Steps to reproduce:

1. Make sure Unity and VS2015 are installed
2. Set the code editor to VS2015 in preferences
3. Create a new project
4. Add a new script to the camera, (NewBehaviourScript)
5. Double-click on the script to open Visual Studio
6. In the Update() method, type "Instan" and optionally press Ctrl+Space to try and force the autocomplete dialog to open and autocomplete Instantiate
7. Observe: there is no autocomplete for any Unity methods

Workaround: Switch to MonoDevelop, open script there, then switch back to VS.

Reproduced with: 5.3.2p1, 5.4.0b4