{-# LANGUAGE PatternGuards #-}
-----------------------------------------------------------------------------
-- |
-- Module : Haddock.Convert
-- Copyright : (c) Isaac Dupree 2009,
-- License : BSD-like
--
-- Maintainer : haddock@projects.haskell.org
-- Stability : experimental
-- Portability : portable
--
-- Conversion between TyThing and HsDecl. This functionality may be moved into
-- GHC at some point.
-----------------------------------------------------------------------------
module Haddock.Convert where
-- Some other functions turned out to be useful for converting
-- instance heads, which aren't TyThings, so just export everything.
import HsSyn
import TcType ( tcSplitTyConApp_maybe, tcSplitSigmaTy )
import TypeRep
import Kind ( splitKindFunTys, synTyConResKind )
import Name
import Var
import Class
import TyCon
import DataCon
import BasicTypes ( TupleSort(..) )
import TysPrim ( alphaTyVars )
import TysWiredIn ( listTyConName, eqTyCon )
import Bag ( emptyBag )
import SrcLoc ( Located, noLoc, unLoc )
-- the main function here! yay!
tyThingToLHsDecl :: TyThing -> LHsDecl Name
tyThingToLHsDecl t = noLoc $ case t of
-- ids (functions and zero-argument a.k.a. CAFs) get a type signature.
-- Including built-in functions like seq.
-- foreign-imported functions could be represented with ForD
-- instead of SigD if we wanted...
--
-- in a future code version we could turn idVarDetails = foreign-call
-- into a ForD instead of a SigD if we wanted. Haddock doesn't
-- need to care.
AnId i -> SigD (synifyIdSig ImplicitizeForAll i)
-- type-constructors (e.g. Maybe) are complicated, put the definition
-- later in the file (also it's used for class associated-types too.)
ATyCon tc
| Just cl <- tyConClass_maybe tc -- classes are just a little tedious
-> TyClD $ ClassDecl
(synifyCtx (classSCTheta cl))
(synifyName cl)
(synifyTyVars (classTyVars cl))
(map (\ (l,r) -> noLoc
(map getName l, map getName r) ) $
snd $ classTvsFds cl)
(map (noLoc . synifyIdSig DeleteTopLevelQuantification)
(classMethods cl))
emptyBag --ignore default method definitions, they don't affect signature
-- class associated-types are a subset of TyCon:
[noLoc (synifyTyCon at_tc) | (at_tc, _) <- classATItems cl]
[] --ignore associated type defaults
[] --we don't have any docs at this point
| otherwise
-> TyClD (synifyTyCon tc)
-- type-constructors (e.g. Maybe) are complicated, put the definition
-- later in the file (also it's used for class associated-types too.)
ACoAxiom ax -> TyClD (synifyAxiom ax)
-- a data-constructor alone just gets rendered as a function:
ADataCon dc -> SigD (TypeSig [synifyName dc]
(synifyType ImplicitizeForAll (dataConUserType dc)))
synifyATDefault :: TyCon -> LTyClDecl Name
synifyATDefault tc = noLoc (synifyAxiom ax)
where Just ax = tyConFamilyCoercion_maybe tc
synifyAxiom :: CoAxiom -> TyClDecl Name
synifyAxiom (CoAxiom { co_ax_tvs = tvs, co_ax_lhs = lhs, co_ax_rhs = rhs })
| Just (tc, args) <- tcSplitTyConApp_maybe lhs
= let name = synifyName tc
tyvars = synifyTyVars tvs
typats = map (synifyType WithinType) args
hs_rhs_ty = synifyType WithinType rhs
in TySynonym name tyvars (Just typats) hs_rhs_ty
| otherwise
= error "synifyAxiom"
synifyTyCon :: TyCon -> TyClDecl Name
synifyTyCon tc
| isFunTyCon tc || isPrimTyCon tc =
TyData
-- arbitrary lie, they are neither algebraic data nor newtype:
DataType
-- no built-in type has any stupidTheta:
(noLoc [])
(synifyName tc)
-- tyConTyVars doesn't work on fun/prim, but we can make them up:
(zipWith
(\fakeTyVar realKind -> noLoc $
KindedTyVar (getName fakeTyVar) (synifyKind realKind) placeHolderKind)
alphaTyVars --a, b, c... which are unfortunately all kind *
(fst . splitKindFunTys $ tyConKind tc)
)
-- assume primitive types aren't members of data/newtype families:
Nothing
-- we have their kind accurately:
(Just (synifyKind (tyConKind tc)))
-- no algebraic constructors:
[]
-- "deriving" needn't be specified:
Nothing
| isSynFamilyTyCon tc =
case synTyConRhs tc of
SynFamilyTyCon ->
TyFamily TypeFamily (synifyName tc) (synifyTyVars (tyConTyVars tc))
(Just (synifyKind (synTyConResKind tc))) -- placeHolderKind
_ -> error "synifyTyCon: impossible open type synonym?"
