Class parameter incorrectly treated as bivariant · Microsoft/TypeScript#56225

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Description

🔎 Search Terms

class parameter generic bivariant constructor typeof extends

🕗 Version & Regression Information

This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.3.0-dev.20231026#code/C4TwDgpgBAggRgZ2AJwIYGNirgGwgYQHsA7JZAV00OQB4BLUrY9aAXigG8BfAPinexkMwKMQgB3KAAoAsACgAkADoVqZAHMEALlEQAbhGQBtALryAlPz4MkqZhHnzQkKAElGdlgHkAZjXQkZJTA1Hys8goBjBRUyFAQAB7AEMQAJgiwiCjC2HhE0cHU9MQ+hlA2TCx8APzlHvZQOmIGyI5y6DioCBkAYoSEnBGpEB1q0HBqOijkDnJcbaPdUAAKyIQhNGBrIfFJKemZQpi5BIHTsfyH2ce4pwWxfBxDI53I0BWeEDrutva+m9tCDx5PM5PIAPTgqBeADWTnA0Bgl1W60IRgARB97OizHJIVACQA9aptfGw+EuABCyMBNGcEEIPigfSBGKxLBxEKhRJJYLxUPJcnpUHwlyRiWSaQy1Nq02gOh8qBwCFm+J5pKhABUABZ0DIIbWEcg4VJQODQRXK2bCgBaNNRu0lBxRG3pjOZ-RqUDljSglpVXIJUGJQA

💻 Code

type AbstractableConstructor<instance = {}> = abstract new (
	...args: never[]
) => instance

type InstanceOf<constructor> =
	constructor extends AbstractableConstructor<infer instance> ? instance : never

class Foo {
	declare bar: true
}

class Proto<proto extends AbstractableConstructor = AbstractableConstructor> {
	declare instance: InstanceOf<proto>
}

// Ok
type A = Proto["instance"]
//   ^? {}

// Ok
type B = Proto<typeof Foo>["instance"]
//   ^? Foo

// Ok
type C = A extends B ? true : false
//   ^? false

// This should be false
type Z = Proto extends Proto<typeof Foo> ? true : false
//   ^? true

🙁 Actual behavior

proto is treated as bivariant with no structural comparison, resulting in Z evaluating to true.

🙂 Expected behavior

proto should be treated as covariant as only its return type is used, or compared structurally, resulting in Z evaluating to false.

Additional information about the issue

No response

Guia do colaborador

Direção de pesquisa: Examine como o TypeScript resolve o parâmetro `typeof Foo` na classe `Proto` dentro do tipo condicional `InstanceOf`. Investigue o cálculo de variância para parâmetros de tipo de classe, especialmente quando o parâmetro é usado apenas na posição de retorno. O problema é que `Proto extends Proto<typeof Foo>` avalia incorretamente como `true` devido ao tratamento bivariante.
Pilha de tecnologia: typescript
Domain: compilers
Tipo Issue: Bug
Difficulty: 4
Tempo estimado: 3-5 dias
Status da atividade: Ativo
Clarity: Claro
Prerequisites: TypeScriptunderstanding of generics and variance
Simpatia para novatos: 25