[System.Reflection] Make GetFieldOffset method virtual to fix issue with custom FieldInfo type.

4 files changed, 40 insertions, 11 deletions

diff --git a/mcs/class/corlib/System.Reflection.Emit/FieldOnTypeBuilderInst.cs b/mcs/class/corlib/System.Reflection.Emit/FieldOnTypeBuilderInst.cs
index c33e0f7f77b..9de89b1e2b8 100644
--- a/mcs/class/corlib/System.Reflection.Emit/FieldOnTypeBuilderInst.cs
+++ b/mcs/class/corlib/System.Reflection.Emit/FieldOnTypeBuilderInst.cs
@@ -128,11 +128,6 @@ namespace System.Reflection.Emit
 			throw new NotSupportedException ();
 		}
 
-        internal override int GetFieldOffset ()
-        {
-            throw new SystemException ("This method should not be called");
-        }
-
 		// Called from the runtime to return the corresponding finished FieldInfo object
 		internal FieldInfo RuntimeResolve () {
 			var type = instantiation.RuntimeResolve ();
diff --git a/mcs/class/corlib/System.Reflection/FieldInfo.cs b/mcs/class/corlib/System.Reflection/FieldInfo.cs
index 1a7528099da..747b021c9bc 100644
--- a/mcs/class/corlib/System.Reflection/FieldInfo.cs
+++ b/mcs/class/corlib/System.Reflection/FieldInfo.cs
@@ -59,7 +59,10 @@ namespace System.Reflection {
 			return fi;
 		}
 
-		internal abstract int GetFieldOffset ();
+		internal virtual int GetFieldOffset ()
+		{
+			throw new SystemException ("This method should not be called");
+		}
 
 		[MethodImplAttribute(MethodImplOptions.InternalCall)]
 		private extern MarshalAsAttribute get_marshal_info ();
diff --git a/mcs/class/corlib/Test/System.Reflection/FieldInfoTest.cs b/mcs/class/corlib/Test/System.Reflection/FieldInfoTest.cs
index 62680cc63a4..d21482dd20d 100644
--- a/mcs/class/corlib/Test/System.Reflection/FieldInfoTest.cs
+++ b/mcs/class/corlib/Test/System.Reflection/FieldInfoTest.cs
@@ -29,6 +29,7 @@
 //
 
 using System;
+using System.Globalization;
 using System.Threading;
 using System.Reflection;
 #if !MONOTOUCH && !FULL_AOT_RUNTIME
@@ -1463,6 +1464,41 @@ namespace MonoTests.System.Reflection
 		public const FieldInfoTest object_field = null;
 		public int non_const_field;
 
+		class FieldInfoWrapper : FieldInfo
+		{
+			private FieldInfo fieldInfo;
+
+			public FieldInfoWrapper (FieldInfo fieldInfo)
+			{
+				this.fieldInfo = fieldInfo;
+			}
+
+			public override FieldAttributes Attributes => fieldInfo.Attributes;
+			public override Type DeclaringType => fieldInfo.DeclaringType;
+			public override RuntimeFieldHandle FieldHandle => fieldInfo.FieldHandle;
+			public override Type FieldType => fieldInfo.FieldType;
+			public override string Name => fieldInfo.Name;
+			public override Type ReflectedType => fieldInfo.ReflectedType;
+			
+			public override object[] GetCustomAttributes (bool inherit) => fieldInfo.GetCustomAttributes (inherit); 
+			public override object[] GetCustomAttributes (Type attributeType, bool inherit) => fieldInfo.GetCustomAttributes (attributeType, inherit);
+			public override object GetValue (object obj) => fieldInfo.GetValue (obj);
+			public override bool IsDefined (Type attributeType, bool inherit) => fieldInfo.IsDefined (attributeType, inherit);
+			public override void SetValue (object obj, object value, BindingFlags invokeAttr, Binder binder, CultureInfo culture) =>
+				fieldInfo.SetValue (obj, value, invokeAttr, binder, culture);
+		}
+
+		[Test]
+		public void CustomFieldInfo () 
+		{
+			var fieldInfoWrapper = new FieldInfoWrapper (GetType ().GetField (nameof (non_const_field)));
+			MethodInfo method = typeof (FieldInfoWrapper).GetMethod ("GetFieldOffset", BindingFlags.NonPublic | BindingFlags.Instance);
+			Assert.IsNotNull (method);
+			Assert.IsTrue (method.IsVirtual);
+
+			var ex = Assert.Catch<Exception> (() => method.Invoke (fieldInfoWrapper, new object[] {}));
+			Assert.IsTrue (ex.InnerException is SystemException);
+		}
 	}
 
 	// We do not refernece the field, that is expected
diff --git a/mcs/class/referencesource/mscorlib/system/runtime/serialization/serializationfieldinfo.cs b/mcs/class/referencesource/mscorlib/system/runtime/serialization/serializationfieldinfo.cs
index fccc00284c5..4281cdbd257 100644
--- a/mcs/class/referencesource/mscorlib/system/runtime/serialization/serializationfieldinfo.cs
+++ b/mcs/class/referencesource/mscorlib/system/runtime/serialization/serializationfieldinfo.cs
@@ -88,11 +88,6 @@ namespace System.Runtime.Serialization {
                 return m_field.FieldType;
             }
         }
-
-        internal override int GetFieldOffset ()
-        {
-            throw new SystemException ("This method should not be called");
-        }
         
         public override Object GetValue(Object obj) {
             return m_field.GetValue(obj);