Diagnose friend function template redefinitions.

Friend function template defined in a class template becomes available if
the enclosing class template is instantiated. Until the function template
is used, it does not have a body, but still is considered a definition for
the purpose of redeclaration checks.

This change modifies redefinition check so that it can find the friend
function template definitions in instantiated classes.

Differential Revision: http://reviews.llvm.org/D21508

llvm-svn: 348473
diff --git a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
index f880d46..8f9af03 100644
--- a/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ b/clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -1817,7 +1817,9 @@
   // If the original function was part of a friend declaration,
   // inherit its namespace state and add it to the owner.
   if (isFriend) {
-    PrincipalDecl->setObjectOfFriendDecl();
+    Function->setObjectOfFriendDecl();
+    if (FunctionTemplateDecl *FT = Function->getDescribedFunctionTemplate())
+      FT->setObjectOfFriendDecl();
     DC->makeDeclVisibleInContext(PrincipalDecl);
 
     bool QueuedInstantiation = false;