private static bool CanCastByVarianceToInterfaceOrDelegate(this TypeDesc thisType, TypeDesc otherType, StackOverflowProtect protectInput)
{
if (!thisType.HasSameTypeDefinition(otherType))
{
return(false);
}
var stackOverflowProtectKey = new CastingPair(thisType, otherType);
if (protectInput != null)
{
if (protectInput.Contains(stackOverflowProtectKey))
{
return(false);
}
}
StackOverflowProtect protect = new StackOverflowProtect(stackOverflowProtectKey, protectInput);
Instantiation instantiationThis = thisType.Instantiation;
Instantiation instantiationTarget = otherType.Instantiation;
Instantiation instantiationOpen = thisType.GetTypeDefinition().Instantiation;
Debug.Assert(instantiationThis.Length == instantiationTarget.Length &&
instantiationThis.Length == instantiationOpen.Length);
for (int i = 0; i < instantiationThis.Length; i++)
{
TypeDesc arg = instantiationThis[i];
TypeDesc targetArg = instantiationTarget[i];
if (arg != targetArg)
{
GenericParameterDesc openArgType = (GenericParameterDesc)instantiationOpen[i];
switch (openArgType.Variance)
{
case GenericVariance.Covariant:
if (!arg.IsBoxedAndCanCastTo(targetArg, protect))
{
return(false);
}
break;
case GenericVariance.Contravariant:
if (!targetArg.IsBoxedAndCanCastTo(arg, protect))
{
return(false);
}
break;
default:
// non-variant
Debug.Assert(openArgType.Variance == GenericVariance.None);
return(false);
}
}
}
return(true);
}
