rename/RnSource.hs

    {-
    (c) The GRASP/AQUA Project, Glasgow University, 1992-1998

    \section[RnSource]{Main pass of renamer}
    -}

    {-# LANGUAGE CPP, ScopedTypeVariables #-}
    {-# LANGUAGE FlexibleContexts #-}
    {-# LANGUAGE TypeFamilies #-}

    module RnSource (
            rnSrcDecls, addTcgDUs, findSplice
        ) where

    #include "HsVersions.h"

    import GhcPrelude

    import {-# SOURCE #-} RnExpr( rnLExpr )
    import {-# SOURCE #-} RnSplice ( rnSpliceDecl, rnTopSpliceDecls )

    import HsSyn
    import FieldLabel
    import RdrName
    import RnTypes
    import RnBinds
    import RnEnv
    import RnUtils          ( HsDocContext(..), mapFvRn, bindLocalNames
                            , checkDupRdrNames, inHsDocContext, bindLocalNamesFV
                            , checkShadowedRdrNames, warnUnusedTypePatterns
                            , extendTyVarEnvFVRn, newLocalBndrsRn )
    import RnUnbound        ( mkUnboundName )
    import RnNames
    import RnHsDoc          ( rnHsDoc, rnMbLHsDoc )
    import TcAnnotations    ( annCtxt )
    import TcRnMonad

    import ForeignCall      ( CCallTarget(..) )
    import Module
    import HscTypes         ( Warnings(..), plusWarns )
    import Class            ( FunDep )
    import PrelNames        ( applicativeClassName, pureAName, thenAName
                            , monadClassName, returnMName, thenMName
                            , monadFailClassName, failMName, failMName_preMFP
                            , semigroupClassName, sappendName
                            , monoidClassName, mappendName
                            )
    import Name
    import NameSet
    import NameEnv
    import Avail
    import Outputable
    import Bag
    import BasicTypes       ( DerivStrategy, RuleName, pprRuleName )
    import Maybes           ( orElse )
    import FastString
    import SrcLoc
    import DynFlags
    import Util             ( debugIsOn, filterOut, lengthExceeds, partitionWith )
    import HscTypes         ( HscEnv, hsc_dflags )
    import ListSetOps       ( findDupsEq, removeDups, equivClasses )
    import Digraph          ( SCC, flattenSCC, flattenSCCs, Node(..)
                            , stronglyConnCompFromEdgedVerticesUniq )
    import UniqSet
    import qualified GHC.LanguageExtensions as LangExt

    import Control.Monad
    import Control.Arrow ( first )
    import Data.List ( mapAccumL )
    import qualified Data.List.NonEmpty as NE
    import Data.List.NonEmpty ( NonEmpty(..) )
    import Data.Maybe ( isJust )
    import qualified Data.Set as Set ( difference, fromList, toList, null )

    {- | @rnSourceDecl@ "renames" declarations.
    It simultaneously performs dependency analysis and precedence parsing.
    It also does the following error checks:

    * Checks that tyvars are used properly. This includes checking
      for undefined tyvars, and tyvars in contexts that are ambiguous.
      (Some of this checking has now been moved to module @TcMonoType@,
      since we don't have functional dependency information at this point.)

    * Checks that all variable occurrences are defined.

    * Checks the @(..)@ etc constraints in the export list.

    Brings the binders of the group into scope in the appropriate places;
    does NOT assume that anything is in scope already
    -}
    rnSrcDecls :: HsGroup GhcPs -> RnM (TcGblEnv, HsGroup GhcRn)
    -- Rename a top-level HsGroup; used for normal source files *and* hs-boot files
    rnSrcDecls group@(HsGroup { hs_valds   = val_decls,
                                hs_splcds  = splice_decls,
                                hs_tyclds  = tycl_decls,
                                hs_derivds = deriv_decls,
                                hs_fixds   = fix_decls,
                                hs_warnds  = warn_decls,
                                hs_annds   = ann_decls,
                                hs_fords   = foreign_decls,
                                hs_defds   = default_decls,
                                hs_ruleds  = rule_decls,
                                hs_vects   = vect_decls,
                                hs_docs    = docs })
     = do {
       -- (A) Process the fixity declarations, creating a mapping from
       --     FastStrings to FixItems.
       --     Also checks for duplicates.
       local_fix_env <- makeMiniFixityEnv fix_decls ;

       -- (B) Bring top level binders (and their fixities) into scope,
       --     *except* for the value bindings, which get done in step (D)
       --     with collectHsIdBinders. However *do* include
       --
       --        * Class ops, data constructors, and record fields,
       --          because they do not have value declarations.
       --          Aso step (C) depends on datacons and record fields
       --
       --        * For hs-boot files, include the value signatures
       --          Again, they have no value declarations
       --
       (tc_envs, tc_bndrs) <- getLocalNonValBinders local_fix_env group ;

       setEnvs tc_envs $ do {

       failIfErrsM ; -- No point in continuing if (say) we have duplicate declarations

       -- (D1) Bring pattern synonyms into scope.
       --      Need to do this before (D2) because rnTopBindsLHS
       --      looks up those pattern synonyms (Trac #9889)

       extendPatSynEnv val_decls local_fix_env $ \pat_syn_bndrs -> do {

       -- (D2) Rename the left-hand sides of the value bindings.
       --     This depends on everything from (B) being in scope,
       --     and on (C) for resolving record wild cards.
       --     It uses the fixity env from (A) to bind fixities for view patterns.
       new_lhs <- rnTopBindsLHS local_fix_env val_decls ;

       -- Bind the LHSes (and their fixities) in the global rdr environment
       let { id_bndrs = collectHsIdBinders new_lhs } ;  -- Excludes pattern-synonym binders
                                                        -- They are already in scope
       traceRn "rnSrcDecls" (ppr id_bndrs) ;
       tc_envs <- extendGlobalRdrEnvRn (map avail id_bndrs) local_fix_env ;
       setEnvs tc_envs $ do {

       --  Now everything is in scope, as the remaining renaming assumes.

       -- (E) Rename type and class decls
       --     (note that value LHSes need to be in scope for default methods)
       --
       -- You might think that we could build proper def/use information
       -- for type and class declarations, but they can be involved
       -- in mutual recursion across modules, and we only do the SCC
       -- analysis for them in the type checker.
       -- So we content ourselves with gathering uses only; that
       -- means we'll only report a declaration as unused if it isn't
       -- mentioned at all.  Ah well.
       traceRn "Start rnTyClDecls" (ppr tycl_decls) ;
       (rn_tycl_decls, src_fvs1) <- rnTyClDecls tycl_decls ;

       -- (F) Rename Value declarations right-hand sides
       traceRn "Start rnmono" empty ;
       let { val_bndr_set = mkNameSet id_bndrs `unionNameSet` mkNameSet pat_syn_bndrs } ;
       is_boot <- tcIsHsBootOrSig ;
       (rn_val_decls, bind_dus) <- if is_boot
        -- For an hs-boot, use tc_bndrs (which collects how we're renamed
        -- signatures), since val_bndr_set is empty (there are no x = ...
        -- bindings in an hs-boot.)
        then rnTopBindsBoot tc_bndrs new_lhs
        else rnValBindsRHS (TopSigCtxt val_bndr_set) new_lhs ;
       traceRn "finish rnmono" (ppr rn_val_decls) ;

       -- (G) Rename Fixity and deprecations

       -- Rename fixity declarations and error if we try to
       -- fix something from another module (duplicates were checked in (A))
       let { all_bndrs = tc_bndrs `unionNameSet` val_bndr_set } ;
       rn_fix_decls <- mapM (mapM (rnSrcFixityDecl (TopSigCtxt all_bndrs)))
                            fix_decls ;

       -- Rename deprec decls;
       -- check for duplicates and ensure that deprecated things are defined locally
       -- at the moment, we don't keep these around past renaming
       rn_warns <- rnSrcWarnDecls all_bndrs warn_decls ;

       -- (H) Rename Everything else

       (rn_rule_decls,    src_fvs2) <- setXOptM LangExt.ScopedTypeVariables $
                                       rnList rnHsRuleDecls rule_decls ;
                               -- Inside RULES, scoped type variables are on
       (rn_vect_decls,    src_fvs3) <- rnList rnHsVectDecl    vect_decls ;
       (rn_foreign_decls, src_fvs4) <- rnList rnHsForeignDecl foreign_decls ;
       (rn_ann_decls,     src_fvs5) <- rnList rnAnnDecl       ann_decls ;
       (rn_default_decls, src_fvs6) <- rnList rnDefaultDecl   default_decls ;
       (rn_deriv_decls,   src_fvs7) <- rnList rnSrcDerivDecl  deriv_decls ;
       (rn_splice_decls,  src_fvs8) <- rnList rnSpliceDecl    splice_decls ;
          -- Haddock docs; no free vars
       rn_docs <- mapM (wrapLocM rnDocDecl) docs ;

       last_tcg_env <- getGblEnv ;
       -- (I) Compute the results and return
       let {rn_group = HsGroup { hs_valds   = rn_val_decls,
                                 hs_splcds  = rn_splice_decls,
                                 hs_tyclds  = rn_tycl_decls,
                                 hs_derivds = rn_deriv_decls,
                                 hs_fixds   = rn_fix_decls,
                                 hs_warnds  = [], -- warns are returned in the tcg_env
                                                 -- (see below) not in the HsGroup
                                 hs_fords  = rn_foreign_decls,
                                 hs_annds  = rn_ann_decls,
                                 hs_defds  = rn_default_decls,
                                 hs_ruleds = rn_rule_decls,
                                 hs_vects  = rn_vect_decls,
                                 hs_docs   = rn_docs } ;

            tcf_bndrs = hsTyClForeignBinders rn_tycl_decls rn_foreign_decls ;
            other_def  = (Just (mkNameSet tcf_bndrs), emptyNameSet) ;
            other_fvs  = plusFVs [src_fvs1, src_fvs2, src_fvs3, src_fvs4, src_fvs5,
                                  src_fvs6, src_fvs7, src_fvs8] ;
                    -- It is tiresome to gather the binders from type and class decls

            src_dus = [other_def] `plusDU` bind_dus `plusDU` usesOnly other_fvs ;
                    -- Instance decls may have occurrences of things bound in bind_dus
                    -- so we must put other_fvs last

            final_tcg_env = let tcg_env' = (last_tcg_env `addTcgDUs` src_dus)
                            in -- we return the deprecs in the env, not in the HsGroup above
                            tcg_env' { tcg_warns = tcg_warns tcg_env' `plusWarns` rn_warns };
           } ;
       traceRn "finish rnSrc" (ppr rn_group) ;
       traceRn "finish Dus" (ppr src_dus ) ;
       return (final_tcg_env, rn_group)
                        }}}}

    addTcgDUs :: TcGblEnv -> DefUses -> TcGblEnv
    -- This function could be defined lower down in the module hierarchy,
    -- but there doesn't seem anywhere very logical to put it.
    addTcgDUs tcg_env dus = tcg_env { tcg_dus = tcg_dus tcg_env `plusDU` dus }

    rnList :: (a -> RnM (b, FreeVars)) -> [Located a] -> RnM ([Located b], FreeVars)
    rnList f xs = mapFvRn (wrapLocFstM f) xs

    {-
    *********************************************************
    *                                                       *
            HsDoc stuff
    *                                                       *
    *********************************************************
    -}

    rnDocDecl :: DocDecl -> RnM DocDecl
    rnDocDecl (DocCommentNext doc) = do
      rn_doc <- rnHsDoc doc
      return (DocCommentNext rn_doc)
    rnDocDecl (DocCommentPrev doc) = do
      rn_doc <- rnHsDoc doc
      return (DocCommentPrev rn_doc)
    rnDocDecl (DocCommentNamed str doc) = do
      rn_doc <- rnHsDoc doc
      return (DocCommentNamed str rn_doc)
    rnDocDecl (DocGroup lev doc) = do
      rn_doc <- rnHsDoc doc
      return (DocGroup lev rn_doc)

    {-
    *********************************************************
    *                                                       *
            Source-code deprecations declarations
    *                                                       *
    *********************************************************

    Check that the deprecated names are defined, are defined locally, and
    that there are no duplicate deprecations.

