type MyProc* = proc() {.cdecl.} proc testProc() {.cdecl.} = echo "Hello World" proc callPointer(p: pointer) = let function = cast[MyProc](p) function() proc toPointer(function: MyProc) = let p: pointer = cast[pointer](function) # Error: expression cannot be cast to pointer callPointer(p) toPointer(testProc)