2 % (c) The University of Glasgow 2006
3 % (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
10 -- * Main TyCon data types
11 TyCon, FieldLabel, CoTyConKindChecker,
13 AlgTyConRhs(..), visibleDataCons,
16 AssocFamilyPermutation,
18 -- ** Constructing TyCons
32 -- ** Predicates on TyCons
34 isClassTyCon, isFamInstTyCon,
37 isTupleTyCon, isUnboxedTupleTyCon, isBoxedTupleTyCon,
38 isSynTyCon, isClosedSynTyCon, isOpenSynTyCon,
39 isSuperKindTyCon, isDecomposableTyCon,
40 isCoercionTyCon, isCoercionTyCon_maybe,
41 isForeignTyCon, isAnyTyCon, tyConHasKind,
44 isDataTyCon, isProductTyCon, isEnumerationTyCon,
45 isNewTyCon, isAbstractTyCon, isOpenTyCon,
51 isImplicitTyCon, tyConHasGenerics,
53 -- ** Extracting information out of TyCons
58 tyConDataCons, tyConDataCons_maybe, tyConSingleDataCon_maybe,
63 tyConFamInst_maybe, tyConFamilyCoercion_maybe,
64 synTyConDefn, synTyConRhs, synTyConType, synTyConResKind,
65 tyConExtName, -- External name for foreign types
67 newTyConRhs, newTyConEtadRhs, unwrapNewTyCon_maybe,
68 assocTyConArgPoss_maybe,
71 -- ** Manipulating TyCons
72 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 )
97 import Data.List( elemIndex )
100 %************************************************************************
102 \subsection{The data type}
104 %************************************************************************
107 -- | TyCons represent type constructors. Type constructors are introduced by things such as:
109 -- 1) Data declarations: @data Foo = ...@ creates the @Foo@ type constructor of kind @*@
111 -- 2) Type synonyms: @type Foo = ...@ creates the @Foo@ type constructor
113 -- 3) Newtypes: @newtype Foo a = MkFoo ...@ creates the @Foo@ type constructor of kind @* -> *@
115 -- 4) Class declarations: @class Foo where@ creates the @Foo@ type constructor of kind @*@
117 -- 5) Type coercions! This is because we represent a coercion from @t1@ to @t2@ as a 'Type', where
118 -- that type has kind @t1 ~ t2@. See "Coercion" for more on this
120 -- This data type also encodes a number of primitive, built in type constructors such as those
121 -- for function and tuple types.
123 = -- | The function type constructor, @(->)@
125 tyConUnique :: Unique,
131 -- | Algebraic type constructors, which are defined to be those arising @data@ type and @newtype@ declarations.
132 -- All these constructors are lifted and boxed. See 'AlgTyConRhs' for more information.
134 tyConUnique :: Unique,
139 tyConTyVars :: [TyVar], -- ^ The type variables used in the type constructor.
140 -- Precisely, this list scopes over:
142 -- 1. The 'algTcStupidTheta'
144 -- 2. The cached types in 'algTyConRhs.NewTyCon'
146 -- 3. The family instance types if present
148 -- Note that it does /not/ scope over the data constructors.
150 algTcGadtSyntax :: Bool, -- ^ Was the data type declared with GADT syntax? If so,
151 -- that doesn't mean it's a true GADT; only that the "where"
152 -- form was used. This field is used only to guide
155 algTcStupidTheta :: [PredType], -- ^ The \"stupid theta\" for the data type (always empty for GADTs).
156 -- A \"stupid theta\" is the context to the left of an algebraic type
157 -- declaration, e.g. @Eq a@ in the declaration @data Eq a => T a ...@.
159 algTcRhs :: AlgTyConRhs, -- ^ Contains information about the data constructors of the algebraic type
161 algTcRec :: RecFlag, -- ^ Tells us whether the data type is part of a mutually-recursive group or not
163 hasGenerics :: Bool, -- ^ Whether generic (in the -XGenerics sense) to\/from functions are
164 -- available in the exports of the data type's source module.
166 algTcParent :: TyConParent -- ^ Gives the class or family declaration 'TyCon' for derived 'TyCon's
167 -- representing class or family instances, respectively. See also 'synTcParent'
170 -- | Represents the infinite family of tuple type constructors, @()@, @(a,b)@, @(# a, b #)@ etc.
172 tyConUnique :: Unique,
176 tyConBoxed :: Boxity,
177 tyConTyVars :: [TyVar],
178 dataCon :: DataCon, -- ^ Corresponding tuple data constructor
182 -- | Represents type synonyms
184 tyConUnique :: Unique,
189 tyConTyVars :: [TyVar], -- Bound tyvars
191 synTcRhs :: SynTyConRhs, -- ^ Contains information about the expansion of the synonym
193 synTcParent :: TyConParent -- ^ Gives the family declaration 'TyCon' of 'TyCon's representing family instances
197 -- | Primitive types; cannot be defined in Haskell. This includes the usual suspects (such as @Int#@)
198 -- as well as foreign-imported types and kinds
200 tyConUnique :: Unique,
203 tyConArity :: Arity, -- SLPJ Oct06: I'm not sure what the significance
204 -- of the arity of a primtycon is!
206 primTyConRep :: PrimRep, -- ^ Many primitive tycons are unboxed, but some are
207 -- boxed (represented by pointers). This 'PrimRep' holds
209 -- Only relevant if tc_kind = *
211 isUnLifted :: Bool, -- ^ Most primitive tycons are unlifted (may not contain bottom)
212 -- but foreign-imported ones may be lifted
214 tyConExtName :: Maybe FastString -- ^ @Just e@ for foreign-imported types,
215 -- holds the name of the imported thing
218 -- | Type coercions, such as @(~)@, @sym@, @trans@, @left@ and @right@.
219 -- INVARIANT: Coercion TyCons are always fully applied
220 -- But note that a CoercionTyCon can be over-saturated in a type.
221 -- E.g. (sym g1) Int will be represented as (TyConApp sym [g1,Int])
223 tyConUnique :: Unique,
226 coKindFun :: CoTyConKindChecker
229 -- | Any types. Like tuples, this is a potentially-infinite family of TyCons
230 -- one for each distinct Kind. They have no values at all.
