content: {-# LANGUAGE LambdaCase #-}
  {-# LANGUAGE TypeFamilies #-}
  
  {-
  (c) The GRASP/AQUA Project, Glasgow University, 1992-1998
  
  Renaming and dependency analysis of bindings
  
  This module does renaming and dependency analysis on value bindings in
  the abstract syntax.  It does {\em not} do cycle-checks on class or
  type-synonym declarations; those cannot be done at this stage because
  they may be affected by renaming (which isn't fully worked out yet).
  -}
  
  module GHC.Rename.Bind (
     -- Renaming top-level bindings
     rnTopBindsLHS, rnTopBindsLHSBoot, rnTopBindsBoot, rnValBindsRHS,
  
     -- Renaming local bindings
     rnLocalBindsAndThen, rnLocalValBindsLHS, rnLocalValBindsRHS,
  
     -- Other bindings
     rnMethodBinds, renameSigs, bindRuleBndrs,
     rnMatchGroup, rnGRHSs, rnGRHS, rnSrcFixityDecl,
     makeMiniFixityEnv, MiniFixityEnv, emptyMiniFixityEnv,
     HsSigCtxt(..),
  
     -- Utility for hs-boot files
     rejectBootDecls,
  
     -- Utility for COMPLETE pragmas
     localCompletePragmas
     ) where
  
  import GHC.Prelude
  
  import {-# SOURCE #-} GHC.Rename.Expr( rnExpr, rnLExpr, rnStmts )
  
  import GHC.Hs
  import GHC.Tc.Errors.Types
  import GHC.Tc.Utils.Monad
  import GHC.Rename.HsType
  import GHC.Rename.Pat
  import GHC.Rename.Names
  import GHC.Rename.Env
  import GHC.Rename.Fixity
  import GHC.Rename.Utils
  import GHC.Driver.DynFlags
  
  import GHC.Data.BooleanFormula ( bfTraverse )
  import GHC.Data.Graph.Directed ( SCC(..) )
  import GHC.Data.Maybe          ( orElse, mapMaybe )
  import GHC.Data.OrdList
  import GHC.Data.List.SetOps    ( findDupsEq )
  
  
  import GHC.Types.Error
  import GHC.Types.FieldLabel
  import GHC.Types.Name
  import GHC.Types.Name.Env
  import GHC.Types.Name.Set
  import GHC.Types.Name.Reader
  import GHC.Types.SourceFile
  import GHC.Types.SrcLoc as SrcLoc
  import GHC.Types.Basic         ( RecFlag(..), TypeOrKind(..) )
  
  import GHC.Types.CompleteMatch
  import GHC.Types.Hint ( SigLike(..) )
  import GHC.Types.Unique.DSet ( mkUniqDSet )
  import GHC.Types.Unique.Set
  
  import GHC.Unit.Module
  
  import GHC.Utils.Misc
  import GHC.Utils.Outputable
  import GHC.Utils.Panic
  
  import qualified GHC.LanguageExtensions as LangExt
  
  import Language.Haskell.Syntax.Basic (FieldLabelString(..))
  
  import Control.Monad
  import Data.List          ( partition )
  import Data.List.NonEmpty ( NonEmpty(..) )
  
  {-
  -- ToDo: Put the annotations into the monad, so that they arrive in the proper
  -- place and can be used when complaining.
  
  The code tree received by the function @rnBinds@ contains definitions
  in where-clauses which are all apparently mutually recursive, but which may
  not really depend upon each other. For example, in the top level program
  \begin{verbatim}
  f x = y where a = x
                y = x
  \end{verbatim}
  the definitions of @a@ and @y@ do not depend on each other at all.
  Unfortunately, the typechecker cannot always check such definitions.
  \footnote{Mycroft, A. 1984. Polymorphic type schemes and recursive
  definitions. In Proceedings of the International Symposium on Programming,
  Toulouse, pp. 217-39. LNCS 167. Springer Verlag.}
  However, the typechecker usually can check definitions in which only the
  strongly connected components have been collected into recursive bindings.
  This is precisely what the function @rnBinds@ does.
  
  ToDo: deal with case where a single monobinds binds the same variable
  twice.
  
  The vertag tag is a unique @Int@; the tags only need to be unique
  within one @MonoBinds@, so that unique-Int plumbing is done explicitly
  (heavy monad machinery not needed).
  
  
  ************************************************************************
  *                                                                      *
  * naming conventions                                                   *
  *                                                                      *
  ************************************************************************
  
  \subsection[name-conventions]{Name conventions}
  
  The basic algorithm involves walking over the tree and returning a tuple
  containing the new tree plus its free variables. Some functions, such
  as those walking polymorphic bindings (HsBinds) and qualifier lists in
  list comprehensions (@Quals@), return the variables bound in local
  environments. These are then used to calculate the free variables of the
  expression evaluated in these environments.
  
  Conventions for variable names are as follows:
  \begin{itemize}
  \item
  new code is given a prime to distinguish it from the old.
  
  \item
  a set of variables defined in @Exp@ is written @dvExp@
  
  \item
  a set of variables free in @Exp@ is written @fvExp@
  \end{itemize}
  
  ************************************************************************
  *                                                                      *
  * analysing polymorphic bindings (HsBindGroup, HsBind)
  *                                                                      *
  ************************************************************************
  
  \subsubsection[dep-HsBinds]{Polymorphic bindings}
  
  Non-recursive expressions are reconstructed without any changes at top
  level, although their component expressions may have to be altered.
  However, non-recursive expressions are currently not expected as
  \Haskell{} programs, and this code should not be executed.
  
  Monomorphic bindings contain information that is returned in a tuple
  (a @FlatMonoBinds@) containing:
  
  \begin{enumerate}
  \item
  a unique @Int@ that serves as the ``vertex tag'' for this binding.
  
  \item
  the name of a function or the names in a pattern. These are a set
  referred to as @dvLhs@, the defined variables of the left hand side.
  
  \item
  the free variables of the body. These are referred to as @fvBody@.
  
  \item
  the definition's actual code. This is referred to as just @code@.
  \end{enumerate}
  
  The function @nonRecDvFv@ returns two sets of variables. The first is
  the set of variables defined in the set of monomorphic bindings, while the
  second is the set of free variables in those bindings.
  
  The set of variables defined in a non-recursive binding is just the
  union of all of them, as @union@ removes duplicates. However, the
  free variables in each successive set of cumulative bindings is the
  union of those in the previous set plus those of the newest binding after
  the defined variables of the previous set have been removed.
  
  @rnMethodBinds@ deals only with the declarations in class and
  instance declarations.  It expects only to see @FunMonoBind@s, and
  it expects the global environment to contain bindings for the binders
  (which are all class operations).
  
  ************************************************************************
  *                                                                      *
  \subsubsection{ Top-level bindings}
  *                                                                      *
  ************************************************************************
  -}
  
  -- for top-level bindings, we need to make top-level names,
  -- so we have a different entry point than for local bindings
  rnTopBindsLHS :: MiniFixityEnv
                -> HsValBinds GhcPs
                -> RnM (HsValBindsLR GhcRn GhcPs)
  rnTopBindsLHS fix_env binds
    = rnValBindsLHS (topRecNameMaker fix_env) binds
  
  -- Ensure that a hs-boot file has no top-level bindings.
  rnTopBindsLHSBoot :: MiniFixityEnv
                    -> HsValBinds GhcPs
                    -> RnM (HsValBindsLR GhcRn GhcPs)
  rnTopBindsLHSBoot fix_env binds
    = do  { topBinds <- rnTopBindsLHS fix_env binds
          ; case topBinds of
              ValBinds x mbinds sigs ->
                do  { rejectBootDecls HsBoot BootBindsPs mbinds
                    ; pure (ValBinds x [] sigs) }
              _ -> pprPanic "rnTopBindsLHSBoot" (ppr topBinds) }
  
  rejectBootDecls :: HsBootOrSig
                  -> (NonEmpty (LocatedA decl) -> BadBootDecls)
                  -> [LocatedA decl]
                  -> TcM ()
  rejectBootDecls _ _ [] = return ()
  rejectBootDecls hsc_src what (decl@(L loc _) : decls)
    = addErrAt (locA loc)
    $ TcRnIllegalHsBootOrSigDecl hsc_src
        (what $ decl :| decls)
  
  rnTopBindsBoot :: NameSet -> HsValBindsLR GhcRn GhcPs
                 -> RnM (HsValBinds GhcRn, DefUses)
  -- A hs-boot file has no bindings.
  -- Return a single HsBindGroup with empty binds and renamed signatures
  rnTopBindsBoot bound_names (ValBinds _ _ sigs)
    = do  { (sigs', fvs) <- renameSigs (HsBootCtxt bound_names) sigs
          ; return (XValBindsLR (NValBinds [] sigs'), usesOnly fvs) }
  rnTopBindsBoot _ b = pprPanic "rnTopBindsBoot" (ppr b)
  
