Add return type checking for overriding virtual functions. We currently don't check covariance but that's next.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@71759 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Sema/Sema.h b/lib/Sema/Sema.h
index bd01ec9..5b263b7 100644
--- a/lib/Sema/Sema.h
+++ b/lib/Sema/Sema.h
@@ -1780,6 +1780,12 @@
                                     DeclarationName Name);
   
   std::string getAmbiguousPathsDisplayString(BasePaths &Paths);
+  
+  /// CheckReturnTypeCovariance - Checks whether two types are covariant, 
+  /// according to C++ [class.virtual]p5.
+  bool CheckOverridingFunctionReturnType(const CXXMethodDecl *New, 
+                                         const CXXMethodDecl *Old);
+  
 
   //===--------------------------------------------------------------------===//
   // C++ Access Control