{-# LANGUAGE CPP #-}

-----------------------------------------------------------------------------
--
-- (c) The University of Glasgow 2006
--
-- The purpose of this module is to transform an HsExpr into a CoreExpr which
-- when evaluated, returns a (Meta.Q Meta.Exp) computation analogous to the
-- input HsExpr. We do this in the DsM monad, which supplies access to
-- CoreExpr's of the "smart constructors" of the Meta.Exp datatype.
--
-- It also defines a bunch of knownKeyNames, in the same way as is done
-- in prelude/PrelNames.  It's much more convenient to do it here, because
-- otherwise we have to recompile PrelNames whenever we add a Name, which is
-- a Royal Pain (triggers other recompilation).
-----------------------------------------------------------------------------

module DsMeta( dsBracket ) where

#include "HsVersions.h"

import {-# SOURCE #-}   DsExpr ( dsExpr )

import MatchLit
import DsMonad

import qualified Language.Haskell.TH as TH

import HsSyn
import Class
import PrelNames
-- To avoid clashes with DsMeta.varName we must make a local alias for
-- OccName.varName we do this by removing varName from the import of
-- OccName above, making a qualified instance of OccName and using
-- OccNameAlias.varName where varName ws previously used in this file.
import qualified OccName( isDataOcc, isVarOcc, isTcOcc )

import Module
import Id
import Name hiding( isVarOcc, isTcOcc, varName, tcName )
import THNames
import NameEnv
import TcType
import TyCon
import TysWiredIn
import TysPrim ( liftedTypeKindTyConName, constraintKindTyConName )
import CoreSyn
import MkCore
import CoreUtils
import SrcLoc
import Unique
import BasicTypes
import Outputable
import Bag
import DynFlags
import FastString
import ForeignCall
import Util
import MonadUtils

import Data.ByteString ( unpack )
import Data.Maybe
import Control.Monad
import Data.List

-----------------------------------------------------------------------------
dsBracket :: HsBracket Name -> [PendingTcSplice] -> DsM CoreExpr
-- Returns a CoreExpr of type TH.ExpQ
-- The quoted thing is parameterised over Name, even though it has
-- been type checked.  We don't want all those type decorations!

dsBracket brack splices
  = dsExtendMetaEnv new_bit (do_brack brack)
  where
    new_bit = mkNameEnv [(n, DsSplice (unLoc e)) | PendingTcSplice n e <- splices]

    do_brack (VarBr _ n) = do { MkC e1  <- lookupOcc n ; return e1 }
    do_brack (ExpBr e)   = do { MkC e1  <- repLE e     ; return e1 }
    do_brack (PatBr p)   = do { MkC p1  <- repTopP p   ; return p1 }
    do_brack (TypBr t)   = do { MkC t1  <- repLTy t    ; return t1 }
    do_brack (DecBrG gp) = do { MkC ds1 <- repTopDs gp ; return ds1 }
    do_brack (DecBrL _)  = panic "dsBracket: unexpected DecBrL"
    do_brack (TExpBr e)  = do { MkC e1  <- repLE e     ; return e1 }

{- -------------- Examples --------------------

  [| \x -> x |]
====>
  gensym (unpackString "x"#) `bindQ` \ x1::String ->
  lam (pvar x1) (var x1)


  [| \x -> $(f [| x |]) |]
====>
  gensym (unpackString "x"#) `bindQ` \ x1::String ->
  lam (pvar x1) (f (var x1))
-}


-------------------------------------------------------
--                      Declarations
-------------------------------------------------------

repTopP :: LPat Name -> DsM (Core TH.PatQ)
repTopP pat = do { ss <- mkGenSyms (collectPatBinders pat)
                 ; pat' <- addBinds ss (repLP pat)
                 ; wrapGenSyms ss pat' }

repTopDs :: HsGroup Name -> DsM (Core (TH.Q [TH.Dec]))
repTopDs group@(HsGroup { hs_valds   = valds
                        , hs_splcds  = splcds
                        , hs_tyclds  = tyclds
                        , hs_instds  = instds
                        , hs_derivds = derivds
                        , hs_fixds   = fixds
                        , hs_defds   = defds
                        , hs_fords   = fords
                        , hs_warnds  = warnds
                        , hs_annds   = annds
                        , hs_ruleds  = ruleds
                        , hs_vects   = vects
                        , hs_docs    = docs })
 = do { let { tv_bndrs = hsSigTvBinders valds
            ; bndrs = tv_bndrs ++ hsGroupBinders group } ;
        ss <- mkGenSyms bndrs ;

        -- Bind all the names mainly to avoid repeated use of explicit strings.
        -- Thus we get
        --      do { t :: String <- genSym "T" ;
        --           return (Data t [] ...more t's... }
        -- The other important reason is that the output must mention
        -- only "T", not "Foo:T" where Foo is the current module

        decls <- addBinds ss (
                  do { val_ds   <- rep_val_binds valds
                     ; _        <- mapM no_splice splcds
                     ; tycl_ds  <- mapM repTyClD (tyClGroupConcat tyclds)
                     ; role_ds  <- mapM repRoleD (concatMap group_roles tyclds)
                     ; inst_ds  <- mapM repInstD instds
                     ; deriv_ds <- mapM repStandaloneDerivD derivds
                     ; fix_ds   <- mapM repFixD fixds
                     ; _        <- mapM no_default_decl defds
                     ; for_ds   <- mapM repForD fords
                     ; _        <- mapM no_warn (concatMap (wd_warnings . unLoc)
                                                           warnds)
                     ; ann_ds   <- mapM repAnnD annds
                     ; rule_ds  <- mapM repRuleD (concatMap (rds_rules . unLoc)
                                                            ruleds)
                     ; _        <- mapM no_vect vects
                     ; _        <- mapM no_doc docs

                        -- more needed
                     ;  return (de_loc $ sort_by_loc $
                                val_ds ++ catMaybes tycl_ds ++ role_ds
                                       ++ (concat fix_ds)
                                       ++ inst_ds ++ rule_ds ++ for_ds
                                       ++ ann_ds ++ deriv_ds) }) ;

        decl_ty <- lookupType decQTyConName ;
        let { core_list = coreList' decl_ty decls } ;

        dec_ty <- lookupType decTyConName ;
        q_decs  <- repSequenceQ dec_ty core_list ;

        wrapGenSyms ss q_decs
      }
  where
    no_splice (L loc _)
      = notHandledL loc "Splices within declaration brackets" empty
    no_default_decl (L loc decl)
      = notHandledL loc "Default declarations" (ppr decl)
    no_warn (L loc (Warning thing _))
      = notHandledL loc "WARNING and DEPRECATION pragmas" $
                    text "Pragma for declaration of" <+> ppr thing
    no_vect (L loc decl)
      = notHandledL loc "Vectorisation pragmas" (ppr decl)
    no_doc (L loc _)
      = notHandledL loc "Haddock documentation" empty

hsSigTvBinders :: HsValBinds Name -> [Name]
-- See Note [Scoped type variables in bindings]
hsSigTvBinders binds
  = [hsLTyVarName tv | L _ (TypeSig _ (L _ (HsForAllTy Explicit _ qtvs _ _)) _) <- sigs
                     , tv <- hsQTvBndrs qtvs]
  where
    sigs = case binds of
             ValBindsIn  _ sigs -> sigs
             ValBindsOut _ sigs -> sigs


{- Notes

Note [Scoped type variables in bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   f :: forall a. a -> a
   f x = x::a
Here the 'forall a' brings 'a' into scope over the binding group.
To achieve this we

  a) Gensym a binding for 'a' at the same time as we do one for 'f'
     collecting the relevant binders with hsSigTvBinders

  b) When processing the 'forall', don't gensym

The relevant places are signposted with references to this Note

Note [Binders and occurrences]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
When we desugar [d| data T = MkT |]
we want to get
        Data "T" [] [Con "MkT" []] []
and *not*
        Data "Foo:T" [] [Con "Foo:MkT" []] []
That is, the new data decl should fit into whatever new module it is
asked to fit in.   We do *not* clone, though; no need for this:
        Data "T79" ....

But if we see this:
        data T = MkT
        foo = reifyDecl T

then we must desugar to
        foo = Data "Foo:T" [] [Con "Foo:MkT" []] []

So in repTopDs we bring the binders into scope with mkGenSyms and addBinds.
And we use lookupOcc, rather than lookupBinder
in repTyClD and repC.

-}

-- represent associated family instances
--
repTyClD :: LTyClDecl Name -> DsM (Maybe (SrcSpan, Core TH.DecQ))

repTyClD (L loc (FamDecl { tcdFam = fam })) = liftM Just $ repFamilyDecl (L loc fam)

repTyClD (L loc (SynDecl { tcdLName = tc, tcdTyVars = tvs, tcdRhs = rhs }))
  = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
       ; dec <- addTyClTyVarBinds tvs $ \bndrs ->
                repSynDecl tc1 bndrs rhs
       ; return (Just (loc, dec)) }

repTyClD (L loc (DataDecl { tcdLName = tc, tcdTyVars = tvs, tcdDataDefn = defn }))
  = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
       ; tc_tvs <- mk_extra_tvs tc tvs defn
       ; dec <- addTyClTyVarBinds tc_tvs $ \bndrs ->
                repDataDefn tc1 bndrs Nothing (hsLTyVarNames tc_tvs) defn
       ; return (Just (loc, dec)) }

repTyClD (L loc (ClassDecl { tcdCtxt = cxt, tcdLName = cls,
                             tcdTyVars = tvs, tcdFDs = fds,
                             tcdSigs = sigs, tcdMeths = meth_binds,
                             tcdATs = ats, tcdATDefs = [] }))
  = do { cls1 <- lookupLOcc cls         -- See note [Binders and occurrences]
       ; dec  <- addTyVarBinds tvs $ \bndrs ->
           do { cxt1   <- repLContext cxt
              ; sigs1  <- rep_sigs sigs
              ; binds1 <- rep_binds meth_binds
              ; fds1   <- repLFunDeps fds
              ; ats1   <- repFamilyDecls ats
              ; decls1 <- coreList decQTyConName (ats1 ++ sigs1 ++ binds1)
              ; repClass cxt1 cls1 bndrs fds1 decls1
              }
       ; return $ Just (loc, dec)
       }

-- Un-handled cases
repTyClD (L loc d) = putSrcSpanDs loc $
                     do { warnDs (hang ds_msg 4 (ppr d))
                        ; return Nothing }

-------------------------
repRoleD :: LRoleAnnotDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repRoleD (L loc (RoleAnnotDecl tycon roles))
  = do { tycon1 <- lookupLOcc tycon
       ; roles1 <- mapM repRole roles
       ; roles2 <- coreList roleTyConName roles1
       ; dec <- repRoleAnnotD tycon1 roles2
       ; return (loc, dec) }

-------------------------
repDataDefn :: Core TH.Name -> Core [TH.TyVarBndr]
            -> Maybe (Core [TH.TypeQ])
            -> [Name] -> HsDataDefn Name
            -> DsM (Core TH.DecQ)
repDataDefn tc bndrs opt_tys tv_names
          (HsDataDefn { dd_ND = new_or_data, dd_ctxt = cxt
                      , dd_cons = cons, dd_derivs = mb_derivs })
  = do { cxt1     <- repLContext cxt
       ; derivs1  <- repDerivs mb_derivs
       ; case new_or_data of
           NewType  -> do { con1 <- repC tv_names (head cons)
                          ; case con1 of
                             [c] -> repNewtype cxt1 tc bndrs opt_tys c derivs1
                             _cs -> failWithDs (ptext
                                     (sLit "Multiple constructors for newtype:")
                                      <+> pprQuotedList
                                                (con_names $ unLoc $ head cons))
                          }
           DataType -> do { consL <- concatMapM (repC tv_names) cons
                          ; cons1 <- coreList conQTyConName consL
                          ; repData cxt1 tc bndrs opt_tys cons1 derivs1 } }

repSynDecl :: Core TH.Name -> Core [TH.TyVarBndr]
          -> LHsType Name
          -> DsM (Core TH.DecQ)
repSynDecl tc bndrs ty
  = do { ty1 <- repLTy ty
       ; repTySyn tc bndrs ty1 }

repFamilyDecl :: LFamilyDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repFamilyDecl decl@(L loc (FamilyDecl { fdInfo      = info,
                                        fdLName     = tc,
                                        fdTyVars    = tvs,
                                        fdResultSig = L _ resultSig,
                                        fdInjectivityAnn = injectivity }))
  = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
       ; let mkHsQTvs tvs = HsQTvs { hsq_kvs = [], hsq_tvs = tvs }
             resTyVar = case resultSig of
                     TyVarSig bndr -> mkHsQTvs [bndr]
                     _             -> mkHsQTvs []
       ; dec <- addTyClTyVarBinds tvs $ \bndrs ->
                addTyClTyVarBinds resTyVar $ \_ ->
           case info of
             ClosedTypeFamily Nothing ->
                 notHandled "abstract closed type family" (ppr decl)
             ClosedTypeFamily (Just eqns) ->
               do { eqns1  <- mapM repTyFamEqn eqns
                  ; eqns2  <- coreList tySynEqnQTyConName eqns1
                  ; result <- repFamilyResultSig resultSig
                  ; inj    <- repInjectivityAnn injectivity
                  ; repClosedFamilyD tc1 bndrs result inj eqns2 }
             OpenTypeFamily ->
               do { result <- repFamilyResultSig resultSig
                  ; inj    <- repInjectivityAnn injectivity
                  ; repOpenFamilyD tc1 bndrs result inj }
             DataFamily ->
               do { kind <- repFamilyResultSigToMaybeKind resultSig
                  ; repDataFamilyD tc1 bndrs kind }
       ; return (loc, dec)
       }

