[furcas-discussion] Parser Invariants

[Stephan Erb]

Hey Thomas,

I have a few simple questions concerning incremental lexing and parsing.

      * Is it guaranteed that the parser does not change the textual
        representation? (Seems like a obvious yes to me, but I'd like to
        have your confirmation on this)
      * The lexer takes the PREVIOUS version and creates the CURRENT
        one. If there is an existing CURRENT version, it is discarded
        first. What does the parser do with these two versions? When the
        parser has finished, are both versions consistent views on model
        or are they somewhat different?
      * Is the latest CURRENT version promoted to become the new
        PREVIOUS version?
      * Is it dangerous to set errorMode=True in the parse run and force
        the parser to inject as far as possible, even if there are
        syntax errors?

I ask all these questions because they are crucial when determining the
critical regions for the synchronization of the background parsing
thread.  

Thanks!
Stephan