mirror of https://github.com/rust-lang/rust
55 lines
1.5 KiB
Rust
55 lines
1.5 KiB
Rust
//! The compiler code necessary to support the cfg! extension, which expands to
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//! a literal `true` or `false` based on whether the given cfg matches the
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//! current compilation environment.
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use crate::errors;
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use rustc_ast as ast;
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use rustc_ast::token;
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use rustc_ast::tokenstream::TokenStream;
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use rustc_attr as attr;
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use rustc_errors::PResult;
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use rustc_expand::base::{DummyResult, ExpandResult, ExtCtxt, MacEager, MacroExpanderResult};
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use rustc_span::Span;
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pub(crate) fn expand_cfg(
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cx: &mut ExtCtxt<'_>,
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sp: Span,
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tts: TokenStream,
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) -> MacroExpanderResult<'static> {
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let sp = cx.with_def_site_ctxt(sp);
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ExpandResult::Ready(match parse_cfg(cx, sp, tts) {
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Ok(cfg) => {
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let matches_cfg = attr::cfg_matches(
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&cfg,
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&cx.sess,
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cx.current_expansion.lint_node_id,
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Some(cx.ecfg.features),
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);
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MacEager::expr(cx.expr_bool(sp, matches_cfg))
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}
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Err(err) => {
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let guar = err.emit();
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DummyResult::any(sp, guar)
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}
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})
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}
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fn parse_cfg<'a>(cx: &ExtCtxt<'a>, span: Span, tts: TokenStream) -> PResult<'a, ast::MetaItem> {
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let mut p = cx.new_parser_from_tts(tts);
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if p.token == token::Eof {
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return Err(cx.dcx().create_err(errors::RequiresCfgPattern { span }));
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}
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let cfg = p.parse_meta_item()?;
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let _ = p.eat(&token::Comma);
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if !p.eat(&token::Eof) {
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return Err(cx.dcx().create_err(errors::OneCfgPattern { span }));
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}
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Ok(cfg)
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}
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