-- can appear as the right hand side of a type synonym.
| FunTy
- Type
+ Type
Type -- ^ Special case of 'TyConApp': @TyConApp FunTyCon [t1, t2]@
+ -- See Note [Equality-constrained types]
| ForAllTy
- TyCoVar -- ^ Type *or* coercion variable; see Note [Equality-constrained types]
+ TyCoVar -- Type variable
Type -- ^ A polymorphic type
| PredTy
is encoded like this:
ForAllTy (a:*) $ ForAllTy (b:*) $
- ForAllTy (wild_co : a ~ [b]) $
+ FunTy (PredTy (EqPred a [b]) $
blah
-That is, the "(a ~ [b]) =>" part is encode as a for-all
-type with a coercion variable that is never mentioned.
-
-We could instead have used a FunTy with an EqPred on the
-left. But we want
-
- * FunTy to mean RUN-TIME abstraction,
- passing a real value at runtime,
-
- * ForAllTy to mean COMPILE-TIME abstraction,
- erased at runtime
-
-------------------------------------
Note [PredTy]
split2 ps (PredTy p `FunTy` ty) = split2 (p:ps) ty
split2 ps ty = (reverse ps, ty)
-ppr_tc_app :: Prec -> TyCon -> [Type] -> SDoc
-ppr_tc_app _ tc []
- = ppr_tc tc
-ppr_tc_app _ tc [ty]
- | tc `hasKey` listTyConKey = brackets (pprType ty)
- | tc `hasKey` parrTyConKey = ptext (sLit "[:") <> pprType ty <> ptext (sLit ":]")
- | tc `hasKey` liftedTypeKindTyConKey = ptext (sLit "*")
- | tc `hasKey` unliftedTypeKindTyConKey = ptext (sLit "#")
- | tc `hasKey` openTypeKindTyConKey = ptext (sLit "(?)")
- | tc `hasKey` ubxTupleKindTyConKey = ptext (sLit "(#)")
- | tc `hasKey` argTypeKindTyConKey = ptext (sLit "??")
-
-ppr_tc_app p tc tys
- | isTupleTyCon tc && tyConArity tc == length tys
- = tupleParens (tupleTyConBoxity tc) (sep (punctuate comma (map pprType tys)))
- | otherwise
- = ppr_type_app p (getName tc) tys
-
-ppr_type_app :: Prec -> Name -> [Type] -> SDoc
--- Used for classes as well as types; that's why it's separate from ppr_tc_app
-ppr_type_app p tc tys
- | is_sym_occ -- Print infix if possible
- , [ty1,ty2] <- tys -- We know nothing of precedence though
- = maybeParen p FunPrec (sep [ppr_type FunPrec ty1,
- pprInfixVar True (ppr tc) <+> ppr_type FunPrec ty2])
- | otherwise
- = maybeParen p TyConPrec (hang (pprPrefixVar is_sym_occ (ppr tc))
- 2 (sep (map pprParendType tys)))
- where
- is_sym_occ = isSymOcc (getOccName tc)
-
-ppr_tc :: TyCon -> SDoc -- No brackets for SymOcc
-ppr_tc tc
- = pp_nt_debug <> ppr tc
- where
- pp_nt_debug | isNewTyCon tc = ifPprDebug (if isRecursiveTyCon tc
- then ptext (sLit "<recnt>")
- else ptext (sLit "<nt>"))
- | otherwise = empty
-
ppr_tvar :: TyVar -> SDoc
ppr_tvar tv -- Note [Infix type variables]
| isSymOcc (getOccName tv) = parens (ppr tv)