Looking at #4648 brought this up -

declare module JSX {
  interface IntrinsicElements {
    ["my-custom-element"]: MyCustomElementClass
  }
}

We should allow string literals in computed property names in interfaces. Right now we only allow well-know symbols, but allowing all primitive literals (of valid indexer types, I suppose) should be supported.

This is a spec change - section 2.2.3 would need to be updated to reflect this, but, IMO, is fairly important and worth the change. We can't strongly type, say, tslint.json result structures right now, as we lack this.