| isDataFamilyTyCon tc = --(why no "isOpenAlgTyCon"?)
case algTyConRhs tc of
DataFamilyTyCon ->
TyFamily DataFamily (synifyName tc) (synifyTyVars (tyConTyVars tc))
Nothing --always kind '*'
-- placeHolderKind
_ -> error "synifyTyCon: impossible open data type?"
| otherwise =
-- (closed) type, newtype, and data
let
-- alg_ only applies to newtype/data
-- syn_ only applies to type
-- others apply to both
alg_nd = if isNewTyCon tc then NewType else DataType
alg_ctx = synifyCtx (tyConStupidTheta tc)
name = synifyName tc
tyvars = synifyTyVars (tyConTyVars tc)
typats = case tyConFamInst_maybe tc of
Nothing -> Nothing
Just (_, indexes) -> Just (map (synifyType WithinType) indexes)
alg_kindSig = Just (tyConKind tc)
-- The data constructors.
--
-- Any data-constructors not exported from the module that *defines* the
-- type will not (cannot) be included.
--
-- Very simple constructors, Haskell98 with no existentials or anything,
-- probably look nicer in non-GADT syntax. In source code, all constructors
-- must be declared with the same (GADT vs. not) syntax, and it probably
-- is less confusing to follow that principle for the documentation as well.
--
-- There is no sensible infix-representation for GADT-syntax constructor
-- declarations. They cannot be made in source code, but we could end up
-- with some here in the case where some constructors use existentials.
-- That seems like an acceptable compromise (they'll just be documented
-- in prefix position), since, otherwise, the logic (at best) gets much more
-- complicated. (would use dataConIsInfix.)
alg_use_gadt_syntax = any (not . isVanillaDataCon) (tyConDataCons tc)
alg_cons = map (synifyDataCon alg_use_gadt_syntax) (tyConDataCons tc)
-- "deriving" doesn't affect the signature, no need to specify any.
alg_deriv = Nothing
syn_type = synifyType WithinType (synTyConType tc)
in if isSynTyCon tc
then TySynonym name tyvars typats syn_type
else TyData alg_nd alg_ctx name tyvars typats (fmap synifyKind alg_kindSig) alg_cons alg_deriv
-- User beware: it is your responsibility to pass True (use_gadt_syntax)
-- for any constructor that would be misrepresented by omitting its
-- result-type.
-- But you might want pass False in simple enough cases,
-- if you think it looks better.
synifyDataCon :: Bool -> DataCon -> LConDecl Name
synifyDataCon use_gadt_syntax dc = noLoc $
let
-- dataConIsInfix allegedly tells us whether it was declared with
-- infix *syntax*.
use_infix_syntax = dataConIsInfix dc
use_named_field_syntax = not (null field_tys)
name = synifyName dc
-- con_qvars means a different thing depending on gadt-syntax
(univ_tvs, ex_tvs, _eq_spec, theta, arg_tys, res_ty) = dataConFullSig dc
qvars = if use_gadt_syntax
then synifyTyVars (univ_tvs ++ ex_tvs)
else synifyTyVars ex_tvs
-- skip any EqTheta, use 'orig'inal syntax
ctx = synifyCtx theta
linear_tys = zipWith (\ty bang ->
let tySyn = synifyType WithinType ty
in case bang of
HsUnpackFailed -> noLoc $ HsBangTy HsStrict tySyn
HsNoBang -> tySyn
-- HsNoBang never appears, it's implied instead.
_ -> noLoc $ HsBangTy bang tySyn
)
arg_tys (dataConStrictMarks dc)
field_tys = zipWith (\field synTy -> ConDeclField
(synifyName field) synTy Nothing)
(dataConFieldLabels dc) linear_tys
hs_arg_tys = case (use_named_field_syntax, use_infix_syntax) of
(True,True) -> error "synifyDataCon: contradiction!"
