%
+% (c) The University of Glasgow 2006
% (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
%
-\section[TyCon]{The @TyCon@ datatype}
+
+The @TyCon@ datatype
\begin{code}
module TyCon(
- TyCon, FieldLabel,
+ -- * Main TyCon data types
+ TyCon, FieldLabel,
- PrimRep(..),
- tyConPrimRep,
-
- AlgTyConRhs(..), visibleDataCons, AlgTyConParent(..),
+ AlgTyConRhs(..), visibleDataCons,
+ TyConParent(..), isNoParent,
SynTyConRhs(..),
- isFunTyCon, isUnLiftedTyCon, isProductTyCon,
- isAlgTyCon, isDataTyCon, isSynTyCon, isNewTyCon, isClosedNewTyCon,
- isPrimTyCon,
- isEnumerationTyCon, isGadtSyntaxTyCon, isOpenTyCon,
- assocTyConArgPoss_maybe, isTyConAssoc, setTyConArgPoss,
- isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon, tupleTyConBoxity,
- isRecursiveTyCon, newTyConRep, newTyConRhs, newTyConCo_maybe,
- isHiBootTyCon, isSuperKindTyCon,
- isCoercionTyCon_maybe, isCoercionTyCon,
-
- tcExpandTyCon_maybe, coreExpandTyCon_maybe,
-
- makeTyConAbstract, isAbstractTyCon,
-
- mkForeignTyCon, isForeignTyCon,
+ -- ** Coercion axiom constructors
+ CoAxiom(..), coAxiomName, coAxiomArity,
+ -- ** Constructing TyCons
mkAlgTyCon,
mkClassTyCon,
mkFunTyCon,
mkPrimTyCon,
- mkVoidPrimTyCon,
+ mkKindTyCon,
mkLiftedPrimTyCon,
mkTupleTyCon,
mkSynTyCon,
mkSuperKindTyCon,
- mkCoercionTyCon,
-
+ mkForeignTyCon,
+ mkAnyTyCon,
+
+ -- ** Predicates on TyCons
+ isAlgTyCon,
+ isClassTyCon, isFamInstTyCon,
+ isFunTyCon,
+ isPrimTyCon,
+ isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon,
+ isSynTyCon, isClosedSynTyCon,
+ isSuperKindTyCon, isDecomposableTyCon,
+ isForeignTyCon, isAnyTyCon, tyConHasKind,
+
+ isInjectiveTyCon,
+ isDataTyCon, isProductTyCon, isEnumerationTyCon,
+ isNewTyCon, isAbstractTyCon,
+ isFamilyTyCon, isSynFamilyTyCon, isDataFamilyTyCon,
+ isUnLiftedTyCon,
+ isGadtSyntaxTyCon,
+ isTyConAssoc,
+ isRecursiveTyCon,
+ isHiBootTyCon,
+ isImplicitTyCon,
+
+ -- ** Extracting information out of TyCons
tyConName,
tyConKind,
tyConUnique,
tyConTyVars,
- algTyConRhs, tyConDataCons, tyConDataCons_maybe, tyConFamilySize,
- tyConSelIds,
+ tyConDataCons, tyConDataCons_maybe, tyConSingleDataCon_maybe,
+ tyConFamilySize,
tyConStupidTheta,
tyConArity,
- isClassTyCon, tyConClass_maybe,
- isFamInstTyCon, tyConFamInst_maybe, tyConFamilyCoercion_maybe,
- synTyConDefn, synTyConRhs, synTyConType, synTyConResKind,
- tyConExtName, -- External name for foreign types
-
- maybeTyConSingleCon,
+ tyConParent,
+ tyConClass_maybe,
+ tyConFamInst_maybe, tyConFamilyCoercion_maybe,tyConFamInstSig_maybe,
+ synTyConDefn, synTyConRhs, synTyConType,
+ tyConExtName, -- External name for foreign types
+ algTyConRhs,
+ newTyConRhs, newTyConEtadRhs, unwrapNewTyCon_maybe,
+ tupleTyConBoxity, tupleTyConArity,
+
+ -- ** Manipulating TyCons
+ tcExpandTyCon_maybe, coreExpandTyCon_maybe,
+ makeTyConAbstract,
+ newTyConCo, newTyConCo_maybe,
- -- Generics
- tyConHasGenerics
+ -- * Primitive representations of Types
+ PrimRep(..),
+ tyConPrimRep,
+ primRepSizeW
) where
#include "HsVersions.h"
-import {-# SOURCE #-} TypeRep ( Kind, Type, Coercion, PredType )
+import {-# SOURCE #-} TypeRep ( Kind, Type, PredType )
import {-# SOURCE #-} DataCon ( DataCon, isVanillaDataCon )
-import Var ( TyVar, Id )
-import Class ( Class )
-import BasicTypes ( Arity, RecFlag(..), Boxity(..), isBoxed )
-import Name ( Name, nameUnique, NamedThing(getName) )
-import PrelNames ( Unique, Uniquable(..) )
-import Maybe ( isJust )
-import Maybes ( orElse )
+import Var
+import Class
+import BasicTypes
+import Name
+import PrelNames
+import Maybes
import Outputable
import FastString
+import Constants
+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}
%************************************************************************
\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.
