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Merge the keys of a union or intersection of objects into a single type.
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/** | |
* Merge the keys of a union or intersection of objects into a single type. | |
* | |
* @example | |
* ```ts | |
* type GetBlockOptions = { | |
* includeTransactions?: boolean | undefined | |
* } & ( | |
* | { | |
* blockHash?: string | undefined; | |
* blockNumber?: never | undefined; | |
* blockTag?: never | undefined; | |
* } | |
* | { | |
* blockHash?: never | undefined; | |
* blockNumber?: bigint | undefined; | |
* blockTag?: never | undefined; | |
* } | |
* | { | |
* blockHash?: never | undefined; | |
* blockNumber?: never | undefined; | |
* blockTag?: string | undefined; | |
* } | |
* ) | |
* | |
* type Merged = MergeKeys<GetBlockOptions>; | |
* // { | |
* // includeTransactions?: boolean | undefined; | |
* // blockHash?: string | undefined; | |
* // blockNumber?: bigint | undefined; | |
* // blockTag?: string | undefined; | |
* // } | |
* ``` | |
*/ | |
export type MergeKeys<T> = | |
UnionToIntersection<T> extends infer I | |
? { | |
// Each key of the intersection is first checked against the union type, | |
// T. If it exists in every member of T, then T[K] will be a union of | |
// the value types. Otherwise, I[K] is used. I[K] is the value type of | |
// the key in the intersection which will be `never` for keys with | |
// conflicting value types. | |
[K in keyof I]: K extends keyof T ? T[K] : I[K]; | |
} | |
: never; | |
// https://gist.github.com/ryangoree/e816db56e5fc12aab14e64cea415436c | |
type UnionToIntersection<T> = ( | |
T extends any ? (member: T) => any : never | |
) extends (member: infer R) => any | |
? R | |
: never; |
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