re PR c++/48500 (Regression: Failing to convert template argument to concrete type, in C++0x mode.)

PR c++/48500
	* semantics.c (potential_constant_expression_1) [CALL_EXPR]: Check
	arguments even if we don't know the function.

From-SVN: r172165

gcc/cp/ChangeLog

@@ -1,5 +1,9 @@
 2011-04-07  Jason Merrill  <jason@redhat.com>
 
+	PR c++/48500
+	* semantics.c (potential_constant_expression_1) [CALL_EXPR]: Check
+	arguments even if we don't know the function.
+
 	PR c++/48481
 	* tree.c (build_overload): Allow an unwrapped FUNCTION_DECL
 	at the end of the chain.

gcc/cp/semantics.c

@@ -7358,6 +7358,8 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
             class member access expression, including the result of the
             implicit transformation in the body of the non-static
             member function (9.3.1);  */
+      /* FIXME this restriction seems pointless since the standard dropped
+	 "potential constant expression".  */
       if (is_this_parameter (t))
         {
           if (flags & tf_error)
@@ -7373,21 +7375,12 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
       {
         tree fun = get_function_named_in_call (t);
         const int nargs = call_expr_nargs (t);
-        if (TREE_CODE (fun) != FUNCTION_DECL)
-          {
-	    if (potential_constant_expression_1 (fun, rval, flags))
-	      /* Might end up being a constant function pointer.  */
-	      return true;
-            if (flags & tf_error)
-              error ("%qE is not a function name", fun);
-            return false;
-          }
-	/* Skip initial arguments to base constructors.  */
-	if (DECL_BASE_CONSTRUCTOR_P (fun))
-	  i = num_artificial_parms_for (fun);
-	else
 	i = 0;
-	fun = DECL_ORIGIN (fun);
+
+	if (is_overloaded_fn (fun))
+	  {
+	    if (TREE_CODE (fun) == FUNCTION_DECL)
+	      {
 		if (builtin_valid_in_constant_expr_p (fun))
 		  return true;
 		if (!DECL_DECLARED_CONSTEXPR_P (fun)
@@ -7397,27 +7390,48 @@ potential_constant_expression_1 (tree t, bool want_rval, tsubst_flags_t flags)
 		      error ("%qD is not %<constexpr%>", fun);
 		    return false;
 		  }
-        for (; i < nargs; ++i)
+		/* A call to a non-static member function takes the address
-          {
+		   of the object as the first argument.  But in a constant
-            tree x = get_nth_callarg (t, i);
+		   expression the address will be folded away, so look
-            /* A call to a non-static member function takes the
+		   through it now.  */
-               address of the object as the first argument.
+		if (DECL_NONSTATIC_MEMBER_FUNCTION_P (fun)
-               But in a constant expression the address will be folded
-	       away, so look through it now.  */
-            if (i == 0 && DECL_NONSTATIC_MEMBER_P (fun)
 		    && !DECL_CONSTRUCTOR_P (fun))
 		  {
+		    tree x = get_nth_callarg (t, 0);
 		    if (is_this_parameter (x))
 		      /* OK.  */;
 		    else if (!potential_constant_expression_1 (x, rval, flags))
 		      {
 			if (flags & tf_error)
-		      error ("object argument is not a potential constant "
+			  error ("object argument is not a potential "
-			     "expression");
+				 "constant expression");
+			return false;
+		      }
+		    i = 1;
+		  }
+	      }
+	    else
+	      fun = get_first_fn (fun);
+	    /* Skip initial arguments to base constructors.  */
+	    if (DECL_BASE_CONSTRUCTOR_P (fun))
+	      i = num_artificial_parms_for (fun);
+	    fun = DECL_ORIGIN (fun);
+	  }
+	else
+          {
+	    if (potential_constant_expression_1 (fun, rval, flags))
+	      /* Might end up being a constant function pointer.  */;
+	    else
+	      {
+		if (flags & tf_error)
+		  error ("%qE is not a function name", fun);
 		return false;
 	      }
           }
-	    else if (!potential_constant_expression_1 (x, rval, flags))
+        for (; i < nargs; ++i)
+          {
+            tree x = get_nth_callarg (t, i);
+	    if (!potential_constant_expression_1 (x, rval, flags))
 	      {
 		if (flags & tf_error)
 		  error ("argument in position %qP is not a "

gcc/testsuite/ChangeLog

@@ -1,5 +1,7 @@
 2011-04-07  Jason Merrill  <jason@redhat.com>
 
+	* g++.dg/cpp0x/regress/call1.C: New.
+
 	* g++.dg/cpp0x/variadic107.C: New.
 
 	* g++.dg/cpp0x/sfinae11.C: New.

gcc/testsuite/g++.dg/cpp0x/regress/call1.C

@@ -0,0 +1,13 @@
+// PR c++/48500
+// { dg-options -std=c++0x }
+
+struct linked_ptr {
+};
+template <typename T> linked_ptr make_linked_ptr(T* ptr);
+struct Concrete;
+struct NewedClass {
+  NewedClass(const Concrete& req){}
+};
+template<typename ArgT> void AddObjToChange(const ArgT& req) {
+  linked_ptr p = make_linked_ptr(new NewedClass(req));
+}