Don't produce redundant parentheses warning for "A (::B);" and the like.

The parentheses here are not redundant as they affect the binding of the
'::' token.

llvm-svn: 321304

1 files changed, 19 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 7a50f542a39..b45d31c6b1e 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -3137,10 +3137,14 @@ static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
       (T->isRecordType() || T->isDependentType()) &&
       D.getDeclSpec().getTypeQualifiers() == 0 && D.isFirstDeclarator();
 
+  bool StartsWithDeclaratorId = true;
   for (auto &C : D.type_objects()) {
     switch (C.Kind) {
-    case DeclaratorChunk::Pointer:
     case DeclaratorChunk::Paren:
+      if (&C == &Paren)
+        continue;
+    case DeclaratorChunk::Pointer:
+      StartsWithDeclaratorId = false;
       continue;
 
     case DeclaratorChunk::Array:
@@ -3154,6 +3158,7 @@ static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
       // We assume that something like 'T (&x) = y;' is highly likely to not
       // be intended to be a temporary object.
       CouldBeTemporaryObject = false;
+      StartsWithDeclaratorId = false;
       continue;
 
     case DeclaratorChunk::Function:
@@ -3166,6 +3171,7 @@ static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
     case DeclaratorChunk::Pipe:
       // These cannot appear in expressions.
       CouldBeTemporaryObject = false;
+      StartsWithDeclaratorId = false;
       continue;
     }
   }
@@ -3186,6 +3192,18 @@ static void warnAboutRedundantParens(Sema &S, Declarator &D, QualType T) {
   SourceRange ParenRange(Paren.Loc, Paren.EndLoc);
 
   if (!CouldBeTemporaryObject) {
+    // If we have A (::B), the parentheses affect the meaning of the program.
+    // Suppress the warning in that case. Don't bother looking at the DeclSpec
+    // here: even (e.g.) "int ::x" is visually ambiguous even though it's
+    // formally unambiguous.
+    if (StartsWithDeclaratorId && D.getCXXScopeSpec().isValid()) {
+      for (NestedNameSpecifier *NNS = D.getCXXScopeSpec().getScopeRep(); NNS;
+           NNS = NNS->getPrefix()) {
+        if (NNS->getKind() == NestedNameSpecifier::Global)
+          return;
+      }
+    }
+
     S.Diag(Paren.Loc, diag::warn_redundant_parens_around_declarator)
         << ParenRange << FixItHint::CreateRemoval(Paren.Loc)
         << FixItHint::CreateRemoval(Paren.EndLoc);