Bump syn from 0.15.40 to 1.0.33

[dependabot-preview]

Bumps syn from 0.15.40 to 1.0.33.

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) {

... (truncated)

Commits

• 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
• ec21045 Add test for peek syntax
• 433b5a1 Provide Parse impl for Option<Lit*> without features
• 41c5d57 Provide Parse impl for Option<Lifetime> without features
• 9da2eba Merge pull request #856 from dtolnay/tuple.0.0
• 53c64f8 Enable tuple multi index test
• f86f85c Parse tuple.0.0
• Additional commits viewable in compare view

Dependabot 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 @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)
• @dependabot use these labels will set the current labels as the default for future PRs for this repo and language
• @dependabot use these reviewers will set the current reviewers as the default for future PRs for this repo and language
• @dependabot use these assignees will set the current assignees as the default for future PRs for this repo and language
• @dependabot use this milestone will set the current milestone as the default for future PRs for this repo and language
• @dependabot badge me will comment on this PR with code to add a "Dependabot enabled" badge to your readme

Additionally, you can set the following in your Dependabot dashboard:

• Update frequency (including time of day and day of week)
• Pull request limits (per update run and/or open at any time)
• Out-of-range updates (receive only lockfile updates, if desired)
• Security updates (receive only security updates, if desired)

[dependabot-preview]

Superseded by #596.