  {-
  *********************************************************
  *                                                      *
                  HsLocalBinds
  *                                                      *
  *********************************************************
  -}
  
  rnLocalBindsAndThen :: HsLocalBinds GhcPs
                     -> (HsLocalBinds GhcRn -> FreeVars -> RnM (result, FreeVars))
                     -> RnM (result, FreeVars)
  -- This version (a) assumes that the binding vars are *not* already in scope
  --               (b) removes the binders from the free vars of the thing inside
  -- The parser doesn't produce ThenBinds
  rnLocalBindsAndThen (EmptyLocalBinds x) thing_inside =
    thing_inside (EmptyLocalBinds x) emptyNameSet
  
  rnLocalBindsAndThen (HsValBinds x val_binds) thing_inside
    = rnLocalValBindsAndThen val_binds $ \ val_binds' ->
        thing_inside (HsValBinds x val_binds')
  
  rnLocalBindsAndThen (HsIPBinds x binds) thing_inside = do
      (binds',fv_binds) <- rnIPBinds binds
      (thing, fvs_thing) <- thing_inside (HsIPBinds x binds') fv_binds
      return (thing, fvs_thing `plusFV` fv_binds)
  
  rnIPBinds :: HsIPBinds GhcPs -> RnM (HsIPBinds GhcRn, FreeVars)
  rnIPBinds (IPBinds _ ip_binds ) = do
      (ip_binds', fvs_s) <- mapAndUnzipM (wrapLocFstMA rnIPBind) ip_binds
      return (IPBinds noExtField ip_binds', plusFVs fvs_s)
  
  rnIPBind :: IPBind GhcPs -> RnM (IPBind GhcRn, FreeVars)
  rnIPBind (IPBind _ n expr) = do
      (expr',fvExpr) <- rnLExpr expr
      return (IPBind noExtField n expr', fvExpr)
  
  {-
  ************************************************************************
  *                                                                      *
                  ValBinds
  *                                                                      *
  ************************************************************************
  -}
  
  -- Renaming local binding groups
  -- Does duplicate/shadow check
  rnLocalValBindsLHS :: MiniFixityEnv
                     -> HsValBinds GhcPs
                     -> RnM ([Name], HsValBindsLR GhcRn GhcPs)
  rnLocalValBindsLHS fix_env binds
    = do { binds' <- rnValBindsLHS (localRecNameMaker fix_env) binds
  
           -- Check for duplicates and shadowing
           -- Must do this *after* renaming the patterns
           -- See Note [Collect binders only after renaming] in GHC.Hs.Utils
  
           -- We need to check for dups here because we
           -- don't don't bind all of the variables from the ValBinds at once
           -- with bindLocatedLocals any more.
           --
           -- Note that we don't want to do this at the top level, since
           -- sorting out duplicates and shadowing there happens elsewhere.
           -- The behavior is even different. For example,
           --   import A(f)
           --   f = ...
           -- should not produce a shadowing warning (but it will produce
           -- an ambiguity warning if you use f), but
           --   import A(f)
           --   g = let f = ... in f
           -- should.
         ; let bound_names = collectHsValBinders CollNoDictBinders binds'
               -- There should be only Ids, but if there are any bogus
               -- pattern synonyms, we'll collect them anyway, so that
               -- we don't generate subsequent out-of-scope messages
         ; envs <- getRdrEnvs
         ; checkDupAndShadowedNames envs bound_names
  
         ; return (bound_names, binds') }
  
  -- renames the left-hand sides
  -- generic version used both at the top level and for local binds
  -- does some error checking, but not what gets done elsewhere at the top level
  rnValBindsLHS :: NameMaker
                -> HsValBinds GhcPs
                -> RnM (HsValBindsLR GhcRn GhcPs)
  rnValBindsLHS topP (ValBinds x mbinds sigs)
    = do { mbinds' <- mapM (wrapLocMA (rnBindLHS topP doc)) mbinds
         ; return $ ValBinds x mbinds' sigs }
    where
      bndrs = collectHsBindsBinders CollNoDictBinders mbinds
      doc   = text "In the binding group for:" <+> pprWithCommas ppr bndrs
  
  rnValBindsLHS _ b = pprPanic "rnValBindsLHSFromDoc" (ppr b)
  
  -- General version used both from the top-level and for local things
  -- Assumes the LHS vars are in scope
  --
  -- Does not bind the local fixity declarations
  rnValBindsRHS :: HsSigCtxt
                -> HsValBindsLR GhcRn GhcPs
                -> RnM (HsValBinds GhcRn, DefUses)
  
  rnValBindsRHS ctxt (ValBinds _ mbinds sigs)
    = do { (sigs', sig_fvs) <- renameSigs ctxt sigs
  
         -- Update the TcGblEnv with renamed COMPLETE pragmas from the current
         -- module, for pattern irrefutability checking in do notation.
         ; let localCompletePrags = localCompletePragmas sigs'
         ; updGblEnv (\gblEnv -> gblEnv { tcg_complete_matches = tcg_complete_matches gblEnv ++ localCompletePrags
                                        , tcg_complete_match_env = tcg_complete_match_env gblEnv ++ localCompletePrags }) $
      do { binds_w_dus <- mapM (rnLBind (mkScopedTvFn sigs')) mbinds
         ; let !(anal_binds, anal_dus) = depAnalBinds binds_w_dus
  
         ; let patsyn_fvs = foldr (unionNameSet . psb_ext) emptyNameSet $
                            getPatSynBinds anal_binds
                  -- The uses in binds_w_dus for PatSynBinds do not include
                  -- variables used in the patsyn builders; see
                  -- Note [Pattern synonym builders don't yield dependencies]
                  -- But psb_fvs /does/ include those builder fvs.  So we
                  -- add them back in here to avoid bogus warnings about
                  -- unused variables (#12548)
  
               valbind'_dus = anal_dus `plusDU` usesOnly sig_fvs
                                       `plusDU` usesOnly patsyn_fvs
                              -- Put the sig uses *after* the bindings
                              -- so that the binders are removed from
                              -- the uses in the sigs
  
          ; return (XValBindsLR (NValBinds anal_binds sigs'), valbind'_dus) } }
  
  rnValBindsRHS _ b = pprPanic "rnValBindsRHS" (ppr b)
  
  -- Wrapper for local binds
  --
  -- The *client* of this function is responsible for checking for unused binders;
  -- it doesn't (and can't: we don't have the thing inside the binds) happen here
  --
  -- The client is also responsible for bringing the fixities into scope
  rnLocalValBindsRHS :: NameSet  -- names bound by the LHSes
                     -> HsValBindsLR GhcRn GhcPs
                     -> RnM (HsValBinds GhcRn, DefUses)
  rnLocalValBindsRHS bound_names binds
    = rnValBindsRHS (LocalBindCtxt bound_names) binds
  
  -- for local binds
  -- wrapper that does both the left- and right-hand sides
  --
  -- here there are no local fixity decls passed in;
  -- the local fixity decls come from the ValBinds sigs
  rnLocalValBindsAndThen
    :: HsValBinds GhcPs
    -> (HsValBinds GhcRn -> FreeVars -> RnM (result, FreeVars))
    -> RnM (result, FreeVars)
  rnLocalValBindsAndThen binds@(ValBinds _ _ sigs) thing_inside
   = do   {     -- (A) Create the local fixity environment
            new_fixities <- makeMiniFixityEnv [ L loc sig
                                              | L loc (FixSig _ sig) <- sigs]
  
                -- (B) Rename the LHSes
          ; (bound_names, new_lhs) <- rnLocalValBindsLHS new_fixities binds
  
                --     ...and bring them (and their fixities) into scope
          ; bindLocalNamesFV bound_names              $
            addLocalFixities new_fixities bound_names $ do
  
          {      -- (C) Do the RHS and thing inside
            (binds', dus) <- rnLocalValBindsRHS (mkNameSet bound_names) new_lhs
          ; (result, result_fvs) <- thing_inside binds' (allUses dus)
  
