GHC/HsToCore/Quote.hs

    {-# LANGUAGE AllowAmbiguousTypes    #-}
    {-# LANGUAGE CPP                    #-}
    {-# LANGUAGE DataKinds              #-}
    {-# LANGUAGE FlexibleContexts       #-}
    {-# LANGUAGE FunctionalDependencies #-}
    {-# LANGUAGE PatternSynonyms        #-}
    {-# LANGUAGE RankNTypes             #-}
    {-# LANGUAGE ScopedTypeVariables    #-}
    {-# LANGUAGE TypeApplications       #-}
    {-# LANGUAGE TypeFamilies           #-}
    {-# LANGUAGE UndecidableInstances   #-}

    {-# OPTIONS_GHC -Wno-incomplete-uni-patterns #-}

    -----------------------------------------------------------------------------
    --
    -- (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/GHC.Builtin.Names.  It's much more convenient to do it here, because
    -- otherwise we have to recompile GHC.Builtin.Names whenever we add a Name, which is
    -- a Royal Pain (triggers other recompilation).
    -----------------------------------------------------------------------------

    module GHC.HsToCore.Quote( dsBracket ) where

    #include "HsVersions.h"

    import GHC.Prelude
    import GHC.Platform

    import GHC.Driver.Session

    import {-# SOURCE #-} GHC.HsToCore.Expr ( dsExpr )
    import GHC.HsToCore.Match.Literal
    import GHC.HsToCore.Monad
    import GHC.HsToCore.Binds

    import qualified Language.Haskell.TH as TH
    import qualified Language.Haskell.TH.Syntax as TH

    import GHC.Hs

    import GHC.Tc.Utils.TcType
    import GHC.Tc.Types.Evidence

    import GHC.Core.Class
    import GHC.Core.DataCon
    import GHC.Core.TyCon
    import GHC.Core.Multiplicity ( pattern Many )
    import GHC.Core
    import GHC.Core.Make
    import GHC.Core.Utils

    import GHC.Builtin.Names
    import GHC.Builtin.Names.TH
    import GHC.Builtin.Types

    import GHC.Unit.Module

    import GHC.Utils.Outputable
    import GHC.Utils.Panic
    import GHC.Utils.Misc
    import GHC.Utils.Monad

    import GHC.Data.Bag
    import GHC.Data.FastString
    import GHC.Data.Maybe

    import GHC.Types.SrcLoc as SrcLoc
    import GHC.Types.Unique
    import GHC.Types.Basic
    import GHC.Types.ForeignCall
    import GHC.Types.Var
    import GHC.Types.Id
    import GHC.Types.SourceText
    import GHC.Types.Fixity
    import GHC.Types.TyThing
    import GHC.Types.Name hiding( varName, tcName )
    import GHC.Types.Name.Env

    import GHC.TypeLits
    import Data.Kind (Constraint)

    import qualified GHC.LanguageExtensions as LangExt

    import Data.ByteString ( unpack )
    import Control.Monad
    import Data.List (sort, sortBy)
    import Data.Function
    import Control.Monad.Trans.Reader
    import Control.Monad.Trans.Class

    data MetaWrappers = MetaWrappers {
          -- Applies its argument to a type argument `m` and dictionary `Quote m`
          quoteWrapper :: CoreExpr -> CoreExpr
          -- Apply its argument to a type argument `m` and a dictionary `Monad m`
        , monadWrapper :: CoreExpr -> CoreExpr
          -- Apply the container typed variable `m` to the argument type `T` to get `m T`.
        , metaTy :: Type -> Type
          -- Information about the wrappers which be printed to be inspected
        , _debugWrappers :: (HsWrapper, HsWrapper, Type)
        }

    -- | Construct the functions which will apply the relevant part of the
    -- QuoteWrapper to identifiers during desugaring.
    mkMetaWrappers :: QuoteWrapper -> DsM MetaWrappers
    mkMetaWrappers q@(QuoteWrapper quote_var_raw m_var) = do
          let quote_var = Var quote_var_raw
          -- Get the superclass selector to select the Monad dictionary, going
          -- to be used to construct the monadWrapper.
          quote_tc <- dsLookupTyCon quoteClassName
          monad_tc <- dsLookupTyCon monadClassName
          let Just cls = tyConClass_maybe quote_tc
              Just monad_cls = tyConClass_maybe monad_tc
              -- Quote m -> Monad m
              monad_sel = classSCSelId cls 0

              -- Only used for the defensive assertion that the selector has
              -- the expected type
              tyvars = dataConUserTyVarBinders (classDataCon cls)
              expected_ty = mkInvisForAllTys tyvars $
                              mkInvisFunTyMany (mkClassPred cls (mkTyVarTys (binderVars tyvars)))
                                               (mkClassPred monad_cls (mkTyVarTys (binderVars tyvars)))

          MASSERT2( idType monad_sel `eqType` expected_ty, ppr monad_sel $$ ppr expected_ty)

          let m_ty = Type m_var
              -- Construct the contents of MetaWrappers
              quoteWrapper = applyQuoteWrapper q
              monadWrapper = mkWpEvApps [EvExpr $ mkCoreApps (Var monad_sel) [m_ty, quote_var]] <.>
                                mkWpTyApps [m_var]
              tyWrapper t = mkAppTy m_var t
              debug = (quoteWrapper, monadWrapper, m_var)
          q_f <- dsHsWrapper quoteWrapper
          m_f <- dsHsWrapper monadWrapper
          return (MetaWrappers q_f m_f tyWrapper debug)

    -- Turn A into m A
    wrapName :: Name -> MetaM Type
    wrapName n = do
      t <- lookupType n
      wrap_fn <- asks metaTy
      return (wrap_fn t)

    -- The local state is always the same, calculated from the passed in
    -- wrapper
    type MetaM a = ReaderT MetaWrappers DsM a

    getPlatform :: MetaM Platform
    getPlatform = targetPlatform <$> getDynFlags

    -----------------------------------------------------------------------------
    dsBracket :: Maybe QuoteWrapper -- ^ This is Nothing only when we are dealing with a VarBr
              -> HsBracket GhcRn
              -> [PendingTcSplice]
              -> DsM CoreExpr
    -- See Note [Desugaring Brackets]
    -- Returns a CoreExpr of type (M TH.Exp)
    -- The quoted thing is parameterised over Name, even though it has
    -- been type checked.  We don't want all those type decorations!

    dsBracket wrap brack splices
      = do_brack brack

      where
        runOverloaded act = do
          -- In the overloaded case we have to get given a wrapper, it is just
          -- for variable quotations that there is no wrapper, because they
          -- have a simple type.
          mw <- mkMetaWrappers (expectJust "runOverloaded" wrap)
          runReaderT (mapReaderT (dsExtendMetaEnv new_bit) act) mw

        new_bit = mkNameEnv [(n, DsSplice (unLoc e))
                            | PendingTcSplice n e <- splices]

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

    {-
    Note [Desugaring Brackets]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~

    In the old days (pre Dec 2019) quotation brackets used to be monomorphic, ie
    an expression bracket was of type Q Exp. This made the desugaring process simple
    as there were no complicated type variables to keep consistent throughout the
    whole AST. Due to the overloaded quotations proposal a quotation bracket is now
    of type `Quote m => m Exp` and all the combinators defined in TH.Lib have been
    generalised to work with any monad implementing a minimal interface.

    https://github.com/ghc-proposals/ghc-proposals/blob/master/proposals/0246-overloaded-bracket.rst

    Users can rejoice at the flexibility but now there is some additional complexity in
    how brackets are desugared as all these polymorphic combinators need their arguments
    instantiated.

    > IF YOU ARE MODIFYING THIS MODULE DO NOT USE ANYTHING SPECIFIC TO Q. INSTEAD
    > USE THE `wrapName` FUNCTION TO APPLY THE `m` TYPE VARIABLE TO A TYPE CONSTRUCTOR.

    What the arguments should be instantiated to is supplied by the `QuoteWrapper`
    datatype which is produced by `GHC.Tc.Gen.Splice`. It is a pair of an evidence variable
    for `Quote m` and a type variable `m`. All the polymorphic combinators in desugaring
    need to be applied to these two type variables.

    There are three important functions which do the application.

    1. The default is `rep2` which takes a function name of type `Quote m => T` as an argument.
    2. `rep2M` takes a function name of type `Monad m => T` as an argument
    3. `rep2_nw` takes a function name without any constraints as an argument.

    These functions then use the information in QuoteWrapper to apply the correct
    arguments to the functions as the representation is constructed.

    The `MetaM` monad carries around an environment of three functions which are
    used in order to wrap the polymorphic combinators and instantiate the arguments
    to the correct things.

    1. quoteWrapper wraps functions of type `forall m . Quote m => T`
    2. monadWrapper wraps functions of type `forall m . Monad m => T`
    3. metaTy wraps a type in the polymorphic `m` variable of the whole representation.

    Historical note about the implementation: At the first attempt, I attempted to
    lie that the type of any quotation was `Quote m => m Exp` and then specialise it
    by applying a wrapper to pass the `m` and `Quote m` arguments. This approach was
    simpler to implement but didn't work because of nested splices. For example,
    you might have a nested splice of a more specific type which fixes the type of
    the overall quote and so all the combinators used must also be instantiated to
    that specific type. Therefore you really have to use the contents of the quote
    wrapper to directly apply the right type to the combinators rather than
    first generate a polymorphic definition and then just apply the wrapper at the end.

    -}

    {- -------------- 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
    -------------------------------------------------------

    -- Proxy for the phantom type of `Core`. All the generated fragments have
    -- type something like `Quote m => m Exp` so to keep things simple we represent fragments
    -- of that type as `M Exp`.
    data M a

    repTopP :: LPat GhcRn -> MetaM (Core (M TH.Pat))
    repTopP pat = do { ss <- mkGenSyms (collectPatBinders CollNoDictBinders pat)
                     ; pat' <- addBinds ss (repLP pat)
                     ; wrapGenSyms ss pat' }

    repTopDs :: HsGroup GhcRn -> MetaM (Core (M [TH.Dec]))
    repTopDs group@(HsGroup { hs_valds   = valds
                            , hs_splcds  = splcds
                            , hs_tyclds  = tyclds
                            , hs_derivds = derivds
                            , hs_fixds   = fixds
                            , hs_defds   = defds
                            , hs_fords   = fords
                            , hs_warnds  = warnds
                            , hs_annds   = annds
                            , hs_ruleds  = ruleds
                            , hs_docs    = docs })
     = do { let { bndrs  = hsScopedTvBinders valds
                           ++ hsGroupBinders group
                           ++ map extFieldOcc (hsPatSynSelectors valds)
                ; instds = tyclds >>= group_instds } ;
            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 (tyClGroupTyClDecls tyclds)
                         ; role_ds  <- mapM repRoleD (concatMap group_roles tyclds)
                         ; kisig_ds <- mapM repKiSigD (concatMap group_kisigs tyclds)
                         ; inst_ds  <- mapM repInstD instds
                         ; deriv_ds <- mapM repStandaloneDerivD derivds
                         ; fix_ds   <- mapM repLFixD 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_doc docs

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

            core_list <- repListM decTyConName return decls ;

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

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

    hsScopedTvBinders :: HsValBinds GhcRn -> [Name]
    -- See Note [Scoped type variables in quotes]
    hsScopedTvBinders binds
      = concatMap get_scoped_tvs sigs
      where
        sigs = case binds of
                 ValBinds           _ _ sigs  -> sigs
                 XValBindsLR (NValBinds _ sigs) -> sigs

    get_scoped_tvs :: LSig GhcRn -> [Name]
    get_scoped_tvs (L _ signature)
      | TypeSig _ _ sig <- signature
      = get_scoped_tvs_from_sig (hswc_body sig)
      | ClassOpSig _ _ _ sig <- signature
      = get_scoped_tvs_from_sig sig
      | PatSynSig _ _ sig <- signature
      = get_scoped_tvs_from_sig sig
      | otherwise
      = []

    get_scoped_tvs_from_sig :: LHsSigType GhcRn -> [Name]
      -- Collect both implicit and explicit quantified variables, since
      -- the types in instance heads, as well as `via` types in DerivingVia, can
      -- bring implicitly quantified type variables into scope, e.g.,
      --
      --   instance Foo [a] where
      --     m = n @a
      --
      -- See also Note [Scoped type variables in quotes]
    get_scoped_tvs_from_sig (L _ (HsSig{sig_bndrs = outer_bndrs})) =
      hsOuterTyVarNames outer_bndrs

    {- Notes

    Note [Scoped type variables in quotes]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Quoting declarations with scoped type variables requires some care. Consider:

      $([d| f :: forall a. a -> a
            f x = x::a
          |])

    Here, the `forall a` brings `a` into scope over the binding group. This has
    ramifications when desugaring the quote, as we must ensure that that the
    desugared code binds `a` with `Language.Haskell.TH.newName` and refers to the
    bound `a` type variable in the type signature and in the body of `f`. As a
    result, the call to `newName` must occur before any part of the declaration for
    `f` is processed. 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 the hsScopedTvBinders family of
         functions.

     (b) Use `addBinds` to bring these gensymmed bindings into scope over any
         part of the code where the type variables scope. In the `f` example,
         above, that means the type signature and the body of `f`.

     (c) When processing the `forall`, /don't/ gensym the type variables. We have
         already brought the type variables into scope in part (b), after all, so
         gensymming them again would lead to shadowing. We use the rep_ty_sig
         family of functions for processing types without gensymming the type
         variables again.

     (d) Finally, we use wrapGenSyms to generate the Core for these scoped type
         variables:

           newName "a" >>= \a ->
             ... -- process the type signature and body of `f`

    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.

    Note [Don't quantify implicit type variables in quotes]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    If you're not careful, it's surprisingly easy to take this quoted declaration:

      [d| id :: a -> a
          id x = x
        |]

    and have Template Haskell turn it into this:

      id :: forall a. a -> a
      id x = x

    Notice that we explicitly quantified the variable `a`! The latter declaration
    isn't what the user wrote in the first place.

