TyCon, FieldLabel,
AlgTyConRhs(..), visibleDataCons,
- TyConParent(..),
+ TyConParent(..), isNoParent,
SynTyConRhs(..),
- CoTyConDesc(..),
- AssocFamilyPermutation,
+
+ -- ** Coercion axiom constructors
+ CoAxiom(..), coAxiomName, coAxiomArity,
-- ** Constructing TyCons
mkAlgTyCon,
mkTupleTyCon,
mkSynTyCon,
mkSuperKindTyCon,
- mkCoercionTyCon,
mkForeignTyCon,
mkAnyTyCon,
isFunTyCon,
isPrimTyCon,
isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon,
- isSynTyCon, isClosedSynTyCon, isOpenSynTyCon,
+ isSynTyCon, isClosedSynTyCon,
isSuperKindTyCon, isDecomposableTyCon,
- isCoercionTyCon, isCoercionTyCon_maybe,
isForeignTyCon, isAnyTyCon, tyConHasKind,
isInjectiveTyCon,
isDataTyCon, isProductTyCon, isEnumerationTyCon,
- isNewTyCon, isAbstractTyCon, isOpenTyCon,
+ isNewTyCon, isAbstractTyCon,
+ isFamilyTyCon, isSynFamilyTyCon, isDataFamilyTyCon,
isUnLiftedTyCon,
isGadtSyntaxTyCon,
isTyConAssoc,
tyConFamilySize,
tyConStupidTheta,
tyConArity,
+ tyConParent,
tyConClass_maybe,
- tyConFamInst_maybe, tyConFamilyCoercion_maybe,
- synTyConDefn, synTyConRhs, synTyConType, synTyConResKind,
- tyConExtName, -- External name for foreign types
+ tyConFamInst_maybe, tyConFamilyCoercion_maybe,tyConFamInstSig_maybe,
+ synTyConDefn, synTyConRhs, synTyConType,
+ tyConExtName, -- External name for foreign types
algTyConRhs,
newTyConRhs, newTyConEtadRhs, unwrapNewTyCon_maybe,
- assocTyConArgPoss_maybe,
tupleTyConBoxity,
-- ** Manipulating TyCons
tcExpandTyCon_maybe, coreExpandTyCon_maybe,
makeTyConAbstract,
- newTyConCo_maybe,
- setTyConArgPoss,
+ newTyConCo, newTyConCo_maybe,
-- * Primitive representations of Types
PrimRep(..),
import Outputable
import FastString
import Constants
-import Data.List( elemIndex )
+import Util
+import qualified Data.Data as Data
\end{code}
+-----------------------------------------------
+ Notes about type families
+-----------------------------------------------
+
+Note [Type synonym families]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+* Type synonym families, also known as "type functions", map directly
+ onto the type functions in FC:
+
+ type family F a :: *
+ type instance F Int = Bool
+ ..etc...
+
+* Reply "yes" to isSynFamilyTyCon, and isFamilyTyCon
+
+* From the user's point of view (F Int) and Bool are simply
+ equivalent types.
+
+* A Haskell 98 type synonym is a degenerate form of a type synonym
+ family.
+
+* Type functions can't appear in the LHS of a type function:
+ type instance F (F Int) = ... -- BAD!
+
+* Translation of type family decl:
+ type family F a :: *
+ translates to
+ a SynTyCon 'F', whose SynTyConRhs is SynFamilyTyCon
+
+* Translation of type instance decl:
+ type instance F [a] = Maybe a
+ 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
+
+ It's very much as if the user had written
+ type instance F [a] = R:FList a
+ type R:FList a = Maybe a
+ 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.
+
+* Translation of type family decl:
+ type family F a :: *
+ translates to
+ a SynTyCon 'F', whose SynTyConRhs is SynFamilyTyCon
+
+* Translation of type instance decl:
+ type instance F [a] = Maybe a
+ translates to
+ A SynTyCon 'R:FList a', 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
+ type R:FList a = Maybe a
+ solely so that type and data families can be treated more
+ uniformly, via a single FamInstTyCon descriptor
+
+* In the future we might want to support
+ * closed type families (esp when we have proper kinds)
+ * injective type families (allow decomposition)
+ but we don't at the moment [2010]
+
+Note [Data type families]
+~~~~~~~~~~~~~~~~~~~~~~~~~
+See also Note [Wrappers for data instance tycons] in MkId.lhs
+
+* Data type families are declared thus
+ data family T a :: *
+ data instance T Int = T1 | T2 Bool
+
+ Here T is the "family TyCon".
+
+* Reply "yes" to isDataFamilyTyCon, and isFamilyTyCon
+
+* Reply "yes" to isDataFamilyTyCon, and isFamilyTyCon
+
+* The user does not see any "equivalent types" as he did with type
+ synonym families. He just sees constructors with types
+ T1 :: T Int
+ T2 :: Bool -> T Int
+
+* Here's the FC version of the above declarations:
+
+ data T a
+ data R:TInt = T1 | T2 Bool
+ axiom ax_ti : T Int ~ R:TInt
+
+ The R:TInt is the "representation TyCons".
+ It has an AlgTyConParent of
+ FamInstTyCon T [Int] ax_ti
+
+* The data contructor T2 has a wrapper (which is what the
+ source-level "T2" invokes):
+
+ $WT2 :: Bool -> T Int
+ $WT2 b = T2 b `cast` sym ax_ti
+
+* A data instance can declare a fully-fledged GADT:
+
+ data instance T (a,b) where
+ X1 :: T (Int,Bool)
+ X2 :: a -> b -> T (a,b)
+
+ Here's the FC version of the above declaration:
+
+ data R:TPair a where
+ X1 :: R:TPair Int Bool
+ X2 :: a -> b -> R:TPair a b
+ axiom ax_pr :: T (a,b) ~ R:TPair a b
+
+ $WX1 :: forall a b. a -> b -> T (a,b)
+ $WX1 a b (x::a) (y::b) = X2 a b x y `cast` sym (ax_pr a b)
+
+ The R:TPair are the "representation TyCons".