                  -- Report unused bindings based on the (accurate)
                  -- findUses.  E.g.
                  --      let x = x in 3
                  -- should report 'x' unused
          ; let real_uses = findUses dus result_fvs
                -- Insert fake uses for variables introduced implicitly by
                -- wildcards (#4404)
                rec_uses = hsValBindsImplicits binds'
                implicit_uses = mkNameSet $ concatMap (concatMap implFlBndr_binders . snd)
                                          $ rec_uses
          ; mapM_ (\(loc, ns) ->
                      checkUnusedRecordWildcard loc real_uses (Just ns))
                  rec_uses
          ; warnUnusedLocalBinds bound_names
                                        (real_uses `unionNameSet` implicit_uses)
  
          ; let
              -- The variables "used" in the val binds are:
              --   (1) the uses of the binds (allUses)
              --   (2) the FVs of the thing-inside
              all_uses = allUses dus `plusFV` result_fvs
                  -- Note [Unused binding hack]
                  -- ~~~~~~~~~~~~~~~~~~~~~~~~~~
                  -- Note that *in contrast* to the above reporting of
                  -- unused bindings, (1) above uses duUses to return *all*
                  -- the uses, even if the binding is unused.  Otherwise consider:
                  --      x = 3
                  --      y = let p = x in 'x'    -- NB: p not used
                  -- If we don't "see" the dependency of 'y' on 'x', we may put the
                  -- bindings in the wrong order, and the type checker will complain
                  -- that x isn't in scope
                  --
                  -- But note that this means we won't report 'x' as unused,
                  -- whereas we would if we had { x = 3; p = x; y = 'x' }
  
          ; return (result, all_uses) }}
                  -- The bound names are pruned out of all_uses
                  -- by the bindLocalNamesFV call above
  
  rnLocalValBindsAndThen bs _ = pprPanic "rnLocalValBindsAndThen" (ppr bs)
  
  
  ---------------------
  
  -- renaming a single bind
  
  rnBindLHS :: NameMaker
            -> SDoc
            -> HsBind GhcPs
            -- returns the renamed left-hand side,
            -- and the FreeVars *of the LHS*
            -- (i.e., any free variables of the pattern)
            -> RnM (HsBindLR GhcRn GhcPs)
  
  rnBindLHS name_maker _ bind@(PatBind { pat_lhs = pat, pat_mult = pat_mult })
    = do
        -- we don't actually use the FV processing of rnPatsAndThen here
        (pat',pat'_fvs) <- rnBindPat name_maker pat
        (pat_mult', mult'_fvs) <- rnHsMultAnnWith (rnLHsType PatCtx) pat_mult
        return (bind { pat_lhs = pat', pat_ext = pat'_fvs `plusFV` mult'_fvs, pat_mult = pat_mult' })
                  -- We temporarily store the pat's FVs in bind_fvs;
                  -- gets updated to the FVs of the whole bind
                  -- when doing the RHS below
  
  rnBindLHS name_maker _ bind@(FunBind { fun_id = rdr_name })
    = do { name <- applyNameMaker name_maker rdr_name
         ; return (bind { fun_id = name
                        , fun_ext = noExtField }) }
  
  rnBindLHS name_maker _ (PatSynBind x psb@PSB{ psb_id = rdrname })
    | isTopRecNameMaker name_maker
    = do { addLocM checkConName rdrname
         ; name <-
             lookupLocatedTopBndrRnN WL_ConLike rdrname -- Should be in scope already
         ; return (PatSynBind x psb{ psb_ext = noAnn, psb_id = name }) }
  
    | otherwise  -- Pattern synonym, not at top level
    = do { addErr localPatternSynonymErr  -- Complain, but make up a fake
                                          -- name so that we can carry on
         ; name <- applyNameMaker name_maker rdrname
         ; return (PatSynBind x psb{ psb_ext = noAnn, psb_id = name }) }
    where
      localPatternSynonymErr :: TcRnMessage
      localPatternSynonymErr = TcRnIllegalPatSynDecl rdrname
  
  rnBindLHS _ _ b = pprPanic "rnBindHS" (ppr b)
  
  rnLBind :: (Name -> [Name])      -- Signature tyvar function
          -> LHsBindLR GhcRn GhcPs
          -> RnM (LHsBind GhcRn, [Name], Uses)
  rnLBind sig_fn (L loc bind)
    = setSrcSpanA loc $
      do { (bind', bndrs, dus) <- rnBind sig_fn bind
         ; return (L loc bind', bndrs, dus) }
  
  -- assumes the left-hands-side vars are in scope
  rnBind :: (Name -> [Name])        -- Signature tyvar function
         -> HsBindLR GhcRn GhcPs
         -> RnM (HsBind GhcRn, [Name], Uses)
  rnBind _ bind@(PatBind { pat_lhs = pat
                         , pat_rhs = grhss
                                     -- pat fvs were stored in bind_fvs
                                     -- after processing the LHS
                         , pat_ext = pat_fvs })
    = do  { mod <- getModule
          ; (grhss', rhs_fvs) <- rnGRHSs PatBindRhs rnLExpr grhss
  
                  -- No scoped type variables for pattern bindings
          ; let all_fvs = pat_fvs `plusFV` rhs_fvs
                fvs'    = filterNameSet (nameIsLocalOrFrom mod) all_fvs
                  -- Keep locally-defined Names
                  -- As well as dependency analysis, we need these for the
                  -- MonoLocalBinds test in GHC.Tc.Gen.Bind.decideGeneralisationPlan
                bndrs = collectPatBinders CollNoDictBinders pat
                bind' = bind { pat_rhs  = grhss'
                             , pat_ext = fvs' }
  
          -- Warn if the pattern binds no variables
          -- See Note [Pattern bindings that bind no variables]
          ; whenWOptM Opt_WarnUnusedPatternBinds $
            when (null bndrs && not (isOkNoBindPattern pat)) $
            addTcRnDiagnostic (TcRnUnusedPatternBinds bind')
  
          ; fvs' `seq` -- See Note [Free-variable space leak]
            return (bind', bndrs, all_fvs) }
  
  rnBind sig_fn bind@(FunBind { fun_id = name
                              , fun_matches = matches })
         -- invariant: no free vars here when it's a FunBind
    = do  { let plain_name = unLoc name
  
          ; (matches', rhs_fvs) <- bindSigTyVarsFV (sig_fn plain_name) $
                                  -- bindSigTyVars tests for LangExt.ScopedTyVars
                                   rnMatchGroup (mkPrefixFunRhs name noAnn)
                                                rnLExpr matches
          ; let is_infix = isInfixFunBind bind
          ; when is_infix $ checkPrecMatch plain_name matches'
  
          ; mod <- getModule
          ; let fvs' = filterNameSet (nameIsLocalOrFrom mod) rhs_fvs
                  -- Keep locally-defined Names
                  -- As well as dependency analysis, we need these for the
                  -- MonoLocalBinds test in GHC.Tc.Gen.Bind.decideGeneralisationPlan
  
          ; fvs' `seq` -- See Note [Free-variable space leak]
            return (bind { fun_matches = matches'
                         , fun_ext     = fvs' },
                    [plain_name], rhs_fvs)
        }
  
  rnBind sig_fn (PatSynBind x bind)
    = do  { (bind', name, fvs) <- rnPatSynBind sig_fn bind
          ; return (PatSynBind x bind', name, fvs) }
  
  rnBind _ (VarBind { var_ext = x }) = dataConCantHappen x
  
   -- See Note [Pattern bindings that bind no variables]
  isOkNoBindPattern :: LPat GhcRn -> Bool
  isOkNoBindPattern (L _ pat) =
    case pat of
      WildPat{}       -> True -- Exception (1)
      BangPat {}      -> True -- Exception (2) #9127, #13646
      p -> patternContainsSplice p -- Exception (3)
  
      where
        lpatternContainsSplice :: LPat GhcRn -> Bool
        lpatternContainsSplice (L _ p) = patternContainsSplice p
        patternContainsSplice :: Pat GhcRn -> Bool
        patternContainsSplice p =
          case p of
            -- A top-level splice has been evaluated by this point, so we know the pattern it is evaluated to
            SplicePat (HsUntypedSpliceTop _ p) _ -> patternContainsSplice p
            -- A nested splice isn't evaluated so we can't guess what it will expand to
            SplicePat (HsUntypedSpliceNested {}) _ -> True
            -- The base cases
            VarPat {} -> False
            WildPat {} -> False
            LitPat {} -> False
            NPat {} -> False
            NPlusKPat {} -> False
            -- Recursive cases
            BangPat _ lp -> lpatternContainsSplice lp
            LazyPat _ lp -> lpatternContainsSplice lp
            AsPat _ _ lp  -> lpatternContainsSplice lp
            ParPat _ lp -> lpatternContainsSplice lp
            ViewPat _ _ lp -> lpatternContainsSplice lp
            OrPat _ lps -> any lpatternContainsSplice lps
            SigPat _ lp _  -> lpatternContainsSplice lp
            ListPat _ lps  -> any lpatternContainsSplice lps
            TuplePat _ lps _ -> any lpatternContainsSplice lps
            SumPat _ lp _ _ -> lpatternContainsSplice lp
            ConPat _ _ cpd  -> any lpatternContainsSplice (hsConPatArgs cpd)
            XPat (HsPatExpanded _orig new) -> patternContainsSplice new
  
