strict function type does not handle spread arguments

[beckend]

TypeScript Version: 2.7.0-dev.20171212 and 2.6.2

Code

class TargetComponent {

  public one: any;
  public two: any;

  constructor(one: any, two: any) {
    this.one = one;
    this.two = two;
  }

}

class ComponentExt extends TargetComponent {

  constructor(...args: any[]) {
    // Expected 2 arguments, but got 0 or more.
    super(...args);
  }

}

Expected behavior:
No errors.

Actual behavior:
at Super => Expected 2 arguments, but got 0 or more.

[ghost]

This isn't a --strictFunctionTypes error.
It will work if the constructor were defined as one?: any, two?: any. The problem is that with an arbitrary array, we can't be sure it has isn't empty, so we can't know that both arguments are provided. See #15849.

[beckend]

Alright, you are saying this valid javascript is not accepted in typescript in strict mode? And also that it is a feature?

[RyanCavanaugh]

https://stackoverflow.com/questions/41750390/what-does-all-legal-javascript-is-legal-typescript-mean

[ghost]

This isn't related to the --strict flag, it shoul happen regardless of compiler options.
Since you're typing everything as any right now you can get this code to work by making the parameters optional. But if you wanted to ensure that they're not undefined, then you also need to ensure that all super calls pass in at least two arguments.
Also, in JavaScript it's not necessary to declare a constructor if all you're doing is delegating to a parent class constructor, so if constructor(...args: any[]) { super(...args); } is really all you're doing, you could just remove that and it will work.

[beckend]

The code was more of a demonstration, of course the point with that constructor was to make something happen, and in many cases you don't really need to care about the arguments and thus you use spread operator. The demonstration might as well be proxying two functions and it would produce the same error.

But so far I get that this is indeed intentional from typescript and this was actually a aware decision you made...which bring this issue to it's conclusion so you can close this at your discretion.