231 -- Because there are infinitely many of them (like tuples) they are
232 -- defined in GHC.Prim and have names like "Any(*->*)".
233 -- Their Unique is derived from the OccName.
234 -- See Note [Any types] in TysPrim
236 tyConUnique :: Unique,
238 tc_kind :: Kind -- Never = *; that is done via PrimTyCon
239 -- See Note [Any types] in TysPrim
242 -- | Super-kinds. These are "kinds-of-kinds" and are never seen in Haskell source programs.
243 -- There are only two super-kinds: TY (aka "box"), which is the super-kind of kinds that
244 -- construct types eventually, and CO (aka "diamond"), which is the super-kind of kinds
245 -- that just represent coercions.
247 -- Super-kinds have no kind themselves, and have arity zero
249 tyConUnique :: Unique,
253 type CoTyConKindChecker = forall m. Monad m => CoTyConKindCheckerFun m
255 type CoTyConKindCheckerFun m
256 = (Type -> m Kind) -- Kind checker for types
257 -> (Type -> m (Type,Type)) -- and for coercions
258 -> Bool -- True => apply consistency checks
259 -> [Type] -- Exactly right number of args
260 -> m (Type, Type) -- Kind of this application
262 -- ^ Function that when given a list of the type arguments to the 'TyCon'
263 -- constructs the types that the resulting coercion relates.
264 -- Returns Nothing if ill-kinded.
266 -- INVARIANT: 'coKindFun' is always applied to exactly 'tyConArity' args
267 -- E.g. for @trans (c1 :: ta=tb) (c2 :: tb=tc)@, the 'coKindFun' returns
268 -- the kind as a pair of types: @(ta, tc)@
270 -- | Names of the fields in an algebraic record type
271 type FieldLabel = Name
273 -- | Represents right-hand-sides of 'TyCon's for algebraic types
276 -- | Says that we know nothing about this data type, except that it's represented
277 -- by a pointer. Used when we export a data type abstractly into an .hi file.
280 -- | Represents an open type family without a fixed right hand
281 -- side. Additional instances can appear at any time.
283 -- These are introduced by either a top level declaration:
287 -- Or an assoicated data type declaration, within a class declaration:
289 -- > class C a b where
293 otArgPoss :: AssocFamilyPermutation
296 -- | Information about those 'TyCon's derived from a @data@ declaration. This includes
297 -- data types with no constructors at all.
299 data_cons :: [DataCon],
300 -- ^ The data type constructors; can be empty if the user declares
301 -- the type to have no constructors
303 -- INVARIANT: Kept in order of increasing 'DataCon' tag
305 -- (see the tag assignment in DataCon.mkDataCon)
306 is_enum :: Bool -- ^ Cached value: is this an enumeration type? (See 'isEnumerationTyCon')
309 -- | Information about those 'TyCon's derived from a @newtype@ declaration
311 data_con :: DataCon, -- ^ The unique constructor for the @newtype@. It has no existentials
313 nt_rhs :: Type, -- ^ Cached value: the argument type of the constructor, which
314 -- is just the representation type of the 'TyCon' (remember that
315 -- @newtype@s do not exist at runtime so need a different representation
318 -- The free 'TyVar's of this type are the 'tyConTyVars' from the corresponding
321 nt_etad_rhs :: ([TyVar], Type),
322 -- ^ Same as the 'nt_rhs', but this time eta-reduced. Hence the list of 'TyVar's in
323 -- this field may be shorter than the declared arity of the 'TyCon'.
325 -- See Note [Newtype eta]
327 nt_co :: Maybe TyCon -- ^ A 'TyCon' (which is always a 'CoercionTyCon') that can have a 'Coercion'
328 -- extracted from it to create the @newtype@ from the representation 'Type'.
330 -- This field is optional for non-recursive @newtype@s only.
332 -- See Note [Newtype coercions]
333 -- Invariant: arity = #tvs in nt_etad_rhs;
334 -- See Note [Newtype eta]
335 -- Watch out! If any newtypes become transparent
336 -- again check Trac #1072.
339 type AssocFamilyPermutation
340 = Maybe [Int] -- Nothing for *top-level* type families
341 -- For *associated* type families, gives the position
342 -- of that 'TyVar' in the class argument list (0-indexed)
343 -- e.g. class C a b c where { type F c a :: *->* }
344 -- Then we get Just [2,0]
345 -- For *synonyms*, the length of the list is identical to
347 -- For *data types*, the length may be smaller than the
348 -- TyCon's arity; e.g. class C a where { data D a :: *->* }
349 -- here D gets arity 2
351 -- | Extract those 'DataCon's that we are able to learn about. Note that visibility in this sense does not
352 -- correspond to visibility in the context of any particular user program!
353 visibleDataCons :: AlgTyConRhs -> [DataCon]
354 visibleDataCons AbstractTyCon = []
355 visibleDataCons OpenTyCon {} = []
356 visibleDataCons (DataTyCon{ data_cons = cs }) = cs
357 visibleDataCons (NewTyCon{ data_con = c }) = [c]
359 -- ^ Both type classes as well as family instances imply implicit
360 -- type constructors. These implicit type constructors refer to their parent
361 -- structure (ie, the class or family from which they derive) using a type of
362 -- the following form. We use 'TyConParent' for both algebraic and synonym
363 -- types, but the variant 'ClassTyCon' will only be used by algebraic 'TyCon's.
365 = -- | An ordinary type constructor has no parent.
368 -- | Type constructors representing a class dictionary.
370 Class -- INVARIANT: the classTyCon of this Class is the current tycon
372 -- | Type constructors representing an instance of a type family. Parameters:
374 -- 1) The type family in question
376 -- 2) Instance types; free variables are the 'tyConTyVars'
377 -- of the current 'TyCon' (not the family one). INVARIANT:
378 -- the number of types matches the arity of the family 'TyCon'
380 -- 3) A 'CoercionTyCon' identifying the representation
381 -- type with the type instance family
385 TyCon -- c.f. Note [Newtype coercions]
388 -- E.g. data intance T [a] = ...
