module TyCon( -- * Main TyCon data types TyCon, FieldLabel, AlgTyConRhs(..), visibleDataCons, TyConParent(..), isNoParent, SynTyConRhs(..), Role(..), -- ** Constructing TyCons mkAlgTyCon, mkClassTyCon, mkFunTyCon, mkPrimTyCon, mkKindTyCon, mkLiftedPrimTyCon, mkTupleTyCon, mkSynTyCon, mkForeignTyCon, mkPromotedDataCon, mkPromotedTyCon, -- ** Predicates on TyCons isAlgTyCon, isClassTyCon, isFamInstTyCon, isFunTyCon, isPrimTyCon, isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon, isSynTyCon, isDecomposableTyCon, isForeignTyCon, isPromotedDataCon, isPromotedTyCon, isPromotedDataCon_maybe, isPromotedTyCon_maybe, promotableTyCon_maybe, promoteTyCon, isInjectiveTyCon, isDataTyCon, isProductTyCon, isDataProductTyCon_maybe, isEnumerationTyCon, isNewTyCon, isAbstractTyCon, isFamilyTyCon, isOpenFamilyTyCon, isSynFamilyTyCon, isDataFamilyTyCon, isOpenSynFamilyTyCon, isClosedSynFamilyTyCon_maybe, isBuiltInSynFamTyCon_maybe, isUnLiftedTyCon, isGadtSyntaxTyCon, isDistinctTyCon, isDistinctAlgRhs, isTyConAssoc, tyConAssoc_maybe, isRecursiveTyCon, isImplicitTyCon, -- ** Extracting information out of TyCons tyConName, tyConKind, tyConUnique, tyConTyVars, tyConCType, tyConCType_maybe, tyConDataCons, tyConDataCons_maybe, tyConSingleDataCon_maybe, tyConSingleAlgDataCon_maybe, tyConFamilySize, tyConStupidTheta, tyConArity, tyConRoles, tyConParent, tyConTuple_maybe, tyConClass_maybe, tyConFamInst_maybe, tyConFamInstSig_maybe, tyConFamilyCoercion_maybe, synTyConDefn_maybe, synTyConRhs_maybe, tyConExtName, -- External name for foreign types algTyConRhs, newTyConRhs, newTyConEtadArity, newTyConEtadRhs, unwrapNewTyCon_maybe, tupleTyConBoxity, tupleTyConSort, tupleTyConArity, -- ** Manipulating TyCons tcExpandTyCon_maybe, coreExpandTyCon_maybe, makeTyConAbstract, newTyConCo, newTyConCo_maybe, pprPromotionQuote, -- * Primitive representations of Types PrimRep(..), PrimElemRep(..), tyConPrimRep, isVoidRep, isGcPtrRep, primRepSizeW, primElemRepSizeB, -- * Recursion breaking RecTcChecker, initRecTc, checkRecTc ) where #include "HsVersions.h" import {-# SOURCE #-} TypeRep ( Kind, Type, PredType ) import {-# SOURCE #-} DataCon ( DataCon, isVanillaDataCon ) import Var import Class import BasicTypes import DynFlags import ForeignCall import Name import NameSet import CoAxiom import PrelNames import Maybes import Outputable import FastString import Constants import Util import qualified Data.Data as Data import Data.Typeable (Typeable)\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 OpenSynFamilyTyCon type family G a :: * where G Int = Bool G Bool = Char G a = () translates to a SynTyCon 'G', whose SynTyConRhs is ClosedSynFamilyTyCon, with the appropriate CoAxiom representing the equations * In the future we might want to support * injective type families (allow decomposition) but we don't at the moment [2013] 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 * 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. Note [Associated families and their parent class] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ *Associated* families are just like *non-associated* families, except that they have a TyConParent of AssocFamilyTyCon, which identifies the parent class. However there is an important sharing relationship between * the tyConTyVars of the parent Class * the tyConTyvars of the associated TyCon class C a b where data T p a type F a q b Here the 'a' and 'b' are shared with the 'Class'; that is, they have the same Unique. This is important. In an instance declaration we expect * all the shared variables to be instantiated the same way * the non-shared variables of the associated type should not be instantiated at all instance C [x] (Tree y) where data T p [x] = T1 x | T2 p type F [x] q (Tree y) = (x,y,q) Note [TyCon Role signatures] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Every tycon has a role signature, assigning a role to each of the tyConTyVars (or of equal length to the tyConArity, if there are no tyConTyVars). An example demonstrates these best: say we have a tycon T, with parameters a at nominal, b at representational, and c at phantom. Then, to prove representational equality between T a1 b1 c1 and T a2 b2 c2, we need to have nominal equality between a1 and a2, representational equality between b1 and b2, and nothing in particular (i.e., phantom equality) between c1 and c2. This might happen, say, with the following declaration: data T a b c where MkT :: b -> T Int b c Data and class tycons have their roles inferred (see inferRoles in TcTyDecls), as do vanilla synonym tycons. Family tycons have all parameters at role N, though it is conceivable that we could relax this restriction. (->)'s and tuples' parameters are at role R. Each primitive tycon declares its roles; it's worth noting that (~#)'s parameters are at role N. Promoted data constructors' type arguments are at role R. All kind arguments are at role N. %************************************************************************ %* * \subsection{The data type} %* * %************************************************************************ \begin{code}

