The clever hack of '#define __has_include __has_include' breaks -dD
and -fdirectives-only, because that emits definitions. This turns
__has_include into a proper builtin macro. Thus it's never emitted
via -dD, and because use outside of directive processing is undefined,
we can just expand it anywhere.
PR preprocessor/93452
* internal.h (struct spec_nodes): Drop n__has_include{,_next}.
* directives.c (lex_macro_node): Don't check __has_include redef.
* expr.c (eval_token): Drop __has_include eval.
(parse_has_include): Move to ...
* macro.c (builtin_has_include): ... here.
(_cpp_builtin_macro_text): Eval __has_include{,_next}.
* include/cpplib.h (enum cpp_builtin_type): Add BT_HAS_INCLUDE{,_NEXT}.
* init.c (builtin_array): Add them.
(cpp_init_builtins): Drop __has_include{,_next} init here ...
* pch.c (cpp_read_state): ... and here.
* traditional.c (enum ls): Drop has_include states ...
(_cpp_scan_out_logical_line): ... and here.