            -- The behavior of this case is unimportant, as GHC will throw an error shortly
            -- after reaching this case for other reasons (see TcRnIllegalTypePattern).
            EmbTyPat{} -> True
  
            InvisPat{} -> True
  
  {- Note [Pattern bindings that bind no variables]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  Generally, we want to warn about pattern bindings like
    Just _ = e
  because they don't do anything!  But we have three exceptions:
  
  (1) A wildcard pattern
         _ = rhs
    which (a) is not that different from  _v = rhs
          (b) is sometimes used to give a type sig for,
              or an occurrence of, a variable on the RHS
  
  (2) A strict pattern binding; that is, one with an outermost bang
       !Just _ = e
    This can fail, so unlike the lazy variant, it is not a no-op.
    Moreover, #13646 argues that even for single constructor
    types, you might want to write the constructor.  See also #9127.
  
  (3) A splice pattern
        $(th-lhs) = rhs
     It is impossible to determine whether or not th-lhs really
     binds any variable. You have to recurse all the way into the pattern to check
     it doesn't contain any splices like this. See #22057.
  
  Note [Free-variable space leak]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  We have
      fvs' = trim fvs
  and we seq fvs' before turning it as part of a record.
  
  The reason is that trim is sometimes something like
      \xs -> intersectNameSet (mkNameSet bound_names) xs
  and we don't want to retain the list bound_names. This showed up in
  ticket #1136.
  -}
  
  {- *********************************************************************
  *                                                                      *
            Dependency analysis and other support functions
  *                                                                      *
  ********************************************************************* -}
  
  depAnalBinds :: [(LHsBind GhcRn, [Name], Uses)]
               -> ([(RecFlag, LHsBinds GhcRn)], DefUses)
  -- Dependency analysis; this is important so that
  -- unused-binding reporting is accurate
  depAnalBinds binds_w_dus
    = (map get_binds sccs, toOL $ map get_du sccs)
    where
      sccs = depAnal (\(_, defs, _) -> defs)
                     (\(_, _, uses) -> nonDetEltsUniqSet uses)
                     -- It's OK to use nonDetEltsUniqSet here as explained in
                     -- Note [depAnal determinism] in GHC.Types.Name.Env.
                     binds_w_dus
  
      get_binds (AcyclicSCC (bind, _, _)) = (NonRecursive, [bind])
      get_binds (CyclicSCC  binds_w_dus)  = (Recursive, [b | (b,_,_) <- binds_w_dus])
  
      get_du (AcyclicSCC (_, bndrs, uses)) = (Just (mkNameSet bndrs), uses)
      get_du (CyclicSCC  binds_w_dus)      = (Just defs, uses)
          where
            defs = mkNameSet [b | (_,bs,_) <- binds_w_dus, b <- bs]
            uses = unionNameSets [u | (_,_,u) <- binds_w_dus]
  
  ---------------------
  -- Bind the top-level forall'd type variables in the sigs.
  -- E.g  f :: forall a. a -> a
  --      f = rhs
  --      The 'a' scopes over the rhs
  --
  -- NB: there'll usually be just one (for a function binding)
  --     but if there are many, one may shadow the rest; too bad!
  --      e.g  x :: forall a. [a] -> [a]
  --           y :: forall a. [(a,a)] -> a
  --           (x,y) = e
  --      In e, 'a' will be in scope, and it'll be the one from 'y'!
  
  mkScopedTvFn :: [LSig GhcRn] -> (Name -> [Name])
  -- Return a lookup function that maps an Id Name to the names
  -- of the type variables that should scope over its body.
  mkScopedTvFn sigs = \n -> lookupNameEnv env n `orElse` []
    where
      env = mkHsSigEnv get_scoped_tvs sigs
  
      get_scoped_tvs :: LSig GhcRn -> Maybe ([LocatedN Name], [Name])
      -- Returns (binders, scoped tvs for those binders)
      get_scoped_tvs (L _ (ClassOpSig _ _ names sig_ty))
        = Just (names, hsScopedTvs sig_ty)
      get_scoped_tvs (L _ (TypeSig _ names sig_ty))
        = Just (names, hsWcScopedTvs sig_ty)
      get_scoped_tvs (L _ (PatSynSig _ names sig_ty))
        = Just (names, hsScopedTvs sig_ty)
      get_scoped_tvs _ = Nothing
  
  -- Process the fixity declarations, making a FastString -> (Located Fixity) map
  -- (We keep the location around for reporting duplicate fixity declarations.)
  --
  -- Checks for duplicates, but not that only locally defined things are fixed.
  -- Note: for local fixity declarations, duplicates would also be checked in
  --       check_sigs below.  But we also use this function at the top level.
  
  makeMiniFixityEnv :: [LFixitySig GhcPs] -> RnM MiniFixityEnv
  
  makeMiniFixityEnv decls = foldlM add_one_sig emptyMiniFixityEnv decls
   where
     add_one_sig :: MiniFixityEnv -> LFixitySig GhcPs -> RnM MiniFixityEnv
     add_one_sig env (L loc (FixitySig ns_spec names fixity)) =
       foldlM add_one env [ (locA loc,locA name_loc,name,fixity, ns_spec)
                          | L name_loc name <- names ]
  
     add_one env (loc, name_loc, name, fixity, ns_spec) = do
       { -- this fixity decl is a duplicate iff
         -- the ReaderName's OccName's FastString is already in the env
         -- (we only need to check the local fix_env because
         --  definitions of non-local will be caught elsewhere)
         let { fs = occNameFS (rdrNameOcc name)
             ; fix_item = L loc fixity};
  
         case search_for_dups ns_spec env fs of
           Nothing -> return $ extend_mini_fixity_env ns_spec env fs fix_item
           Just (L loc' _) -> do
             { setSrcSpan loc $
               addErrAt name_loc (TcRnMultipleFixityDecls loc' name)
             ; return env}
       }
     search_for_dups ns_spec MFE{mfe_data_level_names, mfe_type_level_names} fs
      = case ns_spec of
        NoNamespaceSpecifier -> case lookupFsEnv mfe_data_level_names fs of
          -- We only need to find a single duplicate to emit an error about
          -- multiple fixity decls. Therefore, if we find a duplicate in the
          -- term-level namespace, then there is no need to look in the type-level namespace.
          Nothing -> lookupFsEnv mfe_type_level_names fs
          just_dup -> just_dup
        TypeNamespaceSpecifier{} -> lookupFsEnv mfe_type_level_names fs
        DataNamespaceSpecifier{} -> lookupFsEnv mfe_data_level_names fs
  
     extend_mini_fixity_env ns_spec env@MFE{mfe_data_level_names, mfe_type_level_names} fs fix_item
      = case ns_spec of
        NoNamespaceSpecifier     -> MFE { mfe_data_level_names = (extendFsEnv mfe_data_level_names fs fix_item)
                                        , mfe_type_level_names = (extendFsEnv mfe_type_level_names fs fix_item)}
  
        TypeNamespaceSpecifier{} -> env { mfe_type_level_names = (extendFsEnv mfe_type_level_names fs fix_item)}
  
        DataNamespaceSpecifier{} -> env { mfe_data_level_names = (extendFsEnv mfe_data_level_names fs fix_item)}
  
