content: {-
  (c) The University of Glasgow 2006
  (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
  -}
  {-# LANGUAGE CPP #-}
  
  module Eta.Iface.BuildTyCl (
          buildSynonymTyCon,
          buildFamilyTyCon,
          buildAlgTyCon,
          buildDataCon,
          buildPatSyn,
          TcMethInfo, buildClass,
          distinctAbstractTyConRhs, totallyAbstractTyConRhs,
          mkNewTyConRhs, mkDataTyConRhs,
          newImplicitBinder
      ) where
  
  import Eta.Iface.IfaceEnv
  import Eta.Types.FamInstEnv( FamInstEnvs )
  import Eta.BasicTypes.DataCon
  import Eta.BasicTypes.PatSyn
  import Eta.BasicTypes.Var
  import Eta.BasicTypes.VarSet
  import Eta.BasicTypes.BasicTypes
  import Eta.BasicTypes.Name
  import Eta.BasicTypes.MkId
  import Eta.Types.Class
  import Eta.Types.TyCon
  import Eta.Types.Type
  import Eta.BasicTypes.Id
  import Eta.Types.Coercion
  import Eta.TypeCheck.TcType
  
  import Eta.Main.DynFlags
  import Eta.TypeCheck.TcRnMonad
  import Eta.BasicTypes.UniqSupply
  import Eta.Utils.Util
  import Eta.Utils.Outputable
  
  #include "HsVersions.h"
  
  ------------------------------------------------------
  buildSynonymTyCon :: Name -> [TyVar] -> [Role]
                    -> Type
                    -> Kind                   -- ^ Kind of the RHS
                    -> TcRnIf m n TyCon
  buildSynonymTyCon tc_name tvs roles rhs rhs_kind
    = return (mkSynonymTyCon tc_name kind tvs roles rhs)
    where kind = mkPiKinds tvs rhs_kind
  
  
  buildFamilyTyCon :: Name -> [TyVar]
                   -> FamTyConFlav
                   -> Kind                   -- ^ Kind of the RHS
                   -> TyConParent
                   -> TcRnIf m n TyCon
  buildFamilyTyCon tc_name tvs rhs rhs_kind parent
    = return (mkFamilyTyCon tc_name kind tvs rhs parent)
    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)
                                  [1..length sc_theta]
          ; 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 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.
  -}
  