From 1932b9de5a54b94709f55e9627ef40053c5d17ec Mon Sep 17 00:00:00 2001
From: Jon Sequeira <jonsequeira@gmail.com>
Date: Mon, 2 May 2022 18:16:42 -0700
Subject: [PATCH 1/4] reduce SetHandler overloads to max 8 generic type
 parameters

---
 ...ommandLine_api_is_not_changed.approved.txt |  16 -
 .../Binding/SetHandlerTests.cs                |  68 +--
 src/System.CommandLine/Handler.Action.cs      | 555 +++++-------------
 src/System.CommandLine/Handler.Func.cs        | 555 +++++-------------
 4 files changed, 328 insertions(+), 866 deletions(-)

diff --git a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
index 56a0a185ff..7880f226af 100644
--- a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
+++ b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
@@ -113,14 +113,6 @@
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Action<T1,T2,T3,T4,T5,T6> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T>(this Command command, Func<T,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2>(this Command command, Func<T1,T2,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2, T3>(this Command command, Func<T1,T2,T3,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
@@ -129,14 +121,6 @@
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Func<T1,T2,T3,T4,T5,T6,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
     public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
   public interface IConsole : System.CommandLine.IO.IStandardError, System.CommandLine.IO.IStandardIn, System.CommandLine.IO.IStandardOut
   public abstract class IdentifierSymbol : Symbol, System.CommandLine.Completions.ICompletionSource
     public System.Collections.Generic.IReadOnlyCollection<System.String> Aliases { get; }
diff --git a/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs b/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
index af87d84660..92387beb79 100644
--- a/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
+++ b/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
@@ -282,14 +282,6 @@ protected override CustomType GetBoundValue(BindingContext bindingContext)
         [InlineData(6)]
         [InlineData(7)]
         [InlineData(8)]
-        [InlineData(9)]
-        [InlineData(10)]
-        [InlineData(11)]
-        [InlineData(12)]
-        [InlineData(13)]
-        [InlineData(14)]
-        [InlineData(15)]
-        [InlineData(16)]
         public void Binding_is_correct_for_Action_overload_having_arity_(int arity)
         {
             var command = new RootCommand();
@@ -329,31 +321,7 @@ public void Binding_is_correct_for_Action_overload_having_arity_(int arity)
                 8 => new Action<int, int, int, int, int, int, int, int>(
                     (i1, i2, i3, i4, i5, i6, i7, i8) =>
                         Received(i1, i2, i3, i4, i5, i6, i7, i8)),
-                9 => new Action<int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9)),
-                10 => new Action<int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10)),
-                11 => new Action<int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11)),
-                12 => new Action<int, int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12)),
-                13 => new Action<int, int, int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13)),
-                14 => new Action<int, int, int, int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14)),
-                15 => new Action<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15)),
-                16 => new Action<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15, i16) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15, i16)),
-
+              
                 _ => throw new ArgumentOutOfRangeException()
             };
 
@@ -404,14 +372,6 @@ Task Received(params int[] values)
         [InlineData(6)]
         [InlineData(7)]
         [InlineData(8)]
-        [InlineData(9)]
-        [InlineData(10)]
-        [InlineData(11)]
-        [InlineData(12)]
-        [InlineData(13)]
-        [InlineData(14)]
-        [InlineData(15)]
-        [InlineData(16)]
         public void Binding_is_correct_for_Func_overload_having_arity_(int arity)
         {
             var command = new RootCommand();
@@ -451,31 +411,7 @@ public void Binding_is_correct_for_Func_overload_having_arity_(int arity)
                 8 => new Func<int, int, int, int, int, int, int, int, Task>(
                     (i1, i2, i3, i4, i5, i6, i7, i8) =>
                         Received(i1, i2, i3, i4, i5, i6, i7, i8)),
-                9 => new Func<int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9)),
-                10 => new Func<int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10)),
-                11 => new Func<int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11)),
-                12 => new Func<int, int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12)),
-                13 => new Func<int, int, int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13)),
-                14 => new Func<int, int, int, int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14)),
-                15 => new Func<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15)),
-                16 => new Func<int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, int, Task>(
-                    (i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15, i16) =>
-                        Received(i1, i2, i3, i4, i5, i6, i7, i8, i9, i10, i11, i12, i13, i14, i15, i16)),
-
+             
                 _ => throw new ArgumentOutOfRangeException()
             };
 
diff --git a/src/System.CommandLine/Handler.Action.cs b/src/System.CommandLine/Handler.Action.cs
index f3aa9db6ed..4dc80406f7 100644
--- a/src/System.CommandLine/Handler.Action.cs
+++ b/src/System.CommandLine/Handler.Action.cs
@@ -4,411 +4,182 @@
 using System.CommandLine.Binding;
 using System.CommandLine.Invocation;
 
-namespace System.CommandLine
+namespace System.CommandLine;
+
+/// <summary>
+/// Provides methods for creating and working with command handlers.
+/// </summary>
+public static partial class Handler
 {
     /// <summary>
-    /// Provides methods for creating and working with command handlers.
+    /// Sets a command's handler based on an <see cref="Action"/>.
     /// </summary>
-    public static partial class Handler
-    {
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action"/>.
-        /// </summary>
-        public static void SetHandler(
-            this Command command,
-            Action handle) =>
-            command.Handler = new AnonymousCommandHandler(_ => handle());
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T}"/>.
-        /// </summary>
-        public static void SetHandler<T>(
-            this Command command,
-            Action<T> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
-
-                    handle(value1!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2>(
-            this Command command,
-            Action<T1, T2> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-
-                    handle(value1!, value2!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3>(
-            this Command command,
-            Action<T1, T2, T3> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4>(
-            this Command command,
-            Action<T1, T2, T3, T4> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
+    public static void SetHandler(
+        this Command command,
+        Action handle) =>
+        command.Handler = new AnonymousCommandHandler(_ => handle());
 
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T}"/>.
+    /// </summary>
+    public static void SetHandler<T>(
+        this Command command,
+        Action<T> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
 
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!);
-                });
+                handle(value1!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2>(
+        this Command command,
+        Action<T1, T2> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
 
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!);
-                });
+                handle(value1!, value2!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3>(
+        this Command command,
+        Action<T1, T2, T3> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!);
+            });
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
-                    var value15 = GetValueForHandlerParameter<T15>(symbols, ref index, context);
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4>(
+        this Command command,
+        Action<T1, T2, T3, T4> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!, value4!);
+            });
 
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!, value15!);
-                });
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5>(
+        this Command command,
+        Action<T1, T2, T3, T4, T5> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!, value4!, value5!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(
-            this Command command,
-            Action<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6>(
+        this Command command,
+        Action<T1, T2, T3, T4, T5, T6> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!, value4!, value5!, value6!);
+            });
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
-                    var value15 = GetValueForHandlerParameter<T15>(symbols, ref index, context);
-                    var value16 = GetValueForHandlerParameter<T16>(symbols, ref index, context);
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
+        this Command command,
+        Action<T1, T2, T3, T4, T5, T6, T7> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
+            });
 
-                    handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!, value15!, value16!);
-                });
-    }
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{T1,T2,T3,T4,T5,T6,T7,T8}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
+        this Command command,
+        Action<T1, T2, T3, T4, T5, T6, T7, T8> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+                var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
+
+                handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
+            });
 }
\ No newline at end of file
diff --git a/src/System.CommandLine/Handler.Func.cs b/src/System.CommandLine/Handler.Func.cs
index 3fbe7bdfda..4650f952c7 100644
--- a/src/System.CommandLine/Handler.Func.cs
+++ b/src/System.CommandLine/Handler.Func.cs
@@ -5,411 +5,182 @@
 using System.CommandLine.Invocation;
 using System.Threading.Tasks;
 
