Respect @phpstan-all-methods-impure, @phpstan-all-methods-pure, and method-level purity annotations on built-in classes

[phpstan-bot]

Summary

When creating method reflections for built-in PHP classes (like Memcached), PhpClassReflectionExtension::createMethod() takes a special path for classes that are built-in or enums and have method signatures in the signature map. This path determined hasSideEffects solely from the signature map metadata, completely ignoring PHPDoc purity annotations (@phpstan-all-methods-impure, @phpstan-all-methods-pure, @phpstan-pure, @phpstan-impure) from stubs.

This meant that adding a stub like:

/** @phpstan-all-methods-impure */
class Memcached {}

had no effect on built-in classes whose methods exist in the signature map, causing false positives when PHPStan cached/narrowed method return values across calls.

Changes

• Added purity annotation checks in the built-in class path of PhpClassReflectionExtension::createMethod() (src/Reflection/Php/PhpClassReflectionExtension.php):
  1. Method-level @phpstan-pure/@phpstan-impure from $currentResolvedPhpDoc->isPure()
  2. Class-level @phpstan-all-methods-pure/@phpstan-all-methods-impure from $declaringClass->getResolvedPhpDoc()
  3. Falls back to signature map metadata / TrinaryLogic::createMaybe() as before
• Initialized $currentResolvedPhpDoc before the method signature loop to fix an undefined variable warning

Root cause

The built-in class path in createMethod() (guarded by $declaringClass->isBuiltin() || $declaringClass->isEnum()) only consulted $this->signatureMapProvider->hasMethodMetadata() for side-effect information. The userland path (createUserlandMethodReflection()) already had the correct logic at lines 908-932 checking both method-level and class-level purity annotations. The fix replicates this pattern in the built-in path.

Test

• tests/PHPStan/Rules/Comparison/Bug14534Test.php: Regression test for the reported bug — @phpstan-all-methods-impure on Memcached via stub, verifying no false notIdentical.alwaysFalse error on getResultCode() in a do-while loop
• tests/PHPStan/Rules/Pure/Bug14534AllPureBuiltinTest.php: Analogous test for @phpstan-all-methods-pure on a built-in class — verifying a pure function can call methods without "Possibly impure call" errors
• tests/PHPStan/Rules/Comparison/Bug14534MethodImpureTest.php: Test for method-level @phpstan-impure on a specific built-in method via stub

All three tests fail without the fix and pass with it.

Fixes phpstan/phpstan#14534

[ondrejmirtes]

Personally I think the tests should put the annotations above some non-sensical class we'll never do it for everyone, like SplFileObject or something.

Once we register a stub file for Memcached for everyone, all the tests lose their meaning.

[VincentLanglet]

I took the fix and the tests (with SplFileStorage) in #5536