From d1b0e2bfd03488d6f8b6b709607d3fbc2587a3c1 Mon Sep 17 00:00:00 2001
From: Ryan Nowak <nowakra@gmail.com>
Date: Thu, 11 Oct 2018 18:12:53 -0700
Subject: [PATCH] Teach property helper to ignore ref-struct

Fixes: https://github.com/aspnet/Mvc/issues/8552
---
 .../PropertyHelper.cs                         | 29 +++++++++++++++--
 .../PropertyHelperTest.cs                     | 32 +++++++++++++++++++
 2 files changed, 59 insertions(+), 2 deletions(-)

diff --git a/shared/Microsoft.Extensions.PropertyHelper.Sources/PropertyHelper.cs b/shared/Microsoft.Extensions.PropertyHelper.Sources/PropertyHelper.cs
index 27ba5661a42..f6aad151e52 100644
--- a/shared/Microsoft.Extensions.PropertyHelper.Sources/PropertyHelper.cs
+++ b/shared/Microsoft.Extensions.PropertyHelper.Sources/PropertyHelper.cs
@@ -7,6 +7,7 @@
 using System.Diagnostics;
 using System.Linq;
 using System.Reflection;
+using System.Runtime.CompilerServices;
 
 namespace Microsoft.Extensions.Internal
 {
@@ -37,6 +38,12 @@ internal class PropertyHelper
         private static readonly ConcurrentDictionary<Type, PropertyHelper[]> VisiblePropertiesCache =
             new ConcurrentDictionary<Type, PropertyHelper[]>();
 
+        // We need to be able to check if a type is a 'ref struct' - but we need to be able to compile
+        // for platforms where the attribute is not defined, like net46. So we can fetch the attribute
+        // by late binding. If the attribute isn't defined, then we assume we won't encounter any
+        // 'ref struct' types.
+        private static readonly Type IsByRefLikeAttribute = Type.GetType("System.Runtime.CompilerServices.IsByRefLikeAttribute", throwOnError: false);
+
         private Action<object, object> _valueSetter;
         private Func<object, object> _valueGetter;
 
@@ -511,16 +518,34 @@ protected static PropertyHelper[] GetProperties(
             return helpers;
         }
 
-        // Indexed properties are not useful (or valid) for grabbing properties off an object.
+        
         private static bool IsInterestingProperty(PropertyInfo property)
         {
             // For improving application startup time, do not use GetIndexParameters() api early in this check as it
             // creates a copy of parameter array and also we would like to check for the presence of a get method
             // and short circuit asap.
-            return property.GetMethod != null &&
+            return 
+                property.GetMethod != null &&
                 property.GetMethod.IsPublic &&
                 !property.GetMethod.IsStatic &&
+                
+                // PropertyHelper can't work with ref structs.
+                !IsRefStructProperty(property) &&
+
+                // Indexed properties are not useful (or valid) for grabbing properties off an object.
                 property.GetMethod.GetParameters().Length == 0;
         }
+
+        // PropertyHelper can't really interact with ref-struct properties since they can't be 
+        // boxed and can't be used as generic types. We just ignore them.
+        //
+        // see: https://github.com/aspnet/Mvc/issues/8545
+        private static bool IsRefStructProperty(PropertyInfo property)
+        {
+            return
+                IsByRefLikeAttribute != null &&
+                property.PropertyType.IsValueType &&
+                property.PropertyType.IsDefined(IsByRefLikeAttribute);
+        }
     }
 }
diff --git a/test/Microsoft.Extensions.Internal.Test/PropertyHelperTest.cs b/test/Microsoft.Extensions.Internal.Test/PropertyHelperTest.cs
index 19cf08b3705..1c43dc880b3 100644
--- a/test/Microsoft.Extensions.Internal.Test/PropertyHelperTest.cs
+++ b/test/Microsoft.Extensions.Internal.Test/PropertyHelperTest.cs
@@ -153,6 +153,22 @@ public void PropertyHelper_DoesNotFindStaticProperties()
             Assert.Equal("Prop5", helper.Name);
         }
 
+#if NETSTANDARD || NETCOREAPP
+        [Fact]
+        public void PropertyHelper_RefStructProperties()
+        {
+            // Arrange
+            var obj = new RefStructProperties();
+
+            // Act + Assert
+            var helper = Assert.Single(PropertyHelper.GetProperties(obj.GetType().GetTypeInfo()));
+            Assert.Equal("Prop5", helper.Name);
+        }
+#elif NET46 || NET461
+#else
+#error Unknown TFM - update the set of TFMs where we test for ref structs
+#endif
+
         [Fact]
         public void PropertyHelper_DoesNotFindSetOnlyProperties()
         {
@@ -718,6 +734,22 @@ private class Static
             public int Prop5 { get; set; }
         }
 
+#if NETSTANDARD || NETCOREAPP
+        private class RefStructProperties
+        {
+            public Span<bool> Span => throw new NotImplementedException();
+            public MyRefStruct UserDefined => throw new NotImplementedException();
+
+            public int Prop5 { get; set; }
+        }
+
+        private readonly ref struct MyRefStruct
+        {
+        }
+#elif NET46 || NET461
+#else
+#error Unknown TFM - update the set of TFMs where we test for ref structs
+#endif
         private struct MyProperties
         {
             public int IntProp { get; set; }