    Usually, the culprit behind these bugs is taking implicitly quantified type
    variables (often from the hsib_vars field of HsImplicitBinders) and putting
    them into a `ForallT` or `ForallC`. Doing so caused #13018 and #13123.
    -}

    -- represent associated family instances
    --
    repTyClD :: LTyClDecl GhcRn -> MetaM (Maybe (SrcSpan, Core (M TH.Dec)))

    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 (locA loc, dec)) }

    repTyClD (L loc (DataDecl { tcdLName = tc
                              , tcdTyVars = tvs
                              , tcdDataDefn = defn }))
      = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
           ; dec <- addTyClTyVarBinds tvs $ \bndrs ->
                    repDataDefn tc1 (Left bndrs) defn
           ; return (Just (locA loc, dec)) }

    repTyClD (L loc (ClassDecl { tcdCtxt = cxt, tcdLName = cls,
                                 tcdTyVars = tvs, tcdFDs = fds,
                                 tcdSigs = sigs, tcdMeths = meth_binds,
                                 tcdATs = ats, tcdATDefs = atds }))
      = do { cls1 <- lookupLOcc cls         -- See note [Binders and occurrences]
           ; dec  <- addQTyVarBinds tvs $ \bndrs ->
               do { cxt1   <- repLContext cxt
              -- See Note [Scoped type variables in quotes]
                  ; (ss, sigs_binds) <- rep_meth_sigs_binds sigs meth_binds
                  ; fds1   <- repLFunDeps fds
                  ; ats1   <- repFamilyDecls ats
                  ; atds1  <- mapM (repAssocTyFamDefaultD . unLoc) atds
                  ; decls1 <- repListM decTyConName return (ats1 ++ atds1 ++ sigs_binds)
                  ; decls2 <- repClass cxt1 cls1 bndrs fds1 decls1
                  ; wrapGenSyms ss decls2 }
           ; return $ Just (locA loc, dec)
           }

    -------------------------
    repRoleD :: LRoleAnnotDecl GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repRoleD (L loc (RoleAnnotDecl _ tycon roles))
      = do { tycon1 <- lookupLOcc tycon
           ; roles1 <- mapM repRole roles
           ; roles2 <- coreList roleTyConName roles1
           ; dec <- repRoleAnnotD tycon1 roles2
           ; return (locA loc, dec) }

    -------------------------
    repKiSigD :: LStandaloneKindSig GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repKiSigD (L loc kisig) =
      case kisig of
        StandaloneKindSig _ v ki -> do
          MkC th_v  <- lookupLOcc v
          MkC th_ki <- repHsSigType ki
          dec       <- rep2 kiSigDName [th_v, th_ki]
          pure (locA loc, dec)

    -------------------------
    repDataDefn :: Core TH.Name
                -> Either (Core [(M (TH.TyVarBndr ()))])
                            -- the repTyClD case
                          (Core (Maybe [(M (TH.TyVarBndr ()))]), Core (M TH.Type))
                            -- the repDataFamInstD case
                -> HsDataDefn GhcRn
                -> MetaM (Core (M TH.Dec))
    repDataDefn tc opts
              (HsDataDefn { dd_ND = new_or_data, dd_ctxt = cxt, dd_kindSig = ksig
                          , dd_cons = cons, dd_derivs = mb_derivs })
      = do { cxt1     <- repLContext cxt
           ; derivs1  <- repDerivs mb_derivs
           ; case (new_or_data, cons) of
               (NewType, [con])  -> do { con'  <- repC con
                                       ; ksig' <- repMaybeLTy ksig
                                       ; repNewtype cxt1 tc opts ksig' con'
                                                    derivs1 }
               (NewType, _) -> lift $ failWithDs (text "Multiple constructors for newtype:"
                                           <+> pprQuotedList
                                           (getConNames $ unLoc $ head cons))
               (DataType, _) -> do { ksig' <- repMaybeLTy ksig
                                   ; consL <- mapM repC cons
                                   ; cons1 <- coreListM conTyConName consL
                                   ; repData cxt1 tc opts ksig' cons1
                                             derivs1 }
           }

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

    repFamilyDecl :: LFamilyDecl GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    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 :: [LHsTyVarBndr () GhcRn] -> LHsQTyVars GhcRn
                 mkHsQTvs tvs = HsQTvs { hsq_ext = []
                                       , hsq_explicit = 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 . unLoc) eqns
                      ; eqns2  <- coreListM tySynEqnTyConName 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 (locA loc, dec)
           }

    -- | Represent result signature of a type family
    repFamilyResultSig :: FamilyResultSig GhcRn -> MetaM (Core (M TH.FamilyResultSig))
    repFamilyResultSig (NoSig _)         = repNoSig
    repFamilyResultSig (KindSig _ ki)    = do { ki' <- repLTy 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 GhcRn
                                  -> MetaM (Core (Maybe (M TH.Kind)))
    repFamilyResultSigToMaybeKind (NoSig _) =
        coreNothingM kindTyConName
    repFamilyResultSigToMaybeKind (KindSig _ ki) =
        coreJustM kindTyConName =<< repLTy ki
    repFamilyResultSigToMaybeKind TyVarSig{} =
        panic "repFamilyResultSigToMaybeKind: unexpected TyVarSig"

    -- | Represent injectivity annotation of a type family
    repInjectivityAnn :: Maybe (LInjectivityAnn GhcRn)
                      -> MetaM (Core (Maybe TH.InjectivityAnn))
    repInjectivityAnn Nothing =
        coreNothing injAnnTyConName
    repInjectivityAnn (Just (L _ (InjectivityAnn _ lhs rhs))) =
        do { lhs'   <- lookupBinder (unLoc lhs)
           ; rhs1   <- mapM (lookupBinder . unLoc) rhs
           ; rhs2   <- coreList nameTyConName rhs1
           ; injAnn <- rep2_nw injectivityAnnName [unC lhs', unC rhs2]
           ; coreJust injAnnTyConName injAnn }

    repFamilyDecls :: [LFamilyDecl GhcRn] -> MetaM [Core (M TH.Dec)]
    repFamilyDecls fds = liftM de_loc (mapM repFamilyDecl fds)

    repAssocTyFamDefaultD :: TyFamDefltDecl GhcRn -> MetaM (Core (M TH.Dec))
    repAssocTyFamDefaultD = repTyFamInstD

    -------------------------
    -- represent fundeps
    --
    repLFunDeps :: [LHsFunDep GhcRn] -> MetaM (Core [TH.FunDep])
    repLFunDeps fds = repList funDepTyConName repLFunDep fds

    repLFunDep :: LHsFunDep GhcRn -> MetaM (Core TH.FunDep)
    repLFunDep (L _ (FunDep _ xs ys))
       = do xs' <- repList nameTyConName (lookupBinder . unLoc) xs
            ys' <- repList nameTyConName (lookupBinder . unLoc) ys
            repFunDep xs' ys'

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

    repClsInstD :: ClsInstDecl GhcRn -> MetaM (Core (M TH.Dec))
    repClsInstD (ClsInstDecl { cid_poly_ty = ty, cid_binds = binds
                             , cid_sigs = sigs, cid_tyfam_insts = ats
                             , cid_datafam_insts = adts
                             , cid_overlap_mode = overlap
                             })
      = addSimpleTyVarBinds 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 (#5410)
                --
                do { cxt1     <- repLContext cxt
                   ; inst_ty1 <- repLTy inst_ty
              -- See Note [Scoped type variables in quotes]
                   ; (ss, sigs_binds) <- rep_meth_sigs_binds sigs binds
                   ; ats1   <- mapM (repTyFamInstD . unLoc) ats
                   ; adts1  <- mapM (repDataFamInstD . unLoc) adts
                   ; decls1 <- coreListM decTyConName (ats1 ++ adts1 ++ sigs_binds)
                   ; rOver  <- repOverlap (fmap unLoc overlap)
                   ; decls2 <- repInst rOver cxt1 inst_ty1 decls1
                   ; wrapGenSyms ss decls2 }
     where
       (tvs, cxt, inst_ty) = splitLHsInstDeclTy ty

    repStandaloneDerivD :: LDerivDecl GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repStandaloneDerivD (L loc (DerivDecl { deriv_strategy = strat
                                           , deriv_type     = ty }))
      = do { dec <- repDerivStrategy strat  $ \strat' ->
                    addSimpleTyVarBinds tvs $
                    do { cxt'     <- repLContext cxt
                       ; inst_ty' <- repLTy inst_ty
                       ; repDeriv strat' cxt' inst_ty' }
           ; return (locA loc, dec) }
      where
        (tvs, cxt, inst_ty) = splitLHsInstDeclTy (dropWildCards ty)

    repTyFamInstD :: TyFamInstDecl GhcRn -> MetaM (Core (M TH.Dec))
    repTyFamInstD (TyFamInstDecl { tfid_eqn = eqn })
      = do { eqn1 <- repTyFamEqn eqn
           ; repTySynInst eqn1 }

    repTyFamEqn :: TyFamInstEqn GhcRn -> MetaM (Core (M TH.TySynEqn))
    repTyFamEqn (FamEqn { feqn_tycon = tc_name
                        , feqn_bndrs = outer_bndrs
                        , feqn_pats = tys
                        , feqn_fixity = fixity
                        , feqn_rhs  = rhs })
      = do { tc <- lookupLOcc tc_name     -- See note [Binders and occurrences]
           ; addHsOuterFamEqnTyVarBinds outer_bndrs $ \mb_exp_bndrs ->
             do { tys1 <- case fixity of
                            Prefix -> repTyArgs (repNamedTyCon tc) tys
                            Infix  -> do { (HsValArg t1: HsValArg t2: args) <- checkTys tys
                                         ; t1' <- repLTy t1
                                         ; t2'  <- repLTy t2
                                         ; repTyArgs (repTInfix t1' tc t2') args }
                ; rhs1 <- repLTy rhs
                ; repTySynEqn mb_exp_bndrs tys1 rhs1 } }
         where checkTys :: [LHsTypeArg GhcRn] -> MetaM [LHsTypeArg GhcRn]
               checkTys tys@(HsValArg _:HsValArg _:_) = return tys
               checkTys _ = panic "repTyFamEqn:checkTys"

    repTyArgs :: MetaM (Core (M TH.Type)) -> [LHsTypeArg GhcRn] -> MetaM (Core (M TH.Type))
    repTyArgs f [] = f
    repTyArgs f (HsValArg ty : as) = do { f' <- f
                                        ; ty' <- repLTy ty
                                        ; repTyArgs (repTapp f' ty') as }
    repTyArgs f (HsTypeArg _ ki : as) = do { f' <- f
                                           ; ki' <- repLTy ki
                                           ; repTyArgs (repTappKind f' ki') as }
    repTyArgs f (HsArgPar _ : as) = repTyArgs f as

    repDataFamInstD :: DataFamInstDecl GhcRn -> MetaM (Core (M TH.Dec))
    repDataFamInstD (DataFamInstDecl { dfid_eqn =
                                          FamEqn { feqn_tycon = tc_name
                                                 , feqn_bndrs = outer_bndrs
                                                 , feqn_pats  = tys
                                                 , feqn_fixity = fixity
                                                 , feqn_rhs   = defn }})
      = do { tc <- lookupLOcc tc_name         -- See note [Binders and occurrences]
           ; addHsOuterFamEqnTyVarBinds outer_bndrs $ \mb_exp_bndrs ->
             do { tys1 <- case fixity of
                            Prefix -> repTyArgs (repNamedTyCon tc) tys
                            Infix  -> do { (HsValArg t1: HsValArg t2: args) <- checkTys tys
                                         ; t1' <- repLTy t1
                                         ; t2'  <- repLTy t2
                                         ; repTyArgs (repTInfix t1' tc t2') args }
                ; repDataDefn tc (Right (mb_exp_bndrs, tys1)) defn } }

          where checkTys :: [LHsTypeArg GhcRn] -> MetaM [LHsTypeArg GhcRn]
                checkTys tys@(HsValArg _: HsValArg _: _) = return tys
                checkTys _ = panic "repDataFamInstD:checkTys"

    repForD :: LForeignDecl GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repForD (L loc (ForeignImport { fd_name = name, fd_sig_ty = typ
                                      , fd_fi = CImport (L _ cc)
                                                        (L _ s) mch cis _ }))
     = do MkC name' <- lookupLOcc name
          MkC typ' <- repHsSigType 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 (locA 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@(L _ ForeignExport{}) = notHandled "Foreign export" (ppr decl)

    repCCallConv :: CCallConv -> MetaM (Core TH.Callconv)
    repCCallConv CCallConv          = rep2_nw cCallName []
    repCCallConv StdCallConv        = rep2_nw stdCallName []
    repCCallConv CApiConv           = rep2_nw cApiCallName []
    repCCallConv PrimCallConv       = rep2_nw primCallName []
    repCCallConv JavaScriptCallConv = rep2_nw javaScriptCallName []

    repSafety :: Safety -> MetaM (Core TH.Safety)
    repSafety PlayRisky = rep2_nw unsafeName []
    repSafety PlayInterruptible = rep2_nw interruptibleName []
    repSafety PlaySafe = rep2_nw safeName []

    repLFixD :: LFixitySig GhcRn -> MetaM [(SrcSpan, Core (M TH.Dec))]
    repLFixD (L loc fix_sig) = rep_fix_d (locA loc) fix_sig

    rep_fix_d :: SrcSpan -> FixitySig GhcRn -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_fix_d 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 GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repRuleD (L loc (HsRule { rd_name = n
                            , rd_act = act
                            , rd_tyvs = ty_bndrs
                            , rd_tmvs = tm_bndrs
                            , rd_lhs = lhs
                            , rd_rhs = rhs }))
      = do { rule <- addHsTyVarBinds (fromMaybe [] ty_bndrs) $ \ ex_bndrs ->
             do { let tm_bndr_names = concatMap ruleBndrNames tm_bndrs
                ; ss <- mkGenSyms tm_bndr_names
                ; rule <- addBinds ss $
                          do { elt_ty <- wrapName tyVarBndrUnitTyConName
                             ; ty_bndrs' <- return $ case ty_bndrs of
                                 Nothing -> coreNothing' (mkListTy elt_ty)
                                 Just _  -> coreJust' (mkListTy elt_ty) ex_bndrs
                             ; tm_bndrs' <- repListM ruleBndrTyConName
                                                    repRuleBndr
                                                    tm_bndrs
                             ; n'   <- coreStringLit $ unpackFS $ snd $ unLoc n
                             ; act' <- repPhases act
                             ; lhs' <- repLE lhs
                             ; rhs' <- repLE rhs
                             ; repPragRule n' ty_bndrs' tm_bndrs' lhs' rhs' act' }
               ; wrapGenSyms ss rule  }
           ; return (locA loc, rule) }