-- | TyCons represent type constructors. Type constructors are introduced by things such as: -- -- 1) Data declarations: @data Foo = ...@ creates the @Foo@ type constructor of kind @*@ -- -- 2) Type synonyms: @type Foo = ...@ creates the @Foo@ type constructor -- -- 3) Newtypes: @newtype Foo a = MkFoo ...@ creates the @Foo@ type constructor of kind @* -> *@ -- -- 4) Class declarations: @class Foo where@ creates the @Foo@ type constructor of kind @*@ -- -- This data type also encodes a number of primitive, built in type constructors such as those -- for function and tuple types. -- If you edit this type, you may need to update the GHC formalism -- See Note [GHC Formalism] in coreSyn/CoreLint.lhs data TyCon = -- | The function type constructor, @(->)@ FunTyCon { tyConUnique :: Unique, tyConName :: Name, tc_kind :: Kind, 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. | AlgTyCon { tyConUnique :: Unique, tyConName :: Name, tc_kind :: Kind, tyConArity :: Arity, tyConTyVars :: [TyVar], -- ^ The kind and 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. tc_roles :: [Role], -- ^ The role for each type variable -- This list has the same length as tyConTyVars -- See also Note [TyCon Role signatures] tyConCType :: Maybe CType, -- The C type that should be used -- for this type when using the FFI -- and CAPI 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 algTcParent :: TyConParent, -- ^ Gives the class or family declaration 'TyCon' -- for derived 'TyCon's representing class -- or family instances, respectively. -- See also 'synTcParent' tcPromoted :: Maybe TyCon -- ^ Promoted TyCon, if any } -- | Represents the infinite family of tuple type constructors, -- @()@, @(a,b)@, @(# a, b #)@ etc. | TupleTyCon { tyConUnique :: Unique, tyConName :: Name, tc_kind :: Kind, tyConArity :: Arity, tyConTupleSort :: TupleSort, tyConTyVars :: [TyVar], dataCon :: DataCon, -- ^ Corresponding tuple data constructor tcPromoted :: Maybe TyCon -- Nothing for unboxed tuples } -- | Represents type synonyms | SynTyCon { tyConUnique :: Unique, tyConName :: Name, tc_kind :: Kind, tyConArity :: Arity, tyConTyVars :: [TyVar], -- Bound tyvars tc_roles :: [Role], synTcRhs :: SynTyConRhs, -- ^ Contains information about the -- expansion of the synonym 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 | PrimTyCon { tyConUnique :: Unique, tyConName :: Name, tc_kind :: Kind, tyConArity :: Arity, tc_roles :: [Role], 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 tyConExtName :: Maybe FastString -- ^ @Just e@ for foreign-imported types, -- holds the name of the imported thing } -- | Represents promoted data constructor. | PromotedDataCon { -- See Note [Promoted data constructors] tyConUnique :: Unique, -- ^ Same Unique as the data constructor tyConName :: Name, -- ^ Same Name as the data constructor tyConArity :: Arity, tc_roles :: [Role], -- ^ Roles: N for kind vars, R for type vars tc_kind :: Kind, -- ^ Translated type of the data constructor dataCon :: DataCon -- ^ Corresponding data constructor } -- | Represents promoted type constructor. | PromotedTyCon { tyConUnique :: Unique, -- ^ Same Unique as the type constructor tyConName :: Name, -- ^ Same Name as the type constructor tyConArity :: Arity, -- ^ n if ty_con :: * -> ... -> * n times tc_kind :: Kind, -- ^ Always TysPrim.superKind ty_con :: TyCon -- ^ Corresponding type constructor } deriving Typeable -- | Names of the fields in an algebraic record type type FieldLabel = Name -- | 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. = AbstractTyCon Bool -- True <=> It's definitely a distinct data type, -- equal only to itself; ie not a newtype -- False <=> Not sure -- See Note [AbstractTyCon and type equality] -- | 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 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 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' 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'. -- See Note [Newtype eta] nt_co :: CoAxiom Unbranched -- 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. }\end{code} Note [AbstractTyCon and type equality] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ TODO \begin{code}

-- | 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 DataFamilyTyCon {} = [] visibleDataCons (DataTyCon{ data_cons = cs }) = cs visibleDataCons (NewTyCon{ data_con = c }) = [c] -- ^ Both type classes as well as family instances imply implicit -- type constructors. These implicit type constructors refer to their parent -- structure (ie, the class or family from which they derive) using a type of -- the following form. We use 'TyConParent' for both algebraic and synonym -- types, but the variant 'ClassTyCon' will only be used by algebraic 'TyCon's. data TyConParent = -- | An ordinary type constructor has no parent. NoParentTyCon -- | Type constructors representing a class dictionary. -- See Note [ATyCon for classes] in TypeRep | 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 -- See Note [Associated families and their parent class] -- | Type constructors representing an instance of a *data* family. Parameters: -- -- 1) The type family in question -- -- 2) Instance types; free variables are the 'tyConTyVars' -- of the current 'TyCon' (not the family one). INVARIANT: -- the number of types matches the arity of the family 'TyCon' -- -- 3) A 'CoTyCon' identifying the representation -- type with the type instance family | FamInstTyCon -- See Note [Data type