Throw if a by ref type is returned to avoid making invalid ILdavidfowl/fix-ref-structs

2 files changed, 32 insertions, 1 deletions

diff --git a/src/Http/Http.Extensions/src/RequestDelegateFactory.cs b/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
index 810d902964..d87660f451 100644
--- a/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
+++ b/src/Http/Http.Extensions/src/RequestDelegateFactory.cs
@@ -972,7 +972,7 @@ public static partial class RequestDelegateFactory
             else
             {
                 // TODO: Handle custom awaitables
-                throw new NotSupportedException($"Unsupported return type: {returnType}");
+                throw new NotSupportedException($"Unsupported return type: {TypeNameHelper.GetTypeDisplayName(returnType)}");
             }
         }
         else if (typeof(IResult).IsAssignableFrom(returnType))
@@ -988,6 +988,11 @@ public static partial class RequestDelegateFactory
         {
             return Expression.Call(StringResultWriteResponseAsyncMethod, HttpContextExpr, methodCall);
         }
+        else if (returnType.IsByRefLike)
+        {
+            // Unsupported
+            throw new NotSupportedException($"Unsupported return type: {TypeNameHelper.GetTypeDisplayName(returnType)}");
+        }
         else if (returnType.IsValueType)
         {
             var box = Expression.TypeAs(methodCall, typeof(object));
diff --git a/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs b/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
index 3517fe81b4..808fd4bf0d 100644
--- a/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
+++ b/src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs
@@ -2179,6 +2179,32 @@ public class RequestDelegateFactoryTests : LoggedTest
         Assert.Equal(default, structToBeZeroed);
     }
 
+    [Fact]
+    public void RequestDelegateFactoryThrowsForByRefReturnTypes()
+    {
+        ReadOnlySpan<byte> Method1() => "hello world"u8;
+        Span<byte> Method2() => "hello world"u8.ToArray();
+        RefStruct Method3() => new("hello world"u8);
+
+        var ex1 = Assert.Throws<NotSupportedException>(() => RequestDelegateFactory.Create(Method1));
+        var ex2 = Assert.Throws<NotSupportedException>(() => RequestDelegateFactory.Create(Method2));
+        var ex3 = Assert.Throws<NotSupportedException>(() => RequestDelegateFactory.Create(Method3));
+
+        Assert.Equal("Unsupported return type: System.ReadOnlySpan<byte>", ex1.Message);
+        Assert.Equal("Unsupported return type: System.Span<byte>", ex2.Message);
+        Assert.Equal($"Unsupported return type: {typeof(RefStruct).FullName}", ex3.Message);
+    }
+
+    ref struct RefStruct
+    {
+        public ReadOnlySpan<byte> Buffer { get; }
+
+        public RefStruct(ReadOnlySpan<byte> buffer)
+        {
+            Buffer = buffer;
+        }
+    }
+
     [Theory]
     [InlineData(true)]
     [InlineData(false)]