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Generic type param used as generic type constraint causes variance issues? #33561
Description
TypeScript Version: 3.5.1, 3.6.3, Nightly
Search Terms:
generic type parameter, generic type constraint, variance
Code
declare const x0 : <InT extends boolean|null>(arg : InT) => boolean;
//Expected: Error
//Actual : Error
const x1 : <InT extends string>(arg : InT) => boolean = x0;
type Y<In, Out> = <InT extends In>(arg : InT) => Out;
declare const y0 : Y<boolean|null, boolean>;
//Expected: Error
//Actual : OK
const y1 : Y<string, boolean> = y0;Expected behavior:
y1 = y0 assignment should fail
Actual behavior:
y1 = y0 assignment passes
Playground Link:
Related Issues:
Activity
AnyhowStep commentedon Sep 23, 2019
Seems like the type inference is OK, though,
3.5.1 Playground
jack-williams commentedon Sep 23, 2019
Duplicate of #31006 and fixed by #31029.
AnyhowStep commentedon Sep 23, 2019
It's not in the nightly builds?
[Edit]
Oh, not merged yet.
I guess I'll close this and monitor that PR. Thanks!