+ We have a bit of work to do, to unpick the result types of the
+ data instance declaration for T (a,b), to get the result type in the
+ representation; e.g. T (a,b) --> R:TPair a b
+
+ The representation TyCon R:TList, has an AlgTyConParent of
+
+ FamInstTyCon T [(a,b)] ax_pr
+
+* Notice that T is NOT translated to a FC type function; it just
+ becomes a "data type" with no constructors, which can be coerced inot
+ into R:TInt, R:TPair by the axioms. These axioms
+ axioms come into play when (and *only* when) you
+ - use a data constructor
+ - do pattern matching
+ Rather like newtype, in fact
+
+ As a result
+
+ - T behaves just like a data type so far as decomposition is concerned
+
+ - (T Int) is not implicitly converted to R:TInt during type inference.
+ Indeed the latter type is unknown to the programmer.
+
+ - There *is* an instance for (T Int) in the type-family instance
+ environment, but it is only used for overlap checking
+
+ - It's fine to have T in the LHS of a type function:
+ type instance F (T a) = [a]
+
+ It was this last point that confused me! The big thing is that you
+ should not think of a data family T as a *type function* at all, not
+ even an injective one! We can't allow even injective type functions
+ on the LHS of a type function:
+ type family injective G a :: *
+ type instance F (G Int) = Bool
+ is no good, even if G is injective, because consider
+ type instance G Int = Bool
+ type instance F Bool = Char
+
+ So a data type family is not an injective type function. It's just a
+ data type with some axioms that connect it to other data types.
+
%************************************************************************
%* *
\subsection{The data type}
--
-- 4) Class declarations: @class Foo where@ creates the @Foo@ type constructor of kind @*@
--
--- 5) Type coercions! This is because we represent a coercion from @t1@ to @t2@ as a 'Type', where
--- that type has kind @t1 ~ t2@. See "Coercion" for more on this
---
-- This data type also encodes a number of primitive, built in type constructors such as those
-- for function and tuple types.
data TyCon
tyConArity :: Arity
}
- -- | Algebraic type constructors, which are defined to be those arising @data@ type and @newtype@ declarations.
- -- All these constructors are lifted and boxed. See 'AlgTyConRhs' for more information.
+ -- | Algebraic type constructors, which are defined to be those
+ -- arising @data@ type and @newtype@ declarations. All these
+ -- constructors are lifted and boxed. See 'AlgTyConRhs' for more
+ -- information.
| AlgTyCon {
tyConUnique :: Unique,
tyConName :: Name,
tc_kind :: Kind,
tyConArity :: Arity,
- tyConTyVars :: [TyVar], -- ^ The type variables used in the type constructor.
- -- Precisely, this list scopes over:
- --
- -- 1. The 'algTcStupidTheta'
- --
- -- 2. The cached types in 'algTyConRhs.NewTyCon'
- --
- -- 3. The family instance types if present
- --
- -- Note that it does /not/ scope over the data constructors.
-
- algTcGadtSyntax :: Bool, -- ^ Was the data type declared with GADT syntax? If so,
- -- that doesn't mean it's a true GADT; only that the "where"
- -- form was used. This field is used only to guide
- -- pretty-printing
-
- algTcStupidTheta :: [PredType], -- ^ The \"stupid theta\" for the data type (always empty for GADTs).
- -- A \"stupid theta\" is the context to the left of an algebraic type
- -- declaration, e.g. @Eq a@ in the declaration @data Eq a => T a ...@.
-
- algTcRhs :: AlgTyConRhs, -- ^ Contains information about the data constructors of the algebraic type
-
- 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. See also 'synTcParent'
+ tyConTyVars :: [TyVar], -- ^ The type variables used in the type constructor.
+ -- Invariant: length tyvars = arity
+ -- Precisely, this list scopes over:
+ --
+ -- 1. The 'algTcStupidTheta'
+ -- 2. The cached types in 'algTyConRhs.NewTyCon'
+ -- 3. The family instance types if present
+ --
+ -- Note that it does /not/ scope over the data constructors.
+
+ algTcGadtSyntax :: Bool, -- ^ Was the data type declared with GADT syntax?
+ -- If so, that doesn't mean it's a true GADT;
+ -- only that the "where" form was used.
+ -- This field is used only to guide pretty-printing
+
+ algTcStupidTheta :: [PredType], -- ^ The \"stupid theta\" for the data type
+ -- (always empty for GADTs).
+ -- A \"stupid theta\" is the context to the left
+ -- of an algebraic type declaration,
+ -- e.g. @Eq a@ in the declaration
+ -- @data Eq a => T a ...@.
+
+ algTcRhs :: AlgTyConRhs, -- ^ Contains information about the
+ -- data constructors of the algebraic type
+
+ 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.
+ -- See also 'synTcParent'
}
- -- | Represents the infinite family of tuple type constructors, @()@, @(a,b)@, @(# a, b #)@ etc.
+ -- | Represents the infinite family of tuple type constructors,
+ -- @()@, @(a,b)@, @(# a, b #)@ etc.
| TupleTyCon {
tyConUnique :: Unique,
tyConName :: Name,
tyConTyVars :: [TyVar], -- Bound tyvars
- synTcRhs :: SynTyConRhs, -- ^ Contains information about the expansion of the synonym
+ synTcRhs :: SynTyConRhs, -- ^ Contains information about the
+ -- expansion of the synonym
- synTcParent :: TyConParent -- ^ Gives the family declaration 'TyCon' of 'TyCon's representing family instances
+ synTcParent :: TyConParent -- ^ Gives the family declaration 'TyCon'
+ -- of 'TyCon's representing family instances
}
- -- | Primitive types; cannot be defined in Haskell. This includes the usual suspects (such as @Int#@)
- -- as well as foreign-imported types and kinds
+ -- | Primitive types; cannot be defined in Haskell. This includes
+ -- the usual suspects (such as @Int#@) as well as foreign-imported
+ -- types and kinds
| PrimTyCon {
tyConUnique :: Unique,
tyConName :: Name,
tc_kind :: Kind,
- tyConArity :: Arity, -- SLPJ Oct06: I'm not sure what the significance
- -- of the arity of a primtycon is!
