DR1495: A partial specialization is ill-formed if it is not (strictly) more

specialized than the primary template. (Put another way, if we imagine there
were a partial specialization matching the primary template, we should never
select it if some other partial specialization also matches.)

llvm-svn: 290593

1 files changed, 27 insertions, 2 deletions

diff --git a/clang/test/SemaTemplate/class-template-spec.cpp b/clang/test/SemaTemplate/class-template-spec.cpp
index 86cace19dbf..cee84a750b6 100644
--- a/clang/test/SemaTemplate/class-template-spec.cpp
+++ b/clang/test/SemaTemplate/class-template-spec.cpp
@@ -167,10 +167,16 @@ namespace PR16519 {
   // expected-warning@-2 {{variadic templates are a C++11 extension}}
 #endif
 
-  template<typename T, T ...N, T ...Extra> struct __make_integer_sequence_impl<integer_sequence<T, N...>, Extra...> {
+  // Note that the following seemingly-equivalent template parameter list is
+  // not OK; it would result in a partial specialization that is not more
+  // specialized than the primary template. (See NTTPTypeVsPartialOrder below.)
+  //
+  //    template<typename T, T ...N, T ...Extra>
+  template<typename T, T ...N, typename integer_sequence<T, N...>::value_type ...Extra>
 #if __cplusplus <= 199711L
-  // expected-warning@-2 2 {{variadic templates are a C++11 extension}}
+  // expected-warning@-2 2{{variadic templates are a C++11 extension}}
 #endif
+  struct __make_integer_sequence_impl<integer_sequence<T, N...>, Extra...> {
     typedef integer_sequence<T, N..., sizeof...(N) + N..., Extra...> type;
   };
 
@@ -193,6 +199,25 @@ namespace PR16519 {
 #endif
 }
 
+namespace NTTPTypeVsPartialOrder {
+  struct X { typedef int value_type; };
+  template<typename T> struct Y { typedef T value_type; };
+
+  template<typename T, typename T::value_type N> struct A; // expected-note {{template}}
+  template<int N> struct A<X, N> {};
+  template<typename T, T N> struct A<Y<T>, N> {}; // expected-error {{not more specialized}} expected-note {{'T' vs 'typename Y<type-parameter-0-0>::value_type'}}
+  A<X, 0> ax;
+  A<Y<int>, 0> ay;
+
+
+  template<int, typename T, typename T::value_type> struct B; // expected-note {{template}}
+  template<typename T, typename T::value_type N> struct B<0, T, N>; // expected-note {{matches}}
+  template<int N> struct B<0, X, N> {};
+  template<typename T, T N> struct B<0, Y<T>, N> {}; // expected-error {{not more specialized}} expected-note {{'T' vs 'typename Y<type-parameter-0-0>::value_type'}} expected-note {{matches}}
+  B<0, X, 0> bx;
+  B<0, Y<int>, 0> by; // expected-error {{ambiguous}}
+}
+
 namespace DefaultArgVsPartialSpec {
   // Check that the diagnostic points at the partial specialization, not just at
   // the default argument.