I filed this here instead of DefinitelyTyped because I suspect it's an issue with how extended attributes are being parsed.

When parsing the following WebIDL:

interface AbortSignal : EventTarget {
  [Exposed=(Window,Worker), NewObject, Throws]
  static AbortSignal timeout([EnforceRange] unsigned long long milliseconds);
}

The type definition defines:

export interface ExtendedAttributeRightHandSideIdentifier {
  type: "identifier"
  value: string
}

export interface ExtendedAttributeRightHandSideIdentifierList {
  type: "identifier-list"
  value: ExtendedAttributeRightHandSideIdentifier[]
}

However, the resulting AST is:

{
  "type": "extended-attribute",
  "name": "Exposed",
  "rhs": {
    "type": "identifier-list",
    "value": [
      {
        "value": "Window"
      },
      {
        "value": "Worker"
      }
    ]
  },
  "arguments": []
}

I suspect for consistency sake, these value entries should be of type identifier?