1 files changed, 152 insertions, 42 deletions

diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index 7c68e4d9145..7ea3c8f8341 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -7580,15 +7580,22 @@ class TransformTypos : public TreeTransform<TransformTypos> {
   llvm::SmallDenseMap<OverloadExpr *, Expr *, 4> OverloadResolution;
 
   /// Emit diagnostics for all of the TypoExprs encountered.
+  ///
   /// If the TypoExprs were successfully corrected, then the diagnostics should
   /// suggest the corrections. Otherwise the diagnostics will not suggest
   /// anything (having been passed an empty TypoCorrection).
-  void EmitAllDiagnostics() {
+  ///
+  /// If we've failed to correct due to ambiguous corrections, we need to
+  /// be sure to pass empty corrections and replacements. Otherwise it's
+  /// possible that the Consumer has a TypoCorrection that failed to ambiguity
+  /// and we don't want to report those diagnostics.
+  void EmitAllDiagnostics(bool IsAmbiguous) {
     for (TypoExpr *TE : TypoExprs) {
       auto &State = SemaRef.getTypoExprState(TE);
       if (State.DiagHandler) {
-        TypoCorrection TC = State.Consumer->getCurrentCorrection();
-        ExprResult Replacement = TransformCache[TE];
+        TypoCorrection TC = IsAmbiguous
+            ? TypoCorrection() : State.Consumer->getCurrentCorrection();
+        ExprResult Replacement = IsAmbiguous ? ExprError() : TransformCache[TE];
 
         // Extract the NamedDecl from the transformed TypoExpr and add it to the
         // TypoCorrection, replacing the existing decls. This ensures the right
@@ -7650,6 +7657,145 @@ class TransformTypos : public TreeTransform<TransformTypos> {
     return ExprFilter(Res.get());
   }
 
+  // Since correcting typos may intoduce new TypoExprs, this function
+  // checks for new TypoExprs and recurses if it finds any. Note that it will
+  // only succeed if it is able to correct all typos in the given expression.
+  ExprResult CheckForRecursiveTypos(ExprResult Res, bool &IsAmbiguous) {
+    if (Res.isInvalid()) {
+      return Res;
+    }
+    // Check to see if any new TypoExprs were created. If so, we need to recurse
+    // to check their validity.
+    Expr *FixedExpr = Res.get();
+
+    auto SavedTypoExprs = std::move(TypoExprs);
+    auto SavedAmbiguousTypoExprs = std::move(AmbiguousTypoExprs);
+    TypoExprs.clear();
+    AmbiguousTypoExprs.clear();
+
+    FindTypoExprs(TypoExprs).TraverseStmt(FixedExpr);
+    if (!TypoExprs.empty()) {
+      // Recurse to handle newly created TypoExprs. If we're not able to
+      // handle them, discard these TypoExprs.
+      ExprResult RecurResult =
+          RecursiveTransformLoop(FixedExpr, IsAmbiguous);
+      if (RecurResult.isInvalid()) {
+        Res = ExprError();
+        // Recursive corrections didn't work, wipe them away and don't add
+        // them to the TypoExprs set. Remove them from Sema's TypoExpr list
+        // since we don't want to clear them twice. Note: it's possible the
+        // TypoExprs were created recursively and thus won't be in our
+        // Sema's TypoExprs - they were created in our `RecursiveTransformLoop`.
+        auto &SemaTypoExprs = SemaRef.TypoExprs;
+        for (auto TE : TypoExprs) {
+          TransformCache.erase(TE);
+          SemaRef.clearDelayedTypo(TE);
+
+          auto SI = find(SemaTypoExprs, TE);
+          if (SI != SemaTypoExprs.end()) {
+            SemaTypoExprs.erase(SI);
+          }
+        }
+      } else {
+        // TypoExpr is valid: add newly created TypoExprs since we were
+        // able to correct them.
+        Res = RecurResult;
+        SavedTypoExprs.set_union(TypoExprs);
+      }
+    }
+
+    TypoExprs = std::move(SavedTypoExprs);
+    AmbiguousTypoExprs = std::move(SavedAmbiguousTypoExprs);
+
+    return Res;
+  }
+
+  // Try to transform the given expression, looping through the correction
+  // candidates with `CheckAndAdvanceTypoExprCorrectionStreams`.
+  //
+  // If valid ambiguous typo corrections are seen, `IsAmbiguous` is set to
+  // true and this method immediately will return an `ExprError`.
+  ExprResult RecursiveTransformLoop(Expr *E, bool &IsAmbiguous) {
+    ExprResult Res;
+    auto SavedTypoExprs = std::move(SemaRef.TypoExprs);
+    SemaRef.TypoExprs.clear();
+
+    while (true) {
+      Res = CheckForRecursiveTypos(TryTransform(E), IsAmbiguous);
+
+      // Recursion encountered an ambiguous correction. This means that our
+      // correction itself is ambiguous, so stop now.
+      if (IsAmbiguous)
+        break;
+
+      // If the transform is still valid after checking for any new typos,
+      // it's good to go.
+      if (!Res.isInvalid())
+        break;
+
+      // The transform was invalid, see if we have any TypoExprs with untried
+      // correction candidates.
+      if (!CheckAndAdvanceTypoExprCorrectionStreams())
+        break;
+    }
+
+    // If we found a valid result, double check to make sure it's not ambiguous.
+    if (!IsAmbiguous && !Res.isInvalid() && !AmbiguousTypoExprs.empty()) {
+      auto SavedTransformCache = std::move(TransformCache);
+      TransformCache.clear();
+      // Ensure none of the TypoExprs have multiple typo correction candidates
+      // with the same edit length that pass all the checks and filters.
+      while (!AmbiguousTypoExprs.empty()) {
+        auto TE  = AmbiguousTypoExprs.back();
+
+        // TryTransform itself can create new Typos, adding them to the TypoExpr map
+        // and invalidating our TypoExprState, so always fetch it instead of storing.
+        SemaRef.getTypoExprState(TE).Consumer->saveCurrentPosition();
+
+        TypoCorrection TC = SemaRef.getTypoExprState(TE).Consumer->peekNextCorrection();
+        TypoCorrection Next;
+        do {
+          ExprResult AmbigRes = CheckForRecursiveTypos(TryTransform(E), IsAmbiguous);
+
+          if (!AmbigRes.isInvalid() || IsAmbiguous) {
+            SemaRef.getTypoExprState(TE).Consumer->resetCorrectionStream();
+            SavedTransformCache.erase(TE);
+            Res = ExprError();
+            IsAmbiguous = true;
+            break;
+          }
+        } while ((Next = SemaRef.getTypoExprState(TE).Consumer->peekNextCorrection()) &&
+                 Next.getEditDistance(false) == TC.getEditDistance(false));
+
+        if (IsAmbiguous)
+          break;
+
+        AmbiguousTypoExprs.remove(TE);
+        SemaRef.getTypoExprState(TE).Consumer->restoreSavedPosition();
+      }
+      TransformCache = std::move(SavedTransformCache);
+    }
+
+    // Wipe away any newly created TypoExprs that we don't know about. Since we
+    // clear any invalid TypoExprs in `CheckForRecursiveTypos`, this is only
+    // possible if a `TypoExpr` is created during a transformation but then
+    // fails before we can discover it.
+    auto &SemaTypoExprs = SemaRef.TypoExprs;
+    for (auto Iterator = SemaTypoExprs.begin(); Iterator != SemaTypoExprs.end();) {
+      auto TE = *Iterator;
+      auto FI = find(TypoExprs, TE);
+      if (FI != TypoExprs.end()) {
+        Iterator++;
+        continue;
+      }
+      SemaRef.clearDelayedTypo(TE);
+      Iterator = SemaTypoExprs.erase(Iterator);
+    }
+    SemaRef.TypoExprs = std::move(SavedTypoExprs);
+
+    return Res;
+  }
+
 public:
   TransformTypos(Sema &SemaRef, VarDecl *InitDecl, llvm::function_ref<ExprResult(Expr *)> Filter)
       : BaseTransform(SemaRef), InitDecl(InitDecl), ExprFilter(Filter) {}
@@ -7677,49 +7823,13 @@ public:
   ExprResult TransformBlockExpr(BlockExpr *E) { return Owned(E); }
 