    ruleBndrNames :: LRuleBndr GhcRn -> [Name]
    ruleBndrNames (L _ (RuleBndr _ n))      = [unLoc n]
    ruleBndrNames (L _ (RuleBndrSig _ n sig))
      | HsPS { hsps_ext = HsPSRn { hsps_imp_tvs = vars }} <- sig
      = unLoc n : vars

    repRuleBndr :: LRuleBndr GhcRn -> MetaM (Core (M TH.RuleBndr))
    repRuleBndr (L _ (RuleBndr _ n))
      = do { MkC n' <- lookupNBinder n
           ; rep2 ruleVarName [n'] }
    repRuleBndr (L _ (RuleBndrSig _ n sig))
      = do { MkC n'  <- lookupNBinder n
           ; MkC ty' <- repLTy (hsPatSigType sig)
           ; rep2 typedRuleVarName [n', ty'] }

    repAnnD :: LAnnDecl GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    repAnnD (L loc (HsAnnotation _ _ ann_prov (L _ exp)))
      = do { target <- repAnnProv ann_prov
           ; exp'   <- repE exp
           ; dec    <- repPragAnn target exp'
           ; return (locA loc, dec) }

    repAnnProv :: AnnProvenance GhcRn -> MetaM (Core TH.AnnTarget)
    repAnnProv (ValueAnnProvenance n)
      = do { -- An ANN references an identifier bound elsewhere in the module, so
             -- we must look it up using lookupLOcc (#19377).
             -- Similarly for TypeAnnProvenance (`ANN type`) below.
             MkC n' <- lookupLOcc n
           ; rep2_nw valueAnnotationName [ n' ] }
    repAnnProv (TypeAnnProvenance n)
      = do { MkC n' <- lookupLOcc n
           ; rep2_nw typeAnnotationName [ n' ] }
    repAnnProv ModuleAnnProvenance
      = rep2_nw moduleAnnotationName []

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

    repC :: LConDecl GhcRn -> MetaM (Core (M TH.Con))
    repC (L _ (ConDeclH98 { con_name   = con
                          , con_forall = False
                          , con_mb_cxt = Nothing
                          , con_args   = args }))
      = repH98DataCon con args

    repC (L _ (ConDeclH98 { con_name = con
                          , con_forall = is_existential
                          , con_ex_tvs = con_tvs
                          , con_mb_cxt = mcxt
                          , con_args = args }))
      = addHsTyVarBinds con_tvs $ \ ex_bndrs ->
             do { c'    <- repH98DataCon con args
                ; ctxt' <- repMbContext mcxt
                ; if not is_existential && isNothing mcxt
                  then return c'
                  else rep2 forallCName ([unC ex_bndrs, unC ctxt', unC c'])
                }

    repC (L _ (ConDeclGADT { con_names  = cons
                           , con_bndrs  = L _ outer_bndrs
                           , con_mb_cxt = mcxt
                           , con_g_args = args
                           , con_res_ty = res_ty }))
      | null_outer_imp_tvs && null_outer_exp_tvs
                                     -- No implicit or explicit variables
      , Nothing <- mcxt              -- No context
                                     -- ==> no need for a forall
      = repGadtDataCons cons args res_ty

      | otherwise
      = addHsOuterSigTyVarBinds outer_bndrs $ \ outer_bndrs' ->
                 -- See Note [Don't quantify implicit type variables in quotes]
        do { c'    <- repGadtDataCons cons args res_ty
           ; ctxt' <- repMbContext mcxt
           ; if null_outer_exp_tvs && isNothing mcxt
             then return c'
             else rep2 forallCName ([unC outer_bndrs', unC ctxt', unC c']) }
      where
        null_outer_imp_tvs = nullOuterImplicit outer_bndrs
        null_outer_exp_tvs = nullOuterExplicit outer_bndrs

    repMbContext :: Maybe (LHsContext GhcRn) -> MetaM (Core (M TH.Cxt))
    repMbContext Nothing          = repContext []
    repMbContext (Just (L _ cxt)) = repContext cxt

    repSrcUnpackedness :: SrcUnpackedness -> MetaM (Core (M TH.SourceUnpackedness))
    repSrcUnpackedness SrcUnpack   = rep2 sourceUnpackName         []
    repSrcUnpackedness SrcNoUnpack = rep2 sourceNoUnpackName       []
    repSrcUnpackedness NoSrcUnpack = rep2 noSourceUnpackednessName []

    repSrcStrictness :: SrcStrictness -> MetaM (Core (M TH.SourceStrictness))
    repSrcStrictness SrcLazy     = rep2 sourceLazyName         []
    repSrcStrictness SrcStrict   = rep2 sourceStrictName       []
    repSrcStrictness NoSrcStrict = rep2 noSourceStrictnessName []

    repBangTy :: LBangType GhcRn -> MetaM (Core (M TH.BangType))
    repBangTy ty = do
      MkC u <- repSrcUnpackedness su'
      MkC s <- repSrcStrictness ss'
      MkC b <- rep2 bangName [u, s]
      MkC t <- repLTy ty'
      rep2 bangTypeName [b, t]
      where
        (su', ss', ty') = case unLoc ty of
                HsBangTy _ (HsSrcBang _ su ss) ty -> (su, ss, ty)
                _ -> (NoSrcUnpack, NoSrcStrict, ty)

    -------------------------------------------------------
    --                      Deriving clauses
    -------------------------------------------------------

    repDerivs :: HsDeriving GhcRn -> MetaM (Core [M TH.DerivClause])
    repDerivs clauses
      = repListM derivClauseTyConName repDerivClause clauses

    repDerivClause :: LHsDerivingClause GhcRn
                   -> MetaM (Core (M TH.DerivClause))
    repDerivClause (L _ (HsDerivingClause
                              { deriv_clause_strategy = dcs
                              , deriv_clause_tys      = dct }))
      = repDerivStrategy dcs $ \(MkC dcs') ->
        do MkC dct' <- rep_deriv_clause_tys dct
           rep2 derivClauseName [dcs',dct']
      where
        rep_deriv_clause_tys :: LDerivClauseTys GhcRn -> MetaM (Core [M TH.Type])
        rep_deriv_clause_tys (L _ dct) = case dct of
          DctSingle _ ty -> rep_deriv_tys [ty]
          DctMulti _ tys -> rep_deriv_tys tys

        rep_deriv_tys :: [LHsSigType GhcRn] -> MetaM (Core [M TH.Type])
        rep_deriv_tys = repListM typeTyConName repHsSigType

    rep_meth_sigs_binds :: [LSig GhcRn] -> LHsBinds GhcRn
                        -> MetaM ([GenSymBind], [Core (M TH.Dec)])
    -- Represent signatures and methods in class/instance declarations.
    -- See Note [Scoped type variables in quotes]
    --
    -- Why not use 'repBinds': we have already created symbols for methods in
    -- 'repTopDs' via 'hsGroupBinders'. However in 'repBinds', we recreate
    -- these fun_id via 'collectHsValBinders decs', which would lead to the
    -- instance declarations failing in TH.
    rep_meth_sigs_binds sigs binds
      = do { let tvs = concatMap get_scoped_tvs sigs
           ; ss <- mkGenSyms tvs
           ; sigs1 <- addBinds ss $ rep_sigs sigs
           ; binds1 <- addBinds ss $ rep_binds binds
           ; return (ss, de_loc (sort_by_loc (sigs1 ++ binds1))) }

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

    rep_sigs :: [LSig GhcRn] -> MetaM [(SrcSpan, Core (M TH.Dec))]
            -- We silently ignore ones we don't recognise
    rep_sigs = concatMapM rep_sig

    rep_sig :: LSig GhcRn -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_sig (L loc (TypeSig _ nms ty))
      = mapM (rep_wc_ty_sig sigDName (locA loc) ty) nms
    rep_sig (L loc (PatSynSig _ nms ty))
      = mapM (rep_patsyn_ty_sig (locA loc) ty) nms
    rep_sig (L loc (ClassOpSig _ is_deflt nms ty))
      | is_deflt     = mapM (rep_ty_sig defaultSigDName (locA loc) ty) nms
      | otherwise    = mapM (rep_ty_sig sigDName (locA loc) ty) nms
    rep_sig d@(L _ (IdSig {}))           = pprPanic "rep_sig IdSig" (ppr d)
    rep_sig (L loc (FixSig _ fix_sig))   = rep_fix_d (locA loc) fix_sig
    rep_sig (L loc (InlineSig _ nm ispec))= rep_inline nm ispec (locA loc)
    rep_sig (L loc (SpecSig _ nm tys ispec))
      = concatMapM (\t -> rep_specialise nm t ispec (locA loc)) tys
    rep_sig (L loc (SpecInstSig _ _ ty))  = rep_specialiseInst ty (locA loc)
    rep_sig (L _   (MinimalSig {}))       = notHandled "MINIMAL pragmas" empty
    rep_sig (L _   (SCCFunSig {}))        = notHandled "SCC pragmas" empty
    rep_sig (L loc (CompleteMatchSig _ _st cls mty))
      = rep_complete_sig cls mty (locA loc)

    -- Desugar the explicit type variable binders in an 'LHsSigType', making
    -- sure not to gensym them.
    -- See Note [Scoped type variables in quotes]
    -- and Note [Don't quantify implicit type variables in quotes]
    rep_ty_sig_tvs :: [LHsTyVarBndr Specificity GhcRn]
                   -> MetaM (Core [M TH.TyVarBndrSpec])
    rep_ty_sig_tvs explicit_tvs
      = repListM tyVarBndrSpecTyConName repTyVarBndr
                 explicit_tvs

    -- Desugar the outer type variable binders in an 'LHsSigType', making
    -- sure not to gensym them.
    -- See Note [Scoped type variables in quotes]
    -- and Note [Don't quantify implicit type variables in quotes]
    rep_ty_sig_outer_tvs :: HsOuterSigTyVarBndrs GhcRn
                         -> MetaM (Core [M TH.TyVarBndrSpec])
    rep_ty_sig_outer_tvs (HsOuterImplicit{}) =
      coreListM tyVarBndrSpecTyConName []
    rep_ty_sig_outer_tvs (HsOuterExplicit{hso_bndrs = explicit_tvs}) =
      rep_ty_sig_tvs explicit_tvs

    -- Desugar a top-level type signature. Unlike 'repHsSigType', this
    -- deliberately avoids gensymming the type variables.
    -- See Note [Scoped type variables in quotes]
    -- and Note [Don't quantify implicit type variables in quotes]
    rep_ty_sig :: Name -> SrcSpan -> LHsSigType GhcRn -> LocatedN Name
               -> MetaM (SrcSpan, Core (M TH.Dec))
    rep_ty_sig mk_sig loc sig_ty nm
      = do { nm1 <- lookupLOcc nm
           ; ty1 <- rep_ty_sig' sig_ty
           ; sig <- repProto mk_sig nm1 ty1
           ; return (loc, sig) }

    -- Desugar an 'LHsSigType', making sure not to gensym the type variables at
    -- the front of the type signature.
    -- See Note [Scoped type variables in quotes]
    -- and Note [Don't quantify implicit type variables in quotes]
    rep_ty_sig' :: LHsSigType GhcRn
                -> MetaM (Core (M TH.Type))
    rep_ty_sig' (L _ (HsSig{sig_bndrs = outer_bndrs, sig_body = body}))
      | (ctxt, tau) <- splitLHsQualTy body
      = do { th_explicit_tvs <- rep_ty_sig_outer_tvs outer_bndrs
           ; th_ctxt <- repLContext ctxt
           ; th_tau  <- repLTy tau
           ; if nullOuterExplicit outer_bndrs && null (fromMaybeContext ctxt)
                then return th_tau
                else repTForall th_explicit_tvs th_ctxt th_tau }

    rep_patsyn_ty_sig :: SrcSpan -> LHsSigType GhcRn -> LocatedN Name
                      -> MetaM (SrcSpan, Core (M TH.Dec))
    -- represents a pattern synonym type signature;
    -- see Note [Pattern synonym type signatures and Template Haskell] in "GHC.ThToHs"
    --
    -- Don't create the implicit and explicit variables when desugaring signatures,
    -- see Note [Scoped type variables in quotes]
    -- and Note [Don't quantify implicit type variables in quotes]
    rep_patsyn_ty_sig loc sig_ty nm
      | (univs, reqs, exis, provs, ty) <- splitLHsPatSynTy sig_ty
      = do { nm1 <- lookupLOcc nm
           ; th_univs <- rep_ty_sig_tvs univs
           ; th_exis  <- rep_ty_sig_tvs exis

           ; th_reqs  <- repLContext reqs
           ; th_provs <- repLContext provs
           ; th_ty    <- repLTy ty
           ; ty1      <- repTForall th_univs th_reqs =<<
                           repTForall th_exis th_provs th_ty
           ; sig      <- repProto patSynSigDName nm1 ty1
           ; return (loc, sig) }

    rep_wc_ty_sig :: Name -> SrcSpan -> LHsSigWcType GhcRn -> LocatedN Name
                  -> MetaM (SrcSpan, Core (M TH.Dec))
    rep_wc_ty_sig mk_sig loc sig_ty nm
      = rep_ty_sig mk_sig loc (hswc_body sig_ty) nm

    rep_inline :: LocatedN Name
               -> InlinePragma      -- Never defaultInlinePragma
               -> SrcSpan
               -> MetaM [(SrcSpan, Core (M TH.Dec))]
    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 :: LocatedN Name -> LHsSigType GhcRn -> InlinePragma
                   -> SrcSpan
                   -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_specialise nm ty ispec loc
      = do { nm1 <- lookupLOcc nm
           ; ty1 <- repHsSigType ty
           ; phases <- repPhases $ inl_act ispec
           ; let inline = inl_inline ispec
           ; pragma <- if noUserInlineSpec inline
                       then -- SPECIALISE
                         repPragSpec nm1 ty1 phases
                       else -- SPECIALISE INLINE
                         do { inline1 <- repInline inline
                            ; repPragSpecInl nm1 ty1 inline1 phases }
           ; return [(loc, pragma)]
           }

    rep_specialiseInst :: LHsSigType GhcRn -> SrcSpan
                       -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_specialiseInst ty loc
      = do { ty1    <- repHsSigType ty
           ; pragma <- repPragSpecInst ty1
           ; return [(loc, pragma)] }

    repInline :: InlineSpec -> MetaM (Core TH.Inline)
    repInline NoInline         = dataCon noInlineDataConName
    repInline Inline           = dataCon inlineDataConName
    repInline Inlinable        = dataCon inlinableDataConName
    repInline NoUserInlinePrag = notHandled "NOUSERINLINE" empty

