a b : List α} (h : a.toArray = b.toArray) : a = b := by
     (a.toArrayAux b).size = b.size + a.length := by
   simp [size]
 
--- This is not a `@[simp]` lemma because it is pushing `toArray` inwards.
-theorem toArray_cons (a : α) (l : List α) : (a :: l).toArray = #[a] ++ l.toArray := by
-  apply ext'
-  simp
-
 @[simp] theorem push_toArray (l : List α) (a : α) : l.toArray.push a = (l ++ [a]).toArray := by
   apply ext'
   simp
@@ -44,7 +38,7 @@ theorem toArray_cons (a : α) (l : List α) : (a :: l).toArray = #[a] ++ l.toArr
   simp
 
 @[simp] theorem isEmpty_toArray (l : List α) : l.toArray.isEmpty = l.isEmpty := by
-  cases l <;> simp [Array.isEmpty]
+  cases l <;> simp
 
 @[simp] theorem toArray_singleton (a : α) : (List.singleton a).toArray = singleton a := rfl
 
@@ -117,18 +111,6 @@ theorem foldl_toArray (f : β → α → β) (init : β) (l : List α) :
   subst h
   rw [foldlM_toList]
 
-/-- Variant of `forM_toArray` with a side condition for the `stop` argument. -/
-@[simp] theorem forM_toArray' [Monad m] (l : List α) (f : α → m PUnit) (h : stop = l.toArray.size) :
-    (l.toArray.forM f 0 stop) = l.forM f := by
-  subst h
-  rw [Array.forM]
-  simp only [size_toArray, foldlM_toArray']
-  induction l <;> simp_all
-
-theorem forM_toArray [Monad m] (l : List α) (f : α → m PUnit) :
-    (l.toArray.forM f) = l.forM f := by
-  simp
-
 /-- Variant of `foldr_toArray` with a side condition for the `start` argument. -/
 @[simp] theorem foldr_toArray' (f : α → β → β) (init : β) (l : List α)
     (h : start = l.toArray.size) :
@@ -389,9 +371,4 @@ theorem takeWhile_go_toArray (p : α → Bool) (l : List α) (i : Nat) :
   · simp
   · simp_all [List.set_eq_of_length_le]
 
-@[simp] theorem toArray_replicate (n : Nat) (v : α) : (List.replicate n v).toArray = mkArray n v := rfl
-
-@[deprecated toArray_replicate (since := "2024-12-13")]
-abbrev _root_.Array.mkArray_eq_toArray_replicate := @toArray_replicate
-
 end List

src/Init/Data/Nat.lean

@@ -5,7 +5,7 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Nat.Basic
-import Init.Data.Nat.Div.Basic
+import Init.Data.Nat.Div
 import Init.Data.Nat.Dvd
 import Init.Data.Nat.Gcd
 import Init.Data.Nat.MinMax

src/Init/Data/Nat/Basic.lean

@@ -445,10 +445,10 @@ protected theorem le_antisymm_iff {a b : Nat} : a = b ↔ a ≤ b ∧ b ≤ a :=
 protected theorem eq_iff_le_and_ge : ∀{a b : Nat}, a = b ↔ a ≤ b ∧ b ≤ a := @Nat.le_antisymm_iff
 
 instance : Std.Antisymm ( . ≤ . : Nat → Nat → Prop) where
-  antisymm _ _ h₁ h₂ := Nat.le_antisymm h₁ h₂
+  antisymm h₁ h₂ := Nat.le_antisymm h₁ h₂
 
 instance : Std.Antisymm (¬ . < . : Nat → Nat → Prop) where
-  antisymm _ _ h₁ h₂ := Nat.le_antisymm (Nat.ge_of_not_lt h₂) (Nat.ge_of_not_lt h₁)
+  antisymm h₁ h₂ := Nat.le_antisymm (Nat.ge_of_not_lt h₂) (Nat.ge_of_not_lt h₁)
 
 protected theorem add_le_add_left {n m : Nat} (h : n ≤ m) (k : Nat) : k + n ≤ k + m :=
   match le.dest h with

src/Init/Data/Nat/Bitwise/Basic.lean

@@ -5,7 +5,7 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Nat.Basic
-import Init.Data.Nat.Div.Basic
+import Init.Data.Nat.Div
 import Init.Coe
 
 namespace Nat

src/Init/Data/Nat/Bitwise/Lemmas.lean

@@ -106,21 +106,9 @@ theorem testBit_add_one (x i : Nat) : testBit x (i + 1) = testBit (x/2) i := by
   unfold testBit
   simp [shiftRight_succ_inside]
 
-theorem testBit_add (x i n : Nat) : testBit x (i + n) = testBit (x / 2 ^ n) i := by
-  revert x
-  induction n with
-  | zero => simp
-  | succ n ih =>
-    intro x
-    rw [← Nat.add_assoc, testBit_add_one, ih (x / 2),
-      Nat.pow_succ, Nat.div_div_eq_div_mul, Nat.mul_comm]
-
 theorem testBit_div_two (x i : Nat) : testBit (x / 2) i = testBit x (i + 1) := by
   simp
 
-theorem testBit_div_two_pow (x i : Nat) : testBit (x / 2 ^ n) i = testBit x (i + n) :=
-  testBit_add .. |>.symm
-
 theorem testBit_to_div_mod {x : Nat} : testBit x i = decide (x / 2^i % 2 = 1) := by
   induction i generalizing x with
   | zero =>
@@ -377,7 +365,7 @@ theorem testBit_two_pow_of_ne {n m : Nat} (hm : n ≠ m) : testBit (2 ^ n) m = f
 
 /-! ### bitwise -/
 
-theorem testBit_bitwise (of_false_false : f false false = false) (x y i : Nat) :
+theorem testBit_bitwise (false_false_axiom : f false false = false) (x y i : Nat) :
     (bitwise f x y).testBit i = f (x.testBit i) (y.testBit i) := by
   induction i using Nat.strongRecOn generalizing x y with
   | ind i hyp =>
@@ -385,12 +373,12 @@ theorem testBit_bitwise (of_false_false : f false false = false) (x y i : Nat) :
     if x_zero : x = 0 then
       cases p : f false true <;>
         cases yi : testBit y i <;>
-          simp [x_zero, p, yi, of_false_false]
+          simp [x_zero, p, yi, false_false_axiom]
     else if y_zero : y = 0 then
       simp [x_zero, y_zero]
       cases p : f true false <;>
         cases xi : testBit x i <;>
-          simp [p, xi, of_false_false]
+          simp [p, xi, false_false_axiom]
     else
       simp only [x_zero, y_zero, ←Nat.two_mul]
       cases i with
@@ -452,11 +440,6 @@ theorem bitwise_lt_two_pow (left : x < 2^n) (right : y < 2^n) : (Nat.bitwise f x
       case neg =>
         apply Nat.add_lt_add <;> exact hyp1
 
-theorem bitwise_div_two_pow (of_false_false : f false false = false := by rfl) :
-  (bitwise f x y) / 2 ^ n = bitwise f (x / 2 ^ n) (y / 2 ^ n) := by
-  apply Nat.eq_of_testBit_eq
-  simp [testBit_bitwise of_false_false, testBit_div_two_pow]
-
 /-! ### and -/
 
 @[simp] theorem testBit_and (x y i : Nat) : (x &&& y).testBit i = (x.testBit i && y.testBit i) := by
@@ -512,11 +495,9 @@ theorem and_pow_two_sub_one_of_lt_two_pow {x : Nat} (lt : x < 2^n) : x &&& 2^n -
   rw [testBit_and]
   simp
 
-theorem and_div_two_pow : (a &&& b) / 2 ^ n = a / 2 ^ n &&& b / 2 ^ n :=
-  bitwise_div_two_pow
-
-theorem and_div_two : (a &&& b) / 2 = a / 2 &&& b / 2 :=
-  and_div_two_pow (n := 1)
+theorem and_div_two : (a &&& b) / 2 = a / 2 &&& b / 2 := by
+  apply Nat.eq_of_testBit_eq
+  simp [testBit_and, ← testBit_add_one]
 
 /-! ### lor -/
 
@@ -582,11 +563,9 @@ theorem or_lt_two_pow {x y n : Nat} (left : x < 2^n) (right : y < 2^n) : x ||| y
   rw [testBit_or]
   simp
 
-theorem or_div_two_pow : (a ||| b) / 2 ^ n = a / 2 ^ n ||| b / 2 ^ n :=
-  bitwise_div_two_pow
-
-theorem or_div_two : (a ||| b) / 2 = a / 2 ||| b / 2 :=
-  or_div_two_pow (n := 1)
+theorem or_div_two : (a ||| b) / 2 = a / 2 ||| b / 2 := by
+  apply Nat.eq_of_testBit_eq
+  simp [testBit_or, ← testBit_add_one]
 
 /-! ### xor -/
 
@@ -640,11 +619,9 @@ theorem and_xor_distrib_left {a b c : Nat} : a &&& (b ^^^ c) = (a &&& b) ^^^ (a
   rw [testBit_xor]
   simp
 
-theorem xor_div_two_pow : (a ^^^ b) / 2 ^ n = a / 2 ^ n ^^^ b / 2 ^ n :=
-  bitwise_div_two_pow
-
-theorem xor_div_two : (a ^^^ b) / 2 = a / 2 ^^^ b / 2 :=
-  xor_div_two_pow (n := 1)
+theorem xor_div_two : (a ^^^ b) / 2 = a / 2 ^^^ b / 2 := by
+  apply Nat.eq_of_testBit_eq
+  simp [testBit_xor, ← testBit_add_one]
 
 /-! ### Arithmetic -/
 
@@ -716,19 +693,6 @@ theorem mul_add_lt_is_or {b : Nat} (b_lt : b < 2^i) (a : Nat) : 2^i * a + b = 2^
   simp only [testBit, one_and_eq_mod_two, mod_two_bne_zero]
   exact (Bool.beq_eq_decide_eq _ _).symm
 
-theorem shiftRight_bitwise_distrib {a b : Nat} (of_false_false : f false false = false := by rfl) :
-    (bitwise f a b) >>> i = bitwise f (a >>> i) (b >>> i) := by
-  simp [shiftRight_eq_div_pow, bitwise_div_two_pow of_false_false]
-
-theorem shiftRight_and_distrib {a b : Nat} : (a &&& b) >>> i = a >>> i &&& b >>> i :=
-  shiftRight_bitwise_distrib
-
-theorem shiftRight_or_distrib {a b : Nat} : (a ||| b) >>> i = a >>> i ||| b >>> i :=
-  shiftRight_bitwise_distrib
-
-theorem shiftRight_xor_distrib {a b : Nat} : (a ^^^ b) >>> i = a >>> i ^^^ b >>> i :=
-  shiftRight_bitwise_distrib
-
 /-! ### le -/
 
 theorem le_of_testBit {n m : Nat} (h : ∀ i, n.testBit i = true → m.testBit i = true) : n ≤ m := by