-namespace System.CommandLine
+namespace System.CommandLine;
+
+/// <summary>
+/// Provides methods for creating and working with command handlers.
+/// </summary>
+public static partial class Handler
 {
     /// <summary>
-    /// Provides methods for creating and working with command handlers.
+    /// Sets a command's handler based on a <see cref="Func{Task}"/>.
     /// </summary>
-    public static partial class Handler
-    {
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{Task}"/>.
-        /// </summary>
-        public static void SetHandler(
-            this Command command,
-            Func<Task> handle) =>
-            command.Handler = new AnonymousCommandHandler(_ => handle());
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T>(
-            this Command command,
-            Func<T, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
-
-                    return handle(value1!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2>(
-            this Command command,
-            Func<T1, T2, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-
-                    return handle(value1!, value2!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3>(
-            this Command command,
-            Func<T1, T2, T3, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4>(
-            this Command command,
-            Func<T1, T2, T3, T4, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
+    public static void SetHandler(
+        this Command command,
+        Func<Task> handle) =>
+        command.Handler = new AnonymousCommandHandler(_ => handle());
 
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
-
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!);
-                });
-
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T>(
+        this Command command,
+        Func<T, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
 
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!);
-                });
+                return handle(value1!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2>(
+        this Command command,
+        Func<T1, T2, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
 
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!);
-                });
+                return handle(value1!, value2!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3>(
+        this Command command,
+        Func<T1, T2, T3, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!);
+            });
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
-                    var value15 = GetValueForHandlerParameter<T15>(symbols, ref index, context);
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4>(
+        this Command command,
+        Func<T1, T2, T3, T4, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!, value4!);
+            });
 
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!, value15!);
-                });
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5>(
+        this Command command,
+        Func<T1, T2, T3, T4, T5, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!, value4!, value5!);
+            });
 
-        /// <summary>
-        /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,T9,T10,T11,T12,T13,T14,T15,T16,Task}"/>.
-        /// </summary>
-        public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16>(
-            this Command command,
-            Func<T1, T2, T3, T4, T5, T6, T7, T8, T9, T10, T11, T12, T13, T14, T15, T16, Task> handle,
-            params IValueDescriptor[] symbols) =>
-            command.Handler = new AnonymousCommandHandler(
-                context =>
-                {
-                    var index = 0;
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6>(
+        this Command command,
+        Func<T1, T2, T3, T4, T5, T6, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!, value4!, value5!, value6!);
+            });
 
-                    var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                    var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                    var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                    var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                    var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                    var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                    var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                    var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
-                    var value9 = GetValueForHandlerParameter<T9>(symbols, ref index, context);
-                    var value10 = GetValueForHandlerParameter<T10>(symbols, ref index, context);
-                    var value11 = GetValueForHandlerParameter<T11>(symbols, ref index, context);
-                    var value12 = GetValueForHandlerParameter<T12>(symbols, ref index, context);
-                    var value13 = GetValueForHandlerParameter<T13>(symbols, ref index, context);
-                    var value14 = GetValueForHandlerParameter<T14>(symbols, ref index, context);
-                    var value15 = GetValueForHandlerParameter<T15>(symbols, ref index, context);
-                    var value16 = GetValueForHandlerParameter<T16>(symbols, ref index, context);
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
+        this Command command,
+        Func<T1, T2, T3, T4, T5, T6, T7, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
+            });
 
-                    return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!, value9!, value10!, value11!, value12!, value13!, value14!, value15!, value16!);
-                });
-    }
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{T1,T2,T3,T4,T5,T6,T7,T8,Task}"/>.
+    /// </summary>
+    public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
+        this Command command,
+        Func<T1, T2, T3, T4, T5, T6, T7, T8, Task> handle,
+        params IValueDescriptor[] symbols) =>
+        command.Handler = new AnonymousCommandHandler(
+            context =>
+            {
+                var index = 0;
+
+                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
+                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+                var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
+
+                return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
+            });
 }
\ No newline at end of file

From 5647304fe787edc0bb79ce0ce16094a9e0f043e0 Mon Sep 17 00:00:00 2001
From: Jon Sequeira <jonsequeira@gmail.com>
Date: Wed, 4 May 2022 12:41:01 -0700
Subject: [PATCH 2/4] remove params from SetHandler, make parameter list match
 generic type param arity

---
 ...ommandLine_api_is_not_changed.approved.txt |  39 ++--
 .../ModelBinder.cs                            |  18 +-
 .../SuggestionDispatcher.cs                   |   1 -
 .../Binding/SetHandlerTests.cs                | 212 +-----------------
 .../CommandExtensionsTests.cs                 |   5 +-
 .../Invocation/InvocationPipelineTests.cs     |   4 +-
 .../Binding/BinderBase{T}.cs                  |   8 +-
 src/System.CommandLine/Binding/BoundValue.cs  |  17 --
 .../Binding/IValueSource.cs                   |   2 +-
 .../ValueDescriptorDefaultValueSource.cs      |   5 +-
 src/System.CommandLine/Handler.Action.cs      | 140 +++++++-----
 src/System.CommandLine/Handler.Func.cs        | 141 +++++++-----
 src/System.CommandLine/Handler.cs             |  65 +-----
 .../Help/HelpBuilder.Default.cs               |   2 +-
 src/System.CommandLine/Help/HelpBuilder.cs    |   2 +-
 15 files changed, 224 insertions(+), 437 deletions(-)

