mostly-isolated issue 888

gistfile1.txt

import python except expr

type
  # A non-borrowed (counted) reference. Avoid copying these around! Nimrod doesn't have
  # the equivalent of an assignment constructor (yet?), so any copy of PyRef must be counted (use dup for that).
  PyRef = object {.inheritable, byref.} 
    p: PPyObject
  PPyRef* = ref PyRef

  EPyException = object of E_Base

# forward declarations
proc getattr*(o: PPyRef, name: cstring) : PPyRef

proc handle_error(s : string) =
  PyErr_Print()
  raise newException(EPyException, s)

proc check(p: PPyObject) : PPyObject =
  if p == nil: handle_error("check(nil)")
  result = p

proc check(x: int) : int =
  if x == -1: handle_error("check(-1)")
  result = x

converter to_PPyRef*(p: PPyObject) : PPyRef = 
  new result
  result.p = check(p)

proc new_list*(size: int): PPyRef = PyList_New(size)
proc new_tuple*(size: int): PPyRef = PyTuple_New(size)

converter to_py*(i: int) : PPyRef = PyInt_FromLong(int32(i))
proc to_py*(s: cstring) : PPyRef = PyString_fromString(s)

proc to_tuple*(vals: openarray[PPyRef]): PPyRef = 
  result = new_tuple(len(vals))
  for i in 0..len(vals)-1:
    let p = vals[i].p
    discard check(PyTuple_SetItem(result.p, i, p))
    Py_INCREF(p) # PyTuple_SetItem steals refs, I don't want that
  
proc `()`*(f: PPyRef, args: varargs[PPyRef]): PPyRef {.discardable.} = 
  let args_tup = to_tuple(args)
  PyObject_CallObject(f.p, args_tup.p)

proc destroy(o: var PyRef) {.destructor.} =
  if o.p != nil:
    echo "decrefing"
    Py_DECREF(o.p)
    o.p = nil

proc getattr*(o: PPyRef, name: cstring) : PPyRef =
  result = to_PPyRef(PyObject_GetAttrString(o.p, name))

proc py_import*(name : cstring) : PPyRef =
  PyImport_ImportModule(name)

type
  Interpreter = object {.bycopy.} 

proc make_interpreter() : Interpreter =
  Py_Initialize()
  result = Interpreter()
  
proc destroy(interpreter : Interpreter) {.destructor.} =
  Py_Finalize()

var py_interpreter = make_interpreter()

let n = 100
let lx = new_list(0)
for i in 1..n:
  # compilation succeeds:
  getattr(lx, "append")(to_py(1))
  # compilation fails:
  getattr(lx, "append")(1)