src/Init/Data/Nat/Div.lean

@@ -1,8 +1,418 @@
 /-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
+Copyright (c) 2016 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
+Authors: Leonardo de Moura
 -/
 prelude
-import Init.Data.Nat.Div.Basic
-import Init.Data.Nat.Div.Lemmas
+import Init.WF
+import Init.WFTactics
+import Init.Data.Nat.Basic
+
+namespace Nat
+
+/--
+Divisibility of natural numbers. `a ∣ b` (typed as `\|`) says that
+there is some `c` such that `b = a * c`.
+-/
+instance : Dvd Nat where
+  dvd a b := Exists (fun c => b = a * c)
+
+theorem div_rec_lemma {x y : Nat} : 0 < y ∧ y ≤ x → x - y < x :=
+  fun ⟨ypos, ylex⟩ => sub_lt (Nat.lt_of_lt_of_le ypos ylex) ypos
+
+@[extern "lean_nat_div"]
+protected def div (x y : @& Nat) : Nat :=
+  if 0 < y ∧ y ≤ x then
+    Nat.div (x - y) y + 1
+  else
+    0
+decreasing_by apply div_rec_lemma; assumption
+
+instance instDiv : Div Nat := ⟨Nat.div⟩
+
+theorem div_eq (x y : Nat) : x / y = if 0 < y ∧ y ≤ x then (x - y) / y + 1 else 0 := by
+  show Nat.div x y = _
+  rw [Nat.div]
+  rfl
+
+def div.inductionOn.{u}
+      {motive : Nat → Nat → Sort u}
+      (x y : Nat)
+      (ind  : ∀ x y, 0 < y ∧ y ≤ x → motive (x - y) y → motive x y)
+      (base : ∀ x y, ¬(0 < y ∧ y ≤ x) → motive x y)
+      : motive x y :=
+  if h : 0 < y ∧ y ≤ x then
+    ind x y h (inductionOn (x - y) y ind base)
+  else
+    base x y h
+decreasing_by apply div_rec_lemma; assumption
+
+theorem div_le_self (n k : Nat) : n / k ≤ n := by
+  induction n using Nat.strongRecOn with
+  | ind n ih =>
+    rw [div_eq]
+    -- Note: manual split to avoid Classical.em which is not yet defined
+    cases (inferInstance : Decidable (0 < k ∧ k ≤ n)) with
+    | isFalse h => simp [h]
+    | isTrue h =>
+      suffices (n - k) / k + 1 ≤ n by simp [h, this]
+      have ⟨hK, hKN⟩ := h
+      have hSub : n - k < n := sub_lt (Nat.lt_of_lt_of_le hK hKN) hK
+      have : (n - k) / k ≤ n - k := ih (n - k) hSub
+      exact succ_le_of_lt (Nat.lt_of_le_of_lt this hSub)
+
+theorem div_lt_self {n k : Nat} (hLtN : 0 < n) (hLtK : 1 < k) : n / k < n := by
+  rw [div_eq]
+  cases (inferInstance : Decidable (0 < k ∧ k ≤ n)) with
+  | isFalse h => simp [hLtN, h]
+  | isTrue h =>
+    suffices (n - k) / k + 1 < n by simp [h, this]
+    have ⟨_, hKN⟩ := h
+    have : (n - k) / k ≤ n - k := div_le_self (n - k) k
+    have := Nat.add_le_of_le_sub hKN this
+    exact Nat.lt_of_lt_of_le (Nat.add_lt_add_left hLtK _) this
+
+@[extern "lean_nat_mod"]
+protected def modCore (x y : @& Nat) : Nat :=
+  if 0 < y ∧ y ≤ x then
+    Nat.modCore (x - y) y
+  else
+    x
+decreasing_by apply div_rec_lemma; assumption
+
+@[extern "lean_nat_mod"]
+protected def mod : @& Nat → @& Nat → Nat
+  /-
+  Nat.modCore is defined by well-founded recursion and thus irreducible. Nevertheless it is
+  desirable if trivial `Nat.mod` calculations, namely
+  * `Nat.mod 0 m` for all `m`
+  * `Nat.mod n (m+n)` for concrete literals `n`
+  reduce definitionally.
+  This property is desirable for `Fin n` literals, as it means `(ofNat 0 : Fin n).val = 0` by
+  definition.
+   -/
+  | 0, _ => 0
+  | n@(_ + 1), m =>
+    if m ≤ n -- NB: if n < m does not reduce as well as `m ≤ n`!
+    then Nat.modCore n m
+    else n
+
+instance instMod : Mod Nat := ⟨Nat.mod⟩
+
+protected theorem modCore_eq_mod (n m : Nat) : Nat.modCore n m = n % m := by
+  show Nat.modCore n m = Nat.mod n m
+  match n, m with
+  | 0, _ =>
+    rw [Nat.modCore]
+    exact if_neg fun ⟨hlt, hle⟩ => Nat.lt_irrefl _ (Nat.lt_of_lt_of_le hlt hle)
+  | (_ + 1), _ =>
+    rw [Nat.mod]; dsimp
+    refine iteInduction (fun _ => rfl) (fun h => ?false) -- cannot use `split` this early yet
+    rw [Nat.modCore]
+    exact if_neg fun ⟨_hlt, hle⟩ => h hle
+
+theorem mod_eq (x y : Nat) : x % y = if 0 < y ∧ y ≤ x then (x - y) % y else x := by
+  rw [←Nat.modCore_eq_mod, ←Nat.modCore_eq_mod, Nat.modCore]
+
+def mod.inductionOn.{u}
+      {motive : Nat → Nat → Sort u}
+      (x y  : Nat)
+      (ind  : ∀ x y, 0 < y ∧ y ≤ x → motive (x - y) y → motive x y)
+      (base : ∀ x y, ¬(0 < y ∧ y ≤ x) → motive x y)
+      : motive x y :=
+  div.inductionOn x y ind base
+
+@[simp] theorem mod_zero (a : Nat) : a % 0 = a :=
+  have : (if 0 < 0 ∧ 0 ≤ a then (a - 0) % 0 else a) = a :=
+    have h : ¬ (0 < 0 ∧ 0 ≤ a) := fun ⟨h₁, _⟩ => absurd h₁ (Nat.lt_irrefl _)
+    if_neg h
+  (mod_eq a 0).symm ▸ this
+
+theorem mod_eq_of_lt {a b : Nat} (h : a < b) : a % b = a :=
+  have : (if 0 < b ∧ b ≤ a then (a - b) % b else a) = a :=
+    have h' : ¬(0 < b ∧ b ≤ a) := fun ⟨_, h₁⟩ => absurd h₁ (Nat.not_le_of_gt h)
+    if_neg h'
+  (mod_eq a b).symm ▸ this
+
+@[simp] theorem one_mod_eq_zero_iff {n : Nat} : 1 % n = 0 ↔ n = 1 := by
+  match n with
+  | 0 => simp
+  | 1 => simp
+  | n + 2 =>
+    rw [mod_eq_of_lt (by exact Nat.lt_of_sub_eq_succ rfl)]
+    simp only [add_one_ne_zero, false_iff, ne_eq]
+    exact ne_of_beq_eq_false rfl
+
+@[simp] theorem Nat.zero_eq_one_mod_iff {n : Nat} : 0 = 1 % n ↔ n = 1 := by
+  rw [eq_comm]
+  simp
+
+theorem mod_eq_sub_mod {a b : Nat} (h : a ≥ b) : a % b = (a - b) % b :=
+  match eq_zero_or_pos b with
+  | Or.inl h₁ => h₁.symm ▸ (Nat.sub_zero a).symm ▸ rfl
+  | Or.inr h₁ => (mod_eq a b).symm ▸ if_pos ⟨h₁, h⟩
+
+theorem mod_lt (x : Nat) {y : Nat} : y > 0 → x % y < y := by
+  induction x, y using mod.inductionOn with
+  | base x y h₁ =>
+    intro h₂
+    have h₁ : ¬ 0 < y ∨ ¬ y ≤ x := Decidable.not_and_iff_or_not.mp h₁
+    match h₁ with
+    | Or.inl h₁ => exact absurd h₂ h₁
+    | Or.inr h₁ =>
+      have hgt : y > x := gt_of_not_le h₁
+      have heq : x % y = x := mod_eq_of_lt hgt
+      rw [← heq] at hgt
+      exact hgt
+  | ind x y h h₂ =>
+    intro h₃
+    have ⟨_, h₁⟩ := h
+    rw [mod_eq_sub_mod h₁]
+    exact h₂ h₃
+
+@[simp] protected theorem sub_mod_add_mod_cancel (a b : Nat) [NeZero a] : a - b % a + b % a = a := by
+  rw [Nat.sub_add_cancel]
+  cases a with
+  | zero => simp_all
+  | succ a =>
+    exact Nat.le_of_lt (mod_lt b (zero_lt_succ a))
+
+theorem mod_le (x y : Nat) : x % y ≤ x := by
+  match Nat.lt_or_ge x y with
+  | Or.inl h₁ => rw [mod_eq_of_lt h₁]; apply Nat.le_refl
+  | Or.inr h₁ => match eq_zero_or_pos y with
+    | Or.inl h₂ => rw [h₂, Nat.mod_zero x]; apply Nat.le_refl
+    | Or.inr h₂ => exact Nat.le_trans (Nat.le_of_lt (mod_lt _ h₂)) h₁
+
+@[simp] theorem zero_mod (b : Nat) : 0 % b = 0 := by
+  rw [mod_eq]
+  have : ¬ (0 < b ∧ b = 0) := by
+    intro ⟨h₁, h₂⟩
+    simp_all
+  simp [this]
+
+@[simp] theorem mod_self (n : Nat) : n % n = 0 := by
+  rw [mod_eq_sub_mod (Nat.le_refl _), Nat.sub_self, zero_mod]
+
+theorem mod_one (x : Nat) : x % 1 = 0 := by
+  have h : x % 1 < 1 := mod_lt x (by decide)
+  have : (y : Nat) → y < 1 → y = 0 := by
+    intro y
+    cases y with
+    | zero   => intro _; rfl
+    | succ y => intro h; apply absurd (Nat.lt_of_succ_lt_succ h) (Nat.not_lt_zero y)
+  exact this _ h
+
+theorem div_add_mod (m n : Nat) : n * (m / n) + m % n = m := by
+  rw [div_eq, mod_eq]
+  have h : Decidable (0 < n ∧ n ≤ m) := inferInstance
+  cases h with
+  | isFalse h => simp [h]
+  | isTrue h =>
+    simp [h]
+    have ih := div_add_mod (m - n) n
+    rw [Nat.left_distrib, Nat.mul_one, Nat.add_assoc, Nat.add_left_comm, ih, Nat.add_comm, Nat.sub_add_cancel h.2]
+decreasing_by apply div_rec_lemma; assumption
+
+theorem div_eq_sub_div (h₁ : 0 < b) (h₂ : b ≤ a) : a / b = (a - b) / b + 1 := by
+ rw [div_eq a, if_pos]; constructor <;> assumption
+
+theorem mod_add_div (m k : Nat) : m % k + k * (m / k) = m := by
+  induction m, k using mod.inductionOn with rw [div_eq, mod_eq]
+  | base x y h => simp [h]
+  | ind x y h IH => simp [h]; rw [Nat.mul_succ, ← Nat.add_assoc, IH, Nat.sub_add_cancel h.2]
+
+theorem mod_def (m k : Nat) : m % k = m - k * (m / k) := by
+  rw [Nat.sub_eq_of_eq_add]
+  apply (Nat.mod_add_div _ _).symm
+
+@[simp] protected theorem div_one (n : Nat) : n / 1 = n := by
+  have := mod_add_div n 1
+  rwa [mod_one, Nat.zero_add, Nat.one_mul] at this
+
+@[simp] protected theorem div_zero (n : Nat) : n / 0 = 0 := by
+  rw [div_eq]; simp [Nat.lt_irrefl]
+
+@[simp] protected theorem zero_div (b : Nat) : 0 / b = 0 :=
+  (div_eq 0 b).trans <| if_neg <| And.rec Nat.not_le_of_gt
+
+theorem le_div_iff_mul_le (k0 : 0 < k) : x ≤ y / k ↔ x * k ≤ y := by
+  induction y, k using mod.inductionOn generalizing x with
+    (rw [div_eq]; simp [h]; cases x with | zero => simp [zero_le] | succ x => ?_)
+  | base y k h =>
+    simp only [add_one, succ_mul, false_iff, Nat.not_le, Nat.succ_ne_zero]
+    refine Nat.lt_of_lt_of_le ?_ (Nat.le_add_left ..)
+    exact Nat.not_le.1 fun h' => h ⟨k0, h'⟩
+  | ind y k h IH =>
+    rw [Nat.add_le_add_iff_right, IH k0, succ_mul,
+        ← Nat.add_sub_cancel (x*k) k, Nat.sub_le_sub_iff_right h.2, Nat.add_sub_cancel]
+
+protected theorem div_div_eq_div_mul (m n k : Nat) : m / n / k = m / (n * k) := by
+  cases eq_zero_or_pos k with
+  | inl k0 => rw [k0, Nat.mul_zero, Nat.div_zero, Nat.div_zero] | inr kpos => ?_
+  cases eq_zero_or_pos n with
+  | inl n0 => rw [n0, Nat.zero_mul, Nat.div_zero, Nat.zero_div] | inr npos => ?_
+
+  apply Nat.le_antisymm
+
+  apply (le_div_iff_mul_le (Nat.mul_pos npos kpos)).2
+  rw [Nat.mul_comm n k, ← Nat.mul_assoc]
+  apply (le_div_iff_mul_le npos).1
+  apply (le_div_iff_mul_le kpos).1
+  (apply Nat.le_refl)
+
+  apply (le_div_iff_mul_le kpos).2
+  apply (le_div_iff_mul_le npos).2
+  rw [Nat.mul_assoc, Nat.mul_comm n k]
+  apply (le_div_iff_mul_le (Nat.mul_pos kpos npos)).1
+  apply Nat.le_refl
+
+theorem div_mul_le_self : ∀ (m n : Nat), m / n * n ≤ m
+  | m, 0   => by simp
+  | _, _+1 => (le_div_iff_mul_le (Nat.succ_pos _)).1 (Nat.le_refl _)
+
+theorem div_lt_iff_lt_mul (Hk : 0 < k) : x / k < y ↔ x < y * k := by
+  rw [← Nat.not_le, ← Nat.not_le]; exact not_congr (le_div_iff_mul_le Hk)
+
+@[simp] theorem add_div_right (x : Nat) {z : Nat} (H : 0 < z) : (x + z) / z = (x / z) + 1 := by
+  rw [div_eq_sub_div H (Nat.le_add_left _ _), Nat.add_sub_cancel]
+
+@[simp] theorem add_div_left (x : Nat) {z : Nat} (H : 0 < z) : (z + x) / z = (x / z) + 1 := by
+  rw [Nat.add_comm, add_div_right x H]
+
+theorem add_mul_div_left (x z : Nat) {y : Nat} (H : 0 < y) : (x + y * z) / y = x / y + z := by
+  induction z with
+  | zero => rw [Nat.mul_zero, Nat.add_zero, Nat.add_zero]
+  | succ z ih => rw [mul_succ, ← Nat.add_assoc, add_div_right _ H, ih]; rfl
+
+theorem add_mul_div_right (x y : Nat) {z : Nat} (H : 0 < z) : (x + y * z) / z = x / z + y := by
+  rw [Nat.mul_comm, add_mul_div_left _ _ H]
+
+@[simp] theorem add_mod_right (x z : Nat) : (x + z) % z = x % z := by
+  rw [mod_eq_sub_mod (Nat.le_add_left ..), Nat.add_sub_cancel]
+
+@[simp] theorem add_mod_left (x z : Nat) : (x + z) % x = z % x := by
+  rw [Nat.add_comm, add_mod_right]
+
+@[simp] theorem add_mul_mod_self_left (x y z : Nat) : (x + y * z) % y = x % y := by
+  match z with
+  | 0 => rw [Nat.mul_zero, Nat.add_zero]
+  | succ z => rw [mul_succ, ← Nat.add_assoc, add_mod_right, add_mul_mod_self_left (z := z)]
+
+@[simp] theorem add_mul_mod_self_right (x y z : Nat) : (x + y * z) % z = x % z := by
+  rw [Nat.mul_comm, add_mul_mod_self_left]
+
+@[simp] theorem mul_mod_right (m n : Nat) : (m * n) % m = 0 := by
+  rw [← Nat.zero_add (m * n), add_mul_mod_self_left, zero_mod]
+
+@[simp] theorem mul_mod_left (m n : Nat) : (m * n) % n = 0 := by
+  rw [Nat.mul_comm, mul_mod_right]
+
+protected theorem div_eq_of_lt_le (lo : k * n ≤ m) (hi : m < (k + 1) * n) : m / n = k :=
+have npos : 0 < n := (eq_zero_or_pos _).resolve_left fun hn => by
+  rw [hn, Nat.mul_zero] at hi lo; exact absurd lo (Nat.not_le_of_gt hi)
+Nat.le_antisymm
+  (le_of_lt_succ ((Nat.div_lt_iff_lt_mul npos).2 hi))
+  ((Nat.le_div_iff_mul_le npos).2 lo)
+
+theorem sub_mul_div (x n p : Nat) (h₁ : n*p ≤ x) : (x - n*p) / n = x / n - p := by
+  match eq_zero_or_pos n with
+  | .inl h₀ => rw [h₀, Nat.div_zero, Nat.div_zero, Nat.zero_sub]
+  | .inr h₀ => induction p with
+    | zero => rw [Nat.mul_zero, Nat.sub_zero, Nat.sub_zero]
+    | succ p IH =>
+      have h₂ : n * p ≤ x := Nat.le_trans (Nat.mul_le_mul_left _ (le_succ _)) h₁
+      have h₃ : x - n * p ≥ n := by
+        apply Nat.le_of_add_le_add_right
+        rw [Nat.sub_add_cancel h₂, Nat.add_comm]
+        rw [mul_succ] at h₁
+        exact h₁
+      rw [sub_succ, ← IH h₂, div_eq_sub_div h₀ h₃]
+      simp [Nat.pred_succ, mul_succ, Nat.sub_sub]
+
+theorem mul_sub_div (x n p : Nat) (h₁ : x < n*p) : (n * p - (x + 1)) / n = p - ((x / n) + 1) := by
+  have npos : 0 < n := (eq_zero_or_pos _).resolve_left fun n0 => by
+    rw [n0, Nat.zero_mul] at h₁; exact not_lt_zero _ h₁
+  apply Nat.div_eq_of_lt_le
+  focus
+    rw [Nat.mul_sub_right_distrib, Nat.mul_comm]
+    exact Nat.sub_le_sub_left ((div_lt_iff_lt_mul npos).1 (lt_succ_self _)) _
+  focus
+    show succ (pred (n * p - x)) ≤ (succ (pred (p - x / n))) * n
+    rw [succ_pred_eq_of_pos (Nat.sub_pos_of_lt h₁),
+      fun h => succ_pred_eq_of_pos (Nat.sub_pos_of_lt h)] -- TODO: why is the function needed?
+    focus
+      rw [Nat.mul_sub_right_distrib, Nat.mul_comm]
+      exact Nat.sub_le_sub_left (div_mul_le_self ..) _
+    focus
+      rwa [div_lt_iff_lt_mul npos, Nat.mul_comm]
+
+theorem mul_mod_mul_left (z x y : Nat) : (z * x) % (z * y) = z * (x % y) :=
+  if y0 : y = 0 then by
+    rw [y0, Nat.mul_zero, mod_zero, mod_zero]
+  else if z0 : z = 0 then by
+    rw [z0, Nat.zero_mul, Nat.zero_mul, Nat.zero_mul, mod_zero]
+  else by
+    induction x using Nat.strongRecOn with
+    | _ n IH =>
+      have y0 : y > 0 := Nat.pos_of_ne_zero y0
+      have z0 : z > 0 := Nat.pos_of_ne_zero z0
+      cases Nat.lt_or_ge n y with
+      | inl yn => rw [mod_eq_of_lt yn, mod_eq_of_lt (Nat.mul_lt_mul_of_pos_left yn z0)]
+      | inr yn =>
+        rw [mod_eq_sub_mod yn, mod_eq_sub_mod (Nat.mul_le_mul_left z yn),
+          ← Nat.mul_sub_left_distrib]
+        exact IH _ (sub_lt (Nat.lt_of_lt_of_le y0 yn) y0)
+
+theorem div_eq_of_lt (h₀ : a < b) : a / b = 0 := by
+  rw [div_eq a, if_neg]
+  intro h₁
+  apply Nat.not_le_of_gt h₀ h₁.right
+
+protected theorem mul_div_cancel (m : Nat) {n : Nat} (H : 0 < n) : m * n / n = m := by
+  let t := add_mul_div_right 0 m H
+  rwa [Nat.zero_add, Nat.zero_div, Nat.zero_add] at t
+
+protected theorem mul_div_cancel_left (m : Nat) {n : Nat} (H : 0 < n) : n * m / n = m := by
+  rw [Nat.mul_comm, Nat.mul_div_cancel _ H]
+
+protected theorem div_le_of_le_mul {m n : Nat} : ∀ {k}, m ≤ k * n → m / k ≤ n
+  | 0, _ => by simp [Nat.div_zero, n.zero_le]
+  | succ k, h => by
+    suffices succ k * (m / succ k) ≤ succ k * n from
+      Nat.le_of_mul_le_mul_left this (zero_lt_succ _)
+    have h1 : succ k * (m / succ k) ≤ m % succ k + succ k * (m / succ k) := Nat.le_add_left _ _
+    have h2 : m % succ k + succ k * (m / succ k) = m := by rw [mod_add_div]
+    have h3 : m ≤ succ k * n := h
+    rw [← h2] at h3
+    exact Nat.le_trans h1 h3
+
+@[simp] theorem mul_div_right (n : Nat) {m : Nat} (H : 0 < m) : m * n / m = n := by
+  induction n <;> simp_all [mul_succ]
+
+@[simp] theorem mul_div_left (m : Nat) {n : Nat} (H : 0 < n) : m * n / n = m := by
+  rw [Nat.mul_comm, mul_div_right _ H]
+
+protected theorem div_self (H : 0 < n) : n / n = 1 := by
+  let t := add_div_right 0 H
+  rwa [Nat.zero_add, Nat.zero_div] at t
+
+protected theorem div_eq_of_eq_mul_left (H1 : 0 < n) (H2 : m = k * n) : m / n = k :=
+by rw [H2, Nat.mul_div_cancel _ H1]
+
+protected theorem div_eq_of_eq_mul_right (H1 : 0 < n) (H2 : m = n * k) : m / n = k :=
+by rw [H2, Nat.mul_div_cancel_left _ H1]
+
+protected theorem mul_div_mul_left {m : Nat} (n k : Nat) (H : 0 < m) :
+    m * n / (m * k) = n / k := by rw [← Nat.div_div_eq_div_mul, Nat.mul_div_cancel_left _ H]
+
+protected theorem mul_div_mul_right {m : Nat} (n k : Nat) (H : 0 < m) :
+    n * m / (k * m) = n / k := by rw [Nat.mul_comm, Nat.mul_comm k, Nat.mul_div_mul_left _ _ H]
+
+theorem mul_div_le (m n : Nat) : n * (m / n) ≤ m := by
+  match n, Nat.eq_zero_or_pos n with
+  | _, Or.inl rfl => rw [Nat.zero_mul]; exact m.zero_le
+  | n, Or.inr h => rw [Nat.mul_comm, ← Nat.le_div_iff_mul_le h]; exact Nat.le_refl _
+
+
+end Nat