diff --git a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
index 7880f226af..6d2b09a310 100644
--- a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
+++ b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
@@ -103,24 +103,30 @@
     public System.Collections.Generic.IEnumerator<System.Collections.Generic.KeyValuePair<System.String,System.Collections.Generic.IEnumerable<System.String>>> GetEnumerator()
     public System.Boolean TryGetValues(System.String name, ref System.Collections.Generic.IReadOnlyList<System.String> values)
   public static class Handler
+    public static System.Void SetHandler(this Command command, System.Action<System.CommandLine.Invocation.InvocationContext> handle)
+    public static System.Void SetHandler(this Command command, System.Action<System.CommandLine.Parsing.ParseResult> handle)
     public static System.Void SetHandler(this Command command, System.Action handle)
     public static System.Void SetHandler(this Command command, System.Func<System.Threading.Tasks.Task> handle)
-    public static System.Void SetHandler<T>(this Command command, Action<T> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2>(this Command command, Action<T1,T2> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3>(this Command command, Action<T1,T2,T3> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4>(this Command command, Action<T1,T2,T3,T4> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5>(this Command command, Action<T1,T2,T3,T4,T5> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Action<T1,T2,T3,T4,T5,T6> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T>(this Command command, Func<T,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2>(this Command command, Func<T1,T2,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3>(this Command command, Func<T1,T2,T3,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4>(this Command command, Func<T1,T2,T3,T4,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5>(this Command command, Func<T1,T2,T3,T4,T5,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Func<T1,T2,T3,T4,T5,T6,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
-    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,System.Threading.Tasks.Task> handle, System.CommandLine.Binding.IValueDescriptor[] symbols)
+    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.Tasks.Task> handle)
+    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.Tasks.Task<System.Int32>> handle)
+    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Parsing.ParseResult,System.Threading.Tasks.Task> handle)
+    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Parsing.ParseResult,System.Threading.Tasks.Task<System.Int32>> handle)
+    public static System.Void SetHandler<T>(this Command command, Action<T> handle, IValueDescriptor<T> symbol)
+    public static System.Void SetHandler<T>(this Command command, Func<T,System.Threading.Tasks.Task> handle, IValueDescriptor<T> symbol)
+    public static System.Void SetHandler<T1, T2>(this Command command, Action<T1,T2> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2)
+    public static System.Void SetHandler<T1, T2>(this Command command, Func<T1,T2,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2)
+    public static System.Void SetHandler<T1, T2, T3>(this Command command, Action<T1,T2,T3> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3)
+    public static System.Void SetHandler<T1, T2, T3>(this Command command, Func<T1,T2,T3,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3)
+    public static System.Void SetHandler<T1, T2, T3, T4>(this Command command, Action<T1,T2,T3,T4> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4)
+    public static System.Void SetHandler<T1, T2, T3, T4>(this Command command, Func<T1,T2,T3,T4,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5>(this Command command, Action<T1,T2,T3,T4,T5> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5>(this Command command, Func<T1,T2,T3,T4,T5,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Action<T1,T2,T3,T4,T5,T6> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6>(this Command command, Func<T1,T2,T3,T4,T5,T6,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6, IValueDescriptor<T7> symbol7)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6, IValueDescriptor<T7> symbol7)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Action<T1,T2,T3,T4,T5,T6,T7,T8> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6, IValueDescriptor<T7> symbol7, IValueDescriptor<T8> symbol8)
+    public static System.Void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(this Command command, Func<T1,T2,T3,T4,T5,T6,T7,T8,System.Threading.Tasks.Task> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2, IValueDescriptor<T3> symbol3, IValueDescriptor<T4> symbol4, IValueDescriptor<T5> symbol5, IValueDescriptor<T6> symbol6, IValueDescriptor<T7> symbol7, IValueDescriptor<T8> symbol8)
   public interface IConsole : System.CommandLine.IO.IStandardError, System.CommandLine.IO.IStandardIn, System.CommandLine.IO.IStandardOut
   public abstract class IdentifierSymbol : Symbol, System.CommandLine.Completions.ICompletionSource
     public System.Collections.Generic.IReadOnlyCollection<System.String> Aliases { get; }
@@ -218,7 +224,6 @@ System.CommandLine.Binding
     public System.Void AddService<T>(Func<System.IServiceProvider,T> factory)
     public System.Object GetService(System.Type serviceType)
   public struct BoundValue : System.ValueType
-    public static BoundValue DefaultForValueDescriptor(IValueDescriptor valueDescriptor)
     public System.Object Value { get; }
     public IValueDescriptor ValueDescriptor { get; }
     public IValueSource ValueSource { get; }
diff --git a/src/System.CommandLine.NamingConventionBinder/ModelBinder.cs b/src/System.CommandLine.NamingConventionBinder/ModelBinder.cs
index 9839a997c4..56885c878a 100644
--- a/src/System.CommandLine.NamingConventionBinder/ModelBinder.cs
+++ b/src/System.CommandLine.NamingConventionBinder/ModelBinder.cs
@@ -287,7 +287,7 @@ internal static (BoundValue? boundValue, bool usedNonDefault) GetBoundValue(
         {
             if (valueDescriptor.HasDefaultValue)
             {
-                return (BoundValue.DefaultForValueDescriptor(valueDescriptor), false);
+                return (DefaultForValueDescriptor(valueDescriptor, bindingContext), false);
             }
 
             if (valueDescriptor.ValueType != parentType) // Recursive models aren't allowed
@@ -312,12 +312,26 @@ internal static (BoundValue? boundValue, bool usedNonDefault) GetBoundValue(
                 return (new BoundValue(parameterDescriptor.GetDefaultValue(), valueDescriptor, valueSource), false);
             }
 
-            return (BoundValue.DefaultForValueDescriptor(valueDescriptor), false);
+            return (DefaultForValueDescriptor(valueDescriptor, bindingContext), false);
         }
 
         return (null, false);
     }
 
+    private static BoundValue DefaultForValueDescriptor(
+        IValueDescriptor valueDescriptor,
+        BindingContext context)
+    {
+        var valueSource = ValueDescriptorDefaultValueSource.Instance;
+
+        valueSource.TryGetValue(valueDescriptor, context, out var value);
+
+        return new BoundValue(
+            value,
+            valueDescriptor,
+            valueSource);
+    }
+
     private protected IValueDescriptor FindModelPropertyDescriptor(Type propertyType, string propertyName)
     {
         return ModelDescriptor.PropertyDescriptors
diff --git a/src/System.CommandLine.Suggest/SuggestionDispatcher.cs b/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
index 242cff0fbf..4bb477991d 100644
--- a/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
+++ b/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
@@ -35,7 +35,6 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
             CompleteScriptCommand.SetHandler((InvocationContext context) =>
             {
                 SuggestionShellScriptHandler.Handle(context.Console, context.ParseResult.GetValueForArgument(shellTypeArgument));
-                return Task.FromResult(0);
             });
 
             ListCommand = new Command("list")
diff --git a/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs b/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
index 92387beb79..04c0c35b3e 100644
--- a/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
+++ b/src/System.CommandLine.Tests/Binding/SetHandlerTests.cs
@@ -9,214 +9,11 @@
 using System.Threading.Tasks;
 using FluentAssertions;
 using Xunit;
-using static System.Environment;
 
