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

…#20991)

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

(https://github.com/dotnet/corefx/issues/19895)

Make Microsoft.CSharp use the the real HasMetadataDefinitionAs()
api if it exists on the running framework. Since this library
is built on netstandard, it still needs to fall back on its
emulation on older frameworks.

Actual removal of the ActiveIssue will have to wait until
the new System.Runtime reference assembly propagates to
the Project N tree and the new api becomes reflectable.

* Merge the lightup checks.

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>