Fix #5610: Match integer comparision

[phpstan-bot]

Summary

When using match(true) with complementary integer comparisons like $bar < $baz and $bar >= $baz, PHPStan incorrectly reported "Match expression does not handle remaining value: true" even though the two arms cover all possible cases.

Changes

• Added resolveComplementaryComparison() method to src/Analyser/MutatingScope.php that checks stored expression types for complementary comparisons
• Modified the comparison resolution logic in MutatingScope::resolveType() to use this method before computing comparison results from operand types
• Added regression test in tests/PHPStan/Rules/Comparison/data/bug-5610.php covering all four complement pairs (</>=, >/<=, <=/>, >=/<)
• Added test method testBug5610() in tests/PHPStan/Rules/Comparison/MatchExpressionRuleTest.php

Root cause

When match(true) processes arms sequentially, after the first arm ($bar < $baz), the scope stores $bar < $baz → false via filterByFalseyValue. However, when resolving the second arm's condition $bar >= $baz, MutatingScope::resolveType() computed the result purely from the operand types (int >= int → maybe → bool), without checking if the complementary expression $bar < $baz already had a stored constant boolean type. Since getType($bar >= $baz) returned bool instead of true, the match was not detected as exhaustive.

The fix adds a complement check: when resolving $a >= $b, it looks up $a < $b in the scope's stored expression types. If the complement is stored as false, the comparison returns true (and vice versa). This allows the match arm processing to correctly identify the second arm as always-true, making the match exhaustive.

Test

The regression test covers four functions, each with a match(true) using a different pair of complementary comparisons (</>=, >/<=, <=/>, >=/<). All are expected to produce no errors (empty expected errors array).

Fixes phpstan/phpstan#5610

[VincentLanglet]

This need more tests, like

• does the second case is reported as always true (and people should use default)
• how is handled:
  • https://phpstan.org/r/fff8ae39-1f5a-4a64-8bfc-ccc11252cb29
  • https://phpstan.org/r/99e09d8c-228b-46bc-be31-2cd968d10fde

[VincentLanglet]

I tried and this is too specific, more case should be handled
https://phpstan.org/r/9b3cc36b-6df2-4db3-83b3-cadf8850c6b8