Const enums should be considered compile-time constants for computed property names

[JoshuaKGoldberg]

TypeScript Version: 1.8.0

Code

const enum Color {
    Blue,
    Red = 1
}

interface IColors {
    // Error: A computed property name in an interface must be a compile-time constant
    [Color.Blue]: any;
    [Color.Red]: any;

    // No errors thrown
    [2]: any;
}

Expected behavior:
No red squigglies

Actual behavior:
Red squigglies, because a const enum's value isn't considered a compile-time constant (isn't it?).

[mhegazy]

this is a duplicate of #5579.

The issue here is not that they are constants or not. the issue is that the way the compiler is layered, it does not necessary know what they are when a it forms the shape of the internal data structure representing the interface or class (symbol). see #5579 for more details.