fix(query): prevent cross-branch capture contamination in alternations with quantifiers#5317
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WillLillis merged 1 commit intotree-sitter:masterfrom Feb 10, 2026
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…s with quantifiers When a branch inside an alternation has a + or * quantifier, the quantifier's pass_through step loops back to the branch's first step. The alternation linking also sets that step's alternative_index to point to the next branch. This causes the quantifier loop-back to incorrectly explore other branches in the case of a failed match that follows a successful match, contaminating captures. This is corrected by redirecting the quantifier loop-back to a "clean" copy of the target step without the alternative index pointing to the next alternation branch. Co-authored-by: Riley Bruins <ribru17@hotmail.com>
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amaanq
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Feb 10, 2026
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Successfully created backport PR for |
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awesome fix!! |
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When a branch inside an alternation has a + or * quantifier, the quantifier's pass_through step loops back to the branch's first step. The alternation linking also sets that step's alternative_index to point to the next branch. This causes the quantifier loop-back to incorrectly explore other branches in the case of a failed match that follows a successful match, contaminating captures.
This is corrected by redirecting the quantifier loop-back to a "clean" copy of the target step without the alternative index pointing to the next alternation branch.
CC @ribru17 Thanks for providing such a nice report and test case for this bug!