 namespace System.CommandLine.Tests.Binding
 {
     public class SetHandlerTests
     {
-        [Theory]
-        [InlineData(1)]
-        [InlineData(2)]
-        [InlineData(3)]
-        public void Instances_from_service_provider_can_be_injected_at_any_position_relative_to_symbol_parameters_with_Action_overloads(int @case)
-        {
-            var option = new Option<bool>("-o");
-            var argument = new Argument<string>("value");
-
-            var command = new RootCommand
-            {
-                option,
-                argument
-            };
-
-            ParseResult boundParseResult = default;
-            bool boundBoolValue = default;
-            string boundStringValue = default;
-            switch (@case)
-            {
-                case 1:
-                    command.SetHandler((ParseResult parseResult, bool boolValue, string stringValue) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                    }, option, argument);
-                    break;
-                case 2:
-                    command.SetHandler((bool boolValue, ParseResult parseResult, string stringValue) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                    }, option, argument);
-                    break;
-                case 3:
-                    command.SetHandler((bool boolValue, string stringValue, ParseResult parseResult) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                    }, option, argument);
-                    break;
-            }
-
-            command.Invoke("-o hi");
-
-            boundParseResult.Should().NotBeNull();
-            boundBoolValue.Should().BeTrue();
-            boundStringValue.Should().Be("hi");
-        }
-
-        [Theory]
-        [InlineData(1)]
-        [InlineData(2)]
-        [InlineData(3)]
-        public void Instances_from_service_provider_can_be_injected_at_any_position_relative_to_symbol_parameters_with_Func_overloads(int @case)
-        {
-            var option = new Option<bool>("-o");
-            var argument = new Argument<string>("value");
-
-            var command = new RootCommand
-            {
-                option,
-                argument
-            };
-
-            ParseResult boundParseResult = default;
-            bool boundBoolValue = default;
-            string boundStringValue = default;
-            switch (@case)
-            {
-                case 1:
-                    command.SetHandler((ParseResult parseResult, bool boolValue, string stringValue) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                        return Task.FromResult(123);
-                    }, option, argument);
-                    break;
-                case 2:
-                    command.SetHandler((bool boolValue, ParseResult parseResult, string stringValue) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                        return Task.FromResult(123);
-                    }, option, argument);
-                    break;
-                case 3:
-                    command.SetHandler((bool boolValue, string stringValue, ParseResult parseResult) =>
-                    {
-                        boundParseResult = parseResult;
-                        boundBoolValue = boolValue;
-                        boundStringValue = stringValue;
-                        return Task.FromResult(123);
-                    }, option, argument);
-                    break;
-            }
-
-            command.Invoke("-o hi");
-
-            boundParseResult.Should().NotBeNull();
-            boundBoolValue.Should().BeTrue();
-            boundStringValue.Should().Be("hi");
-        }
-
-        [Fact]
-        public void If_parameter_order_does_not_match_symbol_order_then_an_error_results()
-        {
-            var boolOption = new Option<bool>("-o");
-            var stringArg = new Argument<string>("value");
-
-            var command = new RootCommand
-            {
-                boolOption,
-                stringArg
-            };
-
-            var wasCalled = false;
-
-            command.SetHandler((bool boolValue, string stringValue) => wasCalled = true, 
-                                                    stringArg, boolOption);
-
-            var exitCode = command.Invoke("-o hi");
-
-            wasCalled.Should().BeFalse();
-            exitCode.Should().Be(1);
-        }
-
-        [Fact]
-        public void If_service_is_not_found_then_an_error_results()
-        {
-            var command = new RootCommand();
-
-            var wasCalled = false;
-            command.SetHandler((ClassWithMultipleCtor instance) => wasCalled = true);
-
-            var exitCode = command.Invoke("");
-
-            wasCalled.Should().BeFalse();
-            exitCode.Should().Be(1);
-        }
-
-        [Fact]
-        public void If_no_symbol_was_passed_for_binding_then_the_error_message_suggests_a_fix_for_the_first_missing_symbol()
-        {
-            var boolOption = new Option<bool>("-o");
-            var stringArg = new Argument<string>("value");
-
-            var subcommand = new Command("TheCommand")
-            {
-                boolOption,
-                stringArg
-            };
-
-            var command = new RootCommand
-            {
-                subcommand
-            };
-
-            subcommand.SetHandler((bool boolValue, string stringValue) => { });
-
-            var console = new TestConsole();
-
-            command.Invoke("TheCommand -o hi", console);
-
-            console.Error.ToString().Should()
-                   .Contain(
-                       $"The SetHandler call for command 'TheCommand' is missing an Argument or Option for the parameter at position 0. Did you mean to pass one of these?{NewLine}Option<Boolean> -o");
-        }
-
-        [Fact]
-        public void If_no_symbol_was_passed_for_binding_subsequent_parameter_then_the_error_message_suggests_a_fix_for_the_first_missing_symbol()
-        {
-            var boolOption = new Option<bool>("-o");
-            var stringArg = new Argument<string>("value");
-
-            var subcommand = new Command("TheCommand")
-            {
-                boolOption,
-                stringArg
-            };
-
-            var command = new RootCommand
-            {
-                subcommand
-            };
-
-            subcommand.SetHandler((bool boolValue, string stringValue) => { }, boolOption);
-
-            var console = new TestConsole();
-
-            command.Invoke("TheCommand -o hi", console);
-
-            console.Error.ToString().Should()
-                   .Contain(
-                       $"The SetHandler call for command 'TheCommand' is missing an Argument or Option for the parameter at position 1. Did you mean to pass one of these?{NewLine}Argument<String> value");
-        }
-
         [Fact]
         public void Custom_types_can_be_bound()
         {
@@ -342,10 +139,11 @@ public void Binding_is_correct_for_Action_overload_having_arity_(int arity)
             var parameters = new List<object>
             {
                 command,
-                handlerFunc,
-                command.Arguments.ToArray()
+                handlerFunc
             };
 
+            parameters.AddRange(command.Arguments);
+
             setHandler.Invoke(null, parameters.ToArray());
 
             var exitCode = command.Invoke(commandLine);
@@ -433,8 +231,8 @@ public void Binding_is_correct_for_Func_overload_having_arity_(int arity)
             {
                 command,
                 handlerFunc,
-                command.Arguments.ToArray()
             };
+            parameters.AddRange(command.Arguments);
 
             setHandler.Invoke(null, parameters.ToArray());
             
@@ -460,7 +258,7 @@ public async Task Unexpected_return_types_result_in_exit_code_0_if_no_exception_
 
             var command = new Command("wat");
 
-            var handle = (ParseResult _) =>
+            var handle = () =>
             {
                 wasCalled = true;
                 return Task.FromResult(new { NovelType = true });
diff --git a/src/System.CommandLine.Tests/CommandExtensionsTests.cs b/src/System.CommandLine.Tests/CommandExtensionsTests.cs
index d7e52d7c2b..a04d072137 100644
--- a/src/System.CommandLine.Tests/CommandExtensionsTests.cs
+++ b/src/System.CommandLine.Tests/CommandExtensionsTests.cs
@@ -3,6 +3,7 @@
 
 using System.Collections.Generic;
 using System.CommandLine.Builder;
+using System.CommandLine.Invocation;
 using System.CommandLine.IO;
 using System.CommandLine.Parsing;
 using System.Threading.Tasks;
@@ -87,7 +88,7 @@ public void Invoke_extension_method_reuses_implicit_parser_instance()
             List<Parser> parsers = new();
             var command = new Command("x");
 
-            command.SetHandler((ParseResult result) => parsers.Add(result.Parser));
+            command.SetHandler(context => parsers.Add(context.ParseResult.Parser));
 
             command.Invoke("");
             command.Invoke("");
@@ -106,7 +107,7 @@ public void Parse_and_Invoke_extension_methods_use_different_implicit_parsers()
             Parser implicitParserForInvoking = null;
             Parser implicitParserForParsing = null;
 
-            command.SetHandler((ParseResult result) => implicitParserForInvoking = result.Parser);
+            command.SetHandler(context => implicitParserForInvoking = context.ParseResult.Parser);
 
             command.Invoke("");
 
diff --git a/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs b/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
index fb8a7f7249..ea620e8cda 100644
--- a/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
+++ b/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
@@ -249,10 +249,10 @@ public void Synchronous_invocation_can_be_short_circuited_by_async_middleware_by
             var handlerWasCalled = false;
 
             var command = new Command("the-command");
-            command.SetHandler((ParseResult parseResult) =>
+            command.SetHandler(context =>
             {
                 handlerWasCalled = true;
-                parseResult.Errors.Should().BeEmpty();
+                context.ParseResult.Errors.Should().BeEmpty();
                 return Task.FromResult(0);
             });
 
diff --git a/src/System.CommandLine/Binding/BinderBase{T}.cs b/src/System.CommandLine/Binding/BinderBase{T}.cs
index 31dcb1baac..94f034acd3 100644
--- a/src/System.CommandLine/Binding/BinderBase{T}.cs
+++ b/src/System.CommandLine/Binding/BinderBase{T}.cs
@@ -23,14 +23,8 @@ public abstract class BinderBase<T> :
 
     object? IValueDescriptor.GetDefaultValue() => default(T);
 