  {- *********************************************************************
  *                                                                      *
                  Pattern synonym bindings
  *                                                                      *
  ********************************************************************* -}
  
  rnPatSynBind :: (Name -> [Name])           -- Signature tyvar function
               -> PatSynBind GhcRn GhcPs
               -> RnM (PatSynBind GhcRn GhcRn, [Name], Uses)
  rnPatSynBind sig_fn bind@(PSB { psb_id = L l name
                                , psb_args = details
                                , psb_def = pat
                                , psb_dir = dir })
         -- invariant: no free vars here when it's a FunBind
    = do  { pattern_synonym_ok <- xoptM LangExt.PatternSynonyms
          ; unless pattern_synonym_ok (addErr TcRnIllegalPatternSynonymDecl)
          ; let scoped_tvs = sig_fn name
  
          ; ((pat', details'), fvs1) <- bindSigTyVarsFV scoped_tvs $
                                        rnPat PatSyn pat $ \pat' ->
           -- We check the 'RdrName's instead of the 'Name's
           -- so that the binding locations are reported
           -- from the left-hand side
              case details of
                 PrefixCon vars ->
                     do { checkDupRdrNames vars
                        ; names <- mapM lookupPatSynBndr vars
                        ; return ( (pat', PrefixCon names)
                                 , mkFVs (map unLoc names)) }
                 InfixCon var1 var2 ->
                     do { checkDupRdrNames [var1, var2]
                        ; name1 <- lookupPatSynBndr var1
                        ; name2 <- lookupPatSynBndr var2
                        -- ; checkPrecMatch -- TODO
                        ; return ( (pat', InfixCon name1 name2)
                                 , mkFVs (map unLoc [name1, name2])) }
                 RecCon vars ->
                     do { checkDupRdrNames (map (foLabel . recordPatSynField) vars)
                        ; fls <- lookupConstructorFields $ noUserRdr name
                        ; let fld_env = mkFsEnv [ (field_label $ flLabel fl, fl) | fl <- fls ]
                        ; let rnRecordPatSynField
                                (RecordPatSynField { recordPatSynField  = visible
                                                   , recordPatSynPatVar = hidden })
                                = do { let visible' = lookupField fld_env visible
                                     ; hidden'  <- lookupPatSynBndr hidden
                                     ; return $ RecordPatSynField { recordPatSynField  = visible'
                                                                  , recordPatSynPatVar = hidden' } }
                        ; names <- mapM rnRecordPatSynField  vars
                        ; return ( (pat', RecCon names)
                                 , mkFVs (map (unLoc . recordPatSynPatVar) names)) }
  
          ; (dir', fvs2) <- case dir of
              Unidirectional -> return (Unidirectional, emptyFVs)
              ImplicitBidirectional -> return (ImplicitBidirectional, emptyFVs)
              ExplicitBidirectional mg ->
                  do { (mg', fvs) <- bindSigTyVarsFV scoped_tvs $
                                     rnMatchGroup (mkPrefixFunRhs (L l name) noAnn)
                                                  rnLExpr mg
                     ; return (ExplicitBidirectional mg', fvs) }
  
          ; mod <- getModule
          ; let fvs = fvs1 `plusFV` fvs2
                fvs' = filterNameSet (nameIsLocalOrFrom mod) fvs
                  -- Keep locally-defined Names
                  -- As well as dependency analysis, we need these for the
                  -- MonoLocalBinds test in GHC.Tc.Gen.Bind.decideGeneralisationPlan
  
                bind' = bind{ psb_args = details'
                            , psb_def = pat'
                            , psb_dir = dir'
                            , psb_ext = fvs' }
                selector_names = case details' of
                                   RecCon names ->
                                        map (unLoc . foLabel . recordPatSynField) names
                                   _ -> []
  
          ; fvs' `seq` -- See Note [Free-variable space leak]
            return (bind', name : selector_names , fvs1)
            -- Why fvs1?  See Note [Pattern synonym builders don't yield dependencies]
        }
    where
      -- See Note [Renaming pattern synonym variables]
      lookupPatSynBndr = wrapLocMA lookupLocalOccRn
  
  
  {-
  Note [Renaming pattern synonym variables]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  
  We rename pattern synonym declarations backwards to normal to reuse
  the logic already implemented for renaming patterns.
  
  We first rename the RHS of a declaration which brings into
  scope the variables bound by the pattern (as they would be
  in normal function definitions). We then lookup the variables
  which we want to bind in this local environment.
  
  It is crucial that we then only lookup in the *local* environment which
  only contains the variables brought into scope by the pattern and nothing
  else. Amazingly no-one encountered this bug for 3 GHC versions but
  it was possible to define a pattern synonym which referenced global
  identifiers and worked correctly.
  
  ```
  x = 5
  
  pattern P :: Int -> ()
  pattern P x <- _
  
  f (P x) = x
  
  > f () = 5
  ```
  
  See #13470 for the original report.
  
  Note [Pattern synonym builders don't yield dependencies]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  When renaming a pattern synonym that has an explicit builder,
  references in the builder definition should not be used when
  calculating dependencies. For example, consider the following pattern
  synonym definition:
  
  pattern P x <- C1 x where
    P x = f (C1 x)
  
  f (P x) = C2 x
  
  In this case, 'P' needs to be typechecked in two passes:
  
  1. Typecheck the pattern definition of 'P', which fully determines the
     type of 'P'. This step doesn't require knowing anything about 'f',
     since the builder definition is not looked at.
  
  2. Typecheck the builder definition, which needs the typechecked
     definition of 'f' to be in scope; done by calls oo tcPatSynBuilderBind
     in GHC.Tc.Gen.Bind.tcValBinds.
  
  This behaviour is implemented in 'tcValBinds', but it crucially
  depends on 'P' not being put in a recursive group with 'f' (which
  would make it look like a recursive pattern synonym a la 'pattern P =
  P' which is unsound and rejected).
  
  So:
   * We do not include builder fvs in the Uses returned by rnPatSynBind
     (which is then used for dependency analysis)
   * But we /do/ include them in the psb_fvs for the PatSynBind
   * In rnValBinds we record these builder uses, to avoid bogus
     unused-variable warnings (#12548)
  -}
  
  {- *********************************************************************
  *                                                                      *
                  Class/instance method bindings
  *                                                                      *
  ********************************************************************* -}
  
  {- @rnMethodBinds@ is used for the method bindings of a class and an instance
  declaration.   Like @rnBinds@ but without dependency analysis.
  
  NOTA BENE: we record each {\em binder} of a method-bind group as a free variable.
  That's crucial when dealing with an instance decl:
  \begin{verbatim}
          instance Foo (T a) where
             op x = ...
  \end{verbatim}
  This might be the {\em sole} occurrence of @op@ for an imported class @Foo@,
  and unless @op@ occurs we won't treat the type signature of @op@ in the class
  decl for @Foo@ as a source of instance-decl gates.  But we should!  Indeed,
  in many ways the @op@ in an instance decl is just like an occurrence, not
  a binder.
  -}
  
  rnMethodBinds :: Bool                   -- True <=> is a class declaration
                -> Name                   -- Class name
                -> [Name]                 -- Type variables from the class/instance header
                -> LHsBinds GhcPs         -- Binds
                -> [LSig GhcPs]           -- and signatures/pragmas
                -> RnM (LHsBinds GhcRn, [LSig GhcRn], FreeVars)
  -- Used for
  --   * the default method bindings in a class decl
  --   * the method bindings in an instance decl
  rnMethodBinds is_cls_decl cls ktv_names binds sigs
    = do { checkDupRdrNames (collectMethodBinders binds)
               -- Check that the same method is not given twice in the
               -- same instance decl      instance C T where
               --                       f x = ...
               --                       g y = ...
               --                       f x = ...
               -- We must use checkDupRdrNames because the Name of the
               -- method is the Name of the class selector, whose SrcSpan
               -- points to the class declaration; and we use rnMethodBinds
               -- for instance decls too
  
         -- Rename the bindings LHSs
         ; binds' <- foldrM (rnMethodBindLHS is_cls_decl cls) [] binds
  
         -- Rename the pragmas and signatures
         -- Annoyingly the type variables /are/ in scope for signatures, but
         -- /are not/ in scope in SPECIALISE and SPECIALISE instance pragmas.
         -- See Note [Type variable scoping in SPECIALISE pragmas].
         ; let (spec_prags, other_sigs) = partition (isSpecLSig <||> isSpecInstLSig) sigs
               bound_nms = mkNameSet (collectHsBindsBinders CollNoDictBinders binds')
               sig_ctxt | is_cls_decl = ClsDeclCtxt cls
                        | otherwise   = InstDeclCtxt (mkOccEnv [ (nameOccName n, n)
                                                               | n <- nonDetEltsUniqSet bound_nms ])
         ; (spec_prags', spg_fvs) <- renameSigs sig_ctxt spec_prags
         ; (other_sigs', sig_fvs) <- bindLocalNamesFV ktv_names $
                                        renameSigs sig_ctxt other_sigs
         ; let localCompletePrags = localCompletePragmas spec_prags'
  
