You can use the #{x : T} reader syntax to annotate variables in macros
like `command-line`. Here's a working version of your code:
```
#lang typed/racket
(define *channel* (make-parameter "#general"))
(define *message* : (Parameterof (Listof String)) (make-parameter '()))
(define (parse-cmdline)
(command-line
#:program "q"
#:once-each
[("-c" "--channel") #{ch : String} "slack channel to post (default:
use .qrc setting or default)" (*channel* ch)]
#:args #{msg : String}
(*message* msg)))
```
On Mon, Mar 6, 2017 at 2:08 AM, kay <[email protected]> wrote:
> For a complex syntax form like `command-line`, I have difficulty correctly
> annotate the bindings it defines.
>
> More specifically, in the below code, for variable `msg`, even the
> document[1] says the `#:args` binds as list of **strings**, but the error
> indicates that it somehow is declared as `Listof Any`.
>
> Similarly, for variable `ch` bound in line 11, I believe it should always be
> `String`, but it somehow is declared to be `Any`.
>
> What should I do with this type of error, if I want my varaibles to be more
> precisely typed than just `Any`?
>
>
> [1]:
> https://docs.racket-lang.org/reference/Command-Line_Parsing.html?q=command-line#%28form._%28%28lib._racket%2Fcmdline..rkt%29._command-line%29%29
>
> ```
> 1 #lang typed/racket
> 2
> 3 (define *channel* (make-parameter "#general"))
> 4 (define *message* : (Parameterof (Listof String)) (make-parameter
> '()))
> 5
> 6
> 7 (define (parse-cmdline)
> 8 (command-line
> 9 #:program "q"
> 10 #:once-each
> 11 [("-c" "--channel") ch "slack channel to post (default: use .qrc
> setting or default)" (*channel* ch)]
> 12 #:args msg
> 13 (*message* msg)))
> 14
> 15
> 16 #|
> 17 tr.rkt:11:91: Type Checker: Wrong argument to parameter - expected
> String and got Any in: (*channel* ch)
> 18 tr.rkt:13:5: Type Checker: Wrong argument to parameter - expected
> (Listof String) and got (Listof Any) in: (*message* msg)
> 19 |#
> ```
>
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