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use syntax::ext::base::*;
use syntax::ext::base;
use syntax::ext::build::AstBuilder;
use syntax::attr;
use syntax::tokenstream;
use syntax::parse::token;
use syntax_pos::Span;
pub fn expand_cfg<'cx>(cx: &mut ExtCtxt,
sp: Span,
tts: &[tokenstream::TokenTree])
-> Box<base::MacResult + 'static> {
let mut p = cx.new_parser_from_tts(tts);
let cfg = panictry!(p.parse_meta_item());
if !p.eat(&token::Eof) {
cx.span_err(sp, "expected 1 cfg-pattern");
return DummyResult::expr(sp);
}
let matches_cfg = attr::cfg_matches(&cfg, cx.parse_sess, cx.ecfg.features);
MacEager::expr(cx.expr_bool(sp, matches_cfg))
}