Unify pseudo-attribute code between NativeFormat and Ecma (#4456)

This was following the old layering rules - resulting
in pointless duplication of logic between Native
and Ecma.

As a bonus, this also fixes an edge-case bug.
PreserveSigAttribute is not valid on constructors
and isn't synthesized by the full framework even
if you force that bit on. Project N now matches
that behavior.

22 files changed, 105 insertions, 196 deletions

diff --git a/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionDomain.cs b/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionDomain.cs
index 17ad69dc1..2f1657ed8 100644
--- a/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionDomain.cs
+++ b/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionDomain.cs
@@ -175,17 +175,6 @@ namespace Internal.Reflection.Core.Execution
             }
         }
 
-        //
-        // Get or create a CustomAttributeData object for a specific type and arguments. 
-        //
-        public CustomAttributeData GetCustomAttributeData(Type attributeType, IList<CustomAttributeTypedArgument> constructorArguments, IList<CustomAttributeNamedArgument> namedArguments)
-        {
-            if (!attributeType.IsRuntimeImplemented())
-                throw new InvalidOperationException();
-            RuntimeTypeInfo runtimeAttributeType = attributeType.CastToRuntimeTypeInfo();
-            return new RuntimePseudoCustomAttributeData(runtimeAttributeType, constructorArguments, namedArguments);
-        }
-
         //=======================================================================================
         // This group of methods jointly service the Type.GetTypeFromHandle() path. The caller
         // is responsible for analyzing the RuntimeTypeHandle to figure out which flavor to call.
diff --git a/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs b/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs
index 5d8699ce3..71e8080a2 100644
--- a/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs
+++ b/src/System.Private.Reflection.Core/src/Internal/Reflection/Core/Execution/ExecutionEnvironment.cs
@@ -72,17 +72,6 @@ namespace Internal.Reflection.Core.Execution
         public abstract FieldAccessor TryGetFieldAccessor(MetadataReader reader, RuntimeTypeHandle declaringTypeHandle, RuntimeTypeHandle fieldTypeHandle, FieldHandle fieldHandle);
 
         //==============================================================================================
-        // Pseudo Custom Attributes
-        //==============================================================================================
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, ScopeDefinitionHandle scopeDefinitionHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, TypeDefinitionHandle typeDefinitionHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, MethodHandle methodHandle, TypeDefinitionHandle declaringTypeHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, ParameterHandle parameterHandle, MethodHandle declaringMethodHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, FieldHandle fieldHandle, TypeDefinitionHandle declaringTypeHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, PropertyHandle propertyHandle, TypeDefinitionHandle declaringTypeHandle);
-        public abstract IEnumerable<CustomAttributeData> GetPseudoCustomAttributes(MetadataReader reader, EventHandle eventHandle, TypeDefinitionHandle declaringTypeHandle);
-
-        //==============================================================================================
         // RuntimeMethodHandle and RuntimeFieldHandle support.
         //==============================================================================================
         public abstract bool TryGetMethodFromHandle(RuntimeMethodHandle runtimeMethodHandle, out RuntimeTypeHandle declaringTypeHandle, out QMethodDefinition methodHandle, out RuntimeTypeHandle[] genericMethodTypeArgumentHandles);
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/Assemblies/NativeFormat/NativeFormatRuntimeAssembly.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/Assemblies/NativeFormat/NativeFormatRuntimeAssembly.cs
index 317e44ebe..e3d7e2ec7 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/Assemblies/NativeFormat/NativeFormatRuntimeAssembly.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/Assemblies/NativeFormat/NativeFormatRuntimeAssembly.cs
@@ -46,9 +46,6 @@ namespace System.Reflection.Runtime.Assemblies.NativeFormat
                 {
                     foreach (CustomAttributeData cad in RuntimeCustomAttributeData.GetCustomAttributes(scope.Reader, scope.ScopeDefinition.CustomAttributes))
                         yield return cad;
-
-                    foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(scope.Reader, scope.Handle))
-                        yield return cad;
                 }
             }
         }
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/CustomAttributes/RuntimePseudoCustomAttributeData.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/CustomAttributes/RuntimePseudoCustomAttributeData.cs
index bc6bfb41a..6734900d7 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/CustomAttributes/RuntimePseudoCustomAttributeData.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/CustomAttributes/RuntimePseudoCustomAttributeData.cs
@@ -17,7 +17,7 @@ namespace System.Reflection.Runtime.CustomAttributes
     //
     internal sealed class RuntimePseudoCustomAttributeData : RuntimeCustomAttributeData
     {
-        public RuntimePseudoCustomAttributeData(RuntimeTypeInfo attributeType, IList<CustomAttributeTypedArgument> constructorArguments, IList<CustomAttributeNamedArgument> namedArguments)
+        public RuntimePseudoCustomAttributeData(Type attributeType, IList<CustomAttributeTypedArgument> constructorArguments, IList<CustomAttributeNamedArgument> namedArguments)
         {
             _attributeType = attributeType;
             if (constructorArguments == null)
@@ -74,7 +74,7 @@ namespace System.Reflection.Runtime.CustomAttributes
 