(True,False) -> RecCon field_tys
(False,False) -> PrefixCon linear_tys
(False,True) -> case linear_tys of
[a,b] -> InfixCon a b
_ -> error "synifyDataCon: infix with non-2 args?"
hs_res_ty = if use_gadt_syntax
then ResTyGADT (synifyType WithinType res_ty)
else ResTyH98
-- finally we get synifyDataCon's result!
in ConDecl name Implicit{-we don't know nor care-}
qvars ctx hs_arg_tys hs_res_ty Nothing
False --we don't want any "deprecated GADT syntax" warnings!
synifyName :: NamedThing n => n -> Located Name
synifyName = noLoc . getName
synifyIdSig :: SynifyTypeState -> Id -> Sig Name
synifyIdSig s i = TypeSig [synifyName i] (synifyType s (varType i))
synifyCtx :: [PredType] -> LHsContext Name
synifyCtx = noLoc . map (synifyType WithinType)
synifyTyVars :: [TyVar] -> [LHsTyVarBndr Name]
synifyTyVars = map synifyTyVar
where
synifyTyVar tv = noLoc $ let
kind = tyVarKind tv
name = getName tv
in if isLiftedTypeKind kind
then UserTyVar name placeHolderKind
else KindedTyVar name (synifyKind kind) placeHolderKind
--states of what to do with foralls:
data SynifyTypeState
= WithinType
-- ^ normal situation. This is the safe one to use if you don't
-- quite understand what's going on.
| ImplicitizeForAll
-- ^ beginning of a function definition, in which, to make it look
-- less ugly, those rank-1 foralls are made implicit.
| DeleteTopLevelQuantification
-- ^ because in class methods the context is added to the type
-- (e.g. adding @forall a. Num a =>@ to @(+) :: a -> a -> a@)
-- which is rather sensible,
-- but we want to restore things to the source-syntax situation where
-- the defining class gets to quantify all its functions for free!
synifyType :: SynifyTypeState -> Type -> LHsType Name
synifyType _ (TyVarTy tv) = noLoc $ HsTyVar (getName tv)
synifyType _ (TyConApp tc tys)
-- Use non-prefix tuple syntax where possible, because it looks nicer.
| isTupleTyCon tc, tyConArity tc == length tys =
noLoc $ HsTupleTy (case tupleTyConSort tc of
BoxedTuple -> HsBoxedTuple
ConstraintTuple -> HsConstraintTuple
UnboxedTuple -> HsUnboxedTuple)
(map (synifyType WithinType) tys)
-- ditto for lists
| getName tc == listTyConName, [ty] <- tys =
noLoc $ HsListTy (synifyType WithinType ty)
-- ditto for implicit parameter tycons
| Just ip <- tyConIP_maybe tc
, [ty] <- tys
= noLoc $ HsIParamTy ip (synifyType WithinType ty)
-- and equalities
| tc == eqTyCon
, [ty1, ty2] <- tys
= noLoc $ HsEqTy (synifyType WithinType ty1) (synifyType WithinType ty2)
-- Most TyCons:
| otherwise =
foldl (\t1 t2 -> noLoc (HsAppTy t1 t2))
(noLoc $ HsTyVar (getName tc))
(map (synifyType WithinType) tys)
synifyType _ (AppTy t1 t2) = let
s1 = synifyType WithinType t1
s2 = synifyType WithinType t2
in noLoc $ HsAppTy s1 s2
synifyType _ (FunTy t1 t2) = let
s1 = synifyType WithinType t1
s2 = synifyType WithinType t2
in noLoc $ HsFunTy s1 s2
synifyType s forallty@(ForAllTy _tv _ty) =
let (tvs, ctx, tau) = tcSplitSigmaTy forallty
in case s of
DeleteTopLevelQuantification -> synifyType ImplicitizeForAll tau
_ -> let
forallPlicitness = case s of
WithinType -> Explicit
ImplicitizeForAll -> Implicit
_ -> error "synifyType: impossible case!!!"
sTvs = synifyTyVars tvs
sCtx = synifyCtx ctx
sTau = synifyType WithinType tau
in noLoc $
HsForAllTy forallPlicitness sTvs sCtx sTau
synifyKind :: Kind -> LHsKind Name
synifyKind = synifyType (error "synifyKind")
synifyInstHead :: ([TyVar], [PredType], Class, [Type]) ->
([HsType Name], Name, [HsType Name])
synifyInstHead (_, preds, cls, ts) =
( map (unLoc . synifyType WithinType) preds
, getName cls
, map (unLoc . synifyType WithinType) ts
)