    It's only imported deprecations, dealt with in RnIfaces, that we
    gather them together.
    -}

    -- checks that the deprecations are defined locally, and that there are no duplicates
    rnSrcWarnDecls :: NameSet -> [LWarnDecls GhcPs] -> RnM Warnings
    rnSrcWarnDecls _ []
      = return NoWarnings

    rnSrcWarnDecls bndr_set decls'
      = do { -- check for duplicates
           ; mapM_ (\ dups -> let (L loc rdr :| (lrdr':_)) = dups
                              in addErrAt loc (dupWarnDecl lrdr' rdr))
                   warn_rdr_dups
           ; pairs_s <- mapM (addLocM rn_deprec) decls
           ; return (WarnSome ((concat pairs_s))) }
     where
       decls = concatMap (\(L _ d) -> wd_warnings d) decls'

       sig_ctxt = TopSigCtxt bndr_set

       rn_deprec (Warning rdr_names txt)
           -- ensures that the names are defined locally
         = do { names <- concatMapM (lookupLocalTcNames sig_ctxt what . unLoc)
                                    rdr_names
              ; return [(rdrNameOcc rdr, txt) | (rdr, _) <- names] }

       what = text "deprecation"

       warn_rdr_dups = findDupRdrNames $ concatMap (\(L _ (Warning ns _)) -> ns)
                                                   decls

    findDupRdrNames :: [Located RdrName] -> [NonEmpty (Located RdrName)]
    findDupRdrNames = findDupsEq (\ x -> \ y -> rdrNameOcc (unLoc x) == rdrNameOcc (unLoc y))

    -- look for duplicates among the OccNames;
    -- we check that the names are defined above
    -- invt: the lists returned by findDupsEq always have at least two elements

    dupWarnDecl :: Located RdrName -> RdrName -> SDoc
    -- Located RdrName -> DeprecDecl RdrName -> SDoc
    dupWarnDecl (L loc _) rdr_name
      = vcat [text "Multiple warning declarations for" <+> quotes (ppr rdr_name),
              text "also at " <+> ppr loc]

    {-
    *********************************************************
    *                                                      *
    \subsection{Annotation declarations}
    *                                                      *
    *********************************************************
    -}

    rnAnnDecl :: AnnDecl GhcPs -> RnM (AnnDecl GhcRn, FreeVars)
    rnAnnDecl ann@(HsAnnotation s provenance expr)
      = addErrCtxt (annCtxt ann) $
        do { (provenance', provenance_fvs) <- rnAnnProvenance provenance
           ; (expr', expr_fvs) <- setStage (Splice Untyped) $
                                  rnLExpr expr
           ; return (HsAnnotation s provenance' expr',
                     provenance_fvs `plusFV` expr_fvs) }

    rnAnnProvenance :: AnnProvenance RdrName
                    -> RnM (AnnProvenance Name, FreeVars)
    rnAnnProvenance provenance = do
        provenance' <- traverse lookupTopBndrRn provenance
        return (provenance', maybe emptyFVs unitFV (annProvenanceName_maybe provenance'))

    {-
    *********************************************************
    *                                                      *
    \subsection{Default declarations}
    *                                                      *
    *********************************************************
    -}

    rnDefaultDecl :: DefaultDecl GhcPs -> RnM (DefaultDecl GhcRn, FreeVars)
    rnDefaultDecl (DefaultDecl tys)
      = do { (tys', fvs) <- rnLHsTypes doc_str tys
           ; return (DefaultDecl tys', fvs) }
      where
        doc_str = DefaultDeclCtx

    {-
    *********************************************************
    *                                                      *
    \subsection{Foreign declarations}
    *                                                      *
    *********************************************************
    -}

    rnHsForeignDecl :: ForeignDecl GhcPs -> RnM (ForeignDecl GhcRn, FreeVars)
    rnHsForeignDecl (ForeignImport { fd_name = name, fd_sig_ty = ty, fd_fi = spec })
      = do { topEnv :: HscEnv <- getTopEnv
           ; name' <- lookupLocatedTopBndrRn name
           ; (ty', fvs) <- rnHsSigType (ForeignDeclCtx name) ty

            -- Mark any PackageTarget style imports as coming from the current package
           ; let unitId = thisPackage $ hsc_dflags topEnv
                 spec'      = patchForeignImport unitId spec

           ; return (ForeignImport { fd_name = name', fd_sig_ty = ty'
                                   , fd_co = noForeignImportCoercionYet
                                   , fd_fi = spec' }, fvs) }

    rnHsForeignDecl (ForeignExport { fd_name = name, fd_sig_ty = ty, fd_fe = spec })
      = do { name' <- lookupLocatedOccRn name
           ; (ty', fvs) <- rnHsSigType (ForeignDeclCtx name) ty
           ; return (ForeignExport { fd_name = name', fd_sig_ty = ty'
                                   , fd_co = noForeignExportCoercionYet
                                   , fd_fe = spec }
                    , fvs `addOneFV` unLoc name') }
            -- NB: a foreign export is an *occurrence site* for name, so
            --     we add it to the free-variable list.  It might, for example,
            --     be imported from another module

    -- | For Windows DLLs we need to know what packages imported symbols are from
    --      to generate correct calls. Imported symbols are tagged with the current
    --      package, so if they get inlined across a package boundry we'll still
    --      know where they're from.
    --
    patchForeignImport :: UnitId -> ForeignImport -> ForeignImport
    patchForeignImport unitId (CImport cconv safety fs spec src)
            = CImport cconv safety fs (patchCImportSpec unitId spec) src

    patchCImportSpec :: UnitId -> CImportSpec -> CImportSpec
    patchCImportSpec unitId spec
     = case spec of
            CFunction callTarget    -> CFunction $ patchCCallTarget unitId callTarget
            _                       -> spec

    patchCCallTarget :: UnitId -> CCallTarget -> CCallTarget
    patchCCallTarget unitId callTarget =
      case callTarget of
      StaticTarget src label Nothing isFun
                                  -> StaticTarget src label (Just unitId) isFun
      _                           -> callTarget

    {-
    *********************************************************
    *                                                      *
    \subsection{Instance declarations}
    *                                                      *
    *********************************************************
    -}

    rnSrcInstDecl :: InstDecl GhcPs -> RnM (InstDecl GhcRn, FreeVars)
    rnSrcInstDecl (TyFamInstD { tfid_inst = tfi })
      = do { (tfi', fvs) <- rnTyFamInstDecl Nothing tfi
           ; return (TyFamInstD { tfid_inst = tfi' }, fvs) }

    rnSrcInstDecl (DataFamInstD { dfid_inst = dfi })
      = do { (dfi', fvs) <- rnDataFamInstDecl Nothing dfi
           ; return (DataFamInstD { dfid_inst = dfi' }, fvs) }

    rnSrcInstDecl (ClsInstD { cid_inst = cid })
      = do { traceRn "rnSrcIstDecl {" (ppr cid)
           ; (cid', fvs) <- rnClsInstDecl cid
           ; traceRn "rnSrcIstDecl end }" empty
           ; return (ClsInstD { cid_inst = cid' }, fvs) }

    -- | Warn about non-canonical typeclass instance declarations
    --
    -- A "non-canonical" instance definition can occur for instances of a
    -- class which redundantly defines an operation its superclass
    -- provides as well (c.f. `return`/`pure`). In such cases, a canonical
    -- instance is one where the subclass inherits its method
    -- implementation from its superclass instance (usually the subclass
    -- has a default method implementation to that effect). Consequently,
    -- a non-canonical instance occurs when this is not the case.
    --
    -- See also descriptions of 'checkCanonicalMonadInstances' and
    -- 'checkCanonicalMonoidInstances'
    checkCanonicalInstances :: Name -> LHsSigType GhcRn -> LHsBinds GhcRn -> RnM ()
    checkCanonicalInstances cls poly_ty mbinds = do
        whenWOptM Opt_WarnNonCanonicalMonadInstances
            checkCanonicalMonadInstances

        whenWOptM Opt_WarnNonCanonicalMonadFailInstances
            checkCanonicalMonadFailInstances

        whenWOptM Opt_WarnNonCanonicalMonoidInstances
            checkCanonicalMonoidInstances

      where
        -- | Warn about unsound/non-canonical 'Applicative'/'Monad' instance
        -- declarations. Specifically, the following conditions are verified:
        --
        -- In 'Monad' instances declarations:
        --
        --  * If 'return' is overridden it must be canonical (i.e. @return = pure@)
        --  * If '(>>)' is overridden it must be canonical (i.e. @(>>) = (*>)@)
        --
        -- In 'Applicative' instance declarations:
        --
        --  * Warn if 'pure' is defined backwards (i.e. @pure = return@).
        --  * Warn if '(*>)' is defined backwards (i.e. @(*>) = (>>)@).
        --
        checkCanonicalMonadInstances
          | cls == applicativeClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == pureAName, isAliasMG mg == Just returnMName
                          -> addWarnNonCanonicalMethod1
                                Opt_WarnNonCanonicalMonadInstances "pure" "return"

                          | name == thenAName, isAliasMG mg == Just thenMName
                          -> addWarnNonCanonicalMethod1
                                Opt_WarnNonCanonicalMonadInstances "(*>)" "(>>)"

                      _ -> return ()

          | cls == monadClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == returnMName, isAliasMG mg /= Just pureAName
                          -> addWarnNonCanonicalMethod2
                                Opt_WarnNonCanonicalMonadInstances "return" "pure"

                          | name == thenMName, isAliasMG mg /= Just thenAName
                          -> addWarnNonCanonicalMethod2
                                Opt_WarnNonCanonicalMonadInstances "(>>)" "(*>)"

                      _ -> return ()

          | otherwise = return ()

        -- | Warn about unsound/non-canonical 'Monad'/'MonadFail' instance
        -- declarations. Specifically, the following conditions are verified:
        --
        -- In 'Monad' instances declarations:
        --
        --  * If 'fail' is overridden it must be canonical
        --    (i.e. @fail = Control.Monad.Fail.fail@)
        --
        -- In 'MonadFail' instance declarations:
        --
        --  * Warn if 'fail' is defined backwards
        --    (i.e. @fail = Control.Monad.fail@).
        --
        checkCanonicalMonadFailInstances
          | cls == monadFailClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == failMName, isAliasMG mg == Just failMName_preMFP
                          -> addWarnNonCanonicalMethod1
                                Opt_WarnNonCanonicalMonadFailInstances "fail"
                                "Control.Monad.fail"

                      _ -> return ()

          | cls == monadClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == failMName_preMFP, isAliasMG mg /= Just failMName
                          -> addWarnNonCanonicalMethod2
                                Opt_WarnNonCanonicalMonadFailInstances "fail"
                                "Control.Monad.Fail.fail"
                      _ -> return ()

          | otherwise = return ()

        -- | Check whether Monoid(mappend) is defined in terms of
        -- Semigroup((<>)) (and not the other way round). Specifically,
        -- the following conditions are verified:
        --
        -- In 'Monoid' instances declarations:
        --
        --  * If 'mappend' is overridden it must be canonical
        --    (i.e. @mappend = (<>)@)
        --
        -- In 'Semigroup' instance declarations:
        --
        --  * Warn if '(<>)' is defined backwards (i.e. @(<>) = mappend@).
        --
        checkCanonicalMonoidInstances
          | cls == semigroupClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == sappendName, isAliasMG mg == Just mappendName
                          -> addWarnNonCanonicalMethod1
                                Opt_WarnNonCanonicalMonoidInstances "(<>)" "mappend"

                      _ -> return ()

          | cls == monoidClassName  = do
              forM_ (bagToList mbinds) $ \(L loc mbind) -> setSrcSpan loc $ do
                  case mbind of
                      FunBind { fun_id = L _ name, fun_matches = mg }
                          | name == mappendName, isAliasMG mg /= Just sappendName
                          -> addWarnNonCanonicalMethod2NoDefault
                                Opt_WarnNonCanonicalMonoidInstances "mappend" "(<>)"

                      _ -> return ()

          | otherwise = return ()

