feat: checkMaxShared (#12083)

This PR adds the debugging helper functions `Expr.checkMaxShared` and
`MVarId.checkMaxShared` to `Sym`, and fixes a bug when visiting
telescopes in `Sym.simp`.

src/Lean/Meta/Sym/Simp/Forall.lean

@@ -81,7 +81,7 @@ public def simpForall (e : Expr) : SimpM Result := do
   else if (← isProp e) then
     let n := getForallTelescopeSize e.bindingBody! 1
     forallBoundedTelescope e n fun xs b => withoutModifyingCacheIfNotWellBehaved do
-      main xs b
+      main xs (← share b)
   else
     return .rfl
 where
@@ -90,7 +90,7 @@ where
     | .rfl _ => return .rfl
     | .step b' h _ =>
       let h ← mkLambdaFVars xs h
-      let e' ← shareCommonInc (← mkForallFVars xs b')
+      let e' ← share (← mkForallFVars xs b')
       -- **Note**: consider caching the forall-congr theorems
       let hcongr ← mkForallCongrFor xs
       return .step e' (mkApp3 hcongr (← mkLambdaFVars xs b) (← mkLambdaFVars xs b') h)

src/Lean/Meta/Sym/Simp/Lambda.lean

@@ -48,14 +48,14 @@ def mkFunextFor (xs : Array Expr) (β : Expr) : MetaM Expr := do
 
 public def simpLambda (e : Expr) : SimpM Result := do
   lambdaTelescope e fun xs b => withoutModifyingCacheIfNotWellBehaved do
-    main xs b
+    main xs (← share b)
 where
   main (xs : Array Expr) (b : Expr) : SimpM Result := do
     match (← simp b) with
     | .rfl _ => return .rfl
     | .step b' h _ =>
       let h ← mkLambdaFVars xs h
-      let e' ← shareCommonInc (← mkLambdaFVars xs b')
+      let e' ← share (← mkLambdaFVars xs b')
       let funext ← getFunext xs b
       return .step e' (mkApp3 funext e e' h)
 

src/Lean/Meta/Sym/Util.lean

@@ -9,6 +9,7 @@ public import Lean.Meta.Sym.SymM
 public import Lean.Meta.Transform
 import Init.Grind.Util
 import Lean.Meta.WHNF
+import Lean.Util.ForEachExpr
 namespace Lean.Meta.Sym
 
 /--
@@ -91,4 +92,21 @@ public def preprocessMVar (mvarId : MVarId) : SymM MVarId := do
   mvarId.assign mvarNew
   return mvarNew.mvarId!
 
+/-- Debug helper: throws if any subexpression of `e` is not in the table of maximally shared terms. -/
+public def _root_.Lean.Expr.checkMaxShared (e : Expr) (msg := "") : SymM Unit := do
+  e.forEach fun e => do
+    if let some prev := (← get).share.set.find? { expr := e } then
+      unless isSameExpr prev.expr e do
+        throwNotMaxShared e
+    else
+      throwNotMaxShared e
+where
+  throwNotMaxShared (e : Expr) : SymM Unit := do
+    let msg := if msg == "" then msg else s!"[{msg}] "
+    throwError "{msg}term is not in the maximally shared table{indentExpr e}"
+
+/-- Debug helper: throws if any subexpression of the goal's target type is not in the table of maximally shared. -/
+public def _root_.Lean.MVarId.checkMaxShared (mvarId : MVarId) (msg := "") : SymM Unit := do
+  (← mvarId.getDecl).type.checkMaxShared msg
+
 end Lean.Meta.Sym