Don't call HasCustomModifier when the argument type is something norm…

…alized to ELEMENT_TYPE_PTR or ELEMENT_TYPE_BYREF (#108610)

src/coreclr/vm/jitinterface.cpp

@@ -9539,7 +9539,17 @@ CorInfoTypeWithMod CEEInfo::getArgType (
         FALLTHROUGH;
 
     case ELEMENT_TYPE_BYREF:
-        IfFailThrow(ptr.GetElemType(NULL));
+        // PeekElemTypeClosed above normalized ELEMENT_TYPE_INTERNAL back to the underlying type handle's signature representation.
+        // This normalization can also occur for generic instantiatations, but we don't support pointer or byref types
+        // as generic arguments.
+        // All of the element types that can be normalized above can't have custom modifiers embedded in this location,
+        // so we don't need to check for them here.
+        CorElementType nonNormalizedType;
+        IfFailThrow(ptr.GetElemType(&nonNormalizedType));
+        if (type != nonNormalizedType)
+        {
+            break;
+        }
         if (ptr.HasCustomModifier(pModule, "Microsoft.VisualC.NeedsCopyConstructorModifier", ELEMENT_TYPE_CMOD_REQD) ||
             ptr.HasCustomModifier(pModule, "System.Runtime.CompilerServices.IsCopyConstructed", ELEMENT_TYPE_CMOD_REQD))
         {