        -- | test whether MatchGroup represents a trivial \"lhsName = rhsName\"
        -- binding, and return @Just rhsName@ if this is the case
        isAliasMG :: MatchGroup GhcRn (LHsExpr GhcRn) -> Maybe Name
        isAliasMG MG {mg_alts = L _ [L _ (Match { m_pats = [], m_grhss = grhss })]}
            | GRHSs [L _ (GRHS [] body)] lbinds <- grhss
            , L _ EmptyLocalBinds <- lbinds
            , L _ (HsVar (L _ rhsName)) <- body  = Just rhsName
        isAliasMG _ = Nothing

        -- got "lhs = rhs" but expected something different
        addWarnNonCanonicalMethod1 flag lhs rhs = do
            addWarn (Reason flag) $ vcat
                           [ text "Noncanonical" <+>
                             quotes (text (lhs ++ " = " ++ rhs)) <+>
                             text "definition detected"
                           , instDeclCtxt1 poly_ty
                           , text "Move definition from" <+>
                             quotes (text rhs) <+>
                             text "to" <+> quotes (text lhs)
                           ]

        -- expected "lhs = rhs" but got something else
        addWarnNonCanonicalMethod2 flag lhs rhs = do
            addWarn (Reason flag) $ vcat
                           [ text "Noncanonical" <+>
                             quotes (text lhs) <+>
                             text "definition detected"
                           , instDeclCtxt1 poly_ty
                           , text "Either remove definition for" <+>
                             quotes (text lhs) <+> text "or define as" <+>
                             quotes (text (lhs ++ " = " ++ rhs))
                           ]

        -- like above, but method has no default impl
        addWarnNonCanonicalMethod2NoDefault flag lhs rhs = do
            addWarn (Reason flag) $ vcat
                           [ text "Noncanonical" <+>
                             quotes (text lhs) <+>
                             text "definition detected"
                           , instDeclCtxt1 poly_ty
                           , text "Define as" <+>
                             quotes (text (lhs ++ " = " ++ rhs))
                           ]

        -- stolen from TcInstDcls
        instDeclCtxt1 :: LHsSigType GhcRn -> SDoc
        instDeclCtxt1 hs_inst_ty
          = inst_decl_ctxt (ppr (getLHsInstDeclHead hs_inst_ty))

        inst_decl_ctxt :: SDoc -> SDoc
        inst_decl_ctxt doc = hang (text "in the instance declaration for")
                             2 (quotes doc <> text ".")

    rnClsInstDecl :: ClsInstDecl GhcPs -> RnM (ClsInstDecl GhcRn, FreeVars)
    rnClsInstDecl (ClsInstDecl { cid_poly_ty = inst_ty, cid_binds = mbinds
                               , cid_sigs = uprags, cid_tyfam_insts = ats
                               , cid_overlap_mode = oflag
                               , cid_datafam_insts = adts })
      = do { (inst_ty', inst_fvs) <- rnLHsInstType (text "an instance declaration") inst_ty
           ; let (ktv_names, _, head_ty') = splitLHsInstDeclTy inst_ty'
           ; let cls = case hsTyGetAppHead_maybe head_ty' of
                         Nothing -> mkUnboundName (mkTcOccFS (fsLit "<class>"))
                         Just (L _ cls, _) -> cls
                         -- rnLHsInstType has added an error message
                         -- if hsTyGetAppHead_maybe fails

              -- Rename the bindings
              -- The typechecker (not the renamer) checks that all
              -- the bindings are for the right class
              -- (Slightly strangely) when scoped type variables are on, the
              -- forall-d tyvars scope over the method bindings too
           ; (mbinds', uprags', meth_fvs) <- rnMethodBinds False cls ktv_names mbinds uprags

           ; checkCanonicalInstances cls inst_ty' mbinds'

           -- Rename the associated types, and type signatures
           -- Both need to have the instance type variables in scope
           ; traceRn "rnSrcInstDecl" (ppr inst_ty' $$ ppr ktv_names)
           ; ((ats', adts'), more_fvs)
                 <- extendTyVarEnvFVRn ktv_names $
                    do { (ats',  at_fvs)  <- rnATInstDecls rnTyFamInstDecl cls ktv_names ats
                       ; (adts', adt_fvs) <- rnATInstDecls rnDataFamInstDecl cls ktv_names adts
                       ; return ( (ats', adts'), at_fvs `plusFV` adt_fvs) }

           ; let all_fvs = meth_fvs `plusFV` more_fvs
                                    `plusFV` inst_fvs
           ; return (ClsInstDecl { cid_poly_ty = inst_ty', cid_binds = mbinds'
                                 , cid_sigs = uprags', cid_tyfam_insts = ats'
                                 , cid_overlap_mode = oflag
                                 , cid_datafam_insts = adts' },
                     all_fvs) }
                 -- We return the renamed associated data type declarations so
                 -- that they can be entered into the list of type declarations
                 -- for the binding group, but we also keep a copy in the instance.
                 -- The latter is needed for well-formedness checks in the type
                 -- checker (eg, to ensure that all ATs of the instance actually
                 -- receive a declaration).
                 -- NB: Even the copies in the instance declaration carry copies of
                 --     the instance context after renaming.  This is a bit
                 --     strange, but should not matter (and it would be more work
                 --     to remove the context).

    rnFamInstEqn :: HsDocContext
                 -> Maybe (Name, [Name]) -- Nothing => not associated
                                         -- Just (cls,tvs) => associated,
                                         --   and gives class and tyvars of the
                                         --   parent instance delc
                 -> [Located RdrName]    -- Kind variables from the equation's RHS
                 -> FamInstEqn GhcPs rhs
                 -> (HsDocContext -> rhs -> RnM (rhs', FreeVars))
                 -> RnM (FamInstEqn GhcRn rhs', FreeVars)
    rnFamInstEqn doc mb_cls rhs_kvars
        (HsIB { hsib_body = FamEqn { feqn_tycon  = tycon
                                   , feqn_pats   = pats
                                   , feqn_fixity = fixity
                                   , feqn_rhs    = payload }}) rn_payload
      = do { tycon'   <- lookupFamInstName (fmap fst mb_cls) tycon
           ; let loc = case pats of
                         []             -> pprPanic "rnFamInstEqn" (ppr tycon)
                         (L loc _ : []) -> loc
                         (L loc _ : ps) -> combineSrcSpans loc (getLoc (last ps))

           ; pat_kity_vars_with_dups <- extractHsTysRdrTyVarsDups pats
           ; let pat_vars = freeKiTyVarsAllVars $
                            rmDupsInRdrTyVars pat_kity_vars_with_dups
                 -- Use the "...Dups" form because it's needed
                 -- below to report unsed binder on the LHS
           ; pat_var_names <- mapM (newTyVarNameRn mb_cls . L loc . unLoc) pat_vars

                 -- Make sure to filter out the kind variables that were explicitly
                 -- bound in the type patterns.
           ; let payload_vars = filterOut (`elemRdr` pat_vars) rhs_kvars
           ; payload_var_names <- mapM (newTyVarNameRn mb_cls) payload_vars

           ; let all_var_names = pat_var_names ++ payload_var_names

                 -- All the free vars of the family patterns
                 -- with a sensible binding location
           ; ((pats', payload'), fvs)
                  <- bindLocalNamesFV all_var_names $
                     do { (pats', pat_fvs) <- rnLHsTypes (FamPatCtx tycon) pats
                        ; (payload', rhs_fvs) <- rn_payload doc payload

                           -- Report unused binders on the LHS
                           -- See Note [Unused type variables in family instances]
                        ; let groups :: [NonEmpty (Located RdrName)]
                              groups = equivClasses cmpLocated $
                                       freeKiTyVarsAllVars pat_kity_vars_with_dups
                        ; tv_nms_dups <- mapM (lookupOccRn . unLoc) $
                                         [ tv | (tv :| (_:_)) <- groups ]
                              -- Add to the used variables
                              --  a) any variables that appear *more than once* on the LHS
                              --     e.g.   F a Int a = Bool
                              --  b) for associated instances, the variables
                              --     of the instance decl.  See
                              --     Note [Unused type variables in family instances]
                        ; let tv_nms_used = extendNameSetList rhs_fvs $
                                            inst_tvs ++ tv_nms_dups
                              inst_tvs = case mb_cls of
                                           Nothing            -> []
                                           Just (_, inst_tvs) -> inst_tvs
                        ; warnUnusedTypePatterns pat_var_names tv_nms_used

                             -- See Note [Renaming associated types]
                        ; let bad_tvs = case mb_cls of
                                          Nothing           -> []
                                          Just (_,cls_tkvs) -> filter is_bad cls_tkvs
                              var_name_set = mkNameSet all_var_names

                              is_bad cls_tkv = cls_tkv `elemNameSet` rhs_fvs
                                            && not (cls_tkv `elemNameSet` var_name_set)
                        ; unless (null bad_tvs) (badAssocRhs bad_tvs)

                        ; return ((pats', payload'), rhs_fvs `plusFV` pat_fvs) }

           ; let anon_wcs = concatMap collectAnonWildCards pats'
                 all_ibs  = anon_wcs ++ all_var_names
                            -- all_ibs: include anonymous wildcards in the implicit
                            -- binders In a type pattern they behave just like any
                            -- other type variable except for being anoymous.  See
                            -- Note [Wildcards in family instances]
                 all_fvs  = fvs `addOneFV` unLoc tycon'
                            -- type instance => use, hence addOneFV

           ; return (HsIB { hsib_vars = all_ibs
                          , hsib_closed = True
                          , hsib_body
                              = FamEqn { feqn_tycon  = tycon'
                                       , feqn_pats   = pats'
                                       , feqn_fixity = fixity
                                       , feqn_rhs    = payload' } },
                     all_fvs) }

    rnTyFamInstDecl :: Maybe (Name, [Name])
                    -> TyFamInstDecl GhcPs
                    -> RnM (TyFamInstDecl GhcRn, FreeVars)
    rnTyFamInstDecl mb_cls (TyFamInstDecl { tfid_eqn = eqn })
      = do { (eqn', fvs) <- rnTyFamInstEqn mb_cls eqn
           ; return (TyFamInstDecl { tfid_eqn = eqn' }, fvs) }

    rnTyFamInstEqn :: Maybe (Name, [Name])
                   -> TyFamInstEqn GhcPs
                   -> RnM (TyFamInstEqn GhcRn, FreeVars)
    rnTyFamInstEqn mb_cls eqn@(HsIB { hsib_body = FamEqn { feqn_tycon = tycon
                                                         , feqn_rhs   = rhs }})
      = do { rhs_kvs <- extractHsTyRdrTyVarsKindVars rhs
           ; rnFamInstEqn (TySynCtx tycon) mb_cls rhs_kvs eqn rnTySyn }

    rnTyFamDefltEqn :: Name
                    -> TyFamDefltEqn GhcPs
                    -> RnM (TyFamDefltEqn GhcRn, FreeVars)
    rnTyFamDefltEqn cls (FamEqn { feqn_tycon  = tycon
                                , feqn_pats   = tyvars
                                , feqn_fixity = fixity
                                , feqn_rhs    = rhs })
      = do { kvs <- extractHsTyRdrTyVarsKindVars rhs
           ; bindHsQTyVars ctx Nothing (Just cls) kvs tyvars $ \ tyvars' _ ->
        do { tycon'      <- lookupFamInstName (Just cls) tycon
           ; (rhs', fvs) <- rnLHsType ctx rhs
           ; return (FamEqn { feqn_tycon  = tycon'
                            , feqn_pats   = tyvars'
                            , feqn_fixity = fixity
                            , feqn_rhs    = rhs' }, fvs) } }
      where
        ctx = TyFamilyCtx tycon

    rnDataFamInstDecl :: Maybe (Name, [Name])
                      -> DataFamInstDecl GhcPs
                      -> RnM (DataFamInstDecl GhcRn, FreeVars)
    rnDataFamInstDecl mb_cls (DataFamInstDecl { dfid_eqn = eqn@(HsIB { hsib_body =
                               FamEqn { feqn_tycon = tycon
                                      , feqn_rhs   = rhs }})})
      = do { rhs_kvs <- extractDataDefnKindVars rhs
           ; (eqn', fvs) <-
               rnFamInstEqn (TyDataCtx tycon) mb_cls rhs_kvs eqn rnDataDefn
           ; return (DataFamInstDecl { dfid_eqn = eqn' }, fvs) }

    -- Renaming of the associated types in instances.