-- | Represent result signature of a type family
repFamilyResultSig :: FamilyResultSig Name -> DsM (Core TH.FamilyResultSig)
repFamilyResultSig  NoSig          = repNoSig
repFamilyResultSig (KindSig ki)    = do { ki' <- repLKind ki
                                        ; repKindSig ki' }
repFamilyResultSig (TyVarSig bndr) = do { bndr' <- repTyVarBndr bndr
                                        ; repTyVarSig bndr' }

-- | Represent result signature using a Maybe Kind. Used with data families,
-- where the result signature can be either missing or a kind but never a named
-- result variable.
repFamilyResultSigToMaybeKind :: FamilyResultSig Name
                              -> DsM (Core (Maybe TH.Kind))
repFamilyResultSigToMaybeKind NoSig =
    do { coreNothing kindTyConName }
repFamilyResultSigToMaybeKind (KindSig ki) =
    do { ki' <- repLKind ki
       ; coreJust kindTyConName ki' }
repFamilyResultSigToMaybeKind _ = panic "repFamilyResultSigToMaybeKind"

-- | Represent injectivity annotation of a type family
repInjectivityAnn :: Maybe (LInjectivityAnn Name)
                  -> DsM (Core (Maybe TH.InjectivityAnn))
repInjectivityAnn Nothing =
    do { coreNothing injAnnTyConName }
repInjectivityAnn (Just (L _ (InjectivityAnn lhs rhs))) =
    do { lhs'   <- lookupBinder (unLoc lhs)
       ; rhs1   <- mapM (lookupBinder . unLoc) rhs
       ; rhs2   <- coreList nameTyConName rhs1
       ; injAnn <- rep2 injectivityAnnName [unC lhs', unC rhs2]
       ; coreJust injAnnTyConName injAnn }

repFamilyDecls :: [LFamilyDecl Name] -> DsM [Core TH.DecQ]
repFamilyDecls fds = liftM de_loc (mapM repFamilyDecl fds)

-------------------------
mk_extra_tvs :: Located Name -> LHsTyVarBndrs Name
             -> HsDataDefn Name -> DsM (LHsTyVarBndrs Name)
-- If there is a kind signature it must be of form
--    k1 -> .. -> kn -> *
-- Return type variables [tv1:k1, tv2:k2, .., tvn:kn]
mk_extra_tvs tc tvs defn
  | HsDataDefn { dd_kindSig = Just hs_kind } <- defn
  = do { extra_tvs <- go hs_kind
       ; return (tvs { hsq_tvs = hsq_tvs tvs ++ extra_tvs }) }
  | otherwise
  = return tvs
  where
    go :: LHsKind Name -> DsM [LHsTyVarBndr Name]
    go (L loc (HsFunTy kind rest))
      = do { uniq <- newUnique
           ; let { occ = mkTyVarOccFS (fsLit "t")
                 ; nm = mkInternalName uniq occ loc
                 ; hs_tv = L loc (KindedTyVar (noLoc nm) kind) }
           ; hs_tvs <- go rest
           ; return (hs_tv : hs_tvs) }

    go (L _ (HsTyVar n))
      | n == liftedTypeKindTyConName
      = return []

    go _ = failWithDs (ptext (sLit "Malformed kind signature for") <+> ppr tc)

-------------------------
-- represent fundeps
--
repLFunDeps :: [Located (FunDep (Located Name))] -> DsM (Core [TH.FunDep])
repLFunDeps fds = repList funDepTyConName repLFunDep fds

repLFunDep :: Located (FunDep (Located Name)) -> DsM (Core TH.FunDep)
repLFunDep (L _ (xs, ys))
   = do xs' <- repList nameTyConName (lookupBinder . unLoc) xs
        ys' <- repList nameTyConName (lookupBinder . unLoc) ys
        repFunDep xs' ys'

-- Represent instance declarations
--
repInstD :: LInstDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repInstD (L loc (TyFamInstD { tfid_inst = fi_decl }))
  = do { dec <- repTyFamInstD fi_decl
       ; return (loc, dec) }
repInstD (L loc (DataFamInstD { dfid_inst = fi_decl }))
  = do { dec <- repDataFamInstD fi_decl
       ; return (loc, dec) }
repInstD (L loc (ClsInstD { cid_inst = cls_decl }))
  = do { dec <- repClsInstD cls_decl
       ; return (loc, dec) }

repClsInstD :: ClsInstDecl Name -> DsM (Core TH.DecQ)
repClsInstD (ClsInstDecl { cid_poly_ty = ty, cid_binds = binds
                         , cid_sigs = prags, cid_tyfam_insts = ats
                         , cid_datafam_insts = adts })
  = addTyVarBinds tvs $ \_ ->
            -- We must bring the type variables into scope, so their
            -- occurrences don't fail, even though the binders don't
            -- appear in the resulting data structure
            --
            -- But we do NOT bring the binders of 'binds' into scope
            -- because they are properly regarded as occurrences
            -- For example, the method names should be bound to
            -- the selector Ids, not to fresh names (Trac #5410)
            --
            do { cxt1 <- repContext cxt
               ; cls_tcon <- repTy (HsTyVar (unLoc cls))
               ; cls_tys <- repLTys tys
               ; inst_ty1 <- repTapps cls_tcon cls_tys
               ; binds1 <- rep_binds binds
               ; prags1 <- rep_sigs prags
               ; ats1 <- mapM (repTyFamInstD . unLoc) ats
               ; adts1 <- mapM (repDataFamInstD . unLoc) adts
               ; decls <- coreList decQTyConName (ats1 ++ adts1 ++ binds1 ++ prags1)
               ; repInst cxt1 inst_ty1 decls }
 where
   Just (tvs, cxt, cls, tys) = splitLHsInstDeclTy_maybe ty

repStandaloneDerivD :: LDerivDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repStandaloneDerivD (L loc (DerivDecl { deriv_type = ty }))
  = do { dec <- addTyVarBinds tvs $ \_ ->
                do { cxt' <- repContext cxt
                   ; cls_tcon <- repTy (HsTyVar (unLoc cls))
                   ; cls_tys <- repLTys tys
                   ; inst_ty <- repTapps cls_tcon cls_tys
                   ; repDeriv cxt' inst_ty }
       ; return (loc, dec) }
  where
    Just (tvs, cxt, cls, tys) = splitLHsInstDeclTy_maybe ty

repTyFamInstD :: TyFamInstDecl Name -> DsM (Core TH.DecQ)
repTyFamInstD decl@(TyFamInstDecl { tfid_eqn = eqn })
  = do { let tc_name = tyFamInstDeclLName decl
       ; tc <- lookupLOcc tc_name               -- See note [Binders and occurrences]
       ; eqn1 <- repTyFamEqn eqn
       ; repTySynInst tc eqn1 }

repTyFamEqn :: LTyFamInstEqn Name -> DsM (Core TH.TySynEqnQ)
repTyFamEqn (L loc (TyFamEqn { tfe_pats = HsWB { hswb_cts = tys
                                               , hswb_kvs = kv_names
                                               , hswb_tvs = tv_names }
                                 , tfe_rhs = rhs }))
  = do { let hs_tvs = HsQTvs { hsq_kvs = kv_names
                             , hsq_tvs = userHsTyVarBndrs loc tv_names }   -- Yuk
       ; addTyClTyVarBinds hs_tvs $ \ _ ->
         do { tys1 <- repLTys tys
            ; tys2 <- coreList typeQTyConName tys1
            ; rhs1 <- repLTy rhs
            ; repTySynEqn tys2 rhs1 } }

repDataFamInstD :: DataFamInstDecl Name -> DsM (Core TH.DecQ)
repDataFamInstD (DataFamInstDecl { dfid_tycon = tc_name
                                 , dfid_pats = HsWB { hswb_cts = tys, hswb_kvs = kv_names, hswb_tvs = tv_names }
                                 , dfid_defn = defn })
  = do { tc <- lookupLOcc tc_name               -- See note [Binders and occurrences]
       ; let loc = getLoc tc_name
             hs_tvs = HsQTvs { hsq_kvs = kv_names, hsq_tvs = userHsTyVarBndrs loc tv_names }   -- Yuk
       ; addTyClTyVarBinds hs_tvs $ \ bndrs ->
         do { tys1 <- repList typeQTyConName repLTy tys
            ; repDataDefn tc bndrs (Just tys1) tv_names defn } }

repForD :: Located (ForeignDecl Name) -> DsM (SrcSpan, Core TH.DecQ)
repForD (L loc (ForeignImport name typ _ (CImport (L _ cc) (L _ s) mch cis _)))
 = do MkC name' <- lookupLOcc name
      MkC typ' <- repLTy typ
      MkC cc' <- repCCallConv cc
      MkC s' <- repSafety s
      cis' <- conv_cimportspec cis
      MkC str <- coreStringLit (static ++ chStr ++ cis')
      dec <- rep2 forImpDName [cc', s', str, name', typ']
      return (loc, dec)
 where
    conv_cimportspec (CLabel cls) = notHandled "Foreign label" (doubleQuotes (ppr cls))
    conv_cimportspec (CFunction DynamicTarget) = return "dynamic"
    conv_cimportspec (CFunction (StaticTarget _ fs _ True))
                            = return (unpackFS fs)
    conv_cimportspec (CFunction (StaticTarget _ _  _ False))
                            = panic "conv_cimportspec: values not supported yet"
    conv_cimportspec CWrapper = return "wrapper"
    -- these calling conventions do not support headers and the static keyword
    raw_cconv = cc == PrimCallConv || cc == JavaScriptCallConv
    static = case cis of
                 CFunction (StaticTarget _ _ _ _) | not raw_cconv -> "static "
                 _ -> ""
    chStr = case mch of
            Just (Header _ h) | not raw_cconv -> unpackFS h ++ " "
            _ -> ""
repForD decl = notHandled "Foreign declaration" (ppr decl)

repCCallConv :: CCallConv -> DsM (Core TH.Callconv)
repCCallConv CCallConv          = rep2 cCallName []
repCCallConv StdCallConv        = rep2 stdCallName []
repCCallConv CApiConv           = rep2 cApiCallName []
repCCallConv PrimCallConv       = rep2 primCallName []
repCCallConv JavaScriptCallConv = rep2 javaScriptCallName []

repSafety :: Safety -> DsM (Core TH.Safety)
repSafety PlayRisky = rep2 unsafeName []
repSafety PlayInterruptible = rep2 interruptibleName []
repSafety PlaySafe = rep2 safeName []

repFixD :: LFixitySig Name -> DsM [(SrcSpan, Core TH.DecQ)]
repFixD (L loc (FixitySig names (Fixity prec dir)))
  = do { MkC prec' <- coreIntLit prec
       ; let rep_fn = case dir of
                        InfixL -> infixLDName
                        InfixR -> infixRDName
                        InfixN -> infixNDName
       ; let do_one name
              = do { MkC name' <- lookupLOcc name
                   ; dec <- rep2 rep_fn [prec', name']
                   ; return (loc,dec) }
       ; mapM do_one names }

repRuleD :: LRuleDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repRuleD (L loc (HsRule n act bndrs lhs _ rhs _))
  = do { let bndr_names = concatMap ruleBndrNames bndrs
       ; ss <- mkGenSyms bndr_names
       ; rule1 <- addBinds ss $
                  do { bndrs' <- repList ruleBndrQTyConName repRuleBndr bndrs
                     ; n'   <- coreStringLit $ unpackFS $ snd $ unLoc n
                     ; act' <- repPhases act
                     ; lhs' <- repLE lhs
                     ; rhs' <- repLE rhs
                     ; repPragRule n' bndrs' lhs' rhs' act' }
       ; rule2 <- wrapGenSyms ss rule1
       ; return (loc, rule2) }

ruleBndrNames :: LRuleBndr Name -> [Name]
ruleBndrNames (L _ (RuleBndr n))      = [unLoc n]
ruleBndrNames (L _ (RuleBndrSig n (HsWB { hswb_kvs = kvs, hswb_tvs = tvs })))
  = unLoc n : kvs ++ tvs

repRuleBndr :: LRuleBndr Name -> DsM (Core TH.RuleBndrQ)
repRuleBndr (L _ (RuleBndr n))
  = do { MkC n' <- lookupLBinder n
       ; rep2 ruleVarName [n'] }
repRuleBndr (L _ (RuleBndrSig n (HsWB { hswb_cts = ty })))
  = do { MkC n'  <- lookupLBinder n
       ; MkC ty' <- repLTy ty
       ; rep2 typedRuleVarName [n', ty'] }

repAnnD :: LAnnDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repAnnD (L loc (HsAnnotation _ ann_prov (L _ exp)))
  = do { target <- repAnnProv ann_prov
       ; exp'   <- repE exp
       ; dec    <- repPragAnn target exp'
       ; return (loc, dec) }

repAnnProv :: AnnProvenance Name -> DsM (Core TH.AnnTarget)
repAnnProv (ValueAnnProvenance (L _ n))
  = do { MkC n' <- globalVar n  -- ANNs are allowed only at top-level
       ; rep2 valueAnnotationName [ n' ] }
repAnnProv (TypeAnnProvenance (L _ n))
  = do { MkC n' <- globalVar n
       ; rep2 typeAnnotationName [ n' ] }
repAnnProv ModuleAnnProvenance
  = rep2 moduleAnnotationName []

ds_msg :: SDoc
ds_msg = ptext (sLit "Cannot desugar this Template Haskell declaration:")

