Expression LiftOperand (ResolveContext rc, Expression expr)
{
TypeSpec type;
if (expr.IsNull) {
type = Left.IsNull ? Right.Type : Left.Type;
} else {
type = expr.Type;
}
if (!type.IsNullableType)
type = NullableInfo.MakeType (rc.Module, type);
return Wrap.Create (expr, type);
}