    -- Rename associated type family decl in class
    rnATDecls :: Name      -- Class
              -> [LFamilyDecl GhcPs]
              -> RnM ([LFamilyDecl GhcRn], FreeVars)
    rnATDecls cls at_decls
      = rnList (rnFamDecl (Just cls)) at_decls

    rnATInstDecls :: (Maybe (Name, [Name]) -> -- The function that renames
                      decl GhcPs ->            -- an instance. rnTyFamInstDecl
                      RnM (decl GhcRn, FreeVars)) -- or rnDataFamInstDecl
                  -> Name      -- Class
                  -> [Name]
                  -> [Located (decl GhcPs)]
                  -> RnM ([Located (decl GhcRn)], FreeVars)
    -- Used for data and type family defaults in a class decl
    -- and the family instance declarations in an instance
    --
    -- NB: We allow duplicate associated-type decls;
    --     See Note [Associated type instances] in TcInstDcls
    rnATInstDecls rnFun cls tv_ns at_insts
      = rnList (rnFun (Just (cls, tv_ns))) at_insts
        -- See Note [Renaming associated types]

    {- Note [Wildcards in family instances]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Wild cards can be used in type/data family instance declarations to indicate
    that the name of a type variable doesn't matter. Each wild card will be
    replaced with a new unique type variable. For instance:

        type family F a b :: *
        type instance F Int _ = Int

    is the same as

        type family F a b :: *
        type instance F Int b = Int

    This is implemented as follows: during renaming anonymous wild cards
    '_' are given freshly generated names. These names are collected after
    renaming (rnFamInstEqn) and used to make new type variables during
    type checking (tc_fam_ty_pats). One should not confuse these wild
    cards with the ones from partial type signatures. The latter generate
    fresh meta-variables whereas the former generate fresh skolems.

    Note [Unused type variables in family instances]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    When the flag -fwarn-unused-type-patterns is on, the compiler reports
    warnings about unused type variables in type-family instances. A
    tpye variable is considered used (i.e. cannot be turned into a wildcard)
    when

     * it occurs on the RHS of the family instance
       e.g.   type instance F a b = a    -- a is used on the RHS

     * it occurs multiple times in the patterns on the LHS
       e.g.   type instance F a a = Int  -- a appears more than once on LHS

     * it is one of the instance-decl variables, for associated types
       e.g.   instance C (a,b) where
                type T (a,b) = a
       Here the type pattern in the type instance must be the same as that
       for the class instance, so
                type T (a,_) = a
       would be rejected.  So we should not complain about an unused variable b

    As usual, the warnings are not reported for for type variables with names
    beginning with an underscore.

    Extra-constraints wild cards are not supported in type/data family
    instance declarations.

    Relevant tickets: #3699, #10586, #10982 and #11451.

    Note [Renaming associated types]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Check that the RHS of the decl mentions only type variables that are explicitly
    bound on the LHS.  For example, this is not ok
       class C a b where
          type F a x :: *
       instance C (p,q) r where
          type F (p,q) x = (x, r)   -- BAD: mentions 'r'
    c.f. Trac #5515

    Kind variables, on the other hand, are allowed to be implicitly or explicitly
    bound. As examples, this (#9574) is acceptable:
       class Funct f where
          type Codomain f :: *
       instance Funct ('KProxy :: KProxy o) where
          -- o is implicitly bound by the kind signature
          -- of the LHS type pattern ('KProxy)
          type Codomain 'KProxy = NatTr (Proxy :: o -> *)
    And this (#14131) is also acceptable:
        data family Nat :: k -> k -> *
        -- k is implicitly bound by an invisible kind pattern
        newtype instance Nat :: (k -> *) -> (k -> *) -> * where
          Nat :: (forall xx. f xx -> g xx) -> Nat f g
    We could choose to disallow this, but then associated type families would not
    be able to be as expressive as top-level type synonyms. For example, this type
    synonym definition is allowed:
        type T = (Nothing :: Maybe a)
    So for parity with type synonyms, we also allow:
        type family   T :: Maybe a
        type instance T = (Nothing :: Maybe a)

    All this applies only for *instance* declarations.  In *class*
    declarations there is no RHS to worry about, and the class variables
    can all be in scope (Trac #5862):
        class Category (x :: k -> k -> *) where
          type Ob x :: k -> Constraint
          id :: Ob x a => x a a
          (.) :: (Ob x a, Ob x b, Ob x c) => x b c -> x a b -> x a c
    Here 'k' is in scope in the kind signature, just like 'x'.
    -}

    {-
    *********************************************************
    *                                                      *
    \subsection{Stand-alone deriving declarations}
    *                                                      *
    *********************************************************
    -}

    rnSrcDerivDecl :: DerivDecl GhcPs -> RnM (DerivDecl GhcRn, FreeVars)
    rnSrcDerivDecl (DerivDecl ty deriv_strat overlap)
      = do { standalone_deriv_ok <- xoptM LangExt.StandaloneDeriving
           ; deriv_strats_ok     <- xoptM LangExt.DerivingStrategies
           ; unless standalone_deriv_ok (addErr standaloneDerivErr)
           ; failIfTc (isJust deriv_strat && not deriv_strats_ok) $
               illegalDerivStrategyErr $ fmap unLoc deriv_strat
           ; (ty', fvs) <- rnLHsInstType (text "a deriving declaration") ty
           ; return (DerivDecl ty' deriv_strat overlap, fvs) }

    standaloneDerivErr :: SDoc
    standaloneDerivErr
      = hang (text "Illegal standalone deriving declaration")
           2 (text "Use StandaloneDeriving to enable this extension")

    {-
    *********************************************************
    *                                                      *
    \subsection{Rules}
    *                                                      *
    *********************************************************
    -}

    rnHsRuleDecls :: RuleDecls GhcPs -> RnM (RuleDecls GhcRn, FreeVars)
    rnHsRuleDecls (HsRules src rules)
      = do { (rn_rules,fvs) <- rnList rnHsRuleDecl rules
           ; return (HsRules src rn_rules,fvs) }

    rnHsRuleDecl :: RuleDecl GhcPs -> RnM (RuleDecl GhcRn, FreeVars)
    rnHsRuleDecl (HsRule rule_name act vars lhs _fv_lhs rhs _fv_rhs)
      = do { let rdr_names_w_loc = map get_var vars
           ; checkDupRdrNames rdr_names_w_loc
           ; checkShadowedRdrNames rdr_names_w_loc
           ; names <- newLocalBndrsRn rdr_names_w_loc
           ; bindHsRuleVars (snd $ unLoc rule_name) vars names $ \ vars' ->
        do { (lhs', fv_lhs') <- rnLExpr lhs
           ; (rhs', fv_rhs') <- rnLExpr rhs
           ; checkValidRule (snd $ unLoc rule_name) names lhs' fv_lhs'
           ; return (HsRule rule_name act vars' lhs' fv_lhs' rhs' fv_rhs',
                     fv_lhs' `plusFV` fv_rhs') } }
      where
        get_var (L _ (RuleBndrSig v _)) = v
        get_var (L _ (RuleBndr v)) = v

    bindHsRuleVars :: RuleName -> [LRuleBndr GhcPs] -> [Name]
                   -> ([LRuleBndr GhcRn] -> RnM (a, FreeVars))
                   -> RnM (a, FreeVars)
    bindHsRuleVars rule_name vars names thing_inside
      = go vars names $ \ vars' ->
        bindLocalNamesFV names (thing_inside vars')
      where
        doc = RuleCtx rule_name

        go (L l (RuleBndr (L loc _)) : vars) (n : ns) thing_inside
          = go vars ns $ \ vars' ->
            thing_inside (L l (RuleBndr (L loc n)) : vars')

        go (L l (RuleBndrSig (L loc _) bsig) : vars) (n : ns) thing_inside
          = rnHsSigWcTypeScoped doc bsig $ \ bsig' ->
            go vars ns $ \ vars' ->
            thing_inside (L l (RuleBndrSig (L loc n) bsig') : vars')

        go [] [] thing_inside = thing_inside []
        go vars names _ = pprPanic "bindRuleVars" (ppr vars $$ ppr names)

    {-
    Note [Rule LHS validity checking]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Check the shape of a transformation rule LHS.  Currently we only allow
    LHSs of the form @(f e1 .. en)@, where @f@ is not one of the
    @forall@'d variables.

    We used restrict the form of the 'ei' to prevent you writing rules
    with LHSs with a complicated desugaring (and hence unlikely to match);
    (e.g. a case expression is not allowed: too elaborate.)

    But there are legitimate non-trivial args ei, like sections and
    lambdas.  So it seems simmpler not to check at all, and that is why
    check_e is commented out.
    -}

    checkValidRule :: FastString -> [Name] -> LHsExpr GhcRn -> NameSet -> RnM ()
    checkValidRule rule_name ids lhs' fv_lhs'
      = do  {       -- Check for the form of the LHS
              case (validRuleLhs ids lhs') of
                    Nothing  -> return ()
                    Just bad -> failWithTc (badRuleLhsErr rule_name lhs' bad)

                    -- Check that LHS vars are all bound
            ; let bad_vars = [var | var <- ids, not (var `elemNameSet` fv_lhs')]
            ; mapM_ (addErr . badRuleVar rule_name) bad_vars }

    validRuleLhs :: [Name] -> LHsExpr GhcRn -> Maybe (HsExpr GhcRn)
    -- Nothing => OK
    -- Just e  => Not ok, and e is the offending sub-expression
    validRuleLhs foralls lhs
      = checkl lhs
      where
        checkl (L _ e) = check e

        check (OpApp e1 op _ e2)              = checkl op `mplus` checkl_e e1 `mplus` checkl_e e2
        check (HsApp e1 e2)                   = checkl e1 `mplus` checkl_e e2
        check (HsAppType e _)                 = checkl e
        check (HsVar (L _ v)) | v `notElem` foralls = Nothing
        check other                           = Just other  -- Failure

            -- Check an argument
        checkl_e (L _ _e) = Nothing         -- Was (check_e e); see Note [Rule LHS validity checking]

    {-      Commented out; see Note [Rule LHS validity checking] above
        check_e (HsVar v)     = Nothing
        check_e (HsPar e)     = checkl_e e
        check_e (HsLit e)     = Nothing
        check_e (HsOverLit e) = Nothing

        check_e (OpApp e1 op _ e2)   = checkl_e e1 `mplus` checkl_e op `mplus` checkl_e e2
        check_e (HsApp e1 e2)        = checkl_e e1 `mplus` checkl_e e2
        check_e (NegApp e _)         = checkl_e e
        check_e (ExplicitList _ es)  = checkl_es es
        check_e other                = Just other   -- Fails

        checkl_es es = foldr (mplus . checkl_e) Nothing es
    -}

    badRuleVar :: FastString -> Name -> SDoc
    badRuleVar name var
      = sep [text "Rule" <+> doubleQuotes (ftext name) <> colon,
             text "Forall'd variable" <+> quotes (ppr var) <+>
                    text "does not appear on left hand side"]

    badRuleLhsErr :: FastString -> LHsExpr GhcRn -> HsExpr GhcRn -> SDoc
    badRuleLhsErr name lhs bad_e
      = sep [text "Rule" <+> pprRuleName name <> colon,
             nest 4 (vcat [err,
                           text "in left-hand side:" <+> ppr lhs])]
        $$
        text "LHS must be of form (f e1 .. en) where f is not forall'd"
      where
        err = case bad_e of
                HsUnboundVar uv -> text "Not in scope:" <+> ppr uv
                _ -> text "Illegal expression:" <+> ppr bad_e

