allowInteropCaptureThis function

Implementation

Function allowInteropCaptureThis(Function f) {
  if (JS('bool', 'typeof(#) == "function"', f)) {
    // Behavior when the function is already a JS function is unspecified.
    throw new ArgumentError(
        "Function is already a JS function so cannot capture this.");
    return f;
  } else {
    return _convertDartFunctionFastCaptureThis(f);
  }
}