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

    repPhases :: Activation -> MetaM (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

    rep_complete_sig :: Located [LocatedN Name]
                     -> Maybe (LocatedN Name)
                     -> SrcSpan
                     -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_complete_sig (L _ cls) mty loc
      = do { mty' <- repMaybe nameTyConName lookupLOcc mty
           ; cls' <- repList nameTyConName lookupLOcc cls
           ; sig <- repPragComplete cls' mty'
           ; return [(loc, sig)] }

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

    class RepTV flag flag' | flag -> flag' where
        tyVarBndrName :: Name
        repPlainTV  :: Core TH.Name -> flag -> MetaM (Core (M (TH.TyVarBndr flag')))
        repKindedTV :: Core TH.Name -> flag -> Core (M TH.Kind)
                    -> MetaM (Core (M (TH.TyVarBndr flag')))

    instance RepTV () () where
        tyVarBndrName = tyVarBndrUnitTyConName
        repPlainTV  (MkC nm) ()          = rep2 plainTVName  [nm]
        repKindedTV (MkC nm) () (MkC ki) = rep2 kindedTVName [nm, ki]

    instance RepTV Specificity TH.Specificity where
        tyVarBndrName = tyVarBndrSpecTyConName
        repPlainTV  (MkC nm) spec          = do { (MkC spec') <- rep_flag spec
                                                ; rep2 plainInvisTVName  [nm, spec'] }
        repKindedTV (MkC nm) spec (MkC ki) = do { (MkC spec') <- rep_flag spec
                                                ; rep2 kindedInvisTVName [nm, spec', ki] }

    rep_flag :: Specificity -> MetaM (Core TH.Specificity)
    rep_flag SpecifiedSpec = rep2_nw specifiedSpecName []
    rep_flag InferredSpec  = rep2_nw inferredSpecName []

    addHsOuterFamEqnTyVarBinds ::
         HsOuterFamEqnTyVarBndrs GhcRn
      -> (Core (Maybe [M TH.TyVarBndrUnit]) -> MetaM (Core (M a)))
      -> MetaM (Core (M a))
    addHsOuterFamEqnTyVarBinds outer_bndrs thing_inside = do
      elt_ty <- wrapName tyVarBndrUnitTyConName
      case outer_bndrs of
        HsOuterImplicit{hso_ximplicit = imp_tvs} ->
          addTyClTyVarBinds (mk_qtvs imp_tvs []) $ \_th_exp_bndrs ->
          thing_inside $ coreNothingList elt_ty
        HsOuterExplicit{hso_bndrs = exp_bndrs} ->
          addTyClTyVarBinds (mk_qtvs [] exp_bndrs) $ \th_exp_bndrs ->
          thing_inside $ coreJustList elt_ty th_exp_bndrs
      where
        mk_qtvs imp_tvs exp_tvs = HsQTvs { hsq_ext = imp_tvs
                                         , hsq_explicit = exp_tvs }

    addHsOuterSigTyVarBinds ::
         HsOuterSigTyVarBndrs GhcRn
      -> (Core [M TH.TyVarBndrSpec] -> MetaM (Core (M a)))
      -> MetaM (Core (M a))
    addHsOuterSigTyVarBinds outer_bndrs thing_inside = case outer_bndrs of
      HsOuterImplicit{hso_ximplicit = imp_tvs} ->
        do th_nil <- coreListM tyVarBndrSpecTyConName []
           addSimpleTyVarBinds imp_tvs $ thing_inside th_nil
      HsOuterExplicit{hso_bndrs = exp_bndrs} ->
        addHsTyVarBinds exp_bndrs thing_inside

    -- | If a type implicitly quantifies its outermost type variables, return
    -- 'True' if the list of implicitly bound type variables is empty. If a type
    -- explicitly quantifies its outermost type variables, always return 'True'.
    --
    -- This is used in various places to determine if a Template Haskell 'Type'
    -- should be headed by a 'ForallT' or not.
    nullOuterImplicit :: HsOuterSigTyVarBndrs GhcRn -> Bool
    nullOuterImplicit (HsOuterImplicit{hso_ximplicit = imp_tvs}) = null imp_tvs
    nullOuterImplicit (HsOuterExplicit{})                        = True
      -- Vacuously true, as there is no implicit quantification

    -- | If a type explicitly quantifies its outermost type variables, return
    -- 'True' if the list of explicitly bound type variables is empty. If a type
    -- implicitly quantifies its outermost type variables, always return 'True'.
    --
    -- This is used in various places to determine if a Template Haskell 'Type'
    -- should be headed by a 'ForallT' or not.
    nullOuterExplicit :: HsOuterSigTyVarBndrs GhcRn -> Bool
    nullOuterExplicit (HsOuterExplicit{hso_bndrs = exp_bndrs}) = null exp_bndrs
    nullOuterExplicit (HsOuterImplicit{})                      = True
      -- Vacuously true, as there is no outermost explicit quantification

    addSimpleTyVarBinds :: [Name]             -- the binders to be added
                        -> MetaM (Core (M a)) -- action in the ext env
                        -> MetaM (Core (M a))
    addSimpleTyVarBinds names thing_inside
      = do { fresh_names <- mkGenSyms names
           ; term <- addBinds fresh_names thing_inside
           ; wrapGenSyms fresh_names term }

    addHsTyVarBinds :: forall flag flag' a. RepTV flag flag'
                    => [LHsTyVarBndr flag GhcRn] -- the binders to be added
                    -> (Core [(M (TH.TyVarBndr flag'))] -> MetaM (Core (M a))) -- action in the ext env
                    -> MetaM (Core (M a))
    addHsTyVarBinds exp_tvs thing_inside
      = do { fresh_exp_names <- mkGenSyms (hsLTyVarNames exp_tvs)
           ; term <- addBinds fresh_exp_names $
                     do { kbs <- repListM (tyVarBndrName @flag @flag') repTyVarBndr
                                          exp_tvs
                        ; thing_inside kbs }
           ; wrapGenSyms fresh_exp_names term }

    addQTyVarBinds :: LHsQTyVars GhcRn -- the binders to be added
                   -> (Core [(M (TH.TyVarBndr ()))] -> MetaM (Core (M a))) -- action in the ext env
                   -> MetaM (Core (M a))
    addQTyVarBinds (HsQTvs { hsq_ext = imp_tvs
                          , hsq_explicit = exp_tvs })
                  thing_inside
      = addTyVarBinds exp_tvs imp_tvs thing_inside

    addTyVarBinds :: RepTV flag flag'
                  => [LHsTyVarBndr flag GhcRn] -- the binders to be added
                  -> [Name]
                  -> (Core [(M (TH.TyVarBndr flag'))] -> MetaM (Core (M a))) -- action in the ext env
                  -> MetaM (Core (M 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 exp_tvs imp_tvs thing_inside
      = addSimpleTyVarBinds imp_tvs $
        addHsTyVarBinds exp_tvs $
        thing_inside

    addTyClTyVarBinds :: LHsQTyVars GhcRn
                      -> (Core [(M (TH.TyVarBndr ()))] -> MetaM (Core (M a)))
                      -> MetaM (Core (M 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 = hsAllLTyVarNames tvs
           ; env <- lift $ 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 <- repListM tyVarBndrUnitTyConName repTyVarBndr
                                         (hsQTvExplicit tvs)
                        ; m kbs }

           ; wrapGenSyms freshNames term }

    -- | Represent a type variable binder
    repTyVarBndr :: RepTV flag flag'
                 => LHsTyVarBndr flag GhcRn -> MetaM (Core (M (TH.TyVarBndr flag')))
    repTyVarBndr (L _ (UserTyVar _ fl (L _ nm)) )
      = do { nm' <- lookupBinder nm
           ; repPlainTV nm' fl }
    repTyVarBndr (L _ (KindedTyVar _ fl (L _ nm) ki))
      = do { nm' <- lookupBinder nm
           ; ki' <- repLTy ki
           ; repKindedTV nm' fl ki' }

    -- represent a type context
    --
    repLContext :: Maybe (LHsContext GhcRn) -> MetaM (Core (M TH.Cxt))
    repLContext Nothing = repContext []
    repLContext (Just ctxt) = repContext (unLoc ctxt)

    repContext :: HsContext GhcRn -> MetaM (Core (M TH.Cxt))
    repContext ctxt = do preds <- repListM typeTyConName repLTy ctxt
                         repCtxt preds

    repHsSigType :: LHsSigType GhcRn -> MetaM (Core (M TH.Type))
    repHsSigType (L _ (HsSig { sig_bndrs = outer_bndrs, sig_body = body }))
      | (ctxt, tau) <- splitLHsQualTy body
      = addHsOuterSigTyVarBinds outer_bndrs $ \ th_outer_bndrs ->
        do { th_ctxt <- repLContext ctxt
           ; th_tau  <- repLTy tau
           ; if nullOuterExplicit outer_bndrs && null (fromMaybeContext ctxt)
             then pure th_tau
             else repTForall th_outer_bndrs th_ctxt th_tau }

    -- yield the representation of a list of types
    repLTys :: [LHsType GhcRn] -> MetaM [Core (M TH.Type)]
    repLTys tys = mapM repLTy tys

    -- represent a type
    repLTy :: LHsType GhcRn -> MetaM (Core (M TH.Type))
    repLTy ty = repTy (unLoc ty)

    -- Desugar a type headed by an invisible forall (e.g., @forall a. a@) or
    -- a context (e.g., @Show a => a@) into a ForallT from L.H.TH.Syntax.
    -- In other words, the argument to this function is always an
    -- @HsForAllTy HsForAllInvis{}@ or @HsQualTy@.
    -- Types headed by visible foralls (which are desugared to ForallVisT) are
    -- handled separately in repTy.
    repForallT :: HsType GhcRn -> MetaM (Core (M TH.Type))
    repForallT ty
     | (tvs, ctxt, tau) <- splitLHsSigmaTyInvis (noLocA ty)
     = addHsTyVarBinds tvs $ \bndrs ->
       do { ctxt1  <- repLContext ctxt
          ; tau1   <- repLTy tau
          ; repTForall bndrs ctxt1 tau1 -- forall a. C a => {...}
          }

    repTy :: HsType GhcRn -> MetaM (Core (M TH.Type))
    repTy ty@(HsForAllTy { hst_tele = tele, hst_body = body }) =
      case tele of
        HsForAllInvis{} -> repForallT ty
        HsForAllVis { hsf_vis_bndrs = tvs } ->
          addHsTyVarBinds tvs $ \bndrs ->
          do body1 <- repLTy body
             repTForallVis bndrs body1
    repTy ty@(HsQualTy {}) = repForallT ty

    repTy (HsTyVar _ _ (L _ n))
      | isLiftedTypeKindTyConName n        = repTStar
      | n `hasKey` constraintKindTyConKey  = repTConstraint
      | n `hasKey` unrestrictedFunTyConKey = repArrowTyCon
      | n `hasKey` funTyConKey             = repMulArrowTyCon
      | isTvOcc occ   = do tv1 <- lookupOcc n
                           repTvar tv1
      | isDataOcc occ = do tc1 <- lookupOcc n
                           repPromotedDataCon tc1
      | n == eqTyConName = repTequality
      | 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 (HsAppKindTy _ ty ki) = do
                                    ty1 <- repLTy ty
                                    ki1 <- repLTy ki
                                    repTappKind ty1 ki1
    repTy (HsFunTy _ w f a) | isUnrestricted w = do
                                    f1   <- repLTy f
                                    a1   <- repLTy a
                                    tcon <- repArrowTyCon
                                    repTapps tcon [f1, a1]
    repTy (HsFunTy _ w f a) = do w1   <- repLTy (arrowToHsType w)
                                 f1   <- repLTy f
                                 a1   <- repLTy a
                                 tcon <- repMulArrowTyCon
                                 repTapps tcon [w1, f1, a1]
    repTy (HsListTy _ t)        = do
                                    t1   <- repLTy t
                                    tcon <- repListTyCon
                                    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 (HsSumTy _ tys)       = do tys1 <- repLTys tys
                                     tcon <- repUnboxedSumTyCon (length tys)
                                     repTapps tcon tys1
    repTy (HsOpTy _ ty1 n ty2)  = repLTy ((nlHsTyVar (unLoc n) `nlHsAppTy` ty1)
                                       `nlHsAppTy` ty2)
    repTy (HsParTy _ t)         = repLTy t
    repTy (HsStarTy _ _) =  repTStar
    repTy (HsKindSig _ t k)     = do
                                    t1 <- repLTy t
                                    k1 <- repLTy 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 _) = repTWildCard
    repTy (HsIParamTy _ n t) = do
                                 n' <- rep_implicit_param_name (unLoc n)
                                 t' <- repLTy t
                                 repTImplicitParam n' t'

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

    repTyLit :: HsTyLit -> MetaM (Core (M TH.TyLit))
    repTyLit (HsNumTy _ i) = rep2 numTyLitName [mkIntegerExpr i]
    repTyLit (HsStrTy _ s) = do { s' <- mkStringExprFS s
                                ; rep2 strTyLitName [s']
                                }
    repTyLit (HsCharTy _ c) = do { c' <- return (mkCharExpr c)
                                 ; rep2 charTyLitName [c']
                                 }

    -- | Represent a type wrapped in a Maybe
    repMaybeLTy :: Maybe (LHsKind GhcRn)
                -> MetaM (Core (Maybe (M TH.Type)))
    repMaybeLTy m = do
      k_ty <- wrapName kindTyConName
      repMaybeT k_ty repLTy m

    repRole :: Located (Maybe Role) -> MetaM (Core TH.Role)
    repRole (L _ (Just Nominal))          = rep2_nw nominalRName []
    repRole (L _ (Just Representational)) = rep2_nw representationalRName []
    repRole (L _ (Just Phantom))          = rep2_nw phantomRName []
    repRole (L _ Nothing)                 = rep2_nw inferRName []