    {-
    *********************************************************
    *                                                      *
    \subsection{Vectorisation declarations}
    *                                                      *
    *********************************************************
    -}

    rnHsVectDecl :: VectDecl GhcPs -> RnM (VectDecl GhcRn, FreeVars)
    -- FIXME: For the moment, the right-hand side is restricted to be a variable as we cannot properly
    --        typecheck a complex right-hand side without invoking 'vectType' from the vectoriser.
    rnHsVectDecl (HsVect s var rhs@(L _ (HsVar _)))
      = do { var' <- lookupLocatedOccRn var
           ; (rhs', fv_rhs) <- rnLExpr rhs
           ; return (HsVect s var' rhs', fv_rhs `addOneFV` unLoc var')
           }
    rnHsVectDecl (HsVect _ _var _rhs)
      = failWith $ vcat
                   [ text "IMPLEMENTATION RESTRICTION: right-hand side of a VECTORISE pragma"
                   , text "must be an identifier"
                   ]
    rnHsVectDecl (HsNoVect s var)
      = do { var' <- lookupLocatedTopBndrRn var           -- only applies to local (not imported) names
           ; return (HsNoVect s var', unitFV (unLoc var'))
           }
    rnHsVectDecl (HsVectTypeIn s isScalar tycon Nothing)
      = do { tycon' <- lookupLocatedOccRn tycon
           ; return (HsVectTypeIn s isScalar tycon' Nothing, unitFV (unLoc tycon'))
           }
    rnHsVectDecl (HsVectTypeIn s isScalar tycon (Just rhs_tycon))
      = do { tycon'     <- lookupLocatedOccRn tycon
           ; rhs_tycon' <- lookupLocatedOccRn rhs_tycon
           ; return ( HsVectTypeIn s isScalar tycon' (Just rhs_tycon')
                    , mkFVs [unLoc tycon', unLoc rhs_tycon'])
           }
    rnHsVectDecl (HsVectTypeOut _ _ _)
      = panic "RnSource.rnHsVectDecl: Unexpected 'HsVectTypeOut'"
    rnHsVectDecl (HsVectClassIn s cls)
      = do { cls' <- lookupLocatedOccRn cls
           ; return (HsVectClassIn s cls', unitFV (unLoc cls'))
           }
    rnHsVectDecl (HsVectClassOut _)
      = panic "RnSource.rnHsVectDecl: Unexpected 'HsVectClassOut'"
    rnHsVectDecl (HsVectInstIn instTy)
      = do { (instTy', fvs) <- rnLHsInstType (text "a VECTORISE pragma") instTy
           ; return (HsVectInstIn instTy', fvs)
           }
    rnHsVectDecl (HsVectInstOut _)
      = panic "RnSource.rnHsVectDecl: Unexpected 'HsVectInstOut'"

    {- **************************************************************
             *                                                      *
          Renaming type, class, instance and role declarations
    *                                                               *
    *****************************************************************

    @rnTyDecl@ uses the `global name function' to create a new type
    declaration in which local names have been replaced by their original
    names, reporting any unknown names.

    Renaming type variables is a pain. Because they now contain uniques,
    it is necessary to pass in an association list which maps a parsed
    tyvar to its @Name@ representation.
    In some cases (type signatures of values),
    it is even necessary to go over the type first
    in order to get the set of tyvars used by it, make an assoc list,
    and then go over it again to rename the tyvars!
    However, we can also do some scoping checks at the same time.

    Note [Dependency analysis of type, class, and instance decls]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    A TyClGroup represents a strongly connected components of
    type/class/instance decls, together with the role annotations for the
    type/class declarations.  The renamer uses strongly connected
    comoponent analysis to build these groups.  We do this for a number of
    reasons:

    * Improve kind error messages. Consider

         data T f a = MkT f a
         data S f a = MkS f (T f a)

      This has a kind error, but the error message is better if you
      check T first, (fixing its kind) and *then* S.  If you do kind
      inference together, you might get an error reported in S, which
      is jolly confusing.  See Trac #4875

    * Increase kind polymorphism.  See TcTyClsDecls
      Note [Grouping of type and class declarations]

    Why do the instance declarations participate?  At least two reasons

    * Consider (Trac #11348)

         type family F a
         type instance F Int = Bool

         data R = MkR (F Int)

         type Foo = 'MkR 'True

      For Foo to kind-check we need to know that (F Int) ~ Bool.  But we won't
      know that unless we've looked at the type instance declaration for F
      before kind-checking Foo.

    * Another example is this (Trac #3990).

         data family Complex a
         data instance Complex Double = CD {-# UNPACK #-} !Double
                                           {-# UNPACK #-} !Double

         data T = T {-# UNPACK #-} !(Complex Double)

      Here, to generate the right kind of unpacked implementation for T,
      we must have access to the 'data instance' declaration.

    * Things become more complicated when we introduce transitive
      dependencies through imported definitions, like in this scenario:

          A.hs
            type family Closed (t :: Type) :: Type where
              Closed t = Open t

            type family Open (t :: Type) :: Type

          B.hs
            data Q where
              Q :: Closed Bool -> Q

            type instance Open Int = Bool

            type S = 'Q 'True

      Somehow, we must ensure that the instance Open Int = Bool is checked before
      the type synonym S. While we know that S depends upon 'Q depends upon Closed,
      we have no idea that Closed depends upon Open!

      To accomodate for these situations, we ensure that an instance is checked
      before every @TyClDecl@ on which it does not depend. That's to say, instances
      are checked as early as possible in @tcTyAndClassDecls@.

    ------------------------------------
    So much for WHY.  What about HOW?  It's pretty easy:

    (1) Rename the type/class, instance, and role declarations
        individually

    (2) Do strongly-connected component analysis of the type/class decls,
        We'll make a TyClGroup for each SCC

        In this step we treat a reference to a (promoted) data constructor
        K as a dependency on its parent type.  Thus
            data T = K1 | K2
            data S = MkS (Proxy 'K1)
        Here S depends on 'K1 and hence on its parent T.

        In this step we ignore instances; see
        Note [No dependencies on data instances]

    (3) Attach roles to the appropriate SCC

    (4) Attach instances to the appropriate SCC.
        We add an instance decl to SCC when:
          all its free types/classes are bound in this SCC or earlier ones

    (5) We make an initial TyClGroup, with empty group_tyclds, for any
        (orphan) instances that affect only imported types/classes

    Steps (3) and (4) are done by the (mapAccumL mk_group) call.

    Note [No dependencies on data instances]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    Consider this
       data family D a
       data instance D Int = D1
       data S = MkS (Proxy 'D1)

    Here the declaration of S depends on the /data instance/ declaration
    for 'D Int'.  That makes things a lot more complicated, especially
    if the data instance is an associated type of an enclosing class instance.
    (And the class instance might have several associated type instances
    with different dependency structure!)

    Ugh.  For now we simply don't allow promotion of data constructors for
    data instances.  See Note [AFamDataCon: not promoting data family
    constructors] in TcEnv
    -}

    rnTyClDecls :: [TyClGroup GhcPs]
                -> RnM ([TyClGroup GhcRn], FreeVars)
    -- Rename the declarations and do dependency analysis on them
    rnTyClDecls tycl_ds
      = do { -- Rename the type/class, instance, and role declaraations
             tycls_w_fvs <- mapM (wrapLocFstM rnTyClDecl)
                                 (tyClGroupTyClDecls tycl_ds)
           ; let tc_names = mkNameSet (map (tcdName . unLoc . fst) tycls_w_fvs)

           ; instds_w_fvs <- mapM (wrapLocFstM rnSrcInstDecl) (tyClGroupInstDecls tycl_ds)
           ; role_annots  <- rnRoleAnnots tc_names (tyClGroupRoleDecls tycl_ds)

           -- Do SCC analysis on the type/class decls
           ; rdr_env <- getGlobalRdrEnv
           ; let tycl_sccs = depAnalTyClDecls rdr_env tycls_w_fvs
                 role_annot_env = mkRoleAnnotEnv role_annots

                 inst_ds_map = mkInstDeclFreeVarsMap rdr_env tc_names instds_w_fvs
                 (init_inst_ds, rest_inst_ds) = getInsts [] inst_ds_map

                 first_group
                   | null init_inst_ds = []
                   | otherwise = [TyClGroup { group_tyclds = []
                                            , group_roles  = []
                                            , group_instds = init_inst_ds }]

                 ((final_inst_ds, orphan_roles), groups)
                    = mapAccumL mk_group (rest_inst_ds, role_annot_env) tycl_sccs

                 all_fvs = plusFV (foldr (plusFV . snd) emptyFVs tycls_w_fvs)
                                  (foldr (plusFV . snd) emptyFVs instds_w_fvs)

                 all_groups = first_group ++ groups

           ; ASSERT2( null final_inst_ds,  ppr instds_w_fvs $$ ppr inst_ds_map
                                           $$ ppr (flattenSCCs tycl_sccs) $$ ppr final_inst_ds  )
             mapM_ orphanRoleAnnotErr (nameEnvElts orphan_roles)

           ; traceRn "rnTycl dependency analysis made groups" (ppr all_groups)
           ; return (all_groups, all_fvs) }
      where
        mk_group :: (InstDeclFreeVarsMap, RoleAnnotEnv)
                 -> SCC (LTyClDecl GhcRn)
                 -> ( (InstDeclFreeVarsMap, RoleAnnotEnv)
                    , TyClGroup GhcRn )
        mk_group (inst_map, role_env) scc
          = ((inst_map', role_env'), group)
          where
            tycl_ds              = flattenSCC scc
            bndrs                = map (tcdName . unLoc) tycl_ds
            (inst_ds, inst_map') = getInsts      bndrs inst_map
            (roles,   role_env') = getRoleAnnots bndrs role_env
            group = TyClGroup { group_tyclds = tycl_ds
                              , group_roles  = roles
                              , group_instds = inst_ds }

    depAnalTyClDecls :: GlobalRdrEnv
                     -> [(LTyClDecl GhcRn, FreeVars)]
                     -> [SCC (LTyClDecl GhcRn)]
    -- See Note [Dependency analysis of type, class, and instance decls]
    depAnalTyClDecls rdr_env ds_w_fvs
      = stronglyConnCompFromEdgedVerticesUniq edges
      where
        edges :: [ Node Name (LTyClDecl GhcRn) ]
        edges = [ DigraphNode d (tcdName (unLoc d)) (map (getParent rdr_env) (nonDetEltsUniqSet fvs))
                | (d, fvs) <- ds_w_fvs ]
                -- It's OK to use nonDetEltsUFM here as
                -- stronglyConnCompFromEdgedVertices is still deterministic
                -- even if the edges are in nondeterministic order as explained
                -- in Note [Deterministic SCC] in Digraph.

    toParents :: GlobalRdrEnv -> NameSet -> NameSet
    toParents rdr_env ns
      = nonDetFoldUniqSet add emptyNameSet ns
      -- It's OK to use nonDetFoldUFM because we immediately forget the
      -- ordering by creating a set
      where
        add n s = extendNameSet s (getParent rdr_env n)

    getParent :: GlobalRdrEnv -> Name -> Name
    getParent rdr_env n
      = case lookupGRE_Name rdr_env n of
          Just gre -> case gre_par gre of
                        ParentIs  { par_is = p } -> p
                        FldParent { par_is = p } -> p
                        _                        -> n
          Nothing -> n

    {- ******************************************************
    *                                                       *
           Role annotations
    *                                                       *
    ****************************************************** -}

    -- | Renames role annotations, returning them as the values in a NameEnv
    -- and checks for duplicate role annotations.
    -- It is quite convenient to do both of these in the same place.
    -- See also Note [Role annotations in the renamer]
    rnRoleAnnots :: NameSet
                 -> [LRoleAnnotDecl GhcPs]
                 -> RnM [LRoleAnnotDecl GhcRn]
    rnRoleAnnots tc_names role_annots
      = do {  -- Check for duplicates *before* renaming, to avoid
              -- lumping together all the unboundNames
             let (no_dups, dup_annots) = removeDups role_annots_cmp role_annots
                 role_annots_cmp (L _ annot1) (L _ annot2)
                   = roleAnnotDeclName annot1 `compare` roleAnnotDeclName annot2
           ; mapM_ dupRoleAnnotErr dup_annots
           ; mapM (wrapLocM rn_role_annot1) no_dups }
      where
        rn_role_annot1 (RoleAnnotDecl tycon roles)
          = do {  -- the name is an *occurrence*, but look it up only in the
                  -- decls defined in this group (see #10263)
                 tycon' <- lookupSigCtxtOccRn (RoleAnnotCtxt tc_names)
                                              (text "role annotation")
                                              tycon
               ; return $ RoleAnnotDecl tycon' roles }

    dupRoleAnnotErr :: NonEmpty (LRoleAnnotDecl GhcPs) -> RnM ()
    dupRoleAnnotErr list
      = addErrAt loc $
        hang (text "Duplicate role annotations for" <+>
              quotes (ppr $ roleAnnotDeclName first_decl) <> colon)
           2 (vcat $ map pp_role_annot $ NE.toList sorted_list)
        where
          sorted_list = NE.sortBy cmp_annot list
          (L loc first_decl :| _) = sorted_list

          pp_role_annot (L loc decl) = hang (ppr decl)
                                          4 (text "-- written at" <+> ppr loc)

          cmp_annot (L loc1 _) (L loc2 _) = loc1 `compare` loc2

    orphanRoleAnnotErr :: LRoleAnnotDecl GhcRn -> RnM ()
    orphanRoleAnnotErr (L loc decl)
      = addErrAt loc $
        hang (text "Role annotation for a type previously declared:")
           2 (ppr decl) $$
        parens (text "The role annotation must be given where" <+>
                quotes (ppr $ roleAnnotDeclName decl) <+>
                text "is declared.")