         // Equals/GetHashCode no need to override (they just implement reference equality but desktop never unified these things.)
 
-        private readonly RuntimeTypeInfo _attributeType;
+        private readonly Type _attributeType;
         private readonly ReadOnlyCollection<CustomAttributeTypedArgument> _constructorArguments;
         private readonly ReadOnlyCollection<CustomAttributeNamedArgument> _namedArguments;
     }
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/EcmaFormat/EcmaFormatRuntimeEventInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/EcmaFormat/EcmaFormatRuntimeEventInfo.cs
index 87820be0a..7c0d038e3 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/EcmaFormat/EcmaFormatRuntimeEventInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/EcmaFormat/EcmaFormatRuntimeEventInfo.cs
@@ -108,8 +108,7 @@ namespace System.Reflection.Runtime.EventInfos.EcmaFormat
                     ReflectionTrace.EventInfo_CustomAttributes(this);
 #endif
 
-                foreach (CustomAttributeData cad in RuntimeCustomAttributeData.GetCustomAttributes(_reader, _event.GetCustomAttributes()))
-                    yield return cad;
+                return RuntimeCustomAttributeData.GetCustomAttributes(_reader, _event.GetCustomAttributes());
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/NativeFormat/NativeFormatRuntimeEventInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/NativeFormat/NativeFormatRuntimeEventInfo.cs
index f738c4e3c..dbcd8ea57 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/NativeFormat/NativeFormatRuntimeEventInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/EventInfos/NativeFormat/NativeFormatRuntimeEventInfo.cs
@@ -104,10 +104,7 @@ namespace System.Reflection.Runtime.EventInfos.NativeFormat
                     ReflectionTrace.EventInfo_CustomAttributes(this);
 #endif
 
-                foreach (CustomAttributeData cad in RuntimeCustomAttributeData.GetCustomAttributes(_reader, _event.CustomAttributes))
-                    yield return cad;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(_reader, _eventHandle, _definingTypeInfo.TypeDefinitionHandle))
-                    yield return cad;
+                return RuntimeCustomAttributeData.GetCustomAttributes(_reader, _event.CustomAttributes);
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/EcmaFormat/EcmaFormatRuntimeFieldInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/EcmaFormat/EcmaFormatRuntimeFieldInfo.cs
index c0a1ed041..cc5f49247 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/EcmaFormat/EcmaFormatRuntimeFieldInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/EcmaFormat/EcmaFormatRuntimeFieldInfo.cs
@@ -64,28 +64,6 @@ namespace System.Reflection.Runtime.FieldInfos.EcmaFormat
             _field = _reader.GetFieldDefinition(fieldHandle);
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-#if ENABLE_REFLECTION_TRACE
-                if (ReflectionTrace.Enabled)
-                    ReflectionTrace.FieldInfo_CustomAttributes(this);
-#endif
-
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _field.GetCustomAttributes());
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-                
-                if (_definingTypeInfo.IsExplicitLayout)
-                {
-                    int offset = _field.GetOffset();
-                    CustomAttributeTypedArgument offsetArgument = new CustomAttributeTypedArgument(typeof(Int32), offset);
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(System.Runtime.InteropServices.FieldOffsetAttribute), new CustomAttributeTypedArgument[] { offsetArgument }, null);
-                }
-            }
-        }
-
         public sealed override FieldAttributes Attributes
         {
             get
@@ -204,6 +182,10 @@ namespace System.Reflection.Runtime.FieldInfos.EcmaFormat
 
