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Follow-up to #68848 #69150

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merged 2 commits into from
Feb 15, 2020
Merged

Follow-up to #68848 #69150

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dbd8220
Avoid `base_parser`, it's not needed.
nnethercote Feb 4, 2020
88b0912
Fix a typo in a variable name.
nnethercote Feb 10, 2020
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32 changes: 15 additions & 17 deletions src/librustc_expand/mbe/macro_rules.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -191,9 +191,9 @@ fn generic_extension<'cx>(
let mut best_failure: Option<(Token, &str)> = None;

// We create a base parser that can be used for the "black box" parts.
// Every iteration needs a fresh copy of that base parser. However, the
// parser is not mutated on many of the iterations, particularly when
// dealing with macros like this:
// Every iteration needs a fresh copy of that parser. However, the parser
// is not mutated on many of the iterations, particularly when dealing with
// macros like this:
//
// macro_rules! foo {
// ("a") => (A);
Expand All @@ -209,11 +209,9 @@ fn generic_extension<'cx>(
// hacky, but speeds up the `html5ever` benchmark significantly. (Issue
// 68836 suggests a more comprehensive but more complex change to deal with
// this situation.)
let base_parser = base_parser_from_cx(&cx.current_expansion, &cx.parse_sess, arg.clone());
let parser = parser_from_cx(&cx.current_expansion, &cx.parse_sess, arg.clone());

for (i, lhs) in lhses.iter().enumerate() {
let mut parser = Cow::Borrowed(&base_parser);

// try each arm's matchers
let lhs_tt = match *lhs {
mbe::TokenTree::Delimited(_, ref delim) => &delim.tts[..],
Expand All @@ -224,13 +222,14 @@ fn generic_extension<'cx>(
// This is used so that if a matcher is not `Success(..)`ful,
// then the spans which became gated when parsing the unsuccessful matcher
// are not recorded. On the first `Success(..)`ful matcher, the spans are merged.
let mut gated_spans_snaphot = mem::take(&mut *cx.parse_sess.gated_spans.spans.borrow_mut());
let mut gated_spans_snapshot =
mem::take(&mut *cx.parse_sess.gated_spans.spans.borrow_mut());

match parse_tt(&mut parser, lhs_tt) {
match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt) {
Success(named_matches) => {
// The matcher was `Success(..)`ful.
// Merge the gated spans from parsing the matcher with the pre-existing ones.
cx.parse_sess.gated_spans.merge(gated_spans_snaphot);
cx.parse_sess.gated_spans.merge(gated_spans_snapshot);

let rhs = match rhses[i] {
// ignore delimiters
Expand Down Expand Up @@ -291,9 +290,9 @@ fn generic_extension<'cx>(

// The matcher was not `Success(..)`ful.
// Restore to the state before snapshotting and maybe try again.
mem::swap(&mut gated_spans_snaphot, &mut cx.parse_sess.gated_spans.spans.borrow_mut());
mem::swap(&mut gated_spans_snapshot, &mut cx.parse_sess.gated_spans.spans.borrow_mut());
}
drop(base_parser);
drop(parser);

let (token, label) = best_failure.expect("ran no matchers");
let span = token.span.substitute_dummy(sp);
Expand All @@ -311,9 +310,8 @@ fn generic_extension<'cx>(
mbe::TokenTree::Delimited(_, ref delim) => &delim.tts[..],
_ => continue,
};
let base_parser =
base_parser_from_cx(&cx.current_expansion, &cx.parse_sess, arg.clone());
match parse_tt(&mut Cow::Borrowed(&base_parser), lhs_tt) {
let parser = parser_from_cx(&cx.current_expansion, &cx.parse_sess, arg.clone());
match parse_tt(&mut Cow::Borrowed(&parser), lhs_tt) {
Success(_) => {
if comma_span.is_dummy() {
err.note("you might be missing a comma");
Expand Down Expand Up @@ -395,8 +393,8 @@ pub fn compile_declarative_macro(
),
];

let base_parser = Parser::new(sess, body, None, true, true, rustc_parse::MACRO_ARGUMENTS);
let argument_map = match parse_tt(&mut Cow::Borrowed(&base_parser), &argument_gram) {
let parser = Parser::new(sess, body, None, true, true, rustc_parse::MACRO_ARGUMENTS);
let argument_map = match parse_tt(&mut Cow::Borrowed(&parser), &argument_gram) {
Success(m) => m,
Failure(token, msg) => {
let s = parse_failure_msg(&token);
Expand Down Expand Up @@ -1212,7 +1210,7 @@ fn quoted_tt_to_string(tt: &mbe::TokenTree) -> String {
}
}

fn base_parser_from_cx<'cx>(
fn parser_from_cx<'cx>(
current_expansion: &'cx ExpansionData,
sess: &'cx ParseSess,
tts: TokenStream,
Expand Down