Fix phpstan/phpstan#14274: "Variable might not be defined" false positive

[phpstan-bot]

Summary

Fixes a false positive "Variable might not be defined" error when maybe-defined variables are guarded by a boolean flag inside complex boolean expressions (|| combined with &&). The issue occurred when multiple if blocks used the same guarded variables, and an unrelated variable assignment in an if body caused the conditional expression holders to be incorrectly dropped.

Changes

• Modified MutatingScope::invalidateExpression() in src/Analyser/MutatingScope.php to filter ConditionalExpressionHolder instances individually rather than dropping all holders for a variable when any single holder has an invalidated condition guard
• Added regression test in tests/PHPStan/Rules/Variables/data/bug-14274.php and corresponding test method in DefinedVariableRuleTest.php

Root cause

When invalidateExpression() was called (e.g., when assigning to $messages[]), the code used continue 3 to skip the entire set of ConditionalExpressionHolder instances for a variable if any holder had a condition guard matching the invalidated expression. This meant that if createConditionalExpressions() had added a spurious holder guarded by $messages (as a type guard) alongside the original holder guarded by $has_staged_update, invalidating $messages would also discard the $has_staged_update-guarded holder. This caused subsequent if blocks to lose the information that the variable was definitely defined when $has_staged_update was true.

The fix changes the logic to filter holders individually: only holders whose condition guards match the invalidated expression are removed, while other holders for the same variable are preserved.

Test

The regression test reproduces the exact scenario from the issue: an if/else block that sets a boolean flag and defines variables via list assignment, followed by multiple if blocks using || with &&-guarded access to those variables. Without the fix, the third if block incorrectly reports "Variable might not be defined" for variables that are properly guarded by the boolean flag.

Fixes phpstan/phpstan#14274

[staabm]

needs a regression test for phpstan/phpstan#12373

[phpstan-bot]

The background make phpstan task completed successfully (exit code 0) — I already retrieved its output earlier showing "No errors". Everything is pushed and ready for review.

[phpstan-bot]

The review from staabm is APPROVED — no further changes are requested.

Looking at the PR diff and recent commits, the regression test for phpstan/phpstan#12373 that was previously requested has already been added:

• tests/PHPStan/Rules/Variables/data/bug-12373.php — test data file
• testBug12373() method in DefinedVariableRuleTest.php

The recent commits confirm this:

• 7a9437824 — "Add regression test for Unexpected "Variable $... might not be defined" phpstan#12373"
• 304c35e52 — "Update bug-12373.php"

Everything is already in order — no additional changes needed.