Step 1 of fix for disabled System.Dynamic.Runtime test on ILC

src/Microsoft.CSharp/src/Microsoft/CSharp/RuntimeBinder/RuntimeBinderExtensions.cs

@@ -240,8 +240,32 @@ private static bool IsTypeParameterEquivalentToTypeInst(this Type typeParam, Typ
             {
                 try
                 {
-                    // See if MetadataToken property is available.
                     Type memberInfo = typeof(MemberInfo);
+
+                    // First, try the actual API. (Post .NetCore 2.0) The api is the only one that gets it completely right on frameworks without MetadataToken.
+                    MethodInfo apiMethod = memberInfo.GetMethod(
+                        "HasSameMetadataDefinitionAs",
+                        BindingFlags.Public | BindingFlags.Instance | BindingFlags.DeclaredOnly | BindingFlags.ExactBinding,
+                        binder: null,
+                        types: new Type[] { typeof(MemberInfo) },
+                        modifiers: null);
+                    if (apiMethod != null)
+                    {
+                        Func<MemberInfo, MemberInfo, bool> apiDelegate = (Func<MemberInfo, MemberInfo, bool>)(apiMethod.CreateDelegate(typeof(Func<MemberInfo, MemberInfo, bool>)));
+                        try
+                        {
+                            bool result = apiDelegate(m1, m2);
+                            // it worked, so publish it
+                            s_MemberEquivalence = apiDelegate;
+                            return result;
+                        }
+                        catch
+                        {
+                            // Api found but apparently stubbed as not supported. Continue on to the next fallback...
+                        }
+                    }
+
+                    // See if MetadataToken property is available.
                     PropertyInfo property = memberInfo.GetProperty("MetadataToken", typeof(int), Array.Empty<Type>());
 
                     if ((object)property != null && property.CanRead)

src/Microsoft.CSharp/src/Resources/Microsoft.CSharp.rd.xml

@@ -82,6 +82,11 @@
         </Type>
         <Type Name="Object" Dynamic="Required Public" />
       </Namespace>
+      <Namespace Name="System.Reflection">
+        <Type Name="MemberInfo">
+          <Method Name="HasSameMetadataDefinitionAs" Dynamic="Required"/>
+        </Type>
+      </Namespace>
     </Assembly>
 
     <Assembly Name="System.Linq.Expressions">
@@ -95,4 +100,4 @@
       <Type Name="System.Reflection.Missing" Dynamic="Required All" />
     </Assembly>
   </Library>
-</Directives>
+</Directives>