-    bool IValueSource.TryGetValue(IValueDescriptor valueDescriptor, BindingContext? bindingContext, out object? boundValue)
+    bool IValueSource.TryGetValue(IValueDescriptor valueDescriptor, BindingContext bindingContext, out object? boundValue)
     {
-        if (bindingContext is null)
-        {
-            boundValue = default;
-            return false;
-        }
-
         boundValue = GetBoundValue(bindingContext);
         return true;
     }
diff --git a/src/System.CommandLine/Binding/BoundValue.cs b/src/System.CommandLine/Binding/BoundValue.cs
index ba50a45a4e..1b400b73d2 100644
--- a/src/System.CommandLine/Binding/BoundValue.cs
+++ b/src/System.CommandLine/Binding/BoundValue.cs
@@ -35,22 +35,5 @@ internal BoundValue(
 
         /// <inheritdoc />
         public override string ToString() => $"{ValueDescriptor}: {Value}";
-
-        /// <summary>
-        /// Gets a <see cref="BoundValue"/> representing the default value for a specified <see cref="IValueDescriptor"/>.
-        /// </summary>
-        /// <param name="valueDescriptor">A value descriptor for which to get the default value.</param>
-        /// <returns>A <see cref="BoundValue"/> representing the default value for a specified <see cref="IValueDescriptor"/>.</returns>
-        public static BoundValue DefaultForValueDescriptor(IValueDescriptor valueDescriptor)
-        {
-            var valueSource = ValueDescriptorDefaultValueSource.Instance;
-
-            valueSource.TryGetValue(valueDescriptor, null, out var value);
-
-            return new BoundValue(
-                value,
-                valueDescriptor,
-                valueSource);
-        }
     }
 }
diff --git a/src/System.CommandLine/Binding/IValueSource.cs b/src/System.CommandLine/Binding/IValueSource.cs
index 6233493947..48d50413c5 100644
--- a/src/System.CommandLine/Binding/IValueSource.cs
+++ b/src/System.CommandLine/Binding/IValueSource.cs
@@ -17,7 +17,7 @@ public interface IValueSource
         /// <returns><see langword="true"/> if a matching value was found; otherwise, <see langword="false"/>.</returns>
         bool TryGetValue(
             IValueDescriptor valueDescriptor,
-            BindingContext? bindingContext,
+            BindingContext bindingContext,
             out object? boundValue);
     }
 }
diff --git a/src/System.CommandLine/Binding/ValueDescriptorDefaultValueSource.cs b/src/System.CommandLine/Binding/ValueDescriptorDefaultValueSource.cs
index ce72ebd6c0..0fc367198b 100644
--- a/src/System.CommandLine/Binding/ValueDescriptorDefaultValueSource.cs
+++ b/src/System.CommandLine/Binding/ValueDescriptorDefaultValueSource.cs
@@ -11,7 +11,10 @@ private ValueDescriptorDefaultValueSource()
         {
         }
 
-        public bool TryGetValue(IValueDescriptor valueDescriptor, BindingContext? bindingContext, out object? boundValue)
+        public bool TryGetValue(
+            IValueDescriptor valueDescriptor, 
+            BindingContext bindingContext, 
+            out object? boundValue)
         {
             boundValue = valueDescriptor.GetDefaultValue();
             return true;
diff --git a/src/System.CommandLine/Handler.Action.cs b/src/System.CommandLine/Handler.Action.cs
index 4dc80406f7..ed7039beb0 100644
--- a/src/System.CommandLine/Handler.Action.cs
+++ b/src/System.CommandLine/Handler.Action.cs
@@ -11,6 +11,14 @@ namespace System.CommandLine;
 /// </summary>
 public static partial class Handler
 {
+    /// <summary>
+    /// Sets a command's handler based on an <see cref="Action{InvocationContext}"/>.
+    /// </summary>
+    public static void SetHandler(
+        this Command command,
+        Action<InvocationContext> handle) =>
+        command.Handler = new AnonymousCommandHandler(handle);
+
     /// <summary>
     /// Sets a command's handler based on an <see cref="Action"/>.
     /// </summary>
@@ -25,13 +33,11 @@ public static void SetHandler(
     public static void SetHandler<T>(
         this Command command,
         Action<T> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T> symbol) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol, context);
 
                 handle(value1!);
             });
@@ -42,14 +48,13 @@ public static void SetHandler<T>(
     public static void SetHandler<T1, T2>(
         this Command command,
         Action<T1, T2> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
 
                 handle(value1!, value2!);
             });
@@ -60,15 +65,15 @@ public static void SetHandler<T1, T2>(
     public static void SetHandler<T1, T2, T3>(
         this Command command,
         Action<T1, T2, T3> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
 
                 handle(value1!, value2!, value3!);
             });
@@ -79,16 +84,17 @@ public static void SetHandler<T1, T2, T3>(
     public static void SetHandler<T1, T2, T3, T4>(
         this Command command,
         Action<T1, T2, T3, T4> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
 
                 handle(value1!, value2!, value3!, value4!);
             });
@@ -99,17 +105,19 @@ public static void SetHandler<T1, T2, T3, T4>(
     public static void SetHandler<T1, T2, T3, T4, T5>(
         this Command command,
         Action<T1, T2, T3, T4, T5> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
 
                 handle(value1!, value2!, value3!, value4!, value5!);
             });
@@ -120,18 +128,21 @@ public static void SetHandler<T1, T2, T3, T4, T5>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6>(
         this Command command,
         Action<T1, T2, T3, T4, T5, T6> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
 
                 handle(value1!, value2!, value3!, value4!, value5!, value6!);
             });
@@ -142,19 +153,23 @@ public static void SetHandler<T1, T2, T3, T4, T5, T6>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
         this Command command,
         Action<T1, T2, T3, T4, T5, T6, T7> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6,
+        IValueDescriptor<T7> symbol7) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
+                var value7 = GetValueForHandlerParameter(symbol7, context);
 
                 handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
             });
@@ -165,20 +180,25 @@ public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
         this Command command,
         Action<T1, T2, T3, T4, T5, T6, T7, T8> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6,
+        IValueDescriptor<T7> symbol7,
+        IValueDescriptor<T8> symbol8) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
+                var value7 = GetValueForHandlerParameter(symbol7, context);
+                var value8 = GetValueForHandlerParameter(symbol8, context);
 
                 handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
             });
diff --git a/src/System.CommandLine/Handler.Func.cs b/src/System.CommandLine/Handler.Func.cs
index 4650f952c7..3ebcce4bdd 100644
--- a/src/System.CommandLine/Handler.Func.cs
+++ b/src/System.CommandLine/Handler.Func.cs
@@ -3,6 +3,7 @@
 
 using System.CommandLine.Binding;
 using System.CommandLine.Invocation;
+using System.CommandLine.Parsing;
 using System.Threading.Tasks;
 
 namespace System.CommandLine;
@@ -20,19 +21,25 @@ public static void SetHandler(
         Func<Task> handle) =>
         command.Handler = new AnonymousCommandHandler(_ => handle());
 
