path: root/compiler/iface/BuildTyCl.hs

{-
(c) The University of Glasgow 2006
(c) The GRASP/AQUA Project, Glasgow University, 1992-1998
-}

{-# LANGUAGE CPP #-}

module BuildTyCl (
        buildSynonymTyCon,
        buildFamilyTyCon,
        buildAlgTyCon,
        buildDataCon,
        buildPatSyn,
        TcMethInfo, buildClass,
        distinctAbstractTyConRhs, totallyAbstractTyConRhs,
        mkNewTyConRhs, mkDataTyConRhs,
        newImplicitBinder
    ) where

#include "HsVersions.h"

import IfaceEnv
import FamInstEnv( FamInstEnvs )
import TysWiredIn( isCTupleTyConName )
import DataCon
import PatSyn
import Var
import VarSet
import BasicTypes
import Name
import MkId
import Class
import TyCon
import Type
import Id
import Coercion
import TcType

import DynFlags
import TcRnMonad
import UniqSupply
import Util
import Outputable

------------------------------------------------------
buildSynonymTyCon :: Name -> [TyVar] -> [Role]
                  -> Type
                  -> Kind                   -- ^ Kind of the RHS
                  -> TyCon
buildSynonymTyCon tc_name tvs roles rhs rhs_kind
  = mkSynonymTyCon tc_name kind tvs roles rhs
  where kind = mkPiKinds tvs rhs_kind


buildFamilyTyCon :: Name         -- ^ Type family name
                 -> [TyVar]      -- ^ Type variables
                 -> Maybe Name   -- ^ Result variable name
                 -> FamTyConFlav -- ^ Open, closed or in a boot file?
                 -> Kind         -- ^ Kind of the RHS
                 -> TyConParent  -- ^ Parent, if exists
                 -> Injectivity  -- ^ Injectivity annotation
                                 -- See [Injectivity annotation] in HsDecls
                 -> TyCon
buildFamilyTyCon tc_name tvs res_tv rhs rhs_kind parent injectivity
  = mkFamilyTyCon tc_name kind tvs res_tv rhs parent injectivity
  where kind = mkPiKinds tvs rhs_kind


------------------------------------------------------
distinctAbstractTyConRhs, totallyAbstractTyConRhs :: AlgTyConRhs
distinctAbstractTyConRhs = AbstractTyCon True
totallyAbstractTyConRhs  = AbstractTyCon False

mkDataTyConRhs :: [DataCon] -> AlgTyConRhs
mkDataTyConRhs cons
  = DataTyCon {
        data_cons = cons,
        is_enum = not (null cons) && all is_enum_con cons
                  -- See Note [Enumeration types] in TyCon
    }
  where
    is_enum_con con
       | (_tvs, theta, arg_tys, _res) <- dataConSig con
       = null theta && null arg_tys


mkNewTyConRhs :: Name -> TyCon -> DataCon -> TcRnIf m n AlgTyConRhs
-- ^ Monadic because it makes a Name for the coercion TyCon
--   We pass the Name of the parent TyCon, as well as the TyCon itself,
--   because the latter is part of a knot, whereas the former is not.
mkNewTyConRhs tycon_name tycon con
  = do  { co_tycon_name <- newImplicitBinder tycon_name mkNewTyCoOcc
        ; let co_tycon = mkNewTypeCo co_tycon_name tycon etad_tvs etad_roles etad_rhs
        ; traceIf (text "mkNewTyConRhs" <+> ppr co_tycon)
        ; return (NewTyCon { data_con    = con,
                             nt_rhs      = rhs_ty,
                             nt_etad_rhs = (etad_tvs, etad_rhs),
                             nt_co       = co_tycon } ) }
                             -- Coreview looks through newtypes with a Nothing
                             -- for nt_co, or uses explicit coercions otherwise
  where
    tvs    = tyConTyVars tycon
    roles  = tyConRoles tycon
    inst_con_ty = applyTys (dataConUserType con) (mkTyVarTys tvs)
    rhs_ty = ASSERT( isFunTy inst_con_ty ) funArgTy inst_con_ty
        -- Instantiate the data con with the
        -- type variables from the tycon
        -- NB: a newtype DataCon has a type that must look like
        --        forall tvs.  <arg-ty> -> T tvs
        -- Note that we *can't* use dataConInstOrigArgTys here because
        -- the newtype arising from   class Foo a => Bar a where {}
        -- has a single argument (Foo a) that is a *type class*, so
        -- dataConInstOrigArgTys returns [].