src/Init/Data/Nat/Div/Basic.lean

@@ -1,437 +0,0 @@
-/-
-Copyright (c) 2016 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-prelude
-import Init.WF
-import Init.WFTactics
-import Init.Data.Nat.Basic
-
-namespace Nat
-
-/--
-Divisibility of natural numbers. `a ∣ b` (typed as `\|`) says that
-there is some `c` such that `b = a * c`.
--/
-instance : Dvd Nat where
-  dvd a b := Exists (fun c => b = a * c)
-
-theorem div_rec_lemma {x y : Nat} : 0 < y ∧ y ≤ x → x - y < x :=
-  fun ⟨ypos, ylex⟩ => sub_lt (Nat.lt_of_lt_of_le ypos ylex) ypos
-
-@[extern "lean_nat_div"]
-protected def div (x y : @& Nat) : Nat :=
-  if 0 < y ∧ y ≤ x then
-    Nat.div (x - y) y + 1
-  else
-    0
-decreasing_by apply div_rec_lemma; assumption
-
-instance instDiv : Div Nat := ⟨Nat.div⟩
-
-theorem div_eq (x y : Nat) : x / y = if 0 < y ∧ y ≤ x then (x - y) / y + 1 else 0 := by
-  show Nat.div x y = _
-  rw [Nat.div]
-  rfl
-
-def div.inductionOn.{u}
-      {motive : Nat → Nat → Sort u}
-      (x y : Nat)
-      (ind  : ∀ x y, 0 < y ∧ y ≤ x → motive (x - y) y → motive x y)
-      (base : ∀ x y, ¬(0 < y ∧ y ≤ x) → motive x y)
-      : motive x y :=
-  if h : 0 < y ∧ y ≤ x then
-    ind x y h (inductionOn (x - y) y ind base)
-  else
-    base x y h
-decreasing_by apply div_rec_lemma; assumption
-
-theorem div_le_self (n k : Nat) : n / k ≤ n := by
-  induction n using Nat.strongRecOn with
-  | ind n ih =>
-    rw [div_eq]
-    -- Note: manual split to avoid Classical.em which is not yet defined
-    cases (inferInstance : Decidable (0 < k ∧ k ≤ n)) with
-    | isFalse h => simp [h]
-    | isTrue h =>
-      suffices (n - k) / k + 1 ≤ n by simp [h, this]
-      have ⟨hK, hKN⟩ := h
-      have hSub : n - k < n := sub_lt (Nat.lt_of_lt_of_le hK hKN) hK
-      have : (n - k) / k ≤ n - k := ih (n - k) hSub
-      exact succ_le_of_lt (Nat.lt_of_le_of_lt this hSub)
-
-theorem div_lt_self {n k : Nat} (hLtN : 0 < n) (hLtK : 1 < k) : n / k < n := by
-  rw [div_eq]
-  cases (inferInstance : Decidable (0 < k ∧ k ≤ n)) with
-  | isFalse h => simp [hLtN, h]
-  | isTrue h =>
-    suffices (n - k) / k + 1 < n by simp [h, this]
-    have ⟨_, hKN⟩ := h
-    have : (n - k) / k ≤ n - k := div_le_self (n - k) k
-    have := Nat.add_le_of_le_sub hKN this
-    exact Nat.lt_of_lt_of_le (Nat.add_lt_add_left hLtK _) this
-
-@[extern "lean_nat_mod"]
-protected def modCore (x y : @& Nat) : Nat :=
-  if 0 < y ∧ y ≤ x then
-    Nat.modCore (x - y) y
-  else
-    x
-decreasing_by apply div_rec_lemma; assumption
-
-@[extern "lean_nat_mod"]
-protected def mod : @& Nat → @& Nat → Nat
-  /-
-  Nat.modCore is defined by well-founded recursion and thus irreducible. Nevertheless it is
-  desirable if trivial `Nat.mod` calculations, namely
-  * `Nat.mod 0 m` for all `m`
-  * `Nat.mod n (m+n)` for concrete literals `n`
-  reduce definitionally.
-  This property is desirable for `Fin n` literals, as it means `(ofNat 0 : Fin n).val = 0` by
-  definition.
-   -/
-  | 0, _ => 0
-  | n@(_ + 1), m =>
-    if m ≤ n -- NB: if n < m does not reduce as well as `m ≤ n`!
-    then Nat.modCore n m
-    else n
-
-instance instMod : Mod Nat := ⟨Nat.mod⟩
-
-protected theorem modCore_eq_mod (n m : Nat) : Nat.modCore n m = n % m := by
-  show Nat.modCore n m = Nat.mod n m
-  match n, m with
-  | 0, _ =>
-    rw [Nat.modCore]
-    exact if_neg fun ⟨hlt, hle⟩ => Nat.lt_irrefl _ (Nat.lt_of_lt_of_le hlt hle)
-  | (_ + 1), _ =>
-    rw [Nat.mod]; dsimp
-    refine iteInduction (fun _ => rfl) (fun h => ?false) -- cannot use `split` this early yet
-    rw [Nat.modCore]
-    exact if_neg fun ⟨_hlt, hle⟩ => h hle
-
-theorem mod_eq (x y : Nat) : x % y = if 0 < y ∧ y ≤ x then (x - y) % y else x := by
-  rw [←Nat.modCore_eq_mod, ←Nat.modCore_eq_mod, Nat.modCore]
-
-def mod.inductionOn.{u}
-      {motive : Nat → Nat → Sort u}
-      (x y  : Nat)
-      (ind  : ∀ x y, 0 < y ∧ y ≤ x → motive (x - y) y → motive x y)
-      (base : ∀ x y, ¬(0 < y ∧ y ≤ x) → motive x y)
-      : motive x y :=
-  div.inductionOn x y ind base
-
-@[simp] theorem mod_zero (a : Nat) : a % 0 = a :=
-  have : (if 0 < 0 ∧ 0 ≤ a then (a - 0) % 0 else a) = a :=
-    have h : ¬ (0 < 0 ∧ 0 ≤ a) := fun ⟨h₁, _⟩ => absurd h₁ (Nat.lt_irrefl _)
-    if_neg h
-  (mod_eq a 0).symm ▸ this
-
-theorem mod_eq_of_lt {a b : Nat} (h : a < b) : a % b = a :=
-  have : (if 0 < b ∧ b ≤ a then (a - b) % b else a) = a :=
-    have h' : ¬(0 < b ∧ b ≤ a) := fun ⟨_, h₁⟩ => absurd h₁ (Nat.not_le_of_gt h)
-    if_neg h'
-  (mod_eq a b).symm ▸ this
-
-@[simp] theorem one_mod_eq_zero_iff {n : Nat} : 1 % n = 0 ↔ n = 1 := by
-  match n with
-  | 0 => simp
-  | 1 => simp
-  | n + 2 =>
-    rw [mod_eq_of_lt (by exact Nat.lt_of_sub_eq_succ rfl)]
-    simp only [add_one_ne_zero, false_iff, ne_eq]
-    exact ne_of_beq_eq_false rfl
-
-@[simp] theorem Nat.zero_eq_one_mod_iff {n : Nat} : 0 = 1 % n ↔ n = 1 := by
-  rw [eq_comm]
-  simp
-
-theorem mod_eq_sub_mod {a b : Nat} (h : a ≥ b) : a % b = (a - b) % b :=
-  match eq_zero_or_pos b with
-  | Or.inl h₁ => h₁.symm ▸ (Nat.sub_zero a).symm ▸ rfl
-  | Or.inr h₁ => (mod_eq a b).symm ▸ if_pos ⟨h₁, h⟩
-
-theorem mod_lt (x : Nat) {y : Nat} : y > 0 → x % y < y := by
-  induction x, y using mod.inductionOn with
-  | base x y h₁ =>
-    intro h₂
-    have h₁ : ¬ 0 < y ∨ ¬ y ≤ x := Decidable.not_and_iff_or_not.mp h₁
-    match h₁ with
-    | Or.inl h₁ => exact absurd h₂ h₁
-    | Or.inr h₁ =>
-      have hgt : y > x := gt_of_not_le h₁
-      have heq : x % y = x := mod_eq_of_lt hgt
-      rw [← heq] at hgt
-      exact hgt
-  | ind x y h h₂ =>
-    intro h₃
-    have ⟨_, h₁⟩ := h
-    rw [mod_eq_sub_mod h₁]
-    exact h₂ h₃
-
-@[simp] protected theorem sub_mod_add_mod_cancel (a b : Nat) [NeZero a] : a - b % a + b % a = a := by
-  rw [Nat.sub_add_cancel]
-  cases a with
-  | zero => simp_all
-  | succ a =>
-    exact Nat.le_of_lt (mod_lt b (zero_lt_succ a))
-
-theorem mod_le (x y : Nat) : x % y ≤ x := by
-  match Nat.lt_or_ge x y with
-  | Or.inl h₁ => rw [mod_eq_of_lt h₁]; apply Nat.le_refl
-  | Or.inr h₁ => match eq_zero_or_pos y with
-    | Or.inl h₂ => rw [h₂, Nat.mod_zero x]; apply Nat.le_refl
-    | Or.inr h₂ => exact Nat.le_trans (Nat.le_of_lt (mod_lt _ h₂)) h₁
-
-@[simp] theorem zero_mod (b : Nat) : 0 % b = 0 := by
-  rw [mod_eq]
-  have : ¬ (0 < b ∧ b = 0) := by
-    intro ⟨h₁, h₂⟩
-    simp_all
-  simp [this]
-
-@[simp] theorem mod_self (n : Nat) : n % n = 0 := by
-  rw [mod_eq_sub_mod (Nat.le_refl _), Nat.sub_self, zero_mod]
-
-theorem mod_one (x : Nat) : x % 1 = 0 := by
-  have h : x % 1 < 1 := mod_lt x (by decide)
-  have : (y : Nat) → y < 1 → y = 0 := by
-    intro y
-    cases y with
-    | zero   => intro _; rfl
-    | succ y => intro h; apply absurd (Nat.lt_of_succ_lt_succ h) (Nat.not_lt_zero y)
-  exact this _ h
-
-theorem div_add_mod (m n : Nat) : n * (m / n) + m % n = m := by
-  rw [div_eq, mod_eq]
-  have h : Decidable (0 < n ∧ n ≤ m) := inferInstance
-  cases h with
-  | isFalse h => simp [h]
-  | isTrue h =>
-    simp [h]
-    have ih := div_add_mod (m - n) n
-    rw [Nat.left_distrib, Nat.mul_one, Nat.add_assoc, Nat.add_left_comm, ih, Nat.add_comm, Nat.sub_add_cancel h.2]
-decreasing_by apply div_rec_lemma; assumption
-
-theorem div_eq_sub_div (h₁ : 0 < b) (h₂ : b ≤ a) : a / b = (a - b) / b + 1 := by
- rw [div_eq a, if_pos]; constructor <;> assumption
-
-theorem mod_add_div (m k : Nat) : m % k + k * (m / k) = m := by
-  induction m, k using mod.inductionOn with rw [div_eq, mod_eq]
-  | base x y h => simp [h]
-  | ind x y h IH => simp [h]; rw [Nat.mul_succ, ← Nat.add_assoc, IH, Nat.sub_add_cancel h.2]
-
-theorem mod_def (m k : Nat) : m % k = m - k * (m / k) := by
-  rw [Nat.sub_eq_of_eq_add]
-  apply (Nat.mod_add_div _ _).symm
-
-theorem mod_eq_sub_mul_div {x k : Nat} : x % k = x - k * (x / k) := mod_def _ _
-
-theorem mod_eq_sub_div_mul {x k : Nat} : x % k = x - (x / k) * k := by
-  rw [mod_eq_sub_mul_div, Nat.mul_comm]
-
-@[simp] protected theorem div_one (n : Nat) : n / 1 = n := by
-  have := mod_add_div n 1
-  rwa [mod_one, Nat.zero_add, Nat.one_mul] at this
-
-@[simp] protected theorem div_zero (n : Nat) : n / 0 = 0 := by
-  rw [div_eq]; simp [Nat.lt_irrefl]
-
-@[simp] protected theorem zero_div (b : Nat) : 0 / b = 0 :=
-  (div_eq 0 b).trans <| if_neg <| And.rec Nat.not_le_of_gt
-
-theorem le_div_iff_mul_le (k0 : 0 < k) : x ≤ y / k ↔ x * k ≤ y := by
-  induction y, k using mod.inductionOn generalizing x with
-    (rw [div_eq]; simp [h]; cases x with | zero => simp [zero_le] | succ x => ?_)
-  | base y k h =>
-    simp only [add_one, succ_mul, false_iff, Nat.not_le, Nat.succ_ne_zero]
-    refine Nat.lt_of_lt_of_le ?_ (Nat.le_add_left ..)
-    exact Nat.not_le.1 fun h' => h ⟨k0, h'⟩
-  | ind y k h IH =>
-    rw [Nat.add_le_add_iff_right, IH k0, succ_mul,
-        ← Nat.add_sub_cancel (x*k) k, Nat.sub_le_sub_iff_right h.2, Nat.add_sub_cancel]
-
-protected theorem div_div_eq_div_mul (m n k : Nat) : m / n / k = m / (n * k) := by
-  cases eq_zero_or_pos k with
-  | inl k0 => rw [k0, Nat.mul_zero, Nat.div_zero, Nat.div_zero] | inr kpos => ?_
-  cases eq_zero_or_pos n with
-  | inl n0 => rw [n0, Nat.zero_mul, Nat.div_zero, Nat.zero_div] | inr npos => ?_
-
-  apply Nat.le_antisymm
-
-  apply (le_div_iff_mul_le (Nat.mul_pos npos kpos)).2
-  rw [Nat.mul_comm n k, ← Nat.mul_assoc]
-  apply (le_div_iff_mul_le npos).1
-  apply (le_div_iff_mul_le kpos).1
-  (apply Nat.le_refl)
-
-  apply (le_div_iff_mul_le kpos).2
-  apply (le_div_iff_mul_le npos).2
-  rw [Nat.mul_assoc, Nat.mul_comm n k]
-  apply (le_div_iff_mul_le (Nat.mul_pos kpos npos)).1
-  apply Nat.le_refl
-
-theorem div_mul_le_self : ∀ (m n : Nat), m / n * n ≤ m
-  | m, 0   => by simp
-  | _, _+1 => (le_div_iff_mul_le (Nat.succ_pos _)).1 (Nat.le_refl _)
-
-theorem div_lt_iff_lt_mul (Hk : 0 < k) : x / k < y ↔ x < y * k := by
-  rw [← Nat.not_le, ← Nat.not_le]; exact not_congr (le_div_iff_mul_le Hk)
-
-theorem pos_of_div_pos {a b : Nat} (h : 0 < a / b) : 0 < a := by
-  cases b with
-  | zero => simp at h
-  | succ b =>
-    match a, h with
-    | 0, h => simp at h
-    | a + 1, _ => exact zero_lt_succ a
-
-@[simp] theorem add_div_right (x : Nat) {z : Nat} (H : 0 < z) : (x + z) / z = (x / z) + 1 := by
-  rw [div_eq_sub_div H (Nat.le_add_left _ _), Nat.add_sub_cancel]
-
-@[simp] theorem add_div_left (x : Nat) {z : Nat} (H : 0 < z) : (z + x) / z = (x / z) + 1 := by
-  rw [Nat.add_comm, add_div_right x H]
-
-theorem add_mul_div_left (x z : Nat) {y : Nat} (H : 0 < y) : (x + y * z) / y = x / y + z := by
-  induction z with
-  | zero => rw [Nat.mul_zero, Nat.add_zero, Nat.add_zero]
-  | succ z ih => rw [mul_succ, ← Nat.add_assoc, add_div_right _ H, ih]; rfl
-
-theorem add_mul_div_right (x y : Nat) {z : Nat} (H : 0 < z) : (x + y * z) / z = x / z + y := by
-  rw [Nat.mul_comm, add_mul_div_left _ _ H]
-
-@[simp] theorem add_mod_right (x z : Nat) : (x + z) % z = x % z := by
-  rw [mod_eq_sub_mod (Nat.le_add_left ..), Nat.add_sub_cancel]
-
-@[simp] theorem add_mod_left (x z : Nat) : (x + z) % x = z % x := by
-  rw [Nat.add_comm, add_mod_right]
-
-@[simp] theorem add_mul_mod_self_left (x y z : Nat) : (x + y * z) % y = x % y := by
-  match z with
-  | 0 => rw [Nat.mul_zero, Nat.add_zero]
-  | succ z => rw [mul_succ, ← Nat.add_assoc, add_mod_right, add_mul_mod_self_left (z := z)]
-
-@[simp] theorem mul_add_mod_self_left (a b c : Nat) : (a * b + c) % a = c % a := by
-  rw [Nat.add_comm, Nat.add_mul_mod_self_left]
-
-@[simp] theorem add_mul_mod_self_right (x y z : Nat) : (x + y * z) % z = x % z := by
-  rw [Nat.mul_comm, add_mul_mod_self_left]
-
-@[simp] theorem mul_add_mod_self_right (a b c : Nat) : (a * b + c) % b = c % b := by
-  rw [Nat.add_comm, Nat.add_mul_mod_self_right]
-
-@[simp] theorem mul_mod_right (m n : Nat) : (m * n) % m = 0 := by
-  rw [← Nat.zero_add (m * n), add_mul_mod_self_left, zero_mod]
-
-@[simp] theorem mul_mod_left (m n : Nat) : (m * n) % n = 0 := by
-  rw [Nat.mul_comm, mul_mod_right]
-
-protected theorem div_eq_of_lt_le (lo : k * n ≤ m) (hi : m < (k + 1) * n) : m / n = k :=
-have npos : 0 < n := (eq_zero_or_pos _).resolve_left fun hn => by
-  rw [hn, Nat.mul_zero] at hi lo; exact absurd lo (Nat.not_le_of_gt hi)
-Nat.le_antisymm
-  (le_of_lt_succ ((Nat.div_lt_iff_lt_mul npos).2 hi))
-  ((Nat.le_div_iff_mul_le npos).2 lo)
-
-theorem sub_mul_div (x n p : Nat) (h₁ : n*p ≤ x) : (x - n*p) / n = x / n - p := by
-  match eq_zero_or_pos n with
-  | .inl h₀ => rw [h₀, Nat.div_zero, Nat.div_zero, Nat.zero_sub]
-  | .inr h₀ => induction p with
-    | zero => rw [Nat.mul_zero, Nat.sub_zero, Nat.sub_zero]
-    | succ p IH =>
-      have h₂ : n * p ≤ x := Nat.le_trans (Nat.mul_le_mul_left _ (le_succ _)) h₁
-      have h₃ : x - n * p ≥ n := by
-        apply Nat.le_of_add_le_add_right
-        rw [Nat.sub_add_cancel h₂, Nat.add_comm]
-        rw [mul_succ] at h₁
-        exact h₁
-      rw [sub_succ, ← IH h₂, div_eq_sub_div h₀ h₃]
-      simp [Nat.pred_succ, mul_succ, Nat.sub_sub]
-
-theorem mul_sub_div (x n p : Nat) (h₁ : x < n*p) : (n * p - (x + 1)) / n = p - ((x / n) + 1) := by
-  have npos : 0 < n := (eq_zero_or_pos _).resolve_left fun n0 => by
-    rw [n0, Nat.zero_mul] at h₁; exact not_lt_zero _ h₁
-  apply Nat.div_eq_of_lt_le
-  focus
-    rw [Nat.mul_sub_right_distrib, Nat.mul_comm]
-    exact Nat.sub_le_sub_left ((div_lt_iff_lt_mul npos).1 (lt_succ_self _)) _
-  focus
-    show succ (pred (n * p - x)) ≤ (succ (pred (p - x / n))) * n
-    rw [succ_pred_eq_of_pos (Nat.sub_pos_of_lt h₁),
-      fun h => succ_pred_eq_of_pos (Nat.sub_pos_of_lt h)] -- TODO: why is the function needed?
-    focus
-      rw [Nat.mul_sub_right_distrib, Nat.mul_comm]
-      exact Nat.sub_le_sub_left (div_mul_le_self ..) _
-    focus
-      rwa [div_lt_iff_lt_mul npos, Nat.mul_comm]
-
-theorem mul_mod_mul_left (z x y : Nat) : (z * x) % (z * y) = z * (x % y) :=
-  if y0 : y = 0 then by
-    rw [y0, Nat.mul_zero, mod_zero, mod_zero]
-  else if z0 : z = 0 then by
-    rw [z0, Nat.zero_mul, Nat.zero_mul, Nat.zero_mul, mod_zero]
-  else by
-    induction x using Nat.strongRecOn with
-    | _ n IH =>
-      have y0 : y > 0 := Nat.pos_of_ne_zero y0
-      have z0 : z > 0 := Nat.pos_of_ne_zero z0
-      cases Nat.lt_or_ge n y with
-      | inl yn => rw [mod_eq_of_lt yn, mod_eq_of_lt (Nat.mul_lt_mul_of_pos_left yn z0)]
-      | inr yn =>
-        rw [mod_eq_sub_mod yn, mod_eq_sub_mod (Nat.mul_le_mul_left z yn),
-          ← Nat.mul_sub_left_distrib]
-        exact IH _ (sub_lt (Nat.lt_of_lt_of_le y0 yn) y0)
-
-theorem div_eq_of_lt (h₀ : a < b) : a / b = 0 := by
-  rw [div_eq a, if_neg]
-  intro h₁
-  apply Nat.not_le_of_gt h₀ h₁.right
-
-protected theorem mul_div_cancel (m : Nat) {n : Nat} (H : 0 < n) : m * n / n = m := by
-  let t := add_mul_div_right 0 m H
-  rwa [Nat.zero_add, Nat.zero_div, Nat.zero_add] at t
-
-protected theorem mul_div_cancel_left (m : Nat) {n : Nat} (H : 0 < n) : n * m / n = m := by
-  rw [Nat.mul_comm, Nat.mul_div_cancel _ H]
-
-protected theorem div_le_of_le_mul {m n : Nat} : ∀ {k}, m ≤ k * n → m / k ≤ n
-  | 0, _ => by simp [Nat.div_zero, n.zero_le]
-  | succ k, h => by
-    suffices succ k * (m / succ k) ≤ succ k * n from
-      Nat.le_of_mul_le_mul_left this (zero_lt_succ _)
-    have h1 : succ k * (m / succ k) ≤ m % succ k + succ k * (m / succ k) := Nat.le_add_left _ _
-    have h2 : m % succ k + succ k * (m / succ k) = m := by rw [mod_add_div]
-    have h3 : m ≤ succ k * n := h
-    rw [← h2] at h3
-    exact Nat.le_trans h1 h3
-
-@[simp] theorem mul_div_right (n : Nat) {m : Nat} (H : 0 < m) : m * n / m = n := by
-  induction n <;> simp_all [mul_succ]
-
-@[simp] theorem mul_div_left (m : Nat) {n : Nat} (H : 0 < n) : m * n / n = m := by
-  rw [Nat.mul_comm, mul_div_right _ H]
-
-protected theorem div_self (H : 0 < n) : n / n = 1 := by
-  let t := add_div_right 0 H
-  rwa [Nat.zero_add, Nat.zero_div] at t
-
-protected theorem div_eq_of_eq_mul_left (H1 : 0 < n) (H2 : m = k * n) : m / n = k :=
-by rw [H2, Nat.mul_div_cancel _ H1]
-
-protected theorem div_eq_of_eq_mul_right (H1 : 0 < n) (H2 : m = n * k) : m / n = k :=
-by rw [H2, Nat.mul_div_cancel_left _ H1]
-
-protected theorem mul_div_mul_left {m : Nat} (n k : Nat) (H : 0 < m) :
-    m * n / (m * k) = n / k := by rw [← Nat.div_div_eq_div_mul, Nat.mul_div_cancel_left _ H]
-
-protected theorem mul_div_mul_right {m : Nat} (n k : Nat) (H : 0 < m) :
-    n * m / (k * m) = n / k := by rw [Nat.mul_comm, Nat.mul_comm k, Nat.mul_div_mul_left _ _ H]
-
-theorem mul_div_le (m n : Nat) : n * (m / n) ≤ m := by
-  match n, Nat.eq_zero_or_pos n with
-  | _, Or.inl rfl => rw [Nat.zero_mul]; exact m.zero_le
-  | n, Or.inr h => rw [Nat.mul_comm, ← Nat.le_div_iff_mul_le h]; exact Nat.le_refl _
-
-
-end Nat

src/Init/Data/Nat/Div/Lemmas.lean

@@ -1,52 +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.Omega
-import Init.Data.Nat.Lemmas
-
-/-!
-# Further lemmas about `Nat.div` and `Nat.mod`, with the convenience of having `omega` available.
--/
-
-namespace Nat
-
-theorem lt_div_iff_mul_lt (h : 0 < k) : x < y / k ↔ x * k < y - (k - 1) := by
-  have t := le_div_iff_mul_le h (x := x + 1) (y := y)
-  rw [succ_le, add_one_mul] at t
-  have s : k = k - 1 + 1 := by omega
-  conv at t => rhs; lhs; rhs; rw [s]
-  rw [← Nat.add_assoc, succ_le, add_lt_iff_lt_sub_right] at t
-  exact t
-
-theorem div_le_iff_le_mul (h : 0 < k) : x / k ≤ y ↔ x ≤ y * k + k - 1 := by
-  rw [le_iff_lt_add_one, Nat.div_lt_iff_lt_mul h, Nat.add_one_mul]
-  omega
-
--- TODO: reprove `div_eq_of_lt_le` in terms of this:
-theorem div_eq_iff (h : 0 < k) : x / k = y ↔ x ≤ y * k + k - 1 ∧ y * k ≤ x := by
-  rw [Nat.eq_iff_le_and_ge, le_div_iff_mul_le h, Nat.div_le_iff_le_mul h]
-
-theorem lt_of_div_eq_zero (h : 0 < k) (h' : x / k = 0) : x < k := by
-  rw [div_eq_iff h] at h'
-  omega
-
-theorem div_eq_zero_iff_lt (h : 0 < k) : x / k = 0 ↔ x < k :=
-  ⟨lt_of_div_eq_zero h, fun h' => Nat.div_eq_of_lt h'⟩
-
-theorem div_mul_self_eq_mod_sub_self {x k : Nat} : (x / k) * k = x - (x % k) := by
-  have := mod_eq_sub_div_mul (x := x) (k := k)
-  have := div_mul_le_self x k
-  omega
-
-theorem mul_div_self_eq_mod_sub_self {x k : Nat} : k * (x / k) = x - (x % k) := by
-  rw [Nat.mul_comm, div_mul_self_eq_mod_sub_self]
-
-theorem lt_div_mul_self (h : 0 < k) (w : k ≤ x) : x - k < x / k * k := by
-  rw [div_mul_self_eq_mod_sub_self]
-  have : x % k < k := mod_lt x h
-  omega
-
-end Nat

src/Init/Data/Nat/Dvd.lean

@@ -4,7 +4,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Leonardo de Moura, Jeremy Avigad, Mario Carneiro
 -/
 prelude
-import Init.Data.Nat.Div.Basic
+import Init.Data.Nat.Div
 import Init.Meta
 
 namespace Nat
@@ -77,7 +77,7 @@ theorem dvd_of_mod_eq_zero {m n : Nat} (H : n % m = 0) : m ∣ n := by
 theorem dvd_iff_mod_eq_zero {m n : Nat} : m ∣ n ↔ n % m = 0 :=
   ⟨mod_eq_zero_of_dvd, dvd_of_mod_eq_zero⟩
 
-instance decidable_dvd : @DecidableRel Nat Nat (·∣·) :=
+instance decidable_dvd : @DecidableRel Nat (·∣·) :=
   fun _ _ => decidable_of_decidable_of_iff dvd_iff_mod_eq_zero.symm
 
 theorem emod_pos_of_not_dvd {a b : Nat} (h : ¬ a ∣ b) : 0 < b % a := by

src/Init/Data/Nat/Lemmas.lean

@@ -176,9 +176,6 @@ protected theorem add_pos_right (m) (h : 0 < n) : 0 < m + n :=
 protected theorem add_self_ne_one : ∀ n, n + n ≠ 1
   | n+1, h => by rw [Nat.succ_add, Nat.succ.injEq] at h; contradiction
 
-theorem le_iff_lt_add_one : x ≤ y ↔ x < y + 1 := by
-  omega
-
 /-! ## sub -/
 
 protected theorem sub_one (n) : n - 1 = pred n := rfl
@@ -228,9 +225,6 @@ protected theorem sub_le_iff_le_add' {a b c : Nat} : a - b ≤ c ↔ a ≤ b + c
 protected theorem le_sub_iff_add_le {n : Nat} (h : k ≤ m) : n ≤ m - k ↔ n + k ≤ m :=
   ⟨Nat.add_le_of_le_sub h, Nat.le_sub_of_add_le⟩
 
-theorem add_lt_iff_lt_sub_right {a b c : Nat} : a + b < c ↔ a < c - b := by
-  omega
-
 protected theorem add_le_of_le_sub' {n k m : Nat} (h : m ≤ k) : n ≤ k - m → m + n ≤ k :=
   Nat.add_comm .. ▸ Nat.add_le_of_le_sub h
 

src/Init/Data/OfScientific.lean

@@ -6,7 +6,6 @@ Authors: Leonardo de Moura
 prelude
 import Init.Meta
 import Init.Data.Float
-import Init.Data.Float32
 import Init.Data.Nat.Log2
 
 /-- For decimal and scientific numbers (e.g., `1.23`, `3.12e10`).
@@ -57,34 +56,3 @@ instance : OfNat Float n   := ⟨Float.ofNat n⟩
 
 abbrev Nat.toFloat (n : Nat) : Float :=
   Float.ofNat n
-
-/-- Computes `m * 2^e`. -/
-def Float32.ofBinaryScientific (m : Nat) (e : Int) : Float32 :=
-  let s := m.log2 - 63
-  let m := (m >>> s).toUInt64
-  let e := e + s
-  m.toFloat32.scaleB e
-
-protected opaque Float32.ofScientific (m : Nat) (s : Bool) (e : Nat) : Float32 :=
-  if s then
-    let s := 64 - m.log2 -- ensure we have 64 bits of mantissa left after division
-    let m := (m <<< (3 * e + s)) / 5^e
-    Float32.ofBinaryScientific m (-4 * e - s)
-  else
-    Float32.ofBinaryScientific (m * 5^e) e
-
-instance : OfScientific Float32 where
-  ofScientific := Float32.ofScientific
-
-@[export lean_float32_of_nat]
-def Float32.ofNat (n : Nat) : Float32 :=
-  OfScientific.ofScientific n false 0
-
-def Float32.ofInt : Int → Float
-  | Int.ofNat n => Float.ofNat n
-  | Int.negSucc n => Float.neg (Float.ofNat (Nat.succ n))
-
-instance : OfNat Float32 n   := ⟨Float32.ofNat n⟩
-
-abbrev Nat.toFloat32 (n : Nat) : Float32 :=
-  Float32.ofNat n

src/Init/Data/Option/Attach.lean

@@ -56,6 +56,7 @@ theorem attach_map_val (o : Option α) (f : α → β) :
     (o.attach.map fun i => f i.val) = o.map f :=
   attach_map_coe _ _
 
