C# highlight function displays wrong colors when using string interpolation

[lennylxx]

Environment data

dotnet --info output:

.NET Command Line Tools (1.0.0-preview1-002702)

Product Information:
 Version:     1.0.0-preview1-002702
 Commit Sha:  6cde21225e

Runtime Environment:
 OS Name:     Windows
 OS Version:  10.0.10586
 OS Platform: Windows
 RID:         win10-x64

VS Code version: 1.2.1
C# Extension version: 1.1.6

Steps to reproduce

1. Open VSCode and create a C# source file: test.cs
2. Paste below content and save

using System;

namespace ConsoleApplication1
{
    class Program
    {
        public static string World = string.Empty;
        public static string Test = DuplicateString($"{nameof(World)}");

        static void Main()
        {
            Console.WriteLine("Hello " + Test);
        }

        public static string DuplicateString(string s)
        {
            return s;
        }
    }
}

Expected behavior

C# highlight function works perfect.

Actual behavior

[DustinCampbell]

This is a duplicate of #249. We'll use that issue to track this bug.