PR c++/81102 - Wrong error with partial specialization.

	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Strip reference when comparing
	types.  Do type deduction later.

From-SVN: r249320

gcc/cp/ChangeLog

 2017-06-16  Jason Merrill  <jason@redhat.com>
 
+	PR c++/81102 - Wrong error with partial specialization.
+	* pt.c (unify) [TEMPLATE_PARM_INDEX]: Strip reference when comparing
+	types.  Do type deduction later.
+
 	PR c++/80174 - ICE with partial specialization of member template.
 	PR c++/71747
 	* pt.c (get_partial_spec_bindings): Only coerce innermost args.

gcc/cp/pt.c

@@ -20628,18 +20628,6 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	  return x;
 	}
 
-      if (cxx_dialect >= cxx1z
-	  /* We deduce from array bounds in try_array_deduction.  */
-	  && !(strict & UNIFY_ALLOW_INTEGER)
-	  && uses_template_parms (TREE_TYPE (parm))
-	  && !type_uses_auto (TREE_TYPE (parm)))
-	{
-	  tree atype = TREE_TYPE (arg);
-	  RECUR_AND_CHECK_FAILURE (tparms, targs,
-				   TREE_TYPE (parm), atype,
-				   UNIFY_ALLOW_NONE, explain_p);
-	}
-
       /* [temp.deduct.type] If, in the declaration of a function template
 	 with a non-type template-parameter, the non-type
 	 template-parameter is used in an expression in the function
@@ -20660,7 +20648,8 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	/* Template-parameter dependent expression.  Just accept it for now.
 	   It will later be processed in convert_template_argument.  */
 	;
-      else if (same_type_p (TREE_TYPE (arg), tparm))
+      else if (same_type_p (non_reference (TREE_TYPE (arg)),
+			    non_reference (tparm)))
 	/* OK */;
       else if ((strict & UNIFY_ALLOW_INTEGER)
 	       && CP_INTEGRAL_TYPE_P (tparm))
@@ -20669,9 +20658,22 @@ unify (tree tparms, tree targs, tree parm, tree arg, int strict,
 	   corresponding parameter.  */
 	arg = fold (build_nop (tparm, arg));
       else if (uses_template_parms (tparm))
-	/* We haven't deduced the type of this parameter yet.  Try again
-	   later.  */
+	{
+	  /* We haven't deduced the type of this parameter yet.  */
+	  if (cxx_dialect >= cxx1z
+	      /* We deduce from array bounds in try_array_deduction.  */
+	      && !(strict & UNIFY_ALLOW_INTEGER))
+	    {
+	      /* Deduce it from the non-type argument.  */
+	      tree atype = TREE_TYPE (arg);
+	      RECUR_AND_CHECK_FAILURE (tparms, targs,
+				       tparm, atype,
+				       UNIFY_ALLOW_NONE, explain_p);
+	    }
+	  else
+	    /* Try again later.  */
 	    return unify_success (explain_p);
+	}
       else
 	return unify_type_mismatch (explain_p, tparm, TREE_TYPE (arg));
 

gcc/testsuite/g++.dg/template/partial-specialization7.C

+// PR c++/81102
+
+template <typename FuncSig, FuncSig f>
+struct HelperWrapper;
+
+// [...]
+
+template <typename Ret, Ret (&Func)()>
+struct HelperWrapper<Ret (&)(), Func>
+{
+    static inline int WrapFuncT(const int)
+    {
+        return 0; // Changed
+    }
+};
+
+// Unary
+template <typename Ret, typename Arg1, Ret (&Func)(Arg1)>
+struct HelperWrapper<Ret (&)(Arg1), Func>
+{
+    static inline int WrapFuncT(const int)
+    {
+        return 1; // Changed
+    }
+};
+
+// Binary
+template <typename Ret, typename Arg1, typename Arg2, Ret (&Func)(Arg1, Arg2)>
+struct HelperWrapper<Ret (&)(Arg1, Arg2), Func>
+{
+    static inline int WrapFuncT(const int)
+    {
+        return 2; // Changed
+    }
+};
+
+int main()
+{
+  return 0;
+}

gcc/testsuite/g++.dg/template/partial5.C

@@ -14,7 +14,7 @@ template<typename T, typename T::foo V>
 struct Y { };
 
 template<typename T, typename U, U v>
-struct Y<T, v> { }; // { dg-error "" }
+struct Y<T, v> { }; // { dg-error "" "" { target { ! c++1z } } }
 
 
 template<typename T, T V>