Typescript WTF Moments 8: Type Level Equality Not Working With Intersection
Acid Coder
Posted on September 22, 2022
export type IsSame<T, U> = (<G>() => G extends T ? 1 : 2) extends <
G
>() => G extends U ? 1 : 2
? true
: false
type A = IsSame<{a:1, b:2},{a:1, b:2}> // true
// ^?
type B = IsSame<{ a:1, b:2 },{ a:1 } & { b:2 }> // false
// ^?
Background: Type Level Equality
Solution:
export type IsSame<T, U> = (<G>() => G extends T ? 1 : 2) extends <
G
>() => G extends U ? 1 : 2
? true
: false
export type ReMap<T> = T extends Record<string, unknown>
? { [Key in keyof T]: T[Key] }
: T
type A = IsSame<{ a:1, b:2 }, { a:1, b:2 }> // true
// ^?
type B = IsSame<ReMap<{ a:1, b:2 }>, ReMap<{ a:1 } & { b:2 }>> // true
// ^?
Combine Remap and IsSame
💖 💪 🙅 🚩
Acid Coder
Posted on September 22, 2022
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typescript Typescript WTF Moments 8: Type Level Equality Not Working With Intersection
September 22, 2022