Check if Array is type T[] or [<some information>]

[white junco]

nop#2745

Playground Link

Preview:```ts
type a1 = unknown[]
type a2 = number[]
type t1 = [number, ...unknown[]]
type t2 = [number, string, ...unknown[]]
type t3 = [number, string, boolean, ...unknown[]]

// Both have length number, but how would I differentiate?```

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[quartz swallow]

@terse abyss tuples extend [infer First, ...infer Rest], arrays shouldnt

well

tuples that dont start with a spread element

you could also try T[number] extends T[0]

[terse abyss]

hm

[terse abyss]

thats too dangerous since T[0] can be unknown

and the elements following it can be not unknown

[quartz swallow]

IsEqual then

[terse abyss]

oh

[quartz swallow]

!:isequal

dang

not a thing

[terse abyss]

yeah that might work

what do you use for isEqual

i use the one from tsafe

[quartz swallow]

search history here

[terse abyss]

type IsMutuallyAssignable<T, S> = [T, S] extends [S, T] ? true : false;
type IsEqual<X, Y> = (<T>() => T extends X ? true : false) extends (<T>() => T extends Y ? true : false) ? true : false

class A { private a?: string }
class B { private a?: string }

type X = IsEqual<A, B>
// ^? - type X = false
type Y = IsMutuallyAssignable<A, B>
// ^? - type Y = false

is it this one

or

!:is-equal

[white junco]

T6#2591

`!t6:is-equal`:

type IsEqual<X, Y> = (<T>() => T extends X ? true : false) extends (<T>() => T extends Y ? true : false) ? true : false

[quartz swallow]

yea

ah, has a dash

[terse abyss]

I kinda help improve the docs experience

is TypeScript bot os

ight, it works good enough

type isTuple<T extends unknown[]> = IsEqual<T[0][], T>;

!close

thanks @quartz swallow