data TyCon
- = FunTyCon {
+ = -- | The function type constructor, @(->)@
+ FunTyCon {
tyConUnique :: Unique,
tyConName :: Name,
- tyConKind :: Kind,
+ tc_kind :: Kind,
tyConArity :: Arity
}
-
- | AlgTyCon { -- Data type, and newtype decls.
- -- All lifted, all boxed
+ -- | 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,
- tyConKind :: Kind,
+ tc_kind :: Kind,
tyConArity :: Arity,
- tyConTyVars :: [TyVar], -- Scopes over (a) the algTcStupidTheta
- -- (b) the cached types in
- -- algTyConRhs.NewTyCon
- -- (c) the family instance
- -- types if present
- -- But not over the data constructors
-
- tyConArgPoss :: Maybe [Int], -- for associated families: for each
- -- tyvar in the AT decl, gives the
- -- position of that tyvar in the class
- -- argument list (starting from 0).
- -- NB: Length is less than tyConArity
- -- if higher kind signature.
+ 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
- algTcSelIds :: [Id], -- Its record selectors (empty if none)
-
- algTcGadtSyntax :: Bool, -- True <=> the data type was declared using GADT syntax
- -- That doesn't mean it's a true GADT; only that the "where"
- -- form was used. This field is used only to guide
- -- pretty-printinng
- algTcStupidTheta :: [PredType], -- The "stupid theta" for the data type
- -- (always empty for GADTs)
-
- algTcRhs :: AlgTyConRhs, -- Data constructors in here
-
- algTcRec :: RecFlag, -- Tells whether the data type is part
- -- of a mutually-recursive group or not
-
- hasGenerics :: Bool, -- True <=> generic to/from functions are available
- -- (in the exports of the data type's source module)
-
- algTcParent :: AlgTyConParent -- Gives the class or family tycon for
- -- derived tycons representing classes
- -- or family instances, respectively.
+ 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.
| TupleTyCon {
tyConUnique :: Unique,
tyConName :: Name,
- tyConKind :: Kind,
+ tc_kind :: Kind,
tyConArity :: Arity,
tyConBoxed :: Boxity,
tyConTyVars :: [TyVar],
- dataCon :: DataCon,
- hasGenerics :: Bool
+ dataCon :: DataCon -- ^ Corresponding tuple data constructor
}
+ -- | Represents type synonyms
| SynTyCon {
tyConUnique :: Unique,
tyConName :: Name,
- tyConKind :: Kind,
+ tc_kind :: Kind,
tyConArity :: Arity,
tyConTyVars :: [TyVar], -- Bound tyvars
- tyConArgPoss :: Maybe [Int], -- for associated families: for each
- -- tyvar in the AT decl, gives the
- -- position of that tyvar in the class
- -- argument list (starting from 0).
- -- NB: Length is less than tyConArity
- -- if higher kind signature.
-
- synTcRhs :: SynTyConRhs -- Expanded type in here
+ synTcRhs :: SynTyConRhs, -- ^ Contains information about the
+ -- expansion of the synonym
+
+ synTcParent :: TyConParent -- ^ Gives the family declaration 'TyCon'
+ -- of 'TyCon's representing family instances
+
}
- | PrimTyCon { -- Primitive types; cannot be defined in Haskell
- -- Now includes foreign-imported types
- -- Also includes 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,
- tyConKind :: Kind,
- tyConArity :: Arity,
+ tc_kind :: Kind,
+ 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). The CgRep tells.
+ 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,
- -- but foreign-imported ones may not be
- tyConExtName :: Maybe FastString -- Just xx for foreign-imported types
+ 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
}
- | CoercionTyCon { -- E.g. (:=:), sym, trans, left, right
- -- INVARIANT: coercions are always fully applied
- tyConUnique :: Unique,
- tyConName :: Name,
- tyConArity :: Arity,
- coKindFun :: [Type] -> Kind
+ -- | Any types. Like tuples, this is a potentially-infinite family of TyCons
+ -- one for each distinct Kind. They have no values at all.
