From 6cf354afa1d33b4d5824866e3a5f1428b088e6bb Mon Sep 17 00:00:00 2001
From: Eric Erhardt <eric.erhardt@microsoft.com>
Date: Tue, 17 Jan 2023 18:22:46 -0600
Subject: [PATCH 1/2] LambdaExpression.CanCompileToIL should respect
 IsDynamicCodeSupported

With the new feature switch added in https://github.com/dotnet/runtime/issues/39806, calling LambdaExpression.Compile is throwing a PlatformNotSupportedException. Instead, LambdaExpression should respect IsDynamicCodeSupported and switch to using the interpreter when IsDynamicCodeSupported is false.
---
 .../src/System/Linq/Expressions/LambdaExpression.cs         | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs b/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs
index d8621b03cdd22..f4c2aa2f74baf 100644
--- a/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs
+++ b/src/libraries/System.Linq.Expressions/src/System/Linq/Expressions/LambdaExpression.cs
@@ -26,7 +26,7 @@ public abstract class LambdaExpression : Expression, IParameterProvider
         private readonly Expression _body;
 
         // This can be flipped to false using feature switches at publishing time
-        public static bool CanCompileToIL => true;
+        public static bool CanCompileToIL => RuntimeFeature.IsDynamicCodeSupported;
 
         // This could be flipped to false using feature switches at publishing time
         public static bool CanInterpret => true;
@@ -154,7 +154,7 @@ public Delegate Compile()
         /// <returns>A delegate containing the compiled version of the lambda.</returns>
         public Delegate Compile(bool preferInterpretation)
         {
-            if (CanCompileToIL && CanInterpret && preferInterpretation)
+            if (CanInterpret && preferInterpretation)
             {
                 return new Interpreter.LightCompiler().CompileTop(this).CreateDelegate();
             }
@@ -234,7 +234,7 @@ internal Expression(Expression body)
         /// <returns>A delegate containing the compiled version of the lambda.</returns>
         public new TDelegate Compile(bool preferInterpretation)
         {
-            if (CanCompileToIL && CanInterpret && preferInterpretation)
+            if (CanInterpret && preferInterpretation)
             {
                 return (TDelegate)(object)new Interpreter.LightCompiler().CompileTop(this).CreateDelegate();
             }

From 807d807be29b736f6cdf965dd838e2069996a491 Mon Sep 17 00:00:00 2001
From: Eric Erhardt <eric.erhardt@microsoft.com>
Date: Wed, 18 Jan 2023 12:29:39 -0600
Subject: [PATCH 2/2] Add tests

---
 .../tests/CompilerTests.cs                    | 24 +++++++++++++++++++
 .../System.Linq.Expressions.Tests.csproj      |  1 +
 2 files changed, 25 insertions(+)

diff --git a/src/libraries/System.Linq.Expressions/tests/CompilerTests.cs b/src/libraries/System.Linq.Expressions/tests/CompilerTests.cs
index 069d72e6abcef..3c2f4bc6b5698 100644
--- a/src/libraries/System.Linq.Expressions/tests/CompilerTests.cs
+++ b/src/libraries/System.Linq.Expressions/tests/CompilerTests.cs
@@ -3,6 +3,7 @@
 
 using System.Runtime.CompilerServices;
 using System.Text.RegularExpressions;
+using Microsoft.DotNet.RemoteExecutor;
 using Xunit;
 
 namespace System.Linq.Expressions.Tests
@@ -429,6 +430,29 @@ private static void Verify_VariableBinder_CatchBlock_Filter(CatchBlock @catch)
 
             Assert.Throws<InvalidOperationException>(() => e.Compile());
         }
+
+        /// <summary>
+        /// Verifies that compiling and executing a lambda method works when IsDynamicCodeSupported == false.
+        /// </summary>
+        [ConditionalFact(typeof(RemoteExecutor), nameof(RemoteExecutor.IsSupported))]
+        public static void CompileWorksWhenDynamicCodeNotSupported()
+        {
+            RemoteInvokeOptions options = new RemoteInvokeOptions();
+            options.RuntimeConfigurationOptions.Add("System.Runtime.CompilerServices.RuntimeFeature.IsDynamicCodeSupported", false.ToString());
+
+            using RemoteInvokeHandle remoteHandle = RemoteExecutor.Invoke(static () =>
+            {
+                ParameterExpression param = Expression.Parameter(typeof(int));
+
+                Func<int, int> typedDel =
+                    Expression.Lambda<Func<int, int>>(Expression.Add(param, Expression.Constant(4)), param).Compile();
+                Assert.Equal(304, typedDel(300));
+
+                Delegate del =
+                    Expression.Lambda(Expression.Add(param, Expression.Constant(5)), param).Compile();
+                Assert.Equal(305, del.DynamicInvoke(300));
+            }, options);
+        }
     }
 
     public enum ConstantsEnum
diff --git a/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj b/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
index 481d04cc820ac..97ead77d06810 100644
--- a/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
+++ b/src/libraries/System.Linq.Expressions/tests/System.Linq.Expressions.Tests.csproj
@@ -1,6 +1,7 @@
 <Project Sdk="Microsoft.NET.Sdk">
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent);$(NetCoreAppCurrent)-ios;$(NetCoreAppCurrent)-tvos;$(NetCoreAppCurrent)-maccatalyst</TargetFrameworks>
+    <IncludeRemoteExecutor>true</IncludeRemoteExecutor>
   </PropertyGroup>
 
   <ItemGroup>