2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
10 -- * Main TyCon data types
13 AlgTyConRhs(..), visibleDataCons,
14 TyConParent(..), isNoParent,
18 -- ** Constructing TyCons
32 -- ** Predicates on TyCons
34 isClassTyCon, isFamInstTyCon,
37 isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon,
38 isSynTyCon, isClosedSynTyCon,
39 isSuperKindTyCon, isDecomposableTyCon,
40 isCoercionTyCon, isCoercionTyCon_maybe,
41 isForeignTyCon, isAnyTyCon, tyConHasKind,
44 isDataTyCon, isProductTyCon, isEnumerationTyCon,
45 isNewTyCon, isAbstractTyCon,
46 isFamilyTyCon, isSynFamilyTyCon, isDataFamilyTyCon,
52 isImplicitTyCon, tyConHasGenerics,
54 -- ** Extracting information out of TyCons
59 tyConDataCons, tyConDataCons_maybe, tyConSingleDataCon_maybe,
65 tyConFamInst_maybe, tyConFamilyCoercion_maybe,tyConFamInstSig_maybe,
66 synTyConDefn, synTyConRhs, synTyConType,
67 tyConExtName, -- External name for foreign types
69 newTyConRhs, newTyConEtadRhs, unwrapNewTyCon_maybe,
72 -- ** Manipulating TyCons
73 tcExpandTyCon_maybe, coreExpandTyCon_maybe,
77 -- * Primitive representations of Types
83 #include "HsVersions.h"
85 import {-# SOURCE #-} TypeRep ( Kind, Type, PredType )
86 import {-# SOURCE #-} DataCon ( DataCon, isVanillaDataCon )
98 import qualified Data.Data as Data
101 -----------------------------------------------
102 Notes about type families
103 -----------------------------------------------
105 Note [Type synonym families]
106 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~
107 * Type synonym families, also known as "type functions", map directly
108 onto the type functions in FC:
111 type instance F Int = Bool
114 * Reply "yes" to isSynFamilyTyCon, and isFamilyTyCon
116 * From the user's point of view (F Int) and Bool are simply
119 * A Haskell 98 type synonym is a degenerate form of a type synonym
122 * Type functions can't appear in the LHS of a type function:
123 type instance F (F Int) = ... -- BAD!
125 * Translation of type family decl:
128 a SynTyCon 'F', whose SynTyConRhs is SynFamilyTyCon
130 * Translation of type instance decl:
131 type instance F [a] = Maybe a
133 A SynTyCon 'R:FList a', whose
134 SynTyConRhs is (SynonymTyCon (Maybe a))
135 TyConParent is (FamInstTyCon F [a] co)
136 where co :: F [a] ~ R:FList a
137 Notice that we introduce a gratuitous vanilla type synonym
138 type R:FList a = Maybe a
139 solely so that type and data families can be treated more
140 uniformly, via a single FamInstTyCon descriptor
142 * In the future we might want to support
143 * closed type families (esp when we have proper kinds)
144 * injective type families (allow decomposition)
145 but we don't at the moment [2010]
147 Note [Data type families]
148 ~~~~~~~~~~~~~~~~~~~~~~~~~
149 See also Note [Wrappers for data instance tycons] in MkId.lhs
151 * Data type families are declared thus
153 data instance T Int = T1 | T2 Bool
155 Here T is the "family TyCon".
157 * Reply "yes" to isDataFamilyTyCon, and isFamilyTyCon
159 * The user does not see any "equivalent types" as he did with type
160 synonym families. He just sees constructors with types
164 * Here's the FC version of the above declarations:
167 data R:TInt = T1 | T2 Bool
168 axiom ax_ti : T Int ~ R:TInt
170 The R:TInt is the "representation TyCons".
171 It has an AlgTyConParent of
172 FamInstTyCon T [Int] ax_ti
174 * The data contructor T2 has a wrapper (which is what the
175 source-level "T2" invokes):
177 $WT2 :: Bool -> T Int
178 $WT2 b = T2 b `cast` sym ax_ti
180 * A data instance can declare a fully-fledged GADT:
182 data instance T (a,b) where
184 X2 :: a -> b -> T (a,b)
186 Here's the FC version of the above declaration:
189 X1 :: R:TPair Int Bool
190 X2 :: a -> b -> R:TPair a b
191 axiom ax_pr :: T (a,b) ~ R:TPair a b
193 $WX1 :: forall a b. a -> b -> T (a,b)
194 $WX1 a b (x::a) (y::b) = X2 a b x y `cast` sym (ax_pr a b)
196 The R:TPair are the "representation TyCons".
197 We have a bit of work to do, to unpick the result types of the
198 data instance declaration for T (a,b), to get the result type in the
199 representation; e.g. T (a,b) --> R:TPair a b
201 The representation TyCon R:TList, has an AlgTyConParent of
203 FamInstTyCon T [(a,b)] ax_pr
205 * Notice that T is NOT translated to a FC type function; it just
206 becomes a "data type" with no constructors, which can be coerced inot
207 into R:TInt, R:TPair by the axioms. These axioms
208 axioms come into play when (and *only* when) you
209 - use a data constructor
210 - do pattern matching
211 Rather like newtype, in fact
215 - T behaves just like a data type so far as decomposition is concerned
217 - (T Int) is not implicitly converted to R:TInt during type inference.
218 Indeed the latter type is unknown to the programmer.
220 - There *is* an instance for (T Int) in the type-family instance
221 environment, but it is only used for overlap checking
223 - It's fine to have T in the LHS of a type function:
224 type instance F (T a) = [a]
226 It was this last point that confused me! The big thing is that you
227 should not think of a data family T as a *type function* at all, not
228 even an injective one! We can't allow even injective type functions
229 on the LHS of a type function:
230 type family injective G a :: *
231 type instance F (G Int) = Bool
232 is no good, even if G is injective, because consider
233 type instance G Int = Bool
234 type instance F Bool = Char
236 So a data type family is not an injective type function. It's just a
237 data type with some axioms that connect it to other data types.
239 %************************************************************************
241 \subsection{The data type}
243 %************************************************************************
246 -- | TyCons represent type constructors. Type constructors are introduced by things such as:
248 -- 1) Data declarations: @data Foo = ...@ creates the @Foo@ type constructor of kind @*@
250 -- 2) Type synonyms: @type Foo = ...@ creates the @Foo@ type constructor
252 -- 3) Newtypes: @newtype Foo a = MkFoo ...@ creates the @Foo@ type constructor of kind @* -> *@
254 -- 4) Class declarations: @class Foo where@ creates the @Foo@ type constructor of kind @*@
256 -- 5) Type coercions! This is because we represent a coercion from @t1@ to @t2@
257 -- as a 'Type', where that type has kind @t1 ~ t2@. See "Coercion" for more on this
259 -- This data type also encodes a number of primitive, built in type constructors such as those
260 -- for function and tuple types.