         protected sealed override RuntimeTypeInfo DefiningType { get { return _definingTypeInfo; } }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _field.GetCustomAttributes());
+
+        protected sealed override int ExplicitLayoutFieldOffsetData => _field.GetOffset();
+
         private readonly EcmaFormatRuntimeNamedTypeInfo _definingTypeInfo;
         private readonly FieldDefinitionHandle _fieldHandle;
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/NativeFormat/NativeFormatRuntimeFieldInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/NativeFormat/NativeFormatRuntimeFieldInfo.cs
index fdc97ec4d..38476fb18 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/NativeFormat/NativeFormatRuntimeFieldInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/NativeFormat/NativeFormatRuntimeFieldInfo.cs
@@ -61,23 +61,6 @@ namespace System.Reflection.Runtime.FieldInfos.NativeFormat
             _field = fieldHandle.GetField(_reader);
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-#if ENABLE_REFLECTION_TRACE
-                if (ReflectionTrace.Enabled)
-                    ReflectionTrace.FieldInfo_CustomAttributes(this);
-#endif
-
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _field.CustomAttributes);
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(_reader, _fieldHandle, _definingTypeInfo.TypeDefinitionHandle))
-                    yield return cad;
-            }
-        }
-
         public sealed override FieldAttributes Attributes
         {
             get
@@ -182,6 +165,10 @@ namespace System.Reflection.Runtime.FieldInfos.NativeFormat
 
         protected sealed override RuntimeTypeInfo DefiningType { get { return _definingTypeInfo; } }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _field.CustomAttributes);
+  
+        protected sealed override int ExplicitLayoutFieldOffsetData => (int)(_field.Offset);
+ 
         private Handle FieldTypeHandle => _field.Signature.GetFieldSignature(_reader).Type;
 
         private readonly NativeFormatRuntimeNamedTypeInfo _definingTypeInfo;
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/RuntimeFieldInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/RuntimeFieldInfo.cs
index e5fe2ceab..392f6db9e 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/RuntimeFieldInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/FieldInfos/RuntimeFieldInfo.cs
@@ -7,6 +7,7 @@ using System.Reflection;
 using System.Diagnostics;
 using System.Globalization;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Runtime.CompilerServices;
 
 using System.Reflection.Runtime.General;
@@ -50,6 +51,27 @@ namespace System.Reflection.Runtime.FieldInfos
             _reflectedType = reflectedType;
         }
 
+        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
+        {
+            get
+            {
+#if ENABLE_REFLECTION_TRACE
+                if (ReflectionTrace.Enabled)
+                    ReflectionTrace.FieldInfo_CustomAttributes(this);
+#endif
+
+                foreach (CustomAttributeData cad in TrueCustomAttributes)
+                    yield return cad;
+
+                if (DeclaringType.IsExplicitLayout)
+                {
+                    int offset = ExplicitLayoutFieldOffsetData;
+                    CustomAttributeTypedArgument offsetArgument = new CustomAttributeTypedArgument(typeof(int), offset);
+                    yield return new RuntimePseudoCustomAttributeData(typeof(FieldOffsetAttribute), new CustomAttributeTypedArgument[] { offsetArgument }, null);
+                }
+            }
+        }
+
         public sealed override Type DeclaringType
         {
             get
@@ -182,7 +204,6 @@ namespace System.Reflection.Runtime.FieldInfos
         }
 
         // Types that derive from RuntimeFieldInfo must implement the following public surface area members
-        public abstract override IEnumerable<CustomAttributeData> CustomAttributes { get; }
         public abstract override FieldAttributes Attributes { get; }
         public abstract override int MetadataToken { get; }
         public abstract override String ToString();
@@ -258,6 +279,9 @@ namespace System.Reflection.Runtime.FieldInfos
         /// </summary>
         protected abstract RuntimeTypeInfo DefiningType { get; }
 
+        protected abstract IEnumerable<CustomAttributeData> TrueCustomAttributes { get; }
+        protected abstract int ExplicitLayoutFieldOffsetData { get; }
+
         /// <summary>
         /// Returns the field offset (asserts and throws if not an instance field). Does not include the size of the object header.
         /// </summary>
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/EcmaFormat/EcmaFormatMethodCommon.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/EcmaFormat/EcmaFormatMethodCommon.cs
index e44ba9459..3d697d8ec 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/EcmaFormat/EcmaFormatMethodCommon.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/EcmaFormat/EcmaFormatMethodCommon.cs
@@ -157,19 +157,6 @@ namespace System.Reflection.Runtime.MethodInfos.EcmaFormat
             }
         }
 