-------------------------------------------------------
--                      Constructors
-------------------------------------------------------

repC :: [Name] -> LConDecl Name -> DsM [Core TH.ConQ]
repC _ (L _ (ConDecl { con_names = con, con_qvars = con_tvs, con_cxt = L _ []
                     , con_details = details, con_res = ResTyH98 }))
  | null (hsQTvBndrs con_tvs)
  = do { con1 <- mapM lookupLOcc con       -- See Note [Binders and occurrences]
       ; mapM (\c -> repConstr c details) con1  }

repC tvs (L _ (ConDecl { con_names = cons
                       , con_qvars = con_tvs, con_cxt = L _ ctxt
                       , con_details = details
                       , con_res = res_ty }))
  = do { (eq_ctxt, con_tv_subst) <- mkGadtCtxt tvs res_ty
       ; let ex_tvs = HsQTvs { hsq_kvs = filterOut (in_subst con_tv_subst) (hsq_kvs con_tvs)
                             , hsq_tvs = filterOut (in_subst con_tv_subst . hsLTyVarName) (hsq_tvs con_tvs) }

       ; binds <- mapM dupBinder con_tv_subst
       ; b <- dsExtendMetaEnv (mkNameEnv binds) $ -- Binds some of the con_tvs
         addTyVarBinds ex_tvs $ \ ex_bndrs ->   -- Binds the remaining con_tvs
    do { cons1     <- mapM lookupLOcc cons -- See Note [Binders and occurrences]
       ; c'        <- mapM (\c -> repConstr c details) cons1
       ; ctxt'     <- repContext (eq_ctxt ++ ctxt)
       ; rep2 forallCName ([unC ex_bndrs, unC ctxt'] ++ (map unC c')) }
    ; return [b]
    }

in_subst :: [(Name,Name)] -> Name -> Bool
in_subst []          _ = False
in_subst ((n',_):ns) n = n==n' || in_subst ns n

mkGadtCtxt :: [Name]            -- Tyvars of the data type
           -> ResType (LHsType Name)
           -> DsM (HsContext Name, [(Name,Name)])
-- Given a data type in GADT syntax, figure out the equality
-- context, so that we can represent it with an explicit
-- equality context, because that is the only way to express
-- the GADT in TH syntax
--
-- Example:
-- data T a b c where { MkT :: forall d e. d -> e -> T d [e] e
--     mkGadtCtxt [a,b,c] [d,e] (T d [e] e)
--   returns
--     (b~[e], c~e), [d->a]
--
-- This function is fiddly, but not really hard
mkGadtCtxt _ ResTyH98
  = return ([], [])
mkGadtCtxt data_tvs (ResTyGADT _ res_ty)
  | Just (_, tys) <- hsTyGetAppHead_maybe res_ty
  , data_tvs `equalLength` tys
  = return (go [] [] (data_tvs `zip` tys))

  | otherwise
  = failWithDs (ptext (sLit "Malformed constructor result type:") <+> ppr res_ty)
  where
    go cxt subst [] = (cxt, subst)
    go cxt subst ((data_tv, ty) : rest)
       | Just con_tv <- is_hs_tyvar ty
       , isTyVarName con_tv
       , not (in_subst subst con_tv)
       = go cxt ((con_tv, data_tv) : subst) rest
       | otherwise
       = go (eq_pred : cxt) subst rest
       where
         loc = getLoc ty
         eq_pred = L loc (HsEqTy (L loc (HsTyVar data_tv)) ty)

    is_hs_tyvar (L _ (HsTyVar n))  = Just n   -- Type variables *and* tycons
    is_hs_tyvar (L _ (HsParTy ty)) = is_hs_tyvar ty
    is_hs_tyvar _                  = Nothing


repBangTy :: LBangType Name -> DsM (Core (TH.StrictTypeQ))
repBangTy ty = do
  MkC s <- rep2 str []
  MkC t <- repLTy ty'
  rep2 strictTypeName [s, t]
  where
    (str, ty') = case ty of
         L _ (HsBangTy (HsSrcBang _ SrcUnpack SrcStrict) ty)
           -> (unpackedName,  ty)
         L _ (HsBangTy (HsSrcBang _ _         SrcStrict) ty)
           -> (isStrictName,  ty)
         _ -> (notStrictName, ty)

-------------------------------------------------------
--                      Deriving clause
-------------------------------------------------------

repDerivs :: Maybe (Located [LHsType Name]) -> DsM (Core [TH.Name])
repDerivs Nothing = coreList nameTyConName []
repDerivs (Just (L _ ctxt))
  = repList nameTyConName rep_deriv ctxt
  where
    rep_deriv :: LHsType Name -> DsM (Core TH.Name)
        -- Deriving clauses must have the simple H98 form
    rep_deriv ty
      | Just (cls, []) <- splitHsClassTy_maybe (unLoc ty)
      = lookupOcc cls
      | otherwise
      = notHandled "Non-H98 deriving clause" (ppr ty)


-------------------------------------------------------
--   Signatures in a class decl, or a group of bindings
-------------------------------------------------------

rep_sigs :: [LSig Name] -> DsM [Core TH.DecQ]
rep_sigs sigs = do locs_cores <- rep_sigs' sigs
                   return $ de_loc $ sort_by_loc locs_cores

rep_sigs' :: [LSig Name] -> DsM [(SrcSpan, Core TH.DecQ)]
        -- We silently ignore ones we don't recognise
rep_sigs' sigs = do { sigs1 <- mapM rep_sig sigs ;
                     return (concat sigs1) }

rep_sig :: LSig Name -> DsM [(SrcSpan, Core TH.DecQ)]
rep_sig (L loc (TypeSig nms ty _))    = mapM (rep_ty_sig sigDName loc ty) nms
rep_sig (L _   (PatSynSig {}))        = notHandled "Pattern type signatures" empty
rep_sig (L loc (GenericSig nms ty))   = mapM (rep_ty_sig defaultSigDName loc ty) nms
rep_sig d@(L _ (IdSig {}))            = pprPanic "rep_sig IdSig" (ppr d)
rep_sig (L _   (FixSig {}))           = return [] -- fixity sigs at top level
rep_sig (L loc (InlineSig nm ispec))  = rep_inline nm ispec loc
rep_sig (L loc (SpecSig nm tys ispec))
   = concatMapM (\t -> rep_specialise nm t ispec loc) tys
rep_sig (L loc (SpecInstSig _ ty))    = rep_specialiseInst ty loc
rep_sig (L _   (MinimalSig {}))       = notHandled "MINIMAL pragmas" empty

rep_ty_sig :: Name -> SrcSpan -> LHsType Name -> Located Name
           -> DsM (SrcSpan, Core TH.DecQ)
rep_ty_sig mk_sig loc (L _ ty) nm
  = do { nm1 <- lookupLOcc nm
       ; ty1 <- rep_ty ty
       ; sig <- repProto mk_sig nm1 ty1
       ; return (loc, sig) }
  where
    -- We must special-case the top-level explicit for-all of a TypeSig
    -- See Note [Scoped type variables in bindings]
    rep_ty (HsForAllTy Explicit _ tvs ctxt ty)
      = do { let rep_in_scope_tv tv = do { name <- lookupBinder (hsLTyVarName tv)
                                         ; repTyVarBndrWithKind tv name }
           ; bndrs1 <- repList tyVarBndrTyConName rep_in_scope_tv (hsQTvBndrs tvs)
           ; ctxt1  <- repLContext ctxt
           ; ty1    <- repLTy ty
           ; repTForall bndrs1 ctxt1 ty1 }

    rep_ty ty = repTy ty

rep_inline :: Located Name
           -> InlinePragma      -- Never defaultInlinePragma
           -> SrcSpan
           -> DsM [(SrcSpan, Core TH.DecQ)]
rep_inline nm ispec loc
  = do { nm1    <- lookupLOcc nm
       ; inline <- repInline $ inl_inline ispec
       ; rm     <- repRuleMatch $ inl_rule ispec
       ; phases <- repPhases $ inl_act ispec
       ; pragma <- repPragInl nm1 inline rm phases
       ; return [(loc, pragma)]
       }

rep_specialise :: Located Name -> LHsType Name -> InlinePragma -> SrcSpan
               -> DsM [(SrcSpan, Core TH.DecQ)]
rep_specialise nm ty ispec loc
  = do { nm1 <- lookupLOcc nm
       ; ty1 <- repLTy ty
       ; phases <- repPhases $ inl_act ispec
       ; let inline = inl_inline ispec
       ; pragma <- if isEmptyInlineSpec inline
                   then -- SPECIALISE
                     repPragSpec nm1 ty1 phases
                   else -- SPECIALISE INLINE
                     do { inline1 <- repInline inline
                        ; repPragSpecInl nm1 ty1 inline1 phases }
       ; return [(loc, pragma)]
       }

rep_specialiseInst :: LHsType Name -> SrcSpan -> DsM [(SrcSpan, Core TH.DecQ)]
rep_specialiseInst ty loc
  = do { ty1    <- repLTy ty
       ; pragma <- repPragSpecInst ty1
       ; return [(loc, pragma)] }

repInline :: InlineSpec -> DsM (Core TH.Inline)
repInline NoInline  = dataCon noInlineDataConName
repInline Inline    = dataCon inlineDataConName
repInline Inlinable = dataCon inlinableDataConName
repInline spec      = notHandled "repInline" (ppr spec)

repRuleMatch :: RuleMatchInfo -> DsM (Core TH.RuleMatch)
repRuleMatch ConLike = dataCon conLikeDataConName
repRuleMatch FunLike = dataCon funLikeDataConName

repPhases :: Activation -> DsM (Core TH.Phases)
repPhases (ActiveBefore i) = do { MkC arg <- coreIntLit i
                                ; dataCon' beforePhaseDataConName [arg] }
repPhases (ActiveAfter i)  = do { MkC arg <- coreIntLit i
                                ; dataCon' fromPhaseDataConName [arg] }
repPhases _                = dataCon allPhasesDataConName

-------------------------------------------------------
--                      Types
-------------------------------------------------------

addTyVarBinds :: LHsTyVarBndrs Name                            -- the binders to be added
              -> (Core [TH.TyVarBndr] -> DsM (Core (TH.Q a)))  -- action in the ext env
              -> DsM (Core (TH.Q a))
-- gensym a list of type variables and enter them into the meta environment;
-- the computations passed as the second argument is executed in that extended
-- meta environment and gets the *new* names on Core-level as an argument

addTyVarBinds (HsQTvs { hsq_kvs = kvs, hsq_tvs = tvs }) m
  = do { fresh_kv_names <- mkGenSyms kvs
       ; fresh_tv_names <- mkGenSyms (map hsLTyVarName tvs)
       ; let fresh_names = fresh_kv_names ++ fresh_tv_names
       ; term <- addBinds fresh_names $
                 do { kbs <- repList tyVarBndrTyConName mk_tv_bndr (tvs `zip` fresh_tv_names)
                    ; m kbs }
       ; wrapGenSyms fresh_names term }
  where
    mk_tv_bndr (tv, (_,v)) = repTyVarBndrWithKind tv (coreVar v)

addTyClTyVarBinds :: LHsTyVarBndrs Name
                  -> (Core [TH.TyVarBndr] -> DsM (Core (TH.Q a)))
                  -> DsM (Core (TH.Q a))

-- Used for data/newtype declarations, and family instances,
-- so that the nested type variables work right
--    instance C (T a) where
--      type W (T a) = blah
-- The 'a' in the type instance is the one bound by the instance decl
addTyClTyVarBinds tvs m
  = do { let tv_names = hsLKiTyVarNames tvs
       ; env <- dsGetMetaEnv
       ; freshNames <- mkGenSyms (filterOut (`elemNameEnv` env) tv_names)
            -- Make fresh names for the ones that are not already in scope
            -- This makes things work for family declarations

