syntax: Tweak path parsing logic #37290
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jseyfried
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Oct 20, 2016
| impl LookaheadBuffer { | ||
| fn len(&self) -> usize { | ||
| let shift = if self.start <= self.end { 0 } else { LOOKAHEAD_BUFFER_CAPACITY }; | ||
| shift + self.end - self.start |
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nit: I believe this can be slightly simplified to
(LOOKAHEAD_BUFFER_CAPACITY + self.end - self.start) % LOOKAHEAD_BUFFER_CAPACITYThere was a problem hiding this comment.
Yep, looks simpler.
| end: usize, | ||
| } | ||
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|
||
| const LOOKAHEAD_BUFFER_CAPACITY: usize = 8; |
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Is there a reason this is 8? I think 6 would suffice.
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x % LOOKAHEAD_BUFFER_CAPACITY is faster.
Not much difference either way, though.
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Good point -- I forgot about peephole optimizations.
| @@ -5961,10 +5968,8 @@ impl<'a> Parser<'a> { | |||
| maybe_append(attrs, extra_attrs)); | |||
| return Ok(Some(item)); | |||
| } | |||
| if self.check_keyword(keywords::Union) && | |||
| self.look_ahead(1, |t| t.is_ident() && !t.is_any_keyword()) { | |||
| if self.eat_keyword(keywords::Union) { | |||
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I think this would break the macro invocation union!(); in an item position.
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Hmm, right, will fix.
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@bors r=jseyfried |
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📌 Commit fea630e has been approved by |
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syntax: Tweak path parsing logic Associated paths starting with `<<` are parsed in patterns. Paths like `self::foo::bar` are interpreted as paths and not as `self` arguments in methods (cc @matklad). Now, I believe, *all* paths are consistently parsed greedily in case of ambiguity. Detection of `&'a mut self::` requires pretty large (but still fixed) lookahead, so I had to increase the size of parser's lookahead buffer. Curiously, if `lookahead_distance >= lookahead_buffer_size` was used previously, the parser hung forever, I fixed this as well, now it ICEs. r? @jseyfried
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GuillaumeGomez
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add test for rust-lang#37765 Adds a test for rust-lang#37765, a path parsing fix which removes the need for a parenthesis workaround. Closes rust-lang#37765. cc rust-lang#37290 @withoutboats r? @petrochenkov
GuillaumeGomez
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add test for rust-lang#37765 Adds a test for rust-lang#37765, a path parsing fix which removes the need for a parenthesis workaround. Closes rust-lang#37765. cc rust-lang#37290 @withoutboats r? @petrochenkov
nikomatsakis
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Associated paths starting with
<<are parsed in patterns.Paths like
self::foo::barare interpreted as paths and not asselfarguments in methods (cc @matklad).Now, I believe, all paths are consistently parsed greedily in case of ambiguity.
Detection of
&'a mut self::requires pretty large (but still fixed) lookahead, so I had to increase the size of parser's lookahead buffer.Curiously, if
lookahead_distance >= lookahead_buffer_sizewas used previously, the parser hung forever, I fixed this as well, now it ICEs.r? @jseyfried