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
