Fix #11545: while-true-if-break: Variable might not be defined

[phpstan-bot]

Summary

When a loop with an always-true condition (while(true), for(;;), do...while(true)) exits only through a break inside an if block, variables assigned before the break were incorrectly reported as "might not be defined" after the loop.

Changes

• Modified while loop handling in src/Analyser/NodeScopeResolver.php (around line 1519): when $alwaysIterates is true and there are break exit points, build $finalScope purely from break scopes instead of merging them into the unreachable body-end scope
• Modified do-while loop handling in src/Analyser/NodeScopeResolver.php (around line 1636): same fix applied
• Modified for loop handling in src/Analyser/NodeScopeResolver.php (around line 1758): same fix for break scope construction, plus skip merging with pre-loop scope when $alwaysIterates is true
• Added regression test in tests/PHPStan/Rules/Variables/data/bug-11545.php covering while(true), for(;;), and do...while(true) variants
• Added test method testBug11545 in tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php

Root cause

When processing loops, PHPStan constructs a $finalScope representing the state after the loop exits. For while(true), this starts with $finalScopeResult->getScope()->filterByFalseyValue($stmt->cond) — the scope where the condition true is falsey, which is effectively unreachable. Break exit point scopes were then merged into this unreachable scope using mergeWith(). The mergeWith() method treats a variable existing in one scope but not the other as "maybe defined" (TrinaryLogic::Maybe). Since the unreachable scope doesn't have the variable $result, merging produces "maybe" certainty instead of "yes".

The fix recognizes that when a loop always iterates, the only way to reach post-loop code is through a break statement. Therefore, the post-loop scope should be constructed entirely from the break exit point scopes, not merged with the unreachable body-end scope.

Test

Added tests/PHPStan/Rules/Variables/data/bug-11545.php with three functions testing while(true), for(;;), and do...while(true) loops where the only exit is a break inside an if block that also assigns a variable. The test expects zero errors, confirming the variable is considered definitely defined after the loop.

Fixes phpstan/phpstan#11545

Closes phpstan/phpstan#10245
Closes phpstan/phpstan#11984
Closes phpstan/phpstan#5477
Closes phpstan/phpstan#5919
Closes phpstan/phpstan#9023