DsMeta.hs 97.7 KB
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{-# LANGUAGE CPP, TypeFamilies #-}
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-----------------------------------------------------------------------------
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--
-- (c) The University of Glasgow 2006
--
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-- 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.
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--
-- It also defines a bunch of knownKeyNames, in the same way as is done
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-- in prelude/PrelNames.  It's much more convenient to do it here, because
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-- otherwise we have to recompile PrelNames whenever we add a Name, which is
-- a Royal Pain (triggers other recompilation).
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-----------------------------------------------------------------------------

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module DsMeta( dsBracket ) where
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#include "HsVersions.h"

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

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import qualified Language.Haskell.TH as TH
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import HsSyn
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import Class
import PrelNames
-- To avoid clashes with DsMeta.varName we must make a local alias for
-- OccName.varName we do this by removing varName from the import of
-- OccName above, making a qualified instance of OccName and using
-- OccNameAlias.varName where varName ws previously used in this file.
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import qualified OccName( isDataOcc, isVarOcc, isTcOcc )
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import Module
import Id
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import Name hiding( isVarOcc, isTcOcc, varName, tcName )
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import THNames
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import NameEnv
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import NameSet
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import TcType
import TyCon
import TysWiredIn
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import CoreSyn
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import MkCore
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import CoreUtils
import SrcLoc
import Unique
import BasicTypes
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import Outputable
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import Bag
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import DynFlags
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import FastString
import ForeignCall
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import Util
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import Maybes
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import MonadUtils
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import Data.ByteString ( unpack )
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import Control.Monad
import Data.List
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-----------------------------------------------------------------------------
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dsBracket :: HsBracket Name -> [PendingTcSplice] -> DsM CoreExpr
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-- Returns a CoreExpr of type TH.ExpQ
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-- The quoted thing is parameterised over Name, even though it has
-- been type checked.  We don't want all those type decorations!

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dsBracket brack splices
  = dsExtendMetaEnv new_bit (do_brack brack)
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  where
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    new_bit = mkNameEnv [(n, DsSplice (unLoc e)) | PendingTcSplice n e <- splices]
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    do_brack (VarBr _ n) = do { MkC e1  <- lookupOcc n ; return e1 }
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    do_brack (ExpBr e)   = do { MkC e1  <- repLE e     ; return e1 }
    do_brack (PatBr p)   = do { MkC p1  <- repTopP p   ; return p1 }
    do_brack (TypBr t)   = do { MkC t1  <- repLTy t    ; return t1 }
    do_brack (DecBrG gp) = do { MkC ds1 <- repTopDs gp ; return ds1 }
    do_brack (DecBrL _)  = panic "dsBracket: unexpected DecBrL"
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    do_brack (TExpBr e)  = do { MkC e1  <- repLE e     ; return e1 }
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{- -------------- 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))
-}


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

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repTopP :: LPat Name -> DsM (Core TH.PatQ)
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repTopP pat = do { ss <- mkGenSyms (collectPatBinders pat)
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                 ; pat' <- addBinds ss (repLP pat)
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                 ; wrapGenSyms ss pat' }
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repTopDs :: HsGroup Name -> DsM (Core (TH.Q [TH.Dec]))
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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_vects   = vects
                        , hs_docs    = docs })
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 = do { let { bndrs  = hsSigTvBinders valds
                       ++ hsGroupBinders group
                       ++ hsPatSynSelectors valds
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            ; instds = tyclds >>= group_instds } ;
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        ss <- mkGenSyms bndrs ;
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        -- 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
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        decls <- addBinds ss (
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                  do { val_ds   <- rep_val_binds valds
                     ; _        <- mapM no_splice splcds
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                     ; tycl_ds  <- mapM repTyClD (tyClGroupTyClDecls tyclds)
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                     ; role_ds  <- mapM repRoleD (concatMap group_roles tyclds)
                     ; inst_ds  <- mapM repInstD instds
                     ; deriv_ds <- mapM repStandaloneDerivD derivds
                     ; fix_ds   <- mapM repFixD fixds
                     ; _        <- mapM no_default_decl defds
                     ; for_ds   <- mapM repForD fords
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                     ; _        <- mapM no_warn (concatMap (wd_warnings . unLoc)
                                                           warnds)
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                     ; ann_ds   <- mapM repAnnD annds
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                     ; rule_ds  <- mapM repRuleD (concatMap (rds_rules . unLoc)
                                                            ruleds)
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                     ; _        <- mapM no_vect vects
                     ; _        <- mapM no_doc docs
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                        -- more needed
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                     ;  return (de_loc $ sort_by_loc $
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                                val_ds ++ catMaybes tycl_ds ++ role_ds
                                       ++ (concat fix_ds)
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                                       ++ inst_ds ++ rule_ds ++ for_ds
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                                       ++ ann_ds ++ deriv_ds) }) ;
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        decl_ty <- lookupType decQTyConName ;
        let { core_list = coreList' decl_ty decls } ;
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        dec_ty <- lookupType decTyConName ;
        q_decs  <- repSequenceQ dec_ty core_list ;
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        wrapGenSyms ss q_decs
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      }
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  where
    no_splice (L loc _)
      = notHandledL loc "Splices within declaration brackets" empty
    no_default_decl (L loc decl)
      = notHandledL loc "Default declarations" (ppr decl)
    no_warn (L loc (Warning thing _))
      = notHandledL loc "WARNING and DEPRECATION pragmas" $
                    text "Pragma for declaration of" <+> ppr thing
    no_vect (L loc decl)
      = notHandledL loc "Vectorisation pragmas" (ppr decl)
    no_doc (L loc _)
      = notHandledL loc "Haddock documentation" empty
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hsSigTvBinders :: HsValBinds Name -> [Name]
-- See Note [Scoped type variables in bindings]
hsSigTvBinders binds
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  = concatMap get_scoped_tvs sigs
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  where
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    get_scoped_tvs :: LSig Name -> [Name]
    -- Both implicit and explicit quantified variables
    -- We need the implicit ones for   f :: forall (a::k). blah
    --    here 'k' scopes too
    get_scoped_tvs (L _ (TypeSig _ sig))
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       | HsIB { hsib_vars = implicit_vars
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              , hsib_body = hs_ty } <- hswc_body sig
       , (explicit_vars, _) <- splitLHsForAllTy hs_ty
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       = implicit_vars ++ map hsLTyVarName explicit_vars
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    get_scoped_tvs _ = []

