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expand: Tweak a comment in implementation of macro_rules

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This commit is contained in:
Vadim Petrochenkov 2020-10-31 18:09:21 +03:00
parent 3478d7c360
commit 7652bc3f68
1 changed files with 11 additions and 9 deletions
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20
compiler/rustc_expand/src/mbe/transcribe.rs
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@ -232,17 +232,19 @@ pub(super) fn transcribe<'a>(
// the meta-var. // the meta-var.
let ident = MacroRulesNormalizedIdent::new(orignal_ident); let ident = MacroRulesNormalizedIdent::new(orignal_ident);
if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) { if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) {
if let MatchedNonterminal(ref nt) = cur_matched { if let MatchedNonterminal(nt) = cur_matched {
// FIXME #2887: why do we apply a mark when matching a token tree meta-var let token = if let NtTT(tt) = &**nt {
// (e.g. `$x:tt`), but not when we are matching any other type of token // `tt`s are emitted into the output stream directly as "raw tokens",
// tree? // without wrapping them into groups.
if let NtTT(ref tt) = **nt { tt.clone()
result.push(tt.clone().into());
} else { } else {
// Other variables are emitted into the output stream as groups with
// `Delimiter::None` to maintain parsing priorities.
// `Interpolated` is currenty used for such groups in rustc parser.
marker.visit_span(&mut sp); marker.visit_span(&mut sp);
let token = TokenTree::token(token::Interpolated(nt.clone()), sp); TokenTree::token(token::Interpolated(nt.clone()), sp)
result.push(token.into()); };
} result.push(token.into());
} else { } else {
// We were unable to descend far enough. This is an error. // We were unable to descend far enough. This is an error.
return Err(cx.struct_span_err( return Err(cx.struct_span_err(