PR c++/83937 - wrong C++17 handling of init-list ctor argument.

	* call.c (build_special_member_call): Don't convert an init-list
	argument directly to the class type.

From-SVN: r258594

gcc/cp/ChangeLog

+2018-03-16  Jason Merrill  <jason@redhat.com>
+
+	PR c++/83937 - wrong C++17 handling of init-list ctor argument.
+	* call.c (build_special_member_call): Don't convert an init-list
+	argument directly to the class type.
+
 2018-03-16  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c++/79937

gcc/cp/call.c

@@ -8827,7 +8827,12 @@ build_special_member_call (tree instance, tree name, vec<tree, va_gc> **args,
 	/* If we're using this to initialize a non-temporary object, don't
 	   require the destructor to be accessible.  */
 	sub_complain |= tf_no_cleanup;
-      if (!reference_related_p (class_type, TREE_TYPE (arg)))
+      if (BRACE_ENCLOSED_INITIALIZER_P (arg)
+	  && !CONSTRUCTOR_IS_DIRECT_INIT (arg))
+	/* An init-list arg needs to convert to the parm type (83937), so fall
+	   through to normal processing.  */
+	arg = error_mark_node;
+      else if (!reference_related_p (class_type, TREE_TYPE (arg)))
 	arg = perform_implicit_conversion_flags (class_type, arg,
 						 sub_complain,
 						 flags);

gcc/testsuite/g++.dg/cpp0x/initlist-ctor2.C

+// PR c++/83937
+// { dg-do run { target c++11 } }
+
+struct S
+{
+  S(int v = 42) {
+    if (v != int{})
+      __builtin_abort();
+  }
+};
+
+int main()
+{
+  S( {} );
+}