rustc_builtin_macros/
iter.rs

1use rustc_ast::tokenstream::TokenStream;
2use rustc_ast::{CoroutineKind, CoroutineMarker, Expr, ast, token};
3use rustc_errors::PResult;
4use rustc_expand::base::{self, DummyResult, ExpandResult, ExtCtxt, MacroExpanderResult};
5use rustc_span::Span;
6
7pub(crate) fn expand<'cx>(
8    cx: &'cx mut ExtCtxt<'_>,
9    sp: Span,
10    tts: TokenStream,
11) -> MacroExpanderResult<'cx> {
12    let closure = match parse_closure(cx, sp, tts) {
13        Ok(parsed) => parsed,
14        Err(err) => {
15            return ExpandResult::Ready(DummyResult::any(sp, err.emit()));
16        }
17    };
18
19    ExpandResult::Ready(base::MacEager::expr(closure))
20}
21
22fn parse_closure<'a>(
23    cx: &mut ExtCtxt<'a>,
24    span: Span,
25    stream: TokenStream,
26) -> PResult<'a, Box<Expr>> {
27    let mut closure_parser = cx.new_parser_from_tts(stream);
28
29    let coroutine_marker = Some(CoroutineMarker::new(CoroutineKind::Gen, span));
30
31    let mut closure = closure_parser.parse_expr()?;
32    match &mut closure.kind {
33        ast::ExprKind::Closure(c) => {
34            if let Some(marker) = c.coroutine_marker {
35                cx.dcx().span_err(marker.span, "only plain closures allowed in `iter!`");
36            }
37            c.coroutine_marker = coroutine_marker;
38            if closure_parser.token != token::Eof {
39                closure_parser.unexpected()?;
40            }
41            Ok(closure)
42        }
43        _ => {
44            cx.dcx().span_err(closure.span, "`iter!` body must be a closure");
45            Err(closure_parser.unexpected().unwrap_err())
46        }
47    }
48}
rustc_builtin_macros/iter.rs

rustc_builtin_macros/
iter.rs
