From 67b87d36468f652b15ec1c45ab497d56744be18b Mon Sep 17 00:00:00 2001
From: Jackson Schuster <jschuster@microsoft.com>
Date: Mon, 8 Aug 2022 10:36:03 -0700
Subject: [PATCH 1/4] Test that basic ref field operations don't crash linker

---
 eng/Versions.props                            |   3 +-
 .../BasicTests.g.cs                           |   6 +
 .../Basic/LinkerHandlesRefFields.cs           | 119 ++++++++++++++++++
 .../Basic/UnusedFieldsOfStructsAreKept.cs     |  18 +++
 4 files changed, 144 insertions(+), 2 deletions(-)
 create mode 100644 test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs

diff --git a/eng/Versions.props b/eng/Versions.props
index cdf227c176f0..676fd94b314b 100644
--- a/eng/Versions.props
+++ b/eng/Versions.props
@@ -9,7 +9,6 @@
     <PreReleaseVersionLabel>1</PreReleaseVersionLabel>
   </PropertyGroup>
   <PropertyGroup>
-    <UsingToolMicrosoftNetCompilers>true</UsingToolMicrosoftNetCompilers>
     <!-- ilasm -->
     <MicrosoftNETSdkILPackageVersion>7.0.0-rc.1.22374.4</MicrosoftNETSdkILPackageVersion>
     <!-- see https://github.com/dotnet/runtime/issues/1338 -->
@@ -21,7 +20,7 @@
     <MicrosoftDotNetApiCompatVersion>7.0.0-beta.22372.1</MicrosoftDotNetApiCompatVersion>
     <MicrosoftDotNetCodeAnalysisVersion>6.0.0-beta.21271.1</MicrosoftDotNetCodeAnalysisVersion>
     <MicrosoftCodeAnalysisCSharpCodeStyleVersion>3.10.0-2.final</MicrosoftCodeAnalysisCSharpCodeStyleVersion>
-    <MicrosoftCodeAnalysisVersion>4.3.0-2.final</MicrosoftCodeAnalysisVersion>
+    <MicrosoftCodeAnalysisVersion>4.4.0-2.22379.3</MicrosoftCodeAnalysisVersion>
     <MicrosoftCodeAnalysisCSharpAnalyzerTestingXunitVersion>1.0.1-beta1.*</MicrosoftCodeAnalysisCSharpAnalyzerTestingXunitVersion>
     <MicrosoftCodeAnalysisBannedApiAnalyzersVersion>3.3.2</MicrosoftCodeAnalysisBannedApiAnalyzersVersion>
     <!-- This controls the version of the cecil package, or the version of cecil in the project graph
diff --git a/test/ILLink.RoslynAnalyzer.Tests/generated/ILLink.RoslynAnalyzer.Tests.Generator/ILLink.RoslynAnalyzer.Tests.TestCaseGenerator/BasicTests.g.cs b/test/ILLink.RoslynAnalyzer.Tests/generated/ILLink.RoslynAnalyzer.Tests.Generator/ILLink.RoslynAnalyzer.Tests.TestCaseGenerator/BasicTests.g.cs
index a6fd75c94ff6..c5834582d31f 100644
--- a/test/ILLink.RoslynAnalyzer.Tests/generated/ILLink.RoslynAnalyzer.Tests.Generator/ILLink.RoslynAnalyzer.Tests.TestCaseGenerator/BasicTests.g.cs
+++ b/test/ILLink.RoslynAnalyzer.Tests/generated/ILLink.RoslynAnalyzer.Tests.Generator/ILLink.RoslynAnalyzer.Tests.TestCaseGenerator/BasicTests.g.cs
@@ -39,6 +39,12 @@ public Task InterfaceMethodImplementedOnBaseClassDoesNotGetStripped ()
 			return RunTest (allowMissingWarnings: true);
 		}
 
