type X<G> = any extends G ? 1 : 0;
type Y = X<string>; // 1 | 0 ???
Why is X<string> equal to the union of 1 | 0 instead of just one or zero?
#Can someone help me understand this generic result?
molten loom
acoustic rapids
probably weird effects of any, in short
idk what exactly is going on there but i'm pretty sure it's related to the any
molten loom
What I'm trying to achieve is to check if the provided generic type is any and not other type, but this makes my life harder 🥲
acoustic rapids
any won't work like that
generally you use conflicting conditionals to achieve that, such as T extends never then unknown extends T, or T & 1 extends 0
molten loom
ok, will try this
This solution seems to work for my case:
type X<G> = never extends G ? unknown extends G ? 1 : 0 : 0;
type W = X<any>; // 1
type Y = X<unknown>; // 1
type A = X<never>; // 0
type Z = X<string>; // 0
i mean, that doesn't exactly check for any
never extends G is a tautology
unknown extends G checks for exactly unknown and any
never extends T, T extends unknown, any extends T, and T extends any are all always true
molten loom
oh, thanks for these examples
then I'll use the unknown and any version, it's ok for my use case
!resolved
molten loom
Great image representations
hollow fox
its a good blog post
acoustic rapids
that's sick