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syntax: + has incorrect priority in trait object types starting with for #39317

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petrochenkov opened this issue Jan 26, 2017 · 0 comments · Fixed by #40043
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syntax: + has incorrect priority in trait object types starting with for #39317

petrochenkov opened this issue Jan 26, 2017 · 0 comments · Fixed by #40043
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A-parser Area: The parsing of Rust source code to an AST

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@petrochenkov
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&for<'a> Tr<'a> + Send is parsed as &(for<'a> Tr<'a> + Send) while RFC 438 tells that it should be parsed as (&for<'a> Tr<'a>) + Send and therefore be invalid.

Another example: Fn() -> for<'a> Tr<'a> + Send is parsed as Fn() -> (for<'a> Tr<'a> + Send) instead of (Fn() -> for<'a> Tr<'a>) + Send.

cc #39158 (comment)
@petrochenkov petrochenkov added the A-parser Area: The parsing of Rust source code to an AST label Feb 19, 2017
@petrochenkov petrochenkov self-assigned this Feb 19, 2017
@petrochenkov petrochenkov mentioned this issue Feb 23, 2017
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@petrochenkov petrochenkov mentioned this issue Mar 4, 2017
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bors added a commit that referenced this issue Mar 22, 2017
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Auto merge of #40043 - petrochenkov:objpars, r=nikomatsakis
8c4f2c6 
Refactor parsing of trait object types

Bugs are fixed and code is cleaned up.

User visible changes:
- `ty` matcher in macros accepts trait object types like `Write + Send` (#39080)
- Buggy priority of `+` in trait object types starting with `for` is fixed (#39317). `&for<'a> Trait<'a> + Send` is now parsed as `(&for<'a> Trait<'a>) + Send` and requires parens `&(for<'a> Trait<'a> + Send)`. For comparison, `&Send + for<'a> Trait<'a>` was parsed like this since [Nov 27, 2014](#19298).
- Trailing `+`s are supported in trait objects, like in other bounds.
- Better error reporting for trait objects starting with `?Sized`.

Fixes #39080
Fixes #39317 [breaking-change]
Closes #39298
cc #39085 (fixed, then reverted #40043 (comment))
cc #39318 (fixed, then reverted #40043 (comment))

r? @nikomatsakis
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Refactor parsing of trait object types petrochenkov/rust
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