1. Deprecated("Internal Use Only")
dynamic safeForTypedInterop(arg)

Check that that if arg is a Function it is safe to pass to JavaScript. To make a function safe, call allowInterop or allowInteropCaptureThis.

Source 

@Deprecated("Internal Use Only")
safeForTypedInterop(arg) {
  if (CHECK_JS_INVOCATIONS && arg is Function && arg is! JSFunction) {
    throw new ArgumentError(
        "Attempt to pass Function '$arg' to JavaScript via without calling allowInterop or allowInteropCaptureThis");
  }
}