+ tyConArity :: Arity, -- SLPJ Oct06: I'm not sure what the significance
+ -- of the arity of a primtycon is!
- primTyConRep :: PrimRep, -- ^ Many primitive tycons are unboxed, but some are
- -- boxed (represented by pointers). This 'PrimRep' holds
- -- that information.
- -- Only relevant if tc_kind = *
+ primTyConRep :: PrimRep, -- ^ Many primitive tycons are unboxed, but some are
+ -- boxed (represented by pointers). This 'PrimRep'
+ -- holds that information.
+ -- Only relevant if tc_kind = *
- isUnLifted :: Bool, -- ^ Most primitive tycons are unlifted (may not contain bottom)
- -- but foreign-imported ones may be lifted
+ isUnLifted :: Bool, -- ^ Most primitive tycons are unlifted
+ -- (may not contain bottom)
+ -- but foreign-imported ones may be lifted
- tyConExtName :: Maybe FastString -- ^ @Just e@ for foreign-imported types,
- -- holds the name of the imported thing
- }
-
- -- | Type coercions, such as @(~)@, @sym@, @trans@, @left@ and @right@.
- -- INVARIANT: Coercion TyCons are always fully applied
- -- But note that a CoTyCon can be *over*-saturated in a type.
- -- E.g. (sym g1) Int will be represented as (TyConApp sym [g1,Int])
- | CoTyCon {
- tyConUnique :: Unique,
- tyConName :: Name,
- tyConArity :: Arity,
- coTcDesc :: CoTyConDesc
+ tyConExtName :: Maybe FastString -- ^ @Just e@ for foreign-imported types,
+ -- holds the name of the imported thing
}
-- | Any types. Like tuples, this is a potentially-infinite family of TyCons
| AnyTyCon {
tyConUnique :: Unique,
tyConName :: Name,
- tc_kind :: Kind -- Never = *; that is done via PrimTyCon
+ tc_kind :: Kind -- Never = *; that is done via PrimTyCon
-- See Note [Any types] in TysPrim
}
- -- | Super-kinds. These are "kinds-of-kinds" and are never seen in Haskell source programs.
- -- There are only two super-kinds: TY (aka "box"), which is the super-kind of kinds that
- -- construct types eventually, and CO (aka "diamond"), which is the super-kind of kinds
- -- that just represent coercions.
+ -- | Super-kinds. These are "kinds-of-kinds" and are never seen in
+ -- Haskell source programs. There are only two super-kinds: TY (aka
+ -- "box"), which is the super-kind of kinds that construct types
+ -- eventually, and CO (aka "diamond"), which is the super-kind of
+ -- kinds that just represent coercions.
--
-- Super-kinds have no kind themselves, and have arity zero
| SuperKindTyCon {
-- | Represents right-hand-sides of 'TyCon's for algebraic types
data AlgTyConRhs
- -- | Says that we know nothing about this data type, except that it's represented
- -- by a pointer. Used when we export a data type abstractly into an .hi file.
+ -- | Says that we know nothing about this data type, except that
+ -- it's represented by a pointer. Used when we export a data type
+ -- abstractly into an .hi file.
= AbstractTyCon
- -- | Represents an open type family without a fixed right hand
- -- side. Additional instances can appear at any time.
- --
- -- These are introduced by either a top level declaration:
- --
- -- > data T a :: *
- --
- -- Or an assoicated data type declaration, within a class declaration:
- --
- -- > class C a b where
- -- > data T b :: *
-
- | OpenTyCon {
- otArgPoss :: AssocFamilyPermutation
- }
-
- -- | Information about those 'TyCon's derived from a @data@ declaration. This includes
- -- data types with no constructors at all.
+ -- | Represents an open type family without a fixed right hand
+ -- side. Additional instances can appear at any time.
+ --
+ -- These are introduced by either a top level declaration:
+ --
+ -- > data T a :: *
+ --
+ -- Or an associated data type declaration, within a class declaration:
+ --
+ -- > class C a b where
+ -- > data T b :: *
+ | DataFamilyTyCon
+
+ -- | Information about those 'TyCon's derived from a @data@
+ -- declaration. This includes data types with no constructors at
+ -- all.
| DataTyCon {
data_cons :: [DataCon],
- -- ^ The data type constructors; can be empty if the user declares
- -- the type to have no constructors
- --
- -- INVARIANT: Kept in order of increasing 'DataCon' tag
-
- -- (see the tag assignment in DataCon.mkDataCon)
- is_enum :: Bool -- ^ Cached value: is this an enumeration type? (See 'isEnumerationTyCon')
+ -- ^ The data type constructors; can be empty if the user
+ -- declares the type to have no constructors
+ --
+ -- INVARIANT: Kept in order of increasing 'DataCon' tag
+ -- (see the tag assignment in DataCon.mkDataCon)
+
+ is_enum :: Bool -- ^ Cached value: is this an enumeration type?
+ -- See Note [Enumeration types]
}
-- | Information about those 'TyCon's derived from a @newtype@ declaration
| NewTyCon {
- data_con :: DataCon, -- ^ The unique constructor for the @newtype@. It has no existentials
+ data_con :: DataCon, -- ^ The unique constructor for the @newtype@.
