IntelliSense error: a reference cannot be bound to an initonly field?

Question

I have a C++/CLI class like this:

// MyClass.h
#pragma once

namespace MyNamespace {
    using namespace System;

    public ref class MyClass {
    private:
        MyClass();
        IntPtr m_ptr;
    };
}

// MyClass.cpp
#include "MyClass.h"
using namespace System;

namespace MyNamespace {
    MyClass::MyClass() {
        m_ptr = IntPtr::Zero;
    }
}

The project compiles without errors or warnings, however the line m_ptr = IntPtr::Zero is always underlined red with an IntelliSense error: "a reference cannot be bound to an initonly field". What gives? How can I get rid of this?

This is in Visual Studio 2012 Premium Edition but the Platform Toolset is Visual Studio 2008 (v90).

Answer 1

Well, it is a bug in the IntelliSense parser. Written by the Edison Design Group. Pretty famous for writing C++ front-ends but C++/CLI has certainly given them a workout. It has trouble with initonly fields in general (IntPtr::Zero is initonly), something similar here but not otherwise related to this bug. Not having any equivalent in C++ may well be a contributing factor.

It doesn't get put the test much with code like this, the assignment is entirely superfluous. The CLR already makes a hard guarantee that all fields in a managed class are zero-initialized.

So workaround #1 is to just omit the assignment, it doesn't do anything useful.

Workaround #2 is to use the standard C++ constructor initialization syntax:

   MyClass::MyClass() : m_ptr(IntPtr::Zero) {}

Workaround #3, way at the bottom of the list is to initialize it like this, avoiding the initonly field:

MyClass::MyClass() {
    m_ptr = IntPtr();
}

But I'd certainly recommend #1.