389 -- gives a representation tycon:
391 -- axiom co a :: T [a] ~ :R7T a
392 -- with :R7T's algTcParent = FamilyTyCon T [a] co
394 -- | Checks the invariants of a 'TyConParent' given the appropriate type class name, if any
395 okParent :: Name -> TyConParent -> Bool
396 okParent _ NoParentTyCon = True
397 okParent tc_name (ClassTyCon cls) = tyConName (classTyCon cls) == tc_name
398 okParent _ (FamilyTyCon fam_tc tys _co_tc) = tyConArity fam_tc == length tys
402 -- | Information pertaining to the expansion of a type synonym (@type@)
404 = OpenSynTyCon -- e.g. type family F x y :: * -> *
405 Kind -- Kind of the "rhs"; ie *excluding type indices*
406 -- In the example, the kind is (*->*)
407 AssocFamilyPermutation
409 | SynonymTyCon Type -- ^ The synonym mentions head type variables. It acts as a
410 -- template for the expansion when the 'TyCon' is applied to some
414 Note [Newtype coercions]
415 ~~~~~~~~~~~~~~~~~~~~~~~~
416 The NewTyCon field nt_co is a a TyCon (a coercion constructor in fact)
417 which is used for coercing from the representation type of the
418 newtype, to the newtype itself. For example,
420 newtype T a = MkT (a -> a)
422 the NewTyCon for T will contain nt_co = CoT where CoT t : T t ~ t ->
423 t. This TyCon is a CoercionTyCon, so it does not have a kind on its
424 own; it basically has its own typing rule for the fully-applied
425 version. If the newtype T has k type variables then CoT has arity at
426 most k. In the case that the right hand side is a type application
427 ending with the same type variables as the left hand side, we
428 "eta-contract" the coercion. So if we had
430 newtype S a = MkT [a]
432 then we would generate the arity 0 coercion CoS : S ~ []. The
433 primary reason we do this is to make newtype deriving cleaner.
435 In the paper we'd write
436 axiom CoT : (forall t. T t) ~ (forall t. [t])
437 and then when we used CoT at a particular type, s, we'd say
439 which encodes as (TyConApp instCoercionTyCon [TyConApp CoT [], s])
441 But in GHC we instead make CoT into a new piece of type syntax, CoercionTyCon,
442 (like instCoercionTyCon, symCoercionTyCon etc), which must always
443 be saturated, but which encodes as
445 In the vocabulary of the paper it's as if we had axiom declarations
447 axiom CoT t : T t ~ [t]
452 newtype Parser m a = MkParser (Foogle m a)
453 Are these two types equal (to Core)?
456 Well, yes. But to see that easily we eta-reduce the RHS type of
457 Parser, in this case to ([], Froogle), so that even unsaturated applications
458 of Parser will work right. This eta reduction is done when the type
459 constructor is built, and cached in NewTyCon. The cached field is
460 only used in coreExpandTyCon_maybe.
462 Here's an example that I think showed up in practice
464 newtype T a = MkT [a]
465 newtype Foo m = MkFoo (forall a. m a -> Int)
471 w2 = MkFoo (\(MkT x) -> case w1 of MkFoo f -> f x)
473 After desugaring, and discarding the data constructors for the newtypes,
477 And now Lint complains unless Foo T == Foo [], and that requires T==[]
479 This point carries over to the newtype coercion, because we need to
481 w2 = w1 `cast` Foo CoT
483 so the coercion tycon CoT must have
488 Note [Indexed data types] (aka data type families)
489 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
490 See also Note [Wrappers for data instance tycons] in MkId.lhs
495 data instance T (b,c) where
496 T1 :: b -> c -> T (b,c)
499 * T is the "family TyCon"
501 * We make "representation TyCon" :R1T, thus:
503 T1 :: forall b c. b -> c -> :R1T b c
505 * It has a top-level coercion connecting it to the family TyCon
507 axiom :Co:R1T b c : T (b,c) ~ :R1T b c
509 * The data contructor T1 has a wrapper (which is what the source-level
512 $WT1 :: forall b c. b -> c -> T (b,c)
513 $WT1 b c (x::b) (y::c) = T1 b c x y `cast` sym (:Co:R1T b c)
515 * The representation TyCon :R1T has an AlgTyConParent of
517 FamilyTyCon T [(b,c)] :Co:R1T
521 %************************************************************************
525 %************************************************************************
527 A PrimRep is somewhat similar to a CgRep (see codeGen/SMRep) and a
528 MachRep (see cmm/CmmExpr), although each of these types has a distinct
529 and clearly defined purpose:
531 - A PrimRep is a CgRep + information about signedness + information
532 about primitive pointers (AddrRep). Signedness and primitive
533 pointers are required when passing a primitive type to a foreign
534 function, but aren't needed for call/return conventions of Haskell
537 - A MachRep is a basic machine type (non-void, doesn't contain
538 information on pointerhood or signedness, but contains some
539 reps that don't have corresponding Haskell types).
542 -- | A 'PrimRep' is an abstraction of a type. It contains information that
543 -- the code generator needs in order to pass arguments, return results,
544 -- and store values of this type.
548 | IntRep -- ^ Signed, word-sized value
549 | WordRep -- ^ Unsigned, word-sized value
550 | Int64Rep -- ^ Signed, 64 bit value (with 32-bit words only)
551 | Word64Rep -- ^ Unsigned, 64 bit value (with 32-bit words only)
552 | AddrRep -- ^ A pointer, but /not/ to a Haskell value (use 'PtrRep')
557 instance Outputable PrimRep where
558 ppr r = text (show r)
560 -- | Find the size of a 'PrimRep', in words
561 primRepSizeW :: PrimRep -> Int
562 primRepSizeW IntRep = 1
563 primRepSizeW WordRep = 1
564 primRepSizeW Int64Rep = wORD64_SIZE `quot` wORD_SIZE
565 primRepSizeW Word64Rep= wORD64_SIZE `quot` wORD_SIZE
566 primRepSizeW FloatRep = 1 -- NB. might not take a full word
567 primRepSizeW DoubleRep= dOUBLE_SIZE `quot` wORD_SIZE
568 primRepSizeW AddrRep = 1
569 primRepSizeW PtrRep = 1
570 primRepSizeW VoidRep = 0
573 %************************************************************************
575 \subsection{TyCon Construction}
577 %************************************************************************
579 Note: the TyCon constructors all take a Kind as one argument, even though
580 they could, in principle, work out their Kind from their other arguments.