+ -- Because there are infinitely many of them (like tuples) they are
+ -- defined in GHC.Prim and have names like "Any(*->*)".
+ -- Their Unique is derived from the OccName.
+ -- See Note [Any types] in TysPrim
+ | AnyTyCon {
+ tyConUnique :: Unique,
+ tyConName :: Name,
+ tc_kind :: Kind -- Never = *; that is done via PrimTyCon
+ -- See Note [Any types] in TysPrim
}
-
- | SuperKindTyCon { -- Super Kinds, TY (box) and CO (diamond).
- -- They have no kind; and arity zero
+
+ -- | 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 {
tyConUnique :: Unique,
tyConName :: Name
}
-type KindCon = TyCon
-
-type SuperKindCon = TyCon
-
+-- | Names of the fields in an algebraic record type
type FieldLabel = Name
+-- | Represents right-hand-sides of 'TyCon's for algebraic types
data AlgTyConRhs
- = AbstractTyCon -- 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
-
- | OpenDataTyCon -- data family (further instances can appear
- | OpenNewTyCon -- newtype family at any time)
+ -- | 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 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 constructors; can be empty if the user declares
- -- the type to have no constructors
- -- INVARIANT: Kept in order of increasing tag
- -- (see the tag assignment in DataCon.mkDataCon)
- is_enum :: Bool -- Cached: True <=> an enumeration type
- } -- Includes data types with no constructors.
+ -- ^ 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; it has no existentials
-
- nt_rhs :: Type, -- Cached: the argument type of the constructor
- -- = the representation type of the tycon
- -- The free tyvars of this type are the tyConTyVars
-
- nt_co :: Maybe TyCon, -- The coercion used to create the newtype
- -- from the representation
- -- optional for non-recursive newtypes
- -- See Note [Newtype coercions]
-
- nt_etad_rhs :: ([TyVar], Type) ,
- -- The same again, but this time eta-reduced
- -- hence the [TyVar] which may be shorter than the declared
- -- arity of the TyCon. See Note [Newtype eta]
-
- nt_rep :: Type -- Cached: the *ultimate* representation type
- -- By 'ultimate' I mean that the top-level constructor
- -- of the rep type is not itself a newtype or type synonym.
- -- The rep type isn't entirely simple:
- -- for a recursive newtype we pick () as the rep type
- -- newtype T = MkT T
- --
- -- This one does not need to be eta reduced; hence its
- -- free type variables are conveniently tyConTyVars
- -- Thus:
- -- newtype T a = MkT [(a,Int)]
- -- The rep type is [(a,Int)]
- -- NB: the rep type isn't necessarily the original RHS of the
- -- newtype decl, because the rep type looks through other
- } -- newtypes.
+ 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 -- 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.
+ }
+-- | 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 OpenDataTyCon = []
-visibleDataCons OpenNewTyCon = []
+visibleDataCons DataFamilyTyCon {} = []
visibleDataCons (DataTyCon{ data_cons = cs }) = cs
visibleDataCons (NewTyCon{ data_con = c }) = [c]
--- Both type classes as well as data/newtype family instances imply implicit
+-- ^ 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.
---
-data AlgTyConParent = -- An ordinary type constructor has no parent.
- NoParentTyCon
-
- -- Type constructors representing a class dictionary.
- | ClassTyCon Class
-
- -- Type constructors representing an instances of a type
- -- family.
- | FamilyTyCon TyCon -- the type family
- [Type] -- instance types
- TyCon -- a *coercion* identifying
- -- the representation type
- -- with the type instance
-
+-- 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.
+ | 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
+ --
+ -- 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]
+ -- 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 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 (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 Kind -- Type family: *result* kind given
- | SynonymTyCon Type -- Mentioning head type vars. Acts as a template for
- -- the expansion when the tycon is applied to some
- -- types.
+ = -- | 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 [Newtype coercions]
+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)
which is used for coercing from the representation type of the
newtype, to the newtype itself. For example,
newtype T a = MkT (a -> a)
-the NewTyCon for T will contain nt_co = CoT where CoT t : T t :=: t ->
-t. This TyCon is a CoercionTyCon, so it does not have a kind on its
+the NewTyCon for T will contain nt_co = CoT where CoT t : T t ~ t ->
+t. This TyCon is a CoTyCon, so it does not have a kind on its
own; it basically has its own typing rule for the fully-applied
version. If the newtype T has k type variables then CoT has arity at
most k. In the case that the right hand side is a type application
newtype S a = MkT [a]
-then we would generate the arity 0 coercion CoS : S :=: []. The
+then we would generate the arity 0 coercion CoS : S ~ []. The
primary reason we do this is to make newtype deriving cleaner.
