Check for duplicate types in framework packages

Examine framework packages for any duplicate types.

Author: ericstj

pkg/Microsoft.Private.CoreFx.UAP/Microsoft.Private.CoreFx.UAP.pkgproj

@@ -35,6 +35,8 @@
     <ExcludeFromClosure Include="System.Net" />
     <ExcludeFromClosure Include="System.Transactions" />
 
+    <ExcludeFromDuplicateTypes Include="System.Private.Reflection.Metadata.Ecma335" />
+
     <!-- Permit the following implementation-only assemblies -->
     <ValidatePackageSuppression Condition="'$(PackageTargetRuntime)' != ''" Include="PermitInbox">
       <Value>

pkg/frameworkPackage.targets

@@ -114,6 +114,25 @@
 
   </Target>
 
+  <Target Name="VerifyDuplicateTypes" 
+          DependsOnTargets="GetClosureFiles" 
+          AfterTargets="Build"
+          Inputs="%(ClosureFile.FileSet)"
+          Outputs="batching-on-FileSet-metadata">
+    <ItemGroup>
+      <_dupTypeFileName Include="@(ClosureFile->'%(FileName)')">
+        <Original>%(Identity)</Original>
+      </_dupTypeFileName>
+      <_dupTypeFileNamesFiltered Include="@(_dupTypeFileName)" Exclude="@(ExcludeFromDuplicateTypes)"/>
+      <_dupTypeFileFiltered Include="@(_dupTypeFileNamesFiltered->'%(Original)')"/>
+    </ItemGroup>
+
+    <Message Importance="High" Text="Verifying no duplicate types in $(Id) %(ClosureFile.FileSet) assemblies" />
+    <VerifyTypes Sources="@(_dupTypeFileFiltered)"
+                 IgnoredTypes="@(IgnoredDuplicateType)" />
+
+  </Target>
+
   <Target Name="VerifyNETStandard" 
           DependsOnTargets="GetClosureFiles" 
           AfterTargets="Build"