581 But to do so they need functions from Types, and that makes a nasty
582 module mutual-recursion. And they aren't called from many places.
583 So we compromise, and move their Kind calculation to the call site.
586 -- | Given the name of the function type constructor and it's kind, create the
587 -- corresponding 'TyCon'. It is reccomended to use 'TypeRep.funTyCon' if you want
588 -- this functionality
589 mkFunTyCon :: Name -> Kind -> TyCon
592 tyConUnique = nameUnique name,
598 -- | This is the making of an algebraic 'TyCon'. Notably, you have to pass in the generic (in the -XGenerics sense)
599 -- information about the type constructor - you can get hold of it easily (see Generics module)
601 -> Kind -- ^ Kind of the resulting 'TyCon'
602 -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'. Arity is inferred from the length of this list
603 -> [PredType] -- ^ Stupid theta: see 'algTcStupidTheta'
604 -> AlgTyConRhs -- ^ Information about dat aconstructors
606 -> RecFlag -- ^ Is the 'TyCon' recursive?
607 -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
608 -> Bool -- ^ Was the 'TyCon' declared with GADT syntax?
610 mkAlgTyCon name kind tyvars stupid rhs parent is_rec gen_info gadt_syn
613 tyConUnique = nameUnique name,
615 tyConArity = length tyvars,
616 tyConTyVars = tyvars,
617 algTcStupidTheta = stupid,
619 algTcParent = ASSERT( okParent name parent ) parent,
621 algTcGadtSyntax = gadt_syn,
622 hasGenerics = gen_info
625 -- | Simpler specialization of 'mkAlgTyCon' for classes
626 mkClassTyCon :: Name -> Kind -> [TyVar] -> AlgTyConRhs -> Class -> RecFlag -> TyCon
627 mkClassTyCon name kind tyvars rhs clas is_rec =
628 mkAlgTyCon name kind tyvars [] rhs (ClassTyCon clas) is_rec False False
631 -> Kind -- ^ Kind of the resulting 'TyCon'
632 -> Arity -- ^ Arity of the tuple
633 -> [TyVar] -- ^ 'TyVar's scoped over: see 'tyConTyVars'
635 -> Boxity -- ^ Whether the tuple is boxed or unboxed
636 -> Bool -- ^ Does it have generic functions? See 'hasGenerics'
638 mkTupleTyCon name kind arity tyvars con boxed gen_info
640 tyConUnique = nameUnique name,
645 tyConTyVars = tyvars,
647 hasGenerics = gen_info
650 -- ^ Foreign-imported (.NET) type constructors are represented
651 -- as primitive, but /lifted/, 'TyCons' for now. They are lifted
652 -- because the Haskell type @T@ representing the (foreign) .NET
653 -- type @T@ is actually implemented (in ILX) as a @thunk<T>@
654 mkForeignTyCon :: Name
655 -> Maybe FastString -- ^ Name of the foreign imported thing, maybe
659 mkForeignTyCon name ext_name kind arity
662 tyConUnique = nameUnique name,
665 primTyConRep = PtrRep, -- they all do
667 tyConExtName = ext_name
671 -- | Create an unlifted primitive 'TyCon', such as @Int#@
672 mkPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
673 mkPrimTyCon name kind arity rep
674 = mkPrimTyCon' name kind arity rep True
676 -- | Kind constructors
677 mkKindTyCon :: Name -> Kind -> TyCon
678 mkKindTyCon name kind
679 = mkPrimTyCon' name kind 0 VoidRep True
681 -- | Create a lifted primitive 'TyCon' such as @RealWorld@
682 mkLiftedPrimTyCon :: Name -> Kind -> Arity -> PrimRep -> TyCon
683 mkLiftedPrimTyCon name kind arity rep
684 = mkPrimTyCon' name kind arity rep False
686 mkPrimTyCon' :: Name -> Kind -> Arity -> PrimRep -> Bool -> TyCon
687 mkPrimTyCon' name kind arity rep is_unlifted
690 tyConUnique = nameUnique name,
694 isUnLifted = is_unlifted,
695 tyConExtName = Nothing
698 -- | Create a type synonym 'TyCon'
699 mkSynTyCon :: Name -> Kind -> [TyVar] -> SynTyConRhs -> TyConParent -> TyCon
700 mkSynTyCon name kind tyvars rhs parent
703 tyConUnique = nameUnique name,
705 tyConArity = length tyvars,
706 tyConTyVars = tyvars,
711 -- | Create a coercion 'TyCon'
712 mkCoercionTyCon :: Name -> Arity
713 -> CoTyConKindChecker
715 mkCoercionTyCon name arity rule_fn
718 tyConUnique = nameUnique name,
721 coKindFun = \ ty co fail args ->
722 ASSERT2( length args == arity, ppr name )
723 rule_fn ty co fail args
729 mkAnyTyCon :: Name -> Kind -> TyCon
731 = AnyTyCon { tyConName = name,
733 tyConUnique = nameUnique name }
735 -- | Create a super-kind 'TyCon'
736 mkSuperKindTyCon :: Name -> TyCon -- Super kinds always have arity zero
737 mkSuperKindTyCon name
740 tyConUnique = nameUnique name
745 isFunTyCon :: TyCon -> Bool
746 isFunTyCon (FunTyCon {}) = True
749 -- | Test if the 'TyCon' is algebraic but abstract (invisible data constructors)
750 isAbstractTyCon :: TyCon -> Bool
751 isAbstractTyCon (AlgTyCon { algTcRhs = AbstractTyCon }) = True
752 isAbstractTyCon _ = False
754 -- | Make an algebraic 'TyCon' abstract. Panics if the supplied 'TyCon' is not algebraic
755 makeTyConAbstract :: TyCon -> TyCon
756 makeTyConAbstract tc@(AlgTyCon {}) = tc { algTcRhs = AbstractTyCon }
757 makeTyConAbstract tc = pprPanic "makeTyConAbstract" (ppr tc)
759 -- | Does this 'TyCon' represent something that cannot be defined in Haskell?