+		[Fact]
+		public Task LinkerHandlesRefFields ()
+		{
+			return RunTest (allowMissingWarnings: true);
+		}
+
 		[Fact]
 		public Task MultiLevelNestedClassesAllRemovedWhenNonUsed ()
 		{
diff --git a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
new file mode 100644
index 000000000000..71c2cca1162c
--- /dev/null
+++ b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
@@ -0,0 +1,119 @@
+// 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;
+using System.Collections.Generic;
+using System.Diagnostics.CodeAnalysis;
+using System.Linq;
+using System.Runtime.CompilerServices;
+using System.Text;
+using System.Threading.Tasks;
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
+
+namespace Mono.Linker.Tests.Cases.Basic
+{
+	[ExpectedNoWarnings]
+	[SkipKeptItemsValidation]
+	class LinkerHandlesRefFields
+	{
+		ref struct RS
+		{
+			public ref int i;
+			public ref double d;
+			public RS2 rs2;
+			public ref string str;
+			public ref object obj;
+			public ref Type t;
+			public void MoveThis()
+			{
+				this = new RS ();
+			}
+		}
+
+		ref struct RS2
+		{
+			public ref int i;
+			public ref double d;
+			public ref string str;
+			public ref object obj;
+			public ref Type t;
+			public void MoveThis()
+			{
+				this = new RS2 ();
+			}
+		}
+
+		delegate RS2 RsParamRs2Return (RS rs);
+		delegate ref RS2 RefRSParamRefRs2Return (ref RS rs);
+		delegate ref int RsParamRefIntReturn (RS rs);
+
+		public static void Main(string[] args)
+		{
+			scoped RS rs = new RS ();
+			scoped RS2 rs2 = new RS2 ();
+
+			// Assign by value
+			rs.i = rs2.i;
+			rs2.d = rs2.d;
+			rs.obj = rs2.obj;
+			rs2.t = rs.t;
+
+			// Assign by ref
+			rs.i = ref rs2.i;
+			rs2.d = ref rs2.d;
+			rs.obj = ref rs2.obj;
+			rs2.t = ref rs.t;
+
+			// Assign in different basic blocks
+			if (args[0] == "") {
+				rs.i = ref rs2.i;
+				rs.d = rs2.d;
+				rs.obj = ref rs2.obj;
+				rs.t = rs2.t;
+			} else {
+				rs2.i = rs.i;
+				rs2.d = ref rs.d;
+				rs2.obj = rs.obj;
+				rs2.t = ref rs.t;
+			}
+
+			// Cast fields
+			rs.t = (Type) rs.obj;
+			rs.i = (int) rs.d;
+			rs2.i = (int) rs.d;
+
+			// In Lambdas
+			RsParamRs2Return f = (RS rs) => rs.rs2;
+			rs.rs2 = f (rs);
+			RefRSParamRefRs2Return h = (ref RS rs) => ref rs.rs2;
+			rs.rs2 = h (ref rs);
+			RsParamRefIntReturn g = (RS rs) => ref f (rs).i;
+			rs.i = g (rs);
+
+			// As parameters and returns for local functions
+			RS LocalMethod(RS2 rs)
+			{
+				rs.d = 0.2;
+				return new RS ();
+			}
+			rs = LocalMethod (rs.rs2);
+
+			ref RS LocalMethodRef(ref RS rs)
+			{
+				return ref rs;
+			}
+			ref RS refRs = ref LocalMethodRef (ref rs);
+			refRs = LocalMethodRef (ref rs);
+
+			ref int ReturnRefInt (ref int i)
+			{
+				return ref i;
+			}
+			rs.i = ReturnRefInt (ref rs2.i);
+
+			// Call methods with this
+			rs.MoveThis ();
+			rs2.MoveThis ();
+		}
+	}
+}
diff --git a/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs b/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
index fb300fe6a07c..c768a97a57f2 100644
--- a/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
+++ b/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
@@ -1,4 +1,6 @@
 using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using System.Runtime.CompilerServices;
+using System;
 
 namespace Mono.Linker.Tests.Cases.Basic
 {
@@ -8,6 +10,7 @@ public static void Main ()
 		{
 			A a = new A ();
 			PreventCompilerOptimization (a);
+			R r = new R ();
 		}
 
 		[Kept]
@@ -27,5 +30,20 @@ public void UnusedMethod ()
 			{
 			}
 		}
+
+		[KeptAttributeAttribute(typeof(IsByRefLikeAttribute))]
+		[KeptAttributeAttribute(typeof(CompilerFeatureRequiredAttribute))]
+		[KeptAttributeAttribute(typeof(ObsoleteAttribute))]
+		ref struct R
+		{
+			[Kept]
+			public ref int UnusedRefField;
+
+			[Kept]
+			int UnusedField;
+
+			[Kept]
+			int UsedField;
+		}
 	}
 }
\ No newline at end of file