       ; term <- addBinds freshNames $
                 do { kbs <- repList tyVarBndrTyConName mk_tv_bndr (hsQTvBndrs tvs)
                    ; m kbs }

       ; wrapGenSyms freshNames term }
  where
    mk_tv_bndr tv = do { v <- lookupBinder (hsLTyVarName tv)
                       ; repTyVarBndrWithKind tv v }

-- Produce kinded binder constructors from the Haskell tyvar binders
--
repTyVarBndrWithKind :: LHsTyVarBndr Name
                     -> Core TH.Name -> DsM (Core TH.TyVarBndr)
repTyVarBndrWithKind (L _ (UserTyVar _)) nm
  = repPlainTV nm
repTyVarBndrWithKind (L _ (KindedTyVar _ ki)) nm
  = repLKind ki >>= repKindedTV nm

-- | Represent a type variable binder
repTyVarBndr :: LHsTyVarBndr Name -> DsM (Core TH.TyVarBndr)
repTyVarBndr (L _ (UserTyVar nm)) = do { nm' <- lookupBinder nm
                                       ; repPlainTV nm' }
repTyVarBndr (L _ (KindedTyVar (L _ nm) ki)) = do { nm' <- lookupBinder nm
                                                  ; ki' <- repLKind ki
                                                  ; repKindedTV nm' ki' }

-- represent a type context
--
repLContext :: LHsContext Name -> DsM (Core TH.CxtQ)
repLContext (L _ ctxt) = repContext ctxt

repContext :: HsContext Name -> DsM (Core TH.CxtQ)
repContext ctxt = do preds <- repList typeQTyConName repLTy ctxt
                     repCtxt preds

-- yield the representation of a list of types
--
repLTys :: [LHsType Name] -> DsM [Core TH.TypeQ]
repLTys tys = mapM repLTy tys

-- represent a type
--
repLTy :: LHsType Name -> DsM (Core TH.TypeQ)
repLTy (L _ ty) = repTy ty

repTy :: HsType Name -> DsM (Core TH.TypeQ)
repTy (HsForAllTy _ extra tvs ctxt ty)  =
  addTyVarBinds tvs $ \bndrs -> do
    ctxt1  <- repLContext ctxt'
    ty1    <- repLTy ty
    repTForall bndrs ctxt1 ty1
  where
    -- If extra is not Nothing, an extra-constraints wild card was removed
    -- (just) before renaming. It must be put back now, otherwise the
    -- represented type won't include this extra-constraints wild card.
    ctxt'
      | Just loc <- extra
      = let uniq = panic "addExtraCtsWC"
             -- This unique will be discarded by repLContext, but is required
             -- to make a Name
            name = mkInternalName uniq (mkTyVarOcc "_") loc
        in  (++ [L loc (HsWildCardTy (AnonWildCard name))]) `fmap` ctxt
      | otherwise
      = ctxt



repTy (HsTyVar n)
  | isTvOcc occ   = do tv1 <- lookupOcc n
                       repTvar tv1
  | isDataOcc occ = do tc1 <- lookupOcc n
                       repPromotedTyCon tc1
  | otherwise     = do tc1 <- lookupOcc n
                       repNamedTyCon tc1
  where
    occ = nameOccName n

repTy (HsAppTy f a)         = do
                                f1 <- repLTy f
                                a1 <- repLTy a
                                repTapp f1 a1
repTy (HsFunTy f a)         = do
                                f1   <- repLTy f
                                a1   <- repLTy a
                                tcon <- repArrowTyCon
                                repTapps tcon [f1, a1]
repTy (HsListTy t)          = do
                                t1   <- repLTy t
                                tcon <- repListTyCon
                                repTapp tcon t1
repTy (HsPArrTy t)          = do
                                t1   <- repLTy t
                                tcon <- repTy (HsTyVar (tyConName parrTyCon))
                                repTapp tcon t1
repTy (HsTupleTy HsUnboxedTuple tys) = do
                                tys1 <- repLTys tys
                                tcon <- repUnboxedTupleTyCon (length tys)
                                repTapps tcon tys1
repTy (HsTupleTy _ tys)     = do tys1 <- repLTys tys
                                 tcon <- repTupleTyCon (length tys)
                                 repTapps tcon tys1
repTy (HsOpTy ty1 (_, n) ty2) = repLTy ((nlHsTyVar (unLoc n) `nlHsAppTy` ty1)
                                   `nlHsAppTy` ty2)
repTy (HsParTy t)           = repLTy t
repTy (HsEqTy t1 t2) = do
                         t1' <- repLTy t1
                         t2' <- repLTy t2
                         eq  <- repTequality
                         repTapps eq [t1', t2']
repTy (HsKindSig t k)       = do
                                t1 <- repLTy t
                                k1 <- repLKind k
                                repTSig t1 k1
repTy (HsSpliceTy splice _)     = repSplice splice
repTy (HsExplicitListTy _ tys)  = do
                                    tys1 <- repLTys tys
                                    repTPromotedList tys1
repTy (HsExplicitTupleTy _ tys) = do
                                    tys1 <- repLTys tys
                                    tcon <- repPromotedTupleTyCon (length tys)
                                    repTapps tcon tys1
repTy (HsTyLit lit) = do
                        lit' <- repTyLit lit
                        repTLit lit'
repTy (HsWildCardTy (AnonWildCard _)) = repTWildCard
repTy (HsWildCardTy (NamedWildCard n)) = do
                                           nwc <- lookupOcc n
                                           repTNamedWildCard nwc

repTy ty                      = notHandled "Exotic form of type" (ppr ty)

repTyLit :: HsTyLit -> DsM (Core TH.TyLitQ)
repTyLit (HsNumTy _ i) = do iExpr <- mkIntegerExpr i
                            rep2 numTyLitName [iExpr]
repTyLit (HsStrTy _ s) = do { s' <- mkStringExprFS s
                            ; rep2 strTyLitName [s']
                            }

-- represent a kind
--
repLKind :: LHsKind Name -> DsM (Core TH.Kind)
repLKind ki
  = do { let (kis, ki') = splitHsFunType ki
       ; kis_rep <- mapM repLKind kis
       ; ki'_rep <- repNonArrowLKind ki'
       ; kcon <- repKArrow
       ; let f k1 k2 = repKApp kcon k1 >>= flip repKApp k2
       ; foldrM f ki'_rep kis_rep
       }

repNonArrowLKind :: LHsKind Name -> DsM (Core TH.Kind)
repNonArrowLKind (L _ ki) = repNonArrowKind ki

repNonArrowKind :: HsKind Name -> DsM (Core TH.Kind)
repNonArrowKind (HsTyVar name)
  | name == liftedTypeKindTyConName = repKStar
  | name == constraintKindTyConName = repKConstraint
  | isTvOcc (nameOccName name)      = lookupOcc name >>= repKVar
  | otherwise                       = lookupOcc name >>= repKCon
repNonArrowKind (HsAppTy f a)       = do  { f' <- repLKind f
                                          ; a' <- repLKind a
                                          ; repKApp f' a'
                                          }
repNonArrowKind (HsListTy k)        = do  { k' <- repLKind k
                                          ; kcon <- repKList
                                          ; repKApp kcon k'
                                          }
repNonArrowKind (HsTupleTy _ ks)    = do  { ks' <- mapM repLKind ks
                                          ; kcon <- repKTuple (length ks)
                                          ; repKApps kcon ks'
                                          }
repNonArrowKind k                   = notHandled "Exotic form of kind" (ppr k)

repRole :: Located (Maybe Role) -> DsM (Core TH.Role)
repRole (L _ (Just Nominal))          = rep2 nominalRName []
repRole (L _ (Just Representational)) = rep2 representationalRName []
repRole (L _ (Just Phantom))          = rep2 phantomRName []
repRole (L _ Nothing)                 = rep2 inferRName []

-----------------------------------------------------------------------------
--              Splices
-----------------------------------------------------------------------------

repSplice :: HsSplice Name -> DsM (Core a)
-- See Note [How brackets and nested splices are handled] in TcSplice
-- We return a CoreExpr of any old type; the context should know
repSplice (HsTypedSplice   n _)  = rep_splice n
repSplice (HsUntypedSplice n _)  = rep_splice n
repSplice (HsQuasiQuote n _ _ _) = rep_splice n

rep_splice :: Name -> DsM (Core a)
rep_splice splice_name
 = do { mb_val <- dsLookupMetaEnv splice_name
       ; case mb_val of
           Just (DsSplice e) -> do { e' <- dsExpr e
                                   ; return (MkC e') }
           _ -> pprPanic "HsSplice" (ppr splice_name) }
                        -- Should not happen; statically checked

-----------------------------------------------------------------------------
--              Expressions
-----------------------------------------------------------------------------

repLEs :: [LHsExpr Name] -> DsM (Core [TH.ExpQ])
repLEs es = repList expQTyConName repLE es

-- FIXME: some of these panics should be converted into proper error messages
--        unless we can make sure that constructs, which are plainly not
--        supported in TH already lead to error messages at an earlier stage
repLE :: LHsExpr Name -> DsM (Core TH.ExpQ)
repLE (L loc e) = putSrcSpanDs loc (repE e)

repE :: HsExpr Name -> DsM (Core TH.ExpQ)
repE (HsVar x)            =
  do { mb_val <- dsLookupMetaEnv x
     ; case mb_val of
        Nothing          -> do { str <- globalVar x
                               ; repVarOrCon x str }
        Just (DsBound y)   -> repVarOrCon x (coreVar y)
        Just (DsSplice e)  -> do { e' <- dsExpr e
                               ; return (MkC e') } }
repE e@(HsIPVar _) = notHandled "Implicit parameters" (ppr e)

        -- Remember, we're desugaring renamer output here, so
        -- HsOverlit can definitely occur
repE (HsOverLit l) = do { a <- repOverloadedLiteral l; repLit a }
repE (HsLit l)     = do { a <- repLiteral l;           repLit a }
repE (HsLam (MG { mg_alts = [m] })) = repLambda m
repE (HsLamCase _ (MG { mg_alts = ms }))
                   = do { ms' <- mapM repMatchTup ms
                        ; core_ms <- coreList matchQTyConName ms'
                        ; repLamCase core_ms }
repE (HsApp x y)   = do {a <- repLE x; b <- repLE y; repApp a b}

repE (OpApp e1 op _ e2) =
  do { arg1 <- repLE e1;
       arg2 <- repLE e2;
       the_op <- repLE op ;
       repInfixApp arg1 the_op arg2 }
repE (NegApp x _)        = do
                              a         <- repLE x
                              negateVar <- lookupOcc negateName >>= repVar
                              negateVar `repApp` a
repE (HsPar x)            = repLE x
repE (SectionL x y)       = do { a <- repLE x; b <- repLE y; repSectionL a b }
repE (SectionR x y)       = do { a <- repLE x; b <- repLE y; repSectionR a b }
repE (HsCase e (MG { mg_alts = ms }))
                          = do { arg <- repLE e
                               ; ms2 <- mapM repMatchTup ms
                               ; core_ms2 <- coreList matchQTyConName ms2
                               ; repCaseE arg core_ms2 }
repE (HsIf _ x y z)         = do
                              a <- repLE x
                              b <- repLE y
                              c <- repLE z
                              repCond a b c
repE (HsMultiIf _ alts)
  = do { (binds, alts') <- liftM unzip $ mapM repLGRHS alts
       ; expr' <- repMultiIf (nonEmptyCoreList alts')
       ; wrapGenSyms (concat binds) expr' }
repE (HsLet bs e)         = do { (ss,ds) <- repBinds bs
                               ; e2 <- addBinds ss (repLE e)
                               ; z <- repLetE ds e2
                               ; wrapGenSyms ss z }

