Contravariant inference gets picked when a a better covariant candidate exists #57908

🔎 Search Terms

covariant covariance contravariant contravariance inference candidates subtyping assignable subtype

🕗 Version & Regression Information

• This is the behavior in every version I tried

⏯ Playground Link

https://www.typescriptlang.org/play?ts=5.5.0-dev.20240322#code/C4TwDgpgBAShCOBXCBnYAeAKgZQMYAsIBbAQyggA9gIA7AExSj0NID4oBeKAbwCgooSCACcQALig4CxEgG0ARENHyAugG5eAXw29QkJtNKceg5KID8ExDQDWNAPYB3GmqgAje3RCWo1u05oobV5eOghcABsSYWgAM2tcYABLe0Dhe0RqLGYZcipaBgMWElYACns3ACsJPgEwGIlSkgkpYoBKTnYAN3skug0BFENmyRzSAah8EnoIiEaY+Ak4ITRs4dYOjm7e-q02iR6+nVxUtCgukgi+kmpjUoB9GtMRbytbB2dXDy8fPw-AzSbdjcYK8dKZCClWpQepzc6Xa7UAA0-CgQ2KNVRAiU4ig8nkKIEmkJk2mdFm8wQQJ4WKgJxoZ2oaAkaGESRoAHNjAsAHQ4ibEvY6ShgezCYA8YJAA

💻 Code

type Request<TSchema extends Schema> = {
  query: TSchema["query"];
};

type Schema = { query?: unknown; body?: unknown };

declare function route<TSchema extends Schema>(obj: {
  pre: (a: TSchema) => void;
  schema: TSchema;
  handle: (req: Request<TSchema>) => void;
}): void;

const validate = (_: { query?: unknown; body?: unknown }) => {};

route({
  pre: validate,
  schema: {
    query: "",
  },
  handle: (req) => {
    const test: string = req.query;
  },
});

export {};

🙁 Actual behavior

assignment to test fails because { query?: unknown; body?: unknown; } was inferred there

🙂 Expected behavior

I'd expect { query: string } to be inferred here and the assignment to test to succeed

Additional information about the issue

This is a reduced version of this failure.