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    sigs = case binds of
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             ValBindsIn  _ sigs -> sigs
             ValBindsOut _ sigs -> sigs
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{- Notes

Note [Scoped type variables in bindings]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Consider
   f :: forall a. a -> a
   f x = x::a
Here the 'forall a' brings 'a' into scope over the binding group.
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To achieve this we
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  a) Gensym a binding for 'a' at the same time as we do one for 'f'
     collecting the relevant binders with hsSigTvBinders

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

The relevant places are signposted with references to this Note

Note [Binders and occurrences]
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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When we desugar [d| data T = MkT |]
we want to get
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        Data "T" [] [Con "MkT" []] []
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and *not*
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        Data "Foo:T" [] [Con "Foo:MkT" []] []
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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:
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        Data "T79" ....
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But if we see this:
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        data T = MkT
        foo = reifyDecl T
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then we must desugar to
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        foo = Data "Foo:T" [] [Con "Foo:MkT" []] []
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So in repTopDs we bring the binders into scope with mkGenSyms and addBinds.
And we use lookupOcc, rather than lookupBinder
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in repTyClD and repC.

-}

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-- represent associated family instances
--
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repTyClD :: LTyClDecl Name -> DsM (Maybe (SrcSpan, Core TH.DecQ))
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repTyClD (L loc (FamDecl { tcdFam = fam })) = liftM Just $ repFamilyDecl (L loc fam)

repTyClD (L loc (SynDecl { tcdLName = tc, tcdTyVars = tvs, tcdRhs = rhs }))
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  = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
       ; dec <- addTyClTyVarBinds tvs $ \bndrs ->
                repSynDecl tc1 bndrs rhs
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       ; return (Just (loc, dec)) }
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repTyClD (L loc (DataDecl { tcdLName = tc, tcdTyVars = tvs, tcdDataDefn = defn }))
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  = do { tc1 <- lookupLOcc tc           -- See note [Binders and occurrences]
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       ; dec <- addTyClTyVarBinds tvs $ \bndrs ->
                repDataDefn tc1 bndrs Nothing defn
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       ; return (Just (loc, dec)) }
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repTyClD (L loc (ClassDecl { tcdCtxt = cxt, tcdLName = cls,
                             tcdTyVars = tvs, tcdFDs = fds,
                             tcdSigs = sigs, tcdMeths = meth_binds,
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                             tcdATs = ats, tcdATDefs = atds }))
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  = do { cls1 <- lookupLOcc cls         -- See note [Binders and occurrences]
       ; dec  <- addTyVarBinds tvs $ \bndrs ->
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           do { cxt1   <- repLContext cxt
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              ; sigs1  <- rep_sigs sigs
              ; binds1 <- rep_binds meth_binds
              ; fds1   <- repLFunDeps fds
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              ; ats1   <- repFamilyDecls ats
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              ; atds1  <- repAssocTyFamDefaults atds
              ; decls1 <- coreList decQTyConName (ats1 ++ atds1 ++ sigs1 ++ binds1)
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              ; repClass cxt1 cls1 bndrs fds1 decls1
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              }
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       ; return $ Just (loc, dec)
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       }
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-------------------------
repRoleD :: LRoleAnnotDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repRoleD (L loc (RoleAnnotDecl tycon roles))
  = do { tycon1 <- lookupLOcc tycon
       ; roles1 <- mapM repRole roles
       ; roles2 <- coreList roleTyConName roles1
       ; dec <- repRoleAnnotD tycon1 roles2
       ; return (loc, dec) }

