Fix phpstan/phpstan#12597: 'Variable might not be undefined' in if-statement after in_array check.

[phpstan-bot]

Summary

Fixes phpstan/phpstan#12597

When in_array($type, [self::TYPE_1, self::TYPE_2], true) narrows $type to a union type like 1|2, and a variable $message is assigned inside that block, PHPStan creates a conditional expression: "when $type is 1|2, $message is defined." However, a subsequent if ($type === self::TYPE_1) narrows $type to just 1, and the conditional expression didn't fire because filterBySpecifiedTypes used exact type matching via equals() — 1 does not equal 1|2.

Changes

• src/Analyser/MutatingScope.php: Modified filterBySpecifiedTypes to allow conditional expression guards to match when the specified type is a strict subtype of a finite union guard type. The subtype matching is carefully restricted to prevent regressions:

  • Only activates for guard types with >1 finite types (unions of constants/literals)
  • Requires YES certainty on both the guard, specified expression, and the conditional's type holder
  • The YES certainty requirement on the type holder prevents matching stale "undefined" conditionals from earlier scope merges (prevents regression in bug-14117)
  • Subtype matches don't cascade into specifiedExpressions to prevent mutual conditional loops from corrupting type information (prevents regression in dynamic-access test)

• tests/PHPStan/Rules/Variables/data/bug-12597.php: New regression test data file

• tests/PHPStan/Rules/Variables/DefinedVariableRuleTest.php: Added testBug12597()

• tests/PHPStan/Analyser/nsrt/bug-5051.php: Updated test expectations for improved type inference — several bool assertions are now correctly narrowed to false when the guard variable is narrowed to a specific constant value

Test plan

• New regression test testBug12597 passes (no false positive about undefined variable)
• testDynamicAccess passes (no regression in conditional variable tracking)
• testBug14117 passes (no regression with stale conditionals)
• bug-5051 type inference test updated and passes
• Full test suite passes (11722 tests, 0 failures)
• PHPStan self-analysis passes (make phpstan)
• Coding standards pass (make cs-fix)

[staabm]

Add regression rule-tests for

• phpstan/phpstan#13591
• phpstan/phpstan#10422
• phpstan/phpstan#10055

[phpstan-bot]

Tests also confirmed passing from the background run. Everything is green and already pushed.

[VincentLanglet]

Why is it limited to finites types ? Cant we have a conditional expression "if $x is int|string then $message is defined" and later the need to know that $messgae is defined when $x is int ?

[phpstan-bot]

Done. Here's a summary of the changes made to address VincentLanglet's review:

Problem: The subtype matching in filterBySpecifiedTypes was restricted to guard types with count(getFiniteTypes()) > 1, which excluded non-finite union types like int|string.

Fix: Replaced the finite types restriction with !$guardType instanceof MixedType. This allows:

• Finite unions like 1|2 (already worked)
• Non-finite unions like int|string (now works too)
• But excludes mixed-based types like mixed~false, mixed~null etc. which would cause incorrect *NEVER* type collapses when matched against concrete types

Test: Added testBug12597NonFinite with a test case using is_int($type) || is_string($type) to verify the non-finite union guard type scenario works correctly.

Verification: All 11726 tests pass, make phpstan reports no errors.

[staabm]

Add regression test for

• phpstan/phpstan#4090
• phpstan/phpstan#11218

[phpstan-bot]

Done. Added and pushed two regression test files:

• tests/PHPStan/Analyser/nsrt/bug-4090.php — Tests that after in_array($value, $items, true), the array is correctly narrowed to non-empty-array<string> and current() returns string (not string|false).

• tests/PHPStan/Analyser/nsrt/bug-11218.php — Tests that a variable assigned inside a for loop is correctly typed after the loop.

All 11728 tests pass and make phpstan reports no errors.

[VincentLanglet]

Add regression test for

• phpstan/phpstan#4090
• phpstan/phpstan#11218

I think the regression test added for 4090 is not correct ; might need to be updated manually @staabm