Support struct IResults (#37344)

Author: BrennanConroy

src/Http/Http.Extensions/src/RequestDelegateFactory.cs

@@ -487,6 +487,11 @@ private static Expression AddResponseWritingToMethodCall(Expression methodCall,
             }
             else if (typeof(IResult).IsAssignableFrom(returnType))
             {
+                if (returnType.IsValueType)
+                {
+                    var box = Expression.TypeAs(methodCall, typeof(IResult));
+                    return Expression.Call(ResultWriteResponseAsyncMethod, box, HttpContextExpr);
+                }
                 return Expression.Call(ResultWriteResponseAsyncMethod, methodCall, HttpContextExpr);
             }
             else if (returnType == typeof(string))

src/Http/Http.Extensions/test/RequestDelegateFactoryTests.cs

@@ -2003,6 +2003,10 @@ public static IEnumerable<object[]> CustomResults
                 static Task<object> StaticTaskOfIResultAsObject() => Task.FromResult<object>(new CustomResult("Still not enough tests!"));
                 static ValueTask<object> StaticValueTaskOfIResultAsObject() => ValueTask.FromResult<object>(new CustomResult("Still not enough tests!"));
 
+                StructResult TestStructAction() => new StructResult(resultString);
+                Task<StructResult> TaskTestStructAction() => Task.FromResult(new StructResult(resultString));
+                ValueTask<StructResult> ValueTaskTestStructAction() => ValueTask.FromResult(new StructResult(resultString));
+
                 return new List<object[]>
                 {
                     new object[] { (Func<CustomResult>)TestAction },
@@ -2021,6 +2025,10 @@ public static IEnumerable<object[]> CustomResults
 
                     new object[] { (Func<Task<object>>)StaticTaskOfIResultAsObject},
                     new object[] { (Func<ValueTask<object>>)StaticValueTaskOfIResultAsObject},
+
+                    new object[] { (Func<StructResult>)TestStructAction },
+                    new object[] { (Func<Task<StructResult>>)TaskTestStructAction },
+                    new object[] { (Func<ValueTask<StructResult>>)ValueTaskTestStructAction },
                 };
             }
         }
@@ -3247,6 +3255,21 @@ public Task ExecuteAsync(HttpContext httpContext)
             }
         }
 
+        private struct StructResult : IResult
+        {
+            private readonly string _resultString;
+
+            public StructResult(string resultString)
+            {
+                _resultString = resultString;
+            }
+
+            public Task ExecuteAsync(HttpContext httpContext)
+            {
+                return httpContext.Response.WriteAsync(_resultString);
+            }
+        }
+
         private class ExceptionThrowingRequestBodyStream : Stream
         {
             private readonly Exception _exceptionToThrow;