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-------------------------
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repDataDefn :: Core TH.Name -> Core [TH.TyVarBndr]
            -> Maybe (Core [TH.TypeQ])
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            -> HsDataDefn Name
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            -> DsM (Core TH.DecQ)
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repDataDefn tc bndrs opt_tys
          (HsDataDefn { dd_ND = new_or_data, dd_ctxt = cxt, dd_kindSig = ksig
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                      , dd_cons = cons, dd_derivs = mb_derivs })
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  = do { cxt1     <- repLContext cxt
       ; derivs1  <- repDerivs mb_derivs
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       ; case (new_or_data, cons) of
           (NewType, [con])  -> do { con'  <- repC con
                                   ; ksig' <- repMaybeLKind ksig
                                   ; repNewtype cxt1 tc bndrs opt_tys ksig' con'
                                                derivs1 }
           (NewType, _) -> failWithDs (text "Multiple constructors for newtype:"
                                       <+> pprQuotedList
                                       (getConNames $ unLoc $ head cons))
           (DataType, _) -> do { ksig' <- repMaybeLKind ksig
                               ; consL <- mapM repC cons
                               ; cons1 <- coreList conQTyConName consL
                               ; repData cxt1 tc bndrs opt_tys ksig' cons1
                                         derivs1 }
       }
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repSynDecl :: Core TH.Name -> Core [TH.TyVarBndr]
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           -> LHsType Name
           -> DsM (Core TH.DecQ)
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repSynDecl tc bndrs ty
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  = do { ty1 <- repLTy ty
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       ; repTySyn tc bndrs ty1 }

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

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

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

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

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repFamilyDecls :: [LFamilyDecl Name] -> DsM [Core TH.DecQ]
repFamilyDecls fds = liftM de_loc (mapM repFamilyDecl fds)
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repAssocTyFamDefaults :: [LTyFamDefltEqn Name] -> DsM [Core TH.DecQ]
repAssocTyFamDefaults = mapM rep_deflt
  where
     -- very like repTyFamEqn, but different in the details
    rep_deflt :: LTyFamDefltEqn Name -> DsM (Core TH.DecQ)
    rep_deflt (L _ (TyFamEqn { tfe_tycon = tc
                             , tfe_pats  = bndrs
                             , tfe_rhs   = rhs }))
      = addTyClTyVarBinds bndrs $ \ _ ->
        do { tc1  <- lookupLOcc tc
           ; tys1 <- repLTys (hsLTyVarBndrsToTypes bndrs)
           ; tys2 <- coreList typeQTyConName tys1
           ; rhs1 <- repLTy rhs
           ; eqn1 <- repTySynEqn tys2 rhs1
           ; repTySynInst tc1 eqn1 }

