Add support for VB.NET cached delegate initialization with closures

[ElektroKill]

Link to issue(s) this covers:
#2199

Problem

The CachedDelegateInitialization transform did not fully support VB cached delegate initialization. The pattern emitted when an anonymous function uses a local from a display class/closure was not supported. This can be seen by decompiling Class5.method_0() from the sample provided in the aforementioned issue report. This can be seen in the code inside the first try region.

Before:

private void method_0(ClassHttpRequest classHttpRequest_0, string string_0)
{
	string text = "";
	if (!bool_1)
	{
		text = "請先進行登入認證~";
		return;
	}
	ClassHttpRequest val = classHttpRequest_0;
	_Closure$__35-0 arg = new _Closure$__35-0(arg);
	arg.$VB$Local_totp_code = "";
	arg.$VB$Local_frm = new Form();
	Form $VB$Local_frm = arg.$VB$Local_frm;
	_Closure$__35-1 arg2 = default(_Closure$__35-1);
	_Closure$__35-1 CS$<>8__locals0 = new _Closure$__35-1(arg2);
	CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2 = arg;
	$VB$Local_frm.ShowIcon = false;
	$VB$Local_frm.StartPosition = FormStartPosition.CenterScreen;
	$VB$Local_frm.Text = "提示";
	$VB$Local_frm.Size = new Size(new Point(100, 120));
	$VB$Local_frm.FormBorderStyle = FormBorderStyle.FixedSingle;
	$VB$Local_frm.MaximizeBox = false;
	$VB$Local_frm.MinimizeBox = false;
	Label label = new Label();
	$VB$Local_frm.Controls.Add(label);
	label.Dock = DockStyle.Top;
	label.BringToFront();
	label.Text = "請打開手機露天代碼產生器應用程式，並輸入驗證碼。";
	label.AutoSize = false;
	label.Height = checked(label.Font.Height * 3);
	CS$<>8__locals0.$VB$Local_TextBox1 = new TextBox();
	$VB$Local_frm.Controls.Add(CS$<>8__locals0.$VB$Local_TextBox1);
	TextBox $VB$Local_TextBox = CS$<>8__locals0.$VB$Local_TextBox1;
	$VB$Local_TextBox.Dock = DockStyle.Top;
	$VB$Local_TextBox.BringToFront();
	Button button = new Button();
	$VB$Local_frm.Controls.Add(button);
	button.Dock = DockStyle.Top;
	button.BringToFront();
	button.Height = 30;
	button.Text = "確認";
	button.Click += [SpecialName] (object a0, EventArgs a1) =>
	{
		CS$<>8__locals0._Lambda$__0();
	};
	$VB$Local_frm.AcceptButton = button;
	IEnumerator enumerator = default(IEnumerator);
	try
	{
		enumerator = Application.OpenForms.GetEnumerator();
		if (enumerator.MoveNext())
		{
			((Form)enumerator.Current).Invoke((CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2.$I1 == null) ? (CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2.$I1 = [SpecialName] () =>
			{
				CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2.$VB$Local_frm.ShowDialog();
			}) : CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2.$I1);
		}
	}
	finally
	{
		if (enumerator is IDisposable)
		{
			(enumerator as IDisposable).Dispose();
		}
	}
	if (arg.$VB$Local_totp_code.Length < 1)
	{
		text += "~請輸入驗證碼!";
	}
	else
	{
		string text2 = "https://member.ruten.com.tw/totp/do_login_validation.php";
		string text3 = "totp_code=" + arg.$VB$Local_totp_code + "&remember_code=true";
		val.Referer = text2;
		string hTML = val.GetHTML((MethodHTTP)1, text2, (object)text3);
		ClassMy.Savefile(string.Format(Application.StartupPath + "\\test\\login\\ruten\\" + string_0 + "\\{0}.htm", "do_login_validation"), hTML);
		string text4;
		if (hTML.Trim().Length > 0 && hTML.Trim().StartsWith("{\"is_success\":true,"))
		{
			text4 = "~認證成功!";
			List<string> list = new List<string>();
			IEnumerator enumerator2 = default(IEnumerator);
			try
			{
				enumerator2 = val.CookieContainerclass.GetCookies(new Uri("https://mybid.ruten.com.tw/upload/step1.htm")).GetEnumerator();
				while (enumerator2.MoveNext())
				{
					Cookie cookie = (Cookie)enumerator2.Current;
					list.Add(cookie.Name + "=" + cookie.Value);
				}
			}
			finally
			{
				if (enumerator2 is IDisposable)
				{
					(enumerator2 as IDisposable).Dispose();
				}
			}
			if (list.Count > 0)
			{
				ClassMy.Savefile(Class4.string_0 + "\\" + string_0 + ".txt", string.Join(";", list.ToArray()));
			}
		}
		else
		{
			text4 = "~認證失敗!";
			text4 = ((!hTML.Contains("VALIDATE_FAILED")) ? (text4 + "\r\n" + Strings.Left(ClassMy.CheckHTML(hTML).ToString().Trim(), 100)) : (text4 + "\r\n可能驗證碼超時，請重試！"));
		}
		text += text4;
	}
	val = null;
}