+@[simp]
 theorem attach_map_subtype_val (o : Option α) :
     o.attach.map Subtype.val = o :=
   (attach_map_coe _ _).trans (congrFun Option.map_id _)
@@ -68,11 +69,12 @@ theorem attachWith_map_val {p : α → Prop} (f : α → β) (o : Option α) (H
     ((o.attachWith p H).map fun i => f i.val) = o.map f :=
   attachWith_map_coe _ _ _
 
+@[simp]
 theorem attachWith_map_subtype_val {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
     (o.attachWith p H).map Subtype.val = o :=
   (attachWith_map_coe _ _ _).trans (congrFun Option.map_id _)
 
-theorem mem_attach : ∀ (o : Option α) (x : {x // x ∈ o}), x ∈ o.attach
+@[simp] theorem mem_attach : ∀ (o : Option α) (x : {x // x ∈ o}), x ∈ o.attach
   | none, ⟨x, h⟩ => by simp at h
   | some a, ⟨x, h⟩ => by simpa using h
 
@@ -90,14 +92,14 @@ theorem mem_attach : ∀ (o : Option α) (x : {x // x ∈ o}), x ∈ o.attach
     (o.attachWith p H).isSome = o.isSome := by
   cases o <;> simp
 
-@[simp] theorem attach_eq_none_iff {o : Option α} : o.attach = none ↔ o = none := by
+@[simp] theorem attach_eq_none_iff (o : Option α) : o.attach = none ↔ o = none := by
   cases o <;> simp
 
 @[simp] theorem attach_eq_some_iff {o : Option α} {x : {x // x ∈ o}} :
     o.attach = some x ↔ o = some x.val := by
   cases o <;> cases x <;> simp
 
-@[simp] theorem attachWith_eq_none_iff {p : α → Prop} {o : Option α} (H : ∀ a ∈ o, p a) :
+@[simp] theorem attachWith_eq_none_iff {p : α → Prop} (o : Option α) (H : ∀ a ∈ o, p a) :
     o.attachWith p H = none ↔ o = none := by
   cases o <;> simp
 

src/Init/Data/Option/Basic.lean

@@ -96,12 +96,12 @@ This is similar to `<|>`/`orElse`, but it is strict in the second argument. -/
   | some a, _ => some a
   | none,   b => b
 
-@[inline] protected def lt (r : α → β → Prop) : Option α → Option β → Prop
+@[inline] protected def lt (r : α → α → Prop) : Option α → Option α → Prop
   | none, some _     => True
   | some x,   some y => r x y
   | _, _             => False
 
-instance (r : α → β → Prop) [s : DecidableRel r] : DecidableRel (Option.lt r)
+instance (r : α → α → Prop) [s : DecidableRel r] : DecidableRel (Option.lt r)
   | none,   some _ => isTrue  trivial
   | some x, some y => s x y
   | some _, none   => isFalse not_false

src/Init/Data/Option/Monadic.lean

@@ -10,17 +10,7 @@ import Init.Control.Lawful.Basic
 
 namespace Option
 
-@[simp] theorem forM_none [Monad m] (f : α → m PUnit) :
-    none.forM f = pure .unit := rfl
-
-@[simp] theorem forM_some [Monad m] (f : α → m PUnit) (a : α) :
-    (some a).forM f = f a := rfl
-
-@[simp] theorem forM_map [Monad m] [LawfulMonad m] (o : Option α) (g : α → β) (f : β → m PUnit) :
-    (o.map g).forM f = o.forM (fun a => f (g a)) := by
-  cases o <;> simp
-
-@[congr] theorem forIn'_congr [Monad m] [LawfulMonad m] {as bs : Option α} (w : as = bs)
+@[congr] theorem forIn'_congr [Monad m] [LawfulMonad m]{as bs : Option α} (w : as = bs)
     {b b' : β} (hb : b = b')
     {f : (a' : α) → a' ∈ as → β → m (ForInStep β)}
     {g : (a' : α) → a' ∈ bs → β → m (ForInStep β)}
@@ -58,11 +48,6 @@ theorem forIn'_pure_yield_eq_pelim [Monad m] [LawfulMonad m]
       o.pelim b (fun a h => f a h b) := by
   cases o <;> simp
 
-@[simp] theorem forIn'_map [Monad m] [LawfulMonad m]
-    (o : Option α) (g : α → β) (f : (b : β) → b ∈ o.map g → γ → m (ForInStep γ)) :
-    forIn' (o.map g) init f = forIn' o init fun a h y => f (g a) (mem_map_of_mem g h) y := by
-  cases o <;> simp
-
 theorem forIn_eq_elim [Monad m] [LawfulMonad m]
     (o : Option α) (f : (a : α) → β → m (ForInStep β)) (b : β) :
     forIn o b f =
@@ -87,9 +72,4 @@ theorem forIn_pure_yield_eq_elim [Monad m] [LawfulMonad m]
       o.elim b (fun a => f a b) := by
   cases o <;> simp
 
-@[simp] theorem forIn_map [Monad m] [LawfulMonad m]
-    (o : Option α) (g : α → β) (f : β → γ → m (ForInStep γ)) :
-    forIn (o.map g) init f = forIn o init fun a y => f (g a) y := by
-  cases o <;> simp
-
 end Option

src/Init/Data/Ord.lean

@@ -210,18 +210,12 @@ Derive an `LT` instance from an `Ord` instance.
 protected def toLT (_ : Ord α) : LT α :=
   ltOfOrd
 
-instance [i : Ord α] : DecidableRel (@LT.lt _ (Ord.toLT i)) :=
-  inferInstanceAs (DecidableRel (fun a b => compare a b = Ordering.lt))
-
 /--
 Derive an `LE` instance from an `Ord` instance.
 -/
 protected def toLE (_ : Ord α) : LE α :=
   leOfOrd
 
-instance [i : Ord α] : DecidableRel (@LE.le _ (Ord.toLE i)) :=
-  inferInstanceAs (DecidableRel (fun a b => (compare a b).isLE))
-
 /--
 Invert the order of an `Ord` instance.
 -/
@@ -254,6 +248,6 @@ protected def arrayOrd [a : Ord α] : Ord (Array α) where
   compare x y :=
     let _ : LT α := a.toLT
     let _ : BEq α := a.toBEq
-    if List.lex x.toList y.toList then .lt else if x == y then .eq else .gt
+    compareOfLessAndBEq x.toList y.toList
 
 end Ord

src/Init/Data/Range.lean

@@ -1,8 +1,74 @@
 /-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
+Copyright (c) 2020 Microsoft Corporation. All rights reserved.
 Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
+Authors: Leonardo de Moura
 -/
 prelude
-import Init.Data.Range.Basic
-import Init.Data.Range.Lemmas
+import Init.Meta
+
+namespace Std
+-- We put `Range` in `Init` because we want the notation `[i:j]`  without importing `Std`
+-- We don't put `Range` in the top-level namespace to avoid collisions with user defined types
+structure Range where
+  start : Nat := 0
+  stop  : Nat
+  step  : Nat := 1
+
+instance : Membership Nat Range where
+  mem r i := r.start ≤ i ∧ i < r.stop
+
+namespace Range
+universe u v
+
+@[inline] protected def forIn' {β : Type u} {m : Type u → Type v} [Monad m] (range : Range) (init : β) (f : (i : Nat) → i ∈ range → β → m (ForInStep β)) : m β :=
+  let rec @[specialize] loop (start stop step : Nat) (f : (i : Nat) → start ≤ i ∧ i < stop → β → m (ForInStep β)) (fuel i : Nat) (hl : start ≤ i) (b : β) : m β := do
+    if hu : i < stop then
+      match fuel with
+      | 0   => pure b
+      | fuel+1 => match (← f i ⟨hl, hu⟩ b) with
+         | ForInStep.done b  => pure b
+         | ForInStep.yield b => loop start stop step f fuel (i + step) (Nat.le_trans hl (Nat.le_add_right ..)) b
+    else
+      return b
+  loop range.start range.stop range.step f range.stop range.start (Nat.le_refl ..) init
+
+instance : ForIn' m Range Nat inferInstance where
+  forIn' := Range.forIn'
+
+-- No separate `ForIn` instance is required because it can be derived from `ForIn'`.
+
+@[inline] protected def forM {m : Type u → Type v} [Monad m] (range : Range) (f : Nat → m PUnit) : m PUnit :=
+  let rec @[specialize] loop (fuel i stop step : Nat) : m PUnit := do
+    if i ≥ stop then
+      pure ⟨⟩
+    else match fuel with
+     | 0   => pure ⟨⟩
+     | fuel+1 => f i; loop fuel (i + step) stop step
+  loop range.stop range.start range.stop range.step
+
+instance : ForM m Range Nat where
+  forM := Range.forM
+
+syntax:max "[" withoutPosition(":" term) "]" : term
+syntax:max "[" withoutPosition(term ":" term) "]" : term
+syntax:max "[" withoutPosition(":" term ":" term) "]" : term
+syntax:max "[" withoutPosition(term ":" term ":" term) "]" : term
+
+macro_rules
+  | `([ : $stop]) => `({ stop := $stop : Range })
+  | `([ $start : $stop ]) => `({ start := $start, stop := $stop : Range })
+  | `([ $start : $stop : $step ]) => `({ start := $start, stop := $stop, step := $step : Range })
+  | `([ : $stop : $step ]) => `({ stop := $stop, step := $step : Range })
+
+end Range
+end Std
+
+theorem Membership.mem.upper {i : Nat} {r : Std.Range} (h : i ∈ r) : i < r.stop := h.2
+
+theorem Membership.mem.lower {i : Nat} {r : Std.Range} (h : i ∈ r) : r.start ≤ i := h.1
+
+theorem Membership.get_elem_helper {i n : Nat} {r : Std.Range} (h₁ : i ∈ r) (h₂ : r.stop = n) :
+    i < n := h₂ ▸ h₁.2
+
+macro_rules
+  | `(tactic| get_elem_tactic_trivial) => `(tactic| apply Membership.get_elem_helper; assumption; rfl)

src/Init/Data/Range/Basic.lean

@@ -1,86 +0,0 @@
-/-
-Copyright (c) 2020 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-prelude
-import Init.Meta
-import Init.Omega
-
-namespace Std
--- We put `Range` in `Init` because we want the notation `[i:j]`  without importing `Std`
--- We don't put `Range` in the top-level namespace to avoid collisions with user defined types
-structure Range where
-  start : Nat := 0
-  stop  : Nat
-  step  : Nat := 1
-  step_pos : 0 < step
-
-instance : Membership Nat Range where
-  mem r i := r.start ≤ i ∧ i < r.stop ∧ (i - r.start) % r.step = 0
-
-namespace Range
-universe u v
-
-/-- The number of elements in the range. -/
-@[simp] def size (r : Range) : Nat := (r.stop - r.start + r.step - 1) / r.step
-
-@[inline] protected def forIn' [Monad m] (range : Range) (init : β)
-    (f : (i : Nat) → i ∈ range → β → m (ForInStep β)) : m β :=
-  let rec @[specialize] loop (b : β) (i : Nat)
-      (hs : (i - range.start) % range.step = 0) (hl : range.start ≤ i := by omega) : m β := do
-    if h : i < range.stop then
-      match (← f i ⟨hl, by omega, hs⟩ b) with
-      | .done b  => pure b
-      | .yield b =>
-        have := range.step_pos
-        loop b (i + range.step) (by rwa [Nat.add_comm, Nat.add_sub_assoc hl, Nat.add_mod_left])
-    else
-      pure b
-  have := range.step_pos
-  loop init range.start (by simp)
-
-instance : ForIn' m Range Nat inferInstance where
-  forIn' := Range.forIn'
-
--- No separate `ForIn` instance is required because it can be derived from `ForIn'`.
-
-@[inline] protected def forM [Monad m] (range : Range) (f : Nat → m PUnit) : m PUnit :=
-  let rec @[specialize] loop (i : Nat): m PUnit := do
-    if i < range.stop then
-      f i
-      have := range.step_pos
-      loop (i + range.step)
-    else
-      pure ⟨⟩
-  have := range.step_pos
-  loop range.start
-
-instance : ForM m Range Nat where
-  forM := Range.forM
-
-syntax:max "[" withoutPosition(":" term) "]" : term
-syntax:max "[" withoutPosition(term ":" term) "]" : term
-syntax:max "[" withoutPosition(":" term ":" term) "]" : term
-syntax:max "[" withoutPosition(term ":" term ":" term) "]" : term
-
-macro_rules
-  | `([ : $stop]) => `({ stop := $stop, step_pos := Nat.zero_lt_one : Range })
-  | `([ $start : $stop ]) => `({ start := $start, stop := $stop, step_pos := Nat.zero_lt_one : Range })
-  | `([ $start : $stop : $step ]) => `({ start := $start, stop := $stop, step := $step, step_pos := by decide : Range })
-  | `([ : $stop : $step ]) => `({ stop := $stop, step := $step, step_pos := by decide : Range })
-
-end Range
-end Std
-
-theorem Membership.mem.upper {i : Nat} {r : Std.Range} (h : i ∈ r) : i < r.stop := h.2.1
-
-theorem Membership.mem.lower {i : Nat} {r : Std.Range} (h : i ∈ r) : r.start ≤ i := h.1
-
-theorem Membership.mem.step {i : Nat} {r : Std.Range} (h : i ∈ r) : (i - r.start) % r.step = 0 := h.2.2
-
-theorem Membership.get_elem_helper {i n : Nat} {r : Std.Range} (h₁ : i ∈ r) (h₂ : r.stop = n) :
-    i < n := h₂ ▸ h₁.2.1
-
-macro_rules
-  | `(tactic| get_elem_tactic_trivial) => `(tactic| apply Membership.get_elem_helper; assumption; rfl)

src/Init/Data/Range/Lemmas.lean

@@ -1,103 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
--/
-prelude
-import Init.Data.Range.Basic
-import Init.Data.List.Range
-import Init.Data.List.Monadic
-import Init.Data.Nat.Div.Lemmas
-
-/-!
-# Lemmas about `Std.Range`
-
-We provide lemmas rewriting for loops over `Std.Range` in terms of `List.range'`.
--/
-
-namespace Std.Range
-
-/-- Generalization of `mem_of_mem_range'` used in `forIn'_loop_eq_forIn'_range'` below. -/
-private theorem mem_of_mem_range'_aux {r : Range} {a : Nat} (w₁ : (i - r.start) % r.step = 0)
-    (w₂ : r.start ≤ i)
-    (h : a ∈ List.range' i ((r.stop - i + r.step - 1) / r.step) r.step) : a ∈ r := by
-  obtain ⟨j, h', rfl⟩ := List.mem_range'.1 h
-  refine ⟨by omega, ?_⟩
-  rw [Nat.lt_div_iff_mul_lt r.step_pos, Nat.mul_comm] at h'
-  constructor
-  · omega
-  · rwa [Nat.add_comm, Nat.add_sub_assoc w₂, Nat.mul_add_mod_self_left]
-
-theorem mem_of_mem_range' {r : Range} (h : x ∈ List.range' r.start r.size r.step) : x ∈ r := by
-  unfold size at h
-  apply mem_of_mem_range'_aux (by simp) (by simp) h
-
-private theorem size_eq (r : Std.Range) (h : i < r.stop) :
-    (r.stop - i + r.step - 1) / r.step =
-      (r.stop - (i + r.step) + r.step - 1) / r.step + 1 := by
-  have w := r.step_pos
-  if i + r.step < r.stop then -- Not sure this case split is strictly necessary.
-    rw [Nat.div_eq_iff w, Nat.add_one_mul]
-    have : (r.stop - (i + r.step) + r.step - 1) / r.step * r.step ≤
-        (r.stop - (i + r.step) + r.step - 1) := Nat.div_mul_le_self _ _
-    have : r.stop - (i + r.step) + r.step - 1 - r.step <
-        (r.stop - (i + r.step) + r.step - 1) / r.step * r.step :=
-      Nat.lt_div_mul_self w (by omega)
-    omega
-  else
-    have : (r.stop - i + r.step - 1) / r.step = 1 := by
-      rw [Nat.div_eq_iff w, Nat.one_mul]
-      omega
-    have : (r.stop - (i + r.step) + r.step - 1) / r.step = 0 := by
-      rw [Nat.div_eq_iff] <;> omega
-    omega
-
-private theorem forIn'_loop_eq_forIn'_range' [Monad m] (r : Std.Range)
-    (init : β) (f : (a : Nat) → a ∈ r → β → m (ForInStep β)) (i) (w₁) (w₂) :
-    forIn'.loop r f init i w₁ w₂ =
-      forIn' (List.range' i ((r.stop - i + r.step - 1) / r.step) r.step) init
-        fun a h => f a (mem_of_mem_range'_aux w₁ w₂ h) := by
-  have w := r.step_pos
-  rw [forIn'.loop]
-  split <;> rename_i h
-  · simp only [size_eq r h, List.range'_succ, List.forIn'_cons]
-    congr 1
-    funext step
-    split
-    · simp
-    · rw [forIn'_loop_eq_forIn'_range']
-  · have : (r.stop - i + r.step - 1) / r.step = 0 := by
-      rw [Nat.div_eq_iff] <;> omega
-    simp [this]
-
-@[simp] theorem forIn'_eq_forIn'_range' [Monad m] (r : Std.Range)
-    (init : β) (f : (a : Nat) → a ∈ r → β → m (ForInStep β)) :
-    forIn' r init f =
-      forIn' (List.range' r.start r.size r.step) init (fun a h => f a (mem_of_mem_range' h)) := by
-  conv => lhs; simp only [forIn', Range.forIn']
-  simp only [size]
-  rw [forIn'_loop_eq_forIn'_range']
-
-@[simp] theorem forIn_eq_forIn_range' [Monad m] (r : Std.Range)
-    (init : β) (f : Nat → β → m (ForInStep β)) :
-    forIn r init f = forIn (List.range' r.start r.size r.step) init f := by
-  simp only [forIn, forIn'_eq_forIn'_range']
-
-private theorem forM_loop_eq_forM_range' [Monad m] (r : Std.Range) (f : Nat → m PUnit) :
-    forM.loop r f i = forM (List.range' i ((r.stop - i + r.step - 1) / r.step) r.step) f := by
-  have w := r.step_pos
-  rw [forM.loop]
-  split <;> rename_i h
-  · simp [size_eq r h, List.range'_succ, List.forM_cons]
-    congr 1
-    funext
-    rw [forM_loop_eq_forM_range']
-  · have : (r.stop - i + r.step - 1) / r.step = 0 := by
-      rw [Nat.div_eq_iff] <;> omega
-    simp [this]
-
-@[simp] theorem forM_eq_forM_range' [Monad m] (r : Std.Range) (f : Nat → m PUnit) :
-    forM r f = forM (List.range' r.start r.size r.step) f := by
-  simp only [forM, Range.forM, forM_loop_eq_forM_range', size]
-
-end Std.Range

src/Init/Data/String/Basic.lean

@@ -21,10 +21,8 @@ instance : LT String :=
   ⟨fun s₁ s₂ => s₁.data < s₂.data⟩
 
 @[extern "lean_string_dec_lt"]
-instance decidableLT (s₁ s₂ : @& String) : Decidable (s₁ < s₂) :=
-  List.decidableLT s₁.data s₂.data
-
-@[deprecated decidableLT (since := "2024-12-13")] abbrev decLt := @decidableLT
+instance decLt (s₁ s₂ : @& String) : Decidable (s₁ < s₂) :=
+  List.hasDecidableLt s₁.data s₂.data
 
 @[reducible] protected def le (a b : String) : Prop := ¬ b < a
 

src/Init/Data/String/Lemmas.lean

@@ -5,7 +5,6 @@ Authors: Leonardo de Moura
 -/
 prelude
 import Init.Data.Char.Lemmas
-import Init.Data.List.Lex
 
 namespace String
 
@@ -13,39 +12,10 @@ protected theorem data_eq_of_eq {a b : String} (h : a = b) : a.data = b.data :=
   h ▸ rfl
 protected theorem ne_of_data_ne {a b : String} (h : a.data ≠ b.data) : a ≠ b :=
   fun h' => absurd (String.data_eq_of_eq h') h
-
-@[simp] protected theorem not_le {a b : String} : ¬ a ≤ b ↔ b < a := Decidable.not_not
-@[simp] protected theorem not_lt {a b : String} : ¬ a < b ↔ b ≤ a := Iff.rfl
-@[simp] protected theorem le_refl (a : String) : a ≤ a := List.le_refl _
-@[simp] protected theorem lt_irrefl (a : String) : ¬ a < a := List.lt_irrefl _
-
-attribute [local instance] Char.notLTTrans Char.notLTAntisymm Char.notLTTotal
-
-protected theorem le_trans {a b c : String} : a ≤ b → b ≤ c → a ≤ c := List.le_trans
-protected theorem lt_trans {a b c : String} : a < b → b < c → a < c := List.lt_trans
-protected theorem le_total (a b : String) : a ≤ b ∨ b ≤ a := List.le_total
-protected theorem le_antisymm {a b : String} : a ≤ b → b ≤ a → a = b := fun h₁ h₂ => String.ext (List.le_antisymm (as := a.data) (bs := b.data) h₁ h₂)
-protected theorem lt_asymm {a b : String} (h : a < b) : ¬ b < a := List.lt_asymm h
+@[simp] protected theorem lt_irrefl (s : String) : ¬ s < s :=
+  List.lt_irrefl Char.lt_irrefl s.data
 protected theorem ne_of_lt {a b : String} (h : a < b) : a ≠ b := by
   have := String.lt_irrefl a
   intro h; subst h; contradiction
 
