Nim proc pointers

[minidude22]

Hello friends I'm wrapping a small C library for hooking APIs and it ends up 
having a method like this:
    
    
    proc subhook_new*(src: pointer; dst: pointer; flags: subhook_flags_t = 
subhook_flags.NONE): subhook_t {.importc, cdecl, impsubhookHdr.}
    
    
    Run

So I need to end up passing it two pointers to procs. I've got a small example 
where I'm attempting to hook my own method from Nim: 
    
    
    import strformat
    import dependencies/subhook
    
    type addProc = proc(a, b: uint32): uint32 {.cdecl.}
    
    var add_hook: subhook_t
    
    proc add(a, b: uint32): uint32 {.cdecl.} =
      result = a + b
      echo &"Add: {a} + {b} = {result}\n"
    
    
    proc newAdd(a, b: uint32): uint32 {.cdecl.} =
      echo "You've been hooked my guy!!"
      let
        newA = a + 10
        newB = b + 10
      
      # Call the original method after we've done our extra work
      let trampoline = subhook_get_trampoline(add_hook)
      if trampoline == nil:
        raise newException(Exception, "Trampoline not found! Likely a 
disassembly issue")
      
      cast[addProc](trampoline)(newA, newB)
    
    
    # We have to pass the procs into here so we can cast them to pointers 
without
    # nim freaking out
    proc hookAdds(a, b: addProc) =
      add_hook = subhook_new(cast[pointer](a), cast[pointer](b))
      
      discard subhook_install(add_hook)
    
    
    proc main() =
      hookAdds(add, newAdd)
      
      discard add(1, 1)
      
      discard subhook_remove(add_hook)
      subhook_free(add_hook)
    
    
    if isMainModule:
      main()
    
    
    Run

This is working however I'd like to have a better way to call it. Why can I not 
`cast[pointer](add)` from main()? And how could I have a hook method that's 
generic without having to define the proc type?