fix: include local variable dot notation params in grind? suggestions

This PR fixes a bug where `grind?` suggestions would not include parameters
using local variable dot notation (e.g., `cs.getD_rightInvSeq` where `cs` is
a local variable). These parameters were incorrectly filtered out because
the code assumed all ident params resolve to global declarations. In fact,
local variable dot notation produces anchors that need the original term to
be loaded during replay, so they must be preserved in the suggestion.

Closes #12185

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/Lean/Elab/Tactic/Grind/Main.lean

@@ -348,15 +348,28 @@ def evalGrindTraceCore (stx : Syntax) (trace := true) (verbose := true) (useSorr
   let paramStxs := if let some params := params? then params.getElems else #[]
   -- Extract term parameters (non-ident params) to include in the suggestion.
   -- These are not tracked via E-matching, so we conservatively include them all.
-  -- Ident params resolve to global declarations and are tracked via E-matching.
+  -- Plain ident params that resolve to global declarations are tracked via E-matching.
+  -- But idents with local variable dot notation (e.g., `cs.getD_rightInvSeq` where `cs`
+  -- is a local variable) must be preserved because they produce anchors that need
+  -- the original term to be loaded during replay.
   -- Non-ident terms (like `show P by tac`) need to be preserved explicitly.
-  let termParamStxs : Array Grind.TParam := paramStxs.filter fun p =>
+  let termParamStxs : Array Grind.TParam ← paramStxs.filterM fun p => do
     match p with
-    | `(Parser.Tactic.grindParam| $[$_:grindMod]? $_:ident) => false
-    | `(Parser.Tactic.grindParam| ! $[$_:grindMod]? $_:ident) => false
-    | `(Parser.Tactic.grindParam| - $_:ident) => false
-    | `(Parser.Tactic.grindParam| #$_:hexnum) => false
-    | _ => true
+    | `(Parser.Tactic.grindParam| $[$_:grindMod]? $id:ident) =>
+      -- Check if this ident resolves to local variable dot notation
+      -- If so, keep it because it's not a simple global declaration
+      if let some (_, _ :: _) := (← resolveLocalName id.getId) then
+        return true
+      else
+        return false
+    | `(Parser.Tactic.grindParam| ! $[$_:grindMod]? $id:ident) =>
+      if let some (_, _ :: _) := (← resolveLocalName id.getId) then
+        return true
+      else
+        return false
+    | `(Parser.Tactic.grindParam| - $_:ident) => return false
+    | `(Parser.Tactic.grindParam| #$_:hexnum) => return false
+    | _ => return true
   let mvarId ← getMainGoal
   let params ← mkGrindParams config only paramStxs mvarId
   Grind.withProtectedMCtx config mvarId fun mvarId' => do

tests/lean/run/grind_trace_local_dot_notation.lean

@@ -0,0 +1,32 @@
+/-!
+# Test that `grind?` includes local variable dot notation params in its suggestion
+
+When a user provides a parameter like `s.myThm` where `s` is a local variable
+and `myThm` is a field access, it should be included in the suggestion.
+These params are processed as term params (not global decls) and produce anchors.
+Without including the original term in the suggestion, the anchor can't match on replay.
+
+Regression test for: grind? suggestions not working with local variable dot notation
+-/
+set_option linter.unusedVariables false
+
+structure MyStruct where
+  val : Nat
+
+-- A theorem with an indexable pattern
+theorem MyStruct.add_comm (s : MyStruct) (a b : Nat) : a + b = b + a := Nat.add_comm a b
+
+-- Test: Local variable dot notation should be included in the suggestion
+-- `s.add_comm` is a local variable dot notation (not a global decl),
+-- so it should appear in the grind only suggestion
+/--
+info: Try this:
+  [apply] grind only [= s.add_comm]
+-/
+#guard_msgs in
+example (s : MyStruct) : (1 : Nat) + 2 = 2 + 1 := by
+  grind? [= s.add_comm]
+
+-- Verify the suggestion works by using it
+example (s : MyStruct) : (1 : Nat) + 2 = 2 + 1 := by
+  grind only [= s.add_comm]