From 67daacbdc26c0fd73881b2327ce65e0d84ae5499 Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Fri, 30 Mar 2012 16:20:47 +0000
Subject: [PATCH] If we encounter a friend class template for which we cannot
 resolve the nested-name-specifier (e.g., because it is dependent), do not
 error even though we can't represent it in the AST at this point.

This is a horrible, horrible hack. The actual feature we still need to
implement (for C++98!) is covered by PR12292. However, we used to
silently accept this code, so when we recently started rejecting it we
caused some regressions (e.g., <rdar://problem/11147355>). This hack
brings us back to the passable-but-not-good state we had previously.

llvm-svn: 153752
---
 clang/lib/Sema/SemaTemplate.cpp             |  8 ++++++--
 clang/test/SemaTemplate/friend-template.cpp | 13 +++++++++++++
 2 files changed, 19 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 34e5d722ca8f..ec11f8d22429 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -872,8 +872,12 @@ Sema::CheckClassTemplate(Scope *S, unsigned TagSpec, TagUseKind TUK,
   if (SS.isNotEmpty() && !SS.isInvalid()) {
     SemanticContext = computeDeclContext(SS, true);
     if (!SemanticContext) {
-      Diag(NameLoc, diag::err_template_qualified_declarator_no_match)
-        << SS.getScopeRep() << SS.getRange();
+      // FIXME: Horrible, horrible hack! We can't currently represent this
+      // in the AST, and historically we have just ignored such friend
+      // class templates, so don't complain here.
+      if (TUK != TUK_Friend)
+        Diag(NameLoc, diag::err_template_qualified_declarator_no_match)
+          << SS.getScopeRep() << SS.getRange();
       return true;
     }
 
diff --git a/clang/test/SemaTemplate/friend-template.cpp b/clang/test/SemaTemplate/friend-template.cpp
index 152df37d3db3..9c95fa0151c1 100644
--- a/clang/test/SemaTemplate/friend-template.cpp
+++ b/clang/test/SemaTemplate/friend-template.cpp
@@ -230,3 +230,16 @@ namespace PR10660 {
     template <> friend class B; // expected-error{{extraneous 'template<>' in declaration of class 'B'}}
   };
 }
+
+namespace rdar11147355 {
+  template <class T> 
+  struct A {
+    template <class U> class B;
+    template <class S> template <class U> friend class A<S>::B; 
+  };
+  
+  template <class S> template <class U> class A<S>::B {
+  }; 
+  
+  A<double>::B<double>  ab;
+}