262 = -- | The function type constructor, @(->)@
264 tyConUnique :: Unique,
270 -- | Algebraic type constructors, which are defined to be those
271 -- arising @data@ type and @newtype@ declarations. All these
272 -- constructors are lifted and boxed. See 'AlgTyConRhs' for more
275 tyConUnique :: Unique,
280 tyConTyVars :: [TyVar], -- ^ The type variables used in the type constructor.
281 -- Invariant: length tyvars = arity
282 -- Precisely, this list scopes over:
284 -- 1. The 'algTcStupidTheta'
285 -- 2. The cached types in 'algTyConRhs.NewTyCon'
286 -- 3. The family instance types if present
288 -- Note that it does /not/ scope over the data constructors.
290 algTcGadtSyntax :: Bool, -- ^ Was the data type declared with GADT syntax?
291 -- If so, that doesn't mean it's a true GADT;
292 -- only that the "where" form was used.
293 -- This field is used only to guide pretty-printing
295 algTcStupidTheta :: [PredType], -- ^ The \"stupid theta\" for the data type
296 -- (always empty for GADTs).
297 -- A \"stupid theta\" is the context to the left
298 -- of an algebraic type declaration,
299 -- e.g. @Eq a@ in the declaration
300 -- @data Eq a => T a ...@.
302 algTcRhs :: AlgTyConRhs, -- ^ Contains information about the
303 -- data constructors of the algebraic type
305 algTcRec :: RecFlag, -- ^ Tells us whether the data type is part
306 -- of a mutually-recursive group or not
308 hasGenerics :: Bool, -- ^ Whether generic (in the -XGenerics sense)
309 -- to\/from functions are available in the exports
310 -- of the data type's source module.
312 algTcParent :: TyConParent -- ^ Gives the class or family declaration 'TyCon'
313 -- for derived 'TyCon's representing class
314 -- or family instances, respectively.
315 -- See also 'synTcParent'
318 -- | Represents the infinite family of tuple type constructors,
319 -- @()@, @(a,b)@, @(# a, b #)@ etc.
321 tyConUnique :: Unique,
325 tyConBoxed :: Boxity,
326 tyConTyVars :: [TyVar],
327 dataCon :: DataCon, -- ^ Corresponding tuple data constructor
331 -- | Represents type synonyms
333 tyConUnique :: Unique,
338 tyConTyVars :: [TyVar], -- Bound tyvars
340 synTcRhs :: SynTyConRhs, -- ^ Contains information about the
341 -- expansion of the synonym
343 synTcParent :: TyConParent -- ^ Gives the family declaration 'TyCon'
344 -- of 'TyCon's representing family instances
348 -- | Primitive types; cannot be defined in Haskell. This includes
349 -- the usual suspects (such as @Int#@) as well as foreign-imported
352 tyConUnique :: Unique,
355 tyConArity :: Arity, -- SLPJ Oct06: I'm not sure what the significance
356 -- of the arity of a primtycon is!
358 primTyConRep :: PrimRep, -- ^ Many primitive tycons are unboxed, but some are
359 -- boxed (represented by pointers). This 'PrimRep'
360 -- holds that information.
361 -- Only relevant if tc_kind = *
363 isUnLifted :: Bool, -- ^ Most primitive tycons are unlifted
364 -- (may not contain bottom)
365 -- but foreign-imported ones may be lifted
367 tyConExtName :: Maybe FastString -- ^ @Just e@ for foreign-imported types,
368 -- holds the name of the imported thing
371 -- | Type coercions, such as @(~)@, @sym@, @trans@, @left@ and @right@.
372 -- INVARIANT: Coercion TyCons are always fully applied
373 -- But note that a CoTyCon can be *over*-saturated in a type.
374 -- E.g. (sym g1) Int will be represented as (TyConApp sym [g1,Int])
376 tyConUnique :: Unique,
379 coTcDesc :: CoTyConDesc
382 -- | Any types. Like tuples, this is a potentially-infinite family of TyCons
383 -- one for each distinct Kind. They have no values at all.
384 -- Because there are infinitely many of them (like tuples) they are
385 -- defined in GHC.Prim and have names like "Any(*->*)".
386 -- Their Unique is derived from the OccName.
387 -- See Note [Any types] in TysPrim
389 tyConUnique :: Unique,
391 tc_kind :: Kind -- Never = *; that is done via PrimTyCon
392 -- See Note [Any types] in TysPrim
395 -- | Super-kinds. These are "kinds-of-kinds" and are never seen in
396 -- Haskell source programs. There are only two super-kinds: TY (aka
397 -- "box"), which is the super-kind of kinds that construct types
398 -- eventually, and CO (aka "diamond"), which is the super-kind of
399 -- kinds that just represent coercions.
401 -- Super-kinds have no kind themselves, and have arity zero
403 tyConUnique :: Unique,
407 -- | Names of the fields in an algebraic record type
408 type FieldLabel = Name
410 -- | Represents right-hand-sides of 'TyCon's for algebraic types
413 -- | Says that we know nothing about this data type, except that
414 -- it's represented by a pointer. Used when we export a data type
415 -- abstractly into an .hi file.
418 -- | Represents an open type family without a fixed right hand
419 -- side. Additional instances can appear at any time.
421 -- These are introduced by either a top level declaration:
425 -- Or an associated data type declaration, within a class declaration:
427 -- > class C a b where
431 -- | Information about those 'TyCon's derived from a @data@
432 -- declaration. This includes data types with no constructors at
435 data_cons :: [DataCon],
436 -- ^ The data type constructors; can be empty if the user
437 -- declares the type to have no constructors
439 -- INVARIANT: Kept in order of increasing 'DataCon' tag
440 -- (see the tag assignment in DataCon.mkDataCon)
442 is_enum :: Bool -- ^ Cached value: is this an enumeration type?
443 -- (See 'isEnumerationTyCon')
446 -- | Information about those 'TyCon's derived from a @newtype@ declaration
448 data_con :: DataCon, -- ^ The unique constructor for the @newtype@.
449 -- It has no existentials
451 nt_rhs :: Type, -- ^ Cached value: the argument type of the constructor,
452 -- which is just the representation type of the 'TyCon'
453 -- (remember that @newtype@s do not exist at runtime
454 -- so need a different representation type).
