| //! 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 crate::errors; |
| use rustc_ast as ast; |
| use rustc_ast::token; |
| use rustc_ast::tokenstream::TokenStream; |
| use rustc_attr as attr; |
| use rustc_errors::PResult; |
| use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult}; |
| use rustc_span::Span; |
| |
| pub(crate) fn expand_cfg( |
| cx: &mut ExtCtxt<'_>, |
| sp: Span, |
| tts: TokenStream, |
| ) -> MacroExpanderResult<'static> { |
| let sp = cx.with_def_site_ctxt(sp); |
| |
| ExpandResult::Ready(match parse_cfg(cx, sp, tts) { |
| Ok(cfg) => { |
| let matches_cfg = attr::cfg_matches( |
| &cfg, |
| &cx.sess, |
| cx.current_expansion.lint_node_id, |
| Some(cx.ecfg.features), |
| ); |
| MacEager::expr(cx.expr_bool(sp, matches_cfg)) |
| } |
| Err(err) => { |
| let guar = err.emit(); |
| DummyResult::any(sp, guar) |
| } |
| }) |
| } |
| |
| fn parse_cfg<'a>(cx: &ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> { |
| let mut p = cx.new_parser_from_tts(tts); |
| |
| if p.token == token::Eof { |
| return Err(cx.dcx().create_err(errors::RequiresCfgPattern { span })); |
| } |
| |
| let cfg = p.parse_meta_item()?; |
| |
| let _ = p.eat(&token::Comma); |
| |
| if !p.eat(&token::Eof) { |
| return Err(cx.dcx().create_err(errors::OneCfgPattern { span })); |
| } |
| |
| Ok(cfg) |
| } |