Ban ] as literal first character of custom character class
#404
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PCRE, Oniguruma, and ICU allow `]` to appear as the first member of a custom character class, and treat it as literal, due to empty character classes being invalid. However this behavior isn't particularly intuitive, and makes lexing heuristics harder to implement properly. Instead, reject such character classes as being empty, and require escaping if `]` is meant as the first character.
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@swift-ci please test |
milseman
approved these changes
May 12, 2022
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Wot? |
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PCRE, Oniguruma, and ICU allow
]to appear as the first member of a custom character class, and treat it as literal, due to empty character classes being invalid.However this behavior isn't particularly intuitive, and makes lexing heuristics such as swiftlang/swift#58835 harder to implement properly. Instead, reject such character classes as being empty, and require escaping if
]is meant as the first character.