From 5c55368c8946b8a0c1752a4c96e1f35c583c2087 Mon Sep 17 00:00:00 2001
From: Tomas <trylek@microsoft.com>
Date: Wed, 21 Apr 2021 22:17:53 +0200
Subject: [PATCH] First version of method resolution - Scenario1-5 passing

---
 src/coreclr/vm/methodtable.cpp | 89 +++++++++++++++++++++++++++++++++-
 src/coreclr/vm/methodtable.h   |  4 ++
 2 files changed, 92 insertions(+), 1 deletion(-)

diff --git a/src/coreclr/vm/methodtable.cpp b/src/coreclr/vm/methodtable.cpp
index 6e9d8288d8f444..747831bb73642a 100644
--- a/src/coreclr/vm/methodtable.cpp
+++ b/src/coreclr/vm/methodtable.cpp
@@ -9175,10 +9175,97 @@ MethodDesc *MethodTable::GetDefaultConstructor(BOOL forceBoxedEntryPoint /* = FA
 MethodDesc *
 MethodTable::ResolveVirtualStaticMethod(MethodDesc* pInterfaceMD)
 {
-    // TODO
+    for (MethodTable* pMT = this; pMT != nullptr; pMT = pMT->GetParentMethodTable())
+    {
+        MethodDesc* pMD = pMT->TryResolveVirtualStaticMethodOnThisType(pInterfaceMD);
+        if (pMD != nullptr)
+        {
+            return pMD;
+        }
+    }
     COMPlusThrow(kTypeLoadException, E_NOTIMPL);
 }
 
+//==========================================================================================
+// Try to locate the appropriate MethodImpl matching a given interface static virtual method.
+// Returns nullptr on failure.
+MethodDesc*
+MethodTable::TryResolveVirtualStaticMethodOnThisType(MethodDesc* pInterfaceMD)
+{
+    HRESULT hr = S_OK;
+    IMDInternalImport* pMDInternalImport = GetMDImport();
+    HENUMInternalMethodImplHolder hEnumMethodImpl(pMDInternalImport);
+    hr = hEnumMethodImpl.EnumMethodImplInitNoThrow(GetCl());
+
+    if (FAILED(hr))
+    {
+        COMPlusThrow(kTypeLoadException, hr);
+    }
+
+    // This gets the count out of the metadata interface.
+    uint32_t dwNumberMethodImpls = hEnumMethodImpl.EnumMethodImplGetCount();
+
+    // Iterate through each MethodImpl declared on this class
+    for (uint32_t i = 0; i < dwNumberMethodImpls; i++)
+    {
+        mdToken methodBody;
+        mdToken methodDecl;
+        hr = hEnumMethodImpl.EnumMethodImplNext(&methodBody, &methodDecl);
+        if (FAILED(hr))
+        {
+            COMPlusThrow(kTypeLoadException, hr);
+        }
+        if (hr == S_FALSE)
+        {
+            // In the odd case that the enumerator fails before we've reached the total reported
+            // entries, let's reset the count and just break out. (Should we throw?)
+            break;
+        }
+        mdToken tkParent;
+        hr = pMDInternalImport->GetParentToken(methodDecl, &tkParent);
+        if (FAILED(hr))
+        {
+            COMPlusThrow(kTypeLoadException, hr);
+        }
+        MethodTable *pInterfaceMT = ClassLoader::LoadTypeDefOrRefOrSpecThrowing(
+            GetModule(),
+            tkParent,
+            NULL /*SigTypeContext*/)
+            .GetMethodTable();
+        if (pInterfaceMT != pInterfaceMD->GetMethodTable())
+        {
+            continue;
+        }
+        MethodDesc *pMethodDecl = MemberLoader::GetMethodDescFromMemberDefOrRefOrSpec(
+            GetModule(),
+            methodDecl,
+            NULL /*SigTypeContext*/,
+            /* strictMetadataChecks */ FALSE,
+            /* allowInstParam */ FALSE);
+        if (pMethodDecl == nullptr)
+        {
+            COMPlusThrow(kTypeLoadException, E_FAIL);
+        }
+        if (pMethodDecl != pInterfaceMD)
+        {
+            continue;
+        }
+        MethodDesc *pMethodImpl = MemberLoader::GetMethodDescFromMemberDefOrRefOrSpec(
+            GetModule(),
+            methodBody,
+            NULL /*SigTypeContext*/,
+            /* strictMetadataChecks */ FALSE,
+            /* allowInstParam */ FALSE);
+        if (pMethodImpl == nullptr)
+        {
+            COMPlusThrow(kTypeLoadException, E_FAIL);
+        }
+        return pMethodImpl;
+    }
+
+    return nullptr;
+}
+
 //==========================================================================================
 // Finds the (non-unboxing) MethodDesc that implements the interface method pInterfaceMD.
 //
diff --git a/src/coreclr/vm/methodtable.h b/src/coreclr/vm/methodtable.h
index d5984745910c36..b6abc43722bdd4 100644
--- a/src/coreclr/vm/methodtable.h
+++ b/src/coreclr/vm/methodtable.h
@@ -2395,6 +2395,10 @@ class MethodTable
     // when it comes to dispatching pItfMT methods.
     BOOL HasSameInterfaceImplementationAsParent(MethodTable *pItfMT, MethodTable *pParentMT);
 
+    // Try to resolve a given static virtual method override on this type. Return nullptr
+    // when not found.
+    MethodDesc *TryResolveVirtualStaticMethodOnThisType(MethodDesc* pInterfaceMD);
+
 public:
     static MethodDesc *MapMethodDeclToMethodImpl(MethodDesc *pMDDecl);