keyof does not include well known symbols

[mgroenhoff]

TypeScript Version: 2.9.1

Search Terms:
keyof well known symbol

Code

const s = Symbol("s");

interface I {
    n: number;
    [s]: string;
    [Symbol.iterator](): IterableIterator<[string, string]>;
}

type K = keyof I;
type T = I[K];

Expected behavior:

type K = keyof I; // type K = typeof s | "n" | typeof Symbol.iterator
type T = I[K]; // type T = string | number | () => IterableIterator<[string, string]>

Actual behavior:

type K = keyof I; // type K = typeof s | "n"
type T = I[K]; // type T = string | number

[mhegazy]

Predicated on #21603

[weswigham]

@mhegazy we're going to need an LKG post-lib references to stage this change. We probably also want to have a forked copy of the node @types definitions which uses lib references for our own build until we ship the feature and can push the change to DT.

[weswigham]

@RyanCavanaugh if we want this in 3.1, we need to look into taking #24738

[bluenote10]

This feature would significantly simplify writing generic wrappers needed in Solid. See this SO question for an explanation of the use case in Solid. Looking forward to a release.

CC @ryansolid

[jcalz]

Another relevant SO question.

Could we remove the "fixed" tag from this issue since it means the same thing as the less-confusing "fix available"?