anchor.diff:          [<Emit("new $0($1...)")>] abstract Create: ?iterable: seq<'K * 'V> -> WeakMap<'K, 'V>
   
       and [<AllowNullLiteral>] Set<'T> =
  -        abstract size: float with get, set
  +        abstract size: int
           abstract add: value: 'T -> Set<'T>
           abstract clear: unit -> unit
           abstract delete: value: 'T -> bool
  
positive.code:     let [<Global>] WeakSet: WeakSetConstructor = jsNative
      let [<Global>] Promise: PromiseConstructor = jsNative
      let [<Global>] RegExp: RegExpConstructor = jsNative
      let [<Global>] ArrayBuffer: ArrayBufferConstructor = jsNative
      let [<Global>] DataView: DataViewConstructor = jsNative
      let [<Global>] eval: string -> string = jsNative
      let [<Global>] isFinite: float -> bool = jsNative
      let [<Global>] isNaN: float -> bool = jsNative
  
negative.code:         abstract buffer: ArrayBuffer
          abstract byteLength: int
          abstract byteOffset: int
  
      and ArrayBufferViewConstructor =
          [<Emit "new $0($1...)">] abstract Create: size: int -> ArrayBufferView
  
      and [<AllowNullLiteral>] DataView =
          abstract buffer: ArrayBuffer
  