[MSVC] Explicit specializations can be declared in any namespace (fix for http://llvm.org/PR13738)

MS compiler emits no errors in case of explicit specializations outside declaration enclosing namespaces, even when language extensions are disabled.
The patch is to suppress errors and emit extension warnings if explicit specializations are not declared in the corresponding namespaces.
This fixes PR13738.

Patch by Alexey Frolov.

Differential Revision: http://reviews.llvm.org/D8283

llvm-svn: 232800

3 files changed, 46 insertions, 5 deletions

diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a3ab5dff8c8..b9737f23c00 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3443,6 +3443,12 @@ def err_template_spec_redecl_out_of_scope : Error<
   "variable template partial|function template|member "
   "function|static data member|member class|member enumeration}0 "
   "specialization of %1 not in a namespace enclosing %2">;
+def ext_ms_template_spec_redecl_out_of_scope: ExtWarn<
+  "%select{class template|class template partial|variable template|"
+  "variable template partial|function template|member "
+  "function|static data member|member class|member enumeration}0 "
+  "specialization of %1 outside namespace enclosing %2 "
+  "is a Microsoft extension">, InGroup<Microsoft>;
 def err_template_spec_redecl_global_scope : Error<
   "%select{class template|class template partial|variable template|"
   "variable template partial|function template|member "
diff --git a/clang/lib/Sema/SemaTemplate.cpp b/clang/lib/Sema/SemaTemplate.cpp
index 6cba79a5fbb..fad15bbc4f6 100644
--- a/clang/lib/Sema/SemaTemplate.cpp
+++ b/clang/lib/Sema/SemaTemplate.cpp
@@ -5835,11 +5835,13 @@ static bool CheckTemplateSpecializationScope(Sema &S,
     if (isa<TranslationUnitDecl>(SpecializedContext))
       S.Diag(Loc, diag::err_template_spec_redecl_global_scope)
         << EntityKind << Specialized;
-    else if (isa<NamespaceDecl>(SpecializedContext))
-      S.Diag(Loc, diag::err_template_spec_redecl_out_of_scope)
-        << EntityKind << Specialized
-        << cast<NamedDecl>(SpecializedContext);
-    else
+    else if (isa<NamespaceDecl>(SpecializedContext)) {
+      int Diag = diag::err_template_spec_redecl_out_of_scope;
+      if (S.getLangOpts().MicrosoftExt)
+        Diag = diag::ext_ms_template_spec_redecl_out_of_scope;
+      S.Diag(Loc, Diag) << EntityKind << Specialized
+                        << cast<NamedDecl>(SpecializedContext);
+    } else
       llvm_unreachable("unexpected namespace context for specialization");
 
     S.Diag(Specialized->getLocation(), diag::note_specialized_entity);
diff --git a/clang/test/SemaTemplate/ext_ms_template_spec.cpp b/clang/test/SemaTemplate/ext_ms_template_spec.cpp
new file mode 100644
index 00000000000..fc2ed16f9f8
--- /dev/null
+++ b/clang/test/SemaTemplate/ext_ms_template_spec.cpp
@@ -0,0 +1,33 @@
+// RUN: %clang_cc1 -fsyntax-only -fms-extensions -std=c++11 -verify %s
+
+namespace A {
+
+template <class T>
+class ClassTemplate; // expected-note {{explicitly specialized declaration is here}}
+
+template <class T1, class T2>
+class ClassTemplatePartial; // expected-note {{explicitly specialized declaration is here}}
+
+template <typename T> struct X {
+  struct MemberClass; // expected-note {{explicitly specialized declaration is here}}
+  enum MemberEnumeration; // expected-note {{explicitly specialized declaration is here}} // expected-error {{ISO C++ forbids forward references to 'enum' types}}
+};
+
+}
+
+namespace B {
+
+template <>
+class A::ClassTemplate<int>; // expected-warning {{class template specialization of 'ClassTemplate' outside namespace enclosing 'A' is a Microsoft extension}}
+
+template <class T1>
+class A::ClassTemplatePartial<T1, T1 *> {}; // expected-warning {{class template partial specialization of 'ClassTemplatePartial' outside namespace enclosing 'A' is a Microsoft extension}}
+
+template <>
+struct A::X<int>::MemberClass; // expected-warning {{member class specialization of 'MemberClass' outside namespace enclosing 'A' is a Microsoft extension}}
+
+template <>
+enum A::X<int>::MemberEnumeration; // expected-warning {{member enumeration specialization of 'MemberEnumeration' outside namespace enclosing 'A' is a Microsoft extension}} // expected-error {{ISO C++ forbids forward references to 'enum' types}}
+
+}
+