In the paper we'd write
- axiom CoT : (forall t. T t) :=: (forall t. [t])
+ axiom CoT : (forall t. T t) ~ (forall t. [t])
and then when we used CoT at a particular type, s, we'd say
CoT @ s
which encodes as (TyConApp instCoercionTyCon [TyConApp CoT [], s])
-But in GHC we instead make CoT into a new piece of type syntax
+But in GHC we instead make CoT into a new piece of type syntax, CoTyCon,
(like instCoercionTyCon, symCoercionTyCon etc), which must always
be saturated, but which encodes as
TyConApp CoT [s]
In the vocabulary of the paper it's as if we had axiom declarations
like
- axiom CoT t : T t :=: [t]
+ axiom CoT t : T t ~ [t]
Note [Newtype eta]
~~~~~~~~~~~~~~~~~~
w2 :: Foo T
w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
-After desugaring, and discading the data constructors for the newtypes,
+After desugaring, and discarding the data constructors for the newtypes,
we get:
w2 :: Foo T
w2 = w1
And now Lint complains unless Foo T == Foo [], and that requires T==[]
+This point carries over to the newtype coercion, because we need to
+say
+ w2 = w1 `cast` Foo CoT
+
+so the coercion tycon CoT must have
+ kind: T ~ []
+ and arity: 0
+
%************************************************************************
%* *
-\subsection{PrimRep}
+ Coercion axioms
%* *
%************************************************************************
-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.
+\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
+ }
+
+coAxiomArity :: CoAxiom -> Arity
+coAxiomArity ax = length (co_ax_tvs ax)
+
+coAxiomName :: CoAxiom -> Name
+coAxiomName = co_ax_name
+\end{code}
+
+
+%************************************************************************
+%* *
+\subsection{PrimRep}
+%* *
+%************************************************************************
A PrimRep is somewhat similar to a CgRep (see codeGen/SMRep) and a
-MachRep (see cmm/MachOp), although each of these types has a distinct
+MachRep (see cmm/CmmExpr), although each of these types has a distinct
and clearly defined purpose:
- A PrimRep is a CgRep + information about signedness + information
reps that don't have corresponding Haskell types).
\begin{code}
+-- | 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
- | WordRep -- unsinged, word-sized
- | Int64Rep -- signed, 64 bit (32-bit words only)
- | Word64Rep -- unsigned, 64 bit (32-bit words only)
- | AddrRep -- a pointer, but not to a Haskell value
+ | 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
+ deriving( Eq, Show )
+
+instance Outputable PrimRep where
+ ppr r = text (show r)
+
+-- | Find the size of a 'PrimRep', in words
+primRepSizeW :: PrimRep -> Int
+primRepSizeW IntRep = 1
+primRepSizeW WordRep = 1
+primRepSizeW Int64Rep = wORD64_SIZE `quot` wORD_SIZE
+primRepSizeW Word64Rep= wORD64_SIZE `quot` wORD_SIZE
+primRepSizeW FloatRep = 1 -- NB. might not take a full word
+primRepSizeW DoubleRep= dOUBLE_SIZE `quot` wORD_SIZE
+primRepSizeW AddrRep = 1
+primRepSizeW PtrRep = 1
+primRepSizeW VoidRep = 0
\end{code}
%************************************************************************
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,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = 2
}
--- This is the making of a TyCon. Just the same as the old mkAlgTyCon,
--- but now you also have to pass in the generic information about the type
--- constructor - you can get hold of it easily (see Generics module)
-mkAlgTyCon name kind tyvars stupid rhs sel_ids parent is_rec gen_info gadt_syn
+-- | 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
+ -> [PredType] -- ^ Stupid theta: see 'algTcStupidTheta'
+ -> AlgTyConRhs -- ^ Information about dat aconstructors
+ -> TyConParent
+ -> RecFlag -- ^ Is the 'TyCon' recursive?
+ -> Bool -- ^ Was the 'TyCon' declared with GADT syntax?