-instance ltIrrefl : Std.Irrefl (· < · : Char → Char → Prop) where
-  irrefl := Char.lt_irrefl
-
-instance leRefl : Std.Refl (· ≤ · : Char → Char → Prop) where
-  refl := Char.le_refl
-
-instance leTrans : Trans (· ≤ · : Char → Char → Prop) (· ≤ ·) (· ≤ ·) where
-  trans := Char.le_trans
-
-instance leAntisymm : Std.Antisymm (· ≤ · : Char → Char → Prop) where
-  antisymm _ _ := Char.le_antisymm
-
-instance ltAsymm : Std.Asymm (· < · : Char → Char → Prop) where
-  asymm _ _ := Char.lt_asymm
-
-instance leTotal : Std.Total (· ≤ · : Char → Char → Prop) where
-  total := Char.le_total
-
 end String

src/Init/Data/Sum/Lemmas.lean

@@ -30,7 +30,7 @@ protected theorem «exists» {p : α ⊕ β → Prop} :
     | Or.inl ⟨a, h⟩ => ⟨inl a, h⟩
     | Or.inr ⟨b, h⟩ => ⟨inr b, h⟩⟩
 
-theorem forall_sum {γ : α ⊕ β → Sort _} {p : (∀ ab, γ ab) → Prop} :
+theorem forall_sum {γ : α ⊕ β → Sort _} (p : (∀ ab, γ ab) → Prop) :
     (∀ fab, p fab) ↔ (∀ fa fb, p (Sum.rec fa fb)) := by
   refine ⟨fun h fa fb => h _, fun h fab => ?_⟩
   have h1 : fab = Sum.rec (fun a => fab (Sum.inl a)) (fun b => fab (Sum.inr b)) := by

src/Init/Data/Vector/Basic.lean

@@ -6,7 +6,6 @@ Authors: Shreyas Srinivas, François G. Dorais, Kim Morrison
 
 prelude
 import Init.Data.Array.Lemmas
-import Init.Data.Range
 
 /-!
 # Vectors
@@ -71,16 +70,6 @@ instance [Inhabited α] : Inhabited (Vector α n) where
 instance : GetElem (Vector α n) Nat α fun _ i => i < n where
   getElem x i h := get x ⟨i, h⟩
 
-/-- Check if there is an element which satisfies `a == ·`. -/
-def contains [BEq α] (v : Vector α n) (a : α) : Bool := v.toArray.contains a
-
-/-- `a ∈ v` is a predicate which asserts that `a` is in the vector `v`. -/
-structure Mem (as : Vector α n) (a : α) : Prop where
-  val : a ∈ as.toArray
-
-instance : Membership α (Vector α n) where
-  mem := Mem
-
 /--
 Get an element of a vector using a `Nat` index. Returns the given default value if the index is out
 of bounds.
@@ -265,39 +254,3 @@ no element of the index matches the given value.
 /-- 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
-
-/-- Returns `true` with the monad if `p` returns `true` for any element of the vector. -/
-@[inline] def anyM [Monad m] (p : α → m Bool) (v : Vector α n) : m Bool :=
-  v.toArray.anyM p
-
-/-- Returns `true` with the monad if `p` returns `true` for all elements of the vector. -/
-@[inline] def allM [Monad m] (p : α → m Bool) (v : Vector α n) : m Bool :=
-  v.toArray.allM p
-
-/-- Returns `true` if `p` returns `true` for any element of the vector. -/
-@[inline] def any (v : Vector α n) (p : α → Bool) : Bool :=
-  v.toArray.any p
-
-/-- Returns `true` if `p` returns `true` for all elements of the vector. -/
-@[inline] def all (v : Vector α n) (p : α → Bool) : Bool :=
-  v.toArray.all p
-
-/-! ### Lexicographic ordering -/
-
-instance instLT [LT α] : LT (Vector α n) := ⟨fun v w => v.toArray < w.toArray⟩
-instance instLE [LT α] : LE (Vector α n) := ⟨fun v w => v.toArray ≤ w.toArray⟩
-
-/--
-Lexicographic comparator for vectors.
-
-`lex v w lt` is true if
-- `v` is pairwise equivalent via `==` to `w`, or
-- there is an index `i` such that `lt v[i] w[i]`, and for all `j < i`, `v[j] == w[j]`.
--/
-def lex [BEq α] (v w : Vector α n) (lt : α → α → Bool := by exact (· < ·)) : Bool := Id.run do
-  for h : i in [0 : n] do
-    if lt v[i] w[i] then
-      return true
-    else if v[i] != w[i] then
-      return false
-  return false

src/Init/Data/Vector/Lex.lean

@@ -1,202 +0,0 @@
-/-
-Copyright (c) 2024 Lean FRO, LLC. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Kim Morrison
--/
-prelude
-import Init.Data.Vector.Basic
-import Init.Data.Vector.Lemmas
-import Init.Data.Array.Lex.Lemmas
-
-namespace Vector
-
-
-/-! ### Lexicographic ordering -/
-
-@[simp] theorem lt_toArray [LT α] (l₁ l₂ : Vector α n) : l₁.toArray < l₂.toArray ↔ l₁ < l₂ := Iff.rfl
-@[simp] theorem le_toArray [LT α] (l₁ l₂ : Vector α n) : l₁.toArray ≤ l₂.toArray ↔ l₁ ≤ l₂ := Iff.rfl
-
-@[simp] theorem lt_toList [LT α] (l₁ l₂ : Vector α n) : l₁.toList < l₂.toList ↔ l₁ < l₂ := Iff.rfl
-@[simp] theorem le_toList [LT α] (l₁ l₂ : Vector α n) : l₁.toList ≤ l₂.toList ↔ l₁ ≤ l₂ := Iff.rfl
-
-@[simp] theorem mk_lt_mk [LT α] :
-    Vector.mk (α := α) (n := n) data₁ size₁ < Vector.mk data₂ size₂ ↔ data₁ < data₂ := Iff.rfl
-
-@[simp] theorem mk_le_mk [LT α] :
-    Vector.mk (α := α) (n := n) data₁ size₁ ≤ Vector.mk data₂ size₂ ↔ data₁ ≤ data₂ := Iff.rfl
-
-@[simp] theorem mk_lex_mk [BEq α] (lt : α → α → Bool) {l₁ l₂ : Array α} {n₁ : l₁.size = n} {n₂ : l₂.size = n} :
-    (Vector.mk l₁ n₁).lex (Vector.mk l₂ n₂) lt = l₁.lex l₂ lt := by
-  simp [Vector.lex, Array.lex, n₁, n₂]
-  rfl
-
-@[simp] theorem lex_toArray [BEq α] (lt : α → α → Bool) (l₁ l₂ : Vector α n) :
-    l₁.toArray.lex l₂.toArray lt = l₁.lex l₂ lt := by
-  cases l₁
-  cases l₂
-  simp
-
-@[simp] theorem lex_toList [BEq α] (lt : α → α → Bool) (l₁ l₂ : Vector α n) :
-    l₁.toList.lex l₂.toList lt = l₁.lex l₂ lt := by
-  rcases l₁ with ⟨⟨l₁⟩, n₁⟩
-  rcases l₂ with ⟨⟨l₂⟩, n₂⟩
-  simp
-
-@[simp] theorem lex_empty
-    [BEq α] {lt : α → α → Bool} (l₁ : Vector α 0) : l₁.lex #v[] lt = false := by
-  cases l₁
-  simp_all
-
-@[simp] theorem singleton_lex_singleton [BEq α] {lt : α → α → Bool} : #v[a].lex #v[b] lt = lt a b := by
-  simp only [lex, getElem_mk, List.getElem_toArray, List.getElem_singleton]
-  cases lt a b <;> cases a != b <;> simp [Id.run]
-
-protected theorem lt_irrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] (l : Vector α n) : ¬ l < l :=
-  Array.lt_irrefl l.toArray
-
-instance ltIrrefl [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Irrefl (α := Vector α n) (· < ·) where
-  irrefl := Vector.lt_irrefl
-
-@[simp] theorem empty_le [LT α] (l : Vector α 0) : #v[] ≤ l := Array.empty_le l.toArray
-
-@[simp] theorem le_empty [LT α] (l : Vector α 0) : l ≤ #v[] ↔ l = #v[] := by
-  cases l
-  simp
-
-protected theorem le_refl [LT α] [i₀ : Std.Irrefl (· < · : α → α → Prop)] (l : Vector α n) : l ≤ l :=
-  Array.le_refl l.toArray
-
-instance [LT α] [Std.Irrefl (· < · : α → α → Prop)] : Std.Refl (· ≤ · : Vector α n → Vector α n → Prop) where
-  refl := Vector.le_refl
-
-protected theorem lt_trans [LT α] [DecidableLT α]
-    [i₁ : Trans (· < · : α → α → Prop) (· < ·) (· < ·)]
-    {l₁ l₂ l₃ : Vector α n} (h₁ : l₁ < l₂) (h₂ : l₂ < l₃) : l₁ < l₃ :=
-  Array.lt_trans h₁ h₂
-
-instance [LT α] [DecidableLT α]
-    [Trans (· < · : α → α → Prop) (· < ·) (· < ·)] :
-    Trans (· < · : Vector α n → Vector α n → Prop) (· < ·) (· < ·) where
-  trans h₁ h₂ := Vector.lt_trans h₁ h₂
-
-protected theorem lt_of_le_of_lt [DecidableEq α] [LT α] [DecidableLT α]
-    [i₀ : Std.Irrefl (· < · : α → α → Prop)]
-    [i₁ : Std.Asymm (· < · : α → α → Prop)]
-    [i₂ : Std.Antisymm (¬ · < · : α → α → Prop)]
-    [i₃ : Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : Vector α n} (h₁ : l₁ ≤ l₂) (h₂ : l₂ < l₃) : l₁ < l₃ :=
-  Array.lt_of_le_of_lt h₁ h₂
-
-protected theorem le_trans [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)]
-    {l₁ l₂ l₃ : Vector α n} (h₁ : l₁ ≤ l₂) (h₂ : l₂ ≤ l₃) : l₁ ≤ l₃ :=
-  fun h₃ => h₁ (Vector.lt_of_le_of_lt h₂ h₃)
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)]
-    [Trans (¬ · < · : α → α → Prop) (¬ · < ·) (¬ · < ·)] :
-    Trans (· ≤ · : Vector α n → Vector α n → Prop) (· ≤ ·) (· ≤ ·) where
-  trans h₁ h₂ := Vector.le_trans h₁ h₂
-
-protected theorem lt_asymm [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Asymm (· < · : α → α → Prop)]
-    {l₁ l₂ : Vector α n} (h : l₁ < l₂) : ¬ l₂ < l₁ := Array.lt_asymm h
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Asymm (· < · : α → α → Prop)] :
-    Std.Asymm (· < · : Vector α n → Vector α n → Prop) where
-  asymm _ _ := Vector.lt_asymm
-
-protected theorem le_total [DecidableEq α] [LT α] [DecidableLT α]
-    [i : Std.Total (¬ · < · : α → α → Prop)] {l₁ l₂ : Vector α n} : l₁ ≤ l₂ ∨ l₂ ≤ l₁ :=
-  Array.le_total
-
-instance [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Total (¬ · < · : α → α → Prop)] :
-    Std.Total (· ≤ · : Vector α n → Vector α n → Prop) where
-  total _ _ := Vector.le_total
-
-@[simp] theorem lex_eq_true_iff_lt [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : Vector α n} : lex l₁ l₂ = true ↔ l₁ < l₂ := by
-  cases l₁
-  cases l₂
-  simp
-
-@[simp] theorem lex_eq_false_iff_ge [DecidableEq α] [LT α] [DecidableLT α]
-    {l₁ l₂ : Vector α n} : lex l₁ l₂ = false ↔ l₂ ≤ l₁ := by
-  cases l₁
-  cases l₂
-  simp [Array.not_lt_iff_ge]
-
-instance [DecidableEq α] [LT α] [DecidableLT α] : DecidableLT (Vector α n) :=
-  fun l₁ l₂ => decidable_of_iff (lex l₁ l₂ = true) lex_eq_true_iff_lt
-
-instance [DecidableEq α] [LT α] [DecidableLT α] : DecidableLE (Vector α n) :=
-  fun l₁ l₂ => decidable_of_iff (lex l₂ l₁ = false) lex_eq_false_iff_ge
-
-/--
-`l₁` is lexicographically less than `l₂` if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.size`,
-  and `l₁` is shorter than `l₂` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₁[i] < l₂[i]`
--/
-theorem lex_eq_true_iff_exists [BEq α] (lt : α → α → Bool) {l₁ l₂ : Vector α n} :
-    lex l₁ l₂ lt = true ↔
-      (∃ (i : Nat) (h : i < n), (∀ j, (hj : j < i) → l₁[j] == l₂[j]) ∧ lt l₁[i] l₂[i]) := by
-  rcases l₁ with ⟨l₁, n₁⟩
-  rcases l₂ with ⟨l₂, n₂⟩
-  simp [Array.lex_eq_true_iff_exists, n₁, n₂]
-
-/--
-`l₁` is *not* lexicographically less than `l₂`
-(which you might think of as "`l₂` is lexicographically greater than or equal to `l₁`"") if either
-- `l₁` is pairwise equivalent under `· == ·` to `l₂.take l₁.length` or
-- there exists an index `i` such that
-  - for all `j < i`, `l₁[j] == l₂[j]` and
-  - `l₂[i] < l₁[i]`
-
-This formulation requires that `==` and `lt` are compatible in the following senses:
-- `==` is symmetric
-  (we unnecessarily further assume it is transitive, to make use of the existing typeclasses)
-- `lt` is irreflexive with respect to `==` (i.e. if `x == y` then `lt x y = false`
-- `lt` is asymmmetric  (i.e. `lt x y = true → lt y x = false`)
-- `lt` is antisymmetric with respect to `==` (i.e. `lt x y = false → lt y x = false → x == y`)
--/
-theorem lex_eq_false_iff_exists [BEq α] [PartialEquivBEq α] (lt : α → α → Bool)
-    (lt_irrefl : ∀ x y, x == y → lt x y = false)
-    (lt_asymm : ∀ x y, lt x y = true → lt y x = false)
-    (lt_antisymm : ∀ x y, lt x y = false → lt y x = false → x == y)
-    {l₁ l₂ : Vector α n} :
-    lex l₁ l₂ lt = false ↔
-      (l₂.isEqv l₁ (· == ·)) ∨
-        (∃ (i : Nat) (h : i < n),(∀ j, (hj : j < i) → l₁[j] == l₂[j]) ∧ lt l₂[i] l₁[i]) := by
-  rcases l₁ with ⟨l₁, rfl⟩
-  rcases l₂ with ⟨l₂, n₂⟩
-  simp_all [Array.lex_eq_false_iff_exists, n₂]
-
-theorem lt_iff_exists [DecidableEq α] [LT α] [DecidableLT α] {l₁ l₂ : Vector α n} :
-    l₁ < l₂ ↔
-      (∃ (i : Nat) (h : i < n), (∀ j, (hj : j < i) → l₁[j] = l₂[j]) ∧ l₁[i] < l₂[i]) := by
-  cases l₁
-  cases l₂
-  simp_all [Array.lt_iff_exists]
-
-theorem le_iff_exists [DecidableEq α] [LT α] [DecidableLT α]
-    [Std.Irrefl (· < · : α → α → Prop)]
-    [Std.Asymm (· < · : α → α → Prop)]
-    [Std.Antisymm (¬ · < · : α → α → Prop)] {l₁ l₂ : Vector α n} :
-    l₁ ≤ l₂ ↔
-      (l₁ = l₂) ∨
-        (∃ (i : Nat) (h : i < n), (∀ j, (hj : j < i) → l₁[j] = l₂[j]) ∧ l₁[i] < l₂[i]) := by
-  rcases l₁ with ⟨l₁, rfl⟩
-  rcases l₂ with ⟨l₂, n₂⟩
-  simp [Array.le_iff_exists, ← n₂]
-
-end Vector

src/Init/GetElem.lean

@@ -176,14 +176,11 @@ theorem getElem!_neg [GetElem? cont idx elem dom] [LawfulGetElem cont idx elem d
   simp only [getElem?_def] at h ⊢
   split <;> simp_all
 
-@[simp] theorem getElem?_eq_none [GetElem? cont idx elem dom] [LawfulGetElem cont idx elem dom]
-    (c : cont) (i : idx) [Decidable (dom c i)] : c[i]? = none ↔ ¬dom c i := by
+@[simp] theorem isNone_getElem? [GetElem? cont idx elem dom] [LawfulGetElem cont idx elem dom]
+    (c : cont) (i : idx) [Decidable (dom c i)] : c[i]?.isNone = ¬dom c i := by
   simp only [getElem?_def]
   split <;> simp_all
 
-@[deprecated getElem?_eq_none (since := "2024-12-11")]
-abbrev isNone_getElem? := @getElem?_eq_none
-
 @[simp] theorem isSome_getElem? [GetElem? cont idx elem dom] [LawfulGetElem cont idx elem dom]
     (c : cont) (i : idx) [Decidable (dom c i)] : c[i]?.isSome = dom c i := by
   simp only [getElem?_def]

src/Init/NotationExtra.lean

@@ -168,6 +168,11 @@ end Lean
   | `($(_) $c $t $e) => `(if $c then $t else $e)
   | _                => throw ()
 
+@[app_unexpander sorryAx] def unexpandSorryAx : Lean.PrettyPrinter.Unexpander
+  | `($(_) $_)    => `(sorry)
+  | `($(_) $_ $_) => `(sorry)
+  | _             => throw ()
+
 @[app_unexpander Eq.ndrec] def unexpandEqNDRec : Lean.PrettyPrinter.Unexpander
   | `($(_) $m $h) => `($h ▸ $m)
   | _             => throw ()

src/Init/Prelude.lean

@@ -645,22 +645,23 @@ set_option linter.unusedVariables.funArgs false in
 @[reducible] def namedPattern {α : Sort u} (x a : α) (h : Eq x a) : α := a
 
 /--
-Auxiliary axiom used to implement the `sorry` term and tactic.
+Auxiliary axiom used to implement `sorry`.
 
-The `sorry` term/tactic expands to `sorryAx _ (synthetic := false)`.
-It is intended for stubbing-out incomplete parts of a value or proof while still having a syntactically correct skeleton.
-Lean will give a warning whenever a declaration uses `sorry`, so you aren't likely to miss it,
-but you can check if a declaration depends on `sorry` either directly or indirectly by looking for `sorryAx` in the output
-of the `#print axioms my_thm` command.
+The `sorry` term/tactic expands to `sorryAx _ (synthetic := false)`. This is a
+proof of anything, which is intended for stubbing out incomplete parts of a
+proof while still having a syntactically correct proof skeleton. Lean will give
+a warning whenever a proof uses `sorry`, so you aren't likely to miss it, but
+you can double check if a theorem depends on `sorry` by using
+`#print axioms my_thm` and looking for `sorryAx` in the axiom list.
 
