Use declared property type instead of scope-narrowed type when inferring generic `new` expression types by phpstan-bot · Pull Request #5467 · phpstan/phpstan-src

phpstan-bot · 2026-04-14T23:18:54Z

Summary

When a nullable generic property (e.g. ?WeakMap $map with @var WeakMap<object, string>|null) was assigned new WeakMap() inside a null-check guard (if ($x === null)), PHPStan incorrectly reported property.unusedType saying the WeakMap<object, string> type was never assigned. This was a false positive introduced in the commit that added static property support to NewAssignedToPropertyVisitor.

Changes

Modified src/Analyser/ExprHandler/NewHandler.php:
- Injected PropertyReflectionFinder to resolve property reflections from AST nodes
- Replaced $scope->getType($assignedToProperty) with $foundProperty->getWritableType() to use the declared property type instead of the scope-narrowed type
Added regression tests:
- tests/PHPStan/Rules/TooWideTypehints/data/bug-11844.php — rule test covering static properties, instance properties, and SplObjectStorage
- tests/PHPStan/Rules/TooWideTypehints/TooWidePropertyTypeRuleTest.php — test method testBug11844
- tests/PHPStan/Analyser/nsrt/bug-11844.php — type inference test verifying correct types after assignment

Root cause

NewHandler::exactInstantiation() infers template types for new GenericClass() from the declared type of the property being assigned to. It used $scope->getType($assignedToProperty) to get this type, but inside a scope where the property has been narrowed (e.g. after if (self::$map === null)), getType() returns the narrowed type (null). After TypeCombinator::removeNull(), this becomes never, causing the TooWideTypeCheck to conclude the generic type was never assigned.

The fix uses PropertyReflectionFinder::findPropertyReflectionFromNode() to get the property's declared writable type, which reflects the PHPDoc/native type annotation and is not affected by scope narrowing.

Test

Rule test: testBug11844 in TooWidePropertyTypeRuleTest verifies no false positive property.unusedType errors for nullable WeakMap and SplObjectStorage properties (both static and instance)
NSRT test: bug-11844.php verifies new WeakMap() is correctly inferred as WeakMap<object, string> when assigned to a property typed WeakMap<object, string>|null
Verified existing tests for the original PR Fix infer new templated type from initial assign into static property #3364 (bug-3777, bug-10686) still pass

Fixes phpstan/phpstan#11844

VincentLanglet

What about a property \WeakMap|null|false
with a code

if ($this->instanceMap !== false) {
     if ($this->instanceMap === null) {
			$this->instanceMap = new \WeakMap();
			assertType('WeakMap<object, string>', $this->instanceMap);
		}
}

VincentLanglet

Add test with a property

@var \WeakMap<T, U>|null

to be sure the TypeCombinator::intersect call is not loosing generic type with template types.

phpstan-bot · 2026-04-15T09:26:53Z

Done. I've addressed the review by adding test cases with template property types (@var \WeakMap<T, U>|null) to verify that TypeCombinator::intersect() preserves generic type information when template types are involved:

Rule test (tests/PHPStan/Rules/TooWideTypehints/data/bug-11844.php): Added TemplatePropertyCase and StaticTemplatePropertyCase classes with @template T of object and @template U class-level templates and @var \WeakMap<T, U>|null properties — verifies no false positive property.unusedType errors.
NSRT test (tests/PHPStan/Analyser/nsrt/bug-11844.php): Added Baz class with the same template setup, with assertType calls confirming new \WeakMap() is correctly inferred as WeakMap<T of object (class ..., argument), U (class ..., argument)> — the template types are preserved through the intersect.

Both make tests (11857 tests, 79365 assertions) and make phpstan pass cleanly.

VincentLanglet

Merge the nsrt type and the TooWideTypehints/data file into a single one used for both nsrt and TooWidePropertyTypeRule test

phpstan-bot · 2026-04-15T09:38:10Z

Done. I merged the two test files into a single tests/PHPStan/Rules/TooWideTypehints/data/bug-11844.php that serves both purposes:

TooWidePropertyTypeRule test - the file is analysed by TooWidePropertyTypeRuleTest::testBug11844() expecting no errors (unchanged)
NSRT test - added assertType() calls inline and registered the file via yield in NodeScopeResolverTest::findTestFiles()

The standalone tests/PHPStan/Analyser/nsrt/bug-11844.php was deleted. All 11857 tests pass and make phpstan reports no errors.

phpstan-bot · 2026-04-15T10:55:22Z

I processed this review but have nothing to report.

staabm · 2026-04-15T19:15:35Z

@@ -0,0 +1,152 @@
+<?php // lint >= 8.0


move this file into tests/PHPStan/Analyser/nsrt and adjust paths to point to the moved path

Done. Moved tests/PHPStan/Rules/TooWideTypehints/data/bug-11844.php to tests/PHPStan/Analyser/nsrt/bug-11844.php as requested by staabm:

The file is now in the nsrt/ directory where it's auto-discovered by NodeScopeResolverTest, so the explicit yield was removed to avoid a duplicate key error

Updated the path in TooWidePropertyTypeRuleTest::testBug11844() to reference the new location

All 11857 tests pass and make phpstan reports no errors

staabm · 2026-04-15T19:43:57Z

-					$nonFinalObjectType = $isStatic ? new StaticType($nonFinalClassReflection) : new ObjectType($resolvedClassName, classReflection: $nonFinalClassReflection);
-					if ($nonFinalObjectType->isSuperTypeOf($propertyType)->yes()) {
-						return $propertyType;
+					$foundProperty = $this->propertyReflectionFinder->findPropertyReflectionFromNode($assignedToProperty, $scope);


why is this fix required for WeakMap but not for other generic objects?

