[Re-Proposal] Type only Unions

[ksluder (Kyle Sluder)]

@Pampel

If I'm writing a finance application, I don't want someone passing a Double representing a monetary amount to a parameter expecting a Double interest-rate. DebitTransaction and CreditTransaction might both have a amount: Double and reference: String but they mean very different things.

There is actually a different, long-desired language feature that directly addresses this use case: newtypes.