Fixed some variance measurements in type aliases of generic functions #54866
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| @@ -223,6 +226,10 @@ immutable.ts(391,22): error TS2430: Interface 'Set<T>' incorrectly extends inter | |||
| export function Stack<T>(): Stack<T>; | |||
| export function Stack<T>(collection: Iterable<T>): Stack<T>; | |||
| export interface Stack<T> extends Collection.Indexed<T> { | |||
| ~~~~~ | |||
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I have a hard time assessing if this is a good change or not, could use some help with that 😅
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This is probably a good change. This used to stack out, using more variance calculations removed the stack out, but I think have been hiding the error with incorrect results.
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I thought this change looked familiar - I'd built this into the suite of changes in #43887 long ago. I do think this is very much still needed, and since it can stand on its' own, we should probably take it (though I am biased and should get someone else to peek at it). There's a bit more that you should handle, like propagating this "erased" type through indexed access operations, similarly to how wildcardType already works, and any other type constructor that wildcards propagate through.
| @@ -223,6 +226,10 @@ immutable.ts(391,22): error TS2430: Interface 'Set<T>' incorrectly extends inter | |||
| export function Stack<T>(): Stack<T>; | |||
| export function Stack<T>(collection: Iterable<T>): Stack<T>; | |||
| export interface Stack<T> extends Collection.Indexed<T> { | |||
| ~~~~~ | |||
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This is probably a good change. This used to stack out, using more variance calculations removed the stack out, but I think have been hiding the error with incorrect results.
Do u know what kind of tests I should use to verify that I'm moving in the right direction? I guess that for the most part I can heavily borrow from #43887 but since you mentioned that was a broader change... I'm not really able to tell quickly which parts are borrowable and which ones are not 😅 |
An experiment on how the variance measurement could be improved when intersections and unions are involved in situations like this.
related to the issue found here, cc @RyanCavanaugh