    {-
    (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 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
                      -> 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
                -> [HsBang]
                -> [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 arg_stricts 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
                                         arg_stricts 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 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 HsNoBang) 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
        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.
    -}