[flake8-type-checking] Mark TC006 fix unsafe when it adds an escape#25792
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eyupcanakman wants to merge 1 commit into
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[flake8-type-checking] Mark TC006 fix unsafe when it adds an escape#25792eyupcanakman wants to merge 1 commit into
eyupcanakman wants to merge 1 commit into
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The TC006 autofix quotes the cast type expression. When a string inside it uses the same quote that wraps the result, the quoted output gains a backslash escape that type checkers reject inside a forward reference. Mark the fix unsafe when the quoted output would contain an escape so it is no longer auto-applied. Fixes astral-sh#22131.
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Summary
Fixes #22131.
The
TC006fix quotes the type expression intyping.cast(). When a string inside the expression uses the same quote character that wraps the result, the quoted output gains a backslash escape, for examplecast(Literal["'"], "'")becomescast("Literal[\"'\"]", "'"). ty rejects an escape sequence inside a forward reference, so the auto-applied fix turns valid code into code that fails type checking.A single-character quote can't always avoid the escape, so the fix is now marked unsafe whenever the quoted output would contain one. Expressions that quote cleanly keep the safe fix. Producing an escape-free quoted form would need triple-quoted output, which is a larger change to the string generator and can follow separately.
Test Plan
Added two fixture cases to
TC006.py, one with an apostrophe and one with a double-quote value, and confirmed the snapshot marks both as unsafe fixes while the existing safe cases stay unchanged.