Lexer: Properly support Unicode 15.1.0 #4
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The previous lexer implementation in `Language.Rust.Parser.Lexer` was broken for Unicode characters with sufficiently large codepoints, as the previous implementation incorrectly attempted to port UTF-16–encoded codepoints over to `alex`, which is UTF-8–encoded. Rather than try to fix the previous implementation (which was based on old `rustc` code that is no longer used), this ports the lexer to a new implementation that is based on the Rust `unicode-xid` crate (which is how modern versions of `rustc` lex Unicode characters). Specifically: * This adapts `unicode-xid`'s lexer generation script to generate an `alex`-based lexer instead of a Rust-based one. * The new lexer is generated to support codepoints from Unicode 15.1.0. (It is unclear which exact Unicode version the previous lexer targeted, but given that it was last updated in 2016, it was likely quite an old version.) * I have verified that the new lexer can lex exotic Unicode characters such as `𝑂` and `𐌝` by adding them as regression tests. Fixes #3.
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The previous lexer implementation in
Language.Rust.Parser.Lexerwas broken for Unicode characters with sufficiently large codepoints, as the previous implementation incorrectly attempted to port UTF-16–encoded codepoints over toalex, which is UTF-8–encoded. Rather than try to fix the previous implementation (which was based on oldrustccode that is no longer used), this ports the lexer to a new implementation that is based on the Rustunicode-xidcrate (which is how modern versions ofrustclex Unicode characters). Specifically:This adapts
unicode-xid's lexer generation script to generate analex-based lexer instead of a Rust-based one.The new lexer is generated to support codepoints from Unicode 15.1.0. (It is unclear which exact Unicode version the previous lexer targeted, but given that it was last updated in 2016, it was likely quite an old version.)
I have verified that the new lexer can lex exotic Unicode characters such as
𝑂and𐌝by adding them as regression tests.Fixes #3.