families] (CoAxiom Unbranched) -- The coercion constructor, -- always of kind T ty1 ty2 ~ R:T a b c -- where T is the family TyCon, -- and R:T is the representation TyCon (ie this one) -- and a,b,c are the tyConTyVars of this TyCon -- Cached fields of the CoAxiom, but adjusted to -- use the tyConTyVars of this TyCon TyCon -- The family TyCon [Type] -- Argument types (mentions the tyConTyVars of this TyCon) -- Match in length the tyConTyVars of the family TyCon -- E.g. data intance T [a] = ... -- gives a representation tycon: -- data R:TList a = ... -- axiom co a :: T [a] ~ R:TList a -- with R:TList's algTcParent = FamInstTyCon T [a] co instance Outputable TyConParent where ppr NoParentTyCon = text "No parent" ppr (ClassTyCon cls) = text "Class parent" <+> ppr cls ppr (AssocFamilyTyCon cls) = text "Class parent (assoc. family)" <+> ppr cls ppr (FamInstTyCon _ tc tys) = text "Family parent (family instance)" <+> ppr tc <+> sep (map ppr tys) -- | Checks the invariants of a 'TyConParent' given the appropriate type class name, if any okParent :: Name -> TyConParent -> Bool 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) = 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 = -- | 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. -- | An open type synonym family e.g. @type family F x y :: * -> *@ | OpenSynFamilyTyCon -- | A closed type synonym family e.g. @type family F x where { F Int = Bool }@ | ClosedSynFamilyTyCon (CoAxiom Branched) -- The one axiom for this family -- | A closed type synonym family declared in an hs-boot file with -- type family F a where .. | AbstractClosedSynFamilyTyCon | BuiltInSynFamTyCon BuiltInSynFamily\end{code} Note [Closed type families] ~~~~~~~~~~~~~~~~~~~~~~~~~ * In an open type family you can add new instances later. This is the usual case. * In a closed type family you can only put equations where the family is defined. Note [Promoted data constructors] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ A data constructor can be promoted to become a type constructor, via the PromotedTyCon alternative in TyCon. * Only data constructors with (a) no kind polymorphism (b) no constraints in its type (eg GADTs) are promoted. Existentials are ok; see Trac #7347. * The TyCon promoted from a DataCon has the *same* Name and Unique as the DataCon. Eg. If the data constructor Data.Maybe.Just(unique 78, say) is promoted to a TyCon whose name is Data.Maybe.Just(unique 78) * The *kind* of a promoted DataCon may be polymorphic. Example: type of DataCon Just :: forall (a:*). a -> Maybe a kind of (promoted) tycon Just :: forall (a:box). a -> Maybe a The kind is not identical to the type, because of the */box kind signature on the forall'd variable; so the tc_kind field of PromotedTyCon is not identical to the dataConUserType of the DataCon. But it's the same modulo changing the variable kinds, done by DataCon.promoteType. * Small note: We promote the *user* type of the DataCon. Eg data T = MkT {-# UNPACK #-} !(Bool, Bool) The promoted kind is MkT :: (Bool,Bool) -> T *not* MkT :: Bool -> Bool -> T 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

-- | A 'PrimRep' is an abstraction of a type. It contains information that -- the code generator needs in order to pass arguments, return results, -- and store values of this type. data PrimRep = VoidRep | PtrRep | IntRep -- ^ Signed, word-sized value | WordRep -- ^ Unsigned, word-sized value | Int64Rep -- ^ Signed, 64 bit value (with 32-bit words only) | Word64Rep -- ^ Unsigned, 64 bit value (with 32-bit words only) | AddrRep -- ^ A pointer, but /not/ to a Haskell value (use 'PtrRep') | FloatRep | DoubleRep | VecRep Int PrimElemRep -- ^ A vector deriving( Eq, Show ) data PrimElemRep = Int8ElemRep | Int16ElemRep | Int32ElemRep | Int64ElemRep | Word8ElemRep | Word16ElemRep | Word32ElemRep | Word64ElemRep | FloatElemRep | DoubleElemRep deriving( Eq, Show ) instance Outputable PrimRep where ppr r = text (show r) instance Outputable PrimElemRep where ppr r = text (show r) isVoidRep :: PrimRep -> Bool isVoidRep VoidRep = True isVoidRep _other = False isGcPtrRep :: PrimRep -> Bool isGcPtrRep PtrRep = True isGcPtrRep _ = False -- | Find the size of a 'PrimRep', in words primRepSizeW :: DynFlags -> PrimRep -> Int primRepSizeW _ IntRep = 1 primRepSizeW _ WordRep = 1 primRepSizeW dflags Int64Rep = wORD64_SIZE `quot` wORD_SIZE dflags primRepSizeW dflags Word64Rep = wORD64_SIZE `quot` wORD_SIZE dflags primRepSizeW _ FloatRep = 1 -- NB. might not take a full word primRepSizeW dflags DoubleRep = dOUBLE_SIZE dflags `quot` wORD_SIZE dflags primRepSizeW _ AddrRep = 1 primRepSizeW _ PtrRep = 1 primRepSizeW _ VoidRep = 0 primRepSizeW dflags (VecRep len rep) = len * primElemRepSizeB rep `quot` wORD_SIZE dflags primElemRepSizeB :: PrimElemRep -> Int primElemRepSizeB Int8ElemRep = 1 primElemRepSizeB Int16ElemRep = 2 primElemRepSizeB Int32ElemRep = 4 primElemRepSizeB Int64ElemRep = 8 primElemRepSizeB Word8ElemRep = 1 primElemRepSizeB Word16ElemRep = 2 primElemRepSizeB Word32ElemRep = 4 primElemRepSizeB Word64ElemRep = 8 primElemRepSizeB FloatElemRep = 4 primElemRepSizeB DoubleElemRep = 8\end{code} %************************************************************************ %* * \subsection{TyCon Construction} %* * %************************************************************************ Note: the TyCon constructors all take a Kind as one argument, even though they could, in principle, work out their Kind from their other arguments. But to do so they need functions from Types, and that makes a nasty module mutual-recursion. And they aren't called from many places. So we compromise, and move their Kind calculation to the call site. \begin{code}

