Summary

Fixes a regression introduced in 3daa312 (Fix #13303) where PHPStan failed to narrow nullable types through chained conditional expression holders. When boolean variables like $exists = $obj !== null were used in compound conditions, the type of $obj was not properly narrowed inside subsequent if blocks.

Changes

• Modified MutatingScope::filterBySpecifiedTypes() in src/Analyser/MutatingScope.php to iterate over conditional expression holders in a loop until no new specified expressions are discovered (convergence loop)
• Updated tests/PHPStan/Analyser/nsrt/dependent-variable-certainty.php and tests/PHPStan/Analyser/nsrt/dependent-expression-certainty.php to reflect improved certainty (the comment "could be Yes" confirmed this was a known limitation)
• Added regression test tests/PHPStan/Analyser/nsrt/bug-14178.php

Root cause

The mergeConditionalExpressions() method introduced in 3daa312 changed the iteration order of conditional expression holders compared to the old array_merge() approach. Previously, new holders (from boolean conditions like !$a && !$b) came before existing holders (from assignments like $exists = $obj !== null). The new method reversed this order by starting with existing holders.

In filterBySpecifiedTypes(), conditional expression holders are processed in a single pass: when one holder fires, it adds to specifiedExpressions, which may enable subsequent holders. With the reversed order, a holder like "when $newVersionExists is true, $newVersion is non-null" was evaluated before the holder "when $previousVersionExists is false, $newVersionExists is true" had fired, so $newVersionExists wasn't yet in specifiedExpressions.

The fix makes filterBySpecifiedTypes order-independent by looping until convergence — it keeps iterating as long as new expressions are being resolved, allowing chains of any depth to propagate correctly.

Test

The regression test tests/PHPStan/Analyser/nsrt/bug-14178.php reproduces the exact scenario from the issue: two nullable parameters with boolean tracking variables, compound conditions that eliminate impossible combinations, and a subsequent if block where the type should be narrowed to non-null.

Fixes phpstan/phpstan#14178