What about passing the configuration data to `other-module-begin` via 
keyword arguments or tagged expressions in the body of the 
`(other-module-begin ...)` expansion? Is there a particular reason `mb` and 
`other-module-begin` need to communicate with syntax properties?

On Tuesday, November 28, 2017 at 7:15:50 PM UTC-8, Matthew Butterick wrote:
>
> I'm making a #%module-begin macro, but I want to delegate it to an 
> existing one. 
>
> OK, let's start with a rename transformer: 
>
> (provide (rename-out [mb #%module-begin])) 
> (define-syntax mb (make-rename-transformer #'other-module-begin)) 
> (define-syntax other-module-begin (λ (stx) #'foo)) 
>
> That works, but I also need to pass some extra data to 
> `other-module-begin` that controls how it's configured during this 
> delegation. 
>
> OK, let's add a syntax property. But wrapping the property around the 
> transformer doesn't work, because a rename transformer is not `syntax?`: 
>
> (provide (rename-out [mb #%module-begin])) 
> (define-syntax mb (syntax-property (make-rename-transformer 
> #'other-module-begin) 'foo "bar")) 
> (define-syntax other-module-begin (λ (stx) #'foo)) 
>
> ;; syntax-property: contract violation 
>
>
> I can wrap the property around the target identifier, but the syntax 
> property doesn't stick: 
>
> (provide (rename-out [mb #%module-begin])) 
> (define-syntax mb (make-rename-transformer (syntax-property 
> #'other-module-begin 'foo "bar"))) 
> (define-syntax other-module-begin (λ (stx) #'foo)) 
>
> (syntax-property #'mb 'foo) ; #f 
>
>
> Other possibilities with equivalent effect?

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