         -- Update the TcGblEnv with renamed COMPLETE pragmas from the current
         -- module, for pattern irrefutability checking in do notation.
         ; updGblEnv (\gblEnv -> gblEnv { tcg_complete_matches = tcg_complete_matches gblEnv ++ localCompletePrags
                                        , tcg_complete_match_env = tcg_complete_match_env gblEnv ++ localCompletePrags}) $
      do {
         -- Rename the bindings RHSs.  Again there's an issue about whether the
         -- type variables from the class/instance head are in scope.
         -- Answer no in Haskell 2010, but yes if you have -XScopedTypeVariables
         ; (binds'', bind_fvs) <- bindSigTyVarsFV ktv_names $
                do { binds_w_dus <- mapM (rnLBind (mkScopedTvFn other_sigs')) binds'
                   ; let bind_fvs = foldr (\(_,_,fv1) fv2 -> fv1 `plusFV` fv2)
                                             emptyFVs binds_w_dus
                   ; return (map fstOf3 binds_w_dus, bind_fvs) }
  
         ; return ( binds'', spec_prags' ++ other_sigs'
                  , sig_fvs `plusFV` spg_fvs `plusFV` bind_fvs) } }
  
  {- Note [Type variable scoping in SPECIALISE pragmas]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  When renaming the methods of a class or instance declaration, we must be careful
  with the scoping of the type variables that occur in SPECIALISE and SPECIALISE instance
  pragmas: the type variables from the class/instance header DO NOT scope over these,
  unlike class/instance method type signatures.
  
  Examples:
  
    1. SPECIALISE
  
      class C a where
        meth :: a
      instance C (Maybe a) where
        meth = Nothing
        {-# SPECIALISE INLINE meth :: Maybe [a] #-}
  
    2. SPECIALISE instance
  
      instance Eq a => Eq (T a) where
         (==) :: a -> a -> a
         {-# SPECIALISE instance Eq a => Eq (T [a]) #-}
  
    In both cases, the type variable `a` mentioned in the PRAGMA is NOT the same
    as the type variable `a` from the instance header.
    For example, the SPECIALISE instance pragma above is a shorthand for
  
        {-# SPECIALISE instance forall a. Eq a => Eq (T [a]) #-}
  
    which is alpha-equivalent to
  
        {-# SPECIALISE instance forall b. Eq b => Eq (T [b]) #-}
  
    This shows that the type variables are not bound in the header.
  
    Getting this scoping wrong can lead to out-of-scope type variable errors from
    Core Lint, see e.g. #22913.
  -}
  
  rnMethodBindLHS :: Bool -> Name
                  -> LHsBindLR GhcPs GhcPs
                  -> LHsBindsLR GhcRn GhcPs
                  -> RnM (LHsBindsLR GhcRn GhcPs)
  rnMethodBindLHS _ cls (L loc bind@(FunBind { fun_id = name })) rest
    = setSrcSpanA loc $ do
      do { sel_name <- wrapLocMA (lookupInstDeclBndr cls MethodOfClass) name
                       -- We use the selector name as the binder
         ; let bind' = bind { fun_id = sel_name, fun_ext = noExtField }
         ; return (L loc bind' : rest ) }
  
  -- Report error for all other forms of bindings
  -- This is why we use a fold rather than map
  rnMethodBindLHS is_cls_decl _ (L loc bind) rest
    = do { addErrAt (locA loc) $ TcRnIllegalClassBinding decl_sort bind
         ; return rest }
    where
      decl_sort | is_cls_decl = ClassDeclSort
                | otherwise   = InstanceDeclSort
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection[dep-Sigs]{Signatures (and user-pragmas for values)}
  *                                                                      *
  ************************************************************************
  
  @renameSigs@ checks for:
  \begin{enumerate}
  \item more than one sig for one thing;
  \item signatures given for things not bound here;
  \end{enumerate}
  
  At the moment we don't gather free-var info from the types in
  signatures.  We'd only need this if we wanted to report unused tyvars.
  -}
  
  renameSigs :: HsSigCtxt
             -> [LSig GhcPs]
             -> RnM ([LSig GhcRn], FreeVars)
  -- Renames the signatures and performs error checks
  renameSigs ctxt sigs
    = do  { mapM_ dupSigDeclErr (findDupSigs sigs)
  
          ; checkDupMinimalSigs sigs
  
          ; (sigs', sig_fvs) <- mapFvRn (wrapLocFstMA (renameSig ctxt)) sigs
  
          ; let (good_sigs, bad_sigs) = partition (okHsSig ctxt) sigs'
          ; mapM_ misplacedSigErr bad_sigs                 -- Misplaced
  
          ; return (good_sigs, sig_fvs) }
  
  ----------------------
  renameSig :: HsSigCtxt -> Sig GhcPs -> RnM (Sig GhcRn, FreeVars)
  renameSig ctxt sig@(TypeSig _ vs ty)
    = do  { new_vs <- mapM (lookupSigOccRn ctxt sig) vs
          ; let doc = TypeSigCtx vs
          ; (new_ty, fvs) <- rnHsSigWcType doc ty
          ; return (TypeSig noAnn new_vs new_ty, fvs) }
  
  renameSig ctxt sig@(ClassOpSig _ is_deflt vs ty)
    = do  { defaultSigs_on <- xoptM LangExt.DefaultSignatures
          ; when (is_deflt && not defaultSigs_on) $
            addErr (TcRnUnexpectedDefaultSig sig)
          ; new_v <- mapM (lookupSigOccRn ctxt sig) vs
          ; (new_ty, fvs) <- rnHsSigType ty_ctxt TypeLevel ty
          ; return (ClassOpSig noAnn is_deflt new_v new_ty, fvs) }
    where
      v1:|_ = expectNonEmpty vs
      ty_ctxt = ClassMethodSigCtx v1
  
  renameSig _ (SpecInstSig (_, src) ty)
    = do  { checkInferredVars doc ty
          ; (new_ty, fvs) <- rnHsSigType doc TypeLevel ty
            -- Check if there are any nested `forall`s or contexts, which are
            -- illegal in the type of an instance declaration (see
            -- Note [No nested foralls or contexts in instance types] in
            -- GHC.Hs.Type).
          ; addNoNestedForallsContextsErr doc NFC_Specialize
              (getLHsInstDeclHead new_ty)
          ; return (SpecInstSig (noAnn, src) new_ty,fvs) }
    where
      doc = SpecInstSigCtx
  
  -- {-# SPECIALISE #-} pragmas can refer to imported Ids
  -- so, in the top-level case (when mb_names is Nothing)
  -- we use lookupOccRn.  If there's both an imported and a local 'f'
  -- then the SPECIALISE pragma is ambiguous, unlike all other signatures
  renameSig ctxt sig@(SpecSig _ v tys inl)
    = do  { new_v <- case ctxt of
                       TopSigCtxt {} -> lookupLocatedOccRn WL_TermVariable v
                       _             -> lookupSigOccRn ctxt sig v
          ; (new_ty, fvs) <- foldM do_one ([],emptyFVs) tys
          ; return (SpecSig noAnn new_v new_ty inl, fvs) }
    where
      do_one (tys,fvs) ty
        = do { (new_ty, fvs_ty) <- rnHsSigType (SpecialiseSigCtx v) TypeLevel ty
             ; return ( new_ty:tys, fvs_ty `plusFV` fvs) }
  
  renameSig _ctxt (SpecSigE _ bndrs spec_e inl)
    = do { fn_rdr <- checkSpecESigShape spec_e
         ; fn_name <- lookupOccRn WL_TermVariable fn_rdr  -- Checks that the head isn't forall-bound
         ; bindRuleBndrs (SpecECtx fn_rdr) bndrs $ \_ bndrs' ->
           do { (spec_e', fvs) <- rnLExpr spec_e
              ; return (SpecSigE fn_name bndrs' spec_e' inl, fvs) } }
  
  renameSig ctxt sig@(InlineSig _ v s)
    = do  { new_v <- lookupSigOccRn ctxt sig v
          ; return (InlineSig noAnn new_v s, emptyFVs) }
  
  renameSig ctxt (FixSig _ fsig)
    = do  { new_fsig <- rnSrcFixityDecl ctxt fsig
          ; return (FixSig noAnn new_fsig, emptyFVs) }
  
  renameSig ctxt sig@(MinimalSig (_, s) (L l bf))
    = do new_bf <- bfTraverse (lookupSigOccRn ctxt sig) bf
         return (MinimalSig (noAnn, s) (L l new_bf), emptyFVs)
  
  renameSig ctxt sig@(PatSynSig _ vs ty)
    = do  { new_vs <- mapM (lookupSigOccRn ctxt sig) vs
          ; (ty', fvs) <- rnHsSigType ty_ctxt TypeLevel ty
          ; return (PatSynSig noAnn new_vs ty', fvs) }
    where
      ty_ctxt = PatSynSigCtx vs
  
  renameSig ctxt sig@(SCCFunSig (_, st) v s)
    = do  { new_v <- lookupSigOccRn ctxt sig v
          ; return (SCCFunSig (noAnn, st) new_v s, emptyFVs) }
  
