[westonruter]

Closes phpstan/phpstan#15734

With rememberPossiblyImpureFunctionValues: false, the return value of a method that only maybe has side effects is no longer remembered, but what was narrowed about the properties of the object it was called on still is. This makes a call to such a method also invalidate those properties, as a call to a method that has side effects already does:

• A method call ($obj->foo(), $obj?->foo()) invalidates $obj.
• A static call within the declaring class (self::, static::, parent::) invalidates $this, or only the static properties when the method is static.

A method known to have no side effects, such as one marked @phpstan-pure, still leaves everything narrowed. So does a method declared in a built-in class, as it already does for the invalidation of volatile expressions after the call. With the option on, which is the default, nothing changes.

The change adds one condition to the invalidation in MethodCallHandler and StaticCallHandler:

|| (
	!$this->rememberPossiblyImpureFunctionValues
	&& !$hasSideEffects->no()
	&& !$methodReflection->getDeclaringClass()->isBuiltin()
)

The turbo extension's MethodCallHandler.cpp and StaticCallHandler.cpp get the same condition, reading the rememberPossiblyImpureFunctionValues slot they already have.

Scope

Only the object a method is called on is invalidated, mirroring what already happens for a method that has side effects. These keep their narrowing after a possibly impure call:

• Objects passed as arguments, as in $walker->visit($node) followed by a check of $node->state.
• Static properties of a class after a static call made from outside its hierarchy, since StaticCallHandler only invalidates when the scope's class is the declaring class.
• Global state after a possibly impure function call, which would be a change to FuncCallHandler.

Aliasing is not considered either: after $other->advance(), the properties of $this stay narrowed, though $other may be $this.

Performance

With the option off, nearly every non-void $this->method() call not known to be pure now invalidates $this. Invalidating $this cannot use the key prefilter in ScopeOps, so each such call scans all narrowed expressions and conditional expressions. The benchmarks all run with the option on, so they do not measure this. hasSideEffects(), which is not memoized, is read once for the whole condition.

Tests

• do-not-remember-possibly-impure-function-values-properties.php, added to DoNotRememberPossiblyImpureFunctionValuesTest, covers:
  • calls on $this, on another object, and through ?->, self::, static::, and parent::;
  • a static call from a static method;
  • that a pure method, a built-in method, instance properties after a static call, and local variables stay narrowed;
  • that a property asserted by a method's @phpstan-assert-if-true stays narrowed.
• nsrt/remember-possibly-impure-function-values-properties.php is the same fixture under the default configuration, where every narrowing is kept.
• StrictComparisonOfDifferentTypesDoNotRememberPossiblyImpureValuesRuleTest runs the rule with the option off on bug-15734.php, the reproducer from the issue, and expects no errors.

Without the change, the expectations it affects fail, and the reproducer reports both comparisons from the issue. With the PHP change reverted and only the native one in place, the tests pass with the extension loaded, so both implementations are covered. Analysing the fixtures with the option off gives identical output with and without the extension.

The full test suite passes with the turbo extension loaded, as do side-by-side.php, signature-parity.php, and smoke.php.

Open questions

• This reuses rememberPossiblyImpureFunctionValues, whose name and documentation refer to return values. Projects that already set it to false get new errors, as the PMMP integration test shows (see the comment below). It could instead be put behind bleeding edge or given its own option.
• FuncCallHandler could do the same for global state after a possibly impure function call. That is not part of this PR.

🤖 Generated with Claude Code using Claude Opus 5.5 (medium effort)

[westonruter]

_{🤖 Comment by Claude Opus 5.5 (medium effort)}

The PMMP Tests failure is caused by this change: PocketMine-MP sets rememberPossiblyImpureFunctionValues: false, so it is the one integration project where the new behavior applies, and it now gets 16 new errors where a property is narrowed, a method not known to be pure is called, and the property is used again. The reports are what the change intends, but since projects that already opted in get new errors, this may be better placed behind bleedingEdge or a separate option; that can be done here if preferred.

Details

Job: https://github.com/phpstan/phpstan-src/actions/runs/43651082812/job/132623385937 (PocketMine-MP 5.44.3, whose phpstan.neon.dist has rememberPossiblyImpureFunctionValues: false #risky to remember these, better for performance to avoid repeated calls anyway).

Two representative cases:

• Block::getCollisionBoxes() assigns $this->collisionBoxes, calls $this->getModelPositionOffset(), then iterates over and returns the property, which is now list<AxisAlignedBB>|null.
• Main::startNextTest() checks $this->currentTest !== null, then calls $this->getLogger() before using $this->currentTest.

All 16 errors:

File	Line	Error
src/Server.php	1932	Cannot call method readLine() on ConsoleReaderChildProcessDaemon|null.
src/block/Block.php	922	Argument of an invalid type list<AxisAlignedBB>|null supplied for foreach, only iterables are supported.
src/block/Block.php	927	Method Block::getCollisionBoxes() should return list<AxisAlignedBB> but returns list<AxisAlignedBB>|null.
src/block/FlowerPot.php	104	Cannot call method asItem() on Block|null.
src/block/tile/Chest.php	100	Cannot call method removeAllViewers() on DoubleChestInventory|null.
src/entity/Entity.php	1325	Method Entity::getBlocksAroundWithEntityInsideActions() should return array<Block> but returns array<Block>|null.
src/entity/object/ExperienceOrb.php	165	Parameter #1 $entityId of method World::getEntity() expects int, int|null given.
src/entity/object/FallingBlock.php	180	Call to an undefined method Block::onHitGround().
src/entity/projectile/Projectile.php	147	Parameter #1 $pos of method World::isInLoadedTerrain() expects Vector3, Vector3|null given.
src/entity/projectile/Projectile.php	148	Parameter #1 $pos of method World::getBlock() expects Vector3, Vector3|null given.
src/player/Player.php	1181	Parameter #1 $pos of method World::getBlock() expects Vector3, Vector3|null given.
src/player/Player.php	1184	Parameter #1 $pos of method World::setBlock() expects Vector3, Vector3|null given.
tests/plugins/TesterPlugin/src/Main.php	92	Cannot call method getName() on Test|null.
tests/plugins/TesterPlugin/src/Main.php	93	Cannot call method start() on Test|null.
tools/generate-bedrock-data-from-packets.php	492	Cannot call method fromIntId() on ItemTypeDictionary|null.
tools/generate-bedrock-data-from-packets.php	494	Cannot call method fromIntId() on ItemTypeDictionary|null.

Namespaces are shortened. Each could be addressed in PocketMine-MP by marking the intervening method @phpstan-pure or by reading the property into a local variable first.

The other failures are not caused by this PR:

• The doctrine/orm, symfony/symfony, phpstan-laravel, phpstan-dba, espocrm, invoiceninja, and openemr integration jobs fail the same way on an unrelated PR (update-tally-1.0, run 43649509349). The doctrine/orm errors, for example, are all Doctrine DBAL 4.6 deprecations.
• Backward Compatibility fails on 2.3.x itself since a9434a5.
• The two slower benchmarks, UnionTypeBench::benchDescribeIntersections (memory +8.3 %) and FileCacheStorageBench::benchSave (instructions +5.3 %), do not run the changed code. Benchmarks also failed on the preceding 2.3.x push.

[phpstan-bot]

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