Bump syn from 0.15.40 to 1.0.34

[dependabot-preview[bot]]

Bumps syn from 0.15.40 to 1.0.34.

Release notes

Sourced from syn's releases.

1.0.33

• Parse tuple.0.0 as an indexing expression (rust-lang/rust#71322)
• Add Parse impls for optional of proc-macro2 types: Option<TokenTree>, Option<Punct>, Option<Literal>, Option<Group>

1.0.32

• Fix parsing $:item macro_rules metavariables containing outer attributes (#852)

1.0.31

• Add Expr::parse_without_eager_brace to parse expressions in ambiguous syntactic position.

  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) {
  

Commits

• 2f88d8f Release 1.0.34
• 4913b10 Add example expansion to parse_macro_input documentation
• d5bdf68 Update test suite to nightly-2020-07-11
• 5d540a2 Update test suite to nightly-2020-06-27
• f3f73c7 Merge pull request 859 from aaronabramov/patch-1
• fb2597c Add extra-traits feature docs in file.rs
• ab00f48 Release 1.0.33
• 575e43a Optimize token peek impls
• ab9eb76 Add Parse impls for Option of individual token
• 1dc916f Swap impl_token macro args
• Additional commits viewable in compare view

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[dependabot-preview[bot]]

Superseded by #598.