Improve 0-argument -Wvexing-parse diagnostic by adding notes with fix-its:

 - If the declarator is at the start of a line, and the previous line contained
   another declarator and ended with a comma, then that comma was probably a
   typo for a semicolon:

   int n = 0, m = 1, l = 2, // k = 5;
   myImportantFunctionCall(); // oops!

 - If removing the parentheses would correctly initialize the object, then
   produce a note suggesting that fix.

 - Otherwise, if there is a simple initializer we can suggest which performs
   value-initialization, then provide a note suggesting a correction to that
   initializer.

Sema::Declarator now tracks the location of the comma prior to the declarator in
the declaration, if there is one, to facilitate providing the note. The code to
determine an appropriate initializer from the -Wuninitialized warning has been
factored out to allow use in both that and -Wvexing-parse.

llvm-svn: 148072

3 files changed, 8 insertions, 3 deletions

diff --git a/clang/lib/Parse/ParseDecl.cpp b/clang/lib/Parse/ParseDecl.cpp
index be5d5ae54cd..032326cea71 100644
--- a/clang/lib/Parse/ParseDecl.cpp
+++ b/clang/lib/Parse/ParseDecl.cpp
@@ -1138,6 +1138,7 @@ Parser::DeclGroupPtrTy Parser::ParseDeclGroup(ParsingDeclSpec &DS,
 
     // Parse the next declarator.
     D.clear();
+    D.setCommaLoc(CommaLoc);
 
     // Accept attributes in an init-declarator.  In the first declarator in a
     // declaration, these would be part of the declspec.  In subsequent
@@ -2665,9 +2666,11 @@ ParseStructDeclaration(DeclSpec &DS, FieldCallback &Fields) {
 
   // Read struct-declarators until we find the semicolon.
   bool FirstDeclarator = true;
+  SourceLocation CommaLoc;
   while (1) {
     ParsingDeclRAIIObject PD(*this);
     FieldDeclarator DeclaratorInfo(DS);
+    DeclaratorInfo.D.setCommaLoc(CommaLoc);
 
     // Attributes are only allowed here on successive declarators.
     if (!FirstDeclarator)
@@ -2703,7 +2706,7 @@ ParseStructDeclaration(DeclSpec &DS, FieldCallback &Fields) {
       return;
 
     // Consume the comma.
-    ConsumeToken();
+    CommaLoc = ConsumeToken();
 
     FirstDeclarator = false;
   }
diff --git a/clang/lib/Parse/ParseDeclCXX.cpp b/clang/lib/Parse/ParseDeclCXX.cpp
index 285dbbbe079..c31c55ba5b9 100644
--- a/clang/lib/Parse/ParseDeclCXX.cpp
+++ b/clang/lib/Parse/ParseDeclCXX.cpp
@@ -2044,6 +2044,7 @@ void Parser::ParseCXXClassMemberDeclaration(AccessSpecifier AS,
     BitfieldSize = true;
     Init = true;
     HasInitializer = false;
+    DeclaratorInfo.setCommaLoc(CommaLoc);
 
     // Attributes are only allowed on the second declarator.
     MaybeParseGNUAttributes(DeclaratorInfo);
diff --git a/clang/lib/Parse/Parser.cpp b/clang/lib/Parse/Parser.cpp
index d14b9adce2c..e09ee79c8cb 100644
--- a/clang/lib/Parse/Parser.cpp
+++ b/clang/lib/Parse/Parser.cpp
@@ -1067,11 +1067,12 @@ void Parser::ParseKNRParamDeclarations(Declarator &D) {
       if (Tok.isNot(tok::comma))
         break;
 
+      ParmDeclarator.clear();
+
       // Consume the comma.
-      ConsumeToken();
+      ParmDeclarator.setCommaLoc(ConsumeToken());
 
       // Parse the next declarator.
-      ParmDeclarator.clear();
       ParseDeclarator(ParmDeclarator);
     }