760 isPrimTyCon :: TyCon -> Bool
761 isPrimTyCon (PrimTyCon {}) = True
762 isPrimTyCon _ = False
764 -- | Is this 'TyCon' unlifted (i.e. cannot contain bottom)? Note that this can only
765 -- be true for primitive and unboxed-tuple 'TyCon's
766 isUnLiftedTyCon :: TyCon -> Bool
767 isUnLiftedTyCon (PrimTyCon {isUnLifted = is_unlifted}) = is_unlifted
768 isUnLiftedTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
769 isUnLiftedTyCon _ = False
771 -- | Returns @True@ if the supplied 'TyCon' resulted from either a @data@ or @newtype@ declaration
772 isAlgTyCon :: TyCon -> Bool
773 isAlgTyCon (AlgTyCon {}) = True
774 isAlgTyCon (TupleTyCon {}) = True
777 isDataTyCon :: TyCon -> Bool
778 -- ^ Returns @True@ for data types that are /definitely/ represented by
779 -- heap-allocated constructors. These are scrutinised by Core-level
780 -- @case@ expressions, and they get info tables allocated for them.
782 -- Generally, the function will be true for all @data@ types and false
783 -- for @newtype@s, unboxed tuples and type family 'TyCon's. But it is
784 -- not guarenteed to return @True@ in all cases that it could.
786 -- NB: for a data type family, only the /instance/ 'TyCon's
787 -- get an info table. The family declaration 'TyCon' does not
788 isDataTyCon (AlgTyCon {algTcRhs = rhs})
790 OpenTyCon {} -> False
793 AbstractTyCon -> False -- We don't know, so return False
794 isDataTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
795 isDataTyCon _ = False
797 -- | Is this 'TyCon' that for a @newtype@
798 isNewTyCon :: TyCon -> Bool
799 isNewTyCon (AlgTyCon {algTcRhs = NewTyCon {}}) = True
802 tyConHasKind :: TyCon -> Bool
803 tyConHasKind (SuperKindTyCon {}) = False
804 tyConHasKind (CoercionTyCon {}) = False
805 tyConHasKind _ = True
807 -- | Take a 'TyCon' apart into the 'TyVar's it scopes over, the 'Type' it expands
808 -- into, and (possibly) a coercion from the representation type to the @newtype@.
809 -- Returns @Nothing@ if this is not possible.
810 unwrapNewTyCon_maybe :: TyCon -> Maybe ([TyVar], Type, Maybe TyCon)
811 unwrapNewTyCon_maybe (AlgTyCon { tyConTyVars = tvs,
812 algTcRhs = NewTyCon { nt_co = mb_co,
814 = Just (tvs, rhs, mb_co)
815 unwrapNewTyCon_maybe _ = Nothing
817 isProductTyCon :: TyCon -> Bool
818 -- | A /product/ 'TyCon' must both:
820 -- 1. Have /one/ constructor
822 -- 2. /Not/ be existential
824 -- However other than this there are few restrictions: they may be @data@ or @newtype@
825 -- 'TyCon's of any boxity and may even be recursive.
826 isProductTyCon tc@(AlgTyCon {}) = case algTcRhs tc of
827 DataTyCon{ data_cons = [data_con] }
828 -> isVanillaDataCon data_con
831 isProductTyCon (TupleTyCon {}) = True
832 isProductTyCon _ = False
834 -- | Is this a 'TyCon' representing a type synonym (@type@)?
835 isSynTyCon :: TyCon -> Bool
836 isSynTyCon (SynTyCon {}) = True
839 -- As for newtypes, it is in some contexts important to distinguish between
840 -- closed synonyms and synonym families, as synonym families have no unique
841 -- right hand side to which a synonym family application can expand.
844 -- | Is this a synonym 'TyCon' that can have no further instances appear?
845 isClosedSynTyCon :: TyCon -> Bool
846 isClosedSynTyCon tycon = isSynTyCon tycon && not (isOpenTyCon tycon)
848 -- | Is this a synonym 'TyCon' that can have may have further instances appear?
849 isOpenSynTyCon :: TyCon -> Bool
850 isOpenSynTyCon tycon = isSynTyCon tycon && isOpenTyCon tycon
852 isDecomposableTyCon :: TyCon -> Bool
853 -- True iff we can deocmpose (T a b c) into ((T a b) c)
854 -- Specifically NOT true of synonyms (open and otherwise) and coercions
855 isDecomposableTyCon (SynTyCon {}) = False
856 isDecomposableTyCon (CoercionTyCon {}) = False
857 isDecomposableTyCon _other = True
859 -- | Is this an algebraic 'TyCon' declared with the GADT syntax?
860 isGadtSyntaxTyCon :: TyCon -> Bool
861 isGadtSyntaxTyCon (AlgTyCon { algTcGadtSyntax = res }) = res
862 isGadtSyntaxTyCon _ = False
864 -- | Is this an algebraic 'TyCon' which is just an enumeration of values?
865 isEnumerationTyCon :: TyCon -> Bool
866 isEnumerationTyCon (AlgTyCon {algTcRhs = DataTyCon { is_enum = res }}) = res
867 isEnumerationTyCon (TupleTyCon {tyConArity = arity}) = arity == 0
868 isEnumerationTyCon _ = False
870 -- | Is this a 'TyCon', synonym or otherwise, that may have further instances appear?
871 isOpenTyCon :: TyCon -> Bool
872 isOpenTyCon (SynTyCon {synTcRhs = OpenSynTyCon {}}) = True
873 isOpenTyCon (AlgTyCon {algTcRhs = OpenTyCon {}}) = True
874 isOpenTyCon _ = False
876 -- | Injective 'TyCon's can be decomposed, so that
877 -- T ty1 ~ T ty2 => ty1 ~ ty2
878 isInjectiveTyCon :: TyCon -> Bool
879 isInjectiveTyCon tc = not (isSynTyCon tc)
880 -- Ultimately we may have injective associated types
881 -- in which case this test will become more interesting
883 -- It'd be unusual to call isInjectiveTyCon on a regular H98
884 -- type synonym, because you should probably have expanded it first
885 -- But regardless, it's not injective!
887 -- | Extract the mapping from 'TyVar' indexes to indexes in the corresponding family
888 -- argument lists form an open 'TyCon' of any sort, if the given 'TyCon' is indeed
889 -- such a beast and that information is available
890 assocTyConArgPoss_maybe :: TyCon -> Maybe [Int]
891 assocTyConArgPoss_maybe (AlgTyCon {
892 algTcRhs = OpenTyCon {otArgPoss = poss}}) = poss
893 assocTyConArgPoss_maybe (SynTyCon { synTcRhs = OpenSynTyCon _ poss }) = poss
894 assocTyConArgPoss_maybe _ = Nothing
896 -- | Are we able to extract informationa 'TyVar' to class argument list
897 -- mappping from a given 'TyCon'?
