blob: 3c33baf95a597705c44abc8f1baf21d82e746b31 [file] [log] [blame]
/// The compiler code necessary to support the cfg! extension, which expands to
/// a literal `true` or `false` based on whether the given cfg matches the
/// current compilation environment.
use errors::DiagnosticBuilder;
use syntax::ast;
use syntax::ext::base::{self, *};
use syntax::attr;
use syntax::tokenstream::TokenStream;
use syntax::parse::token;
use syntax_pos::Span;
pub fn expand_cfg(
cx: &mut ExtCtxt<'_>,
sp: Span,
tts: TokenStream,
) -> Box<dyn base::MacResult + 'static> {
let sp = cx.with_def_site_ctxt(sp);
match parse_cfg(cx, sp, tts) {
Ok(cfg) => {
let matches_cfg = attr::cfg_matches(&cfg, cx.parse_sess, cx.ecfg.features);
MacEager::expr(cx.expr_bool(sp, matches_cfg))
}
Err(mut err) => {
err.emit();
DummyResult::any(sp)
}
}
}
fn parse_cfg<'a>(
cx: &mut ExtCtxt<'a>,
sp: Span,
tts: TokenStream,
) -> Result<ast::MetaItem, DiagnosticBuilder<'a>> {
let mut p = cx.new_parser_from_tts(tts);
if p.token == token::Eof {
let mut err = cx.struct_span_err(sp, "macro requires a cfg-pattern as an argument");
err.span_label(sp, "cfg-pattern required");
return Err(err);
}
let cfg = p.parse_meta_item()?;
let _ = p.eat(&token::Comma);
if !p.eat(&token::Eof) {
return Err(cx.struct_span_err(sp, "expected 1 cfg-pattern"));
}
Ok(cfg)
}