Class PHPStan\Type\Generic\TemplateTypeVariance

`final`

Represents the variance of a template type parameter. Variance describes how subtyping of a generic type relates to subtyping of its type arguments. For a class Box<T>: - Invariant (default): Box<Cat> is NOT a subtype of Box<Animal>, even though Cat extends Animal. The type argument must match exactly. Declared with @template T.

Covariant: Box<Cat> IS a subtype of Box<Animal>. Safe when T only appears in "output" positions (return types). Declared with @template-covariant T.
Contravariant: Box<Animal> IS a subtype of Box<Cat>. Safe when T only appears in "input" positions (parameter types). Declared with @template-contravariant T.
Bivariant: The type argument is ignored for subtyping purposes. Rarely used.
Static: Special variance for static return type in template context. Variance composition follows standard rules — e.g. covariant composed with contravariant yields contravariant. This is used when template types appear inside nested generic types.

Located at src/Type/Generic/TemplateTypeVariance.php

Methods
`public static`	`createInvariant(): self` Type argument must match exactly. This is the default for @template T. Type argument must match exactly. This is the default for @template T.	#
`public static`	`createCovariant(): self` Subtyping flows with the type argument: Cat <: Animal ⟹ Box<Cat> <: Box<Animal>. Subtyping flows with the type argument: Cat <: Animal ⟹ Box<Cat> <: Box<Animal>.	#
`public static`	`createContravariant(): self` Subtyping flows against the type argument: Cat <: Animal ⟹ Box<Animal> <: Box<Cat>. Subtyping flows against the type argument: Cat <: Animal ⟹ Box<Animal> <: Box<Cat>.	#
`public static`	`createStatic(): self` Special variance for static return type in template context. Special variance for static return type in template context.	#
`public static`	`createBivariant(): self` Type argument is ignored for subtyping — all types are compatible. Type argument is ignored for subtyping — all types are compatible.	#
`public`	`invariant(): bool`	#
`public`	`covariant(): bool`	#
`public`	`contravariant(): bool`	#
`public`	`static(): bool`	#
`public`	`bivariant(): bool`	#
`public`	`compose(self $other): self`	#
`public`	`isValidVariance(TemplateType $templateType, Type $a, Type $b, bool $strict = false): IsSuperTypeOfResult` By default `mixed` and benevolent unions are compatible with any other type argument in both directions - that is how gradual typing works. With $strict that answer is not given: it makes the relation symmetric (`Foo<mixed>` and `Foo<int>` end up supertypes of each other) and TypeCombinator::union() then discards one of them depending on the order the types come in. In the strict mode invariance is relaxed just enough to keep `Foo<mixed>` a supertype of `Foo<int>` and not the other way around. By default `mixed` and benevolent unions are compatible with any other type argument in both directions - that is how gradual typing works. With $strict that answer is not given: it makes the relation symmetric (`Foo<mixed>` and `Foo<int>` end up supertypes of each other) and TypeCombinator::union() then discards one of them depending on the order the types come in. In the strict mode invariance is relaxed just enough to keep `Foo<mixed>` a supertype of `Foo<int>` and not the other way around.	#
`public`	`equals(self $other): bool`	#
`public`	`validPosition(self $other): bool`	#
`public`	`describe(): string`	#
`public`	`toPhpDocNodeVariance(): GenericTypeNode::VARIANCE_*`	#

Namespaces

Classes

Interfaces

Class PHPStan\Type\Generic\TemplateTypeVariance