-        public IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _method.GetCustomAttributes());
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-
-                if (0 != (_method.ImplAttributes & MethodImplAttributes.PreserveSig))
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(PreserveSigAttribute), null, null);
-            }
-        }
-
         public RuntimeTypeInfo DeclaringType
         {
             get
@@ -317,6 +304,8 @@ namespace System.Reflection.Runtime.MethodInfos.EcmaFormat
             return true;
         }
 
+        public IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _method.GetCustomAttributes());
+
         public override bool Equals(Object obj)
         {
             if (!(obj is EcmaFormatMethodCommon))
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/IRuntimeMethodCommon.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/IRuntimeMethodCommon.cs
index df1de5e97..68c458102 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/IRuntimeMethodCommon.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/IRuntimeMethodCommon.cs
@@ -26,7 +26,6 @@ namespace System.Reflection.Runtime.MethodInfos
         CallingConventions CallingConvention { get; }
 
         RuntimeTypeInfo ContextTypeInfo { get; }
-        IEnumerable<CustomAttributeData> CustomAttributes { get; }
         RuntimeTypeInfo DeclaringType { get; }
         RuntimeNamedTypeInfo DefiningTypeInfo { get; }
         MethodImplAttributes MethodImplementationFlags { get; }
@@ -36,6 +35,7 @@ namespace System.Reflection.Runtime.MethodInfos
         /// Return an array of the types of the return value and parameter types.
         /// </summary>
         QSignatureTypeHandle[] QualifiedMethodSignature { get; }
+        IEnumerable<CustomAttributeData> TrueCustomAttributes { get; }
 
         /// <summary>
         /// Parse the metadata that describes parameters, and for each parameter for which there is specific metadata
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/NativeFormat/NativeFormatMethodCommon.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/NativeFormat/NativeFormatMethodCommon.cs
index ba7d93981..dae0a916b 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/NativeFormat/NativeFormatMethodCommon.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/NativeFormat/NativeFormatMethodCommon.cs
@@ -2,9 +2,6 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Text;
-using System.Reflection;
 using System.Diagnostics;
 using System.Collections.Generic;
 using System.Runtime;
@@ -15,7 +12,6 @@ using System.Reflection.Runtime.ParameterInfos;
 using System.Reflection.Runtime.ParameterInfos.NativeFormat;
 using System.Reflection.Runtime.CustomAttributes;
 
-using Internal.Reflection.Core;
 using Internal.Reflection.Core.Execution;
 using Internal.Runtime.CompilerServices;
 using Internal.Runtime.TypeLoader;
@@ -149,18 +145,6 @@ namespace System.Reflection.Runtime.MethodInfos.NativeFormat
             }
         }
 
-        public IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _method.CustomAttributes);
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(_reader, _methodHandle, _definingTypeInfo.TypeDefinitionHandle))
-                    yield return cad;
-            }
-        }
-
         public RuntimeTypeInfo DeclaringType
         {
             get
@@ -317,6 +301,8 @@ namespace System.Reflection.Runtime.MethodInfos.NativeFormat
             return true;
         }
 
+        public IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _method.CustomAttributes);
+
         public override bool Equals(Object obj)
         {
             if (!(obj is NativeFormatMethodCommon))
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimeNamedMethodInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimeNamedMethodInfo.cs
index c158d76f1..f2138c9be 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimeNamedMethodInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimeNamedMethodInfo.cs
@@ -6,9 +6,11 @@ using System;
 using System.Reflection;
 using System.Diagnostics;
 using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Reflection.Runtime.General;
 using System.Reflection.Runtime.TypeInfos;
 using System.Reflection.Runtime.ParameterInfos;
+using System.Reflection.Runtime.CustomAttributes;
 
 using Internal.Reflection.Core.Execution;
 
@@ -80,7 +82,14 @@ namespace System.Reflection.Runtime.MethodInfos
                     ReflectionTrace.MethodBase_CustomAttributes(this);
 #endif
 