-- | Given the name of the function type constructor and it's kind, create the -- corresponding 'TyCon'. It is reccomended to use 'TypeRep.funTyCon' if you want -- this functionality mkFunTyCon :: Name -> Kind -> TyCon mkFunTyCon name kind = FunTyCon { tyConUnique = nameUnique name, tyConName = name, tc_kind = kind, 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) mkAlgTyCon :: Name -> Kind -- ^ Kind of the resulting 'TyCon' -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'. -- Arity is inferred from the length of this list -> [Role] -- ^ The roles for each TyVar -> Maybe CType -- ^ The C type this type corresponds to -- when using the CAPI FFI -> [PredType] -- ^ Stupid theta: see 'algTcStupidTheta' -> AlgTyConRhs -- ^ Information about dat aconstructors -> TyConParent -> RecFlag -- ^ Is the 'TyCon' recursive? -> Bool -- ^ Was the 'TyCon' declared with GADT syntax? -> Maybe TyCon -- ^ Promoted version -> TyCon mkAlgTyCon name kind tyvars roles cType stupid rhs parent is_rec gadt_syn prom_tc = AlgTyCon { tyConName = name, tyConUnique = nameUnique name, tc_kind = kind, tyConArity = length tyvars, tyConTyVars = tyvars, tc_roles = roles, tyConCType = cType, algTcStupidTheta = stupid, algTcRhs = rhs, algTcParent = ASSERT2( okParent name parent, ppr name $$ ppr parent ) parent, algTcRec = is_rec, algTcGadtSyntax = gadt_syn, tcPromoted = prom_tc } -- | Simpler specialization of 'mkAlgTyCon' for classes mkClassTyCon :: Name -> Kind -> [TyVar] -> [Role] -> AlgTyConRhs -> Class -> RecFlag -> TyCon mkClassTyCon name kind tyvars roles rhs clas is_rec = mkAlgTyCon name kind tyvars roles Nothing [] rhs (ClassTyCon clas) is_rec False Nothing -- Class TyCons are not pormoted mkTupleTyCon :: Name -> Kind -- ^ Kind of the resulting 'TyCon' -> Arity -- ^ Arity of the tuple -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars' -> DataCon -> TupleSort -- ^ Whether the tuple is boxed or unboxed -> Maybe TyCon -- ^ Promoted version -> TyCon mkTupleTyCon name kind arity tyvars con sort prom_tc = TupleTyCon { tyConUnique = nameUnique name, tyConName = name, tc_kind = kind, tyConArity = arity, tyConTupleSort = sort, tyConTyVars = tyvars, dataCon = con, tcPromoted = prom_tc } -- ^ Foreign-imported (.NET) type constructors are represented -- as primitive, but /lifted/, 'TyCons' for now. They are lifted -- because the Haskell type @T@ representing the (foreign) .NET -- type @T@ is actually implemented (in ILX) as a @thunk<T>@ mkForeignTyCon :: Name -> Maybe FastString -- ^ Name of the foreign imported thing, maybe -> Kind -> TyCon mkForeignTyCon name ext_name kind = PrimTyCon { tyConName = name, tyConUnique = nameUnique name, tc_kind = kind, tyConArity = 0, tc_roles = [], primTyConRep = PtrRep, -- they all do isUnLifted = False, tyConExtName = ext_name } -- | Create an unlifted primitive 'TyCon', such as @Int#@ mkPrimTyCon :: Name -> Kind -> [Role] -> PrimRep -> TyCon mkPrimTyCon name kind roles rep = mkPrimTyCon' name kind roles rep True -- | Kind constructors mkKindTyCon :: Name -> Kind -> TyCon mkKindTyCon name kind = mkPrimTyCon' name kind [] VoidRep True -- | Create a lifted primitive 'TyCon' such as @RealWorld@ mkLiftedPrimTyCon :: Name -> Kind -> [Role] -> PrimRep -> TyCon mkLiftedPrimTyCon name kind roles rep = mkPrimTyCon' name kind roles rep False mkPrimTyCon' :: Name -> Kind -> [Role] -> PrimRep -> Bool -> TyCon mkPrimTyCon' name kind roles rep is_unlifted = PrimTyCon { tyConName = name, tyConUnique = nameUnique name, tc_kind = kind, tyConArity = length roles, tc_roles = roles, primTyConRep = rep, isUnLifted = is_unlifted, tyConExtName = Nothing } -- | Create a type synonym 'TyCon' mkSynTyCon :: Name -> Kind -> [TyVar] -> [Role] -> SynTyConRhs -> TyConParent -> TyCon mkSynTyCon name kind tyvars roles rhs parent = SynTyCon { tyConName = name, tyConUnique = nameUnique name, tc_kind = kind, tyConArity = length tyvars, tyConTyVars = tyvars, tc_roles = roles, synTcRhs = rhs, synTcParent = parent } -- | Create a promoted data constructor 'TyCon' -- Somewhat dodgily, we give it the same Name -- as the data constructor itself; when we pretty-print -- the TyCon we add a quote; see the Outputable TyCon instance mkPromotedDataCon :: DataCon -> Name -> Unique -> Kind -> [Role] -> TyCon mkPromotedDataCon con name unique kind roles = PromotedDataCon { tyConName = name, tyConUnique = unique, tyConArity = arity, tc_roles = roles, tc_kind = kind, dataCon = con } where arity = length roles -- | Create a promoted type constructor 'TyCon' -- Somewhat dodgily, we give it the same Name -- as the type constructor itself mkPromotedTyCon :: TyCon -> Kind -> TyCon mkPromotedTyCon tc kind = PromotedTyCon { tyConName = getName tc, tyConUnique = getUnique tc, tyConArity = tyConArity tc, tc_kind = kind, ty_con = tc }\end{code} \begin{code}

