Fix #11310: False Positive on Match Arm Comparison with Incremented Bounded Integer

[phpstan-bot]

Summary

When using post-increment ($i++) or post-decrement ($i--) as the condition in a match expression, PHPStan incorrectly evaluated the match arms using the post-incremented type instead of the original value. For example, match ($i++) { 0 => ... } with $i: int<0, max> would report "Match arm comparison between int<1, max> and 0 is always false", even though $i++ evaluates to the original value of $i before incrementing.

The same issue also affected pre-increment (++$i), which was double-incremented — the type was incremented once during expression processing, then enterMatch() would re-evaluate it in the updated scope, effectively incrementing it a second time.

Changes

• Modified MutatingScope::enterMatch() in src/Analyser/MutatingScope.php to accept optional pre-computed condition type and native type parameters
• Modified NodeScopeResolver in src/Analyser/NodeScopeResolver.php to capture both the condition type and native type before processing the condition expression, and pass them to enterMatch()
• Added regression test in tests/PHPStan/Rules/Comparison/data/bug-11310.php covering post-increment, post-decrement, and pre-increment in match conditions
• Added test method testBug11310() in tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php

Root cause

In NodeScopeResolver::processExprNode() for Expr\Match_, the condition type was captured correctly at line 4178 ($condType = $scope->getType($expr->cond)), but then the condition expression was processed (line 4179), which updates the scope with the incremented variable type. When $scope->enterMatch($expr) was called (line 4185), enterMatch() would re-evaluate $this->getType($cond) using the already-updated scope, getting the wrong type.

The fix passes the pre-computed types directly to enterMatch() so it doesn't need to re-derive them from the (now stale) scope.

Test

Added tests/PHPStan/Rules/Comparison/data/bug-11310.php with three test cases:

• $i++ (post-increment) in match — should not report false positive on 0 => 'zero'
• $i-- (post-decrement) in match — should not report false positive on 0 => 'zero'
• ++$i (pre-increment) in match — should correctly report that 0 is always false (since ++$i on int<0, max> gives int<1, max>), but should NOT report 1 as always false

Fixes phpstan/phpstan#11310