remove LINQ code from tokenizer

Author: jonsequitur

src/System.CommandLine.Tests/Binding/HandlerDescriptorTests.cs

@@ -6,7 +6,6 @@
 using System.IO;
 using FluentAssertions;
 using System.Linq;
-using System.Threading.Tasks;
 using Xunit;
 
 namespace System.CommandLine.Tests.Binding

src/System.CommandLine.Tests/Binding/TypeConversionTests.cs

@@ -7,7 +7,6 @@
 using FluentAssertions;
 using System.Linq;
 using Xunit;
-using System.CommandLine.Invocation;
 
 namespace System.CommandLine.Tests.Binding
 {

src/System.CommandLine.Tests/UseHelpTests.cs

@@ -6,6 +6,7 @@
 using System.CommandLine.IO;
 using System.CommandLine.Parsing;
 using System.CommandLine.Tests.Utility;
+using System.IO;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Xunit;

src/System.CommandLine/Collections/AliasedSet.cs

@@ -6,7 +6,7 @@
 
 namespace System.CommandLine.Collections
 {
-    public abstract class AliasedSet<T> : IReadOnlyCollection<T>
+    public abstract class AliasedSet<T> : IReadOnlyList<T>
         where T : class
     {
         protected IList<T> Items { get; } = new List<T>();
@@ -65,5 +65,7 @@ internal void Remove(T item)
         protected abstract IReadOnlyList<string> GetRawAliases(T item);
 
         public bool Contains(string alias) => GetByAlias(alias) != null;
+
+        public T this[int index] => Items[index];
     }
 }

src/System.CommandLine/Collections/ISymbolSet.cs

@@ -5,7 +5,7 @@
 
 namespace System.CommandLine.Collections
 {
-    public interface ISymbolSet : IReadOnlyCollection<ISymbol>
+    public interface ISymbolSet : IReadOnlyList<ISymbol>
     {
         ISymbol? GetByAlias(string alias);
     }

src/System.CommandLine/CommandLineConfiguration.cs

@@ -13,8 +13,8 @@ namespace System.CommandLine
 {
     public class CommandLineConfiguration
     {
-        private IReadOnlyCollection<InvocationMiddleware> _middlewarePipeline;
-        private Func<BindingContext, IHelpBuilder> _helpBuilderFactory;
+        private readonly IReadOnlyCollection<InvocationMiddleware> _middlewarePipeline;
+        private readonly Func<BindingContext, IHelpBuilder> _helpBuilderFactory;
         private readonly SymbolSet _symbols = new SymbolSet();
 
         public CommandLineConfiguration(
@@ -37,7 +37,18 @@ public CommandLineConfiguration(
                 throw new ArgumentException("You must specify at least one option or command.");
             }
 
-            ArgumentDelimiters = argumentDelimiters ?? new[] { ':', '=' };
+            if (argumentDelimiters is null)
+            {
+                ArgumentDelimitersInternal = new HashSet<char>
+                {
+                    ':', 
+                    '='
+                };
+            }
+            else
+            {
+                ArgumentDelimitersInternal = new HashSet<char>(argumentDelimiters);
+            }
 
             foreach (var symbol in symbols)
             {
@@ -110,8 +121,10 @@ private void AddGlobalOptionsToChildren(Command parentCommand)
 
         public ISymbolSet Symbols => _symbols;
 
-        public IReadOnlyCollection<char> ArgumentDelimiters { get; }
+        public IReadOnlyCollection<char> ArgumentDelimiters => ArgumentDelimitersInternal;
 
+        internal HashSet<char> ArgumentDelimitersInternal { get; }
+     
         public bool EnableDirectives { get; }
 
         public bool EnablePosixBundling { get; }