-- FIXME: I haven't got the types here right yet
repE e@(HsDo ctxt sts _)
 | case ctxt of { DoExpr -> True; GhciStmtCtxt -> True; _ -> False }
 = do { (ss,zs) <- repLSts sts;
        e'      <- repDoE (nonEmptyCoreList zs);
        wrapGenSyms ss e' }

 | ListComp <- ctxt
 = do { (ss,zs) <- repLSts sts;
        e'      <- repComp (nonEmptyCoreList zs);
        wrapGenSyms ss e' }

  | otherwise
  = notHandled "mdo, monad comprehension and [: :]" (ppr e)

repE (ExplicitList _ _ es) = do { xs <- repLEs es; repListExp xs }
repE e@(ExplicitPArr _ _) = notHandled "Parallel arrays" (ppr e)
repE e@(ExplicitTuple es boxed)
  | not (all tupArgPresent es) = notHandled "Tuple sections" (ppr e)
  | isBoxed boxed  = do { xs <- repLEs [e | L _ (Present e) <- es]; repTup xs }
  | otherwise      = do { xs <- repLEs [e | L _ (Present e) <- es]
                        ; repUnboxedTup xs }

repE (RecordCon c _ flds)
 = do { x <- lookupLOcc c;
        fs <- repFields flds;
        repRecCon x fs }
repE (RecordUpd e flds _ _ _)
 = do { x <- repLE e;
        fs <- repFields flds;
        repRecUpd x fs }

repE (ExprWithTySig e ty _) = do { e1 <- repLE e; t1 <- repLTy ty; repSigExp e1 t1 }
repE (ArithSeq _ _ aseq) =
  case aseq of
    From e              -> do { ds1 <- repLE e; repFrom ds1 }
    FromThen e1 e2      -> do
                             ds1 <- repLE e1
                             ds2 <- repLE e2
                             repFromThen ds1 ds2
    FromTo   e1 e2      -> do
                             ds1 <- repLE e1
                             ds2 <- repLE e2
                             repFromTo ds1 ds2
    FromThenTo e1 e2 e3 -> do
                             ds1 <- repLE e1
                             ds2 <- repLE e2
                             ds3 <- repLE e3
                             repFromThenTo ds1 ds2 ds3

repE (HsSpliceE splice)    = repSplice splice
repE (HsStatic e)          = repLE e >>= rep2 staticEName . (:[]) . unC
repE e@(PArrSeq {})        = notHandled "Parallel arrays" (ppr e)
repE e@(HsCoreAnn {})      = notHandled "Core annotations" (ppr e)
repE e@(HsSCC {})          = notHandled "Cost centres" (ppr e)
repE e@(HsTickPragma {})   = notHandled "Tick Pragma" (ppr e)
repE e@(HsTcBracketOut {}) = notHandled "TH brackets" (ppr e)
repE e                     = notHandled "Expression form" (ppr e)

-----------------------------------------------------------------------------
-- Building representations of auxillary structures like Match, Clause, Stmt,

repMatchTup ::  LMatch Name (LHsExpr Name) -> DsM (Core TH.MatchQ)
repMatchTup (L _ (Match _ [p] _ (GRHSs guards wheres))) =
  do { ss1 <- mkGenSyms (collectPatBinders p)
     ; addBinds ss1 $ do {
     ; p1 <- repLP p
     ; (ss2,ds) <- repBinds wheres
     ; addBinds ss2 $ do {
     ; gs    <- repGuards guards
     ; match <- repMatch p1 gs ds
     ; wrapGenSyms (ss1++ss2) match }}}
repMatchTup _ = panic "repMatchTup: case alt with more than one arg"

repClauseTup ::  LMatch Name (LHsExpr Name) -> DsM (Core TH.ClauseQ)
repClauseTup (L _ (Match _ ps _ (GRHSs guards wheres))) =
  do { ss1 <- mkGenSyms (collectPatsBinders ps)
     ; addBinds ss1 $ do {
       ps1 <- repLPs ps
     ; (ss2,ds) <- repBinds wheres
     ; addBinds ss2 $ do {
       gs <- repGuards guards
     ; clause <- repClause ps1 gs ds
     ; wrapGenSyms (ss1++ss2) clause }}}

repGuards ::  [LGRHS Name (LHsExpr Name)] ->  DsM (Core TH.BodyQ)
repGuards [L _ (GRHS [] e)]
  = do {a <- repLE e; repNormal a }
repGuards other
  = do { zs <- mapM repLGRHS other
       ; let (xs, ys) = unzip zs
       ; gd <- repGuarded (nonEmptyCoreList ys)
       ; wrapGenSyms (concat xs) gd }

repLGRHS :: LGRHS Name (LHsExpr Name) -> DsM ([GenSymBind], (Core (TH.Q (TH.Guard, TH.Exp))))
repLGRHS (L _ (GRHS [L _ (BodyStmt e1 _ _ _)] e2))
  = do { guarded <- repLNormalGE e1 e2
       ; return ([], guarded) }
repLGRHS (L _ (GRHS ss rhs))
  = do { (gs, ss') <- repLSts ss
       ; rhs' <- addBinds gs $ repLE rhs
       ; guarded <- repPatGE (nonEmptyCoreList ss') rhs'
       ; return (gs, guarded) }

repFields :: HsRecordBinds Name -> DsM (Core [TH.Q TH.FieldExp])
repFields (HsRecFields { rec_flds = flds })
  = repList fieldExpQTyConName rep_fld flds
  where
    rep_fld (L _ fld) = do { fn <- lookupLOcc (hsRecFieldId fld)
                           ; e  <- repLE (hsRecFieldArg fld)
                           ; repFieldExp fn e }


-----------------------------------------------------------------------------
-- Representing Stmt's is tricky, especially if bound variables
-- shadow each other. Consider:  [| do { x <- f 1; x <- f x; g x } |]
-- First gensym new names for every variable in any of the patterns.
-- both static (x'1 and x'2), and dynamic ((gensym "x") and (gensym "y"))
-- if variables didn't shaddow, the static gensym wouldn't be necessary
-- and we could reuse the original names (x and x).
--
-- do { x'1 <- gensym "x"
--    ; x'2 <- gensym "x"
--    ; doE [ BindSt (pvar x'1) [| f 1 |]
--          , BindSt (pvar x'2) [| f x |]
--          , NoBindSt [| g x |]
--          ]
--    }

-- The strategy is to translate a whole list of do-bindings by building a
-- bigger environment, and a bigger set of meta bindings
-- (like:  x'1 <- gensym "x" ) and then combining these with the translations
-- of the expressions within the Do

-----------------------------------------------------------------------------
-- The helper function repSts computes the translation of each sub expression
-- and a bunch of prefix bindings denoting the dynamic renaming.

repLSts :: [LStmt Name (LHsExpr Name)] -> DsM ([GenSymBind], [Core TH.StmtQ])
repLSts stmts = repSts (map unLoc stmts)

repSts :: [Stmt Name (LHsExpr Name)] -> DsM ([GenSymBind], [Core TH.StmtQ])
repSts (BindStmt p e _ _ : ss) =
   do { e2 <- repLE e
      ; ss1 <- mkGenSyms (collectPatBinders p)
      ; addBinds ss1 $ do {
      ; p1 <- repLP p;
      ; (ss2,zs) <- repSts ss
      ; z <- repBindSt p1 e2
      ; return (ss1++ss2, z : zs) }}
repSts (LetStmt bs : ss) =
   do { (ss1,ds) <- repBinds bs
      ; z <- repLetSt ds
      ; (ss2,zs) <- addBinds ss1 (repSts ss)
      ; return (ss1++ss2, z : zs) }
repSts (BodyStmt e _ _ _ : ss) =
   do { e2 <- repLE e
      ; z <- repNoBindSt e2
      ; (ss2,zs) <- repSts ss
      ; return (ss2, z : zs) }
repSts (ParStmt stmt_blocks _ _ : ss) =
   do { (ss_s, stmt_blocks1) <- mapAndUnzipM rep_stmt_block stmt_blocks
      ; let stmt_blocks2 = nonEmptyCoreList stmt_blocks1
            ss1 = concat ss_s
      ; z <- repParSt stmt_blocks2
      ; (ss2, zs) <- addBinds ss1 (repSts ss)
      ; return (ss1++ss2, z : zs) }
   where
     rep_stmt_block :: ParStmtBlock Name Name -> DsM ([GenSymBind], Core [TH.StmtQ])
     rep_stmt_block (ParStmtBlock stmts _ _) =
       do { (ss1, zs) <- repSts (map unLoc stmts)
          ; zs1 <- coreList stmtQTyConName zs
          ; return (ss1, zs1) }
repSts [LastStmt e _ _]
  = do { e2 <- repLE e
       ; z <- repNoBindSt e2
       ; return ([], [z]) }
repSts []    = return ([],[])
repSts other = notHandled "Exotic statement" (ppr other)


-----------------------------------------------------------
--                      Bindings
-----------------------------------------------------------

repBinds :: HsLocalBinds Name -> DsM ([GenSymBind], Core [TH.DecQ])
repBinds EmptyLocalBinds
  = do  { core_list <- coreList decQTyConName []
        ; return ([], core_list) }

repBinds b@(HsIPBinds _) = notHandled "Implicit parameters" (ppr b)

repBinds (HsValBinds decs)
 = do   { let { bndrs = hsSigTvBinders decs ++ collectHsValBinders decs }
                -- No need to worrry about detailed scopes within
                -- the binding group, because we are talking Names
                -- here, so we can safely treat it as a mutually
                -- recursive group
                -- For hsSigTvBinders see Note [Scoped type variables in bindings]
        ; ss        <- mkGenSyms bndrs
        ; prs       <- addBinds ss (rep_val_binds decs)
        ; core_list <- coreList decQTyConName
                                (de_loc (sort_by_loc prs))
        ; return (ss, core_list) }

rep_val_binds :: HsValBinds Name -> DsM [(SrcSpan, Core TH.DecQ)]
-- Assumes: all the binders of the binding are alrady in the meta-env
rep_val_binds (ValBindsOut binds sigs)
 = do { core1 <- rep_binds' (unionManyBags (map snd binds))
      ; core2 <- rep_sigs' sigs
      ; return (core1 ++ core2) }
rep_val_binds (ValBindsIn _ _)
 = panic "rep_val_binds: ValBindsIn"

rep_binds :: LHsBinds Name -> DsM [Core TH.DecQ]
rep_binds binds = do { binds_w_locs <- rep_binds' binds
                     ; return (de_loc (sort_by_loc binds_w_locs)) }

rep_binds' :: LHsBinds Name -> DsM [(SrcSpan, Core TH.DecQ)]
rep_binds' = mapM rep_bind . bagToList

rep_bind :: LHsBind Name -> DsM (SrcSpan, Core TH.DecQ)
-- Assumes: all the binders of the binding are alrady in the meta-env

-- Note GHC treats declarations of a variable (not a pattern)
-- e.g.  x = g 5 as a Fun MonoBinds. This is indicated by a single match
-- with an empty list of patterns
rep_bind (L loc (FunBind
                 { fun_id = fn,
                   fun_matches = MG { mg_alts = [L _ (Match _ [] _
                                                   (GRHSs guards wheres))] } }))
 = do { (ss,wherecore) <- repBinds wheres
        ; guardcore <- addBinds ss (repGuards guards)
        ; fn'  <- lookupLBinder fn
        ; p    <- repPvar fn'
        ; ans  <- repVal p guardcore wherecore
        ; ans' <- wrapGenSyms ss ans
        ; return (loc, ans') }

rep_bind (L loc (FunBind { fun_id = fn, fun_matches = MG { mg_alts = ms } }))
 =   do { ms1 <- mapM repClauseTup ms
        ; fn' <- lookupLBinder fn
        ; ans <- repFun fn' (nonEmptyCoreList ms1)
        ; return (loc, ans) }

rep_bind (L loc (PatBind { pat_lhs = pat, pat_rhs = GRHSs guards wheres }))
 =   do { patcore <- repLP pat
        ; (ss,wherecore) <- repBinds wheres
        ; guardcore <- addBinds ss (repGuards guards)
        ; ans  <- repVal patcore guardcore wherecore
        ; ans' <- wrapGenSyms ss ans
        ; return (loc, ans') }

rep_bind (L _ (VarBind { var_id = v, var_rhs = e}))
 =   do { v' <- lookupBinder v
        ; e2 <- repLE e
        ; x <- repNormal e2
        ; patcore <- repPvar v'
        ; empty_decls <- coreList decQTyConName []
        ; ans <- repVal patcore x empty_decls
        ; return (srcLocSpan (getSrcLoc v), ans) }

rep_bind (L _ (AbsBinds {}))  = panic "rep_bind: AbsBinds"
rep_bind (L _ dec@(PatSynBind {})) = notHandled "pattern synonyms" (ppr dec)
-----------------------------------------------------------------------------
-- Since everything in a Bind is mutually recursive we need rename all
-- all the variables simultaneously. For example:
-- [| AndMonoBinds (f x = x + g 2) (g x = f 1 + 2) |] would translate to
-- do { f'1 <- gensym "f"
--    ; g'2 <- gensym "g"
--    ; [ do { x'3 <- gensym "x"; fun f'1 [pvar x'3] [| x + g2 |]},
--        do { x'4 <- gensym "x"; fun g'2 [pvar x'4] [| f 1 + 2 |]}
--      ]}
-- This requires collecting the bindings (f'1 <- gensym "f"), and the
-- environment ( f |-> f'1 ) from each binding, and then unioning them
-- together. As we do this we collect GenSymBinds's which represent the renamed
-- variables bound by the Bindings. In order not to lose track of these
-- representations we build a shadow datatype MB with the same structure as
-- MonoBinds, but which has slots for the representations


-----------------------------------------------------------------------------
-- GHC allows a more general form of lambda abstraction than specified
-- by Haskell 98. In particular it allows guarded lambda's like :
-- (\  x | even x -> 0 | odd x -> 1) at the moment we can't represent this in
-- Haskell Template's Meta.Exp type so we punt if it isn't a simple thing like
-- (\ p1 .. pn -> exp) by causing an error.

repLambda :: LMatch Name (LHsExpr Name) -> DsM (Core TH.ExpQ)
repLambda (L _ (Match _ ps _ (GRHSs [L _ (GRHS [] e)] EmptyLocalBinds)))
 = do { let bndrs = collectPatsBinders ps ;
      ; ss  <- mkGenSyms bndrs
      ; lam <- addBinds ss (
                do { xs <- repLPs ps; body <- repLE e; repLam xs body })
      ; wrapGenSyms ss lam }

repLambda (L _ m) = notHandled "Guarded labmdas" (pprMatch (LambdaExpr :: HsMatchContext Name) m)


-----------------------------------------------------------------------------
--                      Patterns
-- repP deals with patterns.  It assumes that we have already
-- walked over the pattern(s) once to collect the binders, and
-- have extended the environment.  So every pattern-bound
-- variable should already appear in the environment.