+ -- It has no existentials
- nt_rhs :: Type, -- ^ Cached value: the argument type of the constructor, which
- -- is just the representation type of the 'TyCon' (remember that
- -- @newtype@s do not exist at runtime so need a different representation
- -- type).
+ nt_rhs :: Type, -- ^ Cached value: the argument type of the constructor,
+ -- which is just the representation type of the 'TyCon'
+ -- (remember that @newtype@s do not exist at runtime
+ -- so need a different representation type).
--
- -- The free 'TyVar's of this type are the 'tyConTyVars' from the corresponding
- -- 'TyCon'
+ -- The free 'TyVar's of this type are the 'tyConTyVars'
+ -- from the corresponding 'TyCon'
nt_etad_rhs :: ([TyVar], Type),
- -- ^ Same as the 'nt_rhs', but this time eta-reduced. Hence the list of 'TyVar's in
- -- this field may be shorter than the declared arity of the 'TyCon'.
+ -- ^ Same as the 'nt_rhs', but this time eta-reduced.
+ -- Hence the list of 'TyVar's in this field may be
+ -- shorter than the declared arity of the 'TyCon'.
-- See Note [Newtype eta]
-
- nt_co :: Maybe TyCon -- ^ A 'TyCon' (which is always a 'CoTyCon') that can have a 'Coercion'
- -- extracted from it to create the @newtype@ from the representation 'Type'.
- --
- -- This field is optional for non-recursive @newtype@s only.
+ nt_co :: CoAxiom -- The axiom coercion that creates the @newtype@ from
+ -- the representation 'Type'.
- -- See Note [Newtype coercions]
- -- Invariant: arity = #tvs in nt_etad_rhs;
- -- See Note [Newtype eta]
- -- Watch out! If any newtypes become transparent
- -- again check Trac #1072.
+ -- See Note [Newtype coercions]
+ -- Invariant: arity = #tvs in nt_etad_rhs;
+ -- See Note [Newtype eta]
+ -- Watch out! If any newtypes become transparent
+ -- again check Trac #1072.
}
-type AssocFamilyPermutation
- = Maybe [Int] -- Nothing for *top-level* type families
- -- For *associated* type families, gives the position
- -- of that 'TyVar' in the class argument list (0-indexed)
- -- e.g. class C a b c where { type F c a :: *->* }
- -- Then we get Just [2,0]
- -- For *synonyms*, the length of the list is identical to
- -- the TyCon's arity
- -- For *data types*, the length may be smaller than the
- -- TyCon's arity; e.g. class C a where { data D a :: *->* }
- -- here D gets arity 2
-
--- | Extract those 'DataCon's that we are able to learn about. Note that visibility in this sense does not
--- correspond to visibility in the context of any particular user program!
+-- | Extract those 'DataCon's that we are able to learn about. Note
+-- that visibility in this sense does not correspond to visibility in
+-- the context of any particular user program!
visibleDataCons :: AlgTyConRhs -> [DataCon]
visibleDataCons AbstractTyCon = []
-visibleDataCons OpenTyCon {} = []
+visibleDataCons DataFamilyTyCon {} = []
visibleDataCons (DataTyCon{ data_cons = cs }) = cs
visibleDataCons (NewTyCon{ data_con = c }) = [c]
| ClassTyCon
Class -- INVARIANT: the classTyCon of this Class is the current tycon
+ -- | An *associated* type of a class.
+ | AssocFamilyTyCon
+ Class -- The class in whose declaration the family is declared
+ -- The 'tyConTyVars' of this 'TyCon' may mention some
+ -- of the same type variables as the classTyVars of the
+ -- parent 'Class'. E.g.
+ --
+ -- @
+ -- class C a b where
+ -- data T c a
+ -- @
+ --
+ -- Here the 'a' is shared with the 'Class', and that is
+ -- important. In an instance declaration we expect the
+ -- two to be instantiated the same way. Eg.
+ --
+ -- @
+ -- instanc C [x] (Tree y) where
+ -- data T c [x] = T1 x | T2 c
+ -- @
+
-- | Type constructors representing an instance of a type family. Parameters:
--
-- 1) The type family in question
--
-- 3) A 'CoTyCon' identifying the representation
-- type with the type instance family
- | FamilyTyCon
- TyCon
- [Type]
- TyCon -- c.f. Note [Newtype coercions]
+ | FamInstTyCon -- See Note [Data type families]
+ -- and Note [Type synonym families]
+ TyCon -- The family TyCon
+ [Type] -- Argument types (mentions the tyConTyVars of this TyCon)
+ CoAxiom -- The coercion constructor
- --
-- E.g. data intance T [a] = ...
-- gives a representation tycon:
- -- data :R7T a = ...
- -- axiom co a :: T [a] ~ :R7T a
- -- with :R7T's algTcParent = FamilyTyCon T [a] co
+ -- data R:TList a = ...
+ -- axiom co a :: T [a] ~ R:TList a
+ -- with R:TList's algTcParent = FamInstTyCon T [a] co
-- | Checks the invariants of a 'TyConParent' given the appropriate type class name, if any
okParent :: Name -> TyConParent -> Bool
-okParent _ NoParentTyCon = True
-okParent tc_name (ClassTyCon cls) = tyConName (classTyCon cls) == tc_name
-okParent _ (FamilyTyCon fam_tc tys _co_tc) = tyConArity fam_tc == length tys
+okParent _ NoParentTyCon = True
+okParent tc_name (AssocFamilyTyCon cls) = tc_name `elem` map tyConName (classATs cls)
+okParent tc_name (ClassTyCon cls) = tc_name == tyConName (classTyCon cls)
+okParent _ (FamInstTyCon fam_tc tys _co_tc) = tyConArity fam_tc == length tys
+
+isNoParent :: TyConParent -> Bool
+isNoParent NoParentTyCon = True
+isNoParent _ = False
--------------------
-- | Information pertaining to the expansion of a type synonym (@type@)
data SynTyConRhs
- = OpenSynTyCon -- e.g. type family F x y :: * -> *
- Kind -- Kind of the "rhs"; ie *excluding type indices*
- -- In the example, the kind is (*->*)
- AssocFamilyPermutation
-
- | SynonymTyCon Type -- ^ The synonym mentions head type variables. It acts as a
- -- template for the expansion when the 'TyCon' is applied to some
- -- types.