-The `synthetic` flag is false when a `sorry` is written explicitly by the user, but it is
+The `synthetic` flag is false when written explicitly by the user, but it is
 set to `true` when a tactic fails to prove a goal, or if there is a type error
 in the expression. A synthetic `sorry` acts like a regular one, except that it
-suppresses follow-up errors in order to prevent an error from causing a cascade
+suppresses follow-up errors in order to prevent one error from causing a cascade
 of other errors because the desired term was not constructed.
 -/
 @[extern "lean_sorry", never_extract]
-axiom sorryAx (α : Sort u) (synthetic : Bool) : α
+axiom sorryAx (α : Sort u) (synthetic := false) : α
 
 theorem eq_false_of_ne_true : {b : Bool} → Not (Eq b true) → Eq b false
   | true, h => False.elim (h rfl)
@@ -859,8 +860,8 @@ abbrev DecidablePred {α : Sort u} (r : α → Prop) :=
   (a : α) → Decidable (r a)
 
 /-- A decidable relation. See `Decidable`. -/
-abbrev DecidableRel {α : Sort u} {β : Sort v} (r : α → β → Prop) :=
-  (a : α) → (b : β) → Decidable (r a b)
+abbrev DecidableRel {α : Sort u} (r : α → α → Prop) :=
+  (a b : α) → Decidable (r a b)
 
 /--
 Asserts that `α` has decidable equality, that is, `a = b` is decidable
@@ -1126,11 +1127,6 @@ class LT (α : Type u) where
 /-- `a > b` is an abbreviation for `b < a`. -/
 @[reducible] def GT.gt {α : Type u} [LT α] (a b : α) : Prop := LT.lt b a
 
-/-- Abbreviation for `DecidableRel (· < · : α → α → Prop)`. -/
-abbrev DecidableLT (α : Type u) [LT α] := DecidableRel (LT.lt : α → α → Prop)
-/-- Abbreviation for `DecidableRel (· ≤ · : α → α → Prop)`. -/
-abbrev DecidableLE (α : Type u) [LE α] := DecidableRel (LE.le : α → α → Prop)
-
 /-- `Max α` is the typeclass which supports the operation `max x y` where `x y : α`.-/
 class Max (α : Type u) where
   /-- The maximum operation: `max x y`. -/
@@ -2554,7 +2550,7 @@ When we reimplement the specializer, we may consider copying `inst` if it also
 occurs outside binders or if it is an instance.
 -/
 @[never_extract, extern "lean_panic_fn"]
-def panicCore {α : Sort u} [Inhabited α] (msg : String) : α := default
+def panicCore {α : Type u} [Inhabited α] (msg : String) : α := default
 
 /--
 `(panic "msg" : α)` has a built-in implementation which prints `msg` to
@@ -2568,7 +2564,7 @@ Because this is a pure function with side effects, it is marked as
 elimination and other optimizations that assume that the expression is pure.
 -/
 @[noinline, never_extract]
-def panic {α : Sort u} [Inhabited α] (msg : String) : α :=
+def panic {α : Type u} [Inhabited α] (msg : String) : α :=
   panicCore msg
 
 -- TODO: this be applied directly to `Inhabited`'s definition when we remove the above workaround
@@ -3936,13 +3932,6 @@ def getId : Syntax → Name
   | ident _ _ val _ => val
   | _               => Name.anonymous
 
-/-- Retrieve the immediate info from the Syntax node. -/
-def getInfo? : Syntax → Option SourceInfo
-  | atom info ..  => some info
-  | ident info .. => some info
-  | node info ..  => some info
-  | missing       => none
-
 /-- Retrieve the left-most node or leaf's info in the Syntax tree. -/
 partial def getHeadInfo? : Syntax → Option SourceInfo
   | atom info _   => some info

src/Init/PropLemmas.lean

@@ -362,10 +362,6 @@ theorem exists_prop' {p : Prop} : (∃ _ : α, p) ↔ Nonempty α ∧ p :=
 @[simp] theorem exists_prop : (∃ _h : a, b) ↔ a ∧ b :=
   ⟨fun ⟨hp, hq⟩ => ⟨hp, hq⟩, fun ⟨hp, hq⟩ => ⟨hp, hq⟩⟩
 
-@[simp] theorem exists_idem {P : Prop} (f : P → P → Sort _) :
-    (∃ (p₁ : P), ∃ (p₂ : P), f p₁ p₂) ↔ ∃ (p : P), f p p :=
-  ⟨fun ⟨p, _, h⟩ => ⟨p, h⟩, fun ⟨p, h⟩ => ⟨p, p, h⟩⟩
-
 @[simp] theorem exists_apply_eq_apply (f : α → β) (a' : α) : ∃ a, f a = f a' := ⟨a', rfl⟩
 
 theorem forall_prop_of_true {p : Prop} {q : p → Prop} (h : p) : (∀ h' : p, q h') ↔ q h :=

src/Init/SimpLemmas.lean

@@ -153,7 +153,6 @@ instance : Std.LawfulIdentity Or False where
 @[simp] theorem false_implies (p : Prop) : (False → p) = True := eq_true False.elim
 @[simp] theorem forall_false (p : False → Prop) : (∀ h : False, p h) = True := eq_true (False.elim ·)
 @[simp] theorem implies_true (α : Sort u) : (α → True) = True := eq_true fun _ => trivial
--- This is later proved by the simp lemma `forall_const`, but this is useful during bootstrapping.
 @[simp] theorem true_implies (p : Prop) : (True → p) = p := propext ⟨(· trivial), (fun _ => ·)⟩
 @[simp] theorem not_false_eq_true : (¬ False) = True := eq_true False.elim
 @[simp] theorem not_true_eq_false : (¬ True) = False := by decide

src/Init/Tactics.lean

@@ -408,18 +408,16 @@ example (a b c d : Nat) : a + b + c + d = d + (b + c) + a := by ac_rfl
 syntax (name := acRfl) "ac_rfl" : tactic
 
 /--
-The `sorry` tactic is a temporary placeholder for an incomplete tactic proof,
-closing the main goal using `exact sorry`.
-
-This is intended for stubbing-out incomplete parts of a proof while still having a syntactically correct proof skeleton.
-Lean will give a warning whenever a proof uses `sorry`, so you aren't likely to miss it,
-but you can double check if a theorem depends on `sorry` by looking for `sorryAx` in the output
-of the `#print axioms my_thm` command, the axiom used by the implementation of `sorry`.
+The `sorry` tactic closes the goal using `sorryAx`. This is intended for stubbing out incomplete
+parts of a proof while still having a syntactically correct proof skeleton. Lean will give
+a warning whenever a proof uses `sorry`, so you aren't likely to miss it, but
+you can double check if a theorem depends on `sorry` by using
+`#print axioms my_thm` and looking for `sorryAx` in the axiom list.
 -/
-macro "sorry" : tactic => `(tactic| exact sorry)
+macro "sorry" : tactic => `(tactic| exact @sorryAx _ false)
 
-/-- `admit` is a synonym for `sorry`. -/
-macro "admit" : tactic => `(tactic| sorry)
+/-- `admit` is a shorthand for `exact sorry`. -/
+macro "admit" : tactic => `(tactic| exact @sorryAx _ false)
 
 /--
 `infer_instance` is an abbreviation for `exact inferInstance`.

src/Init/Util.lean

@@ -33,13 +33,13 @@ def dbgSleep {α : Type u} (ms : UInt32) (f : Unit → α) : α := f ()
 @[noinline] private def mkPanicMessage (modName : String) (line col : Nat) (msg : String) : String :=
   "PANIC at " ++ modName ++ ":" ++ toString line ++ ":" ++ toString col ++ ": " ++ msg
 
-@[never_extract, inline] def panicWithPos {α : Sort u} [Inhabited α] (modName : String) (line col : Nat) (msg : String) : α :=
+@[never_extract, inline] def panicWithPos {α : Type u} [Inhabited α] (modName : String) (line col : Nat) (msg : String) : α :=
   panic (mkPanicMessage modName line col msg)
 
 @[noinline] private def mkPanicMessageWithDecl (modName : String) (declName : String) (line col : Nat) (msg : String) : String :=
   "PANIC at " ++ declName ++ " " ++ modName ++ ":" ++ toString line ++ ":" ++ toString col ++ ": " ++ msg
 
-@[never_extract, inline] def panicWithPosWithDecl {α : Sort u} [Inhabited α] (modName : String) (declName : String) (line col : Nat) (msg : String) : α :=
+@[never_extract, inline] def panicWithPosWithDecl {α : Type u} [Inhabited α] (modName : String) (declName : String) (line col : Nat) (msg : String) : α :=
   panic (mkPanicMessageWithDecl modName declName line col msg)
 
 @[extern "lean_ptr_addr"]

src/Lean/Compiler/LCNF.lean

@@ -35,6 +35,7 @@ import Lean.Compiler.LCNF.ToLCNF
 import Lean.Compiler.LCNF.Types
 import Lean.Compiler.LCNF.Util
 import Lean.Compiler.LCNF.ConfigOptions
+import Lean.Compiler.LCNF.ForEachExpr
 import Lean.Compiler.LCNF.MonoTypes
 import Lean.Compiler.LCNF.ToMono
 import Lean.Compiler.LCNF.MonadScope

src/Lean/Compiler/LCNF/ForEachExpr.lean

@@ -0,0 +1,14 @@
+/-
+Copyright (c) 2022 Microsoft Corporation. All rights reserved.
+Released under Apache 2.0 license as described in the file LICENSE.
+Authors: Leonardo de Moura
+-/
+prelude
+import Lean.Util.ForEachExpr
+import Lean.Compiler.LCNF.Basic
+
+namespace Lean.Compiler.LCNF
+
+-- TODO: delete
+
+end Lean.Compiler.LCNF

src/Lean/Compiler/LCNF/Main.lean

@@ -29,7 +29,7 @@ and `[specialize]` since they can be partially applied.
 def shouldGenerateCode (declName : Name) : CoreM Bool := do
   if (← isCompIrrelevant |>.run') then return false
   let some info ← getDeclInfo? declName | return false
-  unless info.hasValue (allowOpaque := true) do return false
+  unless info.hasValue do return false
   let env ← getEnv
   if isExtern env declName then return false
   if hasMacroInlineAttribute env declName then return false

src/Lean/Compiler/LCNF/Probing.lean

@@ -7,6 +7,7 @@ prelude
 import Lean.Compiler.LCNF.CompilerM
 import Lean.Compiler.LCNF.PassManager
 import Lean.Compiler.LCNF.PhaseExt
+import Lean.Compiler.LCNF.ForEachExpr
 
 namespace Lean.Compiler.LCNF
 
@@ -21,7 +22,7 @@ def map (f : α → CompilerM β) : Probe α β := fun data => data.mapM f
 def filter (f : α → CompilerM Bool) : Probe α α := fun data => data.filterM f
 
 @[inline]
-def sorted [Inhabited α] [LT α] [DecidableLT α] : Probe α α := fun data => return data.qsort (· < ·)
+def sorted [Inhabited α] [inst : LT α] [DecidableRel inst.lt] : Probe α α := fun data => return data.qsort (· < ·)
 
 @[inline]
 def sortedBySize : Probe Decl (Nat × Decl) := fun decls =>

src/Lean/Compiler/LCNF/ToDecl.lean

@@ -96,7 +96,7 @@ The steps for this are roughly:
 def toDecl (declName : Name) : CompilerM Decl := do
   let declName := if let some name := isUnsafeRecName? declName then name else declName
   let some info ← getDeclInfo? declName | throwError "declaration `{declName}` not found"
-  let some value := info.value? (allowOpaque := true) | throwError "declaration `{declName}` does not have a value"
+  let some value := info.value? | throwError "declaration `{declName}` does not have a value"
   let (type, value) ← Meta.MetaM.run' do
     let type  ← toLCNFType info.type
     let value ← Meta.lambdaTelescope value fun xs body => do Meta.mkLambdaFVars xs (← Meta.etaExpand body)
@@ -107,7 +107,7 @@ def toDecl (declName : Name) : CompilerM Decl := do
     /- Recall that `inlineMatchers` may have exposed `ite`s and `dite`s which are tagged as `[macro_inline]`. -/
     let value ← macroInline value
     /-
-    Remark: we have disabled the following transformatbion, we will perform it at phase 2, after code specialization.
+    Remark: we have disabled the following transformation, we will perform it at phase 2, after code specialization.
     It prevents many optimizations (e.g., "cases-of-ctor").
     -/
     -- let value ← applyCasesOnImplementedBy value

src/Lean/Compiler/LCNF/Util.lean

@@ -56,7 +56,7 @@ def getCasesInfo? (declName : Name) : CoreM (Option CasesInfo) := do
   let arity        := numParams + 1 /- motive -/ + val.numIndices + 1 /- major -/ + val.numCtors
   let discrPos     := numParams + 1 /- motive -/ + val.numIndices
   -- We view indices as discriminants
-  let altsRange    := [discrPos + 1:arity]
+  let altsRange    := { start := discrPos + 1,  stop := arity }
   let altNumParams ← val.ctors.toArray.mapM fun ctor => do
     let .ctorInfo ctorVal ← getConstInfo ctor | unreachable!
     return ctorVal.numFields

src/Lean/CoreM.lean

@@ -612,14 +612,14 @@ instance : MonadRuntimeException CoreM where
 
 /--
 Returns `true` if the given message kind has not been reported in the message log,
-and then mark it as logged. Otherwise, returns `false`.
-We use this API to ensure we don't log the same kind of warning multiple times.
+and then mark it as reported. Otherwise, returns `false`.
+We use this API to ensure we don't report the same kind of warning multiple times.
 -/
-def logMessageKind (kind : Name) : CoreM Bool := do
-  if (← get).messages.loggedKinds.contains kind then
+def reportMessageKind (kind : Name) : CoreM Bool := do
+  if (← get).messages.reportedKinds.contains kind then
     return false
   else
-    modify fun s => { s with messages.loggedKinds := s.messages.loggedKinds.insert kind }
+    modify fun s => { s with messages.reportedKinds := s.messages.reportedKinds.insert kind }
     return true
 
 end Lean

src/Lean/Data/DeclarationRange.lean

@@ -1,49 +0,0 @@
-/-
-Copyright (c) 2021 Microsoft Corporation. All rights reserved.
-Released under Apache 2.0 license as described in the file LICENSE.
-Authors: Leonardo de Moura
--/
-prelude
-import Lean.Data.Position
-
-/-!
-# Data types for declaration ranges
-
-The environment extension for declaration ranges is in `Lean.DeclarationRange`.
--/
-
-namespace Lean
-
-/-- Store position information for declarations. -/
-structure DeclarationRange where
-  pos          : Position
-  /-- A precomputed UTF-16 `character` field as in `Lean.Lsp.Position`. We need to store this
-  because LSP clients want us to report the range in terms of UTF-16, but converting a Unicode
-  codepoint stored in `Lean.Position` to UTF-16 requires loading and mapping the target source
-  file, which is IO-heavy. -/
-  charUtf16    : Nat
-  endPos       : Position
-  /-- See `charUtf16`. -/
-  endCharUtf16 : Nat
-  deriving Inhabited, DecidableEq, Repr
-
-instance : ToExpr DeclarationRange where
-  toExpr r   := mkAppN (mkConst ``DeclarationRange.mk) #[toExpr r.pos, toExpr r.charUtf16, toExpr r.endPos, toExpr r.endCharUtf16]
-  toTypeExpr := mkConst ``DeclarationRange
-
-structure DeclarationRanges where
-  range          : DeclarationRange
-  selectionRange : DeclarationRange
-  deriving Inhabited, Repr
-
-instance : ToExpr DeclarationRanges where
-  toExpr r   := mkAppN (mkConst ``DeclarationRanges.mk) #[toExpr r.range, toExpr r.selectionRange]
-  toTypeExpr := mkConst ``DeclarationRanges
-
-/--
-A declaration location is a declaration range along with the name of the module the declaration resides in.
--/
-structure DeclarationLocation where
-  module : Name
-  range : DeclarationRange
-  deriving Inhabited, DecidableEq, Repr

src/Lean/Data/RArray.lean

@@ -55,7 +55,7 @@ where
   go lb ub h1 h2 : (ofFn.go f lb ub h1 h2).size = ub - lb := by
     induction lb, ub, h1, h2 using RArray.ofFn.go.induct (n := n)
     case case1 => simp [ofFn.go, size]; omega
-    case case2 ih1 ih2 hiu => rw [ofFn.go]; simp +zetaDelta [size, *]; omega
+    case case2 ih1 ih2 hiu => rw [ofFn.go]; simp [size, *]; omega
 
 section Meta
 open Lean

src/Lean/Declaration.lean

@@ -44,7 +44,7 @@ def mkReducibilityHintsRegularEx (h : UInt32) : ReducibilityHints :=
 @[export lean_reducibility_hints_get_height]
 def ReducibilityHints.getHeightEx (h : ReducibilityHints) : UInt32 :=
   match h with
-  | .regular h => h
+  | ReducibilityHints.regular h => h
   | _ => 0
 
 namespace ReducibilityHints
@@ -74,8 +74,8 @@ def isAbbrev : ReducibilityHints → Bool
   | _       => false
 
 def isRegular : ReducibilityHints → Bool
-  | .regular .. => true
-  | _           => false
+  | regular .. => true
+  | _          => false
 
 end ReducibilityHints
 
@@ -186,7 +186,7 @@ def mkInductiveDeclEs (lparams : List Name) (nparams : Nat) (types : List Induct
 
 @[export lean_is_unsafe_inductive_decl]
 def Declaration.isUnsafeInductiveDeclEx : Declaration → Bool
-  | .inductDecl _ _ _ isUnsafe => isUnsafe
+  | Declaration.inductDecl _ _ _ isUnsafe => isUnsafe
   | _ => false
 
 def Declaration.definitionVal! : Declaration → DefinitionVal
@@ -195,16 +195,18 @@ def Declaration.definitionVal! : Declaration → DefinitionVal
 
 @[specialize] def Declaration.foldExprM {α} {m : Type → Type} [Monad m] (d : Declaration) (f : α → Expr → m α) (a : α) : m α :=
   match d with
-  | .quotDecl                                        => pure a
-  | .axiomDecl { type := type, .. }                  => f a type
-  | .defnDecl { type := type, value := value, .. }   => do let a ← f a type; f a value
-  | .opaqueDecl { type := type, value := value, .. } => do let a ← f a type; f a value
-  | .thmDecl { type := type, value := value, .. }    => do let a ← f a type; f a value
-  | .mutualDefnDecl vals                             => vals.foldlM (fun a v => do let a ← f a v.type; f a v.value) a
-  | .inductDecl _ _ inductTypes _                    =>
-    inductTypes.foldlM (init := a) fun a inductType => do
-      let a ← f a inductType.type
-      inductType.ctors.foldlM (fun a ctor => f a ctor.type) a
+  | Declaration.quotDecl                                        => pure a
+  | Declaration.axiomDecl { type := type, .. }                  => f a type
+  | Declaration.defnDecl { type := type, value := value, .. }   => do let a ← f a type; f a value
+  | Declaration.opaqueDecl { type := type, value := value, .. } => do let a ← f a type; f a value
+  | Declaration.thmDecl { type := type, value := value, .. }    => do let a ← f a type; f a value
+  | Declaration.mutualDefnDecl vals                             => vals.foldlM (fun a v => do let a ← f a v.type; f a v.value) a
+  | Declaration.inductDecl _ _ inductTypes _                    =>
+    inductTypes.foldlM
+      (fun a inductType => do
+        let a ← f a inductType.type
+        inductType.ctors.foldlM (fun a ctor => f a ctor.type) a)
+      a
 
 @[inline] def Declaration.forExprM {m : Type → Type} [Monad m] (d : Declaration) (f : Expr → m Unit) : m Unit :=
   d.foldExprM (fun _ a => f a) ()
@@ -300,7 +302,14 @@ structure ConstructorVal extends ConstantVal where
 
 @[export lean_mk_constructor_val]
 def mkConstructorValEx (name : Name) (levelParams : List Name) (type : Expr) (induct : Name) (cidx numParams numFields : Nat) (isUnsafe : Bool) : ConstructorVal := {
-  name, levelParams, type, induct, cidx, numParams, numFields, isUnsafe
+  name := name,
+  levelParams := levelParams,
+  type := type,
+  induct := induct,
+  cidx := cidx,
+  numParams := numParams,
+  numFields := numFields,
+  isUnsafe := isUnsafe
 }
 
 @[export lean_constructor_val_is_unsafe] def ConstructorVal.isUnsafeEx (v : ConstructorVal) : Bool := v.isUnsafe
@@ -344,8 +353,8 @@ structure RecursorVal extends ConstantVal where
 @[export lean_mk_recursor_val]
 def mkRecursorValEx (name : Name) (levelParams : List Name) (type : Expr) (all : List Name) (numParams numIndices numMotives numMinors : Nat)
     (rules : List RecursorRule) (k isUnsafe : Bool) : RecursorVal := {
-  name, levelParams, type, all, numParams, numIndices,
-  numMotives, numMinors, rules, k, isUnsafe
+  name := name, levelParams := levelParams, type := type, all := all, numParams := numParams, numIndices := numIndices,
+  numMotives := numMotives, numMinors := numMinors, rules := rules, k := k, isUnsafe := isUnsafe
 }
 
 @[export lean_recursor_k] def RecursorVal.kEx (v : RecursorVal) : Bool := v.k
@@ -401,27 +410,27 @@ inductive ConstantInfo where
 namespace ConstantInfo
 
 def toConstantVal : ConstantInfo → ConstantVal
-  | .defnInfo     {toConstantVal := d, ..} => d
-  | .axiomInfo    {toConstantVal := d, ..} => d
-  | .thmInfo      {toConstantVal := d, ..} => d
-  | .opaqueInfo   {toConstantVal := d, ..} => d
-  | .quotInfo     {toConstantVal := d, ..} => d
-  | .inductInfo   {toConstantVal := d, ..} => d
-  | .ctorInfo     {toConstantVal := d, ..} => d
-  | .recInfo      {toConstantVal := d, ..} => d
+  | defnInfo     {toConstantVal := d, ..} => d
+  | axiomInfo    {toConstantVal := d, ..} => d
+  | thmInfo      {toConstantVal := d, ..} => d
+  | opaqueInfo   {toConstantVal := d, ..} => d
+  | quotInfo     {toConstantVal := d, ..} => d
+  | inductInfo   {toConstantVal := d, ..} => d
+  | ctorInfo     {toConstantVal := d, ..} => d
+  | recInfo      {toConstantVal := d, ..} => d
 
 def isUnsafe : ConstantInfo → Bool
-  | .defnInfo   v => v.safety == .unsafe
-  | .axiomInfo  v => v.isUnsafe
-  | .thmInfo    _ => false
-  | .opaqueInfo v => v.isUnsafe
-  | .quotInfo   _ => false
-  | .inductInfo v => v.isUnsafe
-  | .ctorInfo   v => v.isUnsafe
-  | .recInfo    v => v.isUnsafe
+  | defnInfo   v => v.safety == .unsafe
+  | axiomInfo  v => v.isUnsafe
+  | thmInfo    _ => false
+  | opaqueInfo v => v.isUnsafe
+  | quotInfo   _ => false
+  | inductInfo v => v.isUnsafe
+  | ctorInfo   v => v.isUnsafe
+  | recInfo    v => v.isUnsafe
 
 def isPartial : ConstantInfo → Bool
-  | .defnInfo v => v.safety == .partial
+  | defnInfo v => v.safety == .partial
   | _ => false
 
 def name (d : ConstantInfo) : Name :=
@@ -436,42 +445,36 @@ def numLevelParams (d : ConstantInfo) : Nat :=
 def type (d : ConstantInfo) : Expr :=
   d.toConstantVal.type
 
-def value? (info : ConstantInfo) (allowOpaque := false) : Option Expr :=
-  match info with
-  | .defnInfo {value, ..}   => some value
-  | .thmInfo  {value, ..}   => some value
-  | .opaqueInfo {value, ..} => if allowOpaque then some value else none
-  | _                       => none
+def value? : ConstantInfo → Option Expr
+  | defnInfo {value := r, ..} => some r
+  | thmInfo  {value := r, ..} => some r
+  | _                         => none
 
-def hasValue (info : ConstantInfo) (allowOpaque := false) : Bool :=
-  match info with
-  | .defnInfo _   => true
-  | .thmInfo  _   => true
-  | .opaqueInfo _ => allowOpaque
-  | _             => false
+def hasValue : ConstantInfo → Bool
+  | defnInfo _ => true
+  | thmInfo  _ => true
+  | _                         => false
 
