Rust grammar has an ambiguity where braces sometimes turn a path expression into a struct initialization and sometimes do not. In the following code, the expression S {} is one expression. Presumably there is an empty struct struct S {} defined somewhere which it is instantiating.
let _ = *S {};
// parsed by rustc as: *(S {})
We would want to parse the above using Expr::parse after the = token.
But in the following, S {} is not a struct init expression.
if *S {} {}
// parsed by rustc as:
//
// if (S) {
// / empty block /
// }
// {
// / another empty block */
// }
For that reason we would want to parse if-conditions using Expr::parse_without_eager_brace after the if token. Same for similar syntactic positions such as the condition expr after a while token or the expr at the top of a match.
The Rust grammar's choices around which way this ambiguity is resolved at various syntactic positions is fairly arbitrary. Really either parse behavior could work in most positions, and language designers just decide each case based on which is more likely to be what the programmer had in mind most of the time.
if return S {} {}
// parsed by rustc as:
//
// if (return (S {})) {
// }
//
// but could equally well have been this other arbitrary choice:
//
// if (return S) {
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Bumps syn from 0.15.40 to 1.0.34.
Release notes
Sourced from syn's releases.
Commits
2f88d8f
Release 1.0.344913b10
Add example expansion to parse_macro_input documentationd5bdf68
Update test suite to nightly-2020-07-115d540a2
Update test suite to nightly-2020-06-27f3f73c7
Merge pull request 859 from aaronabramov/patch-1fb2597c
Addextra-traits
feature docs in file.rsab00f48
Release 1.0.33575e43a
Optimize token peek implsab9eb76
Add Parse impls for Option of individual token1dc916f
Swap impl_token macro argsDependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting
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