After:

private void method_0(ClassHttpRequest classHttpRequest_0, string string_0)
{
	string text = "";
	if (!bool_1)
	{
		text = "請先進行登入認證~";
		return;
	}
	ClassHttpRequest val = classHttpRequest_0;
	_Closure$__35-0 arg = new _Closure$__35-0(arg);
	arg.$VB$Local_totp_code = "";
	arg.$VB$Local_frm = new Form();
	Form $VB$Local_frm = arg.$VB$Local_frm;
	_Closure$__35-1 arg2 = default(_Closure$__35-1);
	_Closure$__35-1 CS$<>8__locals0 = new _Closure$__35-1(arg2);
	CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2 = arg;
	$VB$Local_frm.ShowIcon = false;
	$VB$Local_frm.StartPosition = FormStartPosition.CenterScreen;
	$VB$Local_frm.Text = "提示";
	$VB$Local_frm.Size = new Size(new Point(100, 120));
	$VB$Local_frm.FormBorderStyle = FormBorderStyle.FixedSingle;
	$VB$Local_frm.MaximizeBox = false;
	$VB$Local_frm.MinimizeBox = false;
	Label label = new Label();
	$VB$Local_frm.Controls.Add(label);
	label.Dock = DockStyle.Top;
	label.BringToFront();
	label.Text = "請打開手機露天代碼產生器應用程式，並輸入驗證碼。";
	label.AutoSize = false;
	label.Height = checked(label.Font.Height * 3);
	CS$<>8__locals0.$VB$Local_TextBox1 = new TextBox();
	$VB$Local_frm.Controls.Add(CS$<>8__locals0.$VB$Local_TextBox1);
	TextBox $VB$Local_TextBox = CS$<>8__locals0.$VB$Local_TextBox1;
	$VB$Local_TextBox.Dock = DockStyle.Top;
	$VB$Local_TextBox.BringToFront();
	Button button = new Button();
	$VB$Local_frm.Controls.Add(button);
	button.Dock = DockStyle.Top;
	button.BringToFront();
	button.Height = 30;
	button.Text = "確認";
	button.Click += [SpecialName] (object a0, EventArgs a1) =>
	{
		CS$<>8__locals0._Lambda$__0();
	};
	$VB$Local_frm.AcceptButton = button;
	IEnumerator enumerator = default(IEnumerator);
	try
	{
		enumerator = Application.OpenForms.GetEnumerator();
		if (enumerator.MoveNext())
		{
			((Form)enumerator.Current).Invoke((VB$AnonymousDelegate_0)([SpecialName] () =>
			{
				CS$<>8__locals0.$VB$NonLocal_$VB$Closure_2.$VB$Local_frm.ShowDialog();
			}));
		}
	}
	finally
	{
		if (enumerator is IDisposable)
		{
			(enumerator as IDisposable).Dispose();
		}
	}
	if (arg.$VB$Local_totp_code.Length < 1)
	{
		text += "~請輸入驗證碼!";
	}
	else
	{
		string text2 = "https://member.ruten.com.tw/totp/do_login_validation.php";
		string text3 = "totp_code=" + arg.$VB$Local_totp_code + "&remember_code=true";
		val.Referer = text2;
		string hTML = val.GetHTML((MethodHTTP)1, text2, (object)text3);
		ClassMy.Savefile(string.Format(Application.StartupPath + "\\test\\login\\ruten\\" + string_0 + "\\{0}.htm", "do_login_validation"), hTML);
		string text4;
		if (hTML.Trim().Length > 0 && hTML.Trim().StartsWith("{\"is_success\":true,"))
		{
			text4 = "~認證成功!";
			List<string> list = new List<string>();
			IEnumerator enumerator2 = default(IEnumerator);
			try
			{
				enumerator2 = val.CookieContainerclass.GetCookies(new Uri("https://mybid.ruten.com.tw/upload/step1.htm")).GetEnumerator();
				while (enumerator2.MoveNext())
				{
					Cookie cookie = (Cookie)enumerator2.Current;
					list.Add(cookie.Name + "=" + cookie.Value);
				}
			}
			finally
			{
				if (enumerator2 is IDisposable)
				{
					(enumerator2 as IDisposable).Dispose();
				}
			}
			if (list.Count > 0)
			{
				ClassMy.Savefile(Class4.string_0 + "\\" + string_0 + ".txt", string.Join(";", list.ToArray()));
			}
		}
		else
		{
			text4 = "~認證失敗!";
			text4 = ((!hTML.Contains("VALIDATE_FAILED")) ? (text4 + "\r\n" + Strings.Left(ClassMy.CheckHTML(hTML).ToString().Trim(), 100)) : (text4 + "\r\n可能驗證碼超時，請重試！"));
		}
		text += text4;
	}
	val = null;
}