-def value! (info : ConstantInfo) (allowOpaque := false) : Expr :=
-  match info with
-  | .defnInfo {value, ..}   => value
-  | .thmInfo  {value, ..}   => value
-  | .opaqueInfo {value, ..} => if allowOpaque then value else panic! "declaration with value expected"
-  | _                       => panic! "declaration with value expected"
+def value! : ConstantInfo → Expr
+  | defnInfo {value := r, ..} => r
+  | thmInfo  {value := r, ..} => r
+  | _                         => panic! "declaration with value expected"
 
 def hints : ConstantInfo → ReducibilityHints
-  | .defnInfo {hints, ..} => hints
-  | _                     => .opaque
+  | defnInfo {hints := r, ..} => r
+  | _                         => ReducibilityHints.opaque
 
 def isCtor : ConstantInfo → Bool
-  | .ctorInfo _ => true
-  | _           => false
+  | ctorInfo _ => true
+  | _          => false
 
 def isInductive : ConstantInfo → Bool
-  | .inductInfo _ => true
-  | _             => false
+  | inductInfo _ => true
+  | _            => false
 
 def isTheorem : ConstantInfo → Bool
-  | .thmInfo _ => true
-  | _          => false
+  | thmInfo _ => true
+  | _         => false
 
 def inductiveVal! : ConstantInfo → InductiveVal
   | .inductInfo val => val
@@ -481,11 +484,11 @@ def inductiveVal! : ConstantInfo → InductiveVal
   List of all (including this one) declarations in the same mutual block.
 -/
 def all : ConstantInfo → List Name
-  | .inductInfo val => val.all
-  | .defnInfo val   => val.all
-  | .thmInfo val    => val.all
-  | .opaqueInfo val => val.all
-  | info            => [info.name]
+  | inductInfo val => val.all
+  | defnInfo val   => val.all
+  | thmInfo val    => val.all
+  | opaqueInfo val => val.all
+  | info           => [info.name]
 
 end ConstantInfo
 

src/Lean/DeclarationRange.lean

@@ -4,15 +4,38 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Leonardo de Moura
 -/
 prelude
-import Lean.Data.DeclarationRange
 import Lean.MonadEnv
-
-/-!
-# Environment extension for declaration ranges
--/
+import Lean.AuxRecursor
+import Lean.ToExpr
 
 namespace Lean
 
+/-- Store position information for declarations. -/
+structure DeclarationRange where
+  pos          : Position
+  /-- A precomputed UTF-16 `character` field as in `Lean.Lsp.Position`. We need to store this
+  because LSP clients want us to report the range in terms of UTF-16, but converting a Unicode
+  codepoint stored in `Lean.Position` to UTF-16 requires loading and mapping the target source
+  file, which is IO-heavy. -/
+  charUtf16    : Nat
+  endPos       : Position
+  /-- See `charUtf16`. -/
+  endCharUtf16 : Nat
+  deriving Inhabited, DecidableEq, Repr
+
+instance : ToExpr DeclarationRange where
+  toExpr r   := mkAppN (mkConst ``DeclarationRange.mk) #[toExpr r.pos, toExpr r.charUtf16, toExpr r.endPos, toExpr r.endCharUtf16]
+  toTypeExpr := mkConst ``DeclarationRange
+
+structure DeclarationRanges where
+  range          : DeclarationRange
+  selectionRange : DeclarationRange
+  deriving Inhabited, Repr
+
+instance : ToExpr DeclarationRanges where
+  toExpr r   := mkAppN (mkConst ``DeclarationRanges.mk) #[toExpr r.range, toExpr r.selectionRange]
+  toTypeExpr := mkConst ``DeclarationRanges
+
 builtin_initialize builtinDeclRanges : IO.Ref (NameMap DeclarationRanges) ← IO.mkRef {}
 builtin_initialize declRangeExt : MapDeclarationExtension DeclarationRanges ← mkMapDeclarationExtension
 

src/Lean/Elab/BuiltinNotation.lean

@@ -212,9 +212,9 @@ private def elabTParserMacroAux (prec lhsPrec e : Term) : TermElabM Syntax := do
   | `(dbg_trace $arg:term; $body)            => `(dbgTrace (toString $arg) fun _ => $body)
   | _                                        => Macro.throwUnsupported
 
-@[builtin_term_elab «sorry»] def elabSorry : TermElab := fun _ expectedType? => do
-  let type ← expectedType?.getDM mkFreshTypeMVar
-  mkLabeledSorry type (synthetic := false) (unique := true)
+@[builtin_term_elab «sorry»] def elabSorry : TermElab := fun stx expectedType? => do
+  let stxNew ← `(@sorryAx _ false) -- Remark: we use `@` to ensure `sorryAx` will not consume auto params
+  withMacroExpansion stx stxNew <| elabTerm stxNew expectedType?
 
 /-- Return syntax `Prod.mk elems[0] (Prod.mk elems[1] ... (Prod.mk elems[elems.size - 2] elems[elems.size - 1])))` -/
 partial def mkPairs (elems : Array Term) : MacroM Term :=

src/Lean/Elab/Extra.lean

@@ -581,7 +581,7 @@ def elabDefaultOrNonempty : TermElab :=  fun stx expectedType? => do
       else
         -- It is in the context of an `unsafe` constant. We can use sorry instead.
         -- Another option is to make a recursive application since it is unsafe.
-        mkLabeledSorry expectedType false (unique := true)
+        mkSorry expectedType false
 
 builtin_initialize
   registerTraceClass `Elab.binop

src/Lean/Elab/Frontend.lean

@@ -142,7 +142,6 @@ def runFrontend
     (trustLevel : UInt32 := 0)
     (ileanFileName? : Option String := none)
     (jsonOutput : Bool := false)
-    (errorOnKinds : Array Name := #[])
     : IO (Environment × Bool) := do
   let startTime := (← IO.monoNanosNow).toFloat / 1000000000
   let inputCtx := Parser.mkInputContext input fileName
@@ -151,8 +150,7 @@ def runFrontend
   let processor := Language.Lean.process
   let snap ← processor (fun _ => pure <| .ok { mainModuleName, opts, trustLevel }) none ctx
   let snaps := Language.toSnapshotTree snap
-  let severityOverrides := errorOnKinds.foldl (·.insert · .error) {}
-  let hasErrors ← snaps.runAndReport opts jsonOutput severityOverrides
+  snaps.runAndReport opts jsonOutput
 
   if let some ileanFileName := ileanFileName? then
     let trees := snaps.getAll.flatMap (match ·.infoTree? with | some t => #[t] | _ => #[])
@@ -170,6 +168,7 @@ def runFrontend
     let profile ← Firefox.Profile.export mainModuleName.toString startTime traceStates opts
     IO.FS.writeFile ⟨out⟩ <| Json.compress <| toJson profile
 
+  let hasErrors := snaps.getAll.any (·.diagnostics.msgLog.hasErrors)
   -- no point in freeing the snapshot graph and all referenced data this close to process exit
   Runtime.forget snaps
   pure (cmdState.env, !hasErrors)

src/Lean/Elab/GuardMsgs.lean

@@ -26,7 +26,7 @@ namespace Lean.Elab.Tactic.GuardMsgs
 
 /-- Gives a string representation of a message without source position information.
 Ensures the message ends with a '\n'. -/
-private def messageToStringWithoutPos (msg : Message) : BaseIO String := do
+private def messageToStringWithoutPos (msg : Message) : IO String := do
   let mut str ← msg.data.toString
   unless msg.caption == "" do
     str := msg.caption ++ ":\n" ++ str

src/Lean/Elab/InfoTree/Main.lean

@@ -192,12 +192,8 @@ def FVarAliasInfo.format (info : FVarAliasInfo) : Format :=
 def FieldRedeclInfo.format (ctx : ContextInfo) (info : FieldRedeclInfo) : Format :=
   f!"FieldRedecl @ {formatStxRange ctx info.stx}"
 
-def DelabTermInfo.format (ctx : ContextInfo) (info : DelabTermInfo) : IO Format := do
-  let loc := if let some loc := info.location? then f!"{loc.module} {loc.range.pos}-{loc.range.endPos}" else "none"
-  return f!"DelabTermInfo @ {← TermInfo.format ctx info.toTermInfo}\n\
-    Location: {loc}\n\
-    Docstring: {repr info.docString?}\n\
-    Explicit: {info.explicit}"
+def OmissionInfo.format (ctx : ContextInfo) (info : OmissionInfo) : IO Format := do
+  return f!"Omission @ {← TermInfo.format ctx info.toTermInfo}\nReason: {info.reason}"
 
 def ChoiceInfo.format (ctx : ContextInfo) (info : ChoiceInfo) : Format :=
   f!"Choice @ {formatElabInfo ctx info.toElabInfo}"
@@ -215,7 +211,7 @@ def Info.format (ctx : ContextInfo) : Info → IO Format
   | ofCustomInfo i         => pure <| Std.ToFormat.format i
   | ofFVarAliasInfo i      => pure <| i.format
   | ofFieldRedeclInfo i    => pure <| i.format ctx
-  | ofDelabTermInfo i      => i.format ctx
+  | ofOmissionInfo i       => i.format ctx
   | ofChoiceInfo i         => pure <| i.format ctx
 
 def Info.toElabInfo? : Info → Option ElabInfo
@@ -231,7 +227,7 @@ def Info.toElabInfo? : Info → Option ElabInfo
   | ofCustomInfo _         => none
   | ofFVarAliasInfo _      => none
   | ofFieldRedeclInfo _    => none
-  | ofDelabTermInfo i      => some i.toElabInfo
+  | ofOmissionInfo i       => some i.toElabInfo
   | ofChoiceInfo i         => some i.toElabInfo
 
 /--

src/Lean/Elab/InfoTree/Types.lean

@@ -5,7 +5,7 @@ Released under Apache 2.0 license as described in the file LICENSE.
 Authors: Wojciech Nawrocki, Leonardo de Moura, Sebastian Ullrich
 -/
 prelude
-import Lean.Data.DeclarationRange
+import Lean.Data.Position
 import Lean.Data.OpenDecl
 import Lean.MetavarContext
 import Lean.Environment
@@ -168,22 +168,14 @@ structure FieldRedeclInfo where
   stx : Syntax
 
 /--
-Denotes TermInfo with additional configurations to control interactions with delaborated terms.
-
-For example, the omission term `⋯` that is emitted by the delaborator when omitting a term
-due to `pp.deepTerms false` or `pp.proofs false` uses this.
-Omission needs to be treated differently from regular terms because
+Denotes information for the term `⋯` that is emitted by the delaborator when omitting a term
+due to `pp.deepTerms false` or `pp.proofs false`. Omission needs to be treated differently from regular terms because
 it has to be delaborated differently in `Lean.Widget.InteractiveDiagnostics.infoToInteractive`:
 Regular terms are delaborated explicitly, whereas omitted terms are simply to be expanded with
-regular delaboration settings. Additionally, omissions come with a reason for omission.
+regular delaboration settings.
 -/
-structure DelabTermInfo extends TermInfo where
-  /-- A source position to use for "go to definition", to override the default. -/
-  location? : Option DeclarationLocation := none
-  /-- Text to use to override the docstring. -/
-  docString? : Option String := none
-  /-- Whether to use explicit mode when pretty printing the term on hover. -/
-  explicit : Bool := true
+structure OmissionInfo extends TermInfo where
+  reason : String
 
 /--
 Indicates that all overloaded elaborators failed. The subtrees of a `ChoiceInfo` node are the
@@ -206,7 +198,7 @@ inductive Info where
   | ofCustomInfo (i : CustomInfo)
   | ofFVarAliasInfo (i : FVarAliasInfo)
   | ofFieldRedeclInfo (i : FieldRedeclInfo)
-  | ofDelabTermInfo (i : DelabTermInfo)
+  | ofOmissionInfo (i : OmissionInfo)
   | ofChoiceInfo (i : ChoiceInfo)
   deriving Inhabited
 

src/Lean/Elab/MutualDef.lean

@@ -1007,7 +1007,7 @@ where
             values.mapM (instantiateMVarsProfiling ·)
           catch ex =>
             logException ex
-            headers.mapM fun header => withRef header.declId <| mkLabeledSorry header.type (synthetic := true) (unique := true)
+            headers.mapM fun header => mkSorry header.type (synthetic := true)
         let headers ← headers.mapM instantiateMVarsAtHeader
         let letRecsToLift ← getLetRecsToLift
         let letRecsToLift ← letRecsToLift.mapM instantiateMVarsAtLetRecToLift

src/Lean/Elab/PatternVar.lean

@@ -159,7 +159,7 @@ private def processVar (idStx : Syntax) : M Syntax := do
 private def samePatternsVariables (startingAt : Nat) (s₁ s₂ : State) : Bool := Id.run do
   if h₁ : s₁.vars.size = s₂.vars.size then
     for h₂ : i in [startingAt:s₁.vars.size] do
-      if s₁.vars[i] != s₂.vars[i]'(by obtain ⟨_, y⟩ := h₂; simp_all +zetaDelta) then return false
+      if s₁.vars[i] != s₂.vars[i]'(by obtain ⟨_, y⟩ := h₂; simp_all) then return false
     true
   else
     false

src/Lean/Elab/PreDefinition/Basic.lean

@@ -9,6 +9,7 @@ import Lean.Compiler.NoncomputableAttr
 import Lean.Util.CollectLevelParams
 import Lean.Util.NumObjs
 import Lean.Util.NumApps
+import Lean.PrettyPrinter
 import Lean.Meta.AbstractNestedProofs
 import Lean.Meta.ForEachExpr
 import Lean.Meta.Eqns

src/Lean/Elab/PreDefinition/Main.lean

@@ -20,7 +20,7 @@ private def addAndCompilePartial (preDefs : Array PreDefinition) (useSorry := fa
     let all := preDefs.toList.map (·.declName)
     forallTelescope preDef.type fun xs type => do
       let value ← if useSorry then
-        mkLambdaFVars xs (← withRef preDef.ref <| mkLabeledSorry type (synthetic := true) (unique := true))
+        mkLambdaFVars xs (← mkSorry type (synthetic := true))
       else
         let msg := m!"failed to compile 'partial' definition '{preDef.declName}'"
         liftM <| mkInhabitantFor msg xs type
@@ -115,7 +115,7 @@ private partial def ensureNoUnassignedLevelMVarsAtPreDef (preDef : PreDefinition
 private def ensureNoUnassignedMVarsAtPreDef (preDef : PreDefinition) : TermElabM PreDefinition := do
   let pendingMVarIds ← getMVarsAtPreDef preDef
   if (← logUnassignedUsingErrorInfos pendingMVarIds) then
-    let preDef := { preDef with value := (← withRef preDef.ref <| mkLabeledSorry preDef.type (synthetic := true) (unique := true)) }
+    let preDef := { preDef with value := (← mkSorry preDef.type (synthetic := true)) }
     if (← getMVarsAtPreDef preDef).isEmpty then
       return preDef
     else

src/Lean/Elab/Tactic/Basic.lean

@@ -14,7 +14,7 @@ open Meta
 def admitGoal (mvarId : MVarId) : MetaM Unit :=
   mvarId.withContext do
     let mvarType ← inferType (mkMVar mvarId)
-    mvarId.assign (← mkLabeledSorry mvarType (synthetic := true) (unique := true))
+    mvarId.assign (← mkSorry mvarType (synthetic := true))
 
 def goalsToMessageData (goals : List MVarId) : MessageData :=
   MessageData.joinSep (goals.map MessageData.ofGoal) m!"\n\n"

src/Lean/Elab/Tactic/LibrarySearch.lean

@@ -70,7 +70,7 @@ def elabExact?Term : TermElab := fun stx expectedType? => do
       if let some suggestions ← librarySearch introdGoal then
         if suggestions.isEmpty then logError "`exact?%` didn't find any relevant lemmas"
         else logError "`exact?%` could not close the goal. Try `by apply` to see partial suggestions."
-        mkLabeledSorry expectedType (synthetic := true) (unique := true)
+        mkSorry expectedType (synthetic := true)
       else
         addTermSuggestion stx (← instantiateMVars goal).headBeta
         instantiateMVars goal

src/Lean/Elab/Tactic/Simp.lean

@@ -173,71 +173,68 @@ def elabSimpArgs (stx : Syntax) (ctx : Simp.Context) (simprocs : Simp.SimprocsAr
     syntax simpErase := "-" ident
     -/
     let go := withMainContext do
-      let zetaDeltaSet ← toZetaDeltaSet stx ctx
-      withTrackingZetaDeltaSet zetaDeltaSet do
-        let mut thmsArray := ctx.simpTheorems
-        let mut thms      := thmsArray[0]!
-        let mut simprocs  := simprocs
-        let mut starArg   := false
-        for arg in stx[1].getSepArgs do
-          try -- like withLogging, but compatible with do-notation
-            if arg.getKind == ``Lean.Parser.Tactic.simpErase then
-              let fvar? ← if eraseLocal || starArg then Term.isLocalIdent? arg[1] else pure none
-              if let some fvar := fvar? then
-                -- We use `eraseCore` because the simp theorem for the hypothesis was not added yet
-                thms := thms.eraseCore (.fvar fvar.fvarId!)
+      let mut thmsArray := ctx.simpTheorems
+      let mut thms      := thmsArray[0]!
+      let mut simprocs  := simprocs
+      let mut starArg   := false
+      for arg in stx[1].getSepArgs do
+        try -- like withLogging, but compatible with do-notation
+          if arg.getKind == ``Lean.Parser.Tactic.simpErase then
+            let fvar? ← if eraseLocal || starArg then Term.isLocalIdent? arg[1] else pure none
+            if let some fvar := fvar? then
+              -- We use `eraseCore` because the simp theorem for the hypothesis was not added yet
+              thms := thms.eraseCore (.fvar fvar.fvarId!)
+            else
+              let id := arg[1]
+              if let .ok declName ← observing (realizeGlobalConstNoOverloadWithInfo id) then
+                if (← Simp.isSimproc declName) then
+                  simprocs := simprocs.erase declName
+                else if ctx.config.autoUnfold then
+                  thms := thms.eraseCore (.decl declName)
+                else
+                  thms ← withRef id <| thms.erase (.decl declName)
               else
-                let id := arg[1]
-                if let .ok declName ← observing (realizeGlobalConstNoOverloadWithInfo id) then
-                  if (← Simp.isSimproc declName) then
-                    simprocs := simprocs.erase declName
-                  else if ctx.config.autoUnfold then
-                    thms := thms.eraseCore (.decl declName)
-                  else
-                    thms ← withRef id <| thms.erase (.decl declName)
+                -- If `id` could not be resolved, we should check whether it is a builtin simproc.
+                -- before returning error.
+                let name := id.getId.eraseMacroScopes
+                if (← Simp.isBuiltinSimproc name) then
+                  simprocs := simprocs.erase name
                 else
-                  -- If `id` could not be resolved, we should check whether it is a builtin simproc.
-                  -- before returning error.
-                  let name := id.getId.eraseMacroScopes
-                  if (← Simp.isBuiltinSimproc name) then
-                    simprocs := simprocs.erase name
-                  else
-                    withRef id <| throwUnknownConstant name
-            else if arg.getKind == ``Lean.Parser.Tactic.simpLemma then
-              let post :=
-                if arg[0].isNone then
-                  true
-                else
-                  arg[0][0].getKind == ``Parser.Tactic.simpPost
-              let inv  := !arg[1].isNone
-              let term := arg[2]
-              match (← resolveSimpIdTheorem? term) with
-              | .expr e  =>
-                let name ← mkFreshId
-                thms ← addDeclToUnfoldOrTheorem ctx.indexConfig thms (.stx name arg) e post inv kind
-              | .simproc declName =>
-                simprocs ← simprocs.add declName post
-              | .ext (some ext₁) (some ext₂) _ =>
-                thmsArray := thmsArray.push (← ext₁.getTheorems)
-                simprocs  := simprocs.push (← ext₂.getSimprocs)
-              | .ext (some ext₁) none _ =>
-                thmsArray := thmsArray.push (← ext₁.getTheorems)
-              | .ext none (some ext₂) _ =>
-                simprocs  := simprocs.push (← ext₂.getSimprocs)
-              | .none    =>
-                let name ← mkFreshId
-                thms ← addSimpTheorem ctx.indexConfig thms (.stx name arg) term post inv
-            else if arg.getKind == ``Lean.Parser.Tactic.simpStar then
-              starArg := true
-            else
-              throwUnsupportedSyntax
-          catch ex =>
-            if (← read).recover then
-              logException ex
-            else
-              throw ex
-        let ctx := ctx.setZetaDeltaSet zetaDeltaSet (← getZetaDeltaFVarIds)
-        return { ctx := ctx.setSimpTheorems (thmsArray.set! 0 thms), simprocs, starArg }
+                  withRef id <| throwUnknownConstant name
+          else if arg.getKind == ``Lean.Parser.Tactic.simpLemma then
+            let post :=
+              if arg[0].isNone then
+                true
+              else
+                arg[0][0].getKind == ``Parser.Tactic.simpPost
+            let inv  := !arg[1].isNone
+            let term := arg[2]
+            match (← resolveSimpIdTheorem? term) with
+            | .expr e  =>
+              let name ← mkFreshId
+              thms ← addDeclToUnfoldOrTheorem ctx.indexConfig thms (.stx name arg) e post inv kind
+            | .simproc declName =>
+              simprocs ← simprocs.add declName post
+            | .ext (some ext₁) (some ext₂) _ =>
+              thmsArray := thmsArray.push (← ext₁.getTheorems)
+              simprocs  := simprocs.push (← ext₂.getSimprocs)
+            | .ext (some ext₁) none _ =>
+              thmsArray := thmsArray.push (← ext₁.getTheorems)
+            | .ext none (some ext₂) _ =>
+              simprocs  := simprocs.push (← ext₂.getSimprocs)
+            | .none    =>
+              let name ← mkFreshId
+              thms ← addSimpTheorem ctx.indexConfig thms (.stx name arg) term post inv
+          else if arg.getKind == ``Lean.Parser.Tactic.simpStar then
+            starArg := true
+          else
+            throwUnsupportedSyntax
+        catch ex =>
+          if (← read).recover then
+            logException ex
+          else
+            throw ex
+      return { ctx := ctx.setSimpTheorems (thmsArray.set! 0 thms), simprocs, starArg }
     -- If recovery is disabled, then we want simp argument elaboration failures to be exceptions.
     -- This affects `addSimpTheorem`.
     if (← read).recover then
@@ -280,20 +277,6 @@ where
       else
         return .none
 
