Error Message Formatting about fathom

[mikeday]

The Rust compiler errors seem the most relevant to this situation. Showing the original line (trimmed?) and highlighting the specific span is pretty cool!

[brendanzab]

Definitely at least want to be able to show the original line with a highlighted span, at the very least!

[prjnt]

On Mon, Sep 18, 2017 at 10:33:54PM -0700, Brendan Zabarauskas wrote: Definitely at least want to be able to show the original line with a highlighted span, at the very least!

Keep in mind the common case that the input file is one gigantic line. pjrm.

[brendanzab]

This is more for errors coming from parsing and type checking the DDL definitions (eg. the OTF specification), rather than the errors coming from the resulting generated parsers when they read binary data (eg. and actual font).

[mikeday]

"line" can be safely interpreted as "[up to] 80 character substring of the original line", I think.

[brendanzab]

Pulled out the source location and error diagnostic stuff from pikelet into https://github.com/brendanzab/codespan - still need to make the errors prettier, but it's a start!