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freddi301/Exact.ts

Created July 16, 2025 13:34
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Typescript exact type
Raw
Exact.ts
type Exact<A, B extends A> = A extends B
? B
: B extends Record<any, any>
? { [K in keyof B]: K extends keyof A ? Exact<A[K], B[K]> : never }
: B extends Array<any>
? { [K in keyof B]: K extends keyof A ? Exact<A[K], B[K]> : never }
: never;
function invariantize<A, R>(
fun: (a: A) => R
): <B extends A>(a: Exact<A, B>) => R {
return fun as any;
}
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