Typescript 为什么上下文类型在`fn｜curred(Fn)`的联合中不起作用

为什么这两种类型的联合不在函数内部提供参数提示？

(ts playground)

type Valish = (value: string) => boolean
type CurryValish = (...args: number[]) => Valish

const check = {
  vin: (value) => true,            // ✗ any, should be string
  cin: (curry) => (value) => true, // ✗ any any, should ne number string
} satisfies {
  [key: string]: 
    | Valish
    | CurryValish
}

const checkValish = {
  vin: (value) => true,            // 🗸 string => boolean
} satisfies { [key: string]: Valish }

const checkCurry = {
  cin: (curry) => (value) => true, // 🗸 number => string => boolean
} satisfies { [key: string]: CurryValish }

它似乎足够好地理解上下文以提供大量信息，甚至在CurryValish类型的内部也是如此.那么，当替换为有效类型时，它为什么不提供参数类型呢？

const x: Valish | CurryValish = (a) => "hi"         
// Type 'string' is not assignable to type 'boolean | Valish'.(2322)

const y: Valish | CurryValish = (b) => (a) => "hi"
// Type '(a: any) => string' is not assignable to type 'boolean | Valish'.
//   Type '(a: any) => string' is not assignable to type 'Valish'.
//     Type 'string' is not assignable to type 'boolean'.