-- Process a list of patterns
repLPs :: [LPat Name] -> DsM (Core [TH.PatQ])
repLPs ps = repList patQTyConName repLP ps

repLP :: LPat Name -> DsM (Core TH.PatQ)
repLP (L _ p) = repP p

repP :: Pat Name -> DsM (Core TH.PatQ)
repP (WildPat _)       = repPwild
repP (LitPat l)        = do { l2 <- repLiteral l; repPlit l2 }
repP (VarPat x)        = do { x' <- lookupBinder x; repPvar x' }
repP (LazyPat p)       = do { p1 <- repLP p; repPtilde p1 }
repP (BangPat p)       = do { p1 <- repLP p; repPbang p1 }
repP (AsPat x p)       = do { x' <- lookupLBinder x; p1 <- repLP p; repPaspat x' p1 }
repP (ParPat p)        = repLP p
repP (ListPat ps _ Nothing)    = do { qs <- repLPs ps; repPlist qs }
repP (ListPat ps ty1 (Just (_,e))) = do { p <- repP (ListPat ps ty1 Nothing); e' <- repE e; repPview e' p}
repP (TuplePat ps boxed _)
  | isBoxed boxed       = do { qs <- repLPs ps; repPtup qs }
  | otherwise           = do { qs <- repLPs ps; repPunboxedTup qs }
repP (ConPatIn dc details)
 = do { con_str <- lookupLOcc dc
      ; case details of
         PrefixCon ps -> do { qs <- repLPs ps; repPcon con_str qs }
         RecCon rec   -> do { fps <- repList fieldPatQTyConName rep_fld (rec_flds rec)
                            ; repPrec con_str fps }
         InfixCon p1 p2 -> do { p1' <- repLP p1;
                                p2' <- repLP p2;
                                repPinfix p1' con_str p2' }
   }
 where
   rep_fld (L _ fld) = do { MkC v <- lookupLOcc (hsRecFieldId fld)
                          ; MkC p <- repLP (hsRecFieldArg fld)
                          ; rep2 fieldPatName [v,p] }

repP (NPat (L _ l) Nothing _)  = do { a <- repOverloadedLiteral l; repPlit a }
repP (ViewPat e p _) = do { e' <- repLE e; p' <- repLP p; repPview e' p' }
repP p@(NPat _ (Just _) _) = notHandled "Negative overloaded patterns" (ppr p)
repP p@(SigPatIn {})  = notHandled "Type signatures in patterns" (ppr p)
        -- The problem is to do with scoped type variables.
        -- To implement them, we have to implement the scoping rules
        -- here in DsMeta, and I don't want to do that today!
        --       do { p' <- repLP p; t' <- repLTy t; repPsig p' t' }
        --      repPsig :: Core TH.PatQ -> Core TH.TypeQ -> DsM (Core TH.PatQ)
        --      repPsig (MkC p) (MkC t) = rep2 sigPName [p, t]

repP (SplicePat splice) = repSplice splice

repP other = notHandled "Exotic pattern" (ppr other)

----------------------------------------------------------
-- Declaration ordering helpers

sort_by_loc :: [(SrcSpan, a)] -> [(SrcSpan, a)]
sort_by_loc xs = sortBy comp xs
    where comp x y = compare (fst x) (fst y)

de_loc :: [(a, b)] -> [b]
de_loc = map snd

----------------------------------------------------------
--      The meta-environment

-- A name/identifier association for fresh names of locally bound entities
type GenSymBind = (Name, Id)    -- Gensym the string and bind it to the Id
                                -- I.e.         (x, x_id) means
                                --      let x_id = gensym "x" in ...

-- Generate a fresh name for a locally bound entity

mkGenSyms :: [Name] -> DsM [GenSymBind]
-- We can use the existing name.  For example:
--      [| \x_77 -> x_77 + x_77 |]
-- desugars to
--      do { x_77 <- genSym "x"; .... }
-- We use the same x_77 in the desugared program, but with the type Bndr
-- instead of Int
--
-- We do make it an Internal name, though (hence localiseName)
--
-- Nevertheless, it's monadic because we have to generate nameTy
mkGenSyms ns = do { var_ty <- lookupType nameTyConName
                  ; return [(nm, mkLocalId (localiseName nm) var_ty) | nm <- ns] }


addBinds :: [GenSymBind] -> DsM a -> DsM a
-- Add a list of fresh names for locally bound entities to the
-- meta environment (which is part of the state carried around
-- by the desugarer monad)
addBinds bs m = dsExtendMetaEnv (mkNameEnv [(n,DsBound id) | (n,id) <- bs]) m

dupBinder :: (Name, Name) -> DsM (Name, DsMetaVal)
dupBinder (new, old)
  = do { mb_val <- dsLookupMetaEnv old
       ; case mb_val of
           Just val -> return (new, val)
           Nothing  -> pprPanic "dupBinder" (ppr old) }

-- Look up a locally bound name
--
lookupLBinder :: Located Name -> DsM (Core TH.Name)
lookupLBinder (L _ n) = lookupBinder n

lookupBinder :: Name -> DsM (Core TH.Name)
lookupBinder = lookupOcc
  -- Binders are brought into scope before the pattern or what-not is
  -- desugared.  Moreover, in instance declaration the binder of a method
  -- will be the selector Id and hence a global; so we need the
  -- globalVar case of lookupOcc

-- Look up a name that is either locally bound or a global name
--
--  * If it is a global name, generate the "original name" representation (ie,
--   the <module>:<name> form) for the associated entity
--
lookupLOcc :: Located Name -> DsM (Core TH.Name)
-- Lookup an occurrence; it can't be a splice.
-- Use the in-scope bindings if they exist
lookupLOcc (L _ n) = lookupOcc n

lookupOcc :: Name -> DsM (Core TH.Name)
lookupOcc n
  = do {  mb_val <- dsLookupMetaEnv n ;
          case mb_val of
                Nothing           -> globalVar n
                Just (DsBound x)  -> return (coreVar x)
                Just (DsSplice _) -> pprPanic "repE:lookupOcc" (ppr n)
    }

globalVar :: Name -> DsM (Core TH.Name)
-- Not bound by the meta-env
-- Could be top-level; or could be local
--      f x = $(g [| x |])
-- Here the x will be local
globalVar name
  | isExternalName name
  = do  { MkC mod <- coreStringLit name_mod
        ; MkC pkg <- coreStringLit name_pkg
        ; MkC occ <- occNameLit name
        ; rep2 mk_varg [pkg,mod,occ] }
  | otherwise
  = do  { MkC occ <- occNameLit name
        ; MkC uni <- coreIntLit (getKey (getUnique name))
        ; rep2 mkNameLName [occ,uni] }
  where
      mod = ASSERT( isExternalName name) nameModule name
      name_mod = moduleNameString (moduleName mod)
      name_pkg = packageKeyString (modulePackageKey mod)
      name_occ = nameOccName name
      mk_varg | OccName.isDataOcc name_occ = mkNameG_dName
              | OccName.isVarOcc  name_occ = mkNameG_vName
              | OccName.isTcOcc   name_occ = mkNameG_tcName
              | otherwise                  = pprPanic "DsMeta.globalVar" (ppr name)

lookupType :: Name      -- Name of type constructor (e.g. TH.ExpQ)
           -> DsM Type  -- The type
lookupType tc_name = do { tc <- dsLookupTyCon tc_name ;
                          return (mkTyConApp tc []) }

wrapGenSyms :: [GenSymBind]
            -> Core (TH.Q a) -> DsM (Core (TH.Q a))
-- wrapGenSyms [(nm1,id1), (nm2,id2)] y
--      --> bindQ (gensym nm1) (\ id1 ->
--          bindQ (gensym nm2 (\ id2 ->
--          y))

wrapGenSyms binds body@(MkC b)
  = do  { var_ty <- lookupType nameTyConName
        ; go var_ty binds }
  where
    [elt_ty] = tcTyConAppArgs (exprType b)
        -- b :: Q a, so we can get the type 'a' by looking at the
        -- argument type. NB: this relies on Q being a data/newtype,
        -- not a type synonym

    go _ [] = return body
    go var_ty ((name,id) : binds)
      = do { MkC body'  <- go var_ty binds
           ; lit_str    <- occNameLit name
           ; gensym_app <- repGensym lit_str
           ; repBindQ var_ty elt_ty
                      gensym_app (MkC (Lam id body')) }

occNameLit :: Name -> DsM (Core String)
occNameLit n = coreStringLit (occNameString (nameOccName n))


-- %*********************************************************************
-- %*                                                                   *
--              Constructing code
-- %*                                                                   *
-- %*********************************************************************

-----------------------------------------------------------------------------
-- PHANTOM TYPES for consistency. In order to make sure we do this correct
-- we invent a new datatype which uses phantom types.

newtype Core a = MkC CoreExpr
unC :: Core a -> CoreExpr
unC (MkC x) = x

rep2 :: Name -> [ CoreExpr ] -> DsM (Core a)
rep2 n xs = do { id <- dsLookupGlobalId n
               ; return (MkC (foldl App (Var id) xs)) }

dataCon' :: Name -> [CoreExpr] -> DsM (Core a)
dataCon' n args = do { id <- dsLookupDataCon n
                     ; return $ MkC $ mkCoreConApps id args }

dataCon :: Name -> DsM (Core a)
dataCon n = dataCon' n []

-- Then we make "repConstructors" which use the phantom types for each of the
-- smart constructors of the Meta.Meta datatypes.


-- %*********************************************************************
-- %*                                                                   *
--              The 'smart constructors'
-- %*                                                                   *
-- %*********************************************************************

--------------- Patterns -----------------
repPlit   :: Core TH.Lit -> DsM (Core TH.PatQ)
repPlit (MkC l) = rep2 litPName [l]

repPvar :: Core TH.Name -> DsM (Core TH.PatQ)
repPvar (MkC s) = rep2 varPName [s]

repPtup :: Core [TH.PatQ] -> DsM (Core TH.PatQ)
repPtup (MkC ps) = rep2 tupPName [ps]

repPunboxedTup :: Core [TH.PatQ] -> DsM (Core TH.PatQ)
repPunboxedTup (MkC ps) = rep2 unboxedTupPName [ps]

repPcon   :: Core TH.Name -> Core [TH.PatQ] -> DsM (Core TH.PatQ)
repPcon (MkC s) (MkC ps) = rep2 conPName [s, ps]

repPrec   :: Core TH.Name -> Core [(TH.Name,TH.PatQ)] -> DsM (Core TH.PatQ)
repPrec (MkC c) (MkC rps) = rep2 recPName [c,rps]

repPinfix :: Core TH.PatQ -> Core TH.Name -> Core TH.PatQ -> DsM (Core TH.PatQ)
repPinfix (MkC p1) (MkC n) (MkC p2) = rep2 infixPName [p1, n, p2]

repPtilde :: Core TH.PatQ -> DsM (Core TH.PatQ)
repPtilde (MkC p) = rep2 tildePName [p]

repPbang :: Core TH.PatQ -> DsM (Core TH.PatQ)
repPbang (MkC p) = rep2 bangPName [p]

repPaspat :: Core TH.Name -> Core TH.PatQ -> DsM (Core TH.PatQ)
repPaspat (MkC s) (MkC p) = rep2 asPName [s, p]

repPwild  :: DsM (Core TH.PatQ)
repPwild = rep2 wildPName []

repPlist :: Core [TH.PatQ] -> DsM (Core TH.PatQ)
repPlist (MkC ps) = rep2 listPName [ps]

repPview :: Core TH.ExpQ -> Core TH.PatQ -> DsM (Core TH.PatQ)
repPview (MkC e) (MkC p) = rep2 viewPName [e,p]

