TS is overly picky when declaring a class constructor type · Microsoft/TypeScript#29707

(11 comments) (6 reactions) (0 assignees)TypeScript (6,726 forks)batch import

BugDomain: classesGood First IssueHelp Wanted

Repository metrics

TypeScript Version: 3.4.0-dev.20190202

Search Terms: class, extend, constructor, any[]

Code

type ClassConstructor = new(...args: any[]) => {}

function mixin<C extends ClassConstructor>(Class: C) {
  return class extends Class {}
}

Expected behavior:

I should be able to replace ...args: any[] with ...args: unknown[], or any other signature.

Actual behavior:

Error: Type 'C' is not a constructor function type. [2507]

Playground Link: https://www.typescriptlang.org/play/index.html#src=type%20ClassConstructor%20%3D%20new(...args%3A%20unknown%5B%5D)%20%3D%3E%20%7B%7D%0D%0A%0D%0Afunction%20mixin%3CC%20extends%20ClassConstructor%3E(Class%3A%20C)%20%7B%0D%0A%20%20return%20class%20extends%20Class%20%7B%7D%0D%0A%7D