isFunTyCon :: TyCon -> Bool isFunTyCon (FunTyCon {}) = True isFunTyCon _ = False -- | Test if the 'TyCon' is algebraic but abstract (invisible data constructors) isAbstractTyCon :: TyCon -> Bool isAbstractTyCon (AlgTyCon { algTcRhs = AbstractTyCon {} }) = True isAbstractTyCon _ = False -- | Make an algebraic 'TyCon' abstract. Panics if the supplied 'TyCon' is not algebraic makeTyConAbstract :: TyCon -> TyCon makeTyConAbstract tc@(AlgTyCon { algTcRhs = rhs }) = tc { algTcRhs = AbstractTyCon (isDistinctAlgRhs rhs) } makeTyConAbstract tc = pprPanic "makeTyConAbstract" (ppr tc) -- | Does this 'TyCon' represent something that cannot be defined in Haskell? isPrimTyCon :: TyCon -> Bool isPrimTyCon (PrimTyCon {}) = True isPrimTyCon _ = False -- | Is this 'TyCon' unlifted (i.e. cannot contain bottom)? Note that this can only -- be true for primitive and unboxed-tuple 'TyCon's isUnLiftedTyCon :: TyCon -> Bool isUnLiftedTyCon (PrimTyCon {isUnLifted = is_unlifted}) = is_unlifted isUnLiftedTyCon (TupleTyCon {tyConTupleSort = sort}) = not (isBoxed (tupleSortBoxity sort)) isUnLiftedTyCon _ = False -- | Returns @True@ if the supplied 'TyCon' resulted from either a -- @data@ or @newtype@ declaration isAlgTyCon :: TyCon -> Bool isAlgTyCon (AlgTyCon {}) = True isAlgTyCon (TupleTyCon {}) = True isAlgTyCon _ = False isDataTyCon :: TyCon -> Bool -- ^ Returns @True@ for data types that are /definitely/ represented by -- heap-allocated constructors. These are scrutinised by Core-level -- @case@ expressions, and they get info tables allocated for them. -- -- Generally, the function will be true for all @data@ types and false -- for @newtype@s, unboxed tuples and type family 'TyCon's. But it is -- not guaranteed to return @True@ in all cases that it could. -- -- NB: for a data type family, only the /instance/ 'TyCon's -- get an info table. The family declaration 'TyCon' does not isDataTyCon (AlgTyCon {algTcRhs = rhs}) = case rhs of DataTyCon {} -> True NewTyCon {} -> False DataFamilyTyCon {} -> False AbstractTyCon {} -> False -- We don't know, so return False isDataTyCon (TupleTyCon {tyConTupleSort = sort}) = isBoxed (tupleSortBoxity sort) isDataTyCon _ = False -- | 'isDistinctTyCon' is true of 'TyCon's that are equal only to -- themselves, even via coercions (except for unsafeCoerce). -- This excludes newtypes, type functions, type synonyms. -- It relates directly to the FC consistency story: -- If the axioms are consistent, -- and co : S tys ~ T tys, and S,T are "distinct" TyCons, -- then S=T. -- Cf Note [Pruning dead case alternatives] in Unify isDistinctTyCon :: TyCon -> Bool isDistinctTyCon (AlgTyCon {algTcRhs = rhs}) = isDistinctAlgRhs rhs isDistinctTyCon (FunTyCon {}) = True isDistinctTyCon (TupleTyCon {}) = True isDistinctTyCon (PrimTyCon {}) = True isDistinctTyCon (PromotedDataCon {}) = True isDistinctTyCon _ = False isDistinctAlgRhs :: AlgTyConRhs -> Bool isDistinctAlgRhs (DataTyCon {}) = True isDistinctAlgRhs (DataFamilyTyCon {}) = True isDistinctAlgRhs (AbstractTyCon distinct) = distinct isDistinctAlgRhs (NewTyCon {}) = False -- | Is this 'TyCon' that for a @newtype@ isNewTyCon :: TyCon -> Bool isNewTyCon (AlgTyCon {algTcRhs = NewTyCon {}}) = True isNewTyCon _ = 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, CoAxiom Unbranched) unwrapNewTyCon_maybe (AlgTyCon { tyConTyVars = tvs, algTcRhs = NewTyCon { nt_co = co, nt_rhs = rhs }}) = Just (tvs, rhs, co) unwrapNewTyCon_maybe _ = Nothing isProductTyCon :: TyCon -> Bool -- True of datatypes or newtypes that have -- one, vanilla, data constructor isProductTyCon tc@(AlgTyCon {}) = case algTcRhs tc of DataTyCon{ data_cons = [data_con] } -> isVanillaDataCon data_con NewTyCon {} -> True _ -> False isProductTyCon (TupleTyCon {}) = True isProductTyCon _ = False isDataProductTyCon_maybe :: TyCon -> Maybe DataCon -- True of datatypes (not newtypes) with -- one, vanilla, data constructor isDataProductTyCon_maybe (AlgTyCon { algTcRhs = DataTyCon { data_cons = cons } }) | [con] <- cons -- Singleton , isVanillaDataCon con -- Vanilla = Just con isDataProductTyCon_maybe (TupleTyCon { dataCon = con }) = Just con isDataProductTyCon_maybe _ = Nothing -- | Is this a 'TyCon' representing a type synonym (@type@)? isSynTyCon :: TyCon -> Bool isSynTyCon (SynTyCon {}) = True isSynTyCon _ = False -- As for newtypes, it is in some contexts important to distinguish between -- closed synonyms and synonym families, as synonym families have no unique -- right hand side to which a synonym family application can expand. -- isDecomposableTyCon :: TyCon -> Bool -- 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 _other = True -- | Is this an algebraic 'TyCon' declared with the GADT syntax? isGadtSyntaxTyCon :: TyCon -> Bool isGadtSyntaxTyCon (AlgTyCon { algTcGadtSyntax = res }) = res isGadtSyntaxTyCon _ = False -- | 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 defines a family? isFamilyTyCon :: TyCon -> Bool isFamilyTyCon (SynTyCon {synTcRhs = OpenSynFamilyTyCon }) = True isFamilyTyCon (SynTyCon {synTcRhs = ClosedSynFamilyTyCon {} }) = True isFamilyTyCon (SynTyCon {synTcRhs = AbstractClosedSynFamilyTyCon {} }) = True isFamilyTyCon (SynTyCon {synTcRhs = BuiltInSynFamTyCon {} }) = True isFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True isFamilyTyCon _ = False -- | Is this a 'TyCon', synonym or otherwise, that defines an family