Fix #2413: Avoid global state in `TokenRole`.

We can already compactly store a `TokenRole` via the index+lookup in the `Role` base class.
The lookup in the base class is thread-safe; the one removed here was not.

ICSharpCode.Decompiler/CSharp/Syntax/CSharpTokenNode.cs

@@ -85,7 +85,12 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 
 		int TokenLength {
 			get {
-				return TokenRole.TokenLengths[(int)(this.flags >> AstNodeFlagsUsedBits)];
+				uint tokenRoleIndex = (this.flags >> AstNodeFlagsUsedBits);
+				if (Role.GetByIndex(tokenRoleIndex) is TokenRole r)
+				{
+					return r.Length;
+				}
+				return 0;
 			}
 		}
 
@@ -99,12 +104,17 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		{
 			this.startLocation = location;
 			if (role != null)
-				this.flags |= role.TokenIndex << AstNodeFlagsUsedBits;
+				this.flags |= role.Index << AstNodeFlagsUsedBits;
 		}
 
 		public override string ToString(CSharpFormattingOptions formattingOptions)
 		{
-			return TokenRole.Tokens[(int)(this.flags >> AstNodeFlagsUsedBits)];
+			uint tokenRoleIndex = (this.flags >> AstNodeFlagsUsedBits);
+			if (Role.GetByIndex(tokenRoleIndex) is TokenRole r)
+			{
+				return r.Token;
+			}
+			return string.Empty;
 		}
 
 		public override void AcceptVisitor(IAstVisitor visitor)
@@ -129,4 +139,3 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 		}
 	}
 }
-

ICSharpCode.Decompiler/CSharp/Syntax/TokenRole.cs

@@ -1,5 +1,3 @@
-using System.Collections.Generic;
-
 namespace ICSharpCode.Decompiler.CSharp.Syntax
 {
 	/// <summary>
@@ -7,57 +5,20 @@ namespace ICSharpCode.Decompiler.CSharp.Syntax
 	/// </summary>
 	public sealed class TokenRole : Role<CSharpTokenNode>
 	{
-		internal readonly static List<string> Tokens = new List<string>();
-		internal readonly static List<int> TokenLengths = new List<int>();
-		internal readonly uint TokenIndex;
-
-		static TokenRole()
-		{
-			// null token
-			Tokens.Add("");
-			TokenLengths.Add(0);
-		}
-
 		/// <summary>
 		/// Gets the token as string. Note that the token Name and Token value may differ.
 		/// </summary>
-		public string Token {
-			get;
-			private set;
-		}
+		public string Token { get; }
 
 		/// <summary>
 		/// Gets the char length of the token.
 		/// </summary>
-		public int Length {
-			get;
-			private set;
-		}
-
+		public int Length { get; }
 
 		public TokenRole(string token) : base(token, CSharpTokenNode.Null)
 		{
 			this.Token = token;
 			this.Length = token.Length;
-
-			bool found = false;
-			for (int i = 0; i < Tokens.Count; i++)
-			{
-				var existingToken = Tokens[i];
-				if (existingToken == token)
-				{
-					TokenIndex = (uint)i;
-					found = true;
-					break;
-				}
-			}
-			if (!found)
-			{
-				TokenIndex = (uint)Tokens.Count;
-				Tokens.Add(token);
-				TokenLengths.Add(this.Length);
-			}
 		}
 	}
 }
-