+ -> TyCon
+mkAlgTyCon name kind tyvars stupid rhs parent is_rec gadt_syn
= AlgTyCon {
tyConName = name,
tyConUnique = nameUnique name,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = length tyvars,
tyConTyVars = tyvars,
- tyConArgPoss = Nothing,
algTcStupidTheta = stupid,
algTcRhs = rhs,
- algTcSelIds = sel_ids,
- algTcParent = parent,
+ algTcParent = ASSERT( okParent name parent ) parent,
algTcRec = is_rec,
- algTcGadtSyntax = gadt_syn,
- hasGenerics = gen_info
+ algTcGadtSyntax = gadt_syn
}
+-- | Simpler specialization of 'mkAlgTyCon' for classes
+mkClassTyCon :: Name -> Kind -> [TyVar] -> AlgTyConRhs -> Class -> RecFlag -> TyCon
mkClassTyCon name kind tyvars rhs clas is_rec =
- mkAlgTyCon name kind tyvars [] rhs [] (ClassTyCon clas) is_rec False False
-
-mkTupleTyCon name kind arity tyvars con boxed gen_info
+ mkAlgTyCon name kind tyvars [] rhs (ClassTyCon clas) is_rec False
+
+mkTupleTyCon :: Name
+ -> Kind -- ^ Kind of the resulting 'TyCon'
+ -> Arity -- ^ Arity of the tuple
+ -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'
+ -> DataCon
+ -> Boxity -- ^ Whether the tuple is boxed or unboxed
+ -> TyCon
+mkTupleTyCon name kind arity tyvars con boxed
= TupleTyCon {
tyConUnique = nameUnique name,
tyConName = name,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = arity,
tyConBoxed = boxed,
tyConTyVars = tyvars,
- dataCon = con,
- hasGenerics = gen_info
+ dataCon = con
}
--- 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>
+-- ^ 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
+ -> Arity
+ -> TyCon
mkForeignTyCon name ext_name kind arity
= PrimTyCon {
tyConName = name,
tyConUnique = nameUnique name,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = arity,
primTyConRep = PtrRep, -- they all do
isUnLifted = False,
}
--- most Prim tycons are lifted
+-- | Create an unlifted primitive 'TyCon', such as @Int#@
+mkPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
mkPrimTyCon name kind arity rep
= mkPrimTyCon' name kind arity rep True
-mkVoidPrimTyCon name kind arity
- = mkPrimTyCon' name kind arity VoidRep True
+-- | Kind constructors
+mkKindTyCon :: Name -> Kind -> TyCon
+mkKindTyCon name kind
+ = mkPrimTyCon' name kind 0 VoidRep True
--- but RealWorld is lifted
+-- | Create a lifted primitive 'TyCon' such as @RealWorld@
+mkLiftedPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
mkLiftedPrimTyCon name kind arity rep
= mkPrimTyCon' name kind arity rep False
+mkPrimTyCon' :: Name -> Kind -> Arity -> PrimRep -> Bool -> TyCon
mkPrimTyCon' name kind arity rep is_unlifted
= PrimTyCon {
tyConName = name,
tyConUnique = nameUnique name,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = arity,
primTyConRep = rep,
isUnLifted = is_unlifted,
tyConExtName = Nothing
}
-mkSynTyCon name kind tyvars rhs
+-- | Create a type synonym 'TyCon'
+mkSynTyCon :: Name -> Kind -> [TyVar] -> SynTyConRhs -> TyConParent -> TyCon
+mkSynTyCon name kind tyvars rhs parent
= SynTyCon {
tyConName = name,
tyConUnique = nameUnique name,
- tyConKind = kind,
+ tc_kind = kind,
tyConArity = length tyvars,
tyConTyVars = tyvars,
- tyConArgPoss = Nothing,
- synTcRhs = rhs
+ synTcRhs = rhs,
+ synTcParent = parent
}
-mkCoercionTyCon name arity kindRule
- = CoercionTyCon {
- tyConName = name,
- tyConUnique = nameUnique name,
- tyConArity = arity,
- coKindFun = kindRule
- }
+mkAnyTyCon :: Name -> Kind -> TyCon
+mkAnyTyCon name kind
+ = AnyTyCon { tyConName = name,
+ tc_kind = kind,
+ tyConUnique = nameUnique name }
--- Super kinds always have arity zero
+-- | Create a super-kind 'TyCon'
+mkSuperKindTyCon :: Name -> TyCon -- Super kinds always have arity zero
mkSuperKindTyCon name
= SuperKindTyCon {
tyConName = name,
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 {}) = tc { algTcRhs = AbstractTyCon }
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 {tyConBoxed = boxity}) = not (isBoxed boxity)
isUnLiftedTyCon _ = False
--- isAlgTyCon returns True for both @data@ and @newtype@
+-- | Returns @True@ if the supplied 'TyCon' resulted from either a
+-- @data@ or @newtype@ declaration
isAlgTyCon :: TyCon -> Bool
isAlgTyCon (AlgTyCon {}) = True
isAlgTyCon (TupleTyCon {}) = True
-isAlgTyCon other = False
+isAlgTyCon _ = False
isDataTyCon :: TyCon -> Bool
--- isDataTyCon returns True for data types that are represented by
--- heap-allocated constructors.