--------------- Expressions -----------------
repVarOrCon :: Name -> Core TH.Name -> DsM (Core TH.ExpQ)
repVarOrCon vc str | isDataOcc (nameOccName vc) = repCon str
                   | otherwise                  = repVar str

repVar :: Core TH.Name -> DsM (Core TH.ExpQ)
repVar (MkC s) = rep2 varEName [s]

repCon :: Core TH.Name -> DsM (Core TH.ExpQ)
repCon (MkC s) = rep2 conEName [s]

repLit :: Core TH.Lit -> DsM (Core TH.ExpQ)
repLit (MkC c) = rep2 litEName [c]

repApp :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repApp (MkC x) (MkC y) = rep2 appEName [x,y]

repLam :: Core [TH.PatQ] -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repLam (MkC ps) (MkC e) = rep2 lamEName [ps, e]

repLamCase :: Core [TH.MatchQ] -> DsM (Core TH.ExpQ)
repLamCase (MkC ms) = rep2 lamCaseEName [ms]

repTup :: Core [TH.ExpQ] -> DsM (Core TH.ExpQ)
repTup (MkC es) = rep2 tupEName [es]

repUnboxedTup :: Core [TH.ExpQ] -> DsM (Core TH.ExpQ)
repUnboxedTup (MkC es) = rep2 unboxedTupEName [es]

repCond :: Core TH.ExpQ -> Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repCond (MkC x) (MkC y) (MkC z) = rep2 condEName [x,y,z]

repMultiIf :: Core [TH.Q (TH.Guard, TH.Exp)] -> DsM (Core TH.ExpQ)
repMultiIf (MkC alts) = rep2 multiIfEName [alts]

repLetE :: Core [TH.DecQ] -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repLetE (MkC ds) (MkC e) = rep2 letEName [ds, e]

repCaseE :: Core TH.ExpQ -> Core [TH.MatchQ] -> DsM( Core TH.ExpQ)
repCaseE (MkC e) (MkC ms) = rep2 caseEName [e, ms]

repDoE :: Core [TH.StmtQ] -> DsM (Core TH.ExpQ)
repDoE (MkC ss) = rep2 doEName [ss]

repComp :: Core [TH.StmtQ] -> DsM (Core TH.ExpQ)
repComp (MkC ss) = rep2 compEName [ss]

repListExp :: Core [TH.ExpQ] -> DsM (Core TH.ExpQ)
repListExp (MkC es) = rep2 listEName [es]

repSigExp :: Core TH.ExpQ -> Core TH.TypeQ -> DsM (Core TH.ExpQ)
repSigExp (MkC e) (MkC t) = rep2 sigEName [e,t]

repRecCon :: Core TH.Name -> Core [TH.Q TH.FieldExp]-> DsM (Core TH.ExpQ)
repRecCon (MkC c) (MkC fs) = rep2 recConEName [c,fs]

repRecUpd :: Core TH.ExpQ -> Core [TH.Q TH.FieldExp] -> DsM (Core TH.ExpQ)
repRecUpd (MkC e) (MkC fs) = rep2 recUpdEName [e,fs]

repFieldExp :: Core TH.Name -> Core TH.ExpQ -> DsM (Core (TH.Q TH.FieldExp))
repFieldExp (MkC n) (MkC x) = rep2 fieldExpName [n,x]

repInfixApp :: Core TH.ExpQ -> Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repInfixApp (MkC x) (MkC y) (MkC z) = rep2 infixAppName [x,y,z]

repSectionL :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repSectionL (MkC x) (MkC y) = rep2 sectionLName [x,y]

repSectionR :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repSectionR (MkC x) (MkC y) = rep2 sectionRName [x,y]

------------ Right hand sides (guarded expressions) ----
repGuarded :: Core [TH.Q (TH.Guard, TH.Exp)] -> DsM (Core TH.BodyQ)
repGuarded (MkC pairs) = rep2 guardedBName [pairs]

repNormal :: Core TH.ExpQ -> DsM (Core TH.BodyQ)
repNormal (MkC e) = rep2 normalBName [e]

------------ Guards ----
repLNormalGE :: LHsExpr Name -> LHsExpr Name -> DsM (Core (TH.Q (TH.Guard, TH.Exp)))
repLNormalGE g e = do g' <- repLE g
                      e' <- repLE e
                      repNormalGE g' e'

repNormalGE :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core (TH.Q (TH.Guard, TH.Exp)))
repNormalGE (MkC g) (MkC e) = rep2 normalGEName [g, e]

repPatGE :: Core [TH.StmtQ] -> Core TH.ExpQ -> DsM (Core (TH.Q (TH.Guard, TH.Exp)))
repPatGE (MkC ss) (MkC e) = rep2 patGEName [ss, e]

------------- Stmts -------------------
repBindSt :: Core TH.PatQ -> Core TH.ExpQ -> DsM (Core TH.StmtQ)
repBindSt (MkC p) (MkC e) = rep2 bindSName [p,e]

repLetSt :: Core [TH.DecQ] -> DsM (Core TH.StmtQ)
repLetSt (MkC ds) = rep2 letSName [ds]

repNoBindSt :: Core TH.ExpQ -> DsM (Core TH.StmtQ)
repNoBindSt (MkC e) = rep2 noBindSName [e]

repParSt :: Core [[TH.StmtQ]] -> DsM (Core TH.StmtQ)
repParSt (MkC sss) = rep2 parSName [sss]

-------------- Range (Arithmetic sequences) -----------
repFrom :: Core TH.ExpQ -> DsM (Core TH.ExpQ)
repFrom (MkC x) = rep2 fromEName [x]

repFromThen :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repFromThen (MkC x) (MkC y) = rep2 fromThenEName [x,y]

repFromTo :: Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repFromTo (MkC x) (MkC y) = rep2 fromToEName [x,y]

repFromThenTo :: Core TH.ExpQ -> Core TH.ExpQ -> Core TH.ExpQ -> DsM (Core TH.ExpQ)
repFromThenTo (MkC x) (MkC y) (MkC z) = rep2 fromThenToEName [x,y,z]

------------ Match and Clause Tuples -----------
repMatch :: Core TH.PatQ -> Core TH.BodyQ -> Core [TH.DecQ] -> DsM (Core TH.MatchQ)
repMatch (MkC p) (MkC bod) (MkC ds) = rep2 matchName [p, bod, ds]

repClause :: Core [TH.PatQ] -> Core TH.BodyQ -> Core [TH.DecQ] -> DsM (Core TH.ClauseQ)
repClause (MkC ps) (MkC bod) (MkC ds) = rep2 clauseName [ps, bod, ds]

-------------- Dec -----------------------------
repVal :: Core TH.PatQ -> Core TH.BodyQ -> Core [TH.DecQ] -> DsM (Core TH.DecQ)
repVal (MkC p) (MkC b) (MkC ds) = rep2 valDName [p, b, ds]

repFun :: Core TH.Name -> Core [TH.ClauseQ] -> DsM (Core TH.DecQ)
repFun (MkC nm) (MkC b) = rep2 funDName [nm, b]

repData :: Core TH.CxtQ -> Core TH.Name -> Core [TH.TyVarBndr]
        -> Maybe (Core [TH.TypeQ])
        -> Core [TH.ConQ] -> Core [TH.Name] -> DsM (Core TH.DecQ)
repData (MkC cxt) (MkC nm) (MkC tvs) Nothing (MkC cons) (MkC derivs)
  = rep2 dataDName [cxt, nm, tvs, cons, derivs]
repData (MkC cxt) (MkC nm) (MkC _) (Just (MkC tys)) (MkC cons) (MkC derivs)
  = rep2 dataInstDName [cxt, nm, tys, cons, derivs]

repNewtype :: Core TH.CxtQ -> Core TH.Name -> Core [TH.TyVarBndr]
           -> Maybe (Core [TH.TypeQ])
           -> Core TH.ConQ -> Core [TH.Name] -> DsM (Core TH.DecQ)
repNewtype (MkC cxt) (MkC nm) (MkC tvs) Nothing (MkC con) (MkC derivs)
  = rep2 newtypeDName [cxt, nm, tvs, con, derivs]
repNewtype (MkC cxt) (MkC nm) (MkC _) (Just (MkC tys)) (MkC con) (MkC derivs)
  = rep2 newtypeInstDName [cxt, nm, tys, con, derivs]

repTySyn :: Core TH.Name -> Core [TH.TyVarBndr]
         -> Core TH.TypeQ -> DsM (Core TH.DecQ)
repTySyn (MkC nm) (MkC tvs) (MkC rhs)
  = rep2 tySynDName [nm, tvs, rhs]

repInst :: Core TH.CxtQ -> Core TH.TypeQ -> Core [TH.DecQ] -> DsM (Core TH.DecQ)
repInst (MkC cxt) (MkC ty) (MkC ds) = rep2 instanceDName [cxt, ty, ds]

repClass :: Core TH.CxtQ -> Core TH.Name -> Core [TH.TyVarBndr]
         -> Core [TH.FunDep] -> Core [TH.DecQ]
         -> DsM (Core TH.DecQ)
repClass (MkC cxt) (MkC cls) (MkC tvs) (MkC fds) (MkC ds)
  = rep2 classDName [cxt, cls, tvs, fds, ds]

repDeriv :: Core TH.CxtQ -> Core TH.TypeQ -> DsM (Core TH.DecQ)
repDeriv (MkC cxt) (MkC ty) = rep2 standaloneDerivDName [cxt, ty]

repPragInl :: Core TH.Name -> Core TH.Inline -> Core TH.RuleMatch
           -> Core TH.Phases -> DsM (Core TH.DecQ)
repPragInl (MkC nm) (MkC inline) (MkC rm) (MkC phases)
  = rep2 pragInlDName [nm, inline, rm, phases]

repPragSpec :: Core TH.Name -> Core TH.TypeQ -> Core TH.Phases
            -> DsM (Core TH.DecQ)
repPragSpec (MkC nm) (MkC ty) (MkC phases)
  = rep2 pragSpecDName [nm, ty, phases]

repPragSpecInl :: Core TH.Name -> Core TH.TypeQ -> Core TH.Inline
               -> Core TH.Phases -> DsM (Core TH.DecQ)
repPragSpecInl (MkC nm) (MkC ty) (MkC inline) (MkC phases)
  = rep2 pragSpecInlDName [nm, ty, inline, phases]

repPragSpecInst :: Core TH.TypeQ -> DsM (Core TH.DecQ)
repPragSpecInst (MkC ty) = rep2 pragSpecInstDName [ty]

repPragRule :: Core String -> Core [TH.RuleBndrQ] -> Core TH.ExpQ
            -> Core TH.ExpQ -> Core TH.Phases -> DsM (Core TH.DecQ)
repPragRule (MkC nm) (MkC bndrs) (MkC lhs) (MkC rhs) (MkC phases)
  = rep2 pragRuleDName [nm, bndrs, lhs, rhs, phases]

repPragAnn :: Core TH.AnnTarget -> Core TH.ExpQ -> DsM (Core TH.DecQ)
repPragAnn (MkC targ) (MkC e) = rep2 pragAnnDName [targ, e]

repTySynInst :: Core TH.Name -> Core TH.TySynEqnQ -> DsM (Core TH.DecQ)
repTySynInst (MkC nm) (MkC eqn)
    = rep2 tySynInstDName [nm, eqn]

repDataFamilyD :: Core TH.Name -> Core [TH.TyVarBndr]
               -> Core (Maybe TH.Kind) -> DsM (Core TH.DecQ)
repDataFamilyD (MkC nm) (MkC tvs) (MkC kind)
    = rep2 dataFamilyDName [nm, tvs, kind]

repOpenFamilyD :: Core TH.Name
               -> Core [TH.TyVarBndr]
               -> Core TH.FamilyResultSig
               -> Core (Maybe TH.InjectivityAnn)
               -> DsM (Core TH.DecQ)
repOpenFamilyD (MkC nm) (MkC tvs) (MkC result) (MkC inj)
    = rep2 openTypeFamilyDName [nm, tvs, result, inj]

repClosedFamilyD :: Core TH.Name
                 -> Core [TH.TyVarBndr]
                 -> Core TH.FamilyResultSig
                 -> Core (Maybe TH.InjectivityAnn)
                 -> Core [TH.TySynEqnQ]
                 -> DsM (Core TH.DecQ)
repClosedFamilyD (MkC nm) (MkC tvs) (MkC res) (MkC inj) (MkC eqns)
    = rep2 closedTypeFamilyDName [nm, tvs, res, inj, eqns]

repTySynEqn :: Core [TH.TypeQ] -> Core TH.TypeQ -> DsM (Core TH.TySynEqnQ)
repTySynEqn (MkC lhs) (MkC rhs)
  = rep2 tySynEqnName [lhs, rhs]

repRoleAnnotD :: Core TH.Name -> Core [TH.Role] -> DsM (Core TH.DecQ)
repRoleAnnotD (MkC n) (MkC roles) = rep2 roleAnnotDName [n, roles]

repFunDep :: Core [TH.Name] -> Core [TH.Name] -> DsM (Core TH.FunDep)
repFunDep (MkC xs) (MkC ys) = rep2 funDepName [xs, ys]

repProto :: Name -> Core TH.Name -> Core TH.TypeQ -> DsM (Core TH.DecQ)
repProto mk_sig (MkC s) (MkC ty) = rep2 mk_sig [s, ty]

repCtxt :: Core [TH.PredQ] -> DsM (Core TH.CxtQ)
repCtxt (MkC tys) = rep2 cxtName [tys]

repConstr :: Core TH.Name -> HsConDeclDetails Name
          -> DsM (Core TH.ConQ)
repConstr con (PrefixCon ps)
    = do arg_tys  <- repList strictTypeQTyConName repBangTy ps
         rep2 normalCName [unC con, unC arg_tys]

repConstr con (RecCon (L _ ips))
    = do { args <- concatMapM rep_ip ips
         ; arg_vtys <- coreList varStrictTypeQTyConName args
         ; rep2 recCName [unC con, unC arg_vtys] }
    where
      rep_ip (L _ ip) = mapM (rep_one_ip (cd_fld_type ip)) (cd_fld_names ip)
      rep_one_ip t n = do { MkC v  <- lookupLOcc n
                          ; MkC ty <- repBangTy  t
                          ; rep2 varStrictTypeName [v,ty] }

repConstr con (InfixCon st1 st2)
    = do arg1 <- repBangTy st1
         arg2 <- repBangTy st2
         rep2 infixCName [unC arg1, unC con, unC arg2]

