P0490R0 GB 20: decomposition declaration should commit to tuple
interpretation early
* decl.c (get_tuple_size): Make static. If inst is error_mark_node
or non-complete type, return NULL_TREE, otherwise if
lookup_qualified_name fails or doesn't fold into INTEGER_CST, return
error_mark_node.
(get_tuple_element_type, get_tuple_decomp_init): Make static.
(cp_finish_decomp): Pass LOC to get_tuple_size. If it returns
error_mark_node, complain and fail.
* g++.dg/cpp1z/decomp10.C (f1): Adjust expected diagnostics.
git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@243724 138bc75d-0d04-0410-961f-82ee72b054a4