--- These are srcutinised by Core-level @case@ expressions, and they
--- get info tables allocated for them.
--- True for all @data@ types
--- False for newtypes
--- unboxed tuples
-isDataTyCon tc@(AlgTyCon {algTcRhs = rhs})
+-- ^ 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 guarenteed 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
- OpenDataTyCon -> True
+ DataFamilyTyCon {} -> False
DataTyCon {} -> True
- OpenNewTyCon -> False
NewTyCon {} -> False
- AbstractTyCon -> pprPanic "isDataTyCon" (ppr tc)
+ AbstractTyCon -> False -- We don't know, so return False
isDataTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
-isDataTyCon other = False
+isDataTyCon _ = False
+-- | Is this 'TyCon' that for a @newtype@
isNewTyCon :: TyCon -> Bool
-isNewTyCon (AlgTyCon {algTcRhs = rhs}) = case rhs of
- OpenNewTyCon -> True
- NewTyCon {} -> True
- _ -> False
-isNewTyCon other = False
-
--- This is an important refinement as typical newtype optimisations do *not*
--- hold for newtype families. Why? Given a type `T a', if T is a newtype
--- family, there is no unique right hand side by which `T a' can be replaced
--- by a cast.
---
-isClosedNewTyCon :: TyCon -> Bool
-isClosedNewTyCon tycon = isNewTyCon tycon && not (isOpenTyCon tycon)
+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)
+unwrapNewTyCon_maybe (AlgTyCon { tyConTyVars = tvs,
+ algTcRhs = NewTyCon { nt_co = co,
+ nt_rhs = rhs }})
+ = Just (tvs, rhs, co)
+unwrapNewTyCon_maybe _ = Nothing
isProductTyCon :: TyCon -> Bool
--- A "product" tycon
--- has *one* constructor,
--- is *not* existential
--- but
--- may be DataType, NewType
--- may be unboxed or not,
--- may be recursive or not
+-- | A /product/ 'TyCon' must both:
+--
+-- 1. Have /one/ constructor
+--
+-- 2. /Not/ be existential
--
+-- However other than this there are few restrictions: they may be @data@ or @newtype@
+-- 'TyCon's of any boxity and may even be recursive.
isProductTyCon tc@(AlgTyCon {}) = case algTcRhs tc of
DataTyCon{ data_cons = [data_con] }
-> isVanillaDataCon data_con
NewTyCon {} -> True
- other -> False
+ _ -> False
isProductTyCon (TupleTyCon {}) = True
-isProductTyCon other = False
+isProductTyCon _ = False
+-- | 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 other = False
+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 other = False
-
-isOpenTyCon :: TyCon -> Bool
-isOpenTyCon (SynTyCon {synTcRhs = OpenSynTyCon _}) = True
-isOpenTyCon (AlgTyCon {algTcRhs = OpenDataTyCon }) = True
-isOpenTyCon (AlgTyCon {algTcRhs = OpenNewTyCon }) = True
-isOpenTyCon _ = False
-
-assocTyConArgPoss_maybe :: TyCon -> Maybe [Int]
-assocTyConArgPoss_maybe (AlgTyCon { tyConArgPoss = poss }) = poss
-assocTyConArgPoss_maybe (SynTyCon { tyConArgPoss = poss }) = poss
-assocTyConArgPoss_maybe _ = Nothing
-
+isEnumerationTyCon (TupleTyCon {tyConArity = arity}) = arity == 0
+isEnumerationTyCon _ = False
+
+-- | Is this a 'TyCon', synonym or otherwise, that may have further instances appear?
+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
+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 = isJust . assocTyConArgPoss_maybe
+isTyConAssoc tc = case tyConParent tc of
+ AssocFamilyTyCon {} -> True
+ _ -> False
-setTyConArgPoss :: TyCon -> [Int] -> TyCon
-setTyConArgPoss tc@(AlgTyCon {}) poss = tc { tyConArgPoss = Just poss }
-setTyConArgPoss tc@(SynTyCon {}) poss = tc { tyConArgPoss = Just poss }
-setTyConArgPoss tc _ = pprPanic "setTyConArgPoss" (ppr tc)
-
-isTupleTyCon :: TyCon -> Bool
-- 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, becuase they are built as AlgTyCons. However they
+-- NB: when compiling @Data.Tuple@, the tycons won't reply @True@ to
+-- 'isTupleTyCon', becuase 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 other = False
+isTupleTyCon _ = False
+-- | Is this the 'TyCon' for an unboxed tuple?
isUnboxedTupleTyCon :: TyCon -> Bool
isUnboxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
-isUnboxedTupleTyCon other = False
+isUnboxedTupleTyCon _ = False
+-- | Is this the 'TyCon' for a boxed tuple?
isBoxedTupleTyCon :: TyCon -> Bool
isBoxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
-isBoxedTupleTyCon other = False
+isBoxedTupleTyCon _ = False
+-- | Extract the boxity of the given 'TyCon', if it is a 'TupleTyCon'.