------------ Types -------------------

repTForall :: Core [TH.TyVarBndr] -> Core TH.CxtQ -> Core TH.TypeQ
           -> DsM (Core TH.TypeQ)
repTForall (MkC tvars) (MkC ctxt) (MkC ty)
    = rep2 forallTName [tvars, ctxt, ty]

repTvar :: Core TH.Name -> DsM (Core TH.TypeQ)
repTvar (MkC s) = rep2 varTName [s]

repTapp :: Core TH.TypeQ -> Core TH.TypeQ -> DsM (Core TH.TypeQ)
repTapp (MkC t1) (MkC t2) = rep2 appTName [t1, t2]

repTapps :: Core TH.TypeQ -> [Core TH.TypeQ] -> DsM (Core TH.TypeQ)
repTapps f []     = return f
repTapps f (t:ts) = do { f1 <- repTapp f t; repTapps f1 ts }

repTSig :: Core TH.TypeQ -> Core TH.Kind -> DsM (Core TH.TypeQ)
repTSig (MkC ty) (MkC ki) = rep2 sigTName [ty, ki]

repTequality :: DsM (Core TH.TypeQ)
repTequality = rep2 equalityTName []

repTPromotedList :: [Core TH.TypeQ] -> DsM (Core TH.TypeQ)
repTPromotedList []     = repPromotedNilTyCon
repTPromotedList (t:ts) = do  { tcon <- repPromotedConsTyCon
                              ; f <- repTapp tcon t
                              ; t' <- repTPromotedList ts
                              ; repTapp f t'
                              }

repTLit :: Core TH.TyLitQ -> DsM (Core TH.TypeQ)
repTLit (MkC lit) = rep2 litTName [lit]

repTWildCard :: DsM (Core TH.TypeQ)
repTWildCard = rep2 wildCardTName []

repTNamedWildCard :: Core TH.Name -> DsM (Core TH.TypeQ)
repTNamedWildCard (MkC s) = rep2 namedWildCardTName [s]


--------- Type constructors --------------

repNamedTyCon :: Core TH.Name -> DsM (Core TH.TypeQ)
repNamedTyCon (MkC s) = rep2 conTName [s]

repTupleTyCon :: Int -> DsM (Core TH.TypeQ)
-- Note: not Core Int; it's easier to be direct here
repTupleTyCon i = do dflags <- getDynFlags
                     rep2 tupleTName [mkIntExprInt dflags i]

repUnboxedTupleTyCon :: Int -> DsM (Core TH.TypeQ)
-- Note: not Core Int; it's easier to be direct here
repUnboxedTupleTyCon i = do dflags <- getDynFlags
                            rep2 unboxedTupleTName [mkIntExprInt dflags i]

repArrowTyCon :: DsM (Core TH.TypeQ)
repArrowTyCon = rep2 arrowTName []

repListTyCon :: DsM (Core TH.TypeQ)
repListTyCon = rep2 listTName []

repPromotedTyCon :: Core TH.Name -> DsM (Core TH.TypeQ)
repPromotedTyCon (MkC s) = rep2 promotedTName [s]

repPromotedTupleTyCon :: Int -> DsM (Core TH.TypeQ)
repPromotedTupleTyCon i = do dflags <- getDynFlags
                             rep2 promotedTupleTName [mkIntExprInt dflags i]

repPromotedNilTyCon :: DsM (Core TH.TypeQ)
repPromotedNilTyCon = rep2 promotedNilTName []

repPromotedConsTyCon :: DsM (Core TH.TypeQ)
repPromotedConsTyCon = rep2 promotedConsTName []

------------ Kinds -------------------

repPlainTV :: Core TH.Name -> DsM (Core TH.TyVarBndr)
repPlainTV (MkC nm) = rep2 plainTVName [nm]

repKindedTV :: Core TH.Name -> Core TH.Kind -> DsM (Core TH.TyVarBndr)
repKindedTV (MkC nm) (MkC ki) = rep2 kindedTVName [nm, ki]

repKVar :: Core TH.Name -> DsM (Core TH.Kind)
repKVar (MkC s) = rep2 varKName [s]

repKCon :: Core TH.Name -> DsM (Core TH.Kind)
repKCon (MkC s) = rep2 conKName [s]

repKTuple :: Int -> DsM (Core TH.Kind)
repKTuple i = do dflags <- getDynFlags
                 rep2 tupleKName [mkIntExprInt dflags i]

repKArrow :: DsM (Core TH.Kind)
repKArrow = rep2 arrowKName []

repKList :: DsM (Core TH.Kind)
repKList = rep2 listKName []

repKApp :: Core TH.Kind -> Core TH.Kind -> DsM (Core TH.Kind)
repKApp (MkC k1) (MkC k2) = rep2 appKName [k1, k2]

repKApps :: Core TH.Kind -> [Core TH.Kind] -> DsM (Core TH.Kind)
repKApps f []     = return f
repKApps f (k:ks) = do { f' <- repKApp f k; repKApps f' ks }

repKStar :: DsM (Core TH.Kind)
repKStar = rep2 starKName []

repKConstraint :: DsM (Core TH.Kind)
repKConstraint = rep2 constraintKName []

----------------------------------------------------------
--       Type family result signature

repNoSig :: DsM (Core TH.FamilyResultSig)
repNoSig = rep2 noSigName []

repKindSig :: Core TH.Kind -> DsM (Core TH.FamilyResultSig)
repKindSig (MkC ki) = rep2 kindSigName [ki]

repTyVarSig :: Core TH.TyVarBndr -> DsM (Core TH.FamilyResultSig)
repTyVarSig (MkC bndr) = rep2 tyVarSigName [bndr]

----------------------------------------------------------
--              Literals

repLiteral :: HsLit -> DsM (Core TH.Lit)
repLiteral (HsStringPrim _ bs)
  = do dflags   <- getDynFlags
       word8_ty <- lookupType word8TyConName
       let w8s = unpack bs
           w8s_expr = map (\w8 -> mkCoreConApps word8DataCon
                                  [mkWordLit dflags (toInteger w8)]) w8s
       rep2 stringPrimLName [mkListExpr word8_ty w8s_expr]
repLiteral lit
  = do lit' <- case lit of
                   HsIntPrim _ i    -> mk_integer i
                   HsWordPrim _ w   -> mk_integer w
                   HsInt _ i        -> mk_integer i
                   HsFloatPrim r    -> mk_rational r
                   HsDoublePrim r   -> mk_rational r
                   HsCharPrim _ c   -> mk_char c
                   _ -> return lit
       lit_expr <- dsLit lit'
       case mb_lit_name of
          Just lit_name -> rep2 lit_name [lit_expr]
          Nothing -> notHandled "Exotic literal" (ppr lit)
  where
    mb_lit_name = case lit of
                 HsInteger _ _ _  -> Just integerLName
                 HsInt     _ _    -> Just integerLName
                 HsIntPrim _ _    -> Just intPrimLName
                 HsWordPrim _ _   -> Just wordPrimLName
                 HsFloatPrim _    -> Just floatPrimLName
                 HsDoublePrim _   -> Just doublePrimLName
                 HsChar _ _       -> Just charLName
                 HsCharPrim _ _   -> Just charPrimLName
                 HsString _ _     -> Just stringLName
                 HsRat _ _        -> Just rationalLName
                 _                -> Nothing

mk_integer :: Integer -> DsM HsLit
mk_integer  i = do integer_ty <- lookupType integerTyConName
                   return $ HsInteger "" i integer_ty
mk_rational :: FractionalLit -> DsM HsLit
mk_rational r = do rat_ty <- lookupType rationalTyConName
                   return $ HsRat r rat_ty
mk_string :: FastString -> DsM HsLit
mk_string s = return $ HsString "" s

mk_char :: Char -> DsM HsLit
mk_char c = return $ HsChar "" c

repOverloadedLiteral :: HsOverLit Name -> DsM (Core TH.Lit)
repOverloadedLiteral (OverLit { ol_val = val})
  = do { lit <- mk_lit val; repLiteral lit }
        -- The type Rational will be in the environment, because
        -- the smart constructor 'TH.Syntax.rationalL' uses it in its type,
        -- and rationalL is sucked in when any TH stuff is used

mk_lit :: OverLitVal -> DsM HsLit
mk_lit (HsIntegral _ i)   = mk_integer  i
mk_lit (HsFractional f)   = mk_rational f
mk_lit (HsIsString _ s)   = mk_string   s

--------------- Miscellaneous -------------------

repGensym :: Core String -> DsM (Core (TH.Q TH.Name))
repGensym (MkC lit_str) = rep2 newNameName [lit_str]

repBindQ :: Type -> Type        -- a and b
         -> Core (TH.Q a) -> Core (a -> TH.Q b) -> DsM (Core (TH.Q b))
repBindQ ty_a ty_b (MkC x) (MkC y)
  = rep2 bindQName [Type ty_a, Type ty_b, x, y]

repSequenceQ :: Type -> Core [TH.Q a] -> DsM (Core (TH.Q [a]))
repSequenceQ ty_a (MkC list)
  = rep2 sequenceQName [Type ty_a, list]

------------ Lists -------------------
-- turn a list of patterns into a single pattern matching a list

repList :: Name -> (a  -> DsM (Core b))
                -> [a] -> DsM (Core [b])
repList tc_name f args
  = do { args1 <- mapM f args
       ; coreList tc_name args1 }

coreList :: Name        -- Of the TyCon of the element type
         -> [Core a] -> DsM (Core [a])
coreList tc_name es
  = do { elt_ty <- lookupType tc_name; return (coreList' elt_ty es) }

coreList' :: Type       -- The element type
          -> [Core a] -> Core [a]
coreList' elt_ty es = MkC (mkListExpr elt_ty (map unC es ))

nonEmptyCoreList :: [Core a] -> Core [a]
  -- The list must be non-empty so we can get the element type
  -- Otherwise use coreList
nonEmptyCoreList []           = panic "coreList: empty argument"
nonEmptyCoreList xs@(MkC x:_) = MkC (mkListExpr (exprType x) (map unC xs))

coreStringLit :: String -> DsM (Core String)
coreStringLit s = do { z <- mkStringExpr s; return(MkC z) }

------------------- Maybe ------------------

-- | Construct Core expression for Nothing of a given type name
coreNothing :: Name        -- ^ Name of the TyCon of the element type
            -> DsM (Core (Maybe a))
coreNothing tc_name =
    do { elt_ty <- lookupType tc_name; return (coreNothing' elt_ty) }

-- | Construct Core expression for Nothing of a given type
coreNothing' :: Type       -- ^ The element type
             -> Core (Maybe a)
coreNothing' elt_ty = MkC (mkNothingExpr elt_ty)

-- | Store given Core expression in a Just of a given type name
coreJust :: Name        -- ^ Name of the TyCon of the element type
         -> Core a -> DsM (Core (Maybe a))
coreJust tc_name es
  = do { elt_ty <- lookupType tc_name; return (coreJust' elt_ty es) }

-- | Store given Core expression in a Just of a given type
coreJust' :: Type       -- ^ The element type
          -> Core a -> Core (Maybe a)
coreJust' elt_ty es = MkC (mkJustExpr elt_ty (unC es))

------------ Literals & Variables -------------------

coreIntLit :: Int -> DsM (Core Int)
coreIntLit i = do dflags <- getDynFlags
                  return (MkC (mkIntExprInt dflags i))

coreVar :: Id -> Core TH.Name   -- The Id has type Name
coreVar id = MkC (Var id)

----------------- Failure -----------------------
notHandledL :: SrcSpan -> String -> SDoc -> DsM a
notHandledL loc what doc
  | isGoodSrcSpan loc
  = putSrcSpanDs loc $ notHandled what doc
  | otherwise
  = notHandled what doc

notHandled :: String -> SDoc -> DsM a
notHandled what doc = failWithDs msg
  where
    msg = hang (text what <+> ptext (sLit "not (yet) handled by Template Haskell"))
             2 doc