456 -- The free 'TyVar's of this type are the 'tyConTyVars'
457 -- from the corresponding 'TyCon'
459 nt_etad_rhs :: ([TyVar], Type),
460 -- ^ Same as the 'nt_rhs', but this time eta-reduced.
461 -- Hence the list of 'TyVar's in this field may be
462 -- shorter than the declared arity of the 'TyCon'.
464 -- See Note [Newtype eta]
466 nt_co :: Maybe TyCon -- ^ A 'TyCon' (which is always a 'CoTyCon') that can
467 -- have a 'Coercion' extracted from it to create
468 -- the @newtype@ from the representation 'Type'.
470 -- This field is optional for non-recursive @newtype@s only.
472 -- See Note [Newtype coercions]
473 -- Invariant: arity = #tvs in nt_etad_rhs;
474 -- See Note [Newtype eta]
475 -- Watch out! If any newtypes become transparent
476 -- again check Trac #1072.
479 -- | Extract those 'DataCon's that we are able to learn about. Note
480 -- that visibility in this sense does not correspond to visibility in
481 -- the context of any particular user program!
482 visibleDataCons :: AlgTyConRhs -> [DataCon]
483 visibleDataCons AbstractTyCon = []
484 visibleDataCons DataFamilyTyCon {} = []
485 visibleDataCons (DataTyCon{ data_cons = cs }) = cs
486 visibleDataCons (NewTyCon{ data_con = c }) = [c]
488 -- ^ Both type classes as well as family instances imply implicit
489 -- type constructors. These implicit type constructors refer to their parent
490 -- structure (ie, the class or family from which they derive) using a type of
491 -- the following form. We use 'TyConParent' for both algebraic and synonym
492 -- types, but the variant 'ClassTyCon' will only be used by algebraic 'TyCon's.
494 = -- | An ordinary type constructor has no parent.
497 -- | Type constructors representing a class dictionary.
499 Class -- INVARIANT: the classTyCon of this Class is the current tycon
501 -- | An *associated* type of a class.
503 Class -- The class in whose declaration the family is declared
504 -- The 'tyConTyVars' of this 'TyCon' may mention some
505 -- of the same type variables as the classTyVars of the
506 -- parent 'Class'. E.g.
513 -- Here the 'a' is shared with the 'Class', and that is
514 -- important. In an instance declaration we expect the
515 -- two to be instantiated the same way. Eg.
518 -- instanc C [x] (Tree y) where
519 -- data T c [x] = T1 x | T2 c
522 -- | Type constructors representing an instance of a type family. Parameters:
524 -- 1) The type family in question
526 -- 2) Instance types; free variables are the 'tyConTyVars'
527 -- of the current 'TyCon' (not the family one). INVARIANT:
528 -- the number of types matches the arity of the family 'TyCon'
530 -- 3) A 'CoTyCon' identifying the representation
531 -- type with the type instance family
532 | FamInstTyCon -- See Note [Data type families]
533 -- and Note [Type synonym families]
534 TyCon -- The family TyCon
535 [Type] -- Argument types (mentions the tyConTyVars of this TyCon)
536 TyCon -- The coercion constructor
538 -- E.g. data intance T [a] = ...
539 -- gives a representation tycon:
540 -- data R:TList a = ...
541 -- axiom co a :: T [a] ~ R:TList a
542 -- with R:TList's algTcParent = FamInstTyCon T [a] co
544 -- | Checks the invariants of a 'TyConParent' given the appropriate type class name, if any
545 okParent :: Name -> TyConParent -> Bool
546 okParent _ NoParentTyCon = True
547 okParent tc_name (AssocFamilyTyCon cls) = tc_name `elem` map tyConName (classATs cls)
548 okParent tc_name (ClassTyCon cls) = tc_name == tyConName (classTyCon cls)
549 okParent _ (FamInstTyCon fam_tc tys _co_tc) = tyConArity fam_tc == length tys
551 isNoParent :: TyConParent -> Bool
552 isNoParent NoParentTyCon = True
557 -- | Information pertaining to the expansion of a type synonym (@type@)
559 = -- | An ordinary type synonyn.
561 Type -- This 'Type' is the rhs, and may mention from 'tyConTyVars'.
562 -- It acts as a template for the expansion when the 'TyCon'
563 -- is applied to some types.
565 -- | A type synonym family e.g. @type family F x y :: * -> *@
572 | CoCsel1 | CoCsel2 | CoCselR
575 | CoAxiom -- C tvs : F lhs-tys ~ rhs-ty
576 { co_ax_tvs :: [TyVar]
578 , co_ax_rhs :: Type }
583 Note [Newtype coercions]
584 ~~~~~~~~~~~~~~~~~~~~~~~~
585 The NewTyCon field nt_co is a a TyCon (a coercion constructor in fact)
586 which is used for coercing from the representation type of the
587 newtype, to the newtype itself. For example,
589 newtype T a = MkT (a -> a)
591 the NewTyCon for T will contain nt_co = CoT where CoT t : T t ~ t ->
592 t. This TyCon is a CoTyCon, so it does not have a kind on its
593 own; it basically has its own typing rule for the fully-applied
594 version. If the newtype T has k type variables then CoT has arity at
595 most k. In the case that the right hand side is a type application
596 ending with the same type variables as the left hand side, we
597 "eta-contract" the coercion. So if we had
599 newtype S a = MkT [a]
601 then we would generate the arity 0 coercion CoS : S ~ []. The
602 primary reason we do this is to make newtype deriving cleaner.
604 In the paper we'd write
605 axiom CoT : (forall t. T t) ~ (forall t. [t])
606 and then when we used CoT at a particular type, s, we'd say
608 which encodes as (TyConApp instCoercionTyCon [TyConApp CoT [], s])
610 But in GHC we instead make CoT into a new piece of type syntax, CoTyCon,
611 (like instCoercionTyCon, symCoercionTyCon etc), which must always
612 be saturated, but which encodes as
614 In the vocabulary of the paper it's as if we had axiom declarations
616 axiom CoT t : T t ~ [t]
621 newtype Parser m a = MkParser (Foogle m a)
622 Are these two types equal (to Core)?
625 Well, yes. But to see that easily we eta-reduce the RHS type of
626 Parser, in this case to ([], Froogle), so that even unsaturated applications
627 of Parser will work right. This eta reduction is done when the type
628 constructor is built, and cached in NewTyCon. The cached field is
629 only used in coreExpandTyCon_maybe.