898 isTyConAssoc :: TyCon -> Bool
899 isTyConAssoc = isJust . assocTyConArgPoss_maybe
901 -- | Set the AssocFamilyPermutation structure in an
902 -- associated data or type synonym. The [TyVar] are the
903 -- class type variables. Remember, the tyvars of an associated
904 -- data/type are a subset of the class tyvars; except that an
905 -- associated data type can have extra type variables at the
906 -- end (see Note [Avoid name clashes for associated data types] in TcHsType)
907 setTyConArgPoss :: [TyVar] -> TyCon -> TyCon
908 setTyConArgPoss clas_tvs tc
910 AlgTyCon { algTcRhs = rhs } -> tc { algTcRhs = rhs {otArgPoss = Just ps} }
911 SynTyCon { synTcRhs = OpenSynTyCon ki _ } -> tc { synTcRhs = OpenSynTyCon ki (Just ps) }
912 _ -> pprPanic "setTyConArgPoss" (ppr tc)
914 ps = catMaybes [tv `elemIndex` clas_tvs | tv <- tyConTyVars tc]
915 -- We will get Nothings for the "extra" type variables in an
916 -- associated data type
918 -- The unit tycon didn't used to be classed as a tuple tycon
919 -- but I thought that was silly so I've undone it
920 -- If it can't be for some reason, it should be a AlgTyCon
921 isTupleTyCon :: TyCon -> Bool
922 -- ^ Does this 'TyCon' represent a tuple?
924 -- NB: when compiling @Data.Tuple@, the tycons won't reply @True@ to
925 -- 'isTupleTyCon', becuase they are built as 'AlgTyCons'. However they
926 -- get spat into the interface file as tuple tycons, so I don't think
928 isTupleTyCon (TupleTyCon {}) = True
929 isTupleTyCon _ = False
931 -- | Is this the 'TyCon' for an unboxed tuple?
932 isUnboxedTupleTyCon :: TyCon -> Bool
933 isUnboxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = not (isBoxed boxity)
934 isUnboxedTupleTyCon _ = False
936 -- | Is this the 'TyCon' for a boxed tuple?
937 isBoxedTupleTyCon :: TyCon -> Bool
938 isBoxedTupleTyCon (TupleTyCon {tyConBoxed = boxity}) = isBoxed boxity
939 isBoxedTupleTyCon _ = False
941 -- | Extract the boxity of the given 'TyCon', if it is a 'TupleTyCon'.
943 tupleTyConBoxity :: TyCon -> Boxity
944 tupleTyConBoxity tc = tyConBoxed tc
946 -- | Is this a recursive 'TyCon'?
947 isRecursiveTyCon :: TyCon -> Bool
948 isRecursiveTyCon (AlgTyCon {algTcRec = Recursive}) = True
949 isRecursiveTyCon _ = False
951 -- | Did this 'TyCon' originate from type-checking a .h*-boot file?
952 isHiBootTyCon :: TyCon -> Bool
953 -- Used for knot-tying in hi-boot files
954 isHiBootTyCon (AlgTyCon {algTcRhs = AbstractTyCon}) = True
955 isHiBootTyCon _ = False
957 -- | Is this the 'TyCon' of a foreign-imported type constructor?
958 isForeignTyCon :: TyCon -> Bool
959 isForeignTyCon (PrimTyCon {tyConExtName = Just _}) = True
960 isForeignTyCon _ = False
962 -- | Is this a super-kind 'TyCon'?
963 isSuperKindTyCon :: TyCon -> Bool
964 isSuperKindTyCon (SuperKindTyCon {}) = True
965 isSuperKindTyCon _ = False
967 -- | Is this an AnyTyCon?
968 isAnyTyCon :: TyCon -> Bool
969 isAnyTyCon (AnyTyCon {}) = True
972 -- | Attempt to pull a 'TyCon' apart into the arity and 'coKindFun' of
973 -- a coercion 'TyCon'. Returns @Nothing@ if the 'TyCon' is not of the
975 isCoercionTyCon_maybe :: Monad m => TyCon -> Maybe (Arity, CoTyConKindCheckerFun m)
976 isCoercionTyCon_maybe (CoercionTyCon {tyConArity = ar, coKindFun = rule})
978 isCoercionTyCon_maybe _ = Nothing
980 -- | Is this a 'TyCon' that represents a coercion?
981 isCoercionTyCon :: TyCon -> Bool
982 isCoercionTyCon (CoercionTyCon {}) = True
983 isCoercionTyCon _ = False
985 -- | Identifies implicit tycons that, in particular, do not go into interface
986 -- files (because they are implicitly reconstructed when the interface is
991 -- * Associated families are implicit, as they are re-constructed from
992 -- the class declaration in which they reside, and
994 -- * Family instances are /not/ implicit as they represent the instance body
995 -- (similar to a @dfun@ does that for a class instance).
