Two way assignability condition with generic params is not working as expected

Bug Report

🔎 Search Terms

assignability, ternary, conditions, generics

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

Playground link with relevant code

💻 Code

type NumberIfExtends<T, U> = T extends U ? U extends T ? number : string : string;
function f<G>() {
  const x: NumberIfExtends<G, G> = 1;
}

🙁 Actual behavior

The value 1 is not assignable to variable x, with the following error: Type 'number' is not assignable to type 'NumberIfExtends<G, G>'.

🙂 Expected behavior

This should be assignable, since the the value passed to both T and U generic params is the same.

Please note the following very similar examples, that works without errors.
This is to show this is a minimal reproduction, and that the different do not justify the error:

type NumberIfExtends<T, U> = T extends U ? U extends T ? number : string : string;
const x: NumberIfExtends<'some type', 'some type'> = 1; // if I pass an explicit type (Not a generic)

type NumberIfExtends<T, U> = T extends U ? number : string; // if I use the condition in only one way. 
function f<G>() {
  const x: NumberIfExtends<G, G> = 1;
}

function f<G>(): void {
  const x: G extends G ? G extends G ? number : string : string = 1; // if I define the type without an alias. This is not always possible if instead of defining a variable I would be passing the value to a function who defines its own type
}

Commencez par le TypeScript Playground lié et la reproduction minimale de NumberIfExtends<G, G>. Suivez la manière dont l'assignabilité des types conditionnels avec des paramètres génériques est vérifiée, en comparant la forme alias aux exemples inline et à sens unique. C'est terminé lorsque l'affectation de 1 au type conditionnel générique réussit sans l'erreur signalée.