Typescript failed to expand type in generic for unknown reason

TypeScript Version: 3.1.3

Search Terms:

Code

type Or<T> = T [
    {
        [K in keyof T]: T[K] extends ((...arg:any[])=>any)?
            never:
            K
    } [keyof T]
]

// F is unknown
type F = Or<[
    string,
    number
]>

// F_ is string|number
type F_ = ([
    string,
    number
])[
    {
        [K in keyof ([
            string,
            number
        ])]: ([
            string,
            number
        ])[K] extends ((...arg:any[])=>any)?
            never:
            K
    } [keyof ([
        string,
        number
    ])]
]

Expected behavior:
I will get the type string|number for both case

Actual behavior:
The generic failed to expand the type and make F as unknown for unknown reason,
while manully inline it in F_ typed as expected

Playground Link:
link
Related Issues:

Commencez par l’exemple TypeScript 3.1.3 Playground lié dans l’issue et reproduisez la différence entre le Or générique et le type F_ inline. Examinez pourquoi Or<[string, number]> devient unknown ; le travail est terminé lorsque le cas générique se résout en string|number comme prévu.