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-------------------------
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-- represent fundeps
--
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repLFunDeps :: [Located (FunDep (Located Name))] -> DsM (Core [TH.FunDep])
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repLFunDeps fds = repList funDepTyConName repLFunDep fds
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repLFunDep :: Located (FunDep (Located Name)) -> DsM (Core TH.FunDep)
repLFunDep (L _ (xs, ys))
   = do xs' <- repList nameTyConName (lookupBinder . unLoc) xs
        ys' <- repList nameTyConName (lookupBinder . unLoc) ys
        repFunDep xs' ys'
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-- Represent instance declarations
--
repInstD :: LInstDecl Name -> DsM (SrcSpan, Core TH.DecQ)
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repInstD (L loc (TyFamInstD { tfid_inst = fi_decl }))
  = do { dec <- repTyFamInstD fi_decl
       ; return (loc, dec) }
repInstD (L loc (DataFamInstD { dfid_inst = fi_decl }))
  = do { dec <- repDataFamInstD fi_decl
       ; return (loc, dec) }
repInstD (L loc (ClsInstD { cid_inst = cls_decl }))
  = do { dec <- repClsInstD cls_decl
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       ; return (loc, dec) }
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repClsInstD :: ClsInstDecl Name -> DsM (Core TH.DecQ)
repClsInstD (ClsInstDecl { cid_poly_ty = ty, cid_binds = binds
                         , cid_sigs = prags, cid_tyfam_insts = ats
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                         , cid_datafam_insts = adts
                         , cid_overlap_mode = overlap
                         })
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  = addSimpleTyVarBinds tvs $
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            -- We must bring the type variables into scope, so their
            -- occurrences don't fail, even though the binders don't
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            -- appear in the resulting data structure
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            --
            -- But we do NOT bring the binders of 'binds' into scope
            -- because they are properly regarded as occurrences
            -- For example, the method names should be bound to
            -- the selector Ids, not to fresh names (Trac #5410)
            --
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            do { cxt1 <- repLContext cxt
               ; inst_ty1 <- repLTy inst_ty
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               ; binds1 <- rep_binds binds
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               ; prags1 <- rep_sigs prags
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               ; ats1 <- mapM (repTyFamInstD . unLoc) ats
               ; adts1 <- mapM (repDataFamInstD . unLoc) adts
               ; decls <- coreList decQTyConName (ats1 ++ adts1 ++ binds1 ++ prags1)
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               ; rOver <- repOverlap (fmap unLoc overlap)
               ; repInst rOver cxt1 inst_ty1 decls }
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 where
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   (tvs, cxt, inst_ty) = splitLHsInstDeclTy ty
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repStandaloneDerivD :: LDerivDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repStandaloneDerivD (L loc (DerivDecl { deriv_type = ty }))
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  = do { dec <- addSimpleTyVarBinds tvs $
                do { cxt'     <- repLContext cxt
                   ; inst_ty' <- repLTy inst_ty
                   ; repDeriv cxt' inst_ty' }
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       ; return (loc, dec) }
  where
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    (tvs, cxt, inst_ty) = splitLHsInstDeclTy ty
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repTyFamInstD :: TyFamInstDecl Name -> DsM (Core TH.DecQ)
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repTyFamInstD decl@(TyFamInstDecl { tfid_eqn = eqn })
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  = do { let tc_name = tyFamInstDeclLName decl
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       ; tc <- lookupLOcc tc_name               -- See note [Binders and occurrences]
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       ; eqn1 <- repTyFamEqn eqn
       ; repTySynInst tc eqn1 }
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repTyFamEqn :: LTyFamInstEqn Name -> DsM (Core TH.TySynEqnQ)
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repTyFamEqn (L _ (TyFamEqn { tfe_pats = HsIB { hsib_body = tys
                                             , hsib_vars = var_names }
                           , tfe_rhs = rhs }))
  = do { let hs_tvs = HsQTvs { hsq_implicit = var_names
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                             , hsq_explicit = []
                             , hsq_dependent = emptyNameSet }   -- Yuk
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       ; addTyClTyVarBinds hs_tvs $ \ _ ->
         do { tys1 <- repLTys tys
            ; tys2 <- coreList typeQTyConName tys1
            ; rhs1 <- repLTy rhs
            ; repTySynEqn tys2 rhs1 } }

