Why is <x> extends infer X ? <y> : never so used?

[millsp]

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The whole codebase is full of <x> extends infer X ? <y>: never

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#extends #infer #lots #used

[millsp]

I use this syntax to defer the evaluation of a type... Otherwise TS evaluates all the types in their full depth. This causes performance issues and is irrelevant because we only want to compute when we've received the type parameters. As a result, the ts-toolbelt types load fast.

But it is not the only use case. Like I said above, TS can complain that a type is too deep to compute, then you can force it to compute step by step. So I especially use this on recursive types (which are much deeper because they're recursive).

[ekilah]

Can you add an example of real code from this project that does this to this wiki entry? It's hard to understand if/how x and X are related in your pseudocode <x> extends infer X ? <y>: never (or if the x's are even relevant, which I think they aren't)

[millsp]

You can check this example out