I think I'm missing something. How is nil not an inhabitant?
On Thu, Jun 18, 2020 at 6:48 PM Bryan C. Mills wrote:
>
> On Thu, Jun 18, 2020 at 4:19 PM 'Axel Wagner' via golang-nuts
> wrote:
>>
>> Addendum: In Go, every type needs to be inhabited by at least one value -
>> it's zero value. And
On Thu, Jun 18, 2020 at 4:19 PM 'Axel Wagner' via golang-nuts <
golang-nuts@googlegroups.com> wrote:
> Addendum: In Go, every type needs to be inhabited by at least one value -
> it's zero value. And we already have a type that can take *exactly* one
> value, namely struct{}.
>
That is true, but
The constraint can't be used for phantom types. If C is an interface
with an empty type list and P is given by
type P(type T C) struct{}
you can't instantiate P because no type can satisfy C.
C is not the type with 0 inhabitants: it's a constraint on types that
cannot be satisfied.
I don't
Addendum: In Go, every type needs to be inhabited by at least one value -
it's zero value. And we already have a type that can take *exactly* one
value, namely struct{}.
On Thu, Jun 18, 2020, 22:13 Axel Wagner
wrote:
> These arguments would be more convincing, if Go wouldn't already reject
>
These arguments would be more convincing, if Go wouldn't already reject
interfaces impossible to implement: https://play.golang.org/p/dYm8js26qml
On Thu, Jun 18, 2020, 17:26 Jesper Louis Andersen <
jesper.louis.ander...@gmail.com> wrote:
> It is a type which cannot be inhabited by a term. These
It is a type which cannot be inhabited by a term. These exist and often
have uses. As Bryan wrote they also completes the type lattice, so
rejecting them is often a lot of work for little gain.
If you want examples, look up phantom types, where an uninhabited type is
used as a tag for ensuring
An empty intersection of type lists cannot be instantiated with any actual
type, but if type-list interfaces could eventually be used as run-time
types (as suggested in
https://golang.org/design/go2draft-type-parameters#type-lists-in-interface-types),
then the interface with an empty
On Wed, Jun 17, 2020 at 4:33 PM jimmy frasche wrote:
>
> If I merge the two examples I still get an error
> https://go2goplay.golang.org/p/TNYLDLokGCQ
>
> prog.go2:21:2: int does not satisfy Z (int not found in ⊥)
I think that may be a bug in the type checker, which may not be quite
updated to
I think that second error is a bug. I would expect that case to be the
same as if I wrote a type list that was just int (and hence not the
empty type list).
On Wed, Jun 17, 2020 at 4:33 PM jimmy frasche wrote:
>
> If I merge the two examples I still get an error
>
If I merge the two examples I still get an error
https://go2goplay.golang.org/p/TNYLDLokGCQ
prog.go2:21:2: int does not satisfy Z (int not found in ⊥)
On Wed, Jun 17, 2020 at 4:24 PM Ian Lance Taylor wrote:
>
> On Wed, Jun 17, 2020 at 3:52 PM jimmy frasche wrote:
> >
> > The only case I mean
On Wed, Jun 17, 2020 at 3:52 PM jimmy frasche wrote:
>
> The only case I mean is when the intersection of the type lists is ∅.
> That's easy to check and always wrong afaict.
Unfortunately I don't think it's that simple.
type MyInt int
type I1 interface {
type int
}
type I2 interface {
The only case I mean is when the intersection of the type lists is ∅.
That's easy to check and always wrong afaict.
On Wed, Jun 17, 2020 at 3:47 PM Ian Lance Taylor wrote:
>
> On Wed, Jun 17, 2020 at 1:09 PM jimmy frasche wrote:
> >
> > This isn't a bug per se, but I can file one if requested.
On Wed, Jun 17, 2020 at 1:09 PM jimmy frasche wrote:
>
> This isn't a bug per se, but I can file one if requested.
>
> https://go2goplay.golang.org/p/AWynhg6ya7h
>
> Since embedding interfaces with type lists uses the intersection of
> the items in the type list, it's possible to create an
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