csc doesn't accept tokens that are in the Ll class.

[stephen-hawley]

Version Used:
Microsoft (R) Visual C# Compiler version 2.6.0.62309 (d3f6b8e)
Steps to Reproduce:
Use the following code:

using System;
using System.Runtime.InteropServices;
namespace UnicodeTests
{
    public class TopLevelEntities
    {
        public static double 𝑒
        {
            get
            {
                return 2.718
            }
        }
    }

Compile with csc.
Expected Behavior:
Correct compile.
Actual Behavior:
/var/folders/jq/jq6r64mn1wvg18lp0bw71f780000gn/T/58603c0f-8712-4a9a-adaa-bf5b607741ee/TopLevelEntitiesUnicodeTests.cs(8,30): error CS1519: Invalid token '�' in class, struct, or interface member declaration

The C# specification states that an identifier can start with a letter-character or a _. A letter-character is defined as "A Unicode character of classes Lu, Ll, Lt, Lm, Lo, or Nl". The letter epsilon (u01d452), referenced above, is in the Ll class.

[chamons]

Also fails with mcs I believe - @marek-safar

[jcouv]

Tagging @gafter

[gafter]

This is a dup of #9731 #13474 and #13560. Roslyn does not correctly process identifier characters that are represented as surrogate pairs.