996 isImplicitTyCon :: TyCon -> Bool
997 isImplicitTyCon tycon | isTyConAssoc tycon = True
998 | isSynTyCon tycon = False
999 | isAlgTyCon tycon = isClassTyCon tycon ||
1001 isImplicitTyCon _other = True
1002 -- catches: FunTyCon, PrimTyCon,
1003 -- CoercionTyCon, SuperKindTyCon
1007 -----------------------------------------------
1008 -- Expand type-constructor applications
1009 -----------------------------------------------
1012 tcExpandTyCon_maybe, coreExpandTyCon_maybe
1014 -> [Type] -- ^ Arguments to 'TyCon'
1015 -> Maybe ([(TyVar,Type)],
1017 [Type]) -- ^ Returns a 'TyVar' substitution, the body type
1018 -- of the synonym (not yet substituted) and any arguments
1019 -- remaining from the application
1021 -- ^ Used to create the view the /typechecker/ has on 'TyCon's. We expand (closed) synonyms only, cf. 'coreExpandTyCon_maybe'
1022 tcExpandTyCon_maybe (SynTyCon {tyConTyVars = tvs,
1023 synTcRhs = SynonymTyCon rhs }) tys
1024 = expand tvs rhs tys
1025 tcExpandTyCon_maybe _ _ = Nothing
1029 -- ^ Used to create the view /Core/ has on 'TyCon's. We expand not only closed synonyms like 'tcExpandTyCon_maybe',
1030 -- but also non-recursive @newtype@s
1031 coreExpandTyCon_maybe (AlgTyCon {
1032 algTcRhs = NewTyCon { nt_etad_rhs = etad_rhs, nt_co = Nothing }}) tys
1033 = case etad_rhs of -- Don't do this in the pattern match, lest we accidentally
1034 -- match the etad_rhs of a *recursive* newtype
1035 (tvs,rhs) -> expand tvs rhs tys
1037 coreExpandTyCon_maybe tycon tys = tcExpandTyCon_maybe tycon tys
1041 expand :: [TyVar] -> Type -- Template
1043 -> Maybe ([(TyVar,Type)], Type, [Type]) -- Expansion
1045 = case n_tvs `compare` length tys of
1046 LT -> Just (tvs `zip` tys, rhs, drop n_tvs tys)
1047 EQ -> Just (tvs `zip` tys, rhs, [])
1054 -- | Does this 'TyCon' have any generic to\/from functions available? See also 'hasGenerics'
1055 tyConHasGenerics :: TyCon -> Bool
1056 tyConHasGenerics (AlgTyCon {hasGenerics = hg}) = hg
1057 tyConHasGenerics (TupleTyCon {hasGenerics = hg}) = hg
1058 tyConHasGenerics _ = False -- Synonyms
1060 tyConKind :: TyCon -> Kind
1061 tyConKind (FunTyCon { tc_kind = k }) = k
1062 tyConKind (AlgTyCon { tc_kind = k }) = k
1063 tyConKind (TupleTyCon { tc_kind = k }) = k
1064 tyConKind (SynTyCon { tc_kind = k }) = k
1065 tyConKind (PrimTyCon { tc_kind = k }) = k
1066 tyConKind (AnyTyCon { tc_kind = k }) = k
1067 tyConKind tc = pprPanic "tyConKind" (ppr tc)
1069 -- | As 'tyConDataCons_maybe', but returns the empty list of constructors if no constructors
1071 tyConDataCons :: TyCon -> [DataCon]
1072 -- It's convenient for tyConDataCons to return the
1073 -- empty list for type synonyms etc
1074 tyConDataCons tycon = tyConDataCons_maybe tycon `orElse` []
1076 -- | Determine the 'DataCon's originating from the given 'TyCon', if the 'TyCon' is the
1077 -- sort that can have any constructors (note: this does not include abstract algebraic types)
1078 tyConDataCons_maybe :: TyCon -> Maybe [DataCon]
1079 tyConDataCons_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = cons }}) = Just cons
1080 tyConDataCons_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = con }}) = Just [con]
1081 tyConDataCons_maybe (TupleTyCon {dataCon = con}) = Just [con]
1082 tyConDataCons_maybe _ = Nothing
1084 -- | Determine the number of value constructors a 'TyCon' has. Panics if the 'TyCon'
1085 -- is not algebraic or a tuple
1086 tyConFamilySize :: TyCon -> Int
1087 tyConFamilySize (AlgTyCon {algTcRhs = DataTyCon {data_cons = cons}}) =
1089 tyConFamilySize (AlgTyCon {algTcRhs = NewTyCon {}}) = 1
1090 tyConFamilySize (AlgTyCon {algTcRhs = OpenTyCon {}}) = 0
1091 tyConFamilySize (TupleTyCon {}) = 1
1092 tyConFamilySize other = pprPanic "tyConFamilySize:" (ppr other)
1094 -- | Extract an 'AlgTyConRhs' with information about data constructors from an algebraic or tuple
1095 -- 'TyCon'. Panics for any other sort of 'TyCon'
1096 algTyConRhs :: TyCon -> AlgTyConRhs
1097 algTyConRhs (AlgTyCon {algTcRhs = rhs}) = rhs
1098 algTyConRhs (TupleTyCon {dataCon = con, tyConArity = arity})
1099 = DataTyCon { data_cons = [con], is_enum = arity == 0 }
1100 algTyConRhs other = pprPanic "algTyConRhs" (ppr other)
1104 -- | Extract the bound type variables and type expansion of a type synonym 'TyCon'. Panics if the
1105 -- 'TyCon' is not a synonym
1106 newTyConRhs :: TyCon -> ([TyVar], Type)
1107 newTyConRhs (AlgTyCon {tyConTyVars = tvs, algTcRhs = NewTyCon { nt_rhs = rhs }}) = (tvs, rhs)
1108 newTyConRhs tycon = pprPanic "newTyConRhs" (ppr tycon)
1110 -- | Extract the bound type variables and type expansion of an eta-contracted type synonym 'TyCon'.
1111 -- Panics if the 'TyCon' is not a synonym
1112 newTyConEtadRhs :: TyCon -> ([TyVar], Type)
1113 newTyConEtadRhs (AlgTyCon {algTcRhs = NewTyCon { nt_etad_rhs = tvs_rhs }}) = tvs_rhs
1114 newTyConEtadRhs tycon = pprPanic "newTyConEtadRhs" (ppr tycon)
1116 -- | Extracts the @newtype@ coercion from such a 'TyCon', which can be used to construct something
1117 -- with the @newtype@s type from its representation type (right hand side). If the supplied 'TyCon'
1118 -- is not a @newtype@, returns @Nothing@
1119 newTyConCo_maybe :: TyCon -> Maybe TyCon
1120 newTyConCo_maybe (AlgTyCon {algTcRhs = NewTyCon { nt_co = co }}) = co
1121 newTyConCo_maybe _ = Nothing
1123 -- | Find the primitive representation of a 'TyCon'
1124 tyConPrimRep :: TyCon -> PrimRep
1125 tyConPrimRep (PrimTyCon {primTyConRep = rep}) = rep
1126 tyConPrimRep tc = ASSERT(not (isUnboxedTupleTyCon tc)) PtrRep
1130 -- | Find the \"stupid theta\" of the 'TyCon'. A \"stupid theta\" is the context to the left of
1131 -- an algebraic type declaration, e.g. @Eq a@ in the declaration @data Eq a => T a ...@
1132 tyConStupidTheta :: TyCon -> [PredType]
1133 tyConStupidTheta (AlgTyCon {algTcStupidTheta = stupid}) = stupid
1134 tyConStupidTheta (TupleTyCon {}) = []
1135 tyConStupidTheta tycon = pprPanic "tyConStupidTheta" (ppr tycon)
1139 -- | Extract the 'TyVar's bound by a type synonym and the corresponding (unsubstituted) right hand side.