631 Here's an example that I think showed up in practice
633 newtype T a = MkT [a]
634 newtype Foo m = MkFoo (forall a. m a -> Int)
640 w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
642 After desugaring, and discarding the data constructors for the newtypes,
646 And now Lint complains unless Foo T == Foo [], and that requires T==[]
648 This point carries over to the newtype coercion, because we need to
650 w2 = w1 `cast` Foo CoT
652 so the coercion tycon CoT must have
657 %************************************************************************
661 %************************************************************************
663 A PrimRep is somewhat similar to a CgRep (see codeGen/SMRep) and a
664 MachRep (see cmm/CmmExpr), although each of these types has a distinct
665 and clearly defined purpose:
667 - A PrimRep is a CgRep + information about signedness + information
668 about primitive pointers (AddrRep). Signedness and primitive
669 pointers are required when passing a primitive type to a foreign
670 function, but aren't needed for call/return conventions of Haskell
673 - A MachRep is a basic machine type (non-void, doesn't contain
674 information on pointerhood or signedness, but contains some
675 reps that don't have corresponding Haskell types).
678 -- | A 'PrimRep' is an abstraction of a type. It contains information that
679 -- the code generator needs in order to pass arguments, return results,
680 -- and store values of this type.
684 | IntRep -- ^ Signed, word-sized value
685 | WordRep -- ^ Unsigned, word-sized value
686 | Int64Rep -- ^ Signed, 64 bit value (with 32-bit words only)
687 | Word64Rep -- ^ Unsigned, 64 bit value (with 32-bit words only)
688 | AddrRep -- ^ A pointer, but /not/ to a Haskell value (use 'PtrRep')
693 instance Outputable PrimRep where
694 ppr r = text (show r)
696 -- | Find the size of a 'PrimRep', in words
697 primRepSizeW :: PrimRep -> Int
698 primRepSizeW IntRep = 1
699 primRepSizeW WordRep = 1
700 primRepSizeW Int64Rep = wORD64_SIZE `quot` wORD_SIZE
701 primRepSizeW Word64Rep= wORD64_SIZE `quot` wORD_SIZE
702 primRepSizeW FloatRep = 1 -- NB. might not take a full word
703 primRepSizeW DoubleRep= dOUBLE_SIZE `quot` wORD_SIZE
704 primRepSizeW AddrRep = 1
705 primRepSizeW PtrRep = 1
706 primRepSizeW VoidRep = 0
709 %************************************************************************
711 \subsection{TyCon Construction}
713 %************************************************************************
715 Note: the TyCon constructors all take a Kind as one argument, even though
716 they could, in principle, work out their Kind from their other arguments.
717 But to do so they need functions from Types, and that makes a nasty
718 module mutual-recursion. And they aren't called from many places.
719 So we compromise, and move their Kind calculation to the call site.
722 -- | Given the name of the function type constructor and it's kind, create the
723 -- corresponding 'TyCon'. It is reccomended to use 'TypeRep.funTyCon' if you want
724 -- this functionality
725 mkFunTyCon :: Name -> Kind -> TyCon
728 tyConUnique = nameUnique name,
734 -- | This is the making of an algebraic 'TyCon'. Notably, you have to
735 -- pass in the generic (in the -XGenerics sense) information about the
736 -- type constructor - you can get hold of it easily (see Generics
739 -> Kind -- ^ Kind of the resulting 'TyCon'
740 -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'.
741 -- Arity is inferred from the length of this list
742 -> [PredType] -- ^ Stupid theta: see 'algTcStupidTheta'
743 -> AlgTyConRhs -- ^ Information about dat aconstructors
745 -> RecFlag -- ^ Is the 'TyCon' recursive?
746 -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
747 -> Bool -- ^ Was the 'TyCon' declared with GADT syntax?
749 mkAlgTyCon name kind tyvars stupid rhs parent is_rec gen_info gadt_syn
752 tyConUnique = nameUnique name,
754 tyConArity = length tyvars,
755 tyConTyVars = tyvars,
756 algTcStupidTheta = stupid,
758 algTcParent = ASSERT( okParent name parent ) parent,
760 algTcGadtSyntax = gadt_syn,
761 hasGenerics = gen_info
764 -- | Simpler specialization of 'mkAlgTyCon' for classes
765 mkClassTyCon :: Name -> Kind -> [TyVar] -> AlgTyConRhs -> Class -> RecFlag -> TyCon
766 mkClassTyCon name kind tyvars rhs clas is_rec =
767 mkAlgTyCon name kind tyvars [] rhs (ClassTyCon clas) is_rec False False
770 -> Kind -- ^ Kind of the resulting 'TyCon'
771 -> Arity -- ^ Arity of the tuple
772 -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'
774 -> Boxity -- ^ Whether the tuple is boxed or unboxed
775 -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
777 mkTupleTyCon name kind arity tyvars con boxed gen_info
779 tyConUnique = nameUnique name,
784 tyConTyVars = tyvars,
786 hasGenerics = gen_info
789 -- ^ Foreign-imported (.NET) type constructors are represented
790 -- as primitive, but /lifted/, 'TyCons' for now. They are lifted
791 -- because the Haskell type @T@ representing the (foreign) .NET
792 -- type @T@ is actually implemented (in ILX) as a @thunk<T>@
793 mkForeignTyCon :: Name
794 -> Maybe FastString -- ^ Name of the foreign imported thing, maybe
798 mkForeignTyCon name ext_name kind arity
801 tyConUnique = nameUnique name,
804 primTyConRep = PtrRep, -- they all do
806 tyConExtName = ext_name
810 -- | Create an unlifted primitive 'TyCon', such as @Int#@
811 mkPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
812 mkPrimTyCon name kind arity rep
813 = mkPrimTyCon' name kind arity rep True
815 -- | Kind constructors
816 mkKindTyCon :: Name -> Kind -> TyCon
817 mkKindTyCon name kind
818 = mkPrimTyCon' name kind 0 VoidRep True
820 -- | Create a lifted primitive 'TyCon' such as @RealWorld@
821 mkLiftedPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
822 mkLiftedPrimTyCon name kind arity rep
823 = mkPrimTyCon' name kind arity rep False
825 mkPrimTyCon' :: Name -> Kind -> Arity -> PrimRep -> Bool -> TyCon
826 mkPrimTyCon' name kind arity rep is_unlifted
829 tyConUnique = nameUnique name,
833 isUnLifted = is_unlifted,
834 tyConExtName = Nothing
837 -- | Create a type synonym 'TyCon'
838 mkSynTyCon :: Name -> Kind -> [TyVar] -> SynTyConRhs -> TyConParent -> TyCon
839 mkSynTyCon name kind tyvars rhs parent
842 tyConUnique = nameUnique name,
844 tyConArity = length tyvars,
845 tyConTyVars = tyvars,
850 -- | Create a coercion 'TyCon'
851 mkCoercionTyCon :: Name -> Arity
854 mkCoercionTyCon name arity desc
857 tyConUnique = nameUnique name,
861 mkAnyTyCon :: Name -> Kind -> TyCon
863 = AnyTyCon { tyConName = name,
865 tyConUnique = nameUnique name }
867 -- | Create a super-kind 'TyCon'
868 mkSuperKindTyCon :: Name -> TyCon -- Super kinds always have arity zero
869 mkSuperKindTyCon name
872 tyConUnique = nameUnique name
877 isFunTyCon :: TyCon -> Bool
878 isFunTyCon (FunTyCon {}) = True
881 -- | Test if the 'TyCon' is algebraic but abstract (invisible data constructors)
882 isAbstractTyCon :: TyCon -> Bool
883 isAbstractTyCon (AlgTyCon { algTcRhs = AbstractTyCon }) = True
884 isAbstractTyCon _ = False
886 -- | Make an algebraic 'TyCon' abstract. Panics if the supplied 'TyCon' is not algebraic
887 makeTyConAbstract :: TyCon -> TyCon
888 makeTyConAbstract tc@(AlgTyCon {}) = tc { algTcRhs = AbstractTyCon }
889 makeTyConAbstract tc = pprPanic "makeTyConAbstract" (ppr tc)
891 -- | Does this 'TyCon' represent something that cannot be defined in Haskell?