    {- Note [Role annotations in the renamer]
    ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    We must ensure that a type's role annotation is put in the same group as the
    proper type declaration. This is because role annotations are needed during
    type-checking when creating the type's TyCon. So, rnRoleAnnots builds a
    NameEnv (LRoleAnnotDecl Name) that maps a name to a role annotation for that
    type, if any. Then, this map can be used to add the role annotations to the
    groups after dependency analysis.

    This process checks for duplicate role annotations, where we must be careful
    to do the check *before* renaming to avoid calling all unbound names duplicates
    of one another.

    The renaming process, as usual, might identify and report errors for unbound
    names. We exclude the annotations for unbound names in the annotation
    environment to avoid spurious errors for orphaned annotations.

    We then (in rnTyClDecls) do a check for orphan role annotations (role
    annotations without an accompanying type decl). The check works by folding
    over components (of type [[Either (TyClDecl Name) (InstDecl Name)]]), selecting
    out the relevant role declarations for each group, as well as diminishing the
    annotation environment. After the fold is complete, anything left over in the
    name environment must be an orphan, and errors are generated.

    An earlier version of this algorithm short-cut the orphan check by renaming
    only with names declared in this module. But, this check is insufficient in
    the case of staged module compilation (Template Haskell, GHCi).
    See #8485. With the new lookup process (which includes types declared in other
    modules), we get better error messages, too.
    -}

    {- ******************************************************
    *                                                       *
           Dependency info for instances
    *                                                       *
    ****************************************************** -}

    ----------------------------------------------------------
    -- | 'InstDeclFreeVarsMap is an association of an
    --   @InstDecl@ with @FreeVars@. The @FreeVars@ are
    --   the tycon names that are both
    --     a) free in the instance declaration
    --     b) bound by this group of type/class/instance decls
    type InstDeclFreeVarsMap = [(LInstDecl GhcRn, FreeVars)]

    -- | Construct an @InstDeclFreeVarsMap@ by eliminating any @Name@s from the
    --   @FreeVars@ which are *not* the binders of a @TyClDecl@.
    mkInstDeclFreeVarsMap :: GlobalRdrEnv
                          -> NameSet
                          -> [(LInstDecl GhcRn, FreeVars)]
                          -> InstDeclFreeVarsMap
    mkInstDeclFreeVarsMap rdr_env tycl_bndrs inst_ds_fvs
      = [ (inst_decl, toParents rdr_env fvs `intersectFVs` tycl_bndrs)
        | (inst_decl, fvs) <- inst_ds_fvs ]

    -- | Get the @LInstDecl@s which have empty @FreeVars@ sets, and the
    --   @InstDeclFreeVarsMap@ with these entries removed.
    -- We call (getInsts tcs instd_map) when we've completed the declarations
    -- for 'tcs'.  The call returns (inst_decls, instd_map'), where
    --   inst_decls are the instance declarations all of
    --              whose free vars are now defined
    --   instd_map' is the inst-decl map with 'tcs' removed from
    --               the free-var set
    getInsts :: [Name] -> InstDeclFreeVarsMap
             -> ([LInstDecl GhcRn], InstDeclFreeVarsMap)
    getInsts bndrs inst_decl_map
      = partitionWith pick_me inst_decl_map
      where
        pick_me :: (LInstDecl GhcRn, FreeVars)
                -> Either (LInstDecl GhcRn) (LInstDecl GhcRn, FreeVars)
        pick_me (decl, fvs)
          | isEmptyNameSet depleted_fvs = Left decl
          | otherwise                   = Right (decl, depleted_fvs)
          where
            depleted_fvs = delFVs bndrs fvs

    {- ******************************************************
    *                                                       *
             Renaming a type or class declaration
    *                                                       *
    ****************************************************** -}

    rnTyClDecl :: TyClDecl GhcPs
               -> RnM (TyClDecl GhcRn, FreeVars)

    -- All flavours of type family declarations ("type family", "newtype family",
    -- and "data family"), both top level and (for an associated type)
    -- in a class decl
    rnTyClDecl (FamDecl { tcdFam = decl })
      = do { (decl', fvs) <- rnFamDecl Nothing decl
           ; return (FamDecl decl', fvs) }

    rnTyClDecl (SynDecl { tcdLName = tycon, tcdTyVars = tyvars,
                          tcdFixity = fixity, tcdRhs = rhs })
      = do { tycon' <- lookupLocatedTopBndrRn tycon
           ; kvs <- extractHsTyRdrTyVarsKindVars rhs
           ; let doc = TySynCtx tycon
           ; traceRn "rntycl-ty" (ppr tycon <+> ppr kvs)
           ; bindHsQTyVars doc Nothing Nothing kvs tyvars $ \ tyvars' _ ->
        do { (rhs', fvs) <- rnTySyn doc rhs
           ; return (SynDecl { tcdLName = tycon', tcdTyVars = tyvars'
                             , tcdFixity = fixity
                             , tcdRhs = rhs', tcdFVs = fvs }, fvs) } }

    -- "data", "newtype" declarations
    -- both top level and (for an associated type) in an instance decl
    rnTyClDecl (DataDecl { tcdLName = tycon, tcdTyVars = tyvars,
                           tcdFixity = fixity, tcdDataDefn = defn })
      = do { tycon' <- lookupLocatedTopBndrRn tycon
           ; kvs <- extractDataDefnKindVars defn
           ; let doc = TyDataCtx tycon
           ; traceRn "rntycl-data" (ppr tycon <+> ppr kvs)
           ; bindHsQTyVars doc Nothing Nothing kvs tyvars $ \ tyvars' no_rhs_kvs ->
        do { (defn', fvs) <- rnDataDefn doc defn
              -- See Note [Complete user-supplied kind signatures] in HsDecls
           ; typeintype <- xoptM LangExt.TypeInType
           ; let cusk = hsTvbAllKinded tyvars' &&
                        (not typeintype || no_rhs_kvs)
           ; return (DataDecl { tcdLName = tycon', tcdTyVars = tyvars'
                              , tcdFixity = fixity
                              , tcdDataDefn = defn', tcdDataCusk = cusk
                              , tcdFVs = fvs }, fvs) } }

    rnTyClDecl (ClassDecl { tcdCtxt = context, tcdLName = lcls,
                            tcdTyVars = tyvars, tcdFixity = fixity,
                            tcdFDs = fds, tcdSigs = sigs,
                            tcdMeths = mbinds, tcdATs = ats, tcdATDefs = at_defs,
                            tcdDocs = docs})
      = do  { lcls' <- lookupLocatedTopBndrRn lcls
            ; let cls' = unLoc lcls'
                  kvs = []  -- No scoped kind vars except those in
                            -- kind signatures on the tyvars

            -- Tyvars scope over superclass context and method signatures
            ; ((tyvars', context', fds', ats'), stuff_fvs)
                <- bindHsQTyVars cls_doc Nothing Nothing kvs tyvars $ \ tyvars' _ -> do
                      -- Checks for distinct tyvars
                 { (context', cxt_fvs) <- rnContext cls_doc context
                 ; fds'  <- rnFds fds
                             -- The fundeps have no free variables
                 ; (ats', fv_ats) <- rnATDecls cls' ats
                 ; let fvs = cxt_fvs     `plusFV`
                             fv_ats
                 ; return ((tyvars', context', fds', ats'), fvs) }

            ; (at_defs', fv_at_defs) <- rnList (rnTyFamDefltEqn cls') at_defs

            -- No need to check for duplicate associated type decls
            -- since that is done by RnNames.extendGlobalRdrEnvRn

            -- Check the signatures
            -- First process the class op sigs (op_sigs), then the fixity sigs (non_op_sigs).
            ; let sig_rdr_names_w_locs = [op | L _ (ClassOpSig False ops _) <- sigs
                                             , op <- ops]
            ; checkDupRdrNames sig_rdr_names_w_locs
                    -- Typechecker is responsible for checking that we only
                    -- give default-method bindings for things in this class.
                    -- The renamer *could* check this for class decls, but can't
                    -- for instance decls.

            -- The newLocals call is tiresome: given a generic class decl
            --      class C a where
            --        op :: a -> a
            --        op {| x+y |} (Inl a) = ...
            --        op {| x+y |} (Inr b) = ...
            --        op {| a*b |} (a*b)   = ...
            -- we want to name both "x" tyvars with the same unique, so that they are
            -- easy to group together in the typechecker.
            ; (mbinds', sigs', meth_fvs)
                <- rnMethodBinds True cls' (hsAllLTyVarNames tyvars') mbinds sigs
                    -- No need to check for duplicate method signatures
                    -- since that is done by RnNames.extendGlobalRdrEnvRn
                    -- and the methods are already in scope

      -- Haddock docs
            ; docs' <- mapM (wrapLocM rnDocDecl) docs

            ; let all_fvs = meth_fvs `plusFV` stuff_fvs `plusFV` fv_at_defs
            ; return (ClassDecl { tcdCtxt = context', tcdLName = lcls',
                                  tcdTyVars = tyvars', tcdFixity = fixity,
                                  tcdFDs = fds', tcdSigs = sigs',
                                  tcdMeths = mbinds', tcdATs = ats', tcdATDefs = at_defs',
                                  tcdDocs = docs', tcdFVs = all_fvs },
                      all_fvs ) }
      where
        cls_doc  = ClassDeclCtx lcls

    -- "type" and "type instance" declarations
    rnTySyn :: HsDocContext -> LHsType GhcPs -> RnM (LHsType GhcRn, FreeVars)
    rnTySyn doc rhs = rnLHsType doc rhs

    rnDataDefn :: HsDocContext -> HsDataDefn GhcPs
               -> RnM (HsDataDefn GhcRn, FreeVars)
    rnDataDefn doc (HsDataDefn { dd_ND = new_or_data, dd_cType = cType
                               , dd_ctxt = context, dd_cons = condecls
                               , dd_kindSig = m_sig, dd_derivs = derivs })
      = do  { checkTc (h98_style || null (unLoc context))
                      (badGadtStupidTheta doc)

            ; (m_sig', sig_fvs) <- case m_sig of
                 Just sig -> first Just <$> rnLHsKind doc sig
                 Nothing  -> return (Nothing, emptyFVs)
            ; (context', fvs1) <- rnContext doc context
            ; (derivs',  fvs3) <- rn_derivs derivs

            -- For the constructor declarations, drop the LocalRdrEnv
            -- in the GADT case, where the type variables in the declaration
            -- do not scope over the constructor signatures
            -- data T a where { T1 :: forall b. b-> b }
            ; let { zap_lcl_env | h98_style = \ thing -> thing
                                | otherwise = setLocalRdrEnv emptyLocalRdrEnv }
            ; (condecls', con_fvs) <- zap_lcl_env $ rnConDecls condecls
               -- No need to check for duplicate constructor decls
               -- since that is done by RnNames.extendGlobalRdrEnvRn

