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feat: refine .split() return type #56841

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feat: refine .split() return type #56841

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28 changes: 28 additions & 0 deletions src/lib/es2015.symbol.wellknown.d.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -162,6 +162,10 @@ interface PromiseConstructor {
readonly [Symbol.species]: PromiseConstructor;
}

// TODO: inline at usage site
type NonEmptyStringParam<S extends string> = S extends '' ? never : S;
type NonZeroNumberParam<N extends number> = N extends 0 ? never : N;

interface RegExp {
/**
* Matches a string with this regular expression, and returns an array containing the results of
Expand Down Expand Up @@ -207,6 +211,11 @@ interface RegExp {
* @param limit if not undefined, the output array is truncated so that it contains no more
* than 'limit' elements.
*/
[Symbol.split]<S extends string>(string: NonEmptyStringParam<S>): [string, ...string[]];
[Symbol.split]<S extends string, N extends number>(
string: NonEmptyStringParam<S>,
limit: NonZeroNumberParam<N>
): [string, ...string[]];
[Symbol.split](string: string, limit?: number): string[];
}

Expand Down Expand Up @@ -247,6 +256,25 @@ interface String {
* @param splitter An object that can split a string.
* @param limit A value used to limit the number of elements returned in the array.
*/
split(
splitter: {
[Symbol.split]<S extends string>(string: NonEmptyStringParam<S>): [string, ...string[]];
[Symbol.split]<S extends string, NN extends number>(
string: NonEmptyStringParam<S>,
limit: NonZeroNumberParam<NN>
): [string, ...string[]];
}
): [string, ...string[]];
split<N extends number>(
splitter: {
[Symbol.split]<S extends string>(string: NonEmptyStringParam<S>): [string, ...string[]];
[Symbol.split]<S extends string, NN extends number>(
string: NonEmptyStringParam<S>,
limit: NonZeroNumberParam<NN>
): [string, ...string[]];
},
limit: NonZeroNumberParam<N>
): [string, ...string[]];
split(splitter: { [Symbol.split](string: string, limit?: number): string[]; }, limit?: number): string[];
}

Expand Down
5 changes: 5 additions & 0 deletions src/lib/es5.d.ts
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Expand Up @@ -470,6 +470,11 @@ interface String {
* @param separator A string that identifies character or characters to use in separating the string. If omitted, a single-element array containing the entire string is returned.
* @param limit A value used to limit the number of elements returned in the array.
*/
split<S extends string>(separator: NonEmptyStringParam<S>): [string, ...string[]];
split<S extends string, N extends number>(
separator: NonEmptyStringParam<S>,
limit: NonZeroNumberParam<N>
): [string, ...string[]];
split(separator: string | RegExp, limit?: number): string[];

/**
Expand Down