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Error Identifier: generics.notSubtype

Every error reported by PHPStan has an error identifier. Here’s a list of all error identifiers. In PHPStan Pro you can see the error identifier next to each error and filter errors by their identifiers.

Code example #

<?php declare(strict_types = 1);

/**
 * @template T
 * @param T $object
 * @return T
 */
function wrap(object $object)
{
    return $object;
}

/** @var int $result */
$result = wrap(new \stdClass());

Why is it reported? #

A type argument provided to a generic type is not a subtype of the corresponding template type’s bound. In the example above, the function wrap declares a template type T without an explicit bound, but the parameter $object has a native object type. Since @template T without a bound defaults to mixed, but the parameter restricts it to object, the template type needs to declare @template T of object to match the native type constraint.

This ensures that generic types are used with compatible type arguments that satisfy the declared constraints.

How to fix it #

Add the appropriate bound to the template type to match the native type of the parameter:

 <?php declare(strict_types = 1);
 
 /**
- * @template T
+ * @template T of object
  * @param T $object
  * @return T
  */
 function wrap(object $object)
 {
     return $object;
 }

This way T is properly constrained to object, matching the native parameter type.

How to ignore this error #

You can use the identifier generics.notSubtype to ignore this error using a comment:

// @phpstan-ignore generics.notSubtype
codeThatProducesTheError();

You can also use only the identifier key to ignore all errors of the same type in your configuration file in the ignoreErrors parameter:

parameters:
	ignoreErrors:
		-
			identifier: generics.notSubtype

Rules that report this error #

• PHPStan\Rules\Classes\LocalTypeAliasesRule [1]
• PHPStan\Rules\Classes\LocalTypeTraitAliasesRule [1]
• PHPStan\Rules\Classes\LocalTypeTraitUseAliasesRule [1]
• PHPStan\Rules\Classes\MethodTagRule [1]
• PHPStan\Rules\Classes\MethodTagTraitRule [1]
• PHPStan\Rules\Classes\MethodTagTraitUseRule [1]
• PHPStan\Rules\Classes\MixinRule [1]
• PHPStan\Rules\Classes\MixinTraitRule [1]
• PHPStan\Rules\Classes\MixinTraitUseRule [1]
• PHPStan\Rules\Classes\PropertyTagRule [1]
• PHPStan\Rules\Classes\PropertyTagTraitRule [1]
• PHPStan\Rules\Classes\PropertyTagTraitUseRule [1]
• PHPStan\Rules\Generics\ClassAncestorsRule [1]
• PHPStan\Rules\Generics\ClassTemplateTypeRule [1]
• PHPStan\Rules\Generics\EnumAncestorsRule [1]
• PHPStan\Rules\Generics\FunctionTemplateTypeRule [1]
• PHPStan\Rules\Generics\InterfaceAncestorsRule [1]
• PHPStan\Rules\Generics\InterfaceTemplateTypeRule [1]
• PHPStan\Rules\Generics\MethodTagTemplateTypeRule [1]
• PHPStan\Rules\Generics\MethodTagTemplateTypeTraitRule [1]
• PHPStan\Rules\Generics\MethodTemplateTypeRule [1]
• PHPStan\Rules\Generics\TraitTemplateTypeRule [1]
• PHPStan\Rules\Generics\UsedTraitsRule [1]
• PHPStan\Rules\PhpDoc\FunctionAssertRule [1]
• PHPStan\Rules\PhpDoc\IncompatibleClassConstantPhpDocTypeRule [1]
• PHPStan\Rules\PhpDoc\IncompatiblePhpDocTypeRule [1]
• PHPStan\Rules\PhpDoc\IncompatiblePropertyHookPhpDocTypeRule [1]
• PHPStan\Rules\PhpDoc\IncompatiblePropertyPhpDocTypeRule [1]
• PHPStan\Rules\PhpDoc\IncompatibleSelfOutTypeRule [1]
• PHPStan\Rules\PhpDoc\InvalidPhpDocVarTagTypeRule [1]
• PHPStan\Rules\PhpDoc\MethodAssertRule [1]

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