isTyConAssoc,
isRecursiveTyCon,
isHiBootTyCon,
- isImplicitTyCon, tyConHasGenerics,
+ isImplicitTyCon,
-- ** Extracting information out of TyCons
tyConName,
tyConExtName, -- External name for foreign types
algTyConRhs,
newTyConRhs, newTyConEtadRhs, unwrapNewTyCon_maybe,
- tupleTyConBoxity,
+ tupleTyConBoxity, tupleTyConArity,
-- ** Manipulating TyCons
tcExpandTyCon_maybe, coreExpandTyCon_maybe,
* Translation of type instance decl:
type instance F [a] = Maybe a
- translates to
- A SynTyCon 'R:FList a', whose
+ translates to a "representation TyCon", 'R:FList', where
+ R:FList is a SynTyCon, whose
SynTyConRhs is (SynonymTyCon (Maybe a))
TyConParent is (FamInstTyCon F [a] co)
where co :: F [a] ~ R:FList a
- Notice that we introduce a gratuitous vanilla type synonym
+
+ It's very much as if the user had written
+ type instance F [a] = R:FList a
type R:FList a = Maybe a
- solely so that type and data families can be treated more
- uniformly, via a single FamInstTyCon descriptor
+ Indeed, in GHC's internal representation, the RHS of every
+ 'type instance' is simply an application of the representation
+ TyCon to the quantified varaibles.
+
+ The intermediate representation TyCon is a bit gratuitous, but
+ it means that:
+
+ each 'type instance' decls is in 1-1 correspondance
+ with its representation TyCon
+
+ So the result of typechecking a 'type instance' decl is just a
+ TyCon. In turn this means that type and data families can be
+ treated uniformly.
* In the future we might want to support
* closed type families (esp when we have proper kinds)
algTcRec :: RecFlag, -- ^ Tells us whether the data type is part
-- of a mutually-recursive group or not
-
- hasGenerics :: Bool, -- ^ Whether generic (in the -XGenerics sense)
- -- to\/from functions are available in the exports
- -- of the data type's source module.
-
+
algTcParent :: TyConParent -- ^ Gives the class or family declaration 'TyCon'
-- for derived 'TyCon's representing class
-- or family instances, respectively.
tyConArity :: Arity,
tyConBoxed :: Boxity,
tyConTyVars :: [TyVar],
- dataCon :: DataCon, -- ^ Corresponding tuple data constructor
- hasGenerics :: Bool
+ dataCon :: DataCon -- ^ Corresponding tuple data constructor
}
-- | Represents type synonyms
Note [Enumeration types]
~~~~~~~~~~~~~~~~~~~~~~~~
-We define datatypes with no constructors to not be
+We define datatypes with no constructors to *not* be
enumerations; this fixes trac #2578, Otherwise we
end up generating an empty table for
<mod>_<type>_closure_tbl
in an enumeration. The empty table apparently upset
the linker.
+Moreover, all the data constructor must be enumerations, meaning
+they have type (forall abc. T a b c). GADTs are not enumerations.
+For example consider
+ data T a where
+ T1 :: T Int
+ T2 :: T Bool
+ T3 :: T a
+What would [T1 ..] be? [T1,T3] :: T Int? Easiest thing is to exclude them.
+See Trac #4528.
+
Note [Newtype coercions]
~~~~~~~~~~~~~~~~~~~~~~~~
The NewTyCon field nt_co is a a TyCon (a coercion constructor in fact)
-> AlgTyConRhs -- ^ Information about dat aconstructors
-> TyConParent
-> RecFlag -- ^ Is the 'TyCon' recursive?
- -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
-> Bool -- ^ Was the 'TyCon' declared with GADT syntax?
-> TyCon
-mkAlgTyCon name kind tyvars stupid rhs parent is_rec gen_info gadt_syn
+mkAlgTyCon name kind tyvars stupid rhs parent is_rec gadt_syn
= AlgTyCon {
tyConName = name,
tyConUnique = nameUnique name,
algTcRhs = rhs,
algTcParent = ASSERT( okParent name parent ) parent,
algTcRec = is_rec,
- algTcGadtSyntax = gadt_syn,
- hasGenerics = gen_info
+ algTcGadtSyntax = gadt_syn
}
-- | Simpler specialization of 'mkAlgTyCon' for classes
mkClassTyCon :: Name -> Kind -> [TyVar] -> AlgTyConRhs -> Class -> RecFlag -> TyCon
mkClassTyCon name kind tyvars rhs clas is_rec =
- mkAlgTyCon name kind tyvars [] rhs (ClassTyCon clas) is_rec False False
+ mkAlgTyCon name kind tyvars [] rhs (ClassTyCon clas) is_rec False
mkTupleTyCon :: Name
-> Kind -- ^ Kind of the resulting 'TyCon'
-> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'
-> DataCon
-> Boxity -- ^ Whether the tuple is boxed or unboxed
- -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
-> TyCon
-mkTupleTyCon name kind arity tyvars con boxed gen_info
+mkTupleTyCon name kind arity tyvars con boxed
= TupleTyCon {
tyConUnique = nameUnique name,
tyConName = name,
tyConArity = arity,
tyConBoxed = boxed,
tyConTyVars = tyvars,
- dataCon = con,
- hasGenerics = gen_info
+ dataCon = con
}
-- ^ Foreign-imported (.NET) type constructors are represented
tupleTyConBoxity :: TyCon -> Boxity
tupleTyConBoxity tc = tyConBoxed tc
+-- | Extract the arity of the given 'TyCon', if it is a 'TupleTyCon'.
+-- Panics otherwise
+tupleTyConArity :: TyCon -> Arity
+tupleTyConArity tc = tyConArity tc
+
-- | Is this a recursive 'TyCon'?
isRecursiveTyCon :: TyCon -> Bool
isRecursiveTyCon (AlgTyCon {algTcRec = Recursive}) = True
\end{code}
\begin{code}
--- | Does this 'TyCon' have any generic to\/from functions available? See also 'hasGenerics'
-tyConHasGenerics :: TyCon -> Bool
-tyConHasGenerics (AlgTyCon {hasGenerics = hg}) = hg
-tyConHasGenerics (TupleTyCon {hasGenerics = hg}) = hg
-tyConHasGenerics _ = False -- Synonyms
tyConKind :: TyCon -> Kind
tyConKind (FunTyCon { tc_kind = k }) = k
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