Just define getIoHandler for HackDispatcher instead of using when

Simplifies it and feels less hacky

Remove the type that Araq says sn't required

asynctools/asyncipc.nim

@@ -130,7 +130,6 @@ elif defined(windows):
  ioPort: Handle
  handles: HashSet[AsyncFD]
  HackDispatcher = ptr HackDispatcherImpl
- Dispatcher = HackDispatcher | PDispatcher
 
  proc openEvent(dwDesiredAccess: Dword, bInheritHandle: WINBOOL,
  lpName: WideCString): Handle
@@ -143,7 +142,7 @@ elif defined(windows):
  proc interlockedAnd(a: ptr int32, b: int32)
  {.importc: "_InterlockedAnd", header: "intrin.h".}
 
- proc getCurrentDispatcher(): Dispatcher =
+ proc getCurrentDispatcher(): auto =
  when defined(nimv2):
  # New runtime will run into segfault if using HackDispatcher, but old versions of Nim require
  # HackDispatcher so we can access some internal fields.
@@ -153,12 +152,9 @@ elif defined(windows):
  else:
  cast[HackDispatcher](getGlobalDispatcher())
 
- template getIoHandler(p: Dispatcher): Handle =
+ template getIoHandler(p: HackDispatcher): Handle =
  ## Returns the IO handle for a dispatcher.
- when p is PDispatcher:
- p.getIoHandler()
- else:
- p.ioPort
+ p.ioPort
 
  proc `$`*(ipc: AsyncIpc): string =
  if ipc.handleMap == Handle(0):