unified-signatures: rest parameter overloading

[WilcoBakker]

Bug Report

• TSLint version: 5.3.2
• TypeScript version: 2.3.3
• Running TSLint via: Atom

TypeScript code being linted

protected oneOf(...accepted: string[]): (arg1: string, arg2: any) => void;
protected oneOf(...accepted: number[]): (arg1: string, arg2: any) => void;

with tslint.json configuration:

{
  "extends": "tslint:recommended",
  "rules": {
    "quotemark": "double",
    "no-console": false,
    "jsdoc-format": false,
    "interface-name": false,
    "object-literal-sort-keys": false,
    "no-bitwise": false
  }
}

Actual behavior

It claims this conflicts with the unified-signatures rule because according to tslint, it can be unified to:

protected oneOf(...accepted: string[] | number[]): (arg1: string, arg2: any) => void;

However this is not supported by TypeScript as TypeScript doesn't support this unification.
It gives an error stating that a rest paramter should be of type Array.

Expected behavior

Tslint knows this is an impossible unification and so does not mark this in conflict with the unified-signatures rule.

Note: TypeScript will most likely never allow this unification as this exact issue (TypeScript part) is marked as By Design a.k.a. this is not possible on purpose. (and with a reason)

Typescript issue: microsoft/TypeScript#5077