Runtime support for upcoming .NET Core WinRT Host (#23402)

* First pass at adding winrt host entry-point.

* There's no way to specify HResult-swapping on a function called via hosted-interop so just return the HResult instead.

* Use the WindowsRuntimeMarshal class to create the activation factory and initialize it.

* Implement loading the dependent assemblies of a WinRT assembly into an isolated load context.

* PR Feedback.

* Fail to get the activation factory if the found type is not a managed type exported from a winmd.

* Rearrange parameters based on PR feedback.

* Remove unneeded include.

* Make ActivationFactoryLoader internal.

* Fix null-ref in WinRT-dependent-assembly loading

* Remove extraneous "System."

1 files changed, 11 insertions, 1 deletions

diff --git a/src/vm/assemblyspec.cpp b/src/vm/assemblyspec.cpp
index a2323afe6b..a044456ff9 100644
--- a/src/vm/assemblyspec.cpp
+++ b/src/vm/assemblyspec.cpp
@@ -870,8 +870,18 @@ ICLRPrivBinder* AssemblySpec::GetBindingContextFromParentAssembly(AppDomain *pDo
             // types being referenced from Windows.Foundation.Winmd).
             //
             // If the AssemblySpec does not correspond to WinRT type but our parent assembly binder is a WinRT binder,
-            // then such an assembly will not be found by the binder. In such a case, we reset our binder reference.
+            // then such an assembly will not be found by the binder.
+            // In such a case, the parent binder should be the fallback binder for the WinRT assembly if one exists.
+            ICLRPrivBinder* pParentWinRTBinder = pParentAssemblyBinder;
             pParentAssemblyBinder = NULL;
+            ReleaseHolder<ICLRPrivAssemblyID_WinRT> assembly;
+            if (SUCCEEDED(pParentWinRTBinder->QueryInterface<ICLRPrivAssemblyID_WinRT>(&assembly)))
+            {
+                pParentAssemblyBinder = dac_cast<PTR_CLRPrivAssemblyWinRT>(assembly.GetValue())->GetFallbackBinder();
+
+                // The fallback binder should not be a WinRT binder.
+                _ASSERTE(!AreSameBinderInstance(pWinRTBinder, pParentAssemblyBinder));
+            }
         }
     }
 #endif // defined(FEATURE_COMINTEROP)