From fe3310697028d8d3d35a11b0877bb2bc47e55b8d Mon Sep 17 00:00:00 2001
From: Douglas Gregor <dgregor@apple.com>
Date: Sat, 13 Feb 2010 05:23:25 +0000
Subject: [PATCH] Permit the use of typedefs of class template specializations
 in qualified declarator-ids. This patch is actually due to Cornelius; fixes
 PR6179.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@96082 91177308-0d34-0410-b5e6-96231b3b80d8
---
 include/clang/Basic/DiagnosticSemaKinds.td     |  3 ---
 lib/Sema/SemaTemplate.cpp                      | 16 ++++++----------
 test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp | 15 +++++++++++++--
 3 files changed, 19 insertions(+), 15 deletions(-)

diff --git a/include/clang/Basic/DiagnosticSemaKinds.td b/include/clang/Basic/DiagnosticSemaKinds.td
index 0eb694cb91..19b242e86b 100644
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@@ -1108,9 +1108,6 @@ def err_template_tag_noparams : Error<
 def err_template_decl_ref : Error<
   "cannot refer to class template %0 without a template argument list">;
 
-def err_typedef_in_def_scope : Error<
-  "cannot use typedef %0 in scope specifier for out-of-line declaration">;
-
 // C++ Template Argument Lists
 def err_template_arg_list_different_arity : Error<
   "%select{too few|too many}0 template arguments for "
diff --git a/lib/Sema/SemaTemplate.cpp b/lib/Sema/SemaTemplate.cpp
index c2f0fbc641..10e411f582 100644
--- a/lib/Sema/SemaTemplate.cpp
+++ b/lib/Sema/SemaTemplate.cpp
@@ -1235,18 +1235,14 @@ Sema::MatchTemplateParametersToScopeSpecifier(SourceLocation DeclStartLoc,
     //   such a member, the member declaration shall be preceded by a
     //   template<> for each enclosing class template that is
     //   explicitly specialized.
-    // We interpret this as forbidding typedefs of template
-    // specializations in the scope specifiers of out-of-line decls.
-    if (const TypedefType *TT = dyn_cast<TypedefType>(T)) {
-      const Type *UnderlyingT = TT->LookThroughTypedefs().getTypePtr();
-      if (isa<TemplateSpecializationType>(UnderlyingT))
-        // FIXME: better source location information.
-        Diag(DeclStartLoc, diag::err_typedef_in_def_scope) << QualType(T,0);
-      T = UnderlyingT;
-    }
+    //
+    // Following the existing practice of GNU and EDG, we allow a typedef of a
+    // template specialization type.
+    if (const TypedefType *TT = dyn_cast<TypedefType>(T))
+      T = TT->LookThroughTypedefs().getTypePtr();
 
     if (const TemplateSpecializationType *SpecType
-          = dyn_cast<TemplateSpecializationType>(T)) {
+                                  = dyn_cast<TemplateSpecializationType>(T)) {
       TemplateDecl *Template = SpecType->getTemplateName().getAsTemplateDecl();
       if (!Template)
         continue; // FIXME: should this be an error? probably...
diff --git a/test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp b/test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp
index 3b5b5afa8e..88cfc5d7c3 100644
--- a/test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp
+++ b/test/CXX/temp/temp.spec/temp.expl.spec/p17.cpp
@@ -18,7 +18,18 @@ namespace test1 {
   };
   typedef A<int> AA;
   
-  template <> int AA::foo = 0; // expected-error {{cannot use typedef}}
-  int AA::bar = 1; // expected-error {{cannot use typedef}} expected-error {{template specialization requires 'template<>'}}
+  template <> int AA::foo = 0; 
+  int AA::bar = 1; // expected-error {{template specialization requires 'template<>'}}
   int A<float>::bar = 2; // expected-error {{template specialization requires 'template<>'}}
+
+  template <> class A<double> { 
+  public:
+    static int foo; // expected-note{{attempt to specialize}}
+    static int bar;    
+  };
+
+  typedef A<double> AB;
+  template <> int AB::foo = 0; // expected-error{{extraneous 'template<>'}} \
+                               // expected-error{{does not specialize}}
+  int AB::bar = 1;
 }
-- 
2.40.0