   ExprResult Transform(Expr *E) {
-    ExprResult Res;
-    while (true) {
-      Res = TryTransform(E);
-
-      // Exit if either the transform was valid or if there were no TypoExprs
-      // to transform that still have any untried correction candidates..
-      if (!Res.isInvalid() ||
-          !CheckAndAdvanceTypoExprCorrectionStreams())
-        break;
-    }
-
-    // Ensure none of the TypoExprs have multiple typo correction candidates
-    // with the same edit length that pass all the checks and filters.
-    // TODO: Properly handle various permutations of possible corrections when
-    // there is more than one potentially ambiguous typo correction.
-    // Also, disable typo correction while attempting the transform when
-    // handling potentially ambiguous typo corrections as any new TypoExprs will
-    // have been introduced by the application of one of the correction
-    // candidates and add little to no value if corrected.
-    SemaRef.DisableTypoCorrection = true;
-    while (!AmbiguousTypoExprs.empty()) {
-      auto TE  = AmbiguousTypoExprs.back();
-      auto Cached = TransformCache[TE];
-      auto &State = SemaRef.getTypoExprState(TE);
-      State.Consumer->saveCurrentPosition();
-      TransformCache.erase(TE);
-      if (!TryTransform(E).isInvalid()) {
-        State.Consumer->resetCorrectionStream();
-        TransformCache.erase(TE);
-        Res = ExprError();
-        break;
-      }
-      AmbiguousTypoExprs.remove(TE);
-      State.Consumer->restoreSavedPosition();
-      TransformCache[TE] = Cached;
-    }
-    SemaRef.DisableTypoCorrection = false;
+    bool IsAmbiguous = false;
+    ExprResult Res = RecursiveTransformLoop(E, IsAmbiguous);
 
-    // Ensure that all of the TypoExprs within the current Expr have been found.
     if (!Res.isUsable())
       FindTypoExprs(TypoExprs).TraverseStmt(E);
 
-    EmitAllDiagnostics();
+    EmitAllDiagnostics(IsAmbiguous);
 
     return Res;
   }