Typing generators

You currently can't use generators in Typed Racket, because the generator syntax expands to a use of create-generator, which is a private definition in racket/generator.

What version of Racket are you using?

v6.7

What program did you run?

#lang typed/racket
(require racket/generator)
(generator () (void))

What should have happened?

#<procedure:generator>

If you got an error message, please include it here.

; Type Checker: missing type for identifier;
;  consider using `require/typed' to import it
;   identifier: create-generator
;   from module: racket/generator
;   in: #%module-begin

There are some other complications involved in typing generators, mostly that the type of yield is parameterized on the current generator, but these can be worked around for simple uses. There doesn't appear to be any way to work around create-generator not having a type.

Start with the reported Typed Racket expansion from generator to the private create-generator in racket/generator. Reproduce the v6.7 example using #lang typed/racket, then investigate how the missing type and the parameterized yield type affect generator support. Done means the example type-checks and produces the documented generator procedure.