    etad_tvs   :: [TyVar]  -- Matched lazily, so that mkNewTypeCo can
    etad_roles :: [Role]   -- return a TyCon without pulling on rhs_ty
    etad_rhs   :: Type     -- See Note [Tricky iface loop] in LoadIface
    (etad_tvs, etad_roles, etad_rhs) = eta_reduce (reverse tvs) (reverse roles) rhs_ty

    eta_reduce :: [TyVar]       -- Reversed
               -> [Role]        -- also reversed
               -> Type          -- Rhs type
               -> ([TyVar], [Role], Type)  -- Eta-reduced version
                                           -- (tyvars in normal order)
    eta_reduce (a:as) (_:rs) ty | Just (fun, arg) <- splitAppTy_maybe ty,
                                  Just tv <- getTyVar_maybe arg,
                                  tv == a,
                                  not (a `elemVarSet` tyVarsOfType fun)
                                = eta_reduce as rs fun
    eta_reduce tvs rs ty = (reverse tvs, reverse rs, ty)


------------------------------------------------------
buildDataCon :: FamInstEnvs
            -> Name -> Bool
            -> [HsSrcBang]
            -> Maybe [HsImplBang]
                -- See Note [Bangs on imported data constructors] in MkId
           -> [Name]                   -- Field labels
           -> [TyVar] -> [TyVar]       -- Univ and ext
           -> [(TyVar,Type)]           -- Equality spec
           -> ThetaType                -- Does not include the "stupid theta"
                                       -- or the GADT equalities
           -> [Type] -> Type           -- Argument and result types
           -> TyCon                    -- Rep tycon
           -> TcRnIf m n DataCon
-- A wrapper for DataCon.mkDataCon that
--   a) makes the worker Id
--   b) makes the wrapper Id if necessary, including
--      allocating its unique (hence monadic)
buildDataCon fam_envs src_name declared_infix src_bangs impl_bangs field_lbls
             univ_tvs ex_tvs eq_spec ctxt arg_tys res_ty rep_tycon
  = do  { wrap_name <- newImplicitBinder src_name mkDataConWrapperOcc
        ; work_name <- newImplicitBinder src_name mkDataConWorkerOcc
        -- This last one takes the name of the data constructor in the source
        -- code, which (for Haskell source anyway) will be in the DataName name
        -- space, and puts it into the VarName name space

        ; us <- newUniqueSupply
        ; dflags <- getDynFlags
        ; let
                stupid_ctxt = mkDataConStupidTheta rep_tycon arg_tys univ_tvs
                data_con = mkDataCon src_name declared_infix
                                     src_bangs field_lbls
                                     univ_tvs ex_tvs eq_spec ctxt
                                     arg_tys res_ty rep_tycon
                                     stupid_ctxt dc_wrk dc_rep
                dc_wrk = mkDataConWorkId work_name data_con
                dc_rep = initUs_ us (mkDataConRep dflags fam_envs wrap_name
                                                  impl_bangs data_con)

        ; return data_con }


-- The stupid context for a data constructor should be limited to
-- the type variables mentioned in the arg_tys
-- ToDo: Or functionally dependent on?
--       This whole stupid theta thing is, well, stupid.
mkDataConStupidTheta :: TyCon -> [Type] -> [TyVar] -> [PredType]
mkDataConStupidTheta tycon arg_tys univ_tvs
  | null stupid_theta = []      -- The common case
  | otherwise         = filter in_arg_tys stupid_theta
  where
    tc_subst     = zipTopTvSubst (tyConTyVars tycon) (mkTyVarTys univ_tvs)
    stupid_theta = substTheta tc_subst (tyConStupidTheta tycon)
        -- Start by instantiating the master copy of the
        -- stupid theta, taken from the TyCon

    arg_tyvars      = tyVarsOfTypes arg_tys
    in_arg_tys pred = not $ isEmptyVarSet $
                      tyVarsOfType pred `intersectVarSet` arg_tyvars