892 isPrimTyCon :: TyCon -> Bool
893 isPrimTyCon (PrimTyCon {}) = True
894 isPrimTyCon _ = False
896 -- | Is this 'TyCon' unlifted (i.e. cannot contain bottom)? Note that this can only
897 -- be true for primitive and unboxed-tuple 'TyCon's
898 isUnLiftedTyCon :: TyCon -> Bool
899 isUnLiftedTyCon (PrimTyCon {isUnLifted = is_unlifted}) = is_unlifted
900 isUnLiftedTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
901 isUnLiftedTyCon _ = False
903 -- | Returns @True@ if the supplied 'TyCon' resulted from either a
904 -- @data@ or @newtype@ declaration
905 isAlgTyCon :: TyCon -> Bool
906 isAlgTyCon (AlgTyCon {}) = True
907 isAlgTyCon (TupleTyCon {}) = True
910 isDataTyCon :: TyCon -> Bool
911 -- ^ Returns @True@ for data types that are /definitely/ represented by
912 -- heap-allocated constructors. These are scrutinised by Core-level
913 -- @case@ expressions, and they get info tables allocated for them.
915 -- Generally, the function will be true for all @data@ types and false
916 -- for @newtype@s, unboxed tuples and type family 'TyCon's. But it is
917 -- not guarenteed to return @True@ in all cases that it could.
919 -- NB: for a data type family, only the /instance/ 'TyCon's
920 -- get an info table. The family declaration 'TyCon' does not
921 isDataTyCon (AlgTyCon {algTcRhs = rhs})
923 DataFamilyTyCon {} -> False
926 AbstractTyCon -> False -- We don't know, so return False
927 isDataTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
928 isDataTyCon _ = False
930 -- | Is this 'TyCon' that for a @newtype@
931 isNewTyCon :: TyCon -> Bool
932 isNewTyCon (AlgTyCon {algTcRhs = NewTyCon {}}) = True
935 -- | Take a 'TyCon' apart into the 'TyVar's it scopes over, the 'Type' it expands
936 -- into, and (possibly) a coercion from the representation type to the @newtype@.
937 -- Returns @Nothing@ if this is not possible.
938 unwrapNewTyCon_maybe :: TyCon -> Maybe ([TyVar], Type, Maybe TyCon)
939 unwrapNewTyCon_maybe (AlgTyCon { tyConTyVars = tvs,
940 algTcRhs = NewTyCon { nt_co = mb_co,
942 = Just (tvs, rhs, mb_co)
943 unwrapNewTyCon_maybe _ = Nothing
945 isProductTyCon :: TyCon -> Bool
946 -- | A /product/ 'TyCon' must both:
948 -- 1. Have /one/ constructor
950 -- 2. /Not/ be existential
952 -- However other than this there are few restrictions: they may be @data@ or @newtype@
953 -- 'TyCon's of any boxity and may even be recursive.
954 isProductTyCon tc@(AlgTyCon {}) = case algTcRhs tc of
955 DataTyCon{ data_cons = [data_con] }
956 -> isVanillaDataCon data_con
959 isProductTyCon (TupleTyCon {}) = True
960 isProductTyCon _ = False
962 -- | Is this a 'TyCon' representing a type synonym (@type@)?
963 isSynTyCon :: TyCon -> Bool
964 isSynTyCon (SynTyCon {}) = True
967 -- As for newtypes, it is in some contexts important to distinguish between
968 -- closed synonyms and synonym families, as synonym families have no unique
969 -- right hand side to which a synonym family application can expand.
972 isDecomposableTyCon :: TyCon -> Bool
973 -- True iff we can decompose (T a b c) into ((T a b) c)
974 -- Specifically NOT true of synonyms (open and otherwise) and coercions
975 isDecomposableTyCon (SynTyCon {}) = False
976 isDecomposableTyCon (CoTyCon {}) = False
977 isDecomposableTyCon _other = True
979 -- | Is this an algebraic 'TyCon' declared with the GADT syntax?
980 isGadtSyntaxTyCon :: TyCon -> Bool
981 isGadtSyntaxTyCon (AlgTyCon { algTcGadtSyntax = res }) = res
982 isGadtSyntaxTyCon _ = False
984 -- | Is this an algebraic 'TyCon' which is just an enumeration of values?
985 isEnumerationTyCon :: TyCon -> Bool
986 isEnumerationTyCon (AlgTyCon {algTcRhs = DataTyCon { is_enum = res }}) = res
987 isEnumerationTyCon (TupleTyCon {tyConArity = arity}) = arity == 0
988 isEnumerationTyCon _ = False
990 -- | Is this a 'TyCon', synonym or otherwise, that may have further instances appear?
991 isFamilyTyCon :: TyCon -> Bool
992 isFamilyTyCon (SynTyCon {synTcRhs = SynFamilyTyCon {}}) = True
993 isFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True
994 isFamilyTyCon _ = False
996 -- | Is this a synonym 'TyCon' that can have may have further instances appear?
