Return a type predicate function that returns true if the type of x is ParametersOf<T> or ParametersOf<T, E>.

This is similar to TupleOf<T> or TupleOf<T, E>, but if is.OptionalOf() is specified at the trailing, the trailing elements becomes optional and makes variable-length tuple.

To enhance performance, users are advised to cache the return value of this function and mitigate the creation cost.

import { is } from "@core/unknownutil";

const isMyType = is.ParametersOf([
  is.Number,
  is.OptionalOf(is.String),
  is.Boolean,
  is.OptionalOf(is.Number),
  is.OptionalOf(is.String),
  is.OptionalOf(is.Boolean),
] as const);
const a: unknown = [0, undefined, "a"];
if (isMyType(a)) {
  // a is narrowed to [number, string | undefined, boolean, number?, string?, boolean?]
  const _: [number, string | undefined, boolean, number?, string?, boolean?] = a;
}

With predElse:

import { is } from "@core/unknownutil";

const isMyType = is.ParametersOf(
  [
    is.Number,
    is.OptionalOf(is.String),
    is.OptionalOf(is.Boolean),
  ] as const,
  is.ArrayOf(is.Number),
);
const a: unknown = [0, "a", true, 0, 1, 2];
if (isMyType(a)) {
  // a is narrowed to [number, string?, boolean?, ...number[]]
  const _: [number, string?, boolean?, ...number[]] = a;
}

Depending on the version of TypeScript and how values are provided, it may be necessary to add as const to the array used as predTup. If a type error occurs, try adding as const as follows:

import { is } from "@core/unknownutil";

const predTup = [is.Number, is.String, is.OptionalOf(is.Boolean)] as const;
const isMyType = is.ParametersOf(predTup);
const a: unknown = [0, "a"];
if (isMyType(a)) {
  // a is narrowed to [number, string, boolean?]
  const _: [number, string, boolean?] = a;
}