            ; let all_fvs = fvs1 `plusFV` fvs3 `plusFV`
                            con_fvs `plusFV` sig_fvs
            ; return ( HsDataDefn { dd_ND = new_or_data, dd_cType = cType
                                  , dd_ctxt = context', dd_kindSig = m_sig'
                                  , dd_cons = condecls'
                                  , dd_derivs = derivs' }
                     , all_fvs )
            }
      where
        h98_style = case condecls of  -- Note [Stupid theta]
                         L _ (ConDeclGADT {}) : _  -> False
                         _                         -> True

        rn_derivs (L loc ds)
          = do { deriv_strats_ok <- xoptM LangExt.DerivingStrategies
               ; failIfTc (lengthExceeds ds 1 && not deriv_strats_ok)
                   multipleDerivClausesErr
               ; (ds', fvs) <- mapFvRn (rnLHsDerivingClause deriv_strats_ok doc) ds
               ; return (L loc ds', fvs) }

    rnLHsDerivingClause :: Bool -> HsDocContext -> LHsDerivingClause GhcPs
                        -> RnM (LHsDerivingClause GhcRn, FreeVars)
    rnLHsDerivingClause deriv_strats_ok doc
                    (L loc (HsDerivingClause { deriv_clause_strategy = dcs
                                             , deriv_clause_tys = L loc' dct }))
      = do { failIfTc (isJust dcs && not deriv_strats_ok) $
               illegalDerivStrategyErr $ fmap unLoc dcs
           ; (dct', fvs) <- mapFvRn (rnHsSigType doc) dct
           ; return ( L loc (HsDerivingClause { deriv_clause_strategy = dcs
                                              , deriv_clause_tys = L loc' dct' })
                    , fvs ) }

    badGadtStupidTheta :: HsDocContext -> SDoc
    badGadtStupidTheta _
      = vcat [text "No context is allowed on a GADT-style data declaration",
              text "(You can put a context on each constructor, though.)"]

    illegalDerivStrategyErr :: Maybe DerivStrategy -> SDoc
    illegalDerivStrategyErr ds
      = vcat [ text "Illegal deriving strategy" <> colon <+> maybe empty ppr ds
             , text "Use DerivingStrategies to enable this extension" ]

    multipleDerivClausesErr :: SDoc
    multipleDerivClausesErr
      = vcat [ text "Illegal use of multiple, consecutive deriving clauses"
             , text "Use DerivingStrategies to allow this" ]

    rnFamDecl :: Maybe Name -- Just cls => this FamilyDecl is nested
                            --             inside an *class decl* for cls
                            --             used for associated types
              -> FamilyDecl GhcPs
              -> RnM (FamilyDecl GhcRn, FreeVars)
    rnFamDecl mb_cls (FamilyDecl { fdLName = tycon, fdTyVars = tyvars
                                 , fdFixity = fixity
                                 , fdInfo = info, fdResultSig = res_sig
                                 , fdInjectivityAnn = injectivity })
      = do { tycon' <- lookupLocatedTopBndrRn tycon
           ; kvs <- extractRdrKindSigVars res_sig
           ; ((tyvars', res_sig', injectivity'), fv1) <-
                bindHsQTyVars doc Nothing mb_cls kvs tyvars $ \ tyvars' _ ->
                do { let rn_sig = rnFamResultSig doc
                   ; (res_sig', fv_kind) <- wrapLocFstM rn_sig res_sig
                   ; injectivity' <- traverse (rnInjectivityAnn tyvars' res_sig')
                                              injectivity
                   ; return ( (tyvars', res_sig', injectivity') , fv_kind ) }
           ; (info', fv2) <- rn_info info
           ; return (FamilyDecl { fdLName = tycon', fdTyVars = tyvars'
                                , fdFixity = fixity
                                , fdInfo = info', fdResultSig = res_sig'
                                , fdInjectivityAnn = injectivity' }
                    , fv1 `plusFV` fv2) }
      where
         doc = TyFamilyCtx tycon

         ----------------------
         rn_info (ClosedTypeFamily (Just eqns))
           = do { (eqns', fvs) <- rnList (rnTyFamInstEqn Nothing) eqns
                                                        -- no class context,
                ; return (ClosedTypeFamily (Just eqns'), fvs) }
         rn_info (ClosedTypeFamily Nothing)
           = return (ClosedTypeFamily Nothing, emptyFVs)
         rn_info OpenTypeFamily = return (OpenTypeFamily, emptyFVs)
         rn_info DataFamily     = return (DataFamily, emptyFVs)

    rnFamResultSig :: HsDocContext
                   -> FamilyResultSig GhcPs
                   -> RnM (FamilyResultSig GhcRn, FreeVars)
    rnFamResultSig _ NoSig
       = return (NoSig, emptyFVs)
    rnFamResultSig doc (KindSig kind)
       = do { (rndKind, ftvs) <- rnLHsKind doc kind
            ;  return (KindSig rndKind, ftvs) }
    rnFamResultSig doc (TyVarSig tvbndr)
       = do { -- `TyVarSig` tells us that user named the result of a type family by
              -- writing `= tyvar` or `= (tyvar :: kind)`. In such case we want to
              -- be sure that the supplied result name is not identical to an
              -- already in-scope type variable from an enclosing class.
              --
              --  Example of disallowed declaration:
              --         class C a b where
              --            type F b = a | a -> b
              rdr_env <- getLocalRdrEnv
           ;  let resName = hsLTyVarName tvbndr
           ;  when (resName `elemLocalRdrEnv` rdr_env) $
              addErrAt (getLoc tvbndr) $
                         (hsep [ text "Type variable", quotes (ppr resName) <> comma
                               , text "naming a type family result,"
                               ] $$
                          text "shadows an already bound type variable")

           ; bindLHsTyVarBndr doc Nothing -- This might be a lie, but it's used for
                                          -- scoping checks that are irrelevant here
                              tvbndr $ \ tvbndr' ->
             return (TyVarSig tvbndr', unitFV (hsLTyVarName tvbndr')) }

    -- Note [Renaming injectivity annotation]
    -- ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
    --
    -- During renaming of injectivity annotation we have to make several checks to
    -- make sure that it is well-formed.  At the moment injectivity annotation
    -- consists of a single injectivity condition, so the terms "injectivity
    -- annotation" and "injectivity condition" might be used interchangeably.  See
    -- Note [Injectivity annotation] for a detailed discussion of currently allowed
    -- injectivity annotations.
    --
    -- Checking LHS is simple because the only type variable allowed on the LHS of
    -- injectivity condition is the variable naming the result in type family head.
    -- Example of disallowed annotation:
    --
    --     type family Foo a b = r | b -> a
    --
    -- Verifying RHS of injectivity consists of checking that:
    --
    --  1. only variables defined in type family head appear on the RHS (kind
    --     variables are also allowed).  Example of disallowed annotation:
    --
    --        type family Foo a = r | r -> b
    --
    --  2. for associated types the result variable does not shadow any of type
    --     class variables. Example of disallowed annotation:
    --
    --        class Foo a b where
    --           type F a = b | b -> a
    --
    -- Breaking any of these assumptions results in an error.

    -- | Rename injectivity annotation. Note that injectivity annotation is just the
    -- part after the "|".  Everything that appears before it is renamed in
    -- rnFamDecl.
    rnInjectivityAnn :: LHsQTyVars GhcRn           -- ^ Type variables declared in
                                                   --   type family head
                     -> LFamilyResultSig GhcRn     -- ^ Result signature
                     -> LInjectivityAnn GhcPs      -- ^ Injectivity annotation
                     -> RnM (LInjectivityAnn GhcRn)
    rnInjectivityAnn tvBndrs (L _ (TyVarSig resTv))
                     (L srcSpan (InjectivityAnn injFrom injTo))
     = do
       { (injDecl'@(L _ (InjectivityAnn injFrom' injTo')), noRnErrors)
              <- askNoErrs $
                 bindLocalNames [hsLTyVarName resTv] $
                 -- The return type variable scopes over the injectivity annotation
                 -- e.g.   type family F a = (r::*) | r -> a
                 do { injFrom' <- rnLTyVar injFrom
                    ; injTo'   <- mapM rnLTyVar injTo
                    ; return $ L srcSpan (InjectivityAnn injFrom' injTo') }

       ; let tvNames  = Set.fromList $ hsAllLTyVarNames tvBndrs
             resName  = hsLTyVarName resTv
             -- See Note [Renaming injectivity annotation]
             lhsValid = EQ == (stableNameCmp resName (unLoc injFrom'))
             rhsValid = Set.fromList (map unLoc injTo') `Set.difference` tvNames

       -- if renaming of type variables ended with errors (eg. there were
       -- not-in-scope variables) don't check the validity of injectivity
       -- annotation. This gives better error messages.
       ; when (noRnErrors && not lhsValid) $
            addErrAt (getLoc injFrom)
                  ( vcat [ text $ "Incorrect type variable on the LHS of "
                               ++ "injectivity condition"
                  , nest 5
                  ( vcat [ text "Expected :" <+> ppr resName
                         , text "Actual   :" <+> ppr injFrom ])])

       ; when (noRnErrors && not (Set.null rhsValid)) $
          do { let errorVars = Set.toList rhsValid
             ; addErrAt srcSpan $ ( hsep
                            [ text "Unknown type variable" <> plural errorVars
                            , text "on the RHS of injectivity condition:"
                            , interpp'SP errorVars ] ) }

       ; return injDecl' }

    -- We can only hit this case when the user writes injectivity annotation without
    -- naming the result:
    --
    --   type family F a | result -> a
    --   type family F a :: * | result -> a
    --
    -- So we rename injectivity annotation like we normally would except that
    -- this time we expect "result" to be reported not in scope by rnLTyVar.
    rnInjectivityAnn _ _ (L srcSpan (InjectivityAnn injFrom injTo)) =
       setSrcSpan srcSpan $ do
       (injDecl', _) <- askNoErrs $ do
         injFrom' <- rnLTyVar injFrom
         injTo'   <- mapM rnLTyVar injTo
         return $ L srcSpan (InjectivityAnn injFrom' injTo')
       return $ injDecl'

    {-
    Note [Stupid theta]
    ~~~~~~~~~~~~~~~~~~~
    Trac #3850 complains about a regression wrt 6.10 for
         data Show a => T a
    There is no reason not to allow the stupid theta if there are no data
    constructors.  It's still stupid, but does no harm, and I don't want
    to cause programs to break unnecessarily (notably HList).  So if there
    are no data constructors we allow h98_style = True
    -}

    {- *****************************************************
    *                                                      *
         Support code for type/data declarations
    *                                                      *
    ***************************************************** -}

    ---------------
    badAssocRhs :: [Name] -> RnM ()
    badAssocRhs ns
      = addErr (hang (text "The RHS of an associated type declaration mentions"
                      <+> text "out-of-scope variable" <> plural ns
                      <+> pprWithCommas (quotes . ppr) ns)
                   2 (text "All such variables must be bound on the LHS"))

    -----------------
    rnConDecls :: [LConDecl GhcPs] -> RnM ([LConDecl GhcRn], FreeVars)
    rnConDecls = mapFvRn (wrapLocFstM rnConDecl)

    rnConDecl :: ConDecl GhcPs -> RnM (ConDecl GhcRn, FreeVars)
    rnConDecl decl@(ConDeclH98 { con_name = name, con_qvars = qtvs
                               , con_cxt = mcxt, con_details = details
                               , con_doc = mb_doc })
      = do  { _ <- addLocM checkConName name
            ; new_name     <- lookupLocatedTopBndrRn name
            ; mb_doc'      <- rnMbLHsDoc mb_doc

