The problem with structural/duck typing is that words can mean several things. For example `.run`ning your duck is probably very different from `.run`ning your

The problem with structural/duck typing is that words can mean several things. For example `.run`ning your duck is probably very different from `.run`ning your Thread. I think the Symbol is a way to signal "this is the dispose function whose contract is defined in the JS `using` spec and not some random function that happens to be named that way".