------------------------------------------------------
buildPatSyn :: Name -> Bool
            -> (Id,Bool) -> Maybe (Id, Bool)
            -> ([TyVar], ThetaType) -- ^ Univ and req
            -> ([TyVar], ThetaType) -- ^ Ex and prov
            -> [Type]               -- ^ Argument types
            -> Type                 -- ^ Result type
            -> PatSyn
buildPatSyn src_name declared_infix matcher@(matcher_id,_) builder
            (univ_tvs, req_theta) (ex_tvs, prov_theta) arg_tys pat_ty
  = ASSERT((and [ univ_tvs == univ_tvs'
                , ex_tvs == ex_tvs'
                , pat_ty `eqType` pat_ty'
                , prov_theta `eqTypes` prov_theta'
                , req_theta `eqTypes` req_theta'
                , arg_tys `eqTypes` arg_tys'
                ]))
    mkPatSyn src_name declared_infix
             (univ_tvs, req_theta) (ex_tvs, prov_theta)
             arg_tys pat_ty
             matcher builder
  where
    ((_:univ_tvs'), req_theta', tau) = tcSplitSigmaTy $ idType matcher_id
    ([pat_ty', cont_sigma, _], _) = tcSplitFunTys tau
    (ex_tvs', prov_theta', cont_tau) = tcSplitSigmaTy cont_sigma
    (arg_tys', _) = tcSplitFunTys cont_tau

-- ------------------------------------------------------

type TcMethInfo = (Name, DefMethSpec, Type)
        -- A temporary intermediate, to communicate between
        -- tcClassSigs and buildClass.

buildClass :: Name -> [TyVar] -> [Role] -> ThetaType
           -> [FunDep TyVar]               -- Functional dependencies
           -> [ClassATItem]                -- Associated types
           -> [TcMethInfo]                 -- Method info
           -> ClassMinimalDef              -- Minimal complete definition
           -> RecFlag                      -- Info for type constructor
           -> TcRnIf m n Class

buildClass tycon_name tvs roles sc_theta fds at_items sig_stuff mindef tc_isrec
  = fixM  $ \ rec_clas ->       -- Only name generation inside loop
    do  { traceIf (text "buildClass")

        ; datacon_name <- newImplicitBinder tycon_name mkClassDataConOcc
                -- The class name is the 'parent' for this datacon, not its tycon,
                -- because one should import the class to get the binding for
                -- the datacon


        ; op_items <- mapM (mk_op_item rec_clas) sig_stuff
                        -- Build the selector id and default method id

              -- Make selectors for the superclasses
        ; sc_sel_names <- mapM  (newImplicitBinder tycon_name . mkSuperDictSelOcc)
                                (takeList sc_theta [fIRST_TAG..])
        ; let sc_sel_ids = [ mkDictSelId sc_name rec_clas
                           | sc_name <- sc_sel_names]
              -- We number off the Dict superclass selectors, 1, 2, 3 etc so that we
              -- can construct names for the selectors. Thus
              --      class (C a, C b) => D a b where ...
              -- gives superclass selectors
              --      D_sc1, D_sc2
              -- (We used to call them D_C, but now we can have two different
              --  superclasses both called C!)