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

    repSplice :: HsSplice GhcRn -> MetaM (Core a)
    -- See Note [How brackets and nested splices are handled] in GHC.Tc.Gen.Splice
    -- 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
    repSplice e@(HsSpliced {})          = pprPanic "repSplice" (ppr e)

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

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

    repLEs :: [LHsExpr GhcRn] -> MetaM (Core [(M TH.Exp)])
    repLEs es = repListM expTyConName 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 GhcRn -> MetaM (Core (M TH.Exp))
    repLE (L loc e) = mapReaderT (putSrcSpanDs (locA loc)) (repE e)

    repE :: HsExpr GhcRn -> MetaM (Core (M TH.Exp))
    repE (HsVar _ (L _ x)) =
      do { mb_val <- lift $ dsLookupMetaEnv x
         ; case mb_val of
            Nothing            -> do { str <- lift $ globalVar x
                                     ; repVarOrCon x str }
            Just (DsBound y)   -> repVarOrCon x (coreVar y)
            Just (DsSplice e)  -> do { e' <- lift $ dsExpr e
                                     ; return (MkC e') } }
    repE (HsIPVar _ n) = rep_implicit_param_name n >>= repImplicitParamVar
    repE (HsOverLabel _ s) = repOverLabel s

    repE e@(HsRecFld _ f) = case f of
      Unambiguous x _ -> repE (HsVar noExtField (noLocA x))
      Ambiguous{}     -> notHandled "Ambiguous record selectors" (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 = (L _ [m]) })) = repLambda m
    repE (HsLamCase _ (MG { mg_alts = (L _ ms) }))
                       = do { ms' <- mapM repMatchTup ms
                            ; core_ms <- coreListM matchTyConName ms'
                            ; repLamCase core_ms }
    repE (HsApp _ x y)   = do {a <- repLE x; b <- repLE y; repApp a b}
    repE (HsAppType _ e t) = do { a <- repLE e
                                ; s <- repLTy (hswc_body t)
                                ; repAppType a s }

    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 = (L _ ms) }))
                              = do { arg <- repLE e
                                   ; ms2 <- mapM repMatchTup ms
                                   ; core_ms2 <- coreListM matchTyConName 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 (L _ sts))
     | Just maybeModuleName <- case ctxt of
         { DoExpr m -> Just m; GhciStmtCtxt -> Just Nothing; _ -> Nothing }
     = do { (ss,zs) <- repLSts sts;
            e'      <- repDoE maybeModuleName (nonEmptyCoreList zs);
            wrapGenSyms ss e' }

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

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

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

    repE (ExplicitList _ es) = do { xs <- repLEs es; repListExp xs }
    repE (ExplicitTuple _ es boxity) =
      let tupArgToCoreExp :: HsTupArg GhcRn -> MetaM (Core (Maybe (M TH.Exp)))
          tupArgToCoreExp a
            | (Present _ e) <- a = do { e' <- repLE e
                                      ; coreJustM expTyConName e' }
            | otherwise = coreNothingM expTyConName

      in do { args <- mapM tupArgToCoreExp es
            ; expTy <- wrapName  expTyConName
            ; let maybeExpQTy = mkTyConApp maybeTyCon [expTy]
                  listArg = coreList' maybeExpQTy args
            ; if isBoxed boxity
              then repTup listArg
              else repUnboxedTup listArg }

    repE (ExplicitSum _ alt arity e)
     = do { e1 <- repLE e
          ; repUnboxedSum e1 alt arity }

    repE (RecordCon { rcon_con = c, rcon_flds = flds })
     = do { x <- lookupLOcc c;
            fs <- repFields flds;
            repRecCon x fs }
    repE (RecordUpd { rupd_expr = e, rupd_flds = Left flds })
     = do { x <- repLE e;
            fs <- repUpdFields flds;
            repRecUpd x fs }
    repE (RecordUpd { rupd_flds = Right _ })
      = do
          -- Not possible due to elimination in the renamer. See Note
          -- [Handling overloaded and rebindable constructs]
          panic "The impossible has happened!"

    repE (ExprWithTySig _ e wc_ty)
      = addSimpleTyVarBinds (get_scoped_tvs_from_sig sig_ty) $
        do { e1 <- repLE e
           ; t1 <- rep_ty_sig' sig_ty
           ; repSigExp e1 t1 }
      where
        sig_ty = dropWildCards wc_ty

    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 (HsUnboundVar _ uv)   = do
                                   occ   <- occNameLit uv
                                   sname <- repNameS occ
                                   repUnboundVar sname
    repE (XExpr (HsExpanded orig_expr ds_expr))
      = do { rebindable_on <- lift $ xoptM LangExt.RebindableSyntax
           ; if rebindable_on  -- See Note [Quotation and rebindable syntax]
             then repE ds_expr
             else repE orig_expr }

    repE e@(HsPragE _ (HsPragSCC {}) _) = notHandled "Cost centres" (ppr e)
    repE e                              = notHandled "Expression form" (ppr e)

    {- Note [Quotation and rebindable syntax]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider
      f = [| (* 3) |]

    Because of Note [Handling overloaded and rebindable constructs] in GHC.Rename.Expr,
    the renamer will expand (* 3) to (rightSection (*) 3), regardless of RebindableSyntax.
    Then, concerning the TH quotation,

    * If RebindableSyntax is off, we want the TH quote to generate the section (* 3),
      as the user originally wrote.

    * If RebindableSyntax is on, we perhaps want the TH quote to generate
      (rightSection (*) 3), using whatever 'rightSection' is in scope, because
      (a) RebindableSyntax might not be on in the splicing context
      (b) Even if it is, 'rightSection' might not be in scope
      (c) At least in the case of Typed Template Haskell we should never get
          a type error from the splice.

    We consult the module-wide RebindableSyntax flag here. We could instead record
    the choice in HsExpanded, but it seems simpler to consult the flag (again).
    -}

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

    repMatchTup ::  LMatch GhcRn (LHsExpr GhcRn) -> MetaM (Core (M TH.Match))
    repMatchTup (L _ (Match { m_pats = [p]
                            , m_grhss = GRHSs _ guards wheres })) =
      do { ss1 <- mkGenSyms (collectPatBinders CollNoDictBinders 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 GhcRn (LHsExpr GhcRn) -> MetaM (Core (M TH.Clause))
    repClauseTup (L _ (Match { m_pats = ps
                             , m_grhss = GRHSs _ guards  wheres })) =
      do { ss1 <- mkGenSyms (collectPatsBinders CollNoDictBinders 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 GhcRn (LHsExpr GhcRn)] ->  MetaM (Core (M TH.Body))
    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 GhcRn (LHsExpr GhcRn)
             -> MetaM ([GenSymBind], (Core (M (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 GhcRn -> MetaM (Core [M TH.FieldExp])
    repFields (HsRecFields { rec_flds = flds })
      = repListM fieldExpTyConName rep_fld flds
      where
        rep_fld :: LHsRecField GhcRn (LHsExpr GhcRn)
                -> MetaM (Core (M TH.FieldExp))
        rep_fld (L _ fld) = do { fn <- lookupLOcc (hsRecFieldSel fld)
                               ; e  <- repLE (hsRecFieldArg fld)
                               ; repFieldExp fn e }

    repUpdFields :: [LHsRecUpdField GhcRn] -> MetaM (Core [M TH.FieldExp])
    repUpdFields = repListM fieldExpTyConName rep_fld
      where
        rep_fld :: LHsRecUpdField GhcRn -> MetaM (Core (M TH.FieldExp))
        rep_fld (L l fld) = case unLoc (hsRecFieldLbl fld) of
          Unambiguous sel_name _ -> do { fn <- lookupLOcc (L l sel_name)
                                       ; e  <- repLE (hsRecFieldArg fld)
                                       ; repFieldExp fn e }
          Ambiguous{}            -> notHandled "Ambiguous record updates" (ppr fld)

    -----------------------------------------------------------------------------
    -- 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 shadow, 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 Nothing
    --          [ 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 GhcRn (LHsExpr GhcRn)] -> MetaM ([GenSymBind], [Core (M TH.Stmt)])
    repLSts stmts = repSts (map unLoc stmts)

    repSts :: [Stmt GhcRn (LHsExpr GhcRn)] -> MetaM ([GenSymBind], [Core (M TH.Stmt)])
    repSts (BindStmt _ p e : ss) =
       do { e2 <- repLE e
          ; ss1 <- mkGenSyms (collectPatBinders CollNoDictBinders 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 GhcRn GhcRn
                        -> MetaM ([GenSymBind], Core [(M TH.Stmt)])
         rep_stmt_block (ParStmtBlock _ stmts _ _) =
           do { (ss1, zs) <- repSts (map unLoc stmts)
              ; zs1 <- coreListM stmtTyConName zs
              ; return (ss1, zs1) }
    repSts [LastStmt _ e _ _]
      = do { e2 <- repLE e
           ; z <- repNoBindSt e2
           ; return ([], [z]) }
    repSts (stmt@RecStmt{} : ss)
      = do { let binders = collectLStmtsBinders CollNoDictBinders (unLoc $ recS_stmts stmt)
           ; ss1 <- mkGenSyms binders
           -- Bring all of binders in the recursive group into scope for the
           -- whole group.
           ; (ss1_other,rss) <- addBinds ss1 $ repSts (map unLoc (unLoc $ recS_stmts stmt))
           ; MASSERT(sort ss1 == sort ss1_other)
           ; z <- repRecSt (nonEmptyCoreList rss)
           ; (ss2,zs) <- addBinds ss1 (repSts ss)
           ; return (ss1++ss2, z : zs) }
    repSts []    = return ([],[])
    repSts other = notHandled "Exotic statement" (ppr other)

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

    repBinds :: HsLocalBinds GhcRn -> MetaM ([GenSymBind], Core [(M TH.Dec)])
    repBinds (EmptyLocalBinds _)
      = do  { core_list <- coreListM decTyConName []
            ; return ([], core_list) }

    repBinds (HsIPBinds _ (IPBinds _ decs))
     = do   { ips <- mapM rep_implicit_param_bind decs
            ; core_list <- coreListM decTyConName
                                    (de_loc (sort_by_loc ips))
            ; return ([], core_list)
            }

    repBinds (HsValBinds _ decs)
     = do   { let { bndrs = hsScopedTvBinders decs ++ collectHsValBinders CollNoDictBinders decs }
                    -- No need to worry 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 hsScopedTvBinders see Note [Scoped type variables in quotes]
            ; ss        <- mkGenSyms bndrs
            ; prs       <- addBinds ss (rep_val_binds decs)
            ; core_list <- coreListM decTyConName
                                    (de_loc (sort_by_loc prs))
            ; return (ss, core_list) }

    rep_implicit_param_bind :: LIPBind GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    rep_implicit_param_bind (L loc (IPBind _ ename (L _ rhs)))
     = do { name <- case ename of
                        Left (L _ n) -> rep_implicit_param_name n
                        Right _ ->
                            panic "rep_implicit_param_bind: post typechecking"
          ; rhs' <- repE rhs
          ; ipb <- repImplicitParamBind name rhs'
          ; return (locA loc, ipb) }

    rep_implicit_param_name :: HsIPName -> MetaM (Core String)
    rep_implicit_param_name (HsIPName name) = coreStringLit (unpackFS name)

    rep_val_binds :: HsValBinds GhcRn -> MetaM [(SrcSpan, Core (M TH.Dec))]
    -- Assumes: all the binders of the binding are already in the meta-env
    rep_val_binds (XValBindsLR (NValBinds binds sigs))
     = do { core1 <- rep_binds (unionManyBags (map snd binds))
          ; core2 <- rep_sigs sigs
          ; return (core1 ++ core2) }
    rep_val_binds (ValBinds _ _ _)
     = panic "rep_val_binds: ValBinds"

    rep_binds :: LHsBinds GhcRn -> MetaM [(SrcSpan, Core (M TH.Dec))]
    rep_binds = mapM rep_bind . bagToList

    rep_bind :: LHsBind GhcRn -> MetaM (SrcSpan, Core (M TH.Dec))
    -- Assumes: all the binders of the binding are already 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 _ [L _ (Match
                                       { m_pats = []
                                       , m_grhss = GRHSs _ guards wheres }
                                          )]) } }))
     = do { (ss,wherecore) <- repBinds wheres
            ; guardcore <- addBinds ss (repGuards guards)
            ; fn'  <- lookupNBinder fn
            ; p    <- repPvar fn'
            ; ans  <- repVal p guardcore wherecore
            ; ans' <- wrapGenSyms ss ans
            ; return (locA loc, ans') }

    rep_bind (L loc (FunBind { fun_id = fn
                             , fun_matches = MG { mg_alts = L _ ms } }))
     =   do { ms1 <- mapM repClauseTup ms
            ; fn' <- lookupNBinder fn
            ; ans <- repFun fn' (nonEmptyCoreList ms1)
            ; return (locA 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 (locA 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 <- coreListM decTyConName []
            ; ans <- repVal patcore x empty_decls
            ; return (srcLocSpan (getSrcLoc v), ans) }

    rep_bind (L _ (AbsBinds {}))  = panic "rep_bind: AbsBinds"
    rep_bind (L loc (PatSynBind _ (PSB { psb_id   = syn
                                       , psb_args = args
                                       , psb_def  = pat
                                       , psb_dir  = dir })))
      = do { syn'      <- lookupNBinder syn
           ; dir'      <- repPatSynDir dir
           ; ss        <- mkGenArgSyms args
           ; patSynD'  <- addBinds ss (
             do { args'  <- repPatSynArgs args
                ; pat'   <- repLP pat
                ; repPatSynD syn' args' dir' pat' })
           ; patSynD'' <- wrapGenArgSyms args ss patSynD'
           ; return (locA loc, patSynD'') }
      where
        mkGenArgSyms :: HsPatSynDetails GhcRn -> MetaM [GenSymBind]
        -- for Record Pattern Synonyms we want to conflate the selector
        -- and the pattern-only names in order to provide a nicer TH
        -- API. Whereas inside GHC, record pattern synonym selectors and
        -- their pattern-only bound right hand sides have different names,
        -- we want to treat them the same in TH. This is the reason why we
        -- need an adjusted mkGenArgSyms in the `RecCon` case below.
        mkGenArgSyms (PrefixCon _ args)   = mkGenSyms (map unLoc args)
        mkGenArgSyms (InfixCon arg1 arg2) = mkGenSyms [unLoc arg1, unLoc arg2]
        mkGenArgSyms (RecCon fields)
          = do { let pats = map (unLoc . recordPatSynPatVar) fields
                     sels = map (extFieldOcc . recordPatSynField) fields
               ; ss <- mkGenSyms sels
               ; return $ replaceNames (zip sels pats) ss }

