On Mon, Apr 9, 2018 at 5:08 PM, Philip McGrath <phi...@philipmcgrath.com> wrote:
> Thanks for your helpful reply. I've created GitHub issues
> https://github.com/racket/typed-racket/issues/691 and
> https://github.com/racket/typed-racket/issues/692 to track the bugs, and I
> will try my hand at a pull request for `parse-command-line` if I have time
> before you do.

Great, thanks!

> On Fri, Apr 6, 2018 at 10:12 AM, Sam Tobin-Hochstadt <sa...@cs.indiana.edu>
> wrote:
>> This is in some ways a weakness in the concept for `#:type-name`. The
>> `struct` form relies on the parent struct to both find the type and to
>> find the parent struct in the underlying `struct` macro. We could add
>> a `#:parent-type-name` option to use here, but then we'd have to
>> enforce that they go together in some way. I'm not sure what the best
>> design is here.
> This explanation makes sense—should something about this limitation be added
> to the reference?

Yes, it should -- or maybe `#:type-name` should behave like one of my

>> To work around this, try:
>> #lang typed/racket
>> (struct animal () #:transparent)
>> (struct dog animal () #:transparent)
>> (define-type Animal animal)
> This seems like a very good work-around. Other than the fact that using
> `#:type-name` would mean that `animal` could not be used as a type, is there
> any difference between the result of this and what `#:type-name` does?

That's the difference.

>> > 3. parse-command-line doesn't support usage-help, help-labels,
>> > help-proc, or
>> > unknown-proc
> A part of this that particularly surprised me was that the built-in type
> didn't work with `require/typed` because Typed Racket couldn't generate a
> contract for it. Is the generation of contracts for built-in types handled
> differently than for programmer-specified types?

Yes, it's quite different -- Typed Racket doesn't actually generate a
contract for `parse-command-line` (or for other built-in functions
like `+` or `list`).

> More broadly, I don't feel like I have very strong intuitions about what
> types Typed Racket can and can't generate contracts for. I believe the Typed
> Racket team is working to be able to generate contracts for more and more
> types, so maybe you are avoiding specifics in the documentation for that
> reason, but I think it would be valuable to have some more detail about what
> is currently possible.

Yes, I think more documentation on this would be an improvement. This
section has a bit of that
http://docs.racket-lang.org/ts-guide/caveats.html but we should add

The part that doesn't work is the type for `finish-proc`, which uses
`...` in the type in a way that Typed Racket can't automatically
generate a contract for.


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