997 isSynFamilyTyCon :: TyCon -> Bool
998 isSynFamilyTyCon (SynTyCon {synTcRhs = SynFamilyTyCon {}}) = True
999 isSynFamilyTyCon _ = False
1001 -- | Is this a synonym 'TyCon' that can have may have further instances appear?
1002 isDataFamilyTyCon :: TyCon -> Bool
1003 isDataFamilyTyCon (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = True
1004 isDataFamilyTyCon _ = False
1006 -- | Is this a synonym 'TyCon' that can have no further instances appear?
1007 isClosedSynTyCon :: TyCon -> Bool
1008 isClosedSynTyCon tycon = isSynTyCon tycon && not (isFamilyTyCon tycon)
1010 -- | Injective 'TyCon's can be decomposed, so that
1011 -- T ty1 ~ T ty2 => ty1 ~ ty2
1012 isInjectiveTyCon :: TyCon -> Bool
1013 isInjectiveTyCon tc = not (isSynTyCon tc)
1014 -- Ultimately we may have injective associated types
1015 -- in which case this test will become more interesting
1017 -- It'd be unusual to call isInjectiveTyCon on a regular H98
1018 -- type synonym, because you should probably have expanded it first
1019 -- But regardless, it's not injective!
1021 -- | Are we able to extract informationa 'TyVar' to class argument list
1022 -- mappping from a given 'TyCon'?
1023 isTyConAssoc :: TyCon -> Bool
1024 isTyConAssoc tc = case tyConParent tc of
1025 AssocFamilyTyCon {} -> True
1028 -- The unit tycon didn't used to be classed as a tuple tycon
1029 -- but I thought that was silly so I've undone it
1030 -- If it can't be for some reason, it should be a AlgTyCon
1031 isTupleTyCon :: TyCon -> Bool
1032 -- ^ Does this 'TyCon' represent a tuple?
1034 -- NB: when compiling @Data.Tuple@, the tycons won't reply @True@ to
1035 -- 'isTupleTyCon', becuase they are built as 'AlgTyCons'. However they
1036 -- get spat into the interface file as tuple tycons, so I don't think
1038 isTupleTyCon (TupleTyCon {}) = True
1039 isTupleTyCon _ = False
1041 -- | Is this the 'TyCon' for an unboxed tuple?
1042 isUnboxedTupleTyCon :: TyCon -> Bool
1043 isUnboxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
1044 isUnboxedTupleTyCon _ = False
1046 -- | Is this the 'TyCon' for a boxed tuple?
1047 isBoxedTupleTyCon :: TyCon -> Bool
1048 isBoxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
1049 isBoxedTupleTyCon _ = False
1051 -- | Extract the boxity of the given 'TyCon', if it is a 'TupleTyCon'.
1053 tupleTyConBoxity :: TyCon -> Boxity
1054 tupleTyConBoxity tc = tyConBoxed tc
1056 -- | Is this a recursive 'TyCon'?
1057 isRecursiveTyCon :: TyCon -> Bool
1058 isRecursiveTyCon (AlgTyCon {algTcRec = Recursive}) = True
1059 isRecursiveTyCon _ = False
1061 -- | Did this 'TyCon' originate from type-checking a .h*-boot file?
1062 isHiBootTyCon :: TyCon -> Bool
1063 -- Used for knot-tying in hi-boot files
1064 isHiBootTyCon (AlgTyCon {algTcRhs = AbstractTyCon}) = True
1065 isHiBootTyCon _ = False
1067 -- | Is this the 'TyCon' of a foreign-imported type constructor?
1068 isForeignTyCon :: TyCon -> Bool
1069 isForeignTyCon (PrimTyCon {tyConExtName = Just _}) = True
1070 isForeignTyCon _ = False
1072 -- | Is this a super-kind 'TyCon'?
1073 isSuperKindTyCon :: TyCon -> Bool
1074 isSuperKindTyCon (SuperKindTyCon {}) = True
1075 isSuperKindTyCon _ = False
1077 -- | Is this an AnyTyCon?
1078 isAnyTyCon :: TyCon -> Bool
1079 isAnyTyCon (AnyTyCon {}) = True
1080 isAnyTyCon _ = False
1082 -- | Attempt to pull a 'TyCon' apart into the arity and 'coKindFun' of
1083 -- a coercion 'TyCon'. Returns @Nothing@ if the 'TyCon' is not of the
1085 isCoercionTyCon_maybe :: TyCon -> Maybe (Arity, CoTyConDesc)
1086 isCoercionTyCon_maybe (CoTyCon {tyConArity = ar, coTcDesc = desc})
1088 isCoercionTyCon_maybe _ = Nothing
1090 -- | Is this a 'TyCon' that represents a coercion?
1091 isCoercionTyCon :: TyCon -> Bool
1092 isCoercionTyCon (CoTyCon {}) = True
1093 isCoercionTyCon _ = False
1095 -- | Identifies implicit tycons that, in particular, do not go into interface
1096 -- files (because they are implicitly reconstructed when the interface is
1101 -- * Associated families are implicit, as they are re-constructed from
1102 -- the class declaration in which they reside, and
1104 -- * Family instances are /not/ implicit as they represent the instance body
1105 -- (similar to a @dfun@ does that for a class instance).
