function isFunction<T extends FunctionOrConstructor>(
  it: T | unknowns,
): it is FunctionOrConstructor<any, any, any> extends T ? Function : T;

import { isFunction } from "jsr:@nick/is/function";

console.log(isFunction(() => {})); // true
console.log(isFunction(function () {})); // true
console.log(isFunction(class {})); // true
console.log(isFunction(new Function())); // true
console.log(isFunction({})); // false
console.log(isFunction(1)); // false

function isFunction<T = any, A extends readonly any[] = any[]>(
  it: Fn<T, A> | unknowns,
): it is Fn<T, A>;

function isFunction<T = any, A extends readonly any[] = any[], R = any>(
  it: ThisFn<T, A, R> | unknowns,
): it is ThisFn<T, A, R>;

function isFunction(it: unknown): it is Function;

function isFunction(it: unknown): it is FunctionOrConstructor;

export type Fn<T = any, A extends readonly any[] = any[]> = (...args: A) => T;

export type FunctionOrConstructor<
  T = any,
  A extends readonly any[] = any[],
  R = void,
> = Constructor<R, A> | Fn<R, A> | ThisFn<T, A, R> | Function;

export type ThisFn<T = any, A extends readonly any[] = any[], R = any> = (
  this: T,
  ...args: A
) => R;