+-- Panics otherwise
+tupleTyConBoxity :: TyCon -> Boxity
tupleTyConBoxity tc = tyConBoxed tc
+-- | Extract the arity of the given 'TyCon', if it is a 'TupleTyCon'.
+-- Panics otherwise
+tupleTyConArity :: TyCon -> Arity
+tupleTyConArity tc = tyConArity tc
+
+-- | Is this a recursive 'TyCon'?
isRecursiveTyCon :: TyCon -> Bool
isRecursiveTyCon (AlgTyCon {algTcRec = Recursive}) = True
-isRecursiveTyCon other = False
+isRecursiveTyCon _ = False
+-- | Did this 'TyCon' originate from type-checking a .h*-boot file?
isHiBootTyCon :: TyCon -> Bool
-- Used for knot-tying in hi-boot files
isHiBootTyCon (AlgTyCon {algTcRhs = AbstractTyCon}) = True
-isHiBootTyCon other = False
+isHiBootTyCon _ = False
+-- | Is this the 'TyCon' of a foreign-imported type constructor?
isForeignTyCon :: TyCon -> Bool
--- isForeignTyCon identifies foreign-imported type constructors
isForeignTyCon (PrimTyCon {tyConExtName = Just _}) = True
-isForeignTyCon other = False
+isForeignTyCon _ = False
+-- | Is this a super-kind 'TyCon'?
isSuperKindTyCon :: TyCon -> Bool
isSuperKindTyCon (SuperKindTyCon {}) = True
-isSuperKindTyCon other = False
+isSuperKindTyCon _ = False
-isCoercionTyCon_maybe :: TyCon -> Maybe (Arity, [Type] -> Kind)
-isCoercionTyCon_maybe (CoercionTyCon {tyConArity = ar, coKindFun = rule})
- = Just (ar, rule)
-isCoercionTyCon_maybe other = Nothing
+-- | Is this an AnyTyCon?
+isAnyTyCon :: TyCon -> Bool
+isAnyTyCon (AnyTyCon {}) = True
+isAnyTyCon _ = False
-isCoercionTyCon (CoercionTyCon {}) = True
-isCoercionTyCon other = False
+-- | 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 = isClassTyCon tycon ||
+ isTupleTyCon tycon
+isImplicitTyCon _other = True
+ -- catches: FunTyCon, PrimTyCon,
+ -- CoTyCon, SuperKindTyCon
\end{code}
\begin{code}
tcExpandTyCon_maybe, coreExpandTyCon_maybe
:: TyCon
- -> [Type] -- Args to tycon
- -> Maybe ([(TyVar,Type)], -- Substitution
- Type, -- Body type (not yet substituted)
- [Type]) -- Leftover args
-
--- For the *typechecker* view, we expand synonyms only
+ -> [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 other_tycon tys = Nothing
+tcExpandTyCon_maybe _ _ = Nothing
---------------
--- For the *Core* view, we expand synonyms only as well
-
-coreExpandTyCon_maybe (AlgTyCon {algTcRec = NonRecursive, -- Not recursive
- 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
+-- ^ 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
- -> [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}
\begin{code}
-tyConHasGenerics :: TyCon -> Bool
-tyConHasGenerics (AlgTyCon {hasGenerics = hg}) = hg
-tyConHasGenerics (TupleTyCon {hasGenerics = hg}) = hg
-tyConHasGenerics other = False -- Synonyms
+tyConKind :: TyCon -> Kind
+tyConKind (FunTyCon { tc_kind = k }) = k
+tyConKind (AlgTyCon { tc_kind = k }) = k
+tyConKind (TupleTyCon { tc_kind = k }) = k
+tyConKind (SynTyCon { tc_kind = k }) = k
+tyConKind (PrimTyCon { tc_kind = k }) = k
+tyConKind (AnyTyCon { tc_kind = k }) = k
+tyConKind tc = pprPanic "tyConKind" (ppr tc) -- SuperKindTyCon and CoTyCon
+
+tyConHasKind :: TyCon -> Bool
+tyConHasKind (SuperKindTyCon {}) = False
+tyConHasKind _ = True
+
+-- | 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 other = Nothing
+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 = OpenDataTyCon}) = 0
-tyConFamilySize (TupleTyCon {}) = 1
-#ifdef DEBUG
+tyConFamilySize (AlgTyCon {algTcRhs = NewTyCon {}}) = 1
+tyConFamilySize (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = 0
+tyConFamilySize (TupleTyCon {}) = 1
tyConFamilySize other = pprPanic "tyConFamilySize:" (ppr other)
-#endif
-
-tyConSelIds :: TyCon -> [Id]
-tyConSelIds (AlgTyCon {algTcSelIds = fs}) = fs
-tyConSelIds other_tycon = []
+-- | 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}) = DataTyCon { data_cons = [con], is_enum = False }
+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)
\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)
-newTyConRep :: TyCon -> ([TyVar], Type)
-newTyConRep (AlgTyCon {tyConTyVars = tvs, algTcRhs = NewTyCon { nt_rep = rep }}) = (tvs, rep)
-newTyConRep tycon = pprPanic "newTyConRep" (ppr tycon)
-
-newTyConCo_maybe :: TyCon -> Maybe TyCon
-newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = co
-newTyConCo_maybe _ = Nothing
-
+-- | 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
+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
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 {}) = []
\end{code}
\begin{code}
+-- | Extract the 'TyVar's bound by a type synonym and the corresponding (unsubstituted) right hand side.
