Why is any assignable to string

[ocean fable]

Based on my intuition I thought the following

type F = any extends string ? true : never;

would result in never but that's not the case. I thought that for the extends to be true every value of a given type would need to be assignable to the other type 🤔

[knotty shale]

pretty sure any "extends" everything and everything "extends" any

any any value can be assigned to string, any string value can be assigned to any

that's kinda the point of any

maybe you're thinking of unknown

[ocean fable]

Doesnt any contain all values though? So for example numbers wouldnt be assignable to string

or is any just an escape hatch? 🤔

[knotty shale]

any doesn't "contain" anything, it disables typechecking

it isn't typesafe

unknown is the typesafe, uh equivalent i guess

[ocean fable]

ah ok, so my understanding that it is a top type was incorrect. Thanks a lot @knotty shale 🙏

[solid notch]

yup

unknown is the top type, never is the bottom type, any is the escape hatch

[knotty shale]

any is the side type

[solid notch]

lol

[crystal temple]

type T = any extends string ? 1 : 0;
//   ^? - type T = 0 | 1

[solid notch]

any is wild

[knotty shale]

eh i guess that makes sense with the original, since true | never = true

[solid notch]

right

[viscid condor]

any is the quantum type - its sometimes the top type and other times the bottom type

whichever is more permissive

[knotty shale]

so it's a switch

[viscid condor]

type A = keyof any;
type B = keyof unknown;
type C = keyof never;

!ts A B C

[crystal temple]

type A = string | number | symbol /* 1:6 */``````ts
type B = never /* 2:6 */``````ts
type C = string | number | symbol /* 3:6 */```

[viscid condor]

its funny, it just swaps places between unknown and never in different contexts

so in this context its the same as never

in others its more like unknown

[knotty shale]

so like as a function argument, with contravariance, that would be emulating never?

mm that is definitely not the right word

[viscid condor]

another is with assignment, if its on the left hand side its like unknown, but if its on the right hand side its like never

as never is basically the same thing as as any

const a: string = 1 as never

!ts

[crystal temple]

const a: string = 1 as never

[viscid condor]

its probably not formally implemented like this

but the observed behaviour is consistent with it

given that any predates both unknown and never

[knotty shale]

!resolved