with -- instances? isOpenFamilyTyCon :: TyCon -> Bool isOpenFamilyTyCon (SynTyCon {synTcRhs = OpenSynFamilyTyCon }) = True isOpenFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon }) = True isOpenFamilyTyCon _ = False -- | Is this a synonym 'TyCon' that can have may have further instances appear? isSynFamilyTyCon :: TyCon -> Bool isSynFamilyTyCon (SynTyCon {synTcRhs = OpenSynFamilyTyCon {}}) = True isSynFamilyTyCon (SynTyCon {synTcRhs = ClosedSynFamilyTyCon {}}) = True isSynFamilyTyCon (SynTyCon {synTcRhs = AbstractClosedSynFamilyTyCon {}}) = True isSynFamilyTyCon (SynTyCon {synTcRhs = BuiltInSynFamTyCon {}}) = True isSynFamilyTyCon _ = False isOpenSynFamilyTyCon :: TyCon -> Bool isOpenSynFamilyTyCon (SynTyCon {synTcRhs = OpenSynFamilyTyCon }) = True isOpenSynFamilyTyCon _ = False -- leave out abstract closed families here isClosedSynFamilyTyCon_maybe :: TyCon -> Maybe (CoAxiom Branched) isClosedSynFamilyTyCon_maybe (SynTyCon {synTcRhs = ClosedSynFamilyTyCon ax}) = Just ax isClosedSynFamilyTyCon_maybe _ = Nothing isBuiltInSynFamTyCon_maybe :: TyCon -> Maybe BuiltInSynFamily isBuiltInSynFamTyCon_maybe SynTyCon {synTcRhs = BuiltInSynFamTyCon ops } = Just ops isBuiltInSynFamTyCon_maybe _ = Nothing -- | Is this a synonym 'TyCon' that can have may have further instances appear? isDataFamilyTyCon :: TyCon -> Bool isDataFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True isDataFamilyTyCon _ = False -- | Injective 'TyCon's can be decomposed, so that -- T ty1 ~ T ty2 => ty1 ~ ty2 isInjectiveTyCon :: TyCon -> Bool isInjectiveTyCon tc = not (isSynTyCon tc) -- 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 -- type synonym, because you should probably have expanded it first -- But regardless, it's not injective! -- | Are we able to extract informationa 'TyVar' to class argument list -- mappping from a given 'TyCon'? isTyConAssoc :: TyCon -> Bool isTyConAssoc tc = isJust (tyConAssoc_maybe tc) tyConAssoc_maybe :: TyCon -> Maybe Class tyConAssoc_maybe tc = case tyConParent tc of AssocFamilyTyCon cls -> Just cls _ -> Nothing -- The unit tycon didn't used to be classed as a tuple tycon -- but I thought that was silly so I've undone it -- If it can't be for some reason, it should be a AlgTyCon isTupleTyCon :: TyCon -> Bool -- ^ Does this 'TyCon' represent a tuple? -- -- NB: when compiling @Data.Tuple@, the tycons won't reply @True@ to -- 'isTupleTyCon', because they are built as 'AlgTyCons'. However they -- get spat into the interface file as tuple tycons, so I don't think -- it matters. isTupleTyCon (TupleTyCon {}) = True isTupleTyCon _ = False -- | Is this the 'TyCon' for an unboxed tuple? isUnboxedTupleTyCon :: TyCon -> Bool isUnboxedTupleTyCon (TupleTyCon {tyConTupleSort = sort}) = not (isBoxed (tupleSortBoxity sort)) isUnboxedTupleTyCon _ = False -- | Is this the 'TyCon' for a boxed tuple? isBoxedTupleTyCon :: TyCon -> Bool isBoxedTupleTyCon (TupleTyCon {tyConTupleSort = sort}) = isBoxed (tupleSortBoxity sort) isBoxedTupleTyCon _ = False -- | Extract the boxity of the given 'TyCon', if it is a 'TupleTyCon'. -- Panics otherwise tupleTyConBoxity :: TyCon -> Boxity tupleTyConBoxity tc = tupleSortBoxity (tyConTupleSort tc) -- | Extract the 'TupleSort' of the given 'TyCon', if it is a 'TupleTyCon'. -- Panics otherwise tupleTyConSort :: TyCon -> TupleSort tupleTyConSort tc = tyConTupleSort 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 isRecursiveTyCon _ = False promotableTyCon_maybe :: TyCon -> Maybe TyCon promotableTyCon_maybe (AlgTyCon { tcPromoted = prom }) = prom promotableTyCon_maybe (TupleTyCon { tcPromoted = prom }) = prom promotableTyCon_maybe _ = Nothing promoteTyCon :: TyCon -> TyCon promoteTyCon tc = case promotableTyCon_maybe tc of Just prom_tc -> prom_tc Nothing -> pprPanic "promoteTyCon" (ppr tc) -- | Is this the 'TyCon' of a foreign-imported type constructor? isForeignTyCon :: TyCon -> Bool isForeignTyCon (PrimTyCon {tyConExtName = Just _}) = True isForeignTyCon _ = False -- | Is this a PromotedTyCon? isPromotedTyCon :: TyCon -> Bool isPromotedTyCon (PromotedTyCon {}) = True isPromotedTyCon _ = False -- | Retrieves the promoted TyCon if this is a PromotedTyCon; isPromotedTyCon_maybe :: TyCon -> Maybe TyCon isPromotedTyCon_maybe (PromotedTyCon { ty_con = tc }) = Just tc isPromotedTyCon_maybe _ = Nothing -- | Is this a PromotedDataCon? isPromotedDataCon :: TyCon -> Bool isPromotedDataCon (PromotedDataCon {}) = True isPromotedDataCon _ = False -- | Retrieves the promoted DataCon if this is a PromotedDataCon; isPromotedDataCon_maybe :: TyCon -> Maybe DataCon isPromotedDataCon_maybe (PromotedDataCon { dataCon = dc }) = Just dc isPromotedDataCon_maybe _ = Nothing -- | Identifies implicit tycons that, in particular, do not go into interface -- files (because they are implicitly reconstructed when the interface is -- read). -- -- Note that: -- -- * Associated families are implicit, as they are re-constructed from -- the class declaration in which they reside, and -- -- * Family instances are /not/ implicit as they represent the instance body -- (similar to a @dfun@ does that for a class instance). isImplicitTyCon :: TyCon -> Bool isImplicitTyCon tycon | isTyConAssoc tycon = True | isSynTyCon tycon = False | isAlgTyCon tycon = isTupleTyCon tycon | otherwise = True -- 'otherwise' catches: FunTyCon, PrimTyCon, -- PromotedDataCon, PomotedTypeTyCon tyConCType_maybe :: TyCon -> Maybe CType tyConCType_maybe tc@(AlgTyCon {}) = tyConCType tc tyConCType_maybe _ = Nothing\end{code} ----------------------------------------------- -- Expand type-constructor applications ----------------------------------------------- \begin{code}

