Function when

src/patterns.ts:646–659

(
  predicate: predicate
)

  predicate: (input: input) => input is narrowed
): GuardExcludeP<input, narrowed, excluded>;
export function when<input, predicate extends (value: input) => unknown>(
  predicate: predicate
): GuardP<
  input,
  predicate extends (value: any) => value is infer narrowed ? narrowed : never
> {
  return {
    [matcher]: () => ({
      match: <UnknownInput>(value: UnknownInput | input) => ({
        matched: Boolean(predicate(value as input)),
      }),
    }),
  };
}

/**
 * `P.select()` is a pattern which will always match,