implement PR4451, improving error recovery for a mistaken : where a :: was

intended.  On the first testcase in the bug, we now produce:

cxx-decl.cpp:12:2: error: unexpected ':' in nested name specifier
y:a a2;
 ^
 ::

instead of:

t.cc:8:1: error: C++ requires a type specifier for all declarations
x:a a2;
^
t.cc:8:2: error: invalid token after top level declarator
x:a a2;
 ^
 ;
t.cc:9:11: error: use of undeclared identifier 'a2'
x::a a3 = a2;
          ^



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@90713 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 14 insertions, 0 deletions

diff --git a/include/clang/Parse/Action.h b/include/clang/Parse/Action.h
index fc56cc6847..200bd8a6b2 100644
--- a/include/clang/Parse/Action.h
+++ b/include/clang/Parse/Action.h
@@ -334,6 +334,20 @@ public:
                                                   bool EnteringContext) {
     return 0;
   }
+  
+  /// IsInvalidUnlessNestedName - This method is used for error recovery
+  /// purposes to determine whether the specified identifier is only valid as
+  /// a nested name specifier, for example a namespace name.  It is
+  /// conservatively correct to always return false from this method.
+  ///
+  /// The arguments are the same as those passed to ActOnCXXNestedNameSpecifier.
+  virtual bool IsInvalidUnlessNestedName(Scope *S,
+                                         const CXXScopeSpec &SS,
+                                         IdentifierInfo &II,
+                                         TypeTy *ObjectType,
+                                         bool EnteringContext) {
+    return false;
+  }
 
   /// ActOnCXXNestedNameSpecifier - Called during parsing of a
   /// nested-name-specifier that involves a template-id, e.g.,