contract-out struct is inconsistent with struct-out

[sorawee]

#lang racket

(module first racket
  (struct foo (x))
  (provide (contract-out (struct foo ([x boolean?])))))

(module second racket
  (require (only-in (submod ".." first) foo))
  (provide (contract-out (struct foo ([x boolean?])))))

(require 'second)

foo-x

evaluates to the accessor foo-x.

However, the corresponding struct-out fails:

#lang racket

(module first racket
  (struct foo (x))
  (provide (struct-out foo)))

(module second racket
  (require (only-in (submod ".." first) foo))
  (provide (struct-out foo)))

(require 'second)

foo-x

;; struct-out: no binding for structure-type identifier
;;   at: struct:foo
;;   in: (struct-out foo)

It's unclear which one has the desired behavior. Note that struct-out used to have the same behavior as contract-out, but it was changed to the current behavior in 096ec54

[rfindler]

Just based on the history, it looks like struct-out is right and contract-out is wrong.

[mflatt]

A note on the difference: A provide can only export bindings that are imported or defined. In the case of struct-out, if it did not complain about struct:foo, then provide would complain. In the case of contract-out, new bindings are created in the providing module by contract-out (to implement the contract), and those bindings can refer to things (via macro expansion) that are not explicitly imported. So, that's why contract-out can export more — because it's really exporting different.

[sorawee]

Since this seems to work as intended, I will close the issue.