+    /// <summary>
+    /// Sets a command's handler based on a <see cref="Func{Task,InvocationContext}"/>.
+    /// </summary>
+    public static void SetHandler(
+        this Command command,
+        Func<InvocationContext, Task> handle) =>
+        command.Handler = new AnonymousCommandHandler(handle);
+    
     /// <summary>
     /// Sets a command's handler based on a <see cref="Func{T,Task}"/>.
     /// </summary>
     public static void SetHandler<T>(
         this Command command,
         Func<T, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T> symbol) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol, context);
 
                 return handle(value1!);
             });
@@ -43,14 +50,13 @@ public static void SetHandler<T>(
     public static void SetHandler<T1, T2>(
         this Command command,
         Func<T1, T2, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
 
                 return handle(value1!, value2!);
             });
@@ -61,15 +67,15 @@ public static void SetHandler<T1, T2>(
     public static void SetHandler<T1, T2, T3>(
         this Command command,
         Func<T1, T2, T3, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
 
                 return handle(value1!, value2!, value3!);
             });
@@ -80,16 +86,17 @@ public static void SetHandler<T1, T2, T3>(
     public static void SetHandler<T1, T2, T3, T4>(
         this Command command,
         Func<T1, T2, T3, T4, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
 
                 return handle(value1!, value2!, value3!, value4!);
             });
@@ -100,17 +107,19 @@ public static void SetHandler<T1, T2, T3, T4>(
     public static void SetHandler<T1, T2, T3, T4, T5>(
         this Command command,
         Func<T1, T2, T3, T4, T5, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
 
                 return handle(value1!, value2!, value3!, value4!, value5!);
             });
@@ -121,18 +130,21 @@ public static void SetHandler<T1, T2, T3, T4, T5>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6>(
         this Command command,
         Func<T1, T2, T3, T4, T5, T6, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
 
                 return handle(value1!, value2!, value3!, value4!, value5!, value6!);
             });
@@ -143,19 +155,23 @@ public static void SetHandler<T1, T2, T3, T4, T5, T6>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
         this Command command,
         Func<T1, T2, T3, T4, T5, T6, T7, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6,
+        IValueDescriptor<T7> symbol7) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
+                var value7 = GetValueForHandlerParameter(symbol7, context);
 
                 return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!);
             });
@@ -166,20 +182,25 @@ public static void SetHandler<T1, T2, T3, T4, T5, T6, T7>(
     public static void SetHandler<T1, T2, T3, T4, T5, T6, T7, T8>(
         this Command command,
         Func<T1, T2, T3, T4, T5, T6, T7, T8, Task> handle,
-        params IValueDescriptor[] symbols) =>
+        IValueDescriptor<T1> symbol1,
+        IValueDescriptor<T2> symbol2,
+        IValueDescriptor<T3> symbol3,
+        IValueDescriptor<T4> symbol4,
+        IValueDescriptor<T5> symbol5,
+        IValueDescriptor<T6> symbol6,
+        IValueDescriptor<T7> symbol7,
+        IValueDescriptor<T8> symbol8) =>
         command.Handler = new AnonymousCommandHandler(
             context =>
             {
-                var index = 0;
-
-                var value1 = GetValueForHandlerParameter<T1>(symbols, ref index, context);
-                var value2 = GetValueForHandlerParameter<T2>(symbols, ref index, context);
-                var value3 = GetValueForHandlerParameter<T3>(symbols, ref index, context);
-                var value4 = GetValueForHandlerParameter<T4>(symbols, ref index, context);
-                var value5 = GetValueForHandlerParameter<T5>(symbols, ref index, context);
-                var value6 = GetValueForHandlerParameter<T6>(symbols, ref index, context);
-                var value7 = GetValueForHandlerParameter<T7>(symbols, ref index, context);
-                var value8 = GetValueForHandlerParameter<T8>(symbols, ref index, context);
+                var value1 = GetValueForHandlerParameter(symbol1, context);
+                var value2 = GetValueForHandlerParameter(symbol2, context);
+                var value3 = GetValueForHandlerParameter(symbol3, context);
+                var value4 = GetValueForHandlerParameter(symbol4, context);
+                var value5 = GetValueForHandlerParameter(symbol5, context);
+                var value6 = GetValueForHandlerParameter(symbol6, context);
+                var value7 = GetValueForHandlerParameter(symbol7, context);
+                var value8 = GetValueForHandlerParameter(symbol8, context);
 
                 return handle(value1!, value2!, value3!, value4!, value5!, value6!, value7!, value8!);
             });
diff --git a/src/System.CommandLine/Handler.cs b/src/System.CommandLine/Handler.cs
index 3b2a6211dc..a60a41d361 100644
--- a/src/System.CommandLine/Handler.cs
+++ b/src/System.CommandLine/Handler.cs
@@ -3,75 +3,24 @@
 
 using System.CommandLine.Binding;
 using System.CommandLine.Invocation;
-using System.CommandLine.Parsing;
-using System.Linq;
-using static System.Environment;
 
 namespace System.CommandLine;
 
 public static partial class Handler
 {
     private static T? GetValueForHandlerParameter<T>(
-        IValueDescriptor[] symbols,
-        ref int index,
+        IValueDescriptor<T> symbol,
         InvocationContext context)
     {
-        if (symbols.Length > index &&
-            symbols[index] is IValueDescriptor<T> symbol)
+        if (symbol is IValueSource valueSource &&
+            valueSource.TryGetValue(symbol, context.BindingContext, out var boundValue) &&
+            boundValue is T value)
         {
-            index++;
-
-            if (symbol is IValueSource valueSource &&
-                valueSource.TryGetValue(symbol, context.BindingContext, out var boundValue) &&
-                boundValue is T value)
-            {
-                return value;
-            }
-            else
-            {
-                return context.ParseResult.GetValueFor(symbol);
-            }
+            return value;
         }
-
-        return GetService<T>(ref index, context); // kept in separate method to avoid jitting rare code path
-    }
-
-    private static T? GetService<T>(ref int index, InvocationContext context)
-    {
-        var service = context.BindingContext.GetService(typeof(T));
-
-        if (service is null)
+        else
         {
-            var candidates = context.ParseResult
-                                    .RootCommandResult
-                                    .AllSymbolResults()
-                                    .Where(r => r.Symbol.Parents.All(p => p is not Option))
-                                    .Select(r => r.Symbol)
-                                    .OfType<IValueDescriptor>()
-                                    .ToArray();
-
-            if (candidates.Any())
-            {
-                var candidatesDescription = string.Join(
-                    NewLine,
-                    candidates
-                        .Where(c => typeof(T).IsAssignableFrom(c.ValueType))
-                        .Select(c => c switch
-                        {
-                            Argument<T> argument => $"{nameof(Argument)}<{argument.ValueType.Name}> {argument.Name}",
-                            Argument argument => $"{nameof(Argument)} {argument.Name}",
-                            Option<T> option => $"{nameof(Option)}<{option.ValueType.Name}> {option.Aliases.First()}",
-                            Option option => $"{nameof(Option)} {option.Aliases.First()}",
-                            _ => throw new ArgumentOutOfRangeException(nameof(c))
-                        }));
-
-                throw new ArgumentException(
-                    $"The {nameof(SetHandler)} call for command '{context.ParseResult.CommandResult.Command.Name}' is missing an {nameof(Argument)} or {nameof(Option)} for the parameter at position {index}. Did you mean to pass one of these?{NewLine}{candidatesDescription}");
-            }
-
-            throw new ArgumentException($"Service not found for type {typeof(T)}.");
+            return context.ParseResult.GetValueFor(symbol);
         }
-
-        return (T)service;
     }
 }
\ No newline at end of file
diff --git a/src/System.CommandLine/Help/HelpBuilder.Default.cs b/src/System.CommandLine/Help/HelpBuilder.Default.cs
index 61c32af136..67f19f5d84 100644
--- a/src/System.CommandLine/Help/HelpBuilder.Default.cs
+++ b/src/System.CommandLine/Help/HelpBuilder.Default.cs
@@ -219,7 +219,7 @@ public static HelpSectionDelegate OptionsSection() =>
                     {
                         if ((parentCommand = parent.Symbol as Command) is not null)
                         {
-                            foreach (Option option in parentCommand.Options)
+                            foreach (var option in parentCommand.Options)
                             {
                                 // global help aliases may be duplicated, we just ignore them
                                 if (option.IsGlobal && !option.IsHidden && uniqueOptions.Add(option))
diff --git a/src/System.CommandLine/Help/HelpBuilder.cs b/src/System.CommandLine/Help/HelpBuilder.cs
index d4d5cd41da..4eb16a21ca 100644
--- a/src/System.CommandLine/Help/HelpBuilder.cs
+++ b/src/System.CommandLine/Help/HelpBuilder.cs
@@ -121,7 +121,7 @@ IEnumerable<string> GetUsageParts()
                         .RecurseWhileNotNull(c => c.Parents.OfType<Command>().FirstOrDefault())
                         .Reverse();
 