        replaceNames selsPats genSyms
          = [ (pat, id) | (sel, id) <- genSyms, (sel', pat) <- selsPats
                        , sel == sel' ]

        wrapGenArgSyms :: HsPatSynDetails GhcRn
                       -> [GenSymBind] -> Core (M TH.Dec) -> MetaM (Core (M TH.Dec))
        wrapGenArgSyms (RecCon _) _  dec = return dec
        wrapGenArgSyms _          ss dec = wrapGenSyms ss dec

    repPatSynD :: Core TH.Name
               -> Core (M TH.PatSynArgs)
               -> Core (M TH.PatSynDir)
               -> Core (M TH.Pat)
               -> MetaM (Core (M TH.Dec))
    repPatSynD (MkC syn) (MkC args) (MkC dir) (MkC pat)
      = rep2 patSynDName [syn, args, dir, pat]

    repPatSynArgs :: HsPatSynDetails GhcRn -> MetaM (Core (M TH.PatSynArgs))
    repPatSynArgs (PrefixCon _ args)
      = do { args' <- repList nameTyConName lookupLOcc args
           ; repPrefixPatSynArgs args' }
    repPatSynArgs (InfixCon arg1 arg2)
      = do { arg1' <- lookupLOcc arg1
           ; arg2' <- lookupLOcc arg2
           ; repInfixPatSynArgs arg1' arg2' }
    repPatSynArgs (RecCon fields)
      = do { sels' <- repList nameTyConName (lookupOcc . extFieldOcc) sels
           ; repRecordPatSynArgs sels' }
      where sels = map recordPatSynField fields

    repPrefixPatSynArgs :: Core [TH.Name] -> MetaM (Core (M TH.PatSynArgs))
    repPrefixPatSynArgs (MkC nms) = rep2 prefixPatSynName [nms]

    repInfixPatSynArgs :: Core TH.Name -> Core TH.Name -> MetaM (Core (M TH.PatSynArgs))
    repInfixPatSynArgs (MkC nm1) (MkC nm2) = rep2 infixPatSynName [nm1, nm2]

    repRecordPatSynArgs :: Core [TH.Name]
                        -> MetaM (Core (M TH.PatSynArgs))
    repRecordPatSynArgs (MkC sels) = rep2 recordPatSynName [sels]

    repPatSynDir :: HsPatSynDir GhcRn -> MetaM (Core (M TH.PatSynDir))
    repPatSynDir Unidirectional        = rep2 unidirPatSynName []
    repPatSynDir ImplicitBidirectional = rep2 implBidirPatSynName []
    repPatSynDir (ExplicitBidirectional (MG { mg_alts = (L _ clauses) }))
      = do { clauses' <- mapM repClauseTup clauses
           ; repExplBidirPatSynDir (nonEmptyCoreList clauses') }

    repExplBidirPatSynDir :: Core [(M TH.Clause)] -> MetaM (Core (M TH.PatSynDir))
    repExplBidirPatSynDir (MkC cls) = rep2 explBidirPatSynName [cls]

    -----------------------------------------------------------------------------
    -- 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 GhcRn (LHsExpr GhcRn) -> MetaM (Core (M TH.Exp))
    repLambda (L _ (Match { m_pats = ps
                          , m_grhss = GRHSs _ [L _ (GRHS _ [] e)]
                                                  (EmptyLocalBinds _) } ))
     = do { let bndrs = collectPatsBinders CollNoDictBinders 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 lambdas" (pprMatch 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 GhcRn] -> MetaM (Core [(M TH.Pat)])
    repLPs ps = repListM patTyConName repLP ps

    repLP :: LPat GhcRn -> MetaM (Core (M TH.Pat))
    repLP p = repP (unLoc p)

    repP :: Pat GhcRn -> MetaM (Core (M TH.Pat))
    repP (WildPat _)        = repPwild
    repP (LitPat _ l)       = do { l2 <- repLiteral l; repPlit l2 }
    repP (VarPat _ x)       = do { x' <- lookupBinder (unLoc 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' <- lookupNBinder x; p1 <- repLP p
                                 ; repPaspat x' p1 }
    repP (ParPat _ p)       = repLP p
    repP (ListPat Nothing ps)  = do { qs <- repLPs ps; repPlist qs }
    repP (ListPat (Just (SyntaxExprRn e)) ps) = do { p <- repP (ListPat Nothing ps)
                                                   ; e' <- repE e
                                                   ; repPview e' p}
    repP (ListPat _ ps) = pprPanic "repP missing SyntaxExprRn" (ppr ps)
    repP (TuplePat _ ps boxed)
      | isBoxed boxed       = do { qs <- repLPs ps; repPtup qs }
      | otherwise           = do { qs <- repLPs ps; repPunboxedTup qs }
    repP (SumPat _ p alt arity) = do { p1 <- repLP p
                                     ; repPunboxedSum p1 alt arity }
    repP (ConPat NoExtField dc details)
     = do { con_str <- lookupLOcc dc
          ; case details of
             PrefixCon tyargs ps -> do { qs <- repLPs ps
                                       ; ts <- repListM typeTyConName (repTy . unLoc . hsps_body) tyargs
                                       ; repPcon con_str ts qs }
             RecCon rec   -> do { fps <- repListM fieldPatTyConName 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 :: LHsRecField GhcRn (LPat GhcRn) -> MetaM (Core (M (TH.Name, TH.Pat)))
       rep_fld (L _ fld) = do { MkC v <- lookupLOcc (hsRecFieldSel 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 (SigPat _ p t) = do { p' <- repLP p
                             ; t' <- repLTy (hsPatSigType t)
                             ; repPsig 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 = sortBy (SrcLoc.leftmost_smallest `on` fst)

    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] -> MetaM [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) Many var_ty) | nm <- ns] }

    addBinds :: [GenSymBind] -> MetaM a -> MetaM 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 = mapReaderT (dsExtendMetaEnv (mkNameEnv [(n,DsBound id) | (n,id) <- bs])) m

    -- Look up a locally bound name
    --
    lookupNBinder :: LocatedN Name -> MetaM (Core TH.Name)
    lookupNBinder n = lookupBinder (unLoc n)

    lookupBinder :: Name -> MetaM (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 :: GenLocated l Name -> MetaM (Core TH.Name)
    -- Lookup an occurrence; it can't be a splice.
    -- Use the in-scope bindings if they exist
    lookupLOcc n = lookupOcc (unLoc n)

    lookupOcc :: Name -> MetaM (Core TH.Name)
    lookupOcc = lift . lookupOccDsM

    lookupOccDsM :: Name -> DsM (Core TH.Name)
    lookupOccDsM 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 <- nameLit name
            ; rep2_nwDsM mk_varg [pkg,mod,occ] }
      | otherwise
      = do  { MkC occ <- nameLit name
            ; MkC uni <- coreIntegerLit (toInteger $ getKey (getUnique name))
            ; rep2_nwDsM mkNameLName [occ,uni] }
      where
          mod = ASSERT( isExternalName name) nameModule name
          name_mod = moduleNameString (moduleName mod)
          name_pkg = unitString (moduleUnit mod)
          name_occ = nameOccName name
          mk_varg | isDataOcc name_occ = mkNameG_dName
                  | isVarOcc  name_occ = mkNameG_vName
                  | isTcOcc   name_occ = mkNameG_tcName
                  | otherwise          = pprPanic "GHC.HsToCore.Quote.globalVar" (ppr name)

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

    wrapGenSyms :: [GenSymBind]
                -> Core (M a) -> MetaM (Core (M 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) = tcSplitAppTy (exprType b)
            -- b :: m a, so we can get the type 'a' by looking at the
            -- argument type. Need to use `tcSplitAppTy` here as since
            -- the overloaded quotations patch the type of the expression can
            -- be something more complicated than just `Q a`.
            -- See #17839 for when this went wrong with the type `WriterT () m a`

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

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

    occNameLit :: OccName -> MetaM (Core String)
    occNameLit name = coreStringLit (occNameString name)

    -- %*********************************************************************
    -- %*                                                                   *
    --              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

    type family NotM a where
      NotM (M _) = TypeError ('Text ("rep2_nw must not produce something of overloaded type"))
      NotM _other = (() :: Constraint)

    rep2M :: Name -> [CoreExpr] -> MetaM (Core (M a))
    rep2 :: Name -> [CoreExpr] -> MetaM (Core (M a))
    rep2_nw :: NotM a => Name -> [CoreExpr] -> MetaM (Core a)
    rep2_nwDsM :: NotM a => Name -> [CoreExpr] -> DsM (Core a)
    rep2 = rep2X lift (asks quoteWrapper)
    rep2M = rep2X lift (asks monadWrapper)
    rep2_nw n xs = lift (rep2_nwDsM n xs)
    rep2_nwDsM = rep2X id (return id)

    rep2X :: Monad m => (forall z . DsM z -> m z)
          -> m (CoreExpr -> CoreExpr)
          -> Name
          -> [ CoreExpr ]
          -> m (Core a)
    rep2X lift_dsm get_wrap n xs = do
      { rep_id <- lift_dsm $ dsLookupGlobalId n
      ; wrap <- get_wrap
      ; return (MkC $ (foldl' App (wrap (Var rep_id)) xs)) }

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

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

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

    --------------- Patterns -----------------
    repPlit   :: Core TH.Lit -> MetaM (Core (M TH.Pat))
    repPlit (MkC l) = rep2 litPName [l]

    repPvar :: Core TH.Name -> MetaM (Core (M TH.Pat))
    repPvar (MkC s) = rep2 varPName [s]

    repPtup :: Core [(M TH.Pat)] -> MetaM (Core (M TH.Pat))
    repPtup (MkC ps) = rep2 tupPName [ps]

    repPunboxedTup :: Core [(M TH.Pat)] -> MetaM (Core (M TH.Pat))
    repPunboxedTup (MkC ps) = rep2 unboxedTupPName [ps]

    repPunboxedSum :: Core (M TH.Pat) -> TH.SumAlt -> TH.SumArity -> MetaM (Core (M TH.Pat))
    -- Note: not Core TH.SumAlt or Core TH.SumArity; it's easier to be direct here
    repPunboxedSum (MkC p) alt arity
     = do { platform <- getPlatform
          ; rep2 unboxedSumPName [ p
                                 , mkIntExprInt platform alt
                                 , mkIntExprInt platform arity ] }

    repPcon   :: Core TH.Name -> Core [(M TH.Type)] -> Core [(M TH.Pat)] -> MetaM (Core (M TH.Pat))
    repPcon (MkC s) (MkC ts) (MkC ps) = rep2 conPName [s, ts, ps]

    repPrec   :: Core TH.Name -> Core [M (TH.Name, TH.Pat)] -> MetaM (Core (M TH.Pat))
    repPrec (MkC c) (MkC rps) = rep2 recPName [c,rps]

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

    repPtilde :: Core (M TH.Pat) -> MetaM (Core (M TH.Pat))
    repPtilde (MkC p) = rep2 tildePName [p]

    repPbang :: Core (M TH.Pat) -> MetaM (Core (M TH.Pat))
    repPbang (MkC p) = rep2 bangPName [p]

    repPaspat :: Core TH.Name -> Core (M TH.Pat) -> MetaM (Core (M TH.Pat))
    repPaspat (MkC s) (MkC p) = rep2 asPName [s, p]

    repPwild  :: MetaM (Core (M TH.Pat))
    repPwild = rep2 wildPName []

    repPlist :: Core [(M TH.Pat)] -> MetaM (Core (M TH.Pat))
    repPlist (MkC ps) = rep2 listPName [ps]

    repPview :: Core (M TH.Exp) -> Core (M TH.Pat) -> MetaM (Core (M TH.Pat))
    repPview (MkC e) (MkC p) = rep2 viewPName [e,p]

    repPsig :: Core (M TH.Pat) -> Core (M TH.Type) -> MetaM (Core (M TH.Pat))
    repPsig (MkC p) (MkC t) = rep2 sigPName [p, t]

