Fix phpstan/phpstan#12063: Call to function is_callable() with array{...} will always evaluate to true

[phpstan-bot]

Summary

When is_callable() is called with an array like [$object, $methodName] where $methodName is a union type containing both existing and non-existing method names (e.g., 'existingMethod'|'nonExistingMethod'), PHPStan incorrectly reported that the call will always evaluate to true. The fix makes isCallable() return maybe when some method names in the union don't exist on the target class.

Changes

• Modified ConstantArrayType::isCallable() in src/Type/Constant/ConstantArrayType.php to detect when findTypeAndMethodNames() skipped non-existent methods
• Extracted the body of findTypeAndMethodNames() into a private doFindTypeAndMethodNames(bool &$hasNonExistentMethod) helper that tracks whether any method names were skipped
• When non-existent methods are detected, isCallable() ANDs the result with maybe to prevent false yes results

Root cause

ConstantArrayType::findTypeAndMethodNames() skips method names that don't exist on the target class (hasMethod()->no() → continue). This means when checking is_callable([$obj, 'existingMethod'|'nonExistingMethod']), only existingMethod was returned, making isCallable() conclude the array is always callable. The fix preserves the skip behavior (needed for getCallableParametersAcceptors) but lets isCallable() know that some methods were filtered out.

Test

Added tests/PHPStan/Rules/Comparison/data/bug-12063.php with the exact reproducing code from the issue — a class with existingMethod and a loop over a mapping that includes both existingMethod and nonExistingMethod. The test expects no errors (the false positive function.alreadyNarrowedType should not be reported).

Fixes phpstan/phpstan#12063
Fixes phpstan/phpstan#4608

[VincentLanglet]

Do we have to instantiate this variable since we don't use it ?

[phpstan-bot]

Done. Made the $hasNonExistentMethod parameter optional with a default value of false in doFindTypeAndMethodNames(), so findTypeAndMethodNames() no longer needs to instantiate a variable it never uses. All tests and static analysis pass.

[VincentLanglet]

Add non regression for phpstan/phpstan#4608, for this, ensure the three last line of

$c = new class {
	public function abc(): void {}
};

$s = rand(0, 1) ? 'abc' : 'not_abc';

$c->{$s}();
call_user_func([$c, $s]);
[$c, $s]();

report an error

- Call to an undefined method class@anonymous/tmp.php:3::not_abc().
- Parameter #1 $callback of function call_user_func expects callable(): mixed, array{class@anonymous/tmp.php:3, 'abc'|'not_abc'} given.
- Trying to invoke array{class@anonymous/tmp.php:3, 'abc'|'not_abc'} but it might not be a callable.

[phpstan-bot]

The background make phpstan task also completed successfully (exit code 0). Everything is green and pushed.

[VincentLanglet]

You get a failure on PHP 7.4

1) PHPStan\Rules\Functions\CallToFunctionParametersRuleTest::testBug4608
Failed asserting that two strings are identical.
--- Expected
+++ Actual
@@ @@
-'11: Parameter #1 $callback of function call_user_func expects callable(): mixed, array{class@anonymous/tests/PHPStan/Rules/Functions/data/bug-4608-call-user-func.php:5, 'abc'|'not_abc'} given.
+'11: Parameter #1 $function of function call_user_func expects callable(): mixed, array{class@anonymous/tests/PHPStan/Rules/Functions/data/bug-4608-call-user-func.php:5, 'abc'|'not_abc'} given.
 '

The name of the param is depend on the PHP VERSION ID

[phpstan-bot]

Fixed. The call_user_func first parameter is named $function in PHP 7.x but $callback in PHP 8.0+. The test now uses PHP_VERSION_ID to select the correct parameter name, matching the pattern already used elsewhere in that test file.

[VincentLanglet]

Fix

--------------------------------------------------------------------------------
FOUND 1 ERROR AFFECTING 1 LINE
--------------------------------------------------------------------------------
 2825 | ERROR | Variable "$paramName" not allowed in double quoted string; use
      |       | sprintf() instead (Squiz.Strings.DoubleQuoteUsage.ContainsVar)
--------------------------------------------------------------------------------

[phpstan-bot]

make tests also confirmed complete (exit code 0). Both checks passed and the fix is already pushed.