15.3.6.12 Internal syntactic bindings: displaced syntactic bindings

These pairs have a format similar to a LEXENV entry representing a syntactic binding, but they are used to represent a failed search into a LEXENV.

The following special value represents an unbound label:

(displaced-lexical . #f)

this is an “identifier out of context” error.

The following special value represents the result of a lexical environment query with invalid label value (not a symbol):

(displaced-lexical . ())