tcExpandTyCon_maybe, coreExpandTyCon_maybe :: TyCon -> [tyco] -- ^ Arguments to 'TyCon' -> Maybe ([(TyVar,tyco)], Type, [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' tcExpandTyCon_maybe (SynTyCon {tyConTyVars = tvs, synTcRhs = SynonymTyCon rhs }) tys = expand tvs rhs tys tcExpandTyCon_maybe _ _ = Nothing --------------- -- ^ 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 tycon tys = tcExpandTyCon_maybe tycon tys ---------------- 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 where n_tvs = length tvs\end{code} \begin{code}

tyConKind :: TyCon -> Kind tyConKind = tc_kind -- | As 'tyConDataCons_maybe', but returns the empty list of constructors if no constructors -- could be found tyConDataCons :: TyCon -> [DataCon] -- It's convenient for tyConDataCons to return the -- empty list for type synonyms etc tyConDataCons tycon = tyConDataCons_maybe tycon `orElse` [] -- | Determine the 'DataCon's originating from the given 'TyCon', if the 'TyCon' is the -- sort that can have any constructors (note: this does not include abstract algebraic types) tyConDataCons_maybe :: TyCon -> Maybe [DataCon] tyConDataCons_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = cons }}) = Just cons tyConDataCons_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = con }}) = Just [con] tyConDataCons_maybe (TupleTyCon {dataCon = con}) = Just [con] tyConDataCons_maybe _ = Nothing -- | Determine the number of value constructors a 'TyCon' has. Panics if the 'TyCon' -- is not algebraic or a tuple tyConFamilySize :: TyCon -> Int tyConFamilySize (AlgTyCon {algTcRhs = DataTyCon {data_cons = cons}}) = length cons 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 -- 'TyCon'. Panics for any other sort of 'TyCon' algTyConRhs :: TyCon -> AlgTyConRhs algTyConRhs (AlgTyCon {algTcRhs = rhs}) = rhs algTyConRhs (TupleTyCon {dataCon = con, tyConArity = arity}) = DataTyCon { data_cons = [con], is_enum = arity == 0 } algTyConRhs other = pprPanic "algTyConRhs" (ppr other) -- | Get the list of roles for the type parameters of a TyCon tyConRoles :: TyCon -> [Role] -- See also Note [TyCon Role signatures] tyConRoles tc = case tc of { FunTyCon {} -> const_role Representational ; AlgTyCon { tc_roles = roles } -> roles ; TupleTyCon {} -> const_role Representational ; SynTyCon { tc_roles = roles } -> roles ; PrimTyCon { tc_roles = roles } -> roles ; PromotedDataCon { tc_roles = roles } -> roles ; PromotedTyCon {} -> const_role Nominal } where const_role r = replicate (tyConArity tc) r\end{code} \begin{code}

-- | Extract the bound type variables and type expansion of a type synonym 'TyCon'. Panics if the -- 'TyCon' is not a synonym newTyConRhs :: TyCon -> ([TyVar], Type) newTyConRhs (AlgTyCon {tyConTyVars = tvs, algTcRhs = NewTyCon { nt_rhs = rhs }}) = (tvs, rhs) newTyConRhs tycon = pprPanic "newTyConRhs" (ppr tycon) -- | The number of type parameters that need to be passed to a newtype to resolve it. May be less than in the definition if it can be eta-contracted. newTyConEtadArity :: TyCon -> Int newTyConEtadArity (AlgTyCon {algTcRhs = NewTyCon { nt_etad_rhs = tvs_rhs }}) = length (fst tvs_rhs) newTyConEtadArity tycon = pprPanic "newTyConEtadArity" (ppr tycon) -- | Extract the bound type variables and type expansion of an eta-contracted type synonym 'TyCon'. -- Panics if the 'TyCon' is not a synonym newTyConEtadRhs :: TyCon -> ([TyVar], Type) newTyConEtadRhs (AlgTyCon {algTcRhs = NewTyCon { nt_etad_rhs = tvs_rhs }}) = tvs_rhs newTyConEtadRhs tycon = pprPanic "newTyConEtadRhs" (ppr tycon) -- | 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 (CoAxiom Unbranched) newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = Just co newTyConCo_maybe _ = Nothing newTyConCo :: TyCon -> CoAxiom Unbranched 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 tyConPrimRep (PrimTyCon {primTyConRep = rep}) = rep tyConPrimRep tc = ASSERT(not (isUnboxedTupleTyCon tc)) PtrRep\end{code} \begin{code}

-- | Find the \"stupid theta\" of the 'TyCon'. 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 ...@ tyConStupidTheta :: TyCon -> [PredType] tyConStupidTheta (AlgTyCon {algTcStupidTheta = stupid}) = stupid tyConStupidTheta (TupleTyCon {}) = [] tyConStupidTheta tycon = pprPanic "tyConStupidTheta" (ppr tycon)\end{code} \begin{code}

-- | Extract the 'TyVar's bound by a vanilla type synonym (not familiy) -- and the corresponding (unsubstituted) right hand side. synTyConDefn_maybe :: TyCon -> Maybe ([TyVar], Type) synTyConDefn_maybe (SynTyCon {tyConTyVars = tyvars, synTcRhs = SynonymTyCon ty}) = Just (tyvars, ty) synTyConDefn_maybe _ = Nothing -- | Extract the information pertaining to the right hand side of a type synonym (@type@) declaration. synTyConRhs_maybe :: TyCon -> Maybe SynTyConRhs synTyConRhs_maybe (SynTyCon {synTcRhs = rhs}) = Just rhs synTyConRhs_maybe _ = Nothing\end{code} \begin{code}

