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expand: Tweak a comment in implementation of macro_rules #78603

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Nov 1, 2020
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expand: Tweak a comment in implementation of macro_rules #78603

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20 changes: 11 additions & 9 deletions compiler/rustc_expand/src/mbe/transcribe.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -232,17 +232,19 @@ pub(super) fn transcribe<'a>(
// the meta-var.
let ident = MacroRulesNormalizedIdent::new(orignal_ident);
if let Some(cur_matched) = lookup_cur_matched(ident, interp, &repeats) {
if let MatchedNonterminal(ref nt) = cur_matched {
// FIXME #2887: why do we apply a mark when matching a token tree meta-var
// (e.g. `$x:tt`), but not when we are matching any other type of token
// tree?
if let NtTT(ref tt) = **nt {
result.push(tt.clone().into());
if let MatchedNonterminal(nt) = cur_matched {
let token = if let NtTT(tt) = &**nt {
// `tt`s are emitted into the output stream directly as "raw tokens",
// without wrapping them into groups.
tt.clone()
} 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);
let token = TokenTree::token(token::Interpolated(nt.clone()), sp);
result.push(token.into());
}
TokenTree::token(token::Interpolated(nt.clone()), sp)
};
result.push(token.into());
} else {
// We were unable to descend far enough. This is an error.
return Err(cx.struct_span_err(
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