Improvements to vexing-parse warnings. Make the no-parameters case more

accurate by asking the parser whether there was an ambiguity rather than trying
to reverse-engineer it from the DeclSpec. Make the with-parameters case have
better diagnostics by using semantic information to drive the warning,
improving the diagnostics and adding a fixit.

Patch by Nikola Smiljanic. Some minor changes by me to suppress diagnostics for
declarations of the form 'T (*x)(...)', which seem to have a very high false
positive rate, and to reduce indentation in 'warnAboutAmbiguousFunction'.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@160998 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 8 insertions, 10 deletions

diff --git a/lib/Parse/ParseDecl.cpp b/lib/Parse/ParseDecl.cpp
index ea514d3826..328345413f 100644
--- a/lib/Parse/ParseDecl.cpp
+++ b/lib/Parse/ParseDecl.cpp
@@ -4318,17 +4318,14 @@ void Parser::ParseDirectDeclarator(Declarator &D) {
       // The paren may be part of a C++ direct initializer, eg. "int x(1);".
       // In such a case, check if we actually have a function declarator; if it
       // is not, the declarator has been fully parsed.
-      if (getLangOpts().CPlusPlus && D.mayBeFollowedByCXXDirectInit()) {
-        // When not in file scope, warn for ambiguous function declarators, just
-        // in case the author intended it as a variable definition.
-        bool warnIfAmbiguous = D.getContext() != Declarator::FileContext;
-        if (!isCXXFunctionDeclarator(warnIfAmbiguous))
-          break;
-      }
+      bool IsAmbiguous = false;
+      if (getLangOpts().CPlusPlus && D.mayBeFollowedByCXXDirectInit() &&
+          !isCXXFunctionDeclarator(&IsAmbiguous))
+        break;
       ParsedAttributes attrs(AttrFactory);
       BalancedDelimiterTracker T(*this, tok::l_paren);
       T.consumeOpen();
-      ParseFunctionDeclarator(D, attrs, T);
+      ParseFunctionDeclarator(D, attrs, T, IsAmbiguous);
       PrototypeScope.Exit();
     } else if (Tok.is(tok::l_square)) {
       ParseBracketDeclarator(D);
@@ -4445,7 +4442,7 @@ void Parser::ParseParenDeclarator(Declarator &D) {
   // function prototype scope, including parameter declarators.
   ParseScope PrototypeScope(this,
                             Scope::FunctionPrototypeScope|Scope::DeclScope);
-  ParseFunctionDeclarator(D, attrs, T, RequiresArg);
+  ParseFunctionDeclarator(D, attrs, T, false, RequiresArg);
   PrototypeScope.Exit();
 }
 
@@ -4471,6 +4468,7 @@ void Parser::ParseParenDeclarator(Declarator &D) {
 void Parser::ParseFunctionDeclarator(Declarator &D,
                                      ParsedAttributes &FirstArgAttrs,
                                      BalancedDelimiterTracker &Tracker,
+                                     bool IsAmbiguous,
                                      bool RequiresArg) {
   assert(getCurScope()->isFunctionPrototypeScope() &&
          "Should call from a Function scope");
@@ -4588,7 +4586,7 @@ void Parser::ParseFunctionDeclarator(Declarator &D,
   // Remember that we parsed a function type, and remember the attributes.
   D.AddTypeInfo(DeclaratorChunk::getFunction(HasProto,
                                              /*isVariadic=*/EllipsisLoc.isValid(),
-                                             EllipsisLoc,
+                                             IsAmbiguous, EllipsisLoc,
                                              ParamInfo.data(), ParamInfo.size(),
                                              DS.getTypeQualifiers(),
                                              RefQualifierIsLValueRef,