Reproduction for `long?` bug

Dockerfile

# The same image used by mybinder.org
FROM mcr.microsoft.com/quantum/iqsharp-base:0.10.1912.0501
ENV IQSHARP_HOSTING_ENV=cgranade-longq-bug-repro

# Make sure the contents of our repo are in ${HOME}
# Required for mybinder.org
COPY . ${HOME}
USER root
RUN chown -R ${USER} ${HOME}
USER ${USER}

longq-bug-repro.ipynb

{
 "cells": [
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "application/json": "{\"rows\":[{\"@type\":\"@tuple\",\"Item1\":\"iqsharp\",\"Item2\":\"0.10.1912.501\"},{\"@type\":\"@tuple\",\"Item1\":\"Jupyter Core\",\"Item2\":\"1.2.20112.0\"},{\"@type\":\"@tuple\",\"Item1\":\".NET Runtime\",\"Item2\":\".NETCoreApp,Version=v3.0\"}]}",
      "text/html": [
       "<table><thead><tr><th>Component</th><th>Version</th></tr></thead><tbody><tr><td>iqsharp</td><td>0.10.1912.501</td></tr><tr><td>Jupyter Core</td><td>1.2.20112.0</td></tr><tr><td>.NET Runtime</td><td>.NETCoreApp,Version=v3.0</td></tr></tbody></table>"
      ],
      "text/plain": [
       "Component    Version\n",
       "------------ ------------------------\n",
       "iqsharp      0.10.1912.501\n",
       "Jupyter Core 1.2.20112.0\n",
       ".NET Runtime .NETCoreApp,Version=v3.0\n"
      ]
     },
     "metadata": {},
     "output_type": "display_data"
    }
   ],
   "source": [
    "%version"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 2,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "application/json": "[\"PrepareCatState\"]",
      "text/html": [
       "<ul><li>PrepareCatState</li></ul>"
      ],
      "text/plain": [
       "PrepareCatState"
      ]
     },
     "execution_count": 2,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "operation PrepareCatState(register : Qubit[]) : Unit {\n",
    "    H(register[0]);\n",
    "    for (target in register[1...]) {\n",
    "        CNOT(register[0], target);\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 3,
   "metadata": {},
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      ": error IQS000: Could not compile Roslyn dll from working folder.\n",
      ": error CS1503: Argument 1: cannot convert from 'long?' to 'long'\n"
     ]
    }
   ],
   "source": [
    "operation PrepareCatState(register : Qubit[]) : Unit is Adj {\n",
    "    H(register[0]);\n",
    "    for (target in register[1...]) {\n",
    "        CNOT(register[0], target);\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 4,
   "metadata": {},
   "outputs": [
    {
     "data": {
      "application/json": "[\"PrepareCatState\"]",
      "text/html": [
       "<ul><li>PrepareCatState</li></ul>"
      ],
      "text/plain": [
       "PrepareCatState"
      ]
     },
     "execution_count": 4,
     "metadata": {},
     "output_type": "execute_result"
    }
   ],
   "source": [
    "operation PrepareCatState(register : Qubit[]) : Unit is Ctl {\n",
    "    H(register[0]);\n",
    "    for (target in register[1...]) {\n",
    "        CNOT(register[0], target);\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 5,
   "metadata": {},
   "outputs": [
    {
     "name": "stderr",
     "output_type": "stream",
     "text": [
      ": error IQS000: Could not compile Roslyn dll from working folder.\n",
      ": error CS1503: Argument 1: cannot convert from 'long?' to 'long'\n",
      ": error CS1503: Argument 1: cannot convert from 'long?' to 'long'\n"
     ]
    }
   ],
   "source": [
    "operation PrepareCatState(register : Qubit[]) : Unit is Adj + Ctl {\n",
    "    H(register[0]);\n",
    "    for (target in register[1...]) {\n",
    "        CNOT(register[0], target);\n",
    "    }\n",
    "}"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": null,
   "metadata": {},
   "outputs": [],
   "source": []
  }
 ],
 "metadata": {
  "kernelspec": {
   "display_name": "Q#",
   "language": "qsharp",
   "name": "iqsharp"
  },
  "language_info": {
   "file_extension": ".qs",
   "mimetype": "text/x-qsharp",
   "name": "qsharp",
   "version": "0.4"
  }
 },
 "nbformat": 4,
 "nbformat_minor": 2
}