  -- COMPLETE Sigs can refer to imported IDs which is why we use
  -- lookupLocatedOccRn rather than lookupSigOccRn
  renameSig _ctxt (CompleteMatchSig (_, s) bf mty)
    = do new_bf <- traverse (lookupLocatedOccRn WL_ConLike) bf
         new_mty  <- traverse (lookupLocatedOccRn WL_TyCon) mty
  
         this_mod <- fmap tcg_mod getGblEnv
         let rn_sig = CompleteMatchSig (noAnn, s) new_bf new_mty
         unless (any (nameIsLocalOrFrom this_mod . unLoc) new_bf) $
           -- Why 'any'? See Note [Orphan COMPLETE pragmas]
           addErrCtxt (SigCtxt rn_sig) $ failWithTc TcRnOrphanCompletePragma
  
         return (rn_sig, emptyFVs)
  
  
  checkSpecESigShape :: LHsExpr GhcPs -> RnM RdrName
  -- Checks the shape of a SPECIALISE
  -- That it looks like  (f a1 .. an [ :: ty ])
  checkSpecESigShape spec_e = go_l spec_e
    where
      go_l (L _ e) = go e
  
      go :: HsExpr GhcPs -> RnM RdrName
      go (ExprWithTySig _ fn _) = go_l fn
      go (HsApp _ fn _)         = go_l fn
      go (HsAppType _ fn _)     = go_l fn
      go (HsVar _ (L _ fn))     = return fn
      go (HsPar _ e)            = go_l e
      go _ = failWithTc (TcRnSpecSigShape spec_e)
  
  {-
  Note [Orphan COMPLETE pragmas]
  ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
  We define a COMPLETE pragma to be a non-orphan if it includes at least
  one conlike defined in the current module. Why is this sufficient?
  Well if you have a pattern match
  
    case expr of
      P1 -> ...
      P2 -> ...
      P3 -> ...
  
  any COMPLETE pragma which mentions a conlike other than P1, P2 or P3
  will not be of any use in verifying that the pattern match is
  exhaustive. So as we have certainly read the interface files that
  define P1, P2 and P3, we will have loaded all non-orphan COMPLETE
  pragmas that could be relevant to this pattern match.
  
  For now we simply disallow orphan COMPLETE pragmas, as the added
  complexity of supporting them properly doesn't seem worthwhile.
  -}
  
  okHsSig :: HsSigCtxt -> LSig (GhcPass a) -> Bool
  okHsSig ctxt (L _ sig)
    = case (sig, ctxt) of
       (ClassOpSig {}, ClsDeclCtxt {})  -> True
       (ClassOpSig {}, InstDeclCtxt {}) -> True
       (ClassOpSig {}, _)               -> False
  
       (TypeSig {}, ClsDeclCtxt {})  -> False
       (TypeSig {}, InstDeclCtxt {}) -> False
       (TypeSig {}, _)               -> True
  
       (PatSynSig {}, TopSigCtxt{}) -> True
       (PatSynSig {}, _)            -> False
  
       (FixSig {}, InstDeclCtxt {}) -> False
       (FixSig {}, _)               -> True
  
       (InlineSig {}, HsBootCtxt {}) -> False
       (InlineSig {}, _)             -> True
  
       (SpecSig {},  ctxt) -> ok_spec_ctxt ctxt
       (SpecSigE {}, ctxt) -> ok_spec_ctxt ctxt
  
       (SpecInstSig {}, InstDeclCtxt {}) -> True
       (SpecInstSig {}, _)               -> False
  
       (MinimalSig {}, ClsDeclCtxt {}) -> True
       (MinimalSig {}, _)              -> False
  
       (SCCFunSig {}, HsBootCtxt {}) -> False
       (SCCFunSig {}, _)             -> True
  
       (CompleteMatchSig {}, TopSigCtxt {} ) -> True
       (CompleteMatchSig {}, _)              -> False
  
       (XSig {}, TopSigCtxt {})   -> True
       (XSig {}, InstDeclCtxt {}) -> True
       (XSig {}, _)               -> False
  
  ok_spec_ctxt ::HsSigCtxt -> Bool
  -- Contexts where SPECIALISE can occur
  ok_spec_ctxt (TopSigCtxt {})    = True
  ok_spec_ctxt (LocalBindCtxt {}) = True
  ok_spec_ctxt (InstDeclCtxt {})  = True
  ok_spec_ctxt _                  = False
  
  -------------------
  findDupSigs :: [LSig GhcPs] -> [NonEmpty (LocatedN RdrName, Sig GhcPs)]
  -- Check for duplicates on RdrName version,
  -- because renamed version has unboundName for
  -- not-in-scope binders, which gives bogus dup-sig errors
  -- NB: in a class decl, a 'generic' sig is not considered
  --     equal to an ordinary sig, so we allow, say
  --           class C a where
  --             op :: a -> a
  --             default op :: Eq a => a -> a
  findDupSigs sigs
    = findDupsEq matching_sig (concatMap (expand_sig . unLoc) sigs)
    where
      expand_sig :: Sig GhcPs -> [(LocatedN RdrName, Sig GhcPs)] -- AZ
      expand_sig sig@(FixSig _ (FixitySig _ ns _)) = zip ns (repeat sig)
      expand_sig sig@(InlineSig _ n _)             = [(n,sig)]
      expand_sig sig@(TypeSig _ ns _)              = [(n,sig) | n <- ns]
      expand_sig sig@(ClassOpSig _ _ ns _)         = [(n,sig) | n <- ns]
      expand_sig sig@(PatSynSig _ ns  _ )          = [(n,sig) | n <- ns]
      expand_sig sig@(SCCFunSig (_, _) n _)           = [(n,sig)]
      expand_sig _ = []
  
      matching_sig :: (LocatedN RdrName, Sig GhcPs) -> (LocatedN RdrName, Sig GhcPs) -> Bool --AZ
      matching_sig (L _ n1,sig1) (L _ n2,sig2)       = n1 == n2 && mtch sig1 sig2
      mtch (FixSig {})           (FixSig {})         = True
      mtch (InlineSig {})        (InlineSig {})      = True
      mtch (TypeSig {})          (TypeSig {})        = True
      mtch (ClassOpSig _ d1 _ _) (ClassOpSig _ d2 _ _) = d1 == d2
      mtch (PatSynSig _ _ _)     (PatSynSig _ _ _)   = True
      mtch (SCCFunSig{})         (SCCFunSig{})       = True
      mtch _ _ = False
  
  -- Warn about multiple MINIMAL signatures
  checkDupMinimalSigs :: [LSig GhcPs] -> RnM ()
  checkDupMinimalSigs sigs
    = case filter isMinimalLSig sigs of
        sig1 : sig2 : otherSigs -> dupMinimalSigErr sig1 sig2 otherSigs
        _ -> return ()
  
  localCompletePragmas :: [LSig GhcRn] -> CompleteMatches
  localCompletePragmas sigs = mapMaybe (getCompleteSig . unLoc) $ reverse sigs
    where
      getCompleteSig = \case
        CompleteMatchSig _ cons mbTyCon ->
          Just $ CompleteMatch (mkUniqDSet $ map unLoc cons) (fmap unLoc mbTyCon)
        _ -> Nothing
    -- SG: for some reason I haven't investigated further, the signatures come in
    -- backwards wrt. declaration order. So we reverse them here, because it makes
    -- a difference for incomplete match suggestions.
  