-
---------------------
-data CoTyConDesc
- = CoSym | CoTrans
- | CoLeft | CoRight
- | CoCsel1 | CoCsel2 | CoCselR
- | CoInst
-
- | CoAxiom -- C tvs : F lhs-tys ~ rhs-ty
- { co_ax_tvs :: [TyVar]
- , co_ax_lhs :: Type
- , co_ax_rhs :: Type }
-
- | CoUnsafe
+ = -- | An ordinary type synonyn.
+ SynonymTyCon
+ Type -- This 'Type' is the rhs, and may mention from 'tyConTyVars'.
+ -- It acts as a template for the expansion when the 'TyCon'
+ -- is applied to some types.
+
+ -- | A type synonym family e.g. @type family F x y :: * -> *@
+ | SynFamilyTyCon
\end{code}
+Note [Enumeration types]
+~~~~~~~~~~~~~~~~~~~~~~~~
+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
+which is used by tagToEnum# to map Int# to constructors
+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)
and arity: 0
-Note [Indexed data types] (aka data type families)
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
- See also Note [Wrappers for data instance tycons] in MkId.lhs
-
-Consider
- data family T a
-
- data instance T (b,c) where
- T1 :: b -> c -> T (b,c)
-
-Then
- * T is the "family TyCon"
-
- * We make "representation TyCon" :R1T, thus:
- data :R1T b c where
- T1 :: forall b c. b -> c -> :R1T b c
-
- * It has a top-level coercion connecting it to the family TyCon
-
- axiom :Co:R1T b c : T (b,c) ~ :R1T b c
-
- * The data contructor T1 has a wrapper (which is what the source-level
- "T1" invokes):
-
- $WT1 :: forall b c. b -> c -> T (b,c)
- $WT1 b c (x::b) (y::c) = T1 b c x y `cast` sym (:Co:R1T b c)
+%************************************************************************
+%* *
+ Coercion axioms
+%* *
+%************************************************************************
- * The representation TyCon :R1T has an AlgTyConParent of
+\begin{code}
+-- | A 'CoAxiom' is a \"coercion constructor\", i.e. a named equality axiom.
+data CoAxiom
+ = CoAxiom -- type equality axiom.
+ { co_ax_unique :: Unique -- unique identifier
+ , co_ax_name :: Name -- name for pretty-printing
+ , co_ax_tvs :: [TyVar] -- bound type variables
+ , co_ax_lhs :: Type -- left-hand side of the equality
+ , co_ax_rhs :: Type -- right-hand side of the equality
+ }
- FamilyTyCon T [(b,c)] :Co:R1T
+coAxiomArity :: CoAxiom -> Arity
+coAxiomArity ax = length (co_ax_tvs ax)
+coAxiomName :: CoAxiom -> Name
+coAxiomName = co_ax_name
+\end{code}
%************************************************************************
tyConArity = 2
}
--- | This is the making of an algebraic 'TyCon'. Notably, you have to pass in the generic (in the -XGenerics sense)
--- information about the type constructor - you can get hold of it easily (see Generics module)
+-- | This is the making of an algebraic 'TyCon'. Notably, you have to
+-- pass in the generic (in the -XGenerics sense) information about the
+-- type constructor - you can get hold of it easily (see Generics
+-- module)
mkAlgTyCon :: Name
-> Kind -- ^ Kind of the resulting 'TyCon'
- -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'. Arity is inferred from the length of this list
+ -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'.
+ -- Arity is inferred from the length of this list
-> [PredType] -- ^ Stupid theta: see 'algTcStupidTheta'
-> AlgTyConRhs -- ^ Information about dat aconstructors
-> TyConParent
= AlgTyCon {
tyConName = name,
tyConUnique = nameUnique name,
- tc_kind = kind,
+ tc_kind = kind,
tyConArity = length tyvars,
tyConTyVars = tyvars,
algTcStupidTheta = stupid,
algTcParent = ASSERT( okParent name parent ) parent,
algTcRec = is_rec,
algTcGadtSyntax = gadt_syn,
- hasGenerics = gen_info
+ hasGenerics = gen_info
}
-- | Simpler specialization of 'mkAlgTyCon' for classes
synTcParent = parent
}
--- | Create a coercion 'TyCon'
-mkCoercionTyCon :: Name -> Arity
- -> CoTyConDesc
- -> TyCon
-mkCoercionTyCon name arity desc
- = CoTyCon {
- tyConName = name,
- tyConUnique = nameUnique name,
- tyConArity = arity,
- coTcDesc = desc }
-
mkAnyTyCon :: Name -> Kind -> TyCon
mkAnyTyCon name kind
= AnyTyCon { tyConName = name,
isUnLiftedTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
isUnLiftedTyCon _ = False
--- | Returns @True@ if the supplied 'TyCon' resulted from either a @data@ or @newtype@ declaration
+-- | Returns @True@ if the supplied 'TyCon' resulted from either a
+-- @data@ or @newtype@ declaration
isAlgTyCon :: TyCon -> Bool
isAlgTyCon (AlgTyCon {}) = True
isAlgTyCon (TupleTyCon {}) = True
-- get an info table. The family declaration 'TyCon' does not
isDataTyCon (AlgTyCon {algTcRhs = rhs})
= case rhs of
- OpenTyCon {} -> False
+ DataFamilyTyCon {} -> False
DataTyCon {} -> True
NewTyCon {} -> False
AbstractTyCon -> False -- We don't know, so return False
-- | Take a 'TyCon' apart into the 'TyVar's it scopes over, the 'Type' it expands
-- into, and (possibly) a coercion from the representation type to the @newtype@.
