-> RecFlag
-> Bool -- True <=> want generics functions
-> Bool -- True <=> was declared in GADT syntax
- -> Maybe (TyCon, [Type],
- Int) -- Just (family, tys, index)
- -- <=> instance of `family' at `tys'
+ -> Maybe (TyCon, [Type]) -- family instance if applicable
-> TcRnIf m n TyCon
buildAlgTyCon tc_name tvs stupid_theta rhs is_rec want_generics gadt_syn
= do { -- We need to tie a knot as the coercion of a data instance depends
-- on the instance representation tycon and vice versa.
; tycon <- fixM (\ tycon_rec -> do
- { (final_name, parent) <- maybeComputeFamilyInfo mb_family tycon_rec
- ; let { tycon = mkAlgTyCon final_name kind tvs stupid_theta rhs
+ { parent <- parentInfo mb_family tycon_rec
+ ; let { tycon = mkAlgTyCon tc_name kind tvs stupid_theta rhs
fields parent is_rec want_generics gadt_syn
; kind = mkArrowKinds (map tyVarKind tvs) liftedTypeKind
; fields = mkTyConSelIds tycon rhs
}
where
-- If a family tycon with instance types is given, the current tycon is an
- -- instance of that family and we have to perform three extra tasks:
+ -- instance of that family and we need to
--
- -- (1) The instance tycon (representing the family at a particular type
- -- instance) need to get a new, derived name - we may not reuse the
- -- family name.
- -- (2) Create a coercion that identifies the family instance type and the
+ -- (1) create a coercion that identifies the family instance type and the
-- representation type from Step (1); ie, it is of the form
-- `Co tvs :: F ts :=: R tvs', where `Co' is the name of the coercion,
- -- `F' the family tycon and `R' the (derived) representation tycon.
- -- (3) Produce a `AlgTyConParent' value containing the parent and coercion
+ -- `F' the family tycon and `R' the (derived) representation tycon,
+ -- and
+ -- (2) produce a `AlgTyConParent' value containing the parent and coercion
-- information.
--
- maybeComputeFamilyInfo Nothing rep_tycon =
- return (tc_name, NoParentTyCon)
- maybeComputeFamilyInfo (Just (family, instTys, index)) rep_tycon =
- do { -- (1) New, derived name for the instance tycon
- ; final_name <- newImplicitBinder tc_name (mkInstTyTcOcc index)
-
- -- (2) Create the coercion.
- ; co_tycon_name <- newImplicitBinder tc_name (mkInstTyCoOcc index)
+ parentInfo Nothing rep_tycon =
+ return NoParentTyCon
+ parentInfo (Just (family, instTys)) rep_tycon =
+ do { -- Create the coercion
+ ; co_tycon_name <- newImplicitBinder tc_name mkInstTyCoOcc
; let co_tycon = mkDataInstCoercion co_tycon_name tvs
family instTys rep_tycon
-
- -- (3) Produce parent information.
- ; return (final_name, FamilyTyCon family instTys co_tycon index)
+ ; return $ FamilyTyCon family instTys co_tycon
}