Quoting Bakul Shah (2018-11-29 22:13:45)
> I doubt go2 will get generics flexible enough for this!
It can actually already pull much of this off, and you don't even need the
contracts part of the draft. E.g:
// Type 'Money' represents a monetary value. The Currency type parameter
// is unused at runtime, but serves to prevent mixing up different
// currencies:
type Money(type Currency) int64
// These types used as the parameter for 'Money'. They are never used as
// values, just as part of this trick with the type system -- because of
// this you'll sometimes hear them referred to as "phantom types".
type USD struct{}
type EUR struct{}
type GBP struct{}
// ...
var m1 Money(USD) = 5
var m2 Money(USD) = 10
var m3 Money(EUR) = 2
m1 + m2 // ok
m2 + m3 // type error: Money(USD) vs. Money(EUR)
-Ian
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