1140 -- If the given 'TyCon' is not a type synonym, panics
1141 synTyConDefn :: TyCon -> ([TyVar], Type)
1142 synTyConDefn (SynTyCon {tyConTyVars = tyvars, synTcRhs = SynonymTyCon ty})
1144 synTyConDefn tycon = pprPanic "getSynTyConDefn" (ppr tycon)
1146 -- | Extract the information pertaining to the right hand side of a type synonym (@type@) declaration. Panics
1147 -- if the given 'TyCon' is not a type synonym
1148 synTyConRhs :: TyCon -> SynTyConRhs
1149 synTyConRhs (SynTyCon {synTcRhs = rhs}) = rhs
1150 synTyConRhs tc = pprPanic "synTyConRhs" (ppr tc)
1152 -- | Find the expansion of the type synonym represented by the given 'TyCon'. The free variables of this
1153 -- type will typically include those 'TyVar's bound by the 'TyCon'. Panics if the 'TyCon' is not that of
1155 synTyConType :: TyCon -> Type
1156 synTyConType tc = case synTcRhs tc of
1158 _ -> pprPanic "synTyConType" (ppr tc)
1160 -- | Find the 'Kind' of an open type synonym. Panics if the 'TyCon' is not an open type synonym
1161 synTyConResKind :: TyCon -> Kind
1162 synTyConResKind (SynTyCon {synTcRhs = OpenSynTyCon kind _}) = kind
1163 synTyConResKind tycon = pprPanic "synTyConResKind" (ppr tycon)
1167 -- | If the given 'TyCon' has a /single/ data constructor, i.e. it is a @data@ type with one
1168 -- alternative, a tuple type or a @newtype@ then that constructor is returned. If the 'TyCon'
1169 -- has more than one constructor, or represents a primitive or function type constructor then
1170 -- @Nothing@ is returned. In any other case, the function panics
1171 tyConSingleDataCon_maybe :: TyCon -> Maybe DataCon
1172 tyConSingleDataCon_maybe (TupleTyCon {dataCon = c}) = Just c
1173 tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = DataTyCon { data_cons = [c] }}) = Just c
1174 tyConSingleDataCon_maybe (AlgTyCon {algTcRhs = NewTyCon { data_con = c }}) = Just c
1175 tyConSingleDataCon_maybe _ = Nothing
1179 -- | Is this 'TyCon' that for a class instance?
1180 isClassTyCon :: TyCon -> Bool
1181 isClassTyCon (AlgTyCon {algTcParent = ClassTyCon _}) = True
1182 isClassTyCon _ = False
1184 -- | If this 'TyCon' is that for a class instance, return the class it is for.
1185 -- Otherwise returns @Nothing@
1186 tyConClass_maybe :: TyCon -> Maybe Class
1187 tyConClass_maybe (AlgTyCon {algTcParent = ClassTyCon clas}) = Just clas
1188 tyConClass_maybe _ = Nothing
1190 -- | Is this 'TyCon' that for a family instance, be that for a synonym or an
1191 -- algebraic family instance?
1192 isFamInstTyCon :: TyCon -> Bool
1193 isFamInstTyCon (AlgTyCon {algTcParent = FamilyTyCon _ _ _ }) = True
1194 isFamInstTyCon (SynTyCon {synTcParent = FamilyTyCon _ _ _ }) = True
1195 isFamInstTyCon _ = False
1197 -- | If this 'TyCon' is that of a family instance, return the family in question
1198 -- and the instance types. Otherwise, return @Nothing@
1199 tyConFamInst_maybe :: TyCon -> Maybe (TyCon, [Type])
1200 tyConFamInst_maybe (AlgTyCon {algTcParent = FamilyTyCon fam instTys _}) =
1202 tyConFamInst_maybe (SynTyCon {synTcParent = FamilyTyCon fam instTys _}) =
1204 tyConFamInst_maybe _ =
1207 -- | If this 'TyCon' is that of a family instance, return a 'TyCon' which represents
1208 -- a coercion identifying the representation type with the type instance family.
1209 -- Otherwise, return @Nothing@
1210 tyConFamilyCoercion_maybe :: TyCon -> Maybe TyCon
1211 tyConFamilyCoercion_maybe (AlgTyCon {algTcParent = FamilyTyCon _ _ coe}) =
1213 tyConFamilyCoercion_maybe (SynTyCon {synTcParent = FamilyTyCon _ _ coe}) =
1215 tyConFamilyCoercion_maybe _ =
1220 %************************************************************************
1222 \subsection[TyCon-instances]{Instance declarations for @TyCon@}
1224 %************************************************************************
1226 @TyCon@s are compared by comparing their @Unique@s.
1228 The strictness analyser needs @Ord@. It is a lexicographic order with
1229 the property @(a<=b) || (b<=a)@.
1232 instance Eq TyCon where
1233 a == b = case (a `compare` b) of { EQ -> True; _ -> False }
1234 a /= b = case (a `compare` b) of { EQ -> False; _ -> True }
1236 instance Ord TyCon where
1237 a <= b = case (a `compare` b) of { LT -> True; EQ -> True; GT -> False }
1238 a < b = case (a `compare` b) of { LT -> True; EQ -> False; GT -> False }
1239 a >= b = case (a `compare` b) of { LT -> False; EQ -> True; GT -> True }
1240 a > b = case (a `compare` b) of { LT -> False; EQ -> False; GT -> True }
1241 compare a b = getUnique a `compare` getUnique b
1243 instance Uniquable TyCon where
1244 getUnique tc = tyConUnique tc
1246 instance Outputable TyCon where
1247 ppr tc = ppr (getName tc)
1249 instance NamedThing TyCon where