            ; let doc      = ConDeclCtx [new_name]
                  qtvs'    = qtvs `orElse` mkHsQTvs []
                  body_kvs = []  -- Consider   data T a = forall (b::k). MkT (...)
                                 -- The 'k' will already be in scope from the
                                 -- bindHsQTyVars for the entire DataDecl
                                 -- So there can be no new body_kvs here
            ; bindHsQTyVars doc (Just $ inHsDocContext doc) Nothing body_kvs qtvs' $
              \new_tyvars _ -> do
            { (new_context, fvs1) <- case mcxt of
                                 Nothing   -> return (Nothing,emptyFVs)
                                 Just lcxt -> do { (lctx',fvs) <- rnContext doc lcxt
                                                 ; return (Just lctx',fvs) }
            ; (new_details, fvs2) <- rnConDeclDetails (unLoc new_name) doc details
            ; let (new_details',fvs3) = (new_details,emptyFVs)
            ; traceRn "rnConDecl" (ppr name <+> vcat
                 [ text "qtvs:" <+> ppr qtvs
                 , text "qtvs':" <+> ppr qtvs' ])
            ; let all_fvs = fvs1 `plusFV` fvs2 `plusFV` fvs3
                  new_tyvars' = case qtvs of
                    Nothing -> Nothing
                    Just _ -> Just new_tyvars
            ; return (decl { con_name = new_name, con_qvars = new_tyvars'
                           , con_cxt = new_context, con_details = new_details'
                           , con_doc = mb_doc' },
                      all_fvs) }}

    rnConDecl decl@(ConDeclGADT { con_names = names, con_type = ty
                                , con_doc = mb_doc })
      = do  { mapM_ (addLocM checkConName) names
            ; new_names    <- mapM lookupLocatedTopBndrRn names
            ; let doc = ConDeclCtx new_names
            ; mb_doc'      <- rnMbLHsDoc mb_doc

            ; (ty', fvs) <- rnHsSigType doc ty
            ; traceRn "rnConDecl" (ppr names <+> vcat
                 [ text "fvs:" <+> ppr fvs ])
            ; return (decl { con_names = new_names, con_type = ty'
                           , con_doc = mb_doc' },
                      fvs) }

    rnConDeclDetails
       :: Name
       -> HsDocContext
       -> HsConDetails (LHsType GhcPs) (Located [LConDeclField GhcPs])
       -> RnM (HsConDetails (LHsType GhcRn) (Located [LConDeclField GhcRn]),
               FreeVars)
    rnConDeclDetails _ doc (PrefixCon tys)
      = do { (new_tys, fvs) <- rnLHsTypes doc tys
           ; return (PrefixCon new_tys, fvs) }

    rnConDeclDetails _ doc (InfixCon ty1 ty2)
      = do { (new_ty1, fvs1) <- rnLHsType doc ty1
           ; (new_ty2, fvs2) <- rnLHsType doc ty2
           ; return (InfixCon new_ty1 new_ty2, fvs1 `plusFV` fvs2) }

    rnConDeclDetails con doc (RecCon (L l fields))
      = do  { fls <- lookupConstructorFields con
            ; (new_fields, fvs) <- rnConDeclFields doc fls fields
                    -- No need to check for duplicate fields
                    -- since that is done by RnNames.extendGlobalRdrEnvRn
            ; return (RecCon (L l new_fields), fvs) }

    -------------------------------------------------

    -- | Brings pattern synonym names and also pattern synonym selectors
    -- from record pattern synonyms into scope.
    extendPatSynEnv :: HsValBinds GhcPs -> MiniFixityEnv
                    -> ([Name] -> TcRnIf TcGblEnv TcLclEnv a) -> TcM a
    extendPatSynEnv val_decls local_fix_env thing = do {
         names_with_fls <- new_ps val_decls
       ; let pat_syn_bndrs = concat [ name: map flSelector fields
                                    | (name, fields) <- names_with_fls ]
       ; let avails = map avail pat_syn_bndrs
       ; (gbl_env, lcl_env) <- extendGlobalRdrEnvRn avails local_fix_env

       ; let field_env' = extendNameEnvList (tcg_field_env gbl_env) names_with_fls
             final_gbl_env = gbl_env { tcg_field_env = field_env' }
       ; setEnvs (final_gbl_env, lcl_env) (thing pat_syn_bndrs) }
      where
        new_ps :: HsValBinds GhcPs -> TcM [(Name, [FieldLabel])]
        new_ps (ValBindsIn binds _) = foldrBagM new_ps' [] binds
        new_ps _ = panic "new_ps"

        new_ps' :: LHsBindLR GhcPs GhcPs
                -> [(Name, [FieldLabel])]
                -> TcM [(Name, [FieldLabel])]
        new_ps' bind names
          | L bind_loc (PatSynBind (PSB { psb_id = L _ n
                                        , psb_args = RecCon as })) <- bind
          = do
              bnd_name <- newTopSrcBinder (L bind_loc n)
              let rnames = map recordPatSynSelectorId as
                  mkFieldOcc :: Located RdrName -> LFieldOcc GhcPs
                  mkFieldOcc (L l name) = L l (FieldOcc (L l name) PlaceHolder)
                  field_occs =  map mkFieldOcc rnames
              flds     <- mapM (newRecordSelector False [bnd_name]) field_occs
              return ((bnd_name, flds): names)
          | L bind_loc (PatSynBind (PSB { psb_id = L _ n})) <- bind
          = do
            bnd_name <- newTopSrcBinder (L bind_loc n)
            return ((bnd_name, []): names)
          | otherwise
          = return names

    {-
    *********************************************************
    *                                                      *
    \subsection{Support code to rename types}
    *                                                      *
    *********************************************************
    -}

    rnFds :: [Located (FunDep (Located RdrName))]
      -> RnM [Located (FunDep (Located Name))]
    rnFds fds
      = mapM (wrapLocM rn_fds) fds
      where
        rn_fds (tys1, tys2)
          = do { tys1' <- rnHsTyVars tys1
               ; tys2' <- rnHsTyVars tys2
               ; return (tys1', tys2') }

    rnHsTyVars :: [Located RdrName] -> RnM [Located Name]
    rnHsTyVars tvs  = mapM rnHsTyVar tvs

    rnHsTyVar :: Located RdrName -> RnM (Located Name)
    rnHsTyVar (L l tyvar) = do
      tyvar' <- lookupOccRn tyvar
      return (L l tyvar')

    {-
    *********************************************************
    *                                                      *
            findSplice
    *                                                      *
    *********************************************************

    This code marches down the declarations, looking for the first
    Template Haskell splice.  As it does so it
            a) groups the declarations into a HsGroup
            b) runs any top-level quasi-quotes
    -}

    findSplice :: [LHsDecl GhcPs]
               -> RnM (HsGroup GhcPs, Maybe (SpliceDecl GhcPs, [LHsDecl GhcPs]))
    findSplice ds = addl emptyRdrGroup ds

    addl :: HsGroup GhcPs -> [LHsDecl GhcPs]
         -> RnM (HsGroup GhcPs, Maybe (SpliceDecl GhcPs, [LHsDecl GhcPs]))
    -- This stuff reverses the declarations (again) but it doesn't matter
    addl gp []           = return (gp, Nothing)
    addl gp (L l d : ds) = add gp l d ds

    add :: HsGroup GhcPs -> SrcSpan -> HsDecl GhcPs -> [LHsDecl GhcPs]
        -> RnM (HsGroup GhcPs, Maybe (SpliceDecl GhcPs, [LHsDecl GhcPs]))

    -- #10047: Declaration QuasiQuoters are expanded immediately, without
    --         causing a group split
    add gp _ (SpliceD (SpliceDecl (L _ qq@HsQuasiQuote{}) _)) ds
      = do { (ds', _) <- rnTopSpliceDecls qq
           ; addl gp (ds' ++ ds)
           }

    add gp loc (SpliceD splice@(SpliceDecl _ flag)) ds
      = do { -- We've found a top-level splice.  If it is an *implicit* one
             -- (i.e. a naked top level expression)
             case flag of
               ExplicitSplice -> return ()
               ImplicitSplice -> do { th_on <- xoptM LangExt.TemplateHaskell
                                    ; unless th_on $ setSrcSpan loc $
                                      failWith badImplicitSplice }

           ; return (gp, Just (splice, ds)) }
      where
        badImplicitSplice = text "Parse error: module header, import declaration"
                         $$ text "or top-level declaration expected."

    -- Class declarations: pull out the fixity signatures to the top
    add gp@(HsGroup {hs_tyclds = ts, hs_fixds = fs}) l (TyClD d) ds
      | isClassDecl d
      = let fsigs = [ L l f | L l (FixSig f) <- tcdSigs d ] in
        addl (gp { hs_tyclds = add_tycld (L l d) ts, hs_fixds = fsigs ++ fs}) ds
      | otherwise
      = addl (gp { hs_tyclds = add_tycld (L l d) ts }) ds

    -- Signatures: fixity sigs go a different place than all others
    add gp@(HsGroup {hs_fixds = ts}) l (SigD (FixSig f)) ds
      = addl (gp {hs_fixds = L l f : ts}) ds
    add gp@(HsGroup {hs_valds = ts}) l (SigD d) ds
      = addl (gp {hs_valds = add_sig (L l d) ts}) ds

    -- Value declarations: use add_bind
    add gp@(HsGroup {hs_valds  = ts}) l (ValD d) ds
      = addl (gp { hs_valds = add_bind (L l d) ts }) ds

    -- Role annotations: added to the TyClGroup
    add gp@(HsGroup {hs_tyclds = ts}) l (RoleAnnotD d) ds
      = addl (gp { hs_tyclds = add_role_annot (L l d) ts }) ds

    -- NB instance declarations go into TyClGroups. We throw them into the first
    -- group, just as we do for the TyClD case. The renamer will go on to group
    -- and order them later.
    add gp@(HsGroup {hs_tyclds = ts})  l (InstD d) ds
      = addl (gp { hs_tyclds = add_instd (L l d) ts }) ds

    -- The rest are routine
    add gp@(HsGroup {hs_derivds = ts})  l (DerivD d) ds
      = addl (gp { hs_derivds = L l d : ts }) ds
    add gp@(HsGroup {hs_defds  = ts})  l (DefD d) ds
      = addl (gp { hs_defds = L l d : ts }) ds
    add gp@(HsGroup {hs_fords  = ts}) l (ForD d) ds
      = addl (gp { hs_fords = L l d : ts }) ds
    add gp@(HsGroup {hs_warnds  = ts})  l (WarningD d) ds
      = addl (gp { hs_warnds = L l d : ts }) ds
    add gp@(HsGroup {hs_annds  = ts}) l (AnnD d) ds
      = addl (gp { hs_annds = L l d : ts }) ds
    add gp@(HsGroup {hs_ruleds  = ts}) l (RuleD d) ds
      = addl (gp { hs_ruleds = L l d : ts }) ds
    add gp@(HsGroup {hs_vects  = ts}) l (VectD d) ds
      = addl (gp { hs_vects = L l d : ts }) ds
    add gp l (DocD d) ds
      = addl (gp { hs_docs = (L l d) : (hs_docs gp) })  ds

    add_tycld :: LTyClDecl a -> [TyClGroup a] -> [TyClGroup a]
    add_tycld d []       = [TyClGroup { group_tyclds = [d]
                                      , group_roles = []
                                      , group_instds = []
                                      }
                           ]
    add_tycld d (ds@(TyClGroup { group_tyclds = tyclds }):dss)
      = ds { group_tyclds = d : tyclds } : dss

    add_instd :: LInstDecl a -> [TyClGroup a] -> [TyClGroup a]
    add_instd d []       = [TyClGroup { group_tyclds = []
                                      , group_roles = []
                                      , group_instds = [d]
                                      }
                           ]
    add_instd d (ds@(TyClGroup { group_instds = instds }):dss)
      = ds { group_instds = d : instds } : dss

    add_role_annot :: LRoleAnnotDecl a -> [TyClGroup a] -> [TyClGroup a]
    add_role_annot d [] = [TyClGroup { group_tyclds = []
                                     , group_roles = [d]
                                     , group_instds = []
                                     }
                          ]
    add_role_annot d (tycls@(TyClGroup { group_roles = roles }) : rest)
      = tycls { group_roles = d : roles } : rest

    add_bind :: LHsBind a -> HsValBinds a -> HsValBinds a
    add_bind b (ValBindsIn bs sigs) = ValBindsIn (bs `snocBag` b) sigs
    add_bind _ (ValBindsOut {})     = panic "RdrHsSyn:add_bind"

    add_sig :: LSig a -> HsValBinds a -> HsValBinds a
    add_sig s (ValBindsIn bs sigs) = ValBindsIn bs (s:sigs)
    add_sig _ (ValBindsOut {})     = panic "RdrHsSyn:add_sig"