repDataFamInstD :: DataFamInstDecl Name -> DsM (Core TH.DecQ)
repDataFamInstD (DataFamInstDecl { dfid_tycon = tc_name
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                                 , dfid_pats = HsIB { hsib_body = tys, hsib_vars = var_names }
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                                 , dfid_defn = defn })
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  = do { tc <- lookupLOcc tc_name               -- See note [Binders and occurrences]
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       ; let hs_tvs = HsQTvs { hsq_implicit = var_names
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                             , hsq_explicit = []
                             , hsq_dependent = emptyNameSet }   -- Yuk
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       ; addTyClTyVarBinds hs_tvs $ \ bndrs ->
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         do { tys1 <- repList typeQTyConName repLTy tys
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            ; repDataDefn tc bndrs (Just tys1) defn } }
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repForD :: Located (ForeignDecl Name) -> DsM (SrcSpan, Core TH.DecQ)
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repForD (L loc (ForeignImport { fd_name = name, fd_sig_ty = typ
                              , fd_fi = CImport (L _ cc) (L _ s) mch cis _ }))
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 = do MkC name' <- lookupLOcc name
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      MkC typ' <- repHsSigType typ
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      MkC cc' <- repCCallConv cc
      MkC s' <- repSafety s
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      cis' <- conv_cimportspec cis
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      MkC str <- coreStringLit (static ++ chStr ++ cis')
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      dec <- rep2 forImpDName [cc', s', str, name', typ']
      return (loc, dec)
 where
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    conv_cimportspec (CLabel cls) = notHandled "Foreign label" (doubleQuotes (ppr cls))
    conv_cimportspec (CFunction DynamicTarget) = return "dynamic"
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    conv_cimportspec (CFunction (StaticTarget _ fs _ True))
                            = return (unpackFS fs)
    conv_cimportspec (CFunction (StaticTarget _ _  _ False))
                            = panic "conv_cimportspec: values not supported yet"
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    conv_cimportspec CWrapper = return "wrapper"
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    -- these calling conventions do not support headers and the static keyword
    raw_cconv = cc == PrimCallConv || cc == JavaScriptCallConv
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    static = case cis of
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                 CFunction (StaticTarget _ _ _ _) | not raw_cconv -> "static "
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                 _ -> ""
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    chStr = case mch of
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            Just (Header _ h) | not raw_cconv -> unpackFS h ++ " "
            _ -> ""
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repForD decl = notHandled "Foreign declaration" (ppr decl)
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repCCallConv :: CCallConv -> DsM (Core TH.Callconv)
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repCCallConv CCallConv          = rep2 cCallName []
repCCallConv StdCallConv        = rep2 stdCallName []
repCCallConv CApiConv           = rep2 cApiCallName []
repCCallConv PrimCallConv       = rep2 primCallName []
repCCallConv JavaScriptCallConv = rep2 javaScriptCallName []
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repSafety :: Safety -> DsM (Core TH.Safety)
repSafety PlayRisky = rep2 unsafeName []
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repSafety PlayInterruptible = rep2 interruptibleName []
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repSafety PlaySafe = rep2 safeName []
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repFixD :: LFixitySig Name -> DsM [(SrcSpan, Core TH.DecQ)]
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repFixD (L loc (FixitySig names (Fixity _ prec dir)))
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  = do { MkC prec' <- coreIntLit prec
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       ; let rep_fn = case dir of
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                        InfixL -> infixLDName
                        InfixR -> infixRDName
                        InfixN -> infixNDName
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       ; let do_one name
              = do { MkC name' <- lookupLOcc name
                   ; dec <- rep2 rep_fn [prec', name']
                   ; return (loc,dec) }
       ; mapM do_one names }
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repRuleD :: LRuleDecl Name -> DsM (SrcSpan, Core TH.DecQ)
repRuleD (L loc (HsRule n act bndrs lhs _ rhs _))
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  = do { let bndr_names = concatMap ruleBndrNames bndrs
       ; ss <- mkGenSyms bndr_names
       ; rule1 <- addBinds ss $
                  do { bndrs' <- repList ruleBndrQTyConName repRuleBndr bndrs
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                     ; n'   <- coreStringLit $ unpackFS $ snd $ unLoc n
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                     ; act' <- repPhases act
                     ; lhs' <- repLE lhs
                     ; rhs' <- repLE rhs
                     ; repPragRule n' bndrs' lhs' rhs' act' }
       ; rule2 <- wrapGenSyms ss rule1
       ; return (loc, rule2) }

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ruleBndrNames :: LRuleBndr Name -> [Name]
ruleBndrNames (L _ (RuleBndr n))      = [unLoc n]
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ruleBndrNames (L _ (RuleBndrSig n sig))
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  | HsWC { hswc_body = HsIB { hsib_vars = vars }} <- sig
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  = unLoc n : vars
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repRuleBndr :: LRuleBndr Name -> DsM (Core TH.RuleBndrQ)
repRuleBndr (L _ (RuleBndr n))
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  = do { MkC n' <- lookupLBinder n
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       ; rep2 ruleVarName [n'] }
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repRuleBndr (L _ (RuleBndrSig n sig))
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  = do { MkC n'  <- lookupLBinder n
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       ; MkC ty' <- repLTy (hsSigWcType sig)
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       ; rep2 typedRuleVarName [n', ty'] }

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

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

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

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repC :: LConDecl Name -> DsM (Core TH.ConQ)
repC (L _ (ConDeclH98 { con_name = con
                      , con_qvars = Nothing, con_cxt = Nothing
                      , con_details = details }))
  = repDataCon con details

repC (L _ (ConDeclH98 { con_name = con
                      , con_qvars = mcon_tvs, con_cxt = mcxt
                      , con_details = details }))
  = do { let con_tvs = fromMaybe emptyLHsQTvs mcon_tvs
             ctxt    = unLoc $ fromMaybe (noLoc []) mcxt
       ; addTyVarBinds con_tvs $ \ ex_bndrs ->
         do { c'    <- repDataCon con details
            ; ctxt' <- repContext ctxt
            ; if isEmptyLHsQTvs con_tvs && null ctxt
              then return c'
              else rep2 forallCName ([unC ex_bndrs, unC ctxt', unC c'])
            }
       }
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repC (L _ (ConDeclGADT { con_names = cons
                       , con_type = res_ty@(HsIB { hsib_vars = con_vars })}))
  | (details, res_ty', L _ [] , []) <- gadtDetails
  , [] <- con_vars
    -- no implicit or explicit variables, no context = no need for a forall
  = do { let doc = text "In the constructor for " <+> ppr (head cons)
       ; (hs_details, gadt_res_ty) <-
           updateGadtResult failWithDs doc details res_ty'
       ; repGadtDataCons cons hs_details gadt_res_ty }