-                foreach (Command parentCommand in parentCommands)
+                foreach (var parentCommand in parentCommands)
                 {
                     if (!displayOptionTitle)
                     {

From 745940030ce120a942c944d7923f1a3b19168621 Mon Sep 17 00:00:00 2001
From: Jon Sequeira <jonsequeira@gmail.com>
Date: Wed, 4 May 2022 12:58:33 -0700
Subject: [PATCH 3/4] cleanup, update approvals

---
 ...sts.System_CommandLine_api_is_not_changed.approved.txt | 4 ----
 .../TerminalModeTests.cs                                  | 2 +-
 src/System.CommandLine.Suggest/SuggestionDispatcher.cs    | 8 ++++----
 .../Invocation/CancelOnProcessTerminationTests.cs         | 3 +--
 .../Invocation/InvocationExtensionsTests.cs               | 5 ++---
 .../Invocation/InvocationPipelineTests.cs                 | 8 ++++----
 src/System.CommandLine/Handler.Func.cs                    | 1 -
 7 files changed, 12 insertions(+), 19 deletions(-)

diff --git a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
index 6d2b09a310..35bddbdbe2 100644
--- a/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
+++ b/src/System.CommandLine.ApiCompatibility.Tests/ApiCompatibilityApprovalTests.System_CommandLine_api_is_not_changed.approved.txt
@@ -104,13 +104,9 @@
     public System.Boolean TryGetValues(System.String name, ref System.Collections.Generic.IReadOnlyList<System.String> values)
   public static class Handler
     public static System.Void SetHandler(this Command command, System.Action<System.CommandLine.Invocation.InvocationContext> handle)
-    public static System.Void SetHandler(this Command command, System.Action<System.CommandLine.Parsing.ParseResult> handle)
     public static System.Void SetHandler(this Command command, System.Action handle)
     public static System.Void SetHandler(this Command command, System.Func<System.Threading.Tasks.Task> handle)
     public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.Tasks.Task> handle)
-    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Invocation.InvocationContext,System.Threading.Tasks.Task<System.Int32>> handle)
-    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Parsing.ParseResult,System.Threading.Tasks.Task> handle)
-    public static System.Void SetHandler(this Command command, System.Func<System.CommandLine.Parsing.ParseResult,System.Threading.Tasks.Task<System.Int32>> handle)
     public static System.Void SetHandler<T>(this Command command, Action<T> handle, IValueDescriptor<T> symbol)
     public static System.Void SetHandler<T>(this Command command, Func<T,System.Threading.Tasks.Task> handle, IValueDescriptor<T> symbol)
     public static System.Void SetHandler<T1, T2>(this Command command, Action<T1,T2> handle, IValueDescriptor<T1> symbol1, IValueDescriptor<T2> symbol2)
diff --git a/src/System.CommandLine.Rendering.Tests/TerminalModeTests.cs b/src/System.CommandLine.Rendering.Tests/TerminalModeTests.cs
index 74cb6d3d71..f4a81ef22d 100644
--- a/src/System.CommandLine.Rendering.Tests/TerminalModeTests.cs
+++ b/src/System.CommandLine.Rendering.Tests/TerminalModeTests.cs
@@ -44,7 +44,7 @@ public async Task Sets_output_mode_to_Ansi_when_specified_by_output_directive(Ou
             OutputMode detectedOutputMode = OutputMode.Auto;
 
             var command = new Command("hello");
-            command.SetHandler((InvocationContext ctx) =>
+            command.SetHandler(ctx =>
             {
                 detectedOutputMode = ctx.Console.DetectOutputMode();
                 return Task.FromResult(0);
diff --git a/src/System.CommandLine.Suggest/SuggestionDispatcher.cs b/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
index 4bb477991d..a048320e48 100644
--- a/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
+++ b/src/System.CommandLine.Suggest/SuggestionDispatcher.cs
@@ -32,7 +32,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
             {
                 shellTypeArgument
             };
-            CompleteScriptCommand.SetHandler((InvocationContext context) =>
+            CompleteScriptCommand.SetHandler(context =>
             {
                 SuggestionShellScriptHandler.Handle(context.Console, context.ParseResult.GetValueForArgument(shellTypeArgument));
             });
@@ -41,7 +41,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
             {
                 Description = "Lists apps registered for suggestions",
             };
-            ListCommand.SetHandler((InvocationContext ctx) =>
+            ListCommand.SetHandler(ctx =>
             {
                 ctx.Console.Out.WriteLine(ShellPrefixesToMatch(_suggestionRegistration));
                 return Task.FromResult(0);
@@ -52,7 +52,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
                 ExecutableOption,
                 PositionOption
             };
-            GetCommand.SetHandler((InvocationContext context) => Get(context));
+            GetCommand.SetHandler(context => Get(context));
 
             var commandPathOption = new Option<string>("--command-path", "The path to the command for which to register suggestions");
 
@@ -62,7 +62,7 @@ public SuggestionDispatcher(ISuggestionRegistration suggestionRegistration, ISug
                 new Option<string>("--suggestion-command", "The command to invoke to retrieve suggestions")
             };
 
-            RegisterCommand.SetHandler((InvocationContext context) =>
+            RegisterCommand.SetHandler(context =>
             {
                 Register(context.ParseResult.GetValueForOption(commandPathOption), context.Console);
                 return Task.FromResult(0);
diff --git a/src/System.CommandLine.Tests/Invocation/CancelOnProcessTerminationTests.cs b/src/System.CommandLine.Tests/Invocation/CancelOnProcessTerminationTests.cs
index cac6f5fb92..ef54677dde 100644
--- a/src/System.CommandLine.Tests/Invocation/CancelOnProcessTerminationTests.cs
+++ b/src/System.CommandLine.Tests/Invocation/CancelOnProcessTerminationTests.cs
@@ -7,7 +7,6 @@
 using System.CommandLine.Tests.Utility;
 using System.Diagnostics;
 using System.Runtime.InteropServices;
-using System.Threading;
 using System.Threading.Tasks;
 using FluentAssertions;
 using Xunit;
@@ -32,7 +31,7 @@ public async Task CancelOnProcessTermination_cancels_on_process_termination(int
             {
                 var command = new Command("the-command");
             
-                command.SetHandler(async (InvocationContext context) =>
+                command.SetHandler(async context =>
                 {
                     var cancellationToken = context.GetCancellationToken();
 
diff --git a/src/System.CommandLine.Tests/Invocation/InvocationExtensionsTests.cs b/src/System.CommandLine.Tests/Invocation/InvocationExtensionsTests.cs
index 24ce8dbbe1..947f94a7c3 100644
--- a/src/System.CommandLine.Tests/Invocation/InvocationExtensionsTests.cs
+++ b/src/System.CommandLine.Tests/Invocation/InvocationExtensionsTests.cs
@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation and contributors. All rights reserved.
 // Licensed under the MIT license. See LICENSE file in the project root for full license information.
 
