Bump syn from 1.0.109 to 2.0.68

[dependabot]

Bumps syn from 1.0.109 to 2.0.68.

Release notes

Sourced from syn's releases.

2.0.68

• Improve panic location when parse_quote! parses invalid syntax (#1690, thanks @​stepancheg)
• More efficient peek implementation for Group and Lifetime (#1687)

2.0.67

• Produce more accurate error message locations for errors located at the end of a nested group (#1679, #1680)
• Support peeking LitCStr in ParseStream::peek (#1682)

2.0.66

• Allow braced structs when parsing ExprLet (#1671)

2.0.65

• Optimize the implementation of Fold to compile faster (#1666, #1667, #1668)

2.0.64

• Support using ParseBuffer across catch_unwind (#1646)
• Validate that the expression in a let-else ends in brace as required by rustc (#1648, #1649)
• Legalize invalid const generic arguments by wrapping in braces (#1654, #1655)
• Fix some expression precedence edge cases involving break and return in loop headers (#1656)
• Always print closure bodies with a brace when the closure has an explicit return type (#1658)
• Automatically insert necessary parentheses in ToTokens for Expr when required by expression precedence (#1659)
• Support struct literal syntax in match guard expressions (#1662)

2.0.63

• Parse and print long if-else-if chains without reliance on deep recursion to avoid overflowing stack (#1644, #1645)

2.0.62

• Reject invalid unparenthesized range and comparison operator expressions (#1642, #1643)

2.0.61

• Check for legal binding name in the ident of Pat::Ident (#1627)
• Resolve unexpected_cfgs warning (#1635)

2.0.60

• Improve how None-delimited groups are counted by peek (#1625)

2.0.59

• Parse c"…" and cr"…" C-string literal syntax as Lit::CStr (#1502)

2.0.58

• Support $ in custom_punctuation! macro (#1611)

2.0.57

• Eliminate dependency on quote when built with default-features disabled and the "proc-macro" feature enabled (#1608, thanks @​BD103)

2.0.56

• Apply RUSTC_WORKSPACE_WRAPPER when deciding whether to run nightly-only tests (#1605)

2.0.55

• Restore compatibility with rustc 1.56 through 1.59 (#1603)

... (truncated)

Commits

• ecb0429 Release 2.0.68
• 37edbd2 Merge pull request #1690 from stepancheg/track-called
• 4338772 track-caller in parse_quote_spanned
• 537b0c5 Update test suite to nightly-2024-06-22
• b088d5c Merge pull request #1688 from dtolnay/peeklit
• 9b4e478 Relocate Lit peek impls into lit module
• 38f2ddb Merge pull request #1687 from dtolnay/fastpeek
• ef20bfd Optimize the peek impl of Group and Lifetime
• 4b6c96a Merge pull request #1686 from dtolnay/isempty
• 87d5792 Reword explanation of ParseBuffer::is_empty
• Additional commits viewable in compare view

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[dependabot]

Superseded by #189.