    --------------- Expressions -----------------
    repVarOrCon :: Name -> Core TH.Name -> MetaM (Core (M TH.Exp))
    repVarOrCon vc str
        | isVarNameSpace ns = repVar str  -- Both type and term variables (#18740)
        | otherwise         = repCon str
      where
        ns = nameNameSpace vc

    repVar :: Core TH.Name -> MetaM (Core (M TH.Exp))
    repVar (MkC s) = rep2 varEName [s]

    repCon :: Core TH.Name -> MetaM (Core (M TH.Exp))
    repCon (MkC s) = rep2 conEName [s]

    repLit :: Core TH.Lit -> MetaM (Core (M TH.Exp))
    repLit (MkC c) = rep2 litEName [c]

    repApp :: Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repApp (MkC x) (MkC y) = rep2 appEName [x,y]

    repAppType :: Core (M TH.Exp) -> Core (M TH.Type) -> MetaM (Core (M TH.Exp))
    repAppType (MkC x) (MkC y) = rep2 appTypeEName [x,y]

    repLam :: Core [(M TH.Pat)] -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repLam (MkC ps) (MkC e) = rep2 lamEName [ps, e]

    repLamCase :: Core [(M TH.Match)] -> MetaM (Core (M TH.Exp))
    repLamCase (MkC ms) = rep2 lamCaseEName [ms]

    repTup :: Core [Maybe (M TH.Exp)] -> MetaM (Core (M TH.Exp))
    repTup (MkC es) = rep2 tupEName [es]

    repUnboxedTup :: Core [Maybe (M TH.Exp)] -> MetaM (Core (M TH.Exp))
    repUnboxedTup (MkC es) = rep2 unboxedTupEName [es]

    repUnboxedSum :: Core (M TH.Exp) -> TH.SumAlt -> TH.SumArity -> MetaM (Core (M TH.Exp))
    -- Note: not Core TH.SumAlt or Core TH.SumArity; it's easier to be direct here
    repUnboxedSum (MkC e) alt arity
     = do { platform <- getPlatform
          ; rep2 unboxedSumEName [ e
                                 , mkIntExprInt platform alt
                                 , mkIntExprInt platform arity ] }

    repCond :: Core (M TH.Exp) -> Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repCond (MkC x) (MkC y) (MkC z) = rep2 condEName [x,y,z]

    repMultiIf :: Core [M (TH.Guard, TH.Exp)] -> MetaM (Core (M TH.Exp))
    repMultiIf (MkC alts) = rep2 multiIfEName [alts]

    repLetE :: Core [(M TH.Dec)] -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repLetE (MkC ds) (MkC e) = rep2 letEName [ds, e]

    repCaseE :: Core (M TH.Exp) -> Core [(M TH.Match)] -> MetaM (Core (M TH.Exp))
    repCaseE (MkC e) (MkC ms) = rep2 caseEName [e, ms]

    repDoE :: Maybe ModuleName -> Core [(M TH.Stmt)] -> MetaM (Core (M TH.Exp))
    repDoE = repDoBlock doEName

    repMDoE :: Maybe ModuleName -> Core [(M TH.Stmt)] -> MetaM (Core (M TH.Exp))
    repMDoE = repDoBlock mdoEName

    repDoBlock :: Name -> Maybe ModuleName -> Core [(M TH.Stmt)] -> MetaM (Core (M TH.Exp))
    repDoBlock doName maybeModName (MkC ss) = do
        MkC coreModName <- coreModNameM
        rep2 doName [coreModName, ss]
      where
        coreModNameM :: MetaM (Core (Maybe TH.ModName))
        coreModNameM = case maybeModName of
          Just m -> do
            MkC s <- coreStringLit (moduleNameString m)
            mName <- rep2_nw mkModNameName [s]
            coreJust modNameTyConName mName
          _ -> coreNothing modNameTyConName

    repComp :: Core [(M TH.Stmt)] -> MetaM (Core (M TH.Exp))
    repComp (MkC ss) = rep2 compEName [ss]

    repListExp :: Core [(M TH.Exp)] -> MetaM (Core (M TH.Exp))
    repListExp (MkC es) = rep2 listEName [es]

    repSigExp :: Core (M TH.Exp) -> Core (M TH.Type) -> MetaM (Core (M TH.Exp))
    repSigExp (MkC e) (MkC t) = rep2 sigEName [e,t]

    repRecCon :: Core TH.Name -> Core [M TH.FieldExp]-> MetaM (Core (M TH.Exp))
    repRecCon (MkC c) (MkC fs) = rep2 recConEName [c,fs]

    repRecUpd :: Core (M TH.Exp) -> Core [M TH.FieldExp] -> MetaM (Core (M TH.Exp))
    repRecUpd (MkC e) (MkC fs) = rep2 recUpdEName [e,fs]

    repFieldExp :: Core TH.Name -> Core (M TH.Exp) -> MetaM (Core (M TH.FieldExp))
    repFieldExp (MkC n) (MkC x) = rep2 fieldExpName [n,x]

    repInfixApp :: Core (M TH.Exp) -> Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repInfixApp (MkC x) (MkC y) (MkC z) = rep2 infixAppName [x,y,z]

    repSectionL :: Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repSectionL (MkC x) (MkC y) = rep2 sectionLName [x,y]

    repSectionR :: Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repSectionR (MkC x) (MkC y) = rep2 sectionRName [x,y]

    repImplicitParamVar :: Core String -> MetaM (Core (M TH.Exp))
    repImplicitParamVar (MkC x) = rep2 implicitParamVarEName [x]

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

    repNormal :: Core (M TH.Exp) -> MetaM (Core (M TH.Body))
    repNormal (MkC e) = rep2 normalBName [e]

    ------------ Guards ----
    repLNormalGE :: LHsExpr GhcRn -> LHsExpr GhcRn
                 -> MetaM (Core (M (TH.Guard, TH.Exp)))
    repLNormalGE g e = do g' <- repLE g
                          e' <- repLE e
                          repNormalGE g' e'

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

    repPatGE :: Core [(M TH.Stmt)] -> Core (M TH.Exp) -> MetaM (Core (M (TH.Guard, TH.Exp)))
    repPatGE (MkC ss) (MkC e) = rep2 patGEName [ss, e]

    ------------- Stmts -------------------
    repBindSt :: Core (M TH.Pat) -> Core (M TH.Exp) -> MetaM (Core (M TH.Stmt))
    repBindSt (MkC p) (MkC e) = rep2 bindSName [p,e]

    repLetSt :: Core [(M TH.Dec)] -> MetaM (Core (M TH.Stmt))
    repLetSt (MkC ds) = rep2 letSName [ds]

    repNoBindSt :: Core (M TH.Exp) -> MetaM (Core (M TH.Stmt))
    repNoBindSt (MkC e) = rep2 noBindSName [e]

    repParSt :: Core [[(M TH.Stmt)]] -> MetaM (Core (M TH.Stmt))
    repParSt (MkC sss) = rep2 parSName [sss]

    repRecSt :: Core [(M TH.Stmt)] -> MetaM (Core (M TH.Stmt))
    repRecSt (MkC ss) = rep2 recSName [ss]

    -------------- Range (Arithmetic sequences) -----------
    repFrom :: Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repFrom (MkC x) = rep2 fromEName [x]

    repFromThen :: Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repFromThen (MkC x) (MkC y) = rep2 fromThenEName [x,y]

    repFromTo :: Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repFromTo (MkC x) (MkC y) = rep2 fromToEName [x,y]

    repFromThenTo :: Core (M TH.Exp) -> Core (M TH.Exp) -> Core (M TH.Exp) -> MetaM (Core (M TH.Exp))
    repFromThenTo (MkC x) (MkC y) (MkC z) = rep2 fromThenToEName [x,y,z]

    ------------ Match and Clause Tuples -----------
    repMatch :: Core (M TH.Pat) -> Core (M TH.Body) -> Core [(M TH.Dec)] -> MetaM (Core (M TH.Match))
    repMatch (MkC p) (MkC bod) (MkC ds) = rep2 matchName [p, bod, ds]

    repClause :: Core [(M TH.Pat)] -> Core (M TH.Body) -> Core [(M TH.Dec)] -> MetaM (Core (M TH.Clause))
    repClause (MkC ps) (MkC bod) (MkC ds) = rep2 clauseName [ps, bod, ds]

    -------------- Dec -----------------------------
    repVal :: Core (M TH.Pat) -> Core (M TH.Body) -> Core [(M TH.Dec)] -> MetaM (Core (M TH.Dec))
    repVal (MkC p) (MkC b) (MkC ds) = rep2 valDName [p, b, ds]

    repFun :: Core TH.Name -> Core [(M TH.Clause)] -> MetaM (Core (M TH.Dec))
    repFun (MkC nm) (MkC b) = rep2 funDName [nm, b]

    repData :: Core (M TH.Cxt) -> Core TH.Name
            -> Either (Core [(M (TH.TyVarBndr ()))])
                      (Core (Maybe [(M (TH.TyVarBndr ()))]), Core (M TH.Type))
            -> Core (Maybe (M TH.Kind)) -> Core [(M TH.Con)] -> Core [M TH.DerivClause]
            -> MetaM (Core (M TH.Dec))
    repData (MkC cxt) (MkC nm) (Left (MkC tvs)) (MkC ksig) (MkC cons) (MkC derivs)
      = rep2 dataDName [cxt, nm, tvs, ksig, cons, derivs]
    repData (MkC cxt) (MkC _) (Right (MkC mb_bndrs, MkC ty)) (MkC ksig) (MkC cons)
            (MkC derivs)
      = rep2 dataInstDName [cxt, mb_bndrs, ty, ksig, cons, derivs]

    repNewtype :: Core (M TH.Cxt) -> Core TH.Name
               -> Either (Core [(M (TH.TyVarBndr ()))])
                         (Core (Maybe [(M (TH.TyVarBndr ()))]), Core (M TH.Type))
               -> Core (Maybe (M TH.Kind)) -> Core (M TH.Con) -> Core [M TH.DerivClause]
               -> MetaM (Core (M TH.Dec))
    repNewtype (MkC cxt) (MkC nm) (Left (MkC tvs)) (MkC ksig) (MkC con)
               (MkC derivs)
      = rep2 newtypeDName [cxt, nm, tvs, ksig, con, derivs]
    repNewtype (MkC cxt) (MkC _) (Right (MkC mb_bndrs, MkC ty)) (MkC ksig) (MkC con)
               (MkC derivs)
      = rep2 newtypeInstDName [cxt, mb_bndrs, ty, ksig, con, derivs]

    repTySyn :: Core TH.Name -> Core [(M (TH.TyVarBndr ()))]
             -> Core (M TH.Type) -> MetaM (Core (M TH.Dec))
    repTySyn (MkC nm) (MkC tvs) (MkC rhs)
      = rep2 tySynDName [nm, tvs, rhs]

    repInst :: Core (Maybe TH.Overlap) ->
               Core (M TH.Cxt) -> Core (M TH.Type) -> Core [(M TH.Dec)] -> MetaM (Core (M TH.Dec))
    repInst (MkC o) (MkC cxt) (MkC ty) (MkC ds) = rep2 instanceWithOverlapDName
                                                                  [o, cxt, ty, ds]

    repDerivStrategy :: Maybe (LDerivStrategy GhcRn)
                     -> (Core (Maybe (M TH.DerivStrategy)) -> MetaM (Core (M a)))
                     -> MetaM (Core (M a))
    repDerivStrategy mds thing_inside =
      case mds of
        Nothing -> thing_inside =<< nothing
        Just ds ->
          case unLoc ds of
            StockStrategy    _ -> thing_inside =<< just =<< repStockStrategy
            AnyclassStrategy _ -> thing_inside =<< just =<< repAnyclassStrategy
            NewtypeStrategy  _ -> thing_inside =<< just =<< repNewtypeStrategy
            ViaStrategy ty     -> addSimpleTyVarBinds (get_scoped_tvs_from_sig ty) $
                                  do ty' <- rep_ty_sig' ty
                                     via_strat <- repViaStrategy ty'
                                     m_via_strat <- just via_strat
                                     thing_inside m_via_strat
      where
      nothing = coreNothingM derivStrategyTyConName
      just    = coreJustM    derivStrategyTyConName

    repStockStrategy :: MetaM (Core (M TH.DerivStrategy))
    repStockStrategy = rep2 stockStrategyName []

    repAnyclassStrategy :: MetaM (Core (M TH.DerivStrategy))
    repAnyclassStrategy = rep2 anyclassStrategyName []

    repNewtypeStrategy :: MetaM (Core (M TH.DerivStrategy))
    repNewtypeStrategy = rep2 newtypeStrategyName []

    repViaStrategy :: Core (M TH.Type) -> MetaM (Core (M TH.DerivStrategy))
    repViaStrategy (MkC t) = rep2 viaStrategyName [t]

    repOverlap :: Maybe OverlapMode -> MetaM (Core (Maybe TH.Overlap))
    repOverlap mb =
      case mb of
        Nothing -> nothing
        Just o ->
          case o of
            NoOverlap _    -> nothing
            Overlappable _ -> just =<< dataCon overlappableDataConName
            Overlapping _  -> just =<< dataCon overlappingDataConName
            Overlaps _     -> just =<< dataCon overlapsDataConName
            Incoherent _   -> just =<< dataCon incoherentDataConName
      where
      nothing = coreNothing overlapTyConName
      just    = coreJust overlapTyConName

    repClass :: Core (M TH.Cxt) -> Core TH.Name -> Core [(M (TH.TyVarBndr ()))]
             -> Core [TH.FunDep] -> Core [(M TH.Dec)]
             -> MetaM (Core (M TH.Dec))
    repClass (MkC cxt) (MkC cls) (MkC tvs) (MkC fds) (MkC ds)
      = rep2 classDName [cxt, cls, tvs, fds, ds]

    repDeriv :: Core (Maybe (M TH.DerivStrategy))
             -> Core (M TH.Cxt) -> Core (M TH.Type)
             -> MetaM (Core (M TH.Dec))
    repDeriv (MkC ds) (MkC cxt) (MkC ty)
      = rep2 standaloneDerivWithStrategyDName [ds, cxt, ty]

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

    repPragSpec :: Core TH.Name -> Core (M TH.Type) -> Core TH.Phases
                -> MetaM (Core (M TH.Dec))
    repPragSpec (MkC nm) (MkC ty) (MkC phases)
      = rep2 pragSpecDName [nm, ty, phases]

    repPragSpecInl :: Core TH.Name -> Core (M TH.Type) -> Core TH.Inline
                   -> Core TH.Phases -> MetaM (Core (M TH.Dec))
    repPragSpecInl (MkC nm) (MkC ty) (MkC inline) (MkC phases)
      = rep2 pragSpecInlDName [nm, ty, inline, phases]

    repPragSpecInst :: Core (M TH.Type) -> MetaM (Core (M TH.Dec))
    repPragSpecInst (MkC ty) = rep2 pragSpecInstDName [ty]

    repPragComplete :: Core [TH.Name] -> Core (Maybe TH.Name) -> MetaM (Core (M TH.Dec))
    repPragComplete (MkC cls) (MkC mty) = rep2 pragCompleteDName [cls, mty]

    repPragRule :: Core String -> Core (Maybe [(M (TH.TyVarBndr ()))])
                -> Core [(M TH.RuleBndr)] -> Core (M TH.Exp) -> Core (M TH.Exp)
                -> Core TH.Phases -> MetaM (Core (M TH.Dec))
    repPragRule (MkC nm) (MkC ty_bndrs) (MkC tm_bndrs) (MkC lhs) (MkC rhs) (MkC phases)
      = rep2 pragRuleDName [nm, ty_bndrs, tm_bndrs, lhs, rhs, phases]

    repPragAnn :: Core TH.AnnTarget -> Core (M TH.Exp) -> MetaM (Core (M TH.Dec))
    repPragAnn (MkC targ) (MkC e) = rep2 pragAnnDName [targ, e]

    repTySynInst :: Core (M TH.TySynEqn) -> MetaM (Core (M TH.Dec))
    repTySynInst (MkC eqn)
        = rep2 tySynInstDName [eqn]