-using System.CommandLine.Invocation;
 using System.CommandLine.IO;
 using System.Threading.Tasks;
 using FluentAssertions;
@@ -124,7 +123,7 @@ public async Task RootCommand_InvokeAsync_can_set_custom_result_code()
         {
             var rootCommand = new RootCommand();
 
-            rootCommand.SetHandler((InvocationContext context) =>
+            rootCommand.SetHandler(context =>
             {
                 context.ExitCode = 123;
                 return Task.CompletedTask;
@@ -140,7 +139,7 @@ public void RootCommand_Invoke_can_set_custom_result_code()
         {
             var rootCommand = new RootCommand();
 
-            rootCommand.SetHandler((InvocationContext context) =>
+            rootCommand.SetHandler(context =>
             {
                 context.ExitCode = 123;
                 return Task.CompletedTask;
diff --git a/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs b/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
index ea620e8cda..33051dd747 100644
--- a/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
+++ b/src/System.CommandLine.Tests/Invocation/InvocationPipelineTests.cs
@@ -182,7 +182,7 @@ public async Task ParseResult_can_be_replaced_by_middleware()
             var command = new Command("the-command");
             var implicitInnerCommand = new Command("implicit-inner-command");
             command.AddCommand(implicitInnerCommand);
-            implicitInnerCommand.SetHandler((InvocationContext context) =>
+            implicitInnerCommand.SetHandler(context =>
             {
                 wasCalled = true;
                 context.ParseResult.Errors.Should().BeEmpty();
@@ -218,7 +218,7 @@ public async Task Invocation_can_be_short_circuited_by_middleware_by_not_calling
             var handlerWasCalled = false;
 
             var command = new Command("the-command");
-            command.SetHandler((InvocationContext context) =>
+            command.SetHandler(context =>
             {
                 handlerWasCalled = true;
                 context.ParseResult.Errors.Should().BeEmpty();
@@ -279,7 +279,7 @@ public async Task When_no_help_builder_is_specified_it_uses_default_implementati
             bool handlerWasCalled = false;
 
             var command = new Command("help-command");
-            command.SetHandler((InvocationContext context) =>
+            command.SetHandler(context =>
             {
                 handlerWasCalled = true;
                 context.HelpBuilder.Should().NotBeNull();
@@ -306,7 +306,7 @@ public async Task When_help_builder_factory_is_specified_it_is_used_to_create_th
             HelpBuilder createdHelpBuilder = null;
 
             var command = new Command("help-command");
-            command.SetHandler((InvocationContext context) =>
+            command.SetHandler(context =>
             {
                 handlerWasCalled = true;
                 context.HelpBuilder.Should().Be(createdHelpBuilder);
diff --git a/src/System.CommandLine/Handler.Func.cs b/src/System.CommandLine/Handler.Func.cs
index 3ebcce4bdd..97f3a9f1e4 100644
--- a/src/System.CommandLine/Handler.Func.cs
+++ b/src/System.CommandLine/Handler.Func.cs
@@ -3,7 +3,6 @@
 
 using System.CommandLine.Binding;
 using System.CommandLine.Invocation;
-using System.CommandLine.Parsing;
 using System.Threading.Tasks;
 
 namespace System.CommandLine;

From 69d0d302481dc413e0c0afbf50c8157dbef78d89 Mon Sep 17 00:00:00 2001
From: Jon Sequeira <jonsequeira@gmail.com>
Date: Wed, 4 May 2022 14:57:41 -0700
Subject: [PATCH 4/4] update trimming and NativeAOT test code

---
 src/System.CommandLine.Tests/CompilationTests.cs  |  1 +
 .../TestApps/NativeAOT/Program.cs                 | 15 ++++++++-------
 .../TestApps/Trimming/Program.cs                  | 10 +++++-----
 3 files changed, 14 insertions(+), 12 deletions(-)

diff --git a/src/System.CommandLine.Tests/CompilationTests.cs b/src/System.CommandLine.Tests/CompilationTests.cs
index d7072a3a92..2694e94e0a 100644
--- a/src/System.CommandLine.Tests/CompilationTests.cs
+++ b/src/System.CommandLine.Tests/CompilationTests.cs
@@ -71,6 +71,7 @@ private void PublishAndValidate(string appName, string warningText, string addit
             },
             workingDirectory);
 
+        stdOut.ToString().Should().NotContain(": error CS");
         stdOut.ToString().Should().NotContain(warningText);
         stdErr.ToString().Should().BeEmpty();
         exitCode.Should().Be(0);
diff --git a/src/System.CommandLine.Tests/TestApps/NativeAOT/Program.cs b/src/System.CommandLine.Tests/TestApps/NativeAOT/Program.cs
index 46c967ac00..ca773abbde 100644
--- a/src/System.CommandLine.Tests/TestApps/NativeAOT/Program.cs
+++ b/src/System.CommandLine.Tests/TestApps/NativeAOT/Program.cs
@@ -1,16 +1,11 @@
 using System;
 using System.CommandLine;
 using System.CommandLine.Builder;
+using System.CommandLine.Invocation;
 using System.CommandLine.Parsing;
 
 public class Program
 {
-    static void Run(bool boolean, string text)
-    {
-        Console.WriteLine($"Bool option: {text}");
-        Console.WriteLine($"String option: {boolean}");
-    }
-
     private static int Main(string[] args)
     {
         Option<bool> boolOption = new Option<bool>(new[] { "--bool", "-b" }, "Bool option");
@@ -22,8 +17,14 @@ private static int Main(string[] args)
             stringOption
         };
 
-        command.SetHandler<bool, string>(Run, boolOption, stringOption);
+        command.SetHandler(Run);
 
         return new CommandLineBuilder(command).Build().Invoke(args);
+
+        void Run(InvocationContext context)
+        {
+            context.Console.WriteLine($"Bool option: {context.ParseResult.GetValueForOption(boolOption)}");
+            context.Console.WriteLine($"String option: {context.ParseResult.GetValueForOption(stringOption)}");
+        }
     }
 }
\ No newline at end of file
diff --git a/src/System.CommandLine.Tests/TestApps/Trimming/Program.cs b/src/System.CommandLine.Tests/TestApps/Trimming/Program.cs
index dab823ff86..f81e9d0ec7 100644
--- a/src/System.CommandLine.Tests/TestApps/Trimming/Program.cs
+++ b/src/System.CommandLine.Tests/TestApps/Trimming/Program.cs
@@ -1,16 +1,16 @@
 using System.CommandLine;
 using System.CommandLine.Invocation;
 
-var fileOption = new Argument<FileInfo>().LegalFileNamesOnly();
+var fileArgument = new Argument<FileInfo>().LegalFileNamesOnly();
 
 var command = new RootCommand
 {
-    fileOption
+    fileArgument
 };
 
-command.SetHandler((FileInfo file, InvocationContext ctx) =>
+command.SetHandler(context =>
 {
-    ctx.Console.Write($"The file you chose was: {file}");
-}, fileOption);
+    context.Console.Write($"The file you chose was: {context.ParseResult.GetValueForArgument(fileArgument)}");
+});
 
 command.Invoke(args);