  bindRuleBndrs :: HsDocContext -> RuleBndrs GhcPs
                -> ([Name] -> RuleBndrs GhcRn -> RnM (a,FreeVars))
                -> RnM (a,FreeVars)
  bindRuleBndrs doc (RuleBndrs { rb_tyvs = tyvs, rb_tmvs = tmvs }) thing_inside
    = do { let rdr_names_w_loc = map (get_var . unLoc) tmvs
         ; checkDupRdrNames rdr_names_w_loc
         ; checkShadowedRdrNames rdr_names_w_loc
         ; names <- newLocalBndrsRn rdr_names_w_loc
         ; bindRuleTyVars doc tyvs             $ \ tyvs' ->
           bindRuleTmVars doc tyvs' tmvs names $ \ tmvs' ->
           thing_inside names (RuleBndrs { rb_ext = noExtField
                                         , rb_tyvs = tyvs', rb_tmvs = tmvs' }) }
    where
      get_var :: RuleBndr GhcPs -> LocatedN RdrName
      get_var (RuleBndrSig _ v _) = v
      get_var (RuleBndr _ v)      = v
  
  
  bindRuleTmVars :: HsDocContext -> Maybe ty_bndrs
                 -> [LRuleBndr GhcPs] -> [Name]
                 -> ([LRuleBndr GhcRn] -> RnM (a, FreeVars))
                 -> RnM (a, FreeVars)
  bindRuleTmVars doc tyvs vars names thing_inside
    = go vars names $ \ vars' ->
      bindLocalNamesFV names (thing_inside vars')
    where
      go ((L l (RuleBndr _ (L loc _))) : vars) (n : ns) thing_inside
        = go vars ns $ \ vars' ->
          thing_inside (L l (RuleBndr noAnn (L loc n)) : vars')
  
      go ((L l (RuleBndrSig _ (L loc _) bsig)) : vars)
         (n : ns) thing_inside
        = rnHsPatSigType bind_free_tvs doc bsig $ \ bsig' ->
          go vars ns $ \ vars' ->
          thing_inside (L l (RuleBndrSig noAnn (L loc n) bsig') : vars')
  
      go [] [] thing_inside = thing_inside []
      go vars names _ = pprPanic "bindRuleVars" (ppr vars $$ ppr names)
  
      bind_free_tvs = case tyvs of Nothing -> AlwaysBind
                                   Just _  -> NeverBind
  
  bindRuleTyVars :: HsDocContext -> Maybe [LHsTyVarBndr () GhcPs]
                 -> (Maybe [LHsTyVarBndr () GhcRn]  -> RnM (b, FreeVars))
                 -> RnM (b, FreeVars)
  bindRuleTyVars doc (Just bndrs) thing_inside
    = bindLHsTyVarBndrs doc WarnUnusedForalls Nothing bndrs (thing_inside . Just)
  bindRuleTyVars _ _ thing_inside = thing_inside Nothing
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Match}
  *                                                                      *
  ************************************************************************
  -}
  
  type AnnoBody body
    = ( Anno [LocatedA (Match GhcRn (LocatedA (body GhcRn)))] ~ SrcSpanAnnLW
      , Anno [LocatedA (Match GhcPs (LocatedA (body GhcPs)))] ~ SrcSpanAnnLW
      , Anno (Match GhcRn (LocatedA (body GhcRn))) ~ SrcSpanAnnA
      , Anno (Match GhcPs (LocatedA (body GhcPs))) ~ SrcSpanAnnA
      , Anno (GRHS GhcRn (LocatedA (body GhcRn))) ~ EpAnnCO
      , Anno (GRHS GhcPs (LocatedA (body GhcPs))) ~ EpAnnCO
      , Outputable (body GhcPs)
      )
  
  -- Note [Empty MatchGroups]
  -- ~~~~~~~~~~~~~~~~~~~~~~~~
  -- In some cases, MatchGroups are allowed to be empty. Firstly, the
  -- prerequisite is that -XEmptyCase is enabled. Then you have an empty
  -- MatchGroup resulting either from a case-expression:
  --
  --     case e of {}
  --
  -- or from a \case-expression:
  --
  --     \case {}
  --
  -- NB: \cases {} is not allowed, since it's not clear how many patterns this
  -- should match on.
  --
  -- The same applies in arrow notation commands: With -XEmptyCases, it is
  -- allowed in case- and \case-commands, but not \cases.
  --
  -- Since the lambda expressions and empty function definitions are already
  -- disallowed elsewhere, here, we only need to make sure we don't accept empty
  -- \cases expressions or commands. In that case, or if we encounter an empty
  -- MatchGroup but -XEmptyCases is disabled, we add an error.
  
  rnMatchGroup :: (Outputable (body GhcPs), AnnoBody body) => HsMatchContextRn
               -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
               -> MatchGroup GhcPs (LocatedA (body GhcPs))
               -> RnM (MatchGroup GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnMatchGroup ctxt rnBody (MG { mg_alts = L lm ms, mg_ext = origin })
           -- see Note [Empty MatchGroups]
    = do { when (null ms) $ checkEmptyCase ctxt
         ; (new_ms, ms_fvs) <- mapFvRn (rnMatch ctxt rnBody) ms
         ; return (mkMatchGroup origin (L lm new_ms), ms_fvs) }
  
  -- Check the validity of a MatchGroup with an empty list of alternatives.
  --
  --  1. Normal `case x of {}` passes this check as long as EmptyCase is enabled.
  --     Ditto lambda-case `\case {}`.
  --
  --  2. Multi-case with no alternatives `\cases {}` is never valid.
  --
  --  3. Other MatchGroup contexts (FunRhs, LamAlt LamSingle, etc) are not
  --     considered here because there is no syntax to construct them with
  --     no alternatives.
  --
  -- Test case: rename/should_fail/RnEmptyCaseFail
  --
  -- Validation continues in the type checker, namely in tcMatches.
  -- See Note [Pattern types for EmptyCase] in GHC.Tc.Gen.Match
  checkEmptyCase :: HsMatchContextRn -> RnM ()
  checkEmptyCase ctxt
    | disallowed_ctxt =
        addErr (TcRnEmptyCase ctxt EmptyCaseDisallowedCtxt)
    | otherwise =
        unlessXOptM LangExt.EmptyCase $
          addErr (TcRnEmptyCase ctxt EmptyCaseWithoutFlag)
    where
      disallowed_ctxt =
        case ctxt of
          LamAlt LamCases -> True
          ArrowMatchCtxt (ArrowLamAlt LamCases) -> True
          _ -> False
  
  rnMatch :: AnnoBody body
          => HsMatchContextRn
          -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
          -> LMatch GhcPs (LocatedA (body GhcPs))
          -> RnM (LMatch GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnMatch ctxt rnBody = wrapLocFstMA (rnMatch' ctxt rnBody)
  
  rnMatch' :: (AnnoBody body)
           => HsMatchContextRn
           -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
           -> Match GhcPs (LocatedA (body GhcPs))
           -> RnM (Match GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnMatch' ctxt rnBody (Match { m_ctxt = mf, m_pats = L l pats, m_grhss = grhss })
    = rnPats ctxt pats $ \ pats' -> do
          { (grhss', grhss_fvs) <- rnGRHSs ctxt rnBody grhss
          ; let mf' = case (ctxt, mf) of
                        (FunRhs { mc_fun = L _ funid }, FunRhs { mc_fun = L lf _ })
                                              -> mf { mc_fun = L lf funid }
                        _                     -> ctxt
          ; return (Match { m_ext = noExtField, m_ctxt = mf', m_pats = L l pats'
                          , m_grhss = grhss'}, grhss_fvs ) }
  
  
  {-
  ************************************************************************
  *                                                                      *
  \subsubsection{Guarded right-hand sides (GRHSs)}
  *                                                                      *
  ************************************************************************
  -}
  
  rnGRHSs :: AnnoBody body
          => HsMatchContextRn
          -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
          -> GRHSs GhcPs (LocatedA (body GhcPs))
          -> RnM (GRHSs GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnGRHSs ctxt rnBody (GRHSs _ grhss binds)
    = rnLocalBindsAndThen binds   $ \ binds' _ -> do
      (grhss', fvGRHSs) <- mapFvRn (rnGRHS ctxt rnBody) grhss
      return (GRHSs emptyComments grhss' binds', fvGRHSs)
  
  rnGRHS :: AnnoBody body
         => HsMatchContextRn
         -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
         -> LGRHS GhcPs (LocatedA (body GhcPs))
         -> RnM (LGRHS GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnGRHS ctxt rnBody = wrapLocFstMA (rnGRHS' ctxt rnBