Function allsorts::gsub::gsub_lookup_would_apply

pub fn gsub_lookup_would_apply<T: GlyphData>(
    opt_gdef_table: Option<&GDEFTable>, 
    lookup: &LookupCacheItem<SubstLookup>, 
    glyphs: &[RawGlyph<T>], 
    i: usize
) -> Result<bool, ParseError>