The type of a custom Zone.registerUnaryCallback implementation function.
Receives the Zone that the handler was registered on as
a delegate forwarding to the handlers of
self's parent zone as
and the current zone where the error was uncaught as
which will have
self as a parent zone.
f is the function which was passed to the
which was passed to the Zone.registerUnaryCallback of
The handler should return either the function
or another function replacing
typically by wrapping
f in a function
which does something extra before and after invoking
The function must only access zone-related functionality through
It should not depend on the current zone (Zone.current).
typedef RegisterUnaryCallbackHandler = ZoneUnaryCallback<R, T> Function<R, T>( Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f);