See
phrase_from_file loads lazily. It has an attributed variable, when you try to unify it it fires off
a goal that loads more text. This kinda-sorta works.
@jan - would it make sense to have a non-lazy phrase_from_file that supported the current line/char reporting? I usually am using phrase_from_file not because it’s lazy but because it supports line tracking, which is pretty much always needed - you will eventually have to deal iwth invalid files,
and ‘not valid’ is rarely the right error message.