Check for unreachable glyphs?

[simoncozens]

This is just an idea, rather than a bug report - do we want to check for (or do we already have a check for) unencoded glyphs which are not referenced in any lookup?

[davelab6]

Love this

[madig]

Uh, shouldn't the code check if these glyphs are used as components by otherwise reachable glyphs? There should be no findings after running pyftsubset --unicodes=* --layout-features=* ... on a font and running the check on the result.