evaluating syntax transformer threw unbound location first

[Panicz Maciej Godek <godek dot maciek at gmail dot com>]

Hello,
I've been trying to comfort myself with a macro to
describe apps for android. After some trials and errors
I concluded that the resulting code should look more
or less like this:

(activity
 app
 (on-create-view
  (let* ((short-view ::int 0)
         (long-view ::int 1)
         (app ::android.widget.ViewFlipper
              (view-flipper))
         (show (lambda(view)
                 ((as android.widget.ViewFlipper app):setDisplayedChild
                  view))))
    (app:addView
     (button text: "Go to view 2"
             typeface: android.graphics.Typeface:SERIF
             on-click-listener: (lambda _ (show long-view))))
    (app:addView
     (button text: "Go to view 1"
             typeface: android.graphics.Typeface:SANS_SERIF
             on-click-listener: (lambda _ (show short-view))))
    (as android.view.View app))))

it works fine, but I wished that the code could be generated
from the following, more concise description:

(define-application-views app
  (short-view
   (button text: "Go to view 2"
           typeface: android.graphics.Typeface:SERIF
           on-click-listener: (lambda _ (show long-view))))
  (long-view
   (button text: "Go to view 1"
           typeface: android.graphics.Typeface:SANS_SERIF
           on-click-listener: (lambda _ (show short-view)))))

I therefore wrote a macro to help me achieve this. I'm
not particularly fluent with syntax-case macros, but since
there were some strange issues regarding define-macro
(it was problematic to use "(this)" in the code generated
by them), I had to resort to the syntax-case system.
I eventually came up with the following code:

(define-syntax define-application-views
  (lambda (stx)
    (syntax-case stx (show)
      ((define-application-views activity-name . names+views)
       (with-syntax ((show (datum->syntax #'define-application-views 'show)))
         #`(activity
            activity-name
            (on-create-view
             (let* (#,@(datum->syntax
                        stx
                        (map (lambda (name+view id)
                               `(,(first name+view) ::int ,id))
                             (syntax->datum #'names+views)
                             (iota (length (syntax->datum #'names+views)))))
                    (activity-name ::android.widget.ViewFlipper
                     (view-flipper))
                    (show
                     (lambda (view)
                       ((as android.widget.ViewFlipper
                            activity-name):setDisplayedChild
                            view))))
               #,@(datum->syntax
                   stx
                   (map (lambda(name+view)
                          `((as android.widget.ViewFlipper
#'activity-name):addView
,(second name+view)))
                        (syntax->datum #'names+views)))
               (as android.view.View activity-name)))))))))

I also defined a few helper macros, so to make the example
complete (albeit in reverse), I hereby provide the full header:

(require 'android-defs)
(require 'srfi-1)
(require 'srfi-2)

(define-syntax define-syntax-rule
  (syntax-rules ()
      ((_ (name args ...) body)
       (define-syntax name
         (syntax-rules ()
           ((name args ...)
            body))))))

(define-syntax-rule (button args ...)
  (android.widget.Button (this) args ...))

(define-syntax-rule (text-view args ...)
  (android.widget.TextView (this) args ...))

(define-syntax-rule (view-flipper args ...)
  (android.widget.ViewFlipper (this) args ...))

The macro did work with the syntax-case system in Guile Scheme,
but when I tried to build it (using the "android-kawa" framework
that I've found here: https://github.com/abarbu/android-kawa),
I got the following error:

.../app.scm:87:1: evaluating syntax transformer
'define-application-views' threw unbound location first

is there any way I could introspect that error further?

Thanks in advance,
Panicz