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|
//! 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 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::{self, *};
use rustc_macros::SessionDiagnostic;
use rustc_span::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.sess.parse_sess,
cx.current_expansion.lint_node_id,
cx.ecfg.features,
);
MacEager::expr(cx.expr_bool(sp, matches_cfg))
}
Err(mut err) => {
err.emit();
DummyResult::any(sp)
}
}
}
#[derive(SessionDiagnostic)]
#[diag(builtin_macros::requires_cfg_pattern)]
struct RequiresCfgPattern {
#[primary_span]
#[label]
span: Span,
}
#[derive(SessionDiagnostic)]
#[diag(builtin_macros::expected_one_cfg_pattern)]
struct OneCfgPattern {
#[primary_span]
span: Span,
}
fn parse_cfg<'a>(cx: &mut 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.create_err(RequiresCfgPattern { span }));
}
let cfg = p.parse_meta_item()?;
let _ = p.eat(&token::Comma);
if !p.eat(&token::Eof) {
return Err(cx.create_err(OneCfgPattern { span }));
}
Ok(cfg)
}
|
