casting address of pointer functions to a type

[Kerp]

Hi again just need to know what i'm doing wrong on this subject

But first here is my code
    
    
    var vkCreateDebugReportCallbackEXT = 
cast[PFN_vkCreateDebugReportCallbackEXT](vkGetInstanceProcAddr(inst,"vkCreateDebugReportCallbackExt"))
    
    

i get a message from the compiler about this when i try it, that it cannot 
convert to a pointer type. i believe its because its pointer function in c and 
maybe nim does not like casting those, i dunno?