15.3.5.10 Imported syntactic bindings: synonym syntaxes

A syntactic binding representing an imported keyword binding associated to a synonym syntax has descriptor with format:

($synonym . ?synonym-label)

where ?synonym-label is the label gensym associated to the aliased syntax; How synonym syntaxes work.

Syntactic bindings of this type are established by define-syntax, let-syntax and similar when the result of evaluating their right–hand side expression is the return value of a call to make-synonym-transformer.