        ; let use_newtype = isSingleton arg_tys
                -- Use a newtype if the data constructor
                --   (a) has exactly one value field
                --       i.e. exactly one operation or superclass taken together
                --   (b) that value is of lifted type (which they always are, because
                --       we box equality superclasses)
                -- See note [Class newtypes and equality predicates]

                -- We treat the dictionary superclasses as ordinary arguments.
                -- That means that in the case of
                --     class C a => D a
                -- we don't get a newtype with no arguments!
              args      = sc_sel_names ++ op_names
              op_tys    = [ty | (_,_,ty) <- sig_stuff]
              op_names  = [op | (op,_,_) <- sig_stuff]
              arg_tys   = sc_theta ++ op_tys
              rec_tycon = classTyCon rec_clas

        ; dict_con <- buildDataCon (panic "buildClass: FamInstEnvs")
                                   datacon_name
                                   False        -- Not declared infix
                                   (map (const no_bang) args)
                                   (Just (map (const HsLazy) args))
                                   [{- No fields -}]
                                   tvs [{- no existentials -}]
                                   [{- No GADT equalities -}]
                                   [{- No theta -}]
                                   arg_tys
                                   (mkTyConApp rec_tycon (mkTyVarTys tvs))
                                   rec_tycon

        ; rhs <- if use_newtype
                 then mkNewTyConRhs tycon_name rec_tycon dict_con
                 else if isCTupleTyConName tycon_name
                 then return (TupleTyCon { data_con = dict_con
                                         , tup_sort = ConstraintTuple })
                 else return (mkDataTyConRhs [dict_con])

        ; let { clas_kind = mkPiKinds tvs constraintKind

              ; tycon = mkClassTyCon tycon_name clas_kind tvs roles
                                     rhs rec_clas tc_isrec
                -- A class can be recursive, and in the case of newtypes
                -- this matters.  For example
                --      class C a where { op :: C b => a -> b -> Int }
                -- Because C has only one operation, it is represented by
                -- a newtype, and it should be a *recursive* newtype.
                -- [If we don't make it a recursive newtype, we'll expand the
                -- newtype like a synonym, but that will lead to an infinite
                -- type]

              ; result = mkClass tvs fds
                                 sc_theta sc_sel_ids at_items
                                 op_items mindef tycon
              }
        ; traceIf (text "buildClass" <+> ppr tycon)
        ; return result }
  where
    no_bang = HsSrcBang Nothing NoSrcUnpack NoSrcStrict

    mk_op_item :: Class -> TcMethInfo -> TcRnIf n m ClassOpItem
    mk_op_item rec_clas (op_name, dm_spec, _)
      = do { dm_info <- case dm_spec of
                          NoDM      -> return NoDefMeth
                          GenericDM -> do { dm_name <- newImplicitBinder op_name mkGenDefMethodOcc
                                          ; return (GenDefMeth dm_name) }
                          VanillaDM -> do { dm_name <- newImplicitBinder op_name mkDefaultMethodOcc
                                          ; return (DefMeth dm_name) }
           ; return (mkDictSelId op_name rec_clas, dm_info) }

{-
Note [Class newtypes and equality predicates]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
        class (a ~ F b) => C a b where
          op :: a -> b

We cannot represent this by a newtype, even though it's not
existential, because there are two value fields (the equality
predicate and op. See Trac #2238

Moreover,
          class (a ~ F b) => C a b where {}
Here we can't use a newtype either, even though there is only
one field, because equality predicates are unboxed, and classes
are boxed.
-}

newImplicitBinder :: Name                       -- Base name
                  -> (OccName -> OccName)       -- Occurrence name modifier
                  -> TcRnIf m n Name            -- Implicit name
-- Called in BuildTyCl to allocate the implicit binders of type/class decls
-- For source type/class decls, this is the first occurrence
-- For iface ones, the LoadIface has alrady allocated a suitable name in the cache
newImplicitBinder base_name mk_sys_occ
  | Just mod <- nameModule_maybe base_name
  = newGlobalBinder mod occ loc
  | otherwise           -- When typechecking a [d| decl bracket |],
                        -- TH generates types, classes etc with Internal names,
                        -- so we follow suit for the implicit binders
  = do  { uniq <- newUnique
        ; return (mkInternalName uniq occ loc) }
  where
    occ = mk_sys_occ (nameOccName base_name)
    loc = nameSrcSpan base_name