Support for arbitrary self-referential static fields on a type (#118413)

- Instead of loading the static field type, use metadata directly to pull the needed info if we can't load the target type.
- Add tests covering various scenarios found by customers in the last year or so
- Remove existing scheme which could handle directly self referential statics
- Defer checking RVA static valuetypes for their field type until a later type loader stage
  - Add VMFLAG for HasRVAStaticFields
- Remove VMFLAG for HasPublicFields, this was found to be unused (its a legacy of an old CAS type loader check which no longer exists)

Fixes #104511

Author: davidwrighton

src/coreclr/vm/class.cpp

@@ -1138,6 +1138,22 @@ void ClassLoader::LoadExactParents(MethodTable* pMT)
         EnsureLoaded(TypeHandle(pMT->GetCanonicalMethodTable()), CLASS_LOAD_EXACTPARENTS);
     }
 
+    if (pMT->GetClass()->HasRVAStaticFields())
+    {
+        ApproxFieldDescIterator fdIterator(pMT, ApproxFieldDescIterator::STATIC_FIELDS);
+        FieldDesc* pFD = NULL;
+        while ((pFD = fdIterator.Next()) != NULL)
+        {
+            if (pFD->IsByValue() && pFD->IsRVA())
+            {
+                if (pFD->GetApproxFieldTypeHandleThrowing().GetMethodTable()->GetClass()->HasFieldsWhichMustBeInited())
+                {
+                    ThrowHR(COR_E_BADIMAGEFORMAT);
+                }
+            }
+        }
+    }
+
     LoadExactParentAndInterfacesTransitively(pMT);
 
     if (pMT->GetClass()->HasVTableMethodImpl())

src/coreclr/vm/class.h

@@ -1317,15 +1317,15 @@ class EEClass // DO NOT CREATE A NEW EEClass USING NEW!
         LIMITED_METHOD_CONTRACT;
         m_VMFlags |= (DWORD)VMFLAG_INLINE_ARRAY;
     }
-    DWORD HasNonPublicFields()
+    DWORD HasRVAStaticFields()
     {
         LIMITED_METHOD_CONTRACT;
-        return (m_VMFlags & VMFLAG_HASNONPUBLICFIELDS);
+        return (m_VMFlags & VMFLAG_HASRVASTATICFIELDS);
     }
-    void SetHasNonPublicFields()
+    void SetHasRVAStaticFields()
     {
         LIMITED_METHOD_CONTRACT;
-        m_VMFlags |= (DWORD)VMFLAG_HASNONPUBLICFIELDS;
+        m_VMFlags |= (DWORD)VMFLAG_HASRVASTATICFIELDS;
     }
     DWORD IsNotTightlyPacked()
     {
@@ -1647,7 +1647,7 @@ class EEClass // DO NOT CREATE A NEW EEClass USING NEW!
 
         VMFLAG_INLINE_ARRAY                    = 0x00010000,
         VMFLAG_NO_GUID                         = 0x00020000,
-        VMFLAG_HASNONPUBLICFIELDS              = 0x00040000,
+        VMFLAG_HASRVASTATICFIELDS              = 0x00040000,
         VMFLAG_HAS_CUSTOM_FIELD_ALIGNMENT      = 0x00080000,
         VMFLAG_CONTAINS_STACK_PTR              = 0x00100000,
         VMFLAG_PREFER_ALIGN8                   = 0x00200000, // Would like to have 8-byte alignment