From e2a21a17248a0d152712d146e79f1ff88cd1e05f Mon Sep 17 00:00:00 2001
From: Jackson Schuster <jschuster@microsoft.com>
Date: Mon, 8 Aug 2022 13:17:04 -0700
Subject: [PATCH 2/4] formatting

---
 .../Basic/LinkerHandlesRefFields.cs                    | 10 +++++-----
 .../Basic/UnusedFieldsOfStructsAreKept.cs              | 10 +++++-----
 2 files changed, 10 insertions(+), 10 deletions(-)

diff --git a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
index 71c2cca1162c..548d52d2b4a6 100644
--- a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
+++ b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
@@ -24,7 +24,7 @@ ref struct RS
 			public ref string str;
 			public ref object obj;
 			public ref Type t;
-			public void MoveThis()
+			public void MoveThis ()
 			{
 				this = new RS ();
 			}
@@ -37,7 +37,7 @@ ref struct RS2
 			public ref string str;
 			public ref object obj;
 			public ref Type t;
-			public void MoveThis()
+			public void MoveThis ()
 			{
 				this = new RS2 ();
 			}
@@ -47,7 +47,7 @@ public void MoveThis()
 		delegate ref RS2 RefRSParamRefRs2Return (ref RS rs);
 		delegate ref int RsParamRefIntReturn (RS rs);
 
-		public static void Main(string[] args)
+		public static void Main (string[] args)
 		{
 			scoped RS rs = new RS ();
 			scoped RS2 rs2 = new RS2 ();
@@ -91,14 +91,14 @@ public static void Main(string[] args)
 			rs.i = g (rs);
 
 			// As parameters and returns for local functions
-			RS LocalMethod(RS2 rs)
+			RS LocalMethod (RS2 rs)
 			{
 				rs.d = 0.2;
 				return new RS ();
 			}
 			rs = LocalMethod (rs.rs2);
 
-			ref RS LocalMethodRef(ref RS rs)
+			ref RS LocalMethodRef (ref RS rs)
 			{
 				return ref rs;
 			}
diff --git a/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs b/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
index c768a97a57f2..ff4bb5ae92a8 100644
--- a/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
+++ b/test/Mono.Linker.Tests.Cases/Basic/UnusedFieldsOfStructsAreKept.cs
@@ -1,6 +1,6 @@
-using Mono.Linker.Tests.Cases.Expectations.Assertions;
-using System.Runtime.CompilerServices;
 using System;
+using System.Runtime.CompilerServices;
+using Mono.Linker.Tests.Cases.Expectations.Assertions;
 
 namespace Mono.Linker.Tests.Cases.Basic
 {
@@ -31,9 +31,9 @@ public void UnusedMethod ()
 			}
 		}
 
-		[KeptAttributeAttribute(typeof(IsByRefLikeAttribute))]
-		[KeptAttributeAttribute(typeof(CompilerFeatureRequiredAttribute))]
-		[KeptAttributeAttribute(typeof(ObsoleteAttribute))]
+		[KeptAttributeAttribute (typeof (IsByRefLikeAttribute))]
+		[KeptAttributeAttribute (typeof (CompilerFeatureRequiredAttribute))]
+		[KeptAttributeAttribute (typeof (ObsoleteAttribute))]
 		ref struct R
 		{
 			[Kept]

From bf7b0ce6a27a9d9589cdbf851f41bcc74db7a59f Mon Sep 17 00:00:00 2001
From: Jackson Schuster <jschuster@microsoft.com>
Date: Mon, 8 Aug 2022 14:50:06 -0700
Subject: [PATCH 3/4] PR Feedback:

- Add virtual methods with ref structs
- Add fields with DAM
- Add method with ref structs with RUC and DAM
---
 .../Basic/LinkerHandlesRefFields.cs           | 56 ++++++++++++++++++-
 1 file changed, 54 insertions(+), 2 deletions(-)

diff --git a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
index 548d52d2b4a6..84d66b92f9a7 100644
--- a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
+++ b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
@@ -9,6 +9,7 @@
 using System.Text;
 using System.Threading.Tasks;
 using Mono.Linker.Tests.Cases.Expectations.Assertions;
+using Mono.Linker.Tests.Cases.Expectations.Helpers;
 
 namespace Mono.Linker.Tests.Cases.Basic
 {
@@ -21,7 +22,6 @@ ref struct RS
 			public ref int i;
 			public ref double d;
 			public RS2 rs2;
-			public ref string str;
 			public ref object obj;
 			public ref Type t;
 			public void MoveThis ()
@@ -34,7 +34,6 @@ ref struct RS2
 		{
 			public ref int i;
 			public ref double d;
-			public ref string str;
 			public ref object obj;
 			public ref Type t;
 			public void MoveThis ()
@@ -43,10 +42,60 @@ public void MoveThis ()
 			}
 		}
 
+		ref struct RsAnnotations
+		{
+			[DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
+			public ref Type tDam;
+
+			[RequiresUnreferencedCode ("message for " + nameof (RefReturnWithMethods_HasRuc))]
+			[return: DynamicallyAccessedMembers (DynamicallyAccessedMemberTypes.PublicMethods)]
+			public static ref Type RefReturnWithMethods_HasRuc (ref RsAnnotations rs)
+			{
+				return ref rs.tDam;
+			}
+		}
+
+		interface IRS
+		{
+			void RSParam (ref RS rsRef, RS rs);
+			RS RSReturn ();
+			ref RS2 RSParamAndReturn (ref RS rs);
+		}
+
+		class Base : IRS
+		{
+			public virtual void RSParam (ref RS rsRef, RS rs) { }
+			public virtual RS RSReturn () { return new RS (); }
+			public virtual ref RS2 RSParamAndReturn (ref RS rs)
+			{
+				return ref rs.rs2;
+			}
+		}
+
+		class Derived : Base, IRS
+		{
+			public override void RSParam (ref RS rsRef, RS rs) { }
+			public override RS RSReturn () { return new RS (); }
+		}
+
+		static void TestVirtualMethods ()
+		{
+			typeof (Base).RequiresPublicMethods ();
+			typeof (Derived).RequiresPublicMethods ();
+		}
+
+		// Ref structs can't implement interfaces
+
 		delegate RS2 RsParamRs2Return (RS rs);
 		delegate ref RS2 RefRSParamRefRs2Return (ref RS rs);
 		delegate ref int RsParamRefIntReturn (RS rs);
 
+		[ExpectedWarning ("IL2026", "message for " + nameof (RsAnnotations.RefReturnWithMethods_HasRuc))]
+		static void CallAnnotatedMethod ()
+		{
+			RsAnnotations rsa = new RsAnnotations ();
+			RsAnnotations.RefReturnWithMethods_HasRuc (ref rsa);
+		}
 		public static void Main (string[] args)
 		{
 			scoped RS rs = new RS ();
@@ -114,6 +163,9 @@ ref int ReturnRefInt (ref int i)
 			// Call methods with this
 			rs.MoveThis ();
 			rs2.MoveThis ();
+
+			CallAnnotatedMethod ();
+			TestVirtualMethods ();
 		}
 	}
 }

From 1d87c2ca269d344f4b327c91d55d7b490c452d05 Mon Sep 17 00:00:00 2001
From: Jackson Schuster <jschuster@microsoft.com>
Date: Tue, 9 Aug 2022 10:27:42 -0700
Subject: [PATCH 4/4] Add comment describing scope of test

---
 test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
index 84d66b92f9a7..8717e220f3b1 100644
--- a/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
+++ b/test/Mono.Linker.Tests.Cases/Basic/LinkerHandlesRefFields.cs
@@ -13,6 +13,9 @@
 
 namespace Mono.Linker.Tests.Cases.Basic
 {
+	/// <summary>
+	/// This test is only to ensure that the linker does not crash when programs use ref fields (new to dotnet 7). This test does not validate any expected behaviors around ref fields.
+	/// </summary>
 	[ExpectedNoWarnings]
 	[SkipKeptItemsValidation]
 	class LinkerHandlesRefFields