Anything new since : Is it possible to pass generic type as generic parameter? ?
My specific problem :
This work fine
type isArrStr<T extends readonly string[] > = T extends readonly["str"] ? true :false ; //dummy
type _retAny<T> = any
//***************
type wrapper<T> = any extends _retAny<isArrStr<infer I>> ? T extends I ? isArrStr<T> : never :never
//********
let myVar:wrapper<readonly["str"]> //ok , return true
let myVar_1:wrapper<readonly["ll"]> //ok , return false
let myVar_2:wrapper<string> // ok , return never
But this doesn't
type wrapper<F,T> = any extends _retAny<F<infer I>> ? T extends I ? F<T> : never :never //error : Type 'F' is not generic
//********
let myVar:wrapper<isArrStr,readonly["str"]> //error : Generic type 'isArrStr' requires 1 type argument
//let myVar_1:wrapper<readonly["ll"]>
//let myVar_2:wrapper<isArrStr,string>
Do you know something to overcome this difficulty ? Thanks for your help have nice day
I'm trying to reproduce HighOrderFunction behavior with type
No, it's still not possible to pass a generic to a generic type parameter plainly, however, it's allowed to pass one if it's constrained. I think, this approach might work for you -
type isArrStr<T> = T extends readonly ["str"] ? true : false; //dummy
type _retAny<T> = any;
type Args<M extends Fn> = M["args"];
type Fn<Args = unknown, Return = unknown> = {
args: Args;
return: Return;
}
type Apply<F extends Fn, U extends Args<F>> = (F & { args: U })["return"];
interface IsArrayOfStr extends Fn {
return: isArrStr<Args<this>>
}
type Result = Apply<IsArrayOfStr, readonly ["str"]>; // true
type Result1 = Apply<IsArrayOfStr, readonly ["11"]>; // false
type Result3 = Apply<IsArrayOfStr, string>; // false
Note that an interface is used to declare the function because the extension of types is limited and instead, an intersection is done for types. Here's a link to the playground.