1106 isImplicitTyCon :: TyCon -> Bool
1107 isImplicitTyCon tycon | isTyConAssoc tycon = True
1108 | isSynTyCon tycon = False
1109 | isAlgTyCon tycon = isClassTyCon tycon ||
1111 isImplicitTyCon _other = True
1112 -- catches: FunTyCon, PrimTyCon,
1113 -- CoTyCon, SuperKindTyCon
1117 -----------------------------------------------
1118 -- Expand type-constructor applications
1119 -----------------------------------------------
1122 tcExpandTyCon_maybe, coreExpandTyCon_maybe
1124 -> [Type] -- ^ Arguments to 'TyCon'
1125 -> Maybe ([(TyVar,Type)],
1127 [Type]) -- ^ Returns a 'TyVar' substitution, the body type
1128 -- of the synonym (not yet substituted) and any arguments
1129 -- remaining from the application
1131 -- ^ Used to create the view the /typechecker/ has on 'TyCon's. We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
1132 tcExpandTyCon_maybe (SynTyCon {tyConTyVars = tvs,
1133 synTcRhs = SynonymTyCon rhs }) tys
1134 = expand tvs rhs tys
1135 tcExpandTyCon_maybe _ _ = Nothing
1139 -- ^ Used to create the view /Core/ has on 'TyCon's. We expand not only closed synonyms like 'tcExpandTyCon_maybe',
1140 -- but also non-recursive @newtype@s
1141 coreExpandTyCon_maybe (AlgTyCon {
1142 algTcRhs = NewTyCon { nt_etad_rhs = etad_rhs, nt_co = Nothing }}) tys
1143 = case etad_rhs of -- Don't do this in the pattern match, lest we accidentally
1144 -- match the etad_rhs of a *recursive* newtype
1145 (tvs,rhs) -> expand tvs rhs tys
1147 coreExpandTyCon_maybe tycon tys = tcExpandTyCon_maybe tycon tys
1151 expand :: [TyVar] -> Type -- Template
1153 -> Maybe ([(TyVar,Type)], Type, [Type]) -- Expansion
1155 = case n_tvs `compare` length tys of
1156 LT -> Just (tvs `zip` tys, rhs, drop n_tvs tys)
1157 EQ -> Just (tvs `zip` tys, rhs, [])
1164 -- | Does this 'TyCon' have any generic to\/from functions available? See also 'hasGenerics'
1165 tyConHasGenerics :: TyCon -> Bool
1166 tyConHasGenerics (AlgTyCon {hasGenerics = hg}) = hg
1167 tyConHasGenerics (TupleTyCon {hasGenerics = hg}) = hg
1168 tyConHasGenerics _ = False -- Synonyms
1170 tyConKind :: TyCon -> Kind
1171 tyConKind (FunTyCon { tc_kind = k }) = k
1172 tyConKind (AlgTyCon { tc_kind = k }) = k
1173 tyConKind (TupleTyCon { tc_kind = k }) = k
1174 tyConKind (SynTyCon { tc_kind = k }) = k
1175 tyConKind (PrimTyCon { tc_kind = k }) = k
1176 tyConKind (AnyTyCon { tc_kind = k }) = k
1177 tyConKind tc = pprPanic "tyConKind" (ppr tc) -- SuperKindTyCon and CoTyCon
1179 tyConHasKind :: TyCon -> Bool
1180 tyConHasKind (SuperKindTyCon {}) = False
1181 tyConHasKind (CoTyCon {}) = False
1182 tyConHasKind _ = True
1184 -- | As 'tyConDataCons_maybe', but returns the empty list of constructors if no constructors
1186 tyConDataCons :: TyCon -> [DataCon]
1187 -- It's convenient for tyConDataCons to return the
1188 -- empty list for type synonyms etc
1189 tyConDataCons tycon = tyConDataCons_maybe tycon `orElse` []
1191 -- | Determine the 'DataCon's originating from the given 'TyCon', if the 'TyCon' is the
1192 -- sort that can have any constructors (note: this does not include abstract algebraic types)
1193 tyConDataCons_maybe :: TyCon -> Maybe [DataCon]
1194 tyConDataCons_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = cons }}) = Just cons
1195 tyConDataCons_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = con }}) = Just [con]
1196 tyConDataCons_maybe (TupleTyCon {dataCon = con}) = Just [con]
1197 tyConDataCons_maybe _ = Nothing
1199 -- | Determine the number of value constructors a 'TyCon' has. Panics if the 'TyCon'
1200 -- is not algebraic or a tuple
1201 tyConFamilySize :: TyCon -> Int
1202 tyConFamilySize (AlgTyCon {algTcRhs = DataTyCon {data_cons = cons}}) =
1204 tyConFamilySize (AlgTyCon {algTcRhs = NewTyCon {}}) = 1
1205 tyConFamilySize (AlgTyCon {algTcRhs = DataFamilyTyCon {}}) = 0
1206 tyConFamilySize (TupleTyCon {}) = 1
1207 tyConFamilySize other = pprPanic "tyConFamilySize:" (ppr other)
1209 -- | Extract an 'AlgTyConRhs' with information about data constructors from an algebraic or tuple
1210 -- 'TyCon'. Panics for any other sort of 'TyCon'
1211 algTyConRhs :: TyCon -> AlgTyConRhs
1212 algTyConRhs (AlgTyCon {algTcRhs = rhs}) = rhs
1213 algTyConRhs (TupleTyCon {dataCon = con, tyConArity = arity})
1214 = DataTyCon { data_cons = [con], is_enum = arity == 0 }
1215 algTyConRhs other = pprPanic "algTyConRhs" (ppr other)
1219 -- | Extract the bound type variables and type expansion of a type synonym 'TyCon'. Panics if the
1220 -- 'TyCon' is not a synonym
1221 newTyConRhs :: TyCon -> ([TyVar], Type)
1222 newTyConRhs (AlgTyCon {tyConTyVars = tvs, algTcRhs = NewTyCon { nt_rhs = rhs }}) = (tvs, rhs)
1223 newTyConRhs tycon = pprPanic "newTyConRhs" (ppr tycon)
1225 -- | Extract the bound type variables and type expansion of an eta-contracted type synonym 'TyCon'.
1226 -- Panics if the 'TyCon' is not a synonym
1227 newTyConEtadRhs :: TyCon -> ([TyVar], Type)
1228 newTyConEtadRhs (AlgTyCon {algTcRhs = NewTyCon { nt_etad_rhs = tvs_rhs }}) = tvs_rhs
1229 newTyConEtadRhs tycon = pprPanic "newTyConEtadRhs" (ppr tycon)
1231 -- | Extracts the @newtype@ coercion from such a 'TyCon', which can be used to construct something
1232 -- with the @newtype@s type from its representation type (right hand side). If the supplied 'TyCon'
1233 -- is not a @newtype@, returns @Nothing@
1234 newTyConCo_maybe :: TyCon -> Maybe TyCon
1235 newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = co
1236 newTyConCo_maybe _ = Nothing
1238 -- | Find the primitive representation of a 'TyCon'
1239 tyConPrimRep :: TyCon -> PrimRep
1240 tyConPrimRep (PrimTyCon {primTyConRep = rep}) = rep
1241 tyConPrimRep tc = ASSERT(not (isUnboxedTupleTyCon tc)) PtrRep
1245 -- | Find the \"stupid theta\" of the 'TyCon'. A \"stupid theta\" is the context to the left of
1246 -- an algebraic type declaration, e.g. @Eq a@ in the declaration @data Eq a => T a ...@
1247 tyConStupidTheta :: TyCon -> [PredType]
1248 tyConStupidTheta (AlgTyCon {algTcStupidTheta = stupid}) = stupid
1249 tyConStupidTheta (TupleTyCon {}) = []
1250 tyConStupidTheta tycon = pprPanic "tyConStupidTheta" (ppr tycon)
1254 -- | Extract the 'TyVar's bound by a type synonym and the corresponding (unsubstituted) right hand side.
