only integers please

xenomorph/xenomorph/int.rkt

@@ -67,8 +67,11 @@ https://github.com/mbutterick/restructure/blob/master/src/Number.coffee
       (if signed (unsigned->signed uint @bits) uint))
                 
     (define/augment (x:encode val . _)
+      (unless (integer? val)
+        (raise-argument-error 'x:encode "integer" val))
+                             
       (unless (<= bound-min val bound-max)
-        (raise-argument-error 'encode
+        (raise-argument-error 'x:encode
                               (format "value that fits within ~a ~a-byte int (~a to ~a)" (if signed "signed" "unsigned") @size bound-min bound-max) val))
       (for/fold ([bs null]
                  [val (exact-if-possible val)]