*
This parser should only ever be called when a dynamic escape scheme exists
so the escape scheme is evaluated in the right scope. If a constant
escape scheme exists, the Evaluatable should store the constant and this
should never be called.
Note that the escape scheme evaluatable (and its dependencies) are manually
cached, so upon exiting scope the cache must be invalidated.
* This parser should only ever be called when a dynamic escape scheme exists so the escape scheme is evaluated in the right scope. If a constant escape scheme exists, the Evaluatable should store the constant and this should never be called.
Note that the escape scheme evaluatable (and its dependencies) are manually cached, so upon exiting scope the cache must be invalidated.