fix: grind using congr equation of private imported matcher (#11756)

This PR fixes an issue where `grind` fails when trying to unfold a
definition by pattern matching imported by `import all` (or from a
non-`module`).

Fixes #11715

---------

Co-authored-by: Sebastian Ullrich <sebasti@nullri.ch>

src/Lean/Meta/Match/MatchEqs.lean

@@ -245,17 +245,6 @@ where go baseName splitterName := withConfig (fun c => { c with etaStruct := .no
     let result := { eqnNames, splitterName, splitterMatchInfo }
     registerMatchEqns matchDeclName result
 
-/- We generate the equations and splitter on demand, and do not save them on .olean files. -/
-builtin_initialize matchCongrEqnsExt : EnvExtension (PHashMap Name (Array Name)) ←
-  -- Using `local` allows us to use the extension in `realizeConst` without specifying `replay?`.
-  -- The resulting state can still be accessed on the generated declarations using `.asyncEnv`;
-  -- see below
-  registerEnvExtension (pure {}) (asyncMode := .local)
-
-def registerMatchCongrEqns (matchDeclName : Name) (eqnNames : Array Name) : CoreM Unit := do
-  modifyEnv fun env => matchCongrEqnsExt.modifyState env fun map =>
-    map.insert matchDeclName eqnNames
-
 /--
 Generate the congruence equations for the given match auxiliary declaration.
 The congruence equations have a completely unrestricted left-hand side (arbitrary discriminants),
@@ -269,11 +258,14 @@ not always needed, so for now we live with the code duplication.
 -/
 @[export lean_get_congr_match_equations_for]
 def genMatchCongrEqnsImpl (matchDeclName : Name) : MetaM (Array Name) := do
-  let baseName := mkPrivateName (← getEnv) matchDeclName
-  let firstEqnName := .str baseName congrEqn1ThmSuffix
-  realizeConst matchDeclName firstEqnName (go baseName)
-  return matchCongrEqnsExt.getState (asyncMode := .async .asyncEnv) (asyncDecl := firstEqnName) (← getEnv) |>.find! matchDeclName
-where go baseName := withConfig (fun c => { c with etaStruct := .none }) do
+  let firstEqnName := matchDeclName.str congrEqn1ThmSuffix
+  realizeConst matchDeclName firstEqnName go
+  let some matchInfo ← getMatcherInfo? matchDeclName | throwError "`{matchDeclName}` is not a matcher function"
+  let mut thmNames := #[]
+  for i in *...matchInfo.numAlts do
+    thmNames := thmNames.push <|(matchDeclName.str congrEqnThmSuffixBase).appendIndexAfter (i+1)
+  return thmNames
+where go := withConfig (fun c => { c with etaStruct := .none }) do
   withConfig (fun c => { c with etaStruct := .none }) do
   let constInfo ← getConstInfo matchDeclName
   let us := constInfo.levelParams.map mkLevelParam
@@ -290,7 +282,7 @@ where go baseName := withConfig (fun c => { c with etaStruct := .none }) do
     let mut idx := 1
     for i in *...alts.size do
       let altInfo := matchInfo.altInfos[i]!
-      let thmName := (Name.str baseName congrEqnThmSuffixBase).appendIndexAfter idx
+      let thmName := (Name.str matchDeclName congrEqnThmSuffixBase).appendIndexAfter idx
       eqnNames := eqnNames.push thmName
       let notAlt ← do
         let alt := alts[i]!
@@ -333,26 +325,36 @@ where go baseName := withConfig (fun c => { c with etaStruct := .none }) do
           return notAlt
       notAlts := notAlts.push notAlt
       idx := idx + 1
-    registerMatchCongrEqns matchDeclName eqnNames
 
 builtin_initialize registerTraceClass `Meta.Match.matchEqs
 
-private def isMatchEqName? (env : Environment) (n : Name) : Option (Name × Bool) := do
+private def isMatchEqName? (env : Environment) (n : Name) : Option Name := do
   let .str p s := n | failure
-  guard <| isEqnReservedNameSuffix s || s == "splitter" || isCongrEqnReservedNameSuffix s
+  guard <| isEqnReservedNameSuffix s || s == "splitter"
   let p ← privateToUserName? p
   guard <| isMatcherCore env p
-  return (p, isCongrEqnReservedNameSuffix s)
+  return p
 
 builtin_initialize registerReservedNamePredicate (isMatchEqName? · · |>.isSome)
 
 builtin_initialize registerReservedNameAction fun name => do
-  let some (p, isGenEq) := isMatchEqName? (← getEnv) name |
+  let some p := isMatchEqName? (← getEnv) name |
     return false
-  if isGenEq then
-    let _ ← MetaM.run' <| genMatchCongrEqnsImpl p
-  else
-    let _ ← MetaM.run' <| getEquationsFor p
+  let _ ← MetaM.run' <| getEquationsForImpl p
+  return true
+
+private def isMatchCongrEqName? (env : Environment) (n : Name) : Option Name := do
+  let .str p s := n | failure
+  guard <| isCongrEqnReservedNameSuffix s
+  guard <| isMatcherCore env p
+  return p
+
+builtin_initialize registerReservedNamePredicate (isMatchCongrEqName? · · |>.isSome)
+
+builtin_initialize registerReservedNameAction fun name => do
+  let some p := isMatchCongrEqName? (← getEnv) name |
+    return false
+  let _ ← MetaM.run' <| genMatchCongrEqnsImpl p
   return true
 
 end Lean.Meta.Match

tests/lean/run/issue11211.lean

@@ -28,7 +28,7 @@ info: private def f.match_1.splitter.{u_1} : (motive : List Nat → Sort u_1)
 
 
 /--
-info: private theorem f.match_1.congr_eq_1.{u_1} : ∀ (motive : List Nat → Sort u_1) (xs : List Nat) (h_1 : Unit → motive [])
+info: theorem f.match_1.congr_eq_1.{u_1} : ∀ (motive : List Nat → Sort u_1) (xs : List Nat) (h_1 : Unit → motive [])
   (h_2 : (x : List Nat) → motive x),
   xs = [] →
     (match xs with

tests/pkg/module/Module/Basic.lean

@@ -544,3 +544,13 @@ Eq.refl five
 -/
 #guard_msgs in
 #print instA._proof_1
+
+/-- Setup for #11715. -/
+
+public structure OpOperand2 where
+  nextUse : Option Nat
+
+public def func (ctx : Nat) (operand : OpOperand2) : Nat :=
+  match operand.nextUse with
+  | none => ctx
+  | some nextPtr => ctx

tests/pkg/module/Module/ImportedAll.lean

@@ -2,7 +2,7 @@ module
 
 public import Module.Basic
 import all Module.Basic
-import Lean.CoreM
+import Lean
 
 /-! `import all` should import private information, privately. -/
 
@@ -160,3 +160,9 @@ error: Invalid `⟨...⟩` notation: Constructor for `StructWithPrivateField` is
 #guard_msgs in
 #with_exporting
 #check (⟨1⟩ : StructWithPrivateField)
+
+/-! #11715: `grind` should not fail to apply private matcher from imported module. -/
+
+attribute [local grind] func in
+theorem stmt1 : func ctx op = ctx := by
+  grind