  | (details,res_ty',ctxt, tvs) <- gadtDetails
  = do { let doc = text "In the constructor for " <+> ppr (head cons)
             con_tvs = HsQTvs { hsq_implicit = []
                              , hsq_explicit = (map (noLoc . UserTyVar . noLoc)
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                                                   con_vars) ++ tvs
                              , hsq_dependent = emptyNameSet }
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       ; addTyVarBinds con_tvs $ \ ex_bndrs -> do
       { (hs_details, gadt_res_ty) <-
           updateGadtResult failWithDs doc details res_ty'
       ; c'    <- repGadtDataCons cons hs_details gadt_res_ty
       ; ctxt' <- repContext (unLoc ctxt)
       ; rep2 forallCName ([unC ex_bndrs, unC ctxt', unC c']) } }
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  where
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     gadtDetails = gadtDeclDetails res_ty
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repSrcUnpackedness :: SrcUnpackedness -> DsM (Core TH.SourceUnpackednessQ)
repSrcUnpackedness SrcUnpack   = rep2 sourceUnpackName         []
repSrcUnpackedness SrcNoUnpack = rep2 sourceNoUnpackName       []
repSrcUnpackedness NoSrcUnpack = rep2 noSourceUnpackednessName []

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

repBangTy :: LBangType Name -> DsM (Core (TH.BangTypeQ))
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repBangTy ty = do
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  MkC u <- repSrcUnpackedness su'
  MkC s <- repSrcStrictness ss'
  MkC b <- rep2 bangName [u, s]
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  MkC t <- repLTy ty'
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  rep2 bangTypeName [b, t]
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  where
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    (su', ss', ty') = case ty of
            L _ (HsBangTy (HsSrcBang _ su ss) ty) -> (su, ss, ty)
            _ -> (NoSrcUnpack, NoSrcStrict, ty)
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-------------------------------------------------------
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--                      Deriving clause
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-------------------------------------------------------

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repDerivs :: HsDeriving Name -> DsM (Core TH.CxtQ)
repDerivs deriv = do
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    let clauses = case deriv of
                    Nothing         -> []
                    Just (L _ ctxt) -> ctxt
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    tys <- repList typeQTyConName
                   (rep_deriv . hsSigType)
                   clauses
           :: DsM (Core [TH.PredQ])
    repCtxt tys
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  where
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    rep_deriv :: LHsType Name -> DsM (Core TH.TypeQ)
    rep_deriv (L _ ty) = repTy ty
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-------------------------------------------------------
--   Signatures in a class decl, or a group of bindings
-------------------------------------------------------

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

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rep_sigs' :: [LSig Name] -> DsM [(SrcSpan, Core TH.DecQ)]
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        -- We silently ignore ones we don't recognise
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rep_sigs' = concatMapM rep_sig
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rep_sig :: LSig Name -> DsM [(SrcSpan, Core TH.DecQ)]
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rep_sig (L loc (TypeSig nms ty))      = mapM (rep_wc_ty_sig sigDName loc ty) nms
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rep_sig (L loc (PatSynSig nms ty))    = mapM (rep_patsyn_ty_sig loc ty) nms
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rep_sig (L loc (ClassOpSig is_deflt nms ty))
  | is_deflt                          = mapM (rep_ty_sig defaultSigDName loc ty) nms
  | otherwise                         = mapM (rep_ty_sig sigDName loc ty) nms
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rep_sig d@(L _ (IdSig {}))            = pprPanic "rep_sig IdSig" (ppr d)
rep_sig (L _   (FixSig {}))           = return [] -- fixity sigs at top level
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rep_sig (L loc (InlineSig nm ispec))  = rep_inline nm ispec loc
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rep_sig (L loc (SpecSig nm tys ispec))
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  = concatMapM (\t -> rep_specialise nm t ispec loc) tys
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rep_sig (L loc (SpecInstSig _ ty))    = rep_specialiseInst ty loc
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rep_sig (L _   (MinimalSig {}))       = notHandled "MINIMAL pragmas" empty
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rep_sig (L _   (SCCFunSig {}))        = notHandled "SCC pragmas" empty
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rep_ty_sig :: Name -> SrcSpan -> LHsSigType Name -> Located Name
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           -> DsM (SrcSpan, Core TH.DecQ)
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rep_ty_sig mk_sig loc sig_ty nm
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  = do { nm1 <- lookupLOcc nm
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       ; ty1 <- repHsSigType sig_ty
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       ; sig <- repProto mk_sig nm1 ty1
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       ; return (loc, sig) }
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rep_patsyn_ty_sig :: SrcSpan -> LHsSigType Name -> Located Name
                  -> DsM (SrcSpan, Core TH.DecQ)
-- represents a pattern synonym type signature; see NOTE [Pattern
-- synonym signatures and Template Haskell]
rep_patsyn_ty_sig loc sig_ty nm
  = do { nm1 <- lookupLOcc nm
       ; ty1 <- repHsPatSynSigType sig_ty
       ; sig <- repProto patSynSigDName nm1 ty1
       ; return (loc, sig) }

