Fix Haskell lexer: handle escape sequences in character literals#3069
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birkenfeld merged 3 commits intopygments:masterfrom Mar 28, 2026
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The root-state pattern for character literals only matched single non-backslash characters like 'a'. Escape sequences like '\n', '\t', '\\' were incorrectly tokenized as Keyword.Type + Name fragments. Added a pattern for '\.' (backslash + any char) to match escape character literals, placed after the existing non-escape pattern. Fixes pygments#1795 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Thanks for the PR, can you add a test case? |
Covers '\n', '\t', '\\', and 'a' tokenization as Literal.String.Char. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Added in 0088b19 - snippet test covering |
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Looks like outputs for the existing tests need to be adjusted as well. |
Update expected token outputs for example.hs and Sudoku.lhs to reflect the new escape character literal tokenization.
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Regenerated the golden outputs for example.hs and Sudoku.lhs in 35edbc8. All Haskell tests passing locally. |
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LGTM now, thanks! |
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Thanks for the merge! |
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Summary
Fixes incorrect tokenization of Haskell escape character literals like
'\n','\t','\\'.Why this matters
The root-state regex
'[^\\]'only matched character literals containing a single non-backslash character. Escape sequences like'\n'were split across tokens -'\becameKeyword.Typeandn'becameName- producing wrong highlighting.Changes
pygments/lexers/haskell.pyline 57: Added pattern'\\.'to match escape character literals. Placed after the existing non-escape pattern so simple chars like'a'still match first.Testing
Verified all common cases tokenize as
Token.Literal.String.Char:'\n'(newline),'\t'(tab),'\\'(backslash),'a'(simple),'A'(uppercase)Fixes #1795
This contribution was developed with AI assistance (Claude Code).