false positive "unused variable" for sig-elems in define-signature

For this code (from Racket Guide)

```racket
#lang racket
 
(define-signature toy-factory^
  (build-toys  ; (integer? -> (listof toy?))
   repaint     ; (toy? symbol? -> toy?)
   toy?        ; (any/c -> boolean?)
   toy-color)) ; (toy? -> symbol?)
 
(provide toy-factory^)

```

`build-toys`, `repaint `, `toy?` and `toy-color` are highlighted as "unused variables" (in VsCode with Magic Racket)