- -- for associated families: for each tyvar in the AT decl, gives the
- -- position of that tyvar in the class argument list (starting from 0).
- -- NB: Length is less than tyConArity iff higher kind signature.
- -- NB: Just _ <=> associated (not toplevel) family
+ -- Nothing <=> top-level indexed type family
+ -- Just ns <=> associated (not toplevel) family
+ -- In the latter case, for each tyvar in the AT decl, 'ns' gives the
+ -- position of that tyvar in the class argument list (starting from 0).
+ -- NB: Length is less than tyConArity iff higher kind signature.