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

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

    repClosedFamilyD :: Core TH.Name
                     -> Core [(M (TH.TyVarBndr ()))]
                     -> Core (M TH.FamilyResultSig)
                     -> Core (Maybe TH.InjectivityAnn)
                     -> Core [(M TH.TySynEqn)]
                     -> MetaM (Core (M TH.Dec))
    repClosedFamilyD (MkC nm) (MkC tvs) (MkC res) (MkC inj) (MkC eqns)
        = rep2 closedTypeFamilyDName [nm, tvs, res, inj, eqns]

    repTySynEqn :: Core (Maybe [(M (TH.TyVarBndr ()))]) ->
                   Core (M TH.Type) -> Core (M TH.Type) -> MetaM (Core (M TH.TySynEqn))
    repTySynEqn (MkC mb_bndrs) (MkC lhs) (MkC rhs)
      = rep2 tySynEqnName [mb_bndrs, lhs, rhs]

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

    repFunDep :: Core [TH.Name] -> Core [TH.Name] -> MetaM (Core TH.FunDep)
    repFunDep (MkC xs) (MkC ys) = rep2_nw funDepName [xs, ys]

    repProto :: Name -> Core TH.Name -> Core (M TH.Type) -> MetaM (Core (M TH.Dec))
    repProto mk_sig (MkC s) (MkC ty) = rep2 mk_sig [s, ty]

    repImplicitParamBind :: Core String -> Core (M TH.Exp) -> MetaM (Core (M TH.Dec))
    repImplicitParamBind (MkC n) (MkC e) = rep2 implicitParamBindDName [n, e]

    repCtxt :: Core [(M TH.Pred)] -> MetaM (Core (M TH.Cxt))
    repCtxt (MkC tys) = rep2 cxtName [tys]

    repH98DataCon :: LocatedN Name
                  -> HsConDeclH98Details GhcRn
                  -> MetaM (Core (M TH.Con))
    repH98DataCon con details
        = do con' <- lookupLOcc con -- See Note [Binders and occurrences]
             case details of
               PrefixCon _ ps -> do
                 arg_tys <- repPrefixConArgs ps
                 rep2 normalCName [unC con', unC arg_tys]
               InfixCon st1 st2 -> do
                 arg1 <- repBangTy (hsScaledThing st1)
                 arg2 <- repBangTy (hsScaledThing st2)
                 rep2 infixCName [unC arg1, unC con', unC arg2]
               RecCon ips -> do
                 arg_vtys <- repRecConArgs ips
                 rep2 recCName [unC con', unC arg_vtys]

    repGadtDataCons :: [LocatedN Name]
                    -> HsConDeclGADTDetails GhcRn
                    -> LHsType GhcRn
                    -> MetaM (Core (M TH.Con))
    repGadtDataCons cons details res_ty
        = do cons' <- mapM lookupLOcc cons -- See Note [Binders and occurrences]
             case details of
               PrefixConGADT ps -> do
                 arg_tys <- repPrefixConArgs ps
                 res_ty' <- repLTy res_ty
                 rep2 gadtCName [ unC (nonEmptyCoreList cons'), unC arg_tys, unC res_ty']
               RecConGADT ips -> do
                 arg_vtys <- repRecConArgs ips
                 res_ty'  <- repLTy res_ty
                 rep2 recGadtCName [unC (nonEmptyCoreList cons'), unC arg_vtys,
                                    unC res_ty']

    -- Desugar the arguments in a data constructor declared with prefix syntax.
    repPrefixConArgs :: [HsScaled GhcRn (LHsType GhcRn)]
                     -> MetaM (Core [M TH.BangType])
    repPrefixConArgs ps = repListM bangTypeTyConName repBangTy (map hsScaledThing ps)

    -- Desugar the arguments in a data constructor declared with record syntax.
    repRecConArgs :: LocatedL [LConDeclField GhcRn]
                  -> MetaM (Core [M TH.VarBangType])
    repRecConArgs ips = do
      args     <- concatMapM rep_ip (unLoc ips)
      coreListM varBangTypeTyConName args
        where
          rep_ip (L _ ip) = mapM (rep_one_ip (cd_fld_type ip)) (cd_fld_names ip)

          rep_one_ip :: LBangType GhcRn -> LFieldOcc GhcRn -> MetaM (Core (M TH.VarBangType))
          rep_one_ip t n = do { MkC v  <- lookupOcc (extFieldOcc $ unLoc n)
                              ; MkC ty <- repBangTy  t
                              ; rep2 varBangTypeName [v,ty] }

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

    repTForall :: Core [(M (TH.TyVarBndr TH.Specificity))] -> Core (M TH.Cxt) -> Core (M TH.Type)
               -> MetaM (Core (M TH.Type))
    repTForall (MkC tvars) (MkC ctxt) (MkC ty)
        = rep2 forallTName [tvars, ctxt, ty]

    repTForallVis :: Core [(M (TH.TyVarBndr ()))] -> Core (M TH.Type)
                  -> MetaM (Core (M TH.Type))
    repTForallVis (MkC tvars) (MkC ty) = rep2 forallVisTName [tvars, ty]

    repTvar :: Core TH.Name -> MetaM (Core (M TH.Type))
    repTvar (MkC s) = rep2 varTName [s]

    repTapp :: Core (M TH.Type) -> Core (M TH.Type) -> MetaM (Core (M TH.Type))
    repTapp (MkC t1) (MkC t2) = rep2 appTName [t1, t2]

    repTappKind :: Core (M TH.Type) -> Core (M TH.Kind) -> MetaM (Core (M TH.Type))
    repTappKind (MkC ty) (MkC ki) = rep2 appKindTName [ty,ki]

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

    repTSig :: Core (M TH.Type) -> Core (M TH.Kind) -> MetaM (Core (M TH.Type))
    repTSig (MkC ty) (MkC ki) = rep2 sigTName [ty, ki]

    repTequality :: MetaM (Core (M TH.Type))
    repTequality = rep2 equalityTName []

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

    repTLit :: Core (M TH.TyLit) -> MetaM (Core (M TH.Type))
    repTLit (MkC lit) = rep2 litTName [lit]

    repTWildCard :: MetaM (Core (M TH.Type))
    repTWildCard = rep2 wildCardTName []

    repTImplicitParam :: Core String -> Core (M TH.Type) -> MetaM (Core (M TH.Type))
    repTImplicitParam (MkC n) (MkC e) = rep2 implicitParamTName [n, e]

    repTStar :: MetaM (Core (M TH.Type))
    repTStar = rep2 starKName []

    repTConstraint :: MetaM (Core (M TH.Type))
    repTConstraint = rep2 constraintKName []

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

    repNamedTyCon :: Core TH.Name -> MetaM (Core (M TH.Type))
    repNamedTyCon (MkC s) = rep2 conTName [s]

    repTInfix :: Core (M TH.Type) -> Core TH.Name -> Core (M TH.Type)
                 -> MetaM (Core (M TH.Type))
    repTInfix (MkC t1) (MkC name) (MkC t2) = rep2 infixTName [t1,name,t2]

    repTupleTyCon :: Int -> MetaM (Core (M TH.Type))
    -- Note: not Core Int; it's easier to be direct here
    repTupleTyCon i = do platform <- getPlatform
                         rep2 tupleTName [mkIntExprInt platform i]

    repUnboxedTupleTyCon :: Int -> MetaM (Core (M TH.Type))
    -- Note: not Core Int; it's easier to be direct here
    repUnboxedTupleTyCon i = do platform <- getPlatform
                                rep2 unboxedTupleTName [mkIntExprInt platform i]

    repUnboxedSumTyCon :: TH.SumArity -> MetaM (Core (M TH.Type))
    -- Note: not Core TH.SumArity; it's easier to be direct here
    repUnboxedSumTyCon arity = do platform <- getPlatform
                                  rep2 unboxedSumTName [mkIntExprInt platform arity]

    repArrowTyCon :: MetaM (Core (M TH.Type))
    repArrowTyCon = rep2 arrowTName []

    repMulArrowTyCon :: MetaM (Core (M TH.Type))
    repMulArrowTyCon = rep2 mulArrowTName []

    repListTyCon :: MetaM (Core (M TH.Type))
    repListTyCon = rep2 listTName []

    repPromotedDataCon :: Core TH.Name -> MetaM (Core (M TH.Type))
    repPromotedDataCon (MkC s) = rep2 promotedTName [s]

    repPromotedTupleTyCon :: Int -> MetaM (Core (M TH.Type))
    repPromotedTupleTyCon i = do platform <- getPlatform
                                 rep2 promotedTupleTName [mkIntExprInt platform i]

    repPromotedNilTyCon :: MetaM (Core (M TH.Type))
    repPromotedNilTyCon = rep2 promotedNilTName []

    repPromotedConsTyCon :: MetaM (Core (M TH.Type))
    repPromotedConsTyCon = rep2 promotedConsTName []

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

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

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

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

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

    repLiteral :: HsLit GhcRn -> MetaM (Core TH.Lit)
    repLiteral (HsStringPrim _ bs)
      = do word8_ty <- lookupType word8TyConName
           let w8s = unpack bs
               w8s_expr = map (\w8 -> mkCoreConApps word8DataCon
                                      [mkWord8Lit (toInteger w8)]) w8s
           rep2_nw 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 (il_value i)
                       HsFloatPrim _ r  -> mk_rational r
                       HsDoublePrim _ r -> mk_rational r
                       HsCharPrim _ c   -> mk_char c
                       _ -> return lit
           lit_expr <- lift $ dsLit lit'
           case mb_lit_name of
              Just lit_name -> rep2_nw 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 -> MetaM (HsLit GhcRn)
    mk_integer  i = return $ HsInteger NoSourceText i integerTy

    mk_rational :: FractionalLit -> MetaM (HsLit GhcRn)
    mk_rational r = do rat_ty <- lookupType rationalTyConName
                       return $ HsRat noExtField r rat_ty
    mk_string :: FastString -> MetaM (HsLit GhcRn)
    mk_string s = return $ HsString NoSourceText s

    mk_char :: Char -> MetaM (HsLit GhcRn)
    mk_char c = return $ HsChar NoSourceText c

    repOverloadedLiteral :: HsOverLit GhcRn -> MetaM (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 -> MetaM (HsLit GhcRn)
    mk_lit (HsIntegral i)     = mk_integer  (il_value i)
    mk_lit (HsFractional f)   = mk_rational f
    mk_lit (HsIsString _ s)   = mk_string   s

    repNameS :: Core String -> MetaM (Core TH.Name)
    repNameS (MkC name) = rep2_nw mkNameSName [name]

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

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

    repBindM :: Type -> Type        -- a and b
             -> Core (M a) -> Core (a -> M b) -> MetaM (Core (M b))
    repBindM ty_a ty_b (MkC x) (MkC y)
      = rep2M bindMName [Type ty_a, Type ty_b, x, y]

    repSequenceM :: Type -> Core [M a] -> MetaM (Core (M [a]))
    repSequenceM ty_a (MkC list)
      = rep2M sequenceQName [Type ty_a, list]

    repUnboundVar :: Core TH.Name -> MetaM (Core (M TH.Exp))
    repUnboundVar (MkC name) = rep2 unboundVarEName [name]

    repOverLabel :: FastString -> MetaM (Core (M TH.Exp))
    repOverLabel fs = do
                        (MkC s) <- coreStringLit $ unpackFS fs
                        rep2 labelEName [s]

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

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

    -- Create a list of m a values
    repListM :: Name -> (a  -> MetaM (Core b))
                        -> [a] -> MetaM (Core [b])
    repListM tc_name f args
      = do { ty <- wrapName tc_name
           ; args1 <- mapM f args
           ; return $ coreList' ty args1 }

    coreListM :: Name -> [Core a] -> MetaM (Core [a])
    coreListM tc as = repListM tc return as

    coreList :: Name    -- Of the TyCon of the element type
             -> [Core a] -> MetaM (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 :: MonadThings m => String -> m (Core String)
    coreStringLit s = do { z <- mkStringExpr s; return(MkC z) }

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

    repMaybe :: Name -> (a -> MetaM (Core b))
                        -> Maybe a -> MetaM (Core (Maybe b))
    repMaybe tc_name f m = do
      t <- lookupType tc_name
      repMaybeT t f m

    repMaybeT :: Type -> (a -> MetaM (Core b))
                        -> Maybe a -> MetaM (Core (Maybe b))
    repMaybeT ty _ Nothing   = return $ coreNothing' ty
    repMaybeT ty f (Just es) = coreJust' ty <$> f es

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

    coreNothingM :: Name -> MetaM (Core (Maybe a))
    coreNothingM tc_name =
        do { elt_ty <- wrapName 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 -> MetaM (Core (Maybe a))
    coreJust tc_name es
      = do { elt_ty <- lookupType tc_name; return (coreJust' elt_ty es) }

    coreJustM :: Name -> Core a -> MetaM (Core (Maybe a))
    coreJustM tc_name es = do { elt_ty <- wrapName 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))

    ------------------- Maybe Lists ------------------

    coreJustList :: Type -> Core [a] -> Core (Maybe [a])
    coreJustList elt_ty = coreJust' (mkListTy elt_ty)

    coreNothingList :: Type -> Core (Maybe [a])
    coreNothingList elt_ty = coreNothing' (mkListTy elt_ty)

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

    coreIntLit :: Int -> MetaM (Core Int)
    coreIntLit i = do platform <- getPlatform
                      return (MkC (mkIntExprInt platform i))

    coreIntegerLit :: MonadThings m => Integer -> m (Core Integer)
    coreIntegerLit i = pure (MkC (mkIntegerExpr i))

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

    ----------------- Failure -----------------------
    notHandledL :: SrcSpan -> String -> SDoc -> MetaM a
    notHandledL loc what doc
      | isGoodSrcSpan loc
      = mapReaderT (putSrcSpanDs loc) $ notHandled what doc
      | otherwise
      = notHandled what doc

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