-- Returns @Nothing@ if this is not possible.
-unwrapNewTyCon_maybe :: TyCon -> Maybe ([TyVar], Type, Maybe TyCon)
+unwrapNewTyCon_maybe :: TyCon -> Maybe ([TyVar], Type, CoAxiom)
unwrapNewTyCon_maybe (AlgTyCon { tyConTyVars = tvs,
- algTcRhs = NewTyCon { nt_co = mb_co,
+ algTcRhs = NewTyCon { nt_co = co,
nt_rhs = rhs }})
- = Just (tvs, rhs, mb_co)
+ = Just (tvs, rhs, co)
unwrapNewTyCon_maybe _ = Nothing
isProductTyCon :: TyCon -> Bool
-- right hand side to which a synonym family application can expand.
--
--- | Is this a synonym 'TyCon' that can have no further instances appear?
-isClosedSynTyCon :: TyCon -> Bool
-isClosedSynTyCon tycon = isSynTyCon tycon && not (isOpenTyCon tycon)
-
--- | Is this a synonym 'TyCon' that can have may have further instances appear?
-isOpenSynTyCon :: TyCon -> Bool
-isOpenSynTyCon tycon = isSynTyCon tycon && isOpenTyCon tycon
-
isDecomposableTyCon :: TyCon -> Bool
--- True iff we can deocmpose (T a b c) into ((T a b) c)
--- Specifically NOT true of synonyms (open and otherwise) and coercions
+-- True iff we can decompose (T a b c) into ((T a b) c)
+-- Specifically NOT true of synonyms (open and otherwise)
isDecomposableTyCon (SynTyCon {}) = False
-isDecomposableTyCon (CoTyCon {}) = False
isDecomposableTyCon _other = True
-- | Is this an algebraic 'TyCon' declared with the GADT syntax?
-- | Is this an algebraic 'TyCon' which is just an enumeration of values?
isEnumerationTyCon :: TyCon -> Bool
+-- See Note [Enumeration types] in TyCon
isEnumerationTyCon (AlgTyCon {algTcRhs = DataTyCon { is_enum = res }}) = res
isEnumerationTyCon (TupleTyCon {tyConArity = arity}) = arity == 0
isEnumerationTyCon _ = False
-- | Is this a 'TyCon', synonym or otherwise, that may have further instances appear?
-isOpenTyCon :: TyCon -> Bool
-isOpenTyCon (SynTyCon {synTcRhs = OpenSynTyCon {}}) = True
-isOpenTyCon (AlgTyCon {algTcRhs = OpenTyCon {}}) = True
-isOpenTyCon _ = False
+isFamilyTyCon :: TyCon -> Bool
+isFamilyTyCon (SynTyCon {synTcRhs = SynFamilyTyCon {}}) = True
+isFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True
+isFamilyTyCon _ = False
+
+-- | Is this a synonym 'TyCon' that can have may have further instances appear?
+isSynFamilyTyCon :: TyCon -> Bool
+isSynFamilyTyCon (SynTyCon {synTcRhs = SynFamilyTyCon {}}) = True
+isSynFamilyTyCon _ = False
+
+-- | Is this a synonym 'TyCon' that can have may have further instances appear?
+isDataFamilyTyCon :: TyCon -> Bool
+isDataFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True
+isDataFamilyTyCon _ = False
+
+-- | Is this a synonym 'TyCon' that can have no further instances appear?
+isClosedSynTyCon :: TyCon -> Bool
+isClosedSynTyCon tycon = isSynTyCon tycon && not (isFamilyTyCon tycon)
-- | Injective 'TyCon's can be decomposed, so that
-- T ty1 ~ T ty2 => ty1 ~ ty2
-- Ultimately we may have injective associated types
-- in which case this test will become more interesting
--
- -- It'd be unusual to call isInjectiveTyCon on a regular H98
+ -- It'd be unusual to call isInjectiveTyCon on a regular H98
-- type synonym, because you should probably have expanded it first
-- But regardless, it's not injective!
--- | Extract the mapping from 'TyVar' indexes to indexes in the corresponding family
--- argument lists form an open 'TyCon' of any sort, if the given 'TyCon' is indeed
--- such a beast and that information is available
-assocTyConArgPoss_maybe :: TyCon -> Maybe [Int]
-assocTyConArgPoss_maybe (AlgTyCon {
- algTcRhs = OpenTyCon {otArgPoss = poss}}) = poss
-assocTyConArgPoss_maybe (SynTyCon { synTcRhs = OpenSynTyCon _ poss }) = poss
-assocTyConArgPoss_maybe _ = Nothing
-
-- | Are we able to extract informationa 'TyVar' to class argument list
-- mappping from a given 'TyCon'?
