Bump syn from 1.0.58 to 1.0.64

[dependabot]

⚠️ Dependabot is rebasing this PR ⚠️

If you make any changes to it yourself then they will take precedence over the rebase.

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Bumps syn from 1.0.58 to 1.0.64.

Release notes

Sourced from syn's releases.

1.0.64

• Avoid clippy::expl_impl_clone_on_copy pedantic lint in downstream custom token types (#976)

1.0.63

• Fix parsing associated types with empty trait bound list after colon (#974)

1.0.62

• Republish to work around docs.rs bug rust-lang/docs.rs#1300

1.0.61

• Improve assertion failures on invalid use of Punctuated API (#970, thanks @​osa1)
• Add Lifetime::span and Lifetime::set_span accessors (#971)

1.0.60

• Provide an idiom for testing exhaustiveness of pattern matches on Expr, Type, Pat, Item, ForeignItem, TraitItem, and ImplItem (#694)

  match expr {
      Expr::Array(e) => {...}
      Expr::Assign(e) => {...}
      ...
      Expr::Yield(e) => {...}
  #[cfg(test)]
  Expr::__TestExhaustive(_) => unimplemented!(),
  #[cfg(not(test))]
  _ => { /* some sane fallback */ }
  
  }

  The above is the only supported idiom for exhaustive matching of those enum. Do not write anything differently as it is not supported.

  The conditional compilation on match-arms lets us fail your tests but not break your library when adding a variant. You will be notified by a test failure when a variant is added, so that you can add code to handle it, but your library will continue to compile and work for downstream users in the interim.

1.0.59

• Parse empty supertrait lists consistently with rustc (#952)
• Fix loss of span information on comma tokens inside of Type::Tuple during parse (#959)

Commits

• f0bc2d2 Release 1.0.64
• c2abcc0 Merge pull request #977 from dtolnay/explclone
• be5653c Suppress expl_impl_clone_on_copy pedantic lint in custom tokens
• 92b1129 Release 1.0.63
• 8ca66e5 Merge pull request #975 from dtolnay/emptybounds
• 79e357c Permit empty trait bounds after colon on type item
• e39fca3 Add regression test for issue 974
• 78f78ab Remove doc cfg attribute on impl on private type
• 5532e28 Release 1.0.62
• d131635 Release 1.0.61
• Additional commits viewable in compare view

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[dependabot]

The following labels could not be found: cargo, dependencies.

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.