[Sema] Do not match function type with const T in template argument deduction

[lliu0]

Summary

From http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584, function type should not match cv-qualified type in template argument deduction. This also matches what GCC and EDG do in template argument deduction.

[rjmccall]

Fix seems right.

cfe/trunk/lib/Sema/SemaTemplateDeduction.cpp

if (const TemplateTypeParmType *TemplateTypeParm
     if (!(TDF & TDF_IgnoreQualifiers) &&
         hasInconsistentOrSupersetQualifiersOf(Param, Arg)) {
       Info.Param = cast<TemplateTypeParmDecl>(TemplateParams->getParam(Index));
       Info.FirstArg = TemplateArgument(Param);
       Info.SecondArg = TemplateArgument(Arg);
       return Sema::TDK_Underqualified;
     }
 
+    // Do not match a function type with a cv-qualified type.
+    // http://www.open-std.org/jtc1/sc22/wg21/docs/cwg_active.html#1584
+    if (Arg->isFunctionType() && Param.hasQualifiers()) {
+      return Sema::TDK_NonDeducedMismatch;
+    }
+
     assert(TemplateTypeParm->getDepth() == Info.getDeducedDepth() &&
            "saw template type parameter with wrong depth");
     assert(Arg != S.Context.OverloadTy && "Unresolved overloaded function");
     QualType DeducedType = Arg;
 
     // Remove any qualifiers on the parameter from the deduced type.
     // We checked the qualifiers for consistency above.
     Qualifiers DeducedQs = DeducedType.getQualifiers();

cfe/trunk/test/CXX/drs/dr15xx.cpp

 };
 
 auto DR1579_lambda_invalid = []() -> GenericMoveOnly<char> {
   static GenericMoveOnly<float> mo;
   return mo; // expected-error{{invokes a deleted function}}
 };
 } // end namespace dr1579
 
+namespace dr1584 {
+  // Deducing function types from cv-qualified types
+  template<typename T> void f(const T *); // expected-note {{candidate template ignored}}
+  template<typename T> void g(T *, const T * = 0);
+  template<typename T> void h(T *) { T::error; } // expected-error {{no members}}
+  template<typename T> void h(const T *);
+  void i() {
+    f(&i); // expected-error {{no matching function}}
+    g(&i);
+    h(&i); // expected-note {{here}}
+  }
+}
+
 namespace dr1589 {   // dr1589: 3.7 c++11
   // Ambiguous ranking of list-initialization sequences
 
   void f0(long, int=0);                 // Would makes selection of #0 ambiguous
   void f0(long);                        // #0
   void f0(std::initializer_list<int>);  // #00
   void g0() { f0({1L}); }               // chooses #00
 

cfe/trunk/test/CXX/drs/dr4xx.cpp

namespace dr468 { // dr468: yes c++11
   };
   int k = dr468::template A<int>::template B<char>::C;
 #if __cplusplus < 201103L
   // expected-error@-2 2{{'template' keyword outside of a template}}
 #endif
 }
 
 namespace dr469 { // dr469: no
-  // FIXME: The core issue here didn't really answer the question. We don't
-  // deduce 'const T' from a function or reference type in a class template...
-  template<typename T> struct X; // expected-note 2{{here}}
+  template<typename T> struct X; // expected-note {{here}}
   template<typename T> struct X<const T> {};
   X<int&> x; // expected-error {{undefined}}
-  X<int()> y; // expected-error {{undefined}}
-
-  // ... but we do in a function template. GCC and EDG fail deduction of 'f'
-  // and the second 'h'.
-  template<typename T> void f(const T *);
-  template<typename T> void g(T *, const T * = 0);
-  template<typename T> void h(T *) { T::error; }
-  template<typename T> void h(const T *);
-  void i() {
-    f(&i);
-    g(&i);
-    h(&i);
-  }
 }
 
 namespace dr470 { // dr470: yes
   template<typename T> struct A {
     struct B {};
   };
   template<typename T> struct C {
   };

cfe/trunk/test/SemaTemplate/function-pointer-qualifier.cpp

+// RUN: %clang_cc1 -fsyntax-only -verify %s
+// expected-no-diagnostics
+
+template<class _Ty> inline
+  void testparam(_Ty **, _Ty **)
+  {
+  }
+
+template<class _Ty> inline
+  void testparam(_Ty *const *, _Ty **)
+  {
+  }
+
+template<class _Ty> inline
+  void testparam(_Ty **, const _Ty **)
+  {
+  }
+
+template<class _Ty> inline
+  void testparam(_Ty *const *, const _Ty **)
+  {
+  }
+
+void case0()
+{
+    void (**p1)();
+    void (**p2)();
+    testparam(p1, p2);
+}