yapl6-mode

Yet Another Perl6 emacs mode.

Approach

Main idea

This mode calls out to Perl6::Parser to parse the source code and return detailed information which type of symbol is located where with start/end markers.

Negotiatable approach

1. Create Emacs overlays which augment the text with pre-declared faces. This is mostly meant as initial start to understand how things work, because it directly uses the information provided by Perl6::Parser.

   This keeps the highlighting until the next time quite static and only up to date as long as Emacs can keep track of start/end points, which it can inside words and between words but not well on word boundaries.

   The behaviour might remind you of the very early Emacs "hilite" modes before there was font-lock. I think it is similar.

2. We might trigger the highlighting explicitely with a key or implicitely when idle.

3. Indentation ideas:

   • "Steal" indentation logic from some other mode (good old perl-mode (not cperl-mode), or perl6-mode.
   • Use the balanced entry/exit information from Perl6::Parser.

Issues and mitigation ideas

1. It can only work on successfully parsable files.

   • the highlighting stays around until it is syntactically ok again

2. Although calling out to perl6 is quick enough nowadays running Perl6::Parser is slow for larger files.

   It even seems to parse used modules, which can mean awhole tree of dependencies, not sure if I observed and understood that correctly.

   • maybe we can parse balanced snippets of code with Perl6::Parser?

3. The interaction with the Perl6 glue code which generates the lisp code is not elegant and for now uses temporary files or whole programs in strings or whatever helps.

   • This will just evolve.