Smaller code to reproduce the issue:

Dim t As String = "hello"
Dim collection As List(Of String) = New List(Of String)
For Each element In collection.Where(Function(x) x = t)
	Console.WriteLine(element)
Next

Solution

Implement support for the pattern seen in this sample.
A unit test was not added as ILSpy does not currently support VB.NET closures/display classes as they differ in structure from the C# ones. This lack of support makes it impossible to create pretty C# decompilation while testing this pattern.

[ElektroKill]

In the latest commit, I fixed support for cached delegate initialization detection using the pattern from CachedDelegateInitializationVB . It turns out that the stack slot which is part of the pattern should not be restricted to only one load.

Test code:

Public Shared Function UseDelegate() As Func(Of Integer)
	Dim del As Func(Of Integer) = Function() 2
	del(2)
	Return del
End Function

ILAst before CachedDelegateInitialization transform:

if (logic.not(comp.o(ldsfld $I1-0 != ldnull))) Block IL_0000 {
	stloc S_0(stsfld $I1-0(newobj Func..ctor(ldsfld $I, ldftn _Lambda$__1-0)))
} else Block IL_0007 {
	stloc S_0(ldsfld $I1-0)
}
callvirt Invoke(ldloc S_0)
leave IL_0005 (ldloc S_0)

S_0 has more than one usage!

[ElektroKill]

Applied the fix mentioned in the comment above to the newly added CachedDelegateInitializationVBWithClosure pattern too.

[ElektroKill]

The latest commit adds support for a rare case of cached delegate initialization generated by the VB compiler when an anonymous method that does not utilize captured variables and is directly returned.

VB code:

Public Shared Function ReturnDelegate() As Func(Of Integer)
	Return Function() 2
End Function

IL:

IL_0000: ldsfld class [mscorlib]System.Func`1<int32> DelegateConstruction/_Closure$____0::'$I0-0'
IL_0005: brfalse.s IL_000d

IL_0007: ldsfld class [mscorlib]System.Func`1<int32> DelegateConstruction/_Closure$____0::'$I0-0'
IL_000c: ret

IL_000d: ldsfld class DelegateConstruction/_Closure$____0 DelegateConstruction/_Closure$____0::$I
IL_0012: ldftn instance int32 DelegateConstruction/_Closure$____0::'_Lambda$__0-0'()
IL_0018: newobj instance void class [mscorlib]System.Func`1<int32>::.ctor(object, native int)
IL_001d: dup
IL_001e: stsfld class [mscorlib]System.Func`1<int32> DelegateConstruction/_Closure$____0::'$I0-0'
IL_0023: ret

ILAst (before cached delegate initialization transformation):

if (comp.o(ldsfld $I0-0 != ldnull)) leave IL_0005 (ldsfld $I0-0)
leave IL_0005 (stsfld $I0-0(newobj Func..ctor(ldsfld $I, ldftn _Lambda$__0-0)))

[siegfriedpammer]

Thank you very much for your contribution!