isTyConAssoc :: TyCon -> Bool
-isTyConAssoc = isJust . assocTyConArgPoss_maybe
-
--- | Set the AssocFamilyPermutation structure in an
--- associated data or type synonym. The [TyVar] are the
--- class type variables. Remember, the tyvars of an associated
--- data/type are a subset of the class tyvars; except that an
--- associated data type can have extra type variables at the
--- end (see Note [Avoid name clashes for associated data types] in TcHsType)
-setTyConArgPoss :: [TyVar] -> TyCon -> TyCon
-setTyConArgPoss clas_tvs tc
- = case tc of
- AlgTyCon { algTcRhs = rhs } -> tc { algTcRhs = rhs {otArgPoss = Just ps} }
- SynTyCon { synTcRhs = OpenSynTyCon ki _ } -> tc { synTcRhs = OpenSynTyCon ki (Just ps) }
- _ -> pprPanic "setTyConArgPoss" (ppr tc)
- where
- ps = catMaybes [tv `elemIndex` clas_tvs | tv <- tyConTyVars tc]
- -- We will get Nothings for the "extra" type variables in an
- -- associated data type
+isTyConAssoc tc = case tyConParent tc of
+ AssocFamilyTyCon {} -> True
+ _ -> False
-- The unit tycon didn't used to be classed as a tuple tycon
-- but I thought that was silly so I've undone it
isAnyTyCon (AnyTyCon {}) = True
isAnyTyCon _ = False
--- | Attempt to pull a 'TyCon' apart into the arity and 'coKindFun' of
--- a coercion 'TyCon'. Returns @Nothing@ if the 'TyCon' is not of the
--- appropriate kind
-isCoercionTyCon_maybe :: TyCon -> Maybe (Arity, CoTyConDesc)
-isCoercionTyCon_maybe (CoTyCon {tyConArity = ar, coTcDesc = desc})
- = Just (ar, desc)
-isCoercionTyCon_maybe _ = Nothing
-
--- | Is this a 'TyCon' that represents a coercion?
-isCoercionTyCon :: TyCon -> Bool
-isCoercionTyCon (CoTyCon {}) = True
-isCoercionTyCon _ = False
-
-- | Identifies implicit tycons that, in particular, do not go into interface
-- files (because they are implicitly reconstructed when the interface is
-- read).
\begin{code}
tcExpandTyCon_maybe, coreExpandTyCon_maybe
:: TyCon
- -> [Type] -- ^ Arguments to 'TyCon'
- -> Maybe ([(TyVar,Type)],
+ -> [tyco] -- ^ Arguments to 'TyCon'
+ -> Maybe ([(TyVar,tyco)],
Type,
- [Type]) -- ^ Returns a 'TyVar' substitution, the body type
- -- of the synonym (not yet substituted) and any arguments
- -- remaining from the application
+ [tyco]) -- ^ Returns a 'TyVar' substitution, the body type
+ -- of the synonym (not yet substituted) and any arguments
+ -- remaining from the application
--- ^ Used to create the view the /typechecker/ has on 'TyCon's. We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
+-- ^ Used to create the view the /typechecker/ has on 'TyCon's.
+-- We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
tcExpandTyCon_maybe (SynTyCon {tyConTyVars = tvs,
synTcRhs = SynonymTyCon rhs }) tys
= expand tvs rhs tys
---------------
--- ^ Used to create the view /Core/ has on 'TyCon's. We expand not only closed synonyms like 'tcExpandTyCon_maybe',
+-- ^ Used to create the view /Core/ has on 'TyCon's. We expand
+-- not only closed synonyms like 'tcExpandTyCon_maybe',
-- but also non-recursive @newtype@s
-coreExpandTyCon_maybe (AlgTyCon {
- algTcRhs = NewTyCon { nt_etad_rhs = etad_rhs, nt_co = Nothing }}) tys
- = case etad_rhs of -- Don't do this in the pattern match, lest we accidentally
- -- match the etad_rhs of a *recursive* newtype
- (tvs,rhs) -> expand tvs rhs tys
-
coreExpandTyCon_maybe tycon tys = tcExpandTyCon_maybe tycon tys
----------------
-expand :: [TyVar] -> Type -- Template
- -> [Type] -- Args
- -> Maybe ([(TyVar,Type)], Type, [Type]) -- Expansion
+expand :: [TyVar] -> Type -- Template
+ -> [a] -- Args
+ -> Maybe ([(TyVar,a)], Type, [a]) -- Expansion
expand tvs rhs tys
= case n_tvs `compare` length tys of
LT -> Just (tvs `zip` tys, rhs, drop n_tvs tys)
EQ -> Just (tvs `zip` tys, rhs, [])
- GT -> Nothing
+ GT -> Nothing
where
n_tvs = length tvs
\end{code}
tyConHasKind :: TyCon -> Bool
tyConHasKind (SuperKindTyCon {}) = False
-tyConHasKind (CoTyCon {}) = False
tyConHasKind _ = True
-- | As 'tyConDataCons_maybe', but returns the empty list of constructors if no constructors
tyConFamilySize :: TyCon -> Int
tyConFamilySize (AlgTyCon {algTcRhs = DataTyCon {data_cons = cons}}) =
length cons
-tyConFamilySize (AlgTyCon {algTcRhs = NewTyCon {}}) = 1
-tyConFamilySize (AlgTyCon {algTcRhs = OpenTyCon {}}) = 0
-tyConFamilySize (TupleTyCon {}) = 1
+tyConFamilySize (AlgTyCon {algTcRhs = NewTyCon {}}) = 1
+tyConFamilySize (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = 0
+tyConFamilySize (TupleTyCon {}) = 1
tyConFamilySize other = pprPanic "tyConFamilySize:" (ppr other)
-- | Extract an 'AlgTyConRhs' with information about data constructors from an algebraic or tuple
-- | Extracts the @newtype@ coercion from such a 'TyCon', which can be used to construct something
-- with the @newtype@s type from its representation type (right hand side). If the supplied 'TyCon'
-- is not a @newtype@, returns @Nothing@
-newTyConCo_maybe :: TyCon -> Maybe TyCon
-newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = co
-newTyConCo_maybe _ = Nothing
+newTyConCo_maybe :: TyCon -> Maybe CoAxiom
+newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = Just co
+newTyConCo_maybe _ = Nothing
+
+newTyConCo :: TyCon -> CoAxiom
+newTyConCo tc = case newTyConCo_maybe tc of
+ Just co -> co
+ Nothing -> pprPanic "newTyConCo" (ppr tc)
-- | Find the primitive representation of a 'TyCon'
tyConPrimRep :: TyCon -> PrimRep
synTyConType tc = case synTcRhs tc of
SynonymTyCon t -> t
_ -> pprPanic "synTyConType" (ppr tc)
-
--- | Find the 'Kind' of an open type synonym. Panics if the 'TyCon' is not an open type synonym
-synTyConResKind :: TyCon -> Kind
-synTyConResKind (SynTyCon {synTcRhs = OpenSynTyCon kind _}) = kind
-synTyConResKind tycon = pprPanic "synTyConResKind" (ppr tycon)
\end{code}
\begin{code}
tyConClass_maybe (AlgTyCon {algTcParent = ClassTyCon clas}) = Just clas
tyConClass_maybe _ = Nothing
+----------------------------------------------------------------------------
+tyConParent :: TyCon -> TyConParent
+tyConParent (AlgTyCon {algTcParent = parent}) = parent
+tyConParent (SynTyCon {synTcParent = parent}) = parent
+tyConParent _ = NoParentTyCon
+
+----------------------------------------------------------------------------
-- | Is this 'TyCon' that for a family instance, be that for a synonym or an
-- algebraic family instance?
