Fix false positive match.alwaysTrue with consecutive match(true) expressions#5296
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gnutix wants to merge 1 commit intophpstan:2.1.xfrom
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Fix false positive match.alwaysTrue with consecutive match(true) expressions#5296gnutix wants to merge 1 commit intophpstan:2.1.xfrom
gnutix wants to merge 1 commit intophpstan:2.1.xfrom
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…cutive match(true) expressions After an exhaustive match(true) with a throwing default arm, the post-match scope carried conditional expressions encoding relationships between arm-narrowed types (e.g. "if equals(A) is false, then equals(B) is true"). When a subsequent match(true) filtered by falsey for the first arm, these conditional expressions activated and incorrectly narrowed the second arm's condition to true. The fix restores the pre-match conditional expressions after the arm body scope merge, preventing match-internal type relationships from leaking into the post-match scope.
gnutix
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No fix is needed, this is expected behaviour. |
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Fixes phpstan/phpstan#14368
Summary
match(true)with a throwing default arm, the post-match scope carried conditional expressions encoding relationships between arm-narrowed types (e.g. "ifequals(A)is false, thenequals(B)is true")match(true)filtered by falsey for the first arm, these conditional expressions activated and incorrectly narrowed the second arm's condition totrue, causing a false positivematch.alwaysTrueRoot cause
PR #5066 (fix #9601) changed
MatchHandlerto exclude always-terminating arms (e.g.default => throw ...) from the arm body scope merge. This is correct for type resolution, but themergeWithcall also createsconditionalExpressionsthat encode relationships between the narrowed types of different arms. These conditional expressions survived into the post-match scope and were activated by subsequent code that narrowed the same expressions.