15.3.5 Imported syntactic bindings

The data describing syntactic bindings established by a library is stored in a library object:

• If no rename clause is used in the import clause: the imported name equals the exported name and it is taken from the export-subst field of the library object. The export-subst maps exported names to label gensyms; it is an alist whose entries have format:

  (?exported-name . ?label)
  

• The syntactic binding’s descriptors are taken from the global-env field of the library object. The global-env maps label gensyms to their binding descriptors; it is an alist whose entries have format:

  (?label . ?binding-descriptor)
  

• When the library is interned: a library object is created and the fields export-subst and global-env are used to build the label gensyms by storing the descriptors in the value slots of the gensyms.
• When a library is imported: the imported names of syntactic bindings are associated to their label gensyms in the rib object representing the current lexical context.