Diagnose invalid uses of tagged types with a missing tag. For example, in:

struct xyz { int y; };
enum abc { ZZZ };

static xyz b;
abc c;

we used to produce:

t2.c:4:8: error: unknown type name 'xyz'
static xyz b;
       ^
t2.c:5:1: error: unknown type name 'abc'
abc c;
^

we now produce:

t2.c:4:8: error: use of tagged type 'xyz' without 'struct' tag
static xyz b;
       ^
       struct
t2.c:5:1: error: use of tagged type 'abc' without 'enum' tag
abc c;
^
enum

GCC produces the normal:
t2.c:4: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘b’
t2.c:5: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or ‘__attribute__’ before ‘c’

rdar://6783347

llvm-svn: 68914

3 files changed, 15 insertions, 2 deletions

diff --git a/clang/include/clang/Basic/DiagnosticParseKinds.td b/clang/include/clang/Basic/DiagnosticParseKinds.td
index 66a48cffb02..5e97faa96da 100644
--- a/clang/include/clang/Basic/DiagnosticParseKinds.td
+++ b/clang/include/clang/Basic/DiagnosticParseKinds.td
@@ -145,6 +145,8 @@ def err_invalid_decl_spec_combination : Error<
   "cannot combine with previous '%0' declaration specifier">;
 def err_unknown_typename : Error<
   "unknown type name %0">;
+def err_use_of_tag_name_without_tag : Error<
+  "use of tagged type %0 without '%1' tag">;
 
 
 /// Objective-C parser diagnostics
diff --git a/clang/include/clang/Parse/Action.h b/clang/include/clang/Parse/Action.h
index 699d5711466..df54da46f6c 100644
--- a/clang/include/clang/Parse/Action.h
+++ b/clang/include/clang/Parse/Action.h
@@ -139,6 +139,15 @@ public:
   virtual TypeTy *getTypeName(IdentifierInfo &II, SourceLocation NameLoc,
                               Scope *S, const CXXScopeSpec *SS = 0) = 0;
 
+  /// isTagName() - This method is called *for error recovery purposes only*
+  /// to determine if the specified name is a valid tag name ("struct foo").  If
+  /// so, this returns the TST for the tag corresponding to it (TST_enum,
+  /// TST_union, TST_struct, TST_class).  This is used to diagnose cases in C
+  /// where the user forgot to specify the tag.
+  virtual DeclSpec::TST isTagName(IdentifierInfo &II, Scope *S) {
+    return DeclSpec::TST_unspecified;
+  }
+  
   /// isCurrentClassName - Return true if the specified name is the
   /// name of the innermost C++ class type currently being defined.
   virtual bool isCurrentClassName(const IdentifierInfo &II, Scope *S,
diff --git a/clang/include/clang/Parse/Parser.h b/clang/include/clang/Parse/Parser.h
index 3e09a2cc535..f5a00065df1 100644
--- a/clang/include/clang/Parse/Parser.h
+++ b/clang/include/clang/Parse/Parser.h
@@ -825,7 +825,8 @@ private:
   
   void ParseObjCTypeQualifierList(ObjCDeclSpec &DS);
 
-  void ParseEnumSpecifier(DeclSpec &DS, AccessSpecifier AS = AS_none);
+  void ParseEnumSpecifier(SourceLocation TagLoc, DeclSpec &DS,
+                          AccessSpecifier AS = AS_none);
   void ParseEnumBody(SourceLocation StartLoc, DeclPtrTy TagDecl);
   void ParseStructUnionBody(SourceLocation StartLoc, unsigned TagType,
                             DeclPtrTy TagDecl);
@@ -1012,7 +1013,8 @@ private:
   // C++ 9: classes [class] and C structs/unions.
   TypeResult ParseClassName(SourceLocation &EndLocation, 
                             const CXXScopeSpec *SS = 0);
-  void ParseClassSpecifier(DeclSpec &DS, 
+  void ParseClassSpecifier(tok::TokenKind TagTokKind, SourceLocation TagLoc,
+                           DeclSpec &DS, 
                            TemplateParameterLists *TemplateParams = 0,
                            AccessSpecifier AS = AS_none);
   void ParseCXXMemberSpecification(SourceLocation StartLoc, unsigned TagType,