-                return _common.CustomAttributes;
+                foreach (CustomAttributeData cad in _common.TrueCustomAttributes)
+                {
+                    yield return cad;
+                }
+
+                MethodImplAttributes implAttributes = _common.MethodImplementationFlags;
+                if (0 != (implAttributes & MethodImplAttributes.PreserveSig))
+                    yield return new RuntimePseudoCustomAttributeData(typeof(PreserveSigAttribute), null, null);
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimePlainConstructorInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimePlainConstructorInfo.cs
index fb5c6a122..a0792d08d 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimePlainConstructorInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/MethodInfos/RuntimePlainConstructorInfo.cs
@@ -71,7 +71,7 @@ namespace System.Reflection.Runtime.MethodInfos
                     ReflectionTrace.MethodBase_CustomAttributes(this);
 #endif
 
-                return _common.CustomAttributes;
+                return _common.TrueCustomAttributes;
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/EcmaFormat/EcmaFormatMethodParameterInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/EcmaFormat/EcmaFormatMethodParameterInfo.cs
index 6fd760eed..71a59d364 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/EcmaFormat/EcmaFormatMethodParameterInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/EcmaFormat/EcmaFormatMethodParameterInfo.cs
@@ -49,24 +49,6 @@ namespace System.Reflection.Runtime.ParameterInfos.EcmaFormat
             }
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(this.Reader, _parameter.GetCustomAttributes());
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-
-                ParameterAttributes attributes = Attributes;
-                if (0 != (attributes & ParameterAttributes.In))
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(InAttribute), null, null);
-                if (0 != (attributes & ParameterAttributes.Out))
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(OutAttribute), null, null);
-                if (0 != (attributes & ParameterAttributes.Optional))
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(OptionalAttribute), null, null);
-            }
-        }
-
         public sealed override String Name
         {
             get
@@ -83,6 +65,8 @@ namespace System.Reflection.Runtime.ParameterInfos.EcmaFormat
             }
         }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(this.Reader, _parameter.GetCustomAttributes());
+
         protected sealed override bool GetDefaultValueIfAvailable(bool raw, out object defaultValue)
         {
             return DefaultValueProcessing.GetDefaultValueIfAny(Reader, ref _parameter, this, raw, out defaultValue);
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/NativeFormat/NativeFormatMethodParameterInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/NativeFormat/NativeFormatMethodParameterInfo.cs
index 4daadc890..8ed4f11b1 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/NativeFormat/NativeFormatMethodParameterInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/NativeFormat/NativeFormatMethodParameterInfo.cs
@@ -47,19 +47,6 @@ namespace System.Reflection.Runtime.ParameterInfos.NativeFormat
             }
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(this.Reader, _parameter.CustomAttributes);
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-                MethodHandle declaringMethodHandle = _methodHandle;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(this.Reader, _parameterHandle, declaringMethodHandle))
-                    yield return cad;
-            }
-        }
-
         public sealed override String Name
         {
             get
@@ -76,6 +63,8 @@ namespace System.Reflection.Runtime.ParameterInfos.NativeFormat
             }
         }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(this.Reader, _parameter.CustomAttributes);
+
         protected sealed override bool GetDefaultValueIfAvailable(bool raw, out object defaultValue)
         {
             return DefaultValueParser.GetDefaultValueIfAny(Reader, _parameter.DefaultValue, ParameterType, CustomAttributes, raw, out defaultValue);
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/RuntimeFatMethodParameterInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/RuntimeFatMethodParameterInfo.cs
index bf7dc0c14..57ce50467 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/RuntimeFatMethodParameterInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/ParameterInfos/RuntimeFatMethodParameterInfo.cs
@@ -3,7 +3,10 @@
 // See the LICENSE file in the project root for more information.
 
 using System.Diagnostics;
+using System.Collections.Generic;
+using System.Runtime.InteropServices;
 using System.Reflection.Runtime.General;
+using System.Reflection.Runtime.CustomAttributes;
 
 namespace System.Reflection.Runtime.ParameterInfos
 {
@@ -18,6 +21,25 @@ namespace System.Reflection.Runtime.ParameterInfos
         {
         }
 
+        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
+        {
+            get
+            {
+                foreach (CustomAttributeData cad in TrueCustomAttributes)
+                    yield return cad;
+
+                ParameterAttributes attributes = Attributes;
+                if (0 != (attributes & ParameterAttributes.In))
+                    yield return new RuntimePseudoCustomAttributeData(typeof(InAttribute), null, null);
+                if (0 != (attributes & ParameterAttributes.Out))
+                    yield return new RuntimePseudoCustomAttributeData(typeof(OutAttribute), null, null);
+                if (0 != (attributes & ParameterAttributes.Optional))
+                    yield return new RuntimePseudoCustomAttributeData(typeof(OptionalAttribute), null, null);
+            }
+        }
+
+        protected abstract IEnumerable<CustomAttributeData> TrueCustomAttributes { get; }
+
         public sealed override bool HasDefaultValue => DefaultValueInfo.Item1;
         public sealed override object DefaultValue => DefaultValueInfo.Item2;
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/EcmaFormat/EcmaFormatRuntimePropertyInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/EcmaFormat/EcmaFormatRuntimePropertyInfo.cs
index 47d9ba5f4..e25d3f543 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/EcmaFormat/EcmaFormatRuntimePropertyInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/EcmaFormat/EcmaFormatRuntimePropertyInfo.cs
@@ -79,8 +79,7 @@ namespace System.Reflection.Runtime.PropertyInfos.EcmaFormat
                     ReflectionTrace.PropertyInfo_CustomAttributes(this);
 #endif
 
-                foreach (CustomAttributeData cad in RuntimeCustomAttributeData.GetCustomAttributes(_reader, _property.GetCustomAttributes()))
-                    yield return cad;
+                return RuntimeCustomAttributeData.GetCustomAttributes(_reader, _property.GetCustomAttributes());
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/NativeFormat/NativeFormatRuntimePropertyInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/NativeFormat/NativeFormatRuntimePropertyInfo.cs
index 2606d8174..56c22b86f 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/NativeFormat/NativeFormatRuntimePropertyInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/PropertyInfos/NativeFormat/NativeFormatRuntimePropertyInfo.cs
@@ -79,10 +79,7 @@ namespace System.Reflection.Runtime.PropertyInfos.NativeFormat
                     ReflectionTrace.PropertyInfo_CustomAttributes(this);
 #endif
 
-                foreach (CustomAttributeData cad in RuntimeCustomAttributeData.GetCustomAttributes(_reader, _property.CustomAttributes))
-                    yield return cad;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(_reader, _propertyHandle, _definingTypeInfo.TypeDefinitionHandle))
-                    yield return cad;
+                return RuntimeCustomAttributeData.GetCustomAttributes(_reader, _property.CustomAttributes);
             }
         }
 
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/EcmaFormat/EcmaFormatRuntimeNamedTypeInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/EcmaFormat/EcmaFormatRuntimeNamedTypeInfo.cs
index 0034bac7a..822bfb6f5 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/EcmaFormat/EcmaFormatRuntimeNamedTypeInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/EcmaFormat/EcmaFormatRuntimeNamedTypeInfo.cs
@@ -42,24 +42,6 @@ namespace System.Reflection.Runtime.TypeInfos.EcmaFormat
             }
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-#if ENABLE_REFLECTION_TRACE
-                if (ReflectionTrace.Enabled)
-                    ReflectionTrace.TypeInfo_CustomAttributes(this);
-#endif
-
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _typeDefinition.GetCustomAttributes());
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-
-                if (0 != (_typeDefinition.Attributes & TypeAttributes.Import))
-                    yield return ReflectionCoreExecution.ExecutionDomain.GetCustomAttributeData(typeof(ComImportAttribute), null, null);
-            }
-        }
-
         protected sealed override Guid? ComputeGuidFromCustomAttributes()
         {
             //
@@ -218,6 +200,8 @@ namespace System.Reflection.Runtime.TypeInfos.EcmaFormat
             return name.EscapeTypeNameIdentifier();
         }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _typeDefinition.GetCustomAttributes());
+
         internal sealed override RuntimeTypeInfo[] RuntimeGenericTypeParameters
         {
             get
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/NativeFormat/NativeFormatRuntimeNamedTypeInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/NativeFormat/NativeFormatRuntimeNamedTypeInfo.cs
index cf057083f..9fac5f941 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/NativeFormat/NativeFormatRuntimeNamedTypeInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/NativeFormat/NativeFormatRuntimeNamedTypeInfo.cs
@@ -2,19 +2,14 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
 using System.Text;
 using System.Reflection;
 using System.Diagnostics;
 using System.Collections.Generic;
-using System.Collections.Concurrent;
 using System.Reflection.Runtime.Assemblies;
 using System.Reflection.Runtime.General;
-using System.Reflection.Runtime.MethodInfos;
-using System.Reflection.Runtime.TypeInfos;
 using System.Reflection.Runtime.CustomAttributes;
 
-using Internal.Reflection.Core.Execution;
 using Internal.Reflection.Tracing;
 
 using Internal.Metadata.NativeFormat;
@@ -46,25 +41,6 @@ namespace System.Reflection.Runtime.TypeInfos.NativeFormat
             }
         }
 
-        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
-        {
-            get
-            {
-#if ENABLE_REFLECTION_TRACE
-                if (ReflectionTrace.Enabled)
-                    ReflectionTrace.TypeInfo_CustomAttributes(this);
-#endif
-
-                IEnumerable<CustomAttributeData> customAttributes = RuntimeCustomAttributeData.GetCustomAttributes(_reader, _typeDefinition.CustomAttributes);
-                foreach (CustomAttributeData cad in customAttributes)
-                    yield return cad;
-                foreach (CustomAttributeData cad in ReflectionCoreExecution.ExecutionEnvironment.GetPseudoCustomAttributes(_reader, _typeDefinitionHandle))
-                {
-                    yield return cad;
-                }
-            }
-        }
-
         protected sealed override Guid? ComputeGuidFromCustomAttributes()
         {
             //
@@ -210,6 +186,8 @@ namespace System.Reflection.Runtime.TypeInfos.NativeFormat
             return name.EscapeTypeNameIdentifier();
         }
 
+        protected sealed override IEnumerable<CustomAttributeData> TrueCustomAttributes => RuntimeCustomAttributeData.GetCustomAttributes(_reader, _typeDefinition.CustomAttributes);
+
         internal sealed override RuntimeTypeInfo[] RuntimeGenericTypeParameters
         {
             get
diff --git a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/RuntimeNamedTypeInfo.cs b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/RuntimeNamedTypeInfo.cs
index da34e9714..6f40ed267 100644
--- a/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/RuntimeNamedTypeInfo.cs
+++ b/src/System.Private.Reflection.Core/src/System/Reflection/Runtime/TypeInfos/RuntimeNamedTypeInfo.cs
@@ -2,26 +2,15 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 // See the LICENSE file in the project root for more information.
 
-using System;
-using System.Text;
-using System.Reflection;
 using System.Diagnostics;
 using System.Collections.Generic;
 using System.Collections.Concurrent;
+using System.Runtime.InteropServices;
 using System.Reflection.Runtime.General;
-using System.Reflection.Runtime.TypeInfos;
-using System.Reflection.Runtime.Assemblies;
 using System.Reflection.Runtime.CustomAttributes;
 
-using Internal.LowLevelLinq;
-using Internal.Reflection.Core.Execution;
-
 using Internal.Reflection.Tracing;
 
-using CharSet = System.Runtime.InteropServices.CharSet;
-using LayoutKind = System.Runtime.InteropServices.LayoutKind;
-using StructLayoutAttribute = System.Runtime.InteropServices.StructLayoutAttribute;
-
 namespace System.Reflection.Runtime.TypeInfos
 {
     //
@@ -43,6 +32,23 @@ namespace System.Reflection.Runtime.TypeInfos
             }
         }
 
+        public sealed override IEnumerable<CustomAttributeData> CustomAttributes
+        {
+            get
+            {
+#if ENABLE_REFLECTION_TRACE
+                if (ReflectionTrace.Enabled)
+                    ReflectionTrace.TypeInfo_CustomAttributes(this);
+#endif
+
+                foreach (CustomAttributeData cad in TrueCustomAttributes)
+                    yield return cad;
+
+                if (0 != (Attributes & TypeAttributes.Import))
+                    yield return new RuntimePseudoCustomAttributeData(typeof(ComImportAttribute), null, null);
+            }
+        }
+
         public bool Equals(RuntimeNamedTypeInfo other)
         {
             // RuntimeTypeInfo.Equals(object) is the one that encapsulates our unification strategy so defer to him.
@@ -164,6 +170,8 @@ namespace System.Reflection.Runtime.TypeInfos
             }
         }
 
+        protected abstract IEnumerable<CustomAttributeData> TrueCustomAttributes { get; }
+
         //
         // Returns the anchoring typedef that declares the members that this type wants returned by the Declared*** properties.
         // The Declared*** properties will project the anchoring typedef's members by overriding their DeclaringType property with "this"