-  /-- If `zetaDelta := false`, create a `FVarId` set with all local let declarations in the `simp` argument list. -/
-  toZetaDeltaSet (stx : Syntax) (ctx : Simp.Context) : TacticM FVarIdSet := do
-    if ctx.config.zetaDelta then return {}
-    Term.withoutCheckDeprecated do -- We do not want to report deprecated constants in the first pass
-      let mut s : FVarIdSet := {}
-      for arg in stx[1].getSepArgs do
-        if arg.getKind == ``Lean.Parser.Tactic.simpLemma then
-          if arg[0].isNone && arg[1].isNone then
-            let term := arg[2]
-            let .expr (.fvar fvarId) ← resolveSimpIdTheorem? term | pure ()
-            if (← fvarId.getDecl).isLet then
-              s := s.insert fvarId
-      return s
-
 @[inline] def simpOnlyBuiltins : List Name := [``eq_self, ``iff_self]
 
 structure MkSimpContextResult where
@@ -340,7 +323,7 @@ def mkSimpContext (stx : Syntax) (eraseLocal : Bool) (kind := SimpKind.simp)
     let simprocs := r.simprocs
     let mut simpTheorems := ctx.simpTheorems
     /-
-    When using `zetaDelta := false`, we do not expand let-declarations when using `[*]`.
+    When using `zeta := false`, we do not expand let-declarations when using `[*]`.
     Users must explicitly include it in the list.
     -/
     let hs ← getPropHyps

src/Lean/Elab/Tactic/SimpTrace.lean

@@ -22,10 +22,10 @@ def mkSimpCallStx (stx : Syntax) (usedSimps : UsedSimps) : MetaM (TSyntax `tacti
   let stx := stx.unsetTrailing
   mkSimpOnly stx usedSimps
 
-@[builtin_tactic simpTrace] def evalSimpTrace : Tactic := fun stx => withMainContext do withSimpDiagnostics do
+@[builtin_tactic simpTrace] def evalSimpTrace : Tactic := fun stx =>
   match stx with
   | `(tactic|
-      simp?%$tk $[!%$bang]? $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]? $(loc)?) =>
+      simp?%$tk $[!%$bang]? $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]? $(loc)?) => withMainContext do withSimpDiagnostics do
     let stx ← if bang.isSome then
       `(tactic| simp!%$tk $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]? $(loc)?)
     else
@@ -39,9 +39,9 @@ def mkSimpCallStx (stx : Syntax) (usedSimps : UsedSimps) : MetaM (TSyntax `tacti
     return stats.diag
   | _ => throwUnsupportedSyntax
 
-@[builtin_tactic simpAllTrace] def evalSimpAllTrace : Tactic := fun stx => withMainContext do withSimpDiagnostics do
+@[builtin_tactic simpAllTrace] def evalSimpAllTrace : Tactic := fun stx =>
   match stx with
-  | `(tactic| simp_all?%$tk $[!%$bang]? $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]?) =>
+  | `(tactic| simp_all?%$tk $[!%$bang]? $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]?) => withSimpDiagnostics do
     let stx ← if bang.isSome then
       `(tactic| simp_all!%$tk $cfg:optConfig $(discharger)? $[only%$o]? $[[$args,*]]?)
     else
@@ -79,9 +79,9 @@ where
     | some mvarId => replaceMainGoal [mvarId]
     pure stats
 
-@[builtin_tactic dsimpTrace] def evalDSimpTrace : Tactic := fun stx => withMainContext do withSimpDiagnostics do
+@[builtin_tactic dsimpTrace] def evalDSimpTrace : Tactic := fun stx =>
   match stx with
-  | `(tactic| dsimp?%$tk $[!%$bang]? $cfg:optConfig $[only%$o]? $[[$args,*]]? $(loc)?) =>
+  | `(tactic| dsimp?%$tk $[!%$bang]? $cfg:optConfig $[only%$o]? $[[$args,*]]? $(loc)?) => withSimpDiagnostics do
     let stx ← if bang.isSome then
       `(tactic| dsimp!%$tk $cfg:optConfig $[only%$o]? $[[$args,*]]? $(loc)?)
     else

src/Lean/Elab/Term.lean

@@ -326,10 +326,6 @@ structure Context where
   `refine' (fun x => _)
   -/
   holesAsSyntheticOpaque : Bool := false
-  /--
-  If `checkDeprecated := true`, then `Linter.checkDeprecated` when creating constants.
-  -/
-  checkDeprecated : Bool := true
 
 abbrev TermElabM := ReaderT Context $ StateRefT State MetaM
 abbrev TermElab  := Syntax → Option Expr → TermElabM Expr
@@ -1158,7 +1154,7 @@ private def mkSyntheticSorryFor (expectedType? : Option Expr) : TermElabM Expr :
   let expectedType ← match expectedType? with
     | none              => mkFreshTypeMVar
     | some expectedType => pure expectedType
-  mkLabeledSorry expectedType (synthetic := true) (unique := false)
+  mkSyntheticSorry expectedType
 
 /--
   Log the given exception, and create a synthetic sorry for representing the failed
@@ -1264,7 +1260,7 @@ The `tacticCode` syntax is the full `by ..` syntax.
 -/
 def mkTacticMVar (type : Expr) (tacticCode : Syntax) (kind : TacticMVarKind) : TermElabM Expr := do
   if ← pure (debug.byAsSorry.get (← getOptions)) <&&> isProp type then
-    withRef tacticCode <| mkLabeledSorry type false (unique := true)
+    mkSorry type false
   else
     let mvar ← mkFreshExprMVar type MetavarKind.syntheticOpaque
     let mvarId := mvar.mvarId!
@@ -1855,7 +1851,7 @@ def elabTermEnsuringType (stx : Syntax) (expectedType? : Option Expr) (catchExPo
     withRef stx <| ensureHasType expectedType? e errorMsgHeader?
   catch ex =>
     if (← read).errToSorry && ex matches .error .. then
-      withRef stx <| exceptionToSorry ex expectedType?
+      exceptionToSorry ex expectedType?
     else
       throw ex
 
@@ -2030,10 +2026,6 @@ def isLetRecAuxMVar (mvarId : MVarId) : TermElabM Bool := do
   trace[Elab.letrec] "mvarId root: {mkMVar mvarId}"
   return (← get).letRecsToLift.any (·.mvarId == mvarId)
 
-private def checkDeprecatedCore (constName : Name) : TermElabM Unit := do
-  if (← read).checkDeprecated then
-    Linter.checkDeprecated constName
-
 /--
   Create an `Expr.const` using the given name and explicit levels.
   Remark: fresh universe metavariables are created if the constant has more universe
@@ -2041,8 +2033,9 @@ private def checkDeprecatedCore (constName : Name) : TermElabM Unit := do
 
   If `checkDeprecated := true`, then `Linter.checkDeprecated` is invoked.
 -/
-def mkConst (constName : Name) (explicitLevels : List Level := []) : TermElabM Expr := do
-  checkDeprecatedCore constName
+def mkConst (constName : Name) (explicitLevels : List Level := []) (checkDeprecated := true) : TermElabM Expr := do
+  if checkDeprecated then
+    Linter.checkDeprecated constName
   let cinfo ← getConstInfo constName
   if explicitLevels.length > cinfo.levelParams.length then
     throwError "too many explicit universe levels for '{constName}'"
@@ -2053,10 +2046,7 @@ def mkConst (constName : Name) (explicitLevels : List Level := []) : TermElabM E
 
 def checkDeprecated (ref : Syntax) (e : Expr) : TermElabM Unit := do
   if let .const declName _ := e.getAppFn then
-    withRef ref do checkDeprecatedCore declName
-
-@[inline] def withoutCheckDeprecated [MonadWithReaderOf Context m] : m α → m α :=
-  withTheReader Context (fun ctx => { ctx with checkDeprecated := false })
+    withRef ref do Linter.checkDeprecated declName
 
 private def mkConsts (candidates : List (Name × List String)) (explicitLevels : List Level) : TermElabM (List (Expr × List String)) := do
   candidates.foldlM (init := []) fun result (declName, projs) => do
@@ -2068,7 +2058,7 @@ private def mkConsts (candidates : List (Name × List String)) (explicitLevels :
     At `elabAppFnId`, we perform the check when converting the list returned by `resolveName'` into a list of
     `TermElabResult`s.
     -/
-    let const ← withoutCheckDeprecated <| mkConst declName explicitLevels
+    let const ← mkConst declName explicitLevels (checkDeprecated := false)
     return (const, projs) :: result
 
 def resolveName (stx : Syntax) (n : Name) (preresolved : List Syntax.Preresolved) (explicitLevels : List Level) (expectedType? : Option Expr := none) : TermElabM (List (Expr × List String)) := do

src/Lean/Language/Basic.lean

@@ -262,16 +262,6 @@ instance : Inhabited DynamicSnapshot where
     f element
     children.forM (·.get.forM f)
 
-/--
-  Runs a tree of snapshots to conclusion,
-  folding the function `f` over each snapshot in tree preorder. -/
-@[specialize] partial def SnapshotTree.foldM [Monad m] (s : SnapshotTree)
-    (f : α → Snapshot → m α) (init : α) : m α := do
-  match s with
-  | mk element children =>
-    let a ← f init element
-    children.foldlM (fun a snap => snap.get.foldM f a) a
-
 /--
   Option for printing end position of each message in addition to start position. Used for testing
   message ranges in the test suite. -/
@@ -279,43 +269,24 @@ register_builtin_option printMessageEndPos : Bool := {
   defValue := false, descr := "print end position of each message in addition to start position"
 }
 
-/--
-Reports messages on stdout and returns whether an error was reported.
-If `json` is true, prints messages as JSON (one per line).
-If a message's kind is in `severityOverrides`, it will be reported with
-the specified severity.
--/
-def reportMessages (msgLog : MessageLog) (opts : Options)
-    (json := false) (severityOverrides : NameMap MessageSeverity := {}) : IO Bool := do
-  let includeEndPos := printMessageEndPos.get opts
-  msgLog.unreported.foldlM (init := false) fun hasErrors msg => do
-    let msg : Message :=
-      if let some severity := severityOverrides.find? msg.kind then
-        {msg with severity}
-      else
-        msg
-    if json then
-      let j ← msg.toJson
-      IO.println j.compress
-    else
-      let s ← msg.toString includeEndPos
-      IO.print s
-    return hasErrors || msg.severity matches .error
+/-- Reports messages on stdout. If `json` is true, prints messages as JSON (one per line). -/
+def reportMessages (msgLog : MessageLog) (opts : Options) (json := false) : IO Unit := do
+  if json then
+    msgLog.forM (·.toJson <&> (·.compress) >>= IO.println)
+  else
+    msgLog.forM (·.toString (includeEndPos := printMessageEndPos.get opts) >>= IO.print)
 
 /--
   Runs a tree of snapshots to conclusion and incrementally report messages on stdout. Messages are
-  reported in tree preorder. Returns whether any errors were reported.
+  reported in tree preorder.
   This function is used by the cmdline driver; see `Lean.Server.FileWorker.reportSnapshots` for how
   the language server reports snapshots asynchronously.  -/
-def SnapshotTree.runAndReport (s : SnapshotTree) (opts : Options)
-    (json := false) (severityOverrides : NameMap MessageSeverity := {}) : IO Bool := do
-  s.foldM (init := false) fun e snap => do
-    let e' ← reportMessages snap.diagnostics.msgLog opts json severityOverrides
-    return strictOr e e'
+def SnapshotTree.runAndReport (s : SnapshotTree) (opts : Options) (json := false) : IO Unit := do
+  s.forM (reportMessages ·.diagnostics.msgLog opts json)
 
 /-- Waits on and returns all snapshots in the tree. -/
 def SnapshotTree.getAll (s : SnapshotTree) : Array Snapshot :=
-  Id.run <| s.foldM (·.push ·) #[]
+  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)

src/Lean/LocalContext.lean

@@ -42,15 +42,16 @@ inductive LocalDeclKind
   | auxDecl
   deriving Inhabited, Repr, DecidableEq, Hashable
 
-/-- A declaration for a `LocalContext`. This is used to register which free variables are in scope.
-
-See `LocalDecl.index`, `LocalDecl.fvarId`, `LocalDecl.userName`, `LocalDecl.type` for accessors for
-arguments common to both constructors.
+/-- A declaration for a LocalContext. This is used to register which free variables are in scope.
+Each declaration comes with
+- `index` the position of the decl in the local context
+- `fvarId` the unique id of the free variables
+- `userName` the pretty-printable name of the variable
+- `type` the type.
+A `cdecl` is a local variable, a `ldecl` is a let-bound free variable with a `value : Expr`.
 -/
 inductive LocalDecl where
-  /-- A local variable. -/
   | cdecl (index : Nat) (fvarId : FVarId) (userName : Name) (type : Expr) (bi : BinderInfo) (kind : LocalDeclKind)
-  /-- A let-bound free variable, with a `value : Expr`. -/
   | ldecl (index : Nat) (fvarId : FVarId) (userName : Name) (type : Expr) (value : Expr) (nonDep : Bool) (kind : LocalDeclKind)
   deriving Inhabited
 
@@ -70,7 +71,6 @@ def isLet : LocalDecl → Bool
   | cdecl .. => false
   | ldecl .. => true
 
-/-- The position of the decl in the local context. -/
 def index : LocalDecl → Nat
   | cdecl (index := i) .. => i
   | ldecl (index := i) .. => i
@@ -79,17 +79,14 @@ def setIndex : LocalDecl → Nat → LocalDecl
   | cdecl _  id n t bi k,   idx => cdecl idx id n t bi k
   | ldecl _  id n t v nd k, idx => ldecl idx id n t v nd k
 
-/-- The unique id of the free variable. -/
 def fvarId : LocalDecl → FVarId
   | cdecl (fvarId := id) .. => id
   | ldecl (fvarId := id) .. => id
 
-/-- The pretty-printable name of the variable. -/
 def userName : LocalDecl → Name
   | cdecl (userName := n) .. => n
   | ldecl (userName := n) .. => n
 
-/-- The type of the variable. -/
 def type : LocalDecl → Expr
   | cdecl (type := t) .. => t
   | ldecl (type := t) .. => t

src/Lean/Message.lean

@@ -91,7 +91,7 @@ inductive MessageData where
   If the thunked message is produced for a term that contains a synthetic sorry,
   `hasSyntheticSorry` should return `true`.
   This is used to filter out certain messages. -/
-  | ofLazy (f : Option PPContext → BaseIO Dynamic) (hasSyntheticSorry : MetavarContext → Bool)
+  | ofLazy (f : Option PPContext → IO Dynamic) (hasSyntheticSorry : MetavarContext → Bool)
   deriving Inhabited, TypeName
 
 namespace MessageData
@@ -103,7 +103,7 @@ def ofFormat (fmt : Format) : MessageData := .ofFormatWithInfos ⟨fmt, .empty
 Lazy message data production, with access to the context as given by
 a surrounding `MessageData.withContext` (which is expected to exist).
 -/
-def lazy (f : PPContext → BaseIO MessageData)
+def lazy (f : PPContext → IO MessageData)
     (hasSyntheticSorry : MetavarContext → Bool := fun _ => false) : MessageData :=
   .ofLazy (hasSyntheticSorry := hasSyntheticSorry) fun ctx? => do
     let msg ← match ctx? with
@@ -220,9 +220,9 @@ where
   | trace _ msg msgs        => visit mctx? msg || msgs.any (visit mctx?)
   | _                       => false
 
-partial def formatAux : NamingContext → Option MessageDataContext → MessageData → BaseIO Format
-  | _,    _,         ofFormatWithInfos fmt    => return fmt.1
-  | _,    none,      ofGoal mvarId            => return formatRawGoal mvarId
+partial def formatAux : NamingContext → Option MessageDataContext → MessageData → IO Format
+  | _, _,            ofFormatWithInfos fmt    => return fmt.1
+  | _,    none,      ofGoal mvarId            => return "goal " ++ format (mkMVar mvarId)
   | nCtx, some ctx,  ofGoal mvarId            => ppGoal (mkPPContext nCtx ctx) mvarId
   | nCtx, ctx,       ofWidget _ d             => formatAux nCtx ctx d
   | nCtx, _,         withContext ctx d        => formatAux nCtx ctx d
@@ -244,10 +244,10 @@ partial def formatAux : NamingContext → Option MessageDataContext → MessageD
       | panic! s!"MessageData.ofLazy: expected MessageData in Dynamic, got {dyn.typeName}"
     formatAux nCtx ctx? msg
 
-protected def format (msgData : MessageData) (ctx? : Option MessageDataContext := none) : BaseIO Format :=
+protected def format (msgData : MessageData) (ctx? : Option MessageDataContext := none) : IO Format :=
   formatAux { currNamespace := Name.anonymous, openDecls := [] } ctx? msgData
 
-protected def toString (msgData : MessageData) : BaseIO String := do
+protected def toString (msgData : MessageData) : IO String := do
   return toString (← msgData.format)
 
 instance : Append MessageData := ⟨compose⟩
@@ -374,14 +374,14 @@ namespace Message
   msg.data.kind
 
 /-- Serializes the message, converting its data into a string and saving its kind. -/
-@[inline] def serialize (msg : Message) : BaseIO SerialMessage := do
+@[inline] def serialize (msg : Message) : IO SerialMessage := do
   return {msg with kind := msg.kind, data := ← msg.data.toString}
 
-protected def toString (msg : Message) (includeEndPos := false) : BaseIO String := do
+protected def toString (msg : Message) (includeEndPos := false) : IO String := do
   -- Remark: The inline here avoids a new message allocation when `msg` is shared
   return inline <| (← msg.serialize).toString includeEndPos
 
-protected def toJson (msg : Message) : BaseIO Json := do
+protected def toJson (msg : Message) : IO Json := do
   -- Remark: The inline here avoids a new message allocation when `msg` is shared
   return inline <| toJson (← msg.serialize)
 
@@ -391,14 +391,23 @@ end Message
 A persistent array of messages.
 
 In the Lean elaborator, we use a fresh message log per command but may also report diagnostics at
-various points inside a command, which will empty `unreported` and move its messages to `reported`.
-Reported messages are preserved for some specific "lookback" operations such as `hasError` that
-should consider the entire message history of the current command; most other functions such as
-`add` and `toList` will only operate on unreported messages.
+various points inside a command, which will empty `unreported` and updated `hadErrors` accordingly
+(see `CoreM.getAndEmptyMessageLog`).
 -/
 structure MessageLog where
-  /-- The list of messages already reported (i.e. saved in a `Snapshot`), in insertion order. -/
-  reported : PersistentArray Message := {}
+  /--
+  If true, there was an error in the log previously that has already been reported to the user and
+  removed from the log. Thus we say that in the current context (usually the current command), we
+  "have errors" if either this flag is set or there is an error in `msgs`; see
+  `MessageLog.hasErrors`. If we have errors, we suppress some error messages that are often the
+  result of a previous error.
+  -/
+  /-
+  Design note: We considered introducing a `hasErrors` field instead that already includes the
+  presence of errors in `msgs` but this would not be compatible with e.g.
+  `MessageLog.errorsToWarnings`.
+  -/
+  hadErrors : Bool := false
   /-- The list of messages not already reported, in insertion order. -/
   unreported : PersistentArray Message := {}
   /--
@@ -407,7 +416,7 @@ structure MessageLog where
   the configuration option `exponentiation.threshold`.
   We don't produce a warning if the kind is already in the following set.
   -/
-  loggedKinds : NameSet := {}
+  reportedKinds : NameSet := {}
   deriving Inhabited
 
 namespace MessageLog
@@ -417,33 +426,24 @@ def empty : MessageLog := {}
 using `MessageLog.toList/toArray`" (since := "2024-05-22")]
 def msgs : MessageLog → PersistentArray Message := unreported
 
-def reportedPlusUnreported : MessageLog → PersistentArray Message
-  | { reported := r, unreported := u, .. } => r ++ u
-
 def hasUnreported (log : MessageLog) : Bool :=
   !log.unreported.isEmpty
 
 def add (msg : Message) (log : MessageLog) : MessageLog :=
   { log with unreported := log.unreported.push msg }
 
-protected def append (l₁ l₂ : MessageLog) : MessageLog where
-  reported := l₁.reported ++ l₂.reported
-  unreported := l₁.unreported ++ l₂.unreported
-  loggedKinds := l₁.loggedKinds.union l₂.loggedKinds
+protected def append (l₁ l₂ : MessageLog) : MessageLog :=
+  { hadErrors := l₁.hadErrors || l₂.hadErrors, unreported := l₁.unreported ++ l₂.unreported }
 
 instance : Append MessageLog :=
   ⟨MessageLog.append⟩
 
-/--
-Checks if either of `reported` or `unreported` contains an error, i.e. whether the current command
-has errored yet.
--/
 def hasErrors (log : MessageLog) : Bool :=
-  log.reported.any (·.severity matches .error) || log.unreported.any (·.severity matches .error)
+  log.hadErrors || log.unreported.any (·.severity matches .error)
 
-/-- Moves `unreported` messages to `reported`. -/
+/-- Clears unreported messages while preserving `hasErrors`. -/
 def markAllReported (log : MessageLog) : MessageLog :=
-  { log with unreported := {}, reported := log.reported ++ log.unreported }
+  { log with unreported := {}, hadErrors  := log.hasErrors }
 
 def errorsToWarnings (log : MessageLog) : MessageLog :=
   { unreported := log.unreported.map (fun m => match m.severity with | MessageSeverity.error => { m with severity := MessageSeverity.warning } | _ => m) }