private static DefaultInterfaceMethodResolution ResolveInterfaceMethodToDefaultImplementationOnType(MethodDesc interfaceMethod, MetadataType currentType, out MethodDesc impl)
{
TypeDesc interfaceMethodOwningType = interfaceMethod.OwningType;
MetadataType mostSpecificInterface = null;
bool diamondCase = false;
impl = null;
MethodDesc interfaceMethodDefinition = interfaceMethod.GetMethodDefinition();
DefType[] consideredInterfaces;
if (!currentType.IsInterface)
{
// If this is not an interface, only things on the interface list could provide
// default implementations.
consideredInterfaces = currentType.RuntimeInterfaces;
}
else
{
// If we're asking about an interface, include the interface in the list.
consideredInterfaces = new DefType[currentType.RuntimeInterfaces.Length + 1];
Array.Copy(currentType.RuntimeInterfaces, consideredInterfaces, currentType.RuntimeInterfaces.Length);
consideredInterfaces[consideredInterfaces.Length - 1] = (DefType)currentType.InstantiateAsOpen();
}
foreach (MetadataType runtimeInterface in consideredInterfaces)
{
if (runtimeInterface == interfaceMethodOwningType)
{
// Also consider the default interface method implementation on the interface itself
// if we don't have anything else yet
if (mostSpecificInterface == null && !interfaceMethod.IsAbstract)
{
mostSpecificInterface = runtimeInterface;
impl = interfaceMethodDefinition;
}
}
else if (Array.IndexOf(runtimeInterface.RuntimeInterfaces, interfaceMethodOwningType) != -1)
{
// This interface might provide a default implementation
MethodImplRecord[] possibleImpls = runtimeInterface.FindMethodsImplWithMatchingDeclName(interfaceMethod.Name);
if (possibleImpls != null)
{
foreach (MethodImplRecord implRecord in possibleImpls)
{
if (implRecord.Decl == interfaceMethodDefinition)
{
// This interface provides a default implementation.
// Is it also most specific?
if (mostSpecificInterface == null || Array.IndexOf(runtimeInterface.RuntimeInterfaces, mostSpecificInterface) != -1)
{
mostSpecificInterface = runtimeInterface;
impl = implRecord.Body;
diamondCase = false;
}
else if (Array.IndexOf(mostSpecificInterface.RuntimeInterfaces, runtimeInterface) == -1)
{
diamondCase = true;
}
break;
}
}
}
}
}
if (diamondCase)
{
impl = null;
return(DefaultInterfaceMethodResolution.Diamond);
}
else if (impl == null)
{
return(DefaultInterfaceMethodResolution.None);
}
else if (impl.IsAbstract)
{
impl = null;
return(DefaultInterfaceMethodResolution.Reabstraction);
}
if (interfaceMethod != interfaceMethodDefinition)
{
impl = impl.MakeInstantiatedMethod(interfaceMethod.Instantiation);
}
return(DefaultInterfaceMethodResolution.DefaultImplementation);
}