1255 -- If the given 'TyCon' is not a type synonym, panics
1256 synTyConDefn :: TyCon -> ([TyVar], Type)
1257 synTyConDefn (SynTyCon {tyConTyVars = tyvars, synTcRhs = SynonymTyCon ty})
1259 synTyConDefn tycon = pprPanic "getSynTyConDefn" (ppr tycon)
1261 -- | Extract the information pertaining to the right hand side of a type synonym (@type@) declaration. Panics
1262 -- if the given 'TyCon' is not a type synonym
1263 synTyConRhs :: TyCon -> SynTyConRhs
1264 synTyConRhs (SynTyCon {synTcRhs = rhs}) = rhs
1265 synTyConRhs tc = pprPanic "synTyConRhs" (ppr tc)
1267 -- | Find the expansion of the type synonym represented by the given 'TyCon'. The free variables of this
1268 -- type will typically include those 'TyVar's bound by the 'TyCon'. Panics if the 'TyCon' is not that of
1270 synTyConType :: TyCon -> Type
1271 synTyConType tc = case synTcRhs tc of
1273 _ -> pprPanic "synTyConType" (ppr tc)
1277 -- | If the given 'TyCon' has a /single/ data constructor, i.e. it is a @data@ type with one
1278 -- alternative, a tuple type or a @newtype@ then that constructor is returned. If the 'TyCon'
1279 -- has more than one constructor, or represents a primitive or function type constructor then
1280 -- @Nothing@ is returned. In any other case, the function panics
1281 tyConSingleDataCon_maybe :: TyCon -> Maybe DataCon
1282 tyConSingleDataCon_maybe (TupleTyCon {dataCon = c}) = Just c
1283 tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = [c] }}) = Just c
1284 tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = c }}) = Just c
1285 tyConSingleDataCon_maybe _ = Nothing
1289 -- | Is this 'TyCon' that for a class instance?
1290 isClassTyCon :: TyCon -> Bool
1291 isClassTyCon (AlgTyCon {algTcParent = ClassTyCon _}) = True
1292 isClassTyCon _ = False
1294 -- | If this 'TyCon' is that for a class instance, return the class it is for.
1295 -- Otherwise returns @Nothing@
1296 tyConClass_maybe :: TyCon -> Maybe Class
1297 tyConClass_maybe (AlgTyCon {algTcParent = ClassTyCon clas}) = Just clas
1298 tyConClass_maybe _ = Nothing
1300 ----------------------------------------------------------------------------
1301 tyConParent :: TyCon -> TyConParent
1302 tyConParent (AlgTyCon {algTcParent = parent}) = parent
1303 tyConParent (SynTyCon {synTcParent = parent}) = parent
1304 tyConParent _ = NoParentTyCon
1306 -- | Is this 'TyCon' that for a family instance, be that for a synonym or an
1307 -- algebraic family instance?
1308 isFamInstTyCon :: TyCon -> Bool
1309 isFamInstTyCon tc = case tyConParent tc of
1310 FamInstTyCon {} -> True
1313 tyConFamInstSig_maybe :: TyCon -> Maybe (TyCon, [Type], TyCon)
1314 tyConFamInstSig_maybe tc
1315 = case tyConParent tc of
1316 FamInstTyCon f ts co_tc -> Just (f, ts, co_tc)
1319 -- | If this 'TyCon' is that of a family instance, return the family in question
1320 -- and the instance types. Otherwise, return @Nothing@
1321 tyConFamInst_maybe :: TyCon -> Maybe (TyCon, [Type])
1322 tyConFamInst_maybe tc
1323 = case tyConParent tc of
1324 FamInstTyCon f ts _ -> Just (f, ts)
1327 -- | If this 'TyCon' is that of a family instance, return a 'TyCon' which represents
1328 -- a coercion identifying the representation type with the type instance family.
1329 -- Otherwise, return @Nothing@
1330 tyConFamilyCoercion_maybe :: TyCon -> Maybe TyCon
1331 tyConFamilyCoercion_maybe tc
1332 = case tyConParent tc of
1333 FamInstTyCon _ _ co -> Just co
1338 %************************************************************************
1340 \subsection[TyCon-instances]{Instance declarations for @TyCon@}
1342 %************************************************************************
1344 @TyCon@s are compared by comparing their @Unique@s.
1346 The strictness analyser needs @Ord@. It is a lexicographic order with
1347 the property @(a<=b) || (b<=a)@.
1350 instance Eq TyCon where
1351 a == b = case (a `compare` b) of { EQ -> True; _ -> False }
1352 a /= b = case (a `compare` b) of { EQ -> False; _ -> True }
1354 instance Ord TyCon where
1355 a <= b = case (a `compare` b) of { LT -> True; EQ -> True; GT -> False }
1356 a < b = case (a `compare` b) of { LT -> True; EQ -> False; GT -> False }
1357 a >= b = case (a `compare` b) of { LT -> False; EQ -> True; GT -> True }
1358 a > b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True }
1359 compare a b = getUnique a `compare` getUnique b
1361 instance Uniquable TyCon where
1362 getUnique tc = tyConUnique tc
1364 instance Outputable CoTyConDesc where
1365 ppr CoSym = ptext (sLit "SYM")
1366 ppr CoTrans = ptext (sLit "TRANS")
1367 ppr CoLeft = ptext (sLit "LEFT")
1368 ppr CoRight = ptext (sLit "RIGHT")
1369 ppr CoCsel1 = ptext (sLit "CSEL1")
1370 ppr CoCsel2 = ptext (sLit "CSEL2")
1371 ppr CoCselR = ptext (sLit "CSELR")
1372 ppr CoInst = ptext (sLit "INST")
1373 ppr CoUnsafe = ptext (sLit "UNSAFE")
1374 ppr (CoAxiom {}) = ptext (sLit "AXIOM")
1376 instance Outputable TyCon where
1377 ppr tc = ppr (getName tc)
1379 instance NamedThing TyCon where
1382 instance Data.Typeable TyCon where
1383 typeOf _ = Data.mkTyConApp (Data.mkTyCon "TyCon") []
1385 instance Data.Data TyCon where
1387 toConstr _ = abstractConstr "TyCon"
1388 gunfold _ _ = error "gunfold"
1389 dataTypeOf _ = mkNoRepType "TyCon"