The type of a custom Zone.runUnary 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 and value
arg are the function and argument
which was passed to the Zone.runUnary of
The default behavior of Zone.runUnary is
f with argument
arg in the current zone,
A custom handler can do things before, after or instead of
The function must only access zone-related functionality through
It should not depend on the current zone (Zone.current).
typedef RunUnaryHandler = R Function<R, T>( Zone self, ZoneDelegate parent, Zone zone, R Function(T arg) f, T arg);