mapped typed issue

[fiery sinew]

piscopancer#0

Playground Link

Preview:```ts
type Ltx = {
inventories: string | string[]
boosts: string
}

type DltxEntries<O extends object> = Partial<
{
[K in keyof O]: (O[K] extends any[]
? {
[_ in K | ${"<" | ">"}${K & string}]: any
}
: {}) & {
[_ in K | !${K & string}]: undefined
} & {
[_ in K]: any
}
}[keyof O]

const test: DltxEntries<Ltx> = {
// no < and > for inventories
}```

[elder silo]

So i have this type and I expected to have < and > for a type that extends an array, it can also be a union with array as one of possible types - have < and > as well

so whenever array appears, in a union or as is, < and > should be enabled

change inventories: string | string[] to inventories: string[] and you will see the type of test variable that I expected

[vernal sail]

add an infer clause to distribute

O[K] extends infer U ? U extends any[] ? ...

[elder silo]

this worked out and this is crazy. Can I ask why it worked? I used infer in several cases already but I can't realize what use it has here

!resolved

[vernal sail]

https://www.typescriptlang.org/docs/handbook/2/conditional-types.html#distributive-conditional-types