optimizer bug?

optbug.d

module util.device;

import directx.d3d11;
import directx.dxgi;

IGraphicsDevice[] GetDevices()
{
	size_t numAdapters;
	IDXGIFactory fact;
	IDXGIAdapter temp;
	IGraphicsDevice[] devices;

	assert( SUCCEEDED( CreateDXGIFactory(&IID_IDXGIFactory, cast(void**)&fact) ));
	while( fact.EnumAdapters(cast(UINT)numAdapters, &temp) != DXGI_ERROR_NOT_FOUND ) // optimizer error: dereferencing null pointer
	{ 
		IGraphicsDevice device = new GraphicsDeviceD3D(temp); 
		devices ~= device;
		++numAdapters;
	}
	
	return devices;
}

IGraphicsDevice GetDefaultDevice()
{
  return GetDevices()[0];
}

abstract class IGraphicsDevice
{
}

class GraphicsDeviceD3D : IGraphicsDevice
{
	private this(IDXGIAdapter adapter) { dxgiAdapter = adapter; }
	package ID3D11Device d3dDevice;
	package IDXGIAdapter dxgiAdapter;
}

unittest
{
	auto device = GetDefaultDevice();
	assert(device);
}

void main()
{
	import std.stdio;
	writeln(GetDefaultDevice());
}

package.json

{
	"name": "optbug",
	"description": "bug",
	"copyright": "Copyright © 2014, evilrat",
	"authors": ["evilrat"],
	"dependencies": {
		"directx-d": "~master"
	},
	"libs": ["phobos64", "d3d11", "dxgi", "user32", "kernel32"],
	"dflags": ["-m64"],
}