Type variable leak and odd error

[ahejlsberg]

🔎 Search Terms

type variable leak

🕗 Version & Regression Information

This is the behavior in 5.8.3 and nightly build

⏯ Playground Link

https://www.typescriptlang.org/play/?#code/CYUwxgNghgTiAEAzArgOzAFwJYHtXzCgggB4BBAGngCUA+AChwCMArALngG94APD+qBzIBKeAF5aNeAF8qsAOZDhHagChQkWAhTpseeAHcYUAA4kAGgz7xzyrrw7mZ68NDhI0mXPizASAFSsOfzt-AG5VVTA8AGcMeAgQKABrAEZxAiIIeiNTel9hKlTRAHoS+H8ATxMEADdYLCgmRISk5PgoVGB4HGBukBgYHBgo2PjElIAmDMJiHOMTfOBC+HSoGI7UStLyqpr4ephG5oQJ5NUgA

💻 Code

declare function call<A, R>(obj: { x: (a: A) => R }, arg: A): R
declare function wrap<X>(x: X): { x: X }
declare function id<T>(x: T): T;

const leak1 = call(wrap(id), 1) // Type variable leak and odd error
const leak2 = call(wrap(id), 1 as any) // Type variable leak

🙁 Actual behavior

The type of the two variables is A, a leaked type variable.

🙂 Expected behavior

No leaks.

Additional information about the issue

No response