-- | If the given 'TyCon' has a /single/ data constructor, i.e. it is a @data@ type with one -- alternative, a tuple type or a @newtype@ then that constructor is returned. If the 'TyCon' -- has more than one constructor, or represents a primitive or function type constructor then -- @Nothing@ is returned. In any other case, the function panics tyConSingleDataCon_maybe :: TyCon -> Maybe DataCon tyConSingleDataCon_maybe (TupleTyCon {dataCon = c}) = Just c tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = [c] }}) = Just c tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = c }}) = Just c tyConSingleDataCon_maybe _ = Nothing tyConSingleAlgDataCon_maybe :: TyCon -> Maybe DataCon -- Returns (Just con) for single-constructor *algebraic* data types -- *not* newtypes tyConSingleAlgDataCon_maybe (TupleTyCon {dataCon = c}) = Just c tyConSingleAlgDataCon_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = [c] }}) = Just c tyConSingleAlgDataCon_maybe _ = Nothing\end{code} \begin{code}

-- | Is this 'TyCon' that for a class instance? isClassTyCon :: TyCon -> Bool isClassTyCon (AlgTyCon {algTcParent = ClassTyCon _}) = True isClassTyCon _ = False -- | If this 'TyCon' is that for a class instance, return the class it is for. -- Otherwise returns @Nothing@ tyConClass_maybe :: TyCon -> Maybe Class tyConClass_maybe (AlgTyCon {algTcParent = ClassTyCon clas}) = Just clas tyConClass_maybe _ = Nothing tyConTuple_maybe :: TyCon -> Maybe TupleSort tyConTuple_maybe (TupleTyCon {tyConTupleSort = sort}) = Just sort tyConTuple_maybe _ = Nothing ---------------------------------------------------------------------------- tyConParent :: TyCon -> TyConParent tyConParent (AlgTyCon {algTcParent = parent}) = parent tyConParent (SynTyCon {synTcParent = parent}) = parent tyConParent _ = NoParentTyCon ---------------------------------------------------------------------------- -- | Is this 'TyCon' that for a data family instance? isFamInstTyCon :: TyCon -> Bool isFamInstTyCon tc = case tyConParent tc of FamInstTyCon {} -> True _ -> False tyConFamInstSig_maybe :: TyCon -> Maybe (TyCon, [Type], CoAxiom Unbranched) tyConFamInstSig_maybe tc = case tyConParent tc of FamInstTyCon ax f ts -> Just (f, ts, ax) _ -> 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 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 (CoAxiom Unbranched) tyConFamilyCoercion_maybe tc = case tyConParent tc of FamInstTyCon co _ _ -> Just co _ -> Nothing\end{code} %************************************************************************ %* * \subsection[TyCon-instances]{Instance declarations for @TyCon@} %* * %************************************************************************ @TyCon@s are compared by comparing their @Unique@s. The strictness analyser needs @Ord@. It is a lexicographic order with the property @(a<=b) || (b<=a)@. \begin{code}

instance Eq TyCon where a == b = case (a `compare` b) of { EQ -> True; _ -> False } a /= b = case (a `compare` b) of { EQ -> False; _ -> True } instance Ord TyCon 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 TyCon where getUnique tc = tyConUnique tc instance Outputable TyCon where -- At the moment a promoted TyCon has the same Name as its -- corresponding TyCon, so we add the quote to distinguish it here ppr tc = pprPromotionQuote tc <> ppr (tyConName tc) pprPromotionQuote :: TyCon -> SDoc pprPromotionQuote (PromotedDataCon {}) = char '\'' -- Quote promoted DataCons in types pprPromotionQuote (PromotedTyCon {}) = ifPprDebug (char '\'') pprPromotionQuote _ = empty -- However, we don't quote TyCons in kinds -- e.g. type family T a :: Bool -> * -- cf Trac #5952. Except with -dppr-debug instance NamedThing TyCon where getName = tyConName instance Data.Data TyCon where -- don't traverse? toConstr _ = abstractConstr "TyCon" gunfold _ _ = error "gunfold" dataTypeOf _ = mkNoRepType "TyCon"\end{code} %************************************************************************ %* * Walking over recursive TyCons %* * %************************************************************************ Note [Expanding newtypes and products] ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ When expanding a type to expose a data-type constructor, we need to be careful about newtypes, lest we fall into an infinite loop. Here are the key examples: newtype Id x = MkId x newtype Fix f = MkFix (f (Fix f)) newtype T = MkT (T -> T) Type Expansion -------------------------- T T -> T Fix Maybe Maybe (Fix Maybe) Id (Id Int) Int Fix Id NO NO NO Notice that we can expand T, even though it's recursive. And we can expand Id (Id Int), even though the Id shows up twice at the outer level. So, when expanding, we keep track of when we've seen a recursive newtype at outermost level; and bale out if we see it again. We sometimes want to do the same for product types, so that the strictness analyser doesn't unbox infinitely deeply. The function that manages this is checkRecTc. \begin{code}

newtype RecTcChecker = RC NameSet initRecTc :: RecTcChecker initRecTc = RC emptyNameSet checkRecTc :: RecTcChecker -> TyCon -> Maybe RecTcChecker -- Nothing => Recursion detected -- Just rec_tcs => Keep going checkRecTc (RC rec_nts) tc | not (isRecursiveTyCon tc) = Just (RC rec_nts) | tc_name `elemNameSet` rec_nts = Nothing | otherwise = Just (RC (addOneToNameSet rec_nts tc_name)) where tc_name = tyConName tc\end{code}