Pushed. To answer staabm's question:

The fix is not WeakMap-specific — it's needed for any generic class whose constructor doesn't reference its template types. The code path at line 420 is entered when count($classTemplateTypes) === count($originalClassTemplateTypes), which means the ConstructorClassTemplateTraverser found no template types consumed by constructor parameters. This is the case for:

WeakMap (empty constructor, but has TKey/TValue templates)

SplObjectStorage (same pattern)

Any custom generic class with a no-arg constructor

For generic classes whose constructors do reference template types (e.g. new GenericContainer($value) where $value: T), the template types are resolved from the constructor arguments instead, so this code path is never reached — and the bug doesn't apply.

I added test cases with a custom CustomGenericCache<TKey, TValue> class (with an explicit no-arg constructor) to demonstrate the fix is general. Both instance and static property variants are tested. All 11857 tests pass and make phpstan reports no errors.

…ing generic `new` expression types - In `NewHandler::exactInstantiation()`, when `new GenericClass()` is assigned to a property and the constructor cannot resolve template types, the code infers template types from the property's declared type - Previously used `$scope->getType($assignedToProperty)` which returns the scope-narrowed type — inside `if ($x === null)`, this returns `null`, and after `removeNull` becomes `never`, causing incorrect type inference - Now uses `PropertyReflectionFinder::findPropertyReflectionFromNode()` to get the property's declared writable type, which is not affected by scope narrowing - Affects both static and instance properties with nullable generic types like `WeakMap<object, string>|null` and `SplObjectStorage<object, string>|null`

…y union When the property type is a union like `WeakMap<object,string>|null|false`, `TypeCombinator::removeNull()` only strips `null`, leaving `WeakMap<object,string>|false`. The subsequent `isSuperTypeOf()` check then fails because `false` is not a subtype of `WeakMap`. Using `TypeCombinator::intersect()` with the class type properly extracts only the matching part of the union (e.g. `WeakMap<object,string>`), handling any combination of non-object types in the property's declared type. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…intersect() preserves generics Adds test coverage for properties typed with class-level template parameters (e.g. `@var \WeakMap<T, U>|null`) to ensure the intersect call in NewHandler does not lose generic type information when template types are involved. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

…a single shared file Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The result of TypeCombinator::intersect($writableType, $nonFinalObjectType) is by definition a subtype of $nonFinalObjectType, so the isSuperTypeOf check is always true when the result is not NeverType. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The file is auto-discovered in the nsrt/ directory by NodeScopeResolverTest, so the explicit yield was also removed to avoid duplicate key errors. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

The fix applies to any generic class whose constructor does not reference its template types (e.g. WeakMap, SplObjectStorage, or custom classes with no-arg constructors). Added CustomGenericCache test cases to prove this. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

VincentLanglet reviewed Apr 15, 2026

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VincentLanglet approved these changes Apr 15, 2026

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VincentLanglet reviewed Apr 15, 2026

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Comment thread src/Analyser/ExprHandler/NewHandler.php Outdated

VincentLanglet reviewed Apr 15, 2026

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Comment thread src/Analyser/ExprHandler/NewHandler.php Outdated

VincentLanglet requested a review from staabm April 15, 2026 15:17

VincentLanglet self-assigned this Apr 15, 2026

staabm reviewed Apr 15, 2026

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staabm approved these changes Apr 15, 2026

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github-actions bot and others added 8 commits April 15, 2026 21:55

Merge NSRT and TooWidePropertyTypeRule test files for bug-11844 into …

cba17ba

…a single shared file Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Remove redundant parentheses around instanceof check

b642c04

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Move bug-11844 test file to tests/PHPStan/Analyser/nsrt/ directory

8439cfe

The file is auto-discovered in the nsrt/ directory by NodeScopeResolverTest, so the explicit yield was also removed to avoid duplicate key errors. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

staabm force-pushed the create-pull-request/patch-uu4m0vb branch from 67382a8 to 9051e36 Compare April 15, 2026 19:55

staabm merged commit 5ec9767 into phpstan:2.1.x Apr 16, 2026
652 of 655 checks passed

staabm deleted the create-pull-request/patch-uu4m0vb branch April 16, 2026 05:25

phpstan-bot mentioned this pull request Apr 16, 2026

Invalid property.unusedType report for nullable WeakMap property (broken since 1.12.4) phpstan/phpstan#11844

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Use declared property type instead of scope-narrowed type when inferring generic `new` expression types#5467

Use declared property type instead of scope-narrowed type when inferring generic `new` expression types#5467
staabm merged 8 commits intophpstan:2.1.xfrom
phpstan-bot:create-pull-request/patch-uu4m0vb

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phpstan-bot commented Apr 14, 2026

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