Comment by aatd86
3 months ago
I think what they meant is that it is not purely parametric polymorphism. Not that parametricity is broken.
3 months ago
I think what they meant is that it is not purely parametric polymorphism. Not that parametricity is broken.
Hmm, maybe
> most type theories don't enforce full parametricity at runtime
means "sometimes types can appear at run time"? If so it's true, but it's not what I understand by "parametricity".
Not sure, either : Parametric polymorphism is compile time. Adding runtime behaviors is a sort of escape hatch.
Which is fair although necessary. It's not so much a breakage as it is a necessity, since non parametric code may rely on this too.
Or maybe it is about constrained parametricity. In any case this doesn't seem a big issue.