PR c++/71446
	* cp-tree.h (CONSTRUCTOR_IS_DESIGNATED_INIT): Define.
	* parser.c (cp_parser_braced_list): Adjust cp_parser_initializer_list
	caller, set CONSTRUCTOR_IS_DESIGNATED_INIT.
	(cp_parser_initializer_list): Add designated parameter, set *designated
	to a bool whether any designators were parsed.
	* decl.c (reshape_init): Copy over CONSTRUCTOR_IS_DESIGNATED_INIT if
	needed.
	* pt.c (tsubst_copy_and_build): Likewise.
	* call.c (implicit_conversion): If CONSTRUCTOR_IS_DESIGNATED_INIT,
	don't call build_list_conv, nor build_complex_conv, nor attempt to
	convert a single element initializer to scalar.

	* g++.dg/cpp2a/desig10.C: New test.
	* g++.dg/cpp2a/desig11.C: New test.
	* g++.dg/ext/desig4.C: Expect 4 new errors.

From-SVN: r269340