+-- If the given 'TyCon' is not a type synonym, panics
synTyConDefn :: TyCon -> ([TyVar], Type)
synTyConDefn (SynTyCon {tyConTyVars = tyvars, synTcRhs = SynonymTyCon ty})
= (tyvars, ty)
synTyConDefn tycon = pprPanic "getSynTyConDefn" (ppr tycon)
+-- | Extract the information pertaining to the right hand side of a type synonym (@type@) declaration. Panics
+-- if the given 'TyCon' is not a type synonym
synTyConRhs :: TyCon -> SynTyConRhs
synTyConRhs (SynTyCon {synTcRhs = rhs}) = rhs
synTyConRhs tc = pprPanic "synTyConRhs" (ppr tc)
+-- | Find the expansion of the type synonym represented by the given 'TyCon'. The free variables of this
+-- type will typically include those 'TyVar's bound by the 'TyCon'. Panics if the 'TyCon' is not that of
+-- a type synonym
synTyConType :: TyCon -> Type
synTyConType tc = case synTcRhs tc of
SynonymTyCon t -> t
_ -> pprPanic "synTyConType" (ppr tc)
-
-synTyConResKind :: TyCon -> Kind
-synTyConResKind (SynTyCon {synTcRhs = OpenSynTyCon kind}) = kind
-synTyConResKind tycon = pprPanic "synTyConResKind" (ppr tycon)
\end{code}
\begin{code}
-maybeTyConSingleCon :: TyCon -> Maybe DataCon
-maybeTyConSingleCon (AlgTyCon {algTcRhs = DataTyCon {data_cons = [c] }}) = Just c
-maybeTyConSingleCon (AlgTyCon {algTcRhs = NewTyCon { data_con = c }}) = Just c
-maybeTyConSingleCon (AlgTyCon {}) = Nothing
-maybeTyConSingleCon (TupleTyCon {dataCon = con}) = Just con
-maybeTyConSingleCon (PrimTyCon {}) = Nothing
-maybeTyConSingleCon (FunTyCon {}) = Nothing -- case at funty
-maybeTyConSingleCon tc = pprPanic "maybeTyConSingleCon: unexpected tycon " $ ppr tc
+-- | 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
\end{code}
\begin{code}
+-- | Is this 'TyCon' that for a class instance?
isClassTyCon :: TyCon -> Bool
isClassTyCon (AlgTyCon {algTcParent = ClassTyCon _}) = True
-isClassTyCon other_tycon = False
+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 ther_tycon = Nothing
+tyConClass_maybe _ = Nothing
-isFamInstTyCon :: TyCon -> Bool
-isFamInstTyCon (AlgTyCon {algTcParent = FamilyTyCon _ _ _ }) = True
-isFamInstTyCon other_tycon = False
+----------------------------------------------------------------------------
+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 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 ther_tycon =
- Nothing
-
-tyConFamilyCoercion_maybe :: TyCon -> Maybe TyCon
-tyConFamilyCoercion_maybe (AlgTyCon {algTcParent = FamilyTyCon _ _ coe}) =
- Just coe
-tyConFamilyCoercion_maybe ther_tycon =
- 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 CoAxiom
+tyConFamilyCoercion_maybe tc
+ = case tyConParent tc of
+ FamInstTyCon _ _ co -> Just co
+ _ -> Nothing
\end{code}
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