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rep_wc_ty_sig :: Name -> SrcSpan -> LHsSigWcType Name -> Located Name
              -> DsM (SrcSpan, Core TH.DecQ)
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    -- We must special-case the top-level explicit for-all of a TypeSig
    -- See Note [Scoped type variables in bindings]
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rep_wc_ty_sig mk_sig loc sig_ty nm
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  , (explicit_tvs, ctxt, ty) <- splitLHsSigmaTy hs_ty
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  = do { nm1 <- lookupLOcc nm
       ; let rep_in_scope_tv tv = do { name <- lookupBinder (hsLTyVarName tv)
                                     ; repTyVarBndrWithKind tv name }
             all_tvs = map (noLoc . UserTyVar . noLoc) implicit_tvs ++ explicit_tvs
       ; th_tvs  <- repList tyVarBndrTyConName rep_in_scope_tv all_tvs
       ; th_ctxt <- repLContext ctxt
       ; th_ty   <- repLTy ty
       ; ty1 <- if null all_tvs && null (unLoc ctxt)
                then return th_ty
                else repTForall th_tvs th_ctxt th_ty
       ; sig <- repProto mk_sig nm1 ty1
       ; return (loc, sig) }
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rep_inline :: Located Name
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           -> InlinePragma      -- Never defaultInlinePragma
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           -> SrcSpan
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           -> DsM [(SrcSpan, Core TH.DecQ)]
rep_inline nm ispec loc
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  = 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
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       ; return [(loc, pragma)]
       }

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

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

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repRuleMatch :: RuleMatchInfo -> DsM (Core TH.RuleMatch)
repRuleMatch ConLike = dataCon conLikeDataConName
repRuleMatch FunLike = dataCon funLikeDataConName
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repPhases :: Activation -> DsM (Core TH.Phases)
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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
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-------------------------------------------------------
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--                      Types
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-------------------------------------------------------
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addSimpleTyVarBinds :: [Name]                -- the binders to be added
                    -> DsM (Core (TH.Q a))   -- action in the ext env
                    -> DsM (Core (TH.Q a))
addSimpleTyVarBinds names thing_inside
  = do { fresh_names <- mkGenSyms names
       ; term <- addBinds fresh_names thing_inside
       ; wrapGenSyms fresh_names term }

addTyVarBinds :: LHsQTyVars Name                            -- the binders to be added
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              -> (Core [TH.TyVarBndr] -> DsM (Core (TH.Q a)))  -- action in the ext env
              -> DsM (Core (TH.Q a))
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-- 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
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-- meta environment and gets the *new* names on Core-level as an argument
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addTyVarBinds (HsQTvs { hsq_implicit = imp_tvs, hsq_explicit = exp_tvs }) m
  = do { fresh_imp_names <- mkGenSyms imp_tvs
       ; fresh_exp_names <- mkGenSyms (map hsLTyVarName exp_tvs)
       ; let fresh_names = fresh_imp_names ++ fresh_exp_names
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                 do { kbs <- repList tyVarBndrTyConName mk_tv_bndr
                                     (exp_tvs `zip` fresh_exp_names)
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                    ; m kbs }
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       ; wrapGenSyms fresh_names term }
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  where
    mk_tv_bndr (tv, (_,v)) = repTyVarBndrWithKind tv (coreVar v)
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addTyClTyVarBinds :: LHsQTyVars Name
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                  -> (Core [TH.TyVarBndr] -> DsM (Core (TH.Q a)))
                  -> DsM (Core (TH.Q a))
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-- 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
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  = do { let tv_names = hsAllLTyVarNames tvs
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       ; env <- dsGetMetaEnv
       ; freshNames <- mkGenSyms (filterOut (`elemNameEnv` env) tv_names)
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            -- Make fresh names for the ones that are not already in scope
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            -- This makes things work for family declarations