isFamInstTyCon :: TyCon -> Bool
-isFamInstTyCon (AlgTyCon {algTcParent = FamilyTyCon _ _ _ }) = True
-isFamInstTyCon (SynTyCon {synTcParent = FamilyTyCon _ _ _ }) = True
-isFamInstTyCon _ = False
+isFamInstTyCon tc = case tyConParent tc of
+ FamInstTyCon {} -> True
+ _ -> False
+
+tyConFamInstSig_maybe :: TyCon -> Maybe (TyCon, [Type], CoAxiom)
+tyConFamInstSig_maybe tc
+ = case tyConParent tc of
+ FamInstTyCon f ts co_tc -> Just (f, ts, co_tc)
+ _ -> Nothing
-- | If this 'TyCon' is that of a family instance, return the family in question
-- and the instance types. Otherwise, return @Nothing@
tyConFamInst_maybe :: TyCon -> Maybe (TyCon, [Type])
-tyConFamInst_maybe (AlgTyCon {algTcParent = FamilyTyCon fam instTys _}) =
- Just (fam, instTys)
-tyConFamInst_maybe (SynTyCon {synTcParent = FamilyTyCon fam instTys _}) =
- Just (fam, instTys)
-tyConFamInst_maybe _ =
- Nothing
+tyConFamInst_maybe tc
+ = case tyConParent tc of
+ FamInstTyCon f ts _ -> Just (f, ts)
+ _ -> Nothing
-- | If this 'TyCon' is that of a family instance, return a 'TyCon' which represents
-- a coercion identifying the representation type with the type instance family.
-- Otherwise, return @Nothing@
-tyConFamilyCoercion_maybe :: TyCon -> Maybe TyCon
-tyConFamilyCoercion_maybe (AlgTyCon {algTcParent = FamilyTyCon _ _ coe}) =
- Just coe
-tyConFamilyCoercion_maybe (SynTyCon {synTcParent = FamilyTyCon _ _ coe}) =
- Just coe
-tyConFamilyCoercion_maybe _ =
- Nothing
+tyConFamilyCoercion_maybe :: TyCon -> Maybe CoAxiom
+tyConFamilyCoercion_maybe tc
+ = case tyConParent tc of
+ FamInstTyCon _ _ co -> Just co
+ _ -> Nothing
\end{code}
instance Uniquable TyCon where
getUnique tc = tyConUnique tc
-instance Outputable CoTyConDesc where
- ppr CoSym = ptext (sLit "SYM")
- ppr CoTrans = ptext (sLit "TRANS")
- ppr CoLeft = ptext (sLit "LEFT")
- ppr CoRight = ptext (sLit "RIGHT")
- ppr CoCsel1 = ptext (sLit "CSEL1")
- ppr CoCsel2 = ptext (sLit "CSEL2")
- ppr CoCselR = ptext (sLit "CSELR")
- ppr CoInst = ptext (sLit "INST")
- ppr CoUnsafe = ptext (sLit "UNSAFE")
- ppr (CoAxiom {}) = ptext (sLit "AXIOM")
-
instance Outputable TyCon where
ppr tc = ppr (getName tc)
instance NamedThing TyCon where
getName = tyConName
+
+instance Data.Typeable TyCon where
+ typeOf _ = Data.mkTyConApp (Data.mkTyCon "TyCon") []
+
+instance Data.Data TyCon where
+ -- don't traverse?
+ toConstr _ = abstractConstr "TyCon"
+ gunfold _ _ = error "gunfold"
+ dataTypeOf _ = mkNoRepType "TyCon"
+
+-------------------
+instance Eq CoAxiom where
+ a == b = case (a `compare` b) of { EQ -> True; _ -> False }
+ a /= b = case (a `compare` b) of { EQ -> False; _ -> True }
+
+instance Ord CoAxiom where
+ a <= b = case (a `compare` b) of { LT -> True; EQ -> True; GT -> False }
+ a < b = case (a `compare` b) of { LT -> True; EQ -> False; GT -> False }
+ a >= b = case (a `compare` b) of { LT -> False; EQ -> True; GT -> True }
+ a > b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True }
+ compare a b = getUnique a `compare` getUnique b
+
+instance Uniquable CoAxiom where
+ getUnique = co_ax_unique
+
+instance Outputable CoAxiom where
+ ppr = ppr . getName
+
+instance NamedThing CoAxiom where
+ getName = co_ax_name
+
+instance Data.Typeable CoAxiom where
+ typeOf _ = Data.mkTyConApp (Data.mkTyCon "CoAxiom") []
+
+instance Data.Data CoAxiom where
+ -- don't traverse?
+ toConstr _ = abstractConstr "CoAxiom"
+ gunfold _ _ = error "gunfold"
+ dataTypeOf _ = mkNoRepType "CoAxiom"
\end{code}
projects / ghc-hetmet.git / blobdiff