Improve diagnosability of Expression.Lambda(Expression.Constant(123)).Compile().GetMethodInfo()

Entity framework would like to inspect the MethodInfo obtained from a delegate that points to the LINQ expression interpreter. This will currently throw a very unhelpful exception that makes it look like we're missing metadata - when in fact, we're missing a feature.

EF will ship with a workaround in their 2.0.1 release, but if anyone tries with 2.0.0 (or hits this in any other way), let's give them something more diagnosable.

[tfs-changeset: 1670903]

2 files changed, 13 insertions, 3 deletions

diff --git a/src/System.Private.Reflection.Execution/src/Internal/Reflection/Extensions/NonPortable/DelegateMethodInfoRetriever.cs b/src/System.Private.Reflection.Execution/src/Internal/Reflection/Extensions/NonPortable/DelegateMethodInfoRetriever.cs
index ed1255ed9..c40196a1c 100644
--- a/src/System.Private.Reflection.Execution/src/Internal/Reflection/Extensions/NonPortable/DelegateMethodInfoRetriever.cs
+++ b/src/System.Private.Reflection.Execution/src/Internal/Reflection/Extensions/NonPortable/DelegateMethodInfoRetriever.cs
@@ -24,9 +24,16 @@ namespace Internal.Reflection.Extensions.NonPortable
                 throw new ArgumentException();
             Delegate[] invokeList = del.GetInvocationList();
             del = invokeList[invokeList.Length - 1];
-            RuntimeTypeHandle typeOfFirstParameterIfInstanceDelegate;
-            bool isOpenResolver;
-            IntPtr originalLdFtnResult = RuntimeAugments.GetDelegateLdFtnResult(del, out typeOfFirstParameterIfInstanceDelegate, out isOpenResolver);
+            IntPtr originalLdFtnResult = RuntimeAugments.GetDelegateLdFtnResult(del, out RuntimeTypeHandle typeOfFirstParameterIfInstanceDelegate, out bool isOpenResolver, out bool isInterpreterEntrypoint);
+
+            if (isInterpreterEntrypoint)
+            {
+                // This is a special kind of delegate where the invoke method is "ObjectArrayThunk". Typically,
+                // this will be a delegate that points the the LINQ Expression interpreter. We could manufacture
+                // a MethodInfo based on the delegate's Invoke signature, but let's just throw for now.
+                throw new PlatformNotSupportedException(SR.DelegateGetMethodInfo_ObjectArrayDelegate);
+            }
+
             if (originalLdFtnResult == (IntPtr)0)
                 return null;
 
diff --git a/src/System.Private.Reflection.Execution/src/Resources/Strings.resx b/src/System.Private.Reflection.Execution/src/Resources/Strings.resx
index e4e0e5324..b64eab36f 100644
--- a/src/System.Private.Reflection.Execution/src/Resources/Strings.resx
+++ b/src/System.Private.Reflection.Execution/src/Resources/Strings.resx
@@ -237,4 +237,7 @@
   <data name="DelegateGetMethodInfo_NoInstantiation" xml:space="preserve">
     <value>Cannot retrieve a MethodInfo for this delegate because the necessary generic instantiation was not metadata-enabled. For more information, please visit http://go.microsoft.com/fwlink/?LinkID=616868</value>
   </data>
+  <data name="DelegateGetMethodInfo_ObjectArrayDelegate" xml:space="preserve">
+    <value>Cannot retrieve a MethodInfo for this delegate because the delegate target is an interpreted LINQ expression.</value>
+  </data>
 </root>