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       ; term <- addBinds freshNames $
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                 do { kbs <- repList tyVarBndrTyConName mk_tv_bndr (hsQTvExplicit tvs)
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                    ; m kbs }
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       ; wrapGenSyms freshNames term }
  where
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    mk_tv_bndr tv = do { v <- lookupBinder (hsLTyVarName tv)
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                       ; repTyVarBndrWithKind tv v }
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-- Produce kinded binder constructors from the Haskell tyvar binders
--
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repTyVarBndrWithKind :: LHsTyVarBndr Name
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                     -> Core TH.Name -> DsM (Core TH.TyVarBndr)
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repTyVarBndrWithKind (L _ (UserTyVar _)) nm
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  = repPlainTV nm
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repTyVarBndrWithKind (L _ (KindedTyVar _ ki)) nm
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  = repLKind ki >>= repKindedTV nm
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-- | Represent a type variable binder
repTyVarBndr :: LHsTyVarBndr Name -> DsM (Core TH.TyVarBndr)
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repTyVarBndr (L _ (UserTyVar (L _ nm)) )= do { nm' <- lookupBinder nm
                                             ; repPlainTV nm' }
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repTyVarBndr (L _ (KindedTyVar (L _ nm) ki)) = do { nm' <- lookupBinder nm
                                                  ; ki' <- repLKind ki
                                                  ; repKindedTV nm' ki' }

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

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repContext :: HsContext Name -> DsM (Core TH.CxtQ)
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repContext ctxt = do preds <- repList typeQTyConName repLTy ctxt
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                     repCtxt preds
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repHsSigType :: LHsSigType Name -> DsM (Core TH.TypeQ)
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repHsSigType (HsIB { hsib_vars = vars
                   , hsib_body = body })
  | (explicit_tvs, ctxt, ty) <- splitLHsSigmaTy body
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  = addTyVarBinds (HsQTvs { hsq_implicit = []
                          , hsq_explicit = map (noLoc . UserTyVar . noLoc) vars ++
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                                           explicit_tvs
                          , hsq_dependent = emptyNameSet })
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                  $ \ th_tvs ->
    do { th_ctxt <- repLContext ctxt
       ; th_ty   <- repLTy ty
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       ; if null vars && null explicit_tvs && null (unLoc ctxt)
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         then return th_ty
         else repTForall th_tvs th_ctxt th_ty }

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repHsPatSynSigType :: LHsSigType Name -> DsM (Core TH.TypeQ)
repHsPatSynSigType (HsIB { hsib_vars = implicit_tvs
                         , hsib_body = body })
  = addTyVarBinds (newTvs (impls ++ univs)) $ \th_univs ->
      addTyVarBinds (newTvs exis) $ \th_exis ->
    do { th_reqs  <- repLContext reqs
       ; th_provs <- repLContext provs
       ; th_ty    <- repLTy ty
       ; repTForall th_univs th_reqs =<< (repTForall th_exis th_provs th_ty) }
  where
    impls = map (noLoc . UserTyVar . noLoc) implicit_tvs
    newTvs tvs = HsQTvs
      { hsq_implicit  = []
      , hsq_explicit  = tvs
      , hsq_dependent = emptyNameSet }
    (univs, reqs, exis, provs, ty) = splitLHsPatSynTy body

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repHsSigWcType :: LHsSigWcType Name -> DsM (Core TH.TypeQ)
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repHsSigWcType (HsWC { hswc_body = sig1 })
  = repHsSigType sig1
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-- yield the representation of a list of types
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repLTys :: [LHsType Name] -> DsM [Core TH.TypeQ]
repLTys tys = mapM repLTy tys
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-- represent a type
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repLTy :: LHsType Name -> DsM (Core TH.TypeQ)
repLTy (L _ ty) = repTy ty

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repForall :: HsType Name -> DsM (Core TH.TypeQ)
-- Arg of repForall is always HsForAllTy or HsQualTy
repForall ty
 | (tvs, ctxt, tau) <- splitLHsSigmaTy (noLoc ty)
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 = addTyVarBinds (HsQTvs { hsq_implicit = [], hsq_explicit = tvs
                         , hsq_dependent = emptyNameSet }) $ \bndrs ->
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   do { ctxt1  <- repLContext ctxt
      ; ty1    <- repLTy tau
      ; repTForall bndrs ctxt1 ty1 }
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repTy :: HsType Name -> DsM (Core TH.TypeQ)
repTy ty@(HsForAllTy {}) = repForall ty
repTy ty@(HsQualTy {})   = repForall ty
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repTy (HsTyVar (L _ n))
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  | isTvOcc occ   = do tv1 <- lookupOcc n
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                       repTvar tv1
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  | isDataOcc occ = do tc1 <- lookupOcc n
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                       repPromotedDataCon tc1
  | n == eqTyConName = repTequality
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  | otherwise     = do tc1 <- lookupOcc n
                       repNamedTyCon tc1
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  where
    occ = nameOccName n
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repTy (HsAppTy f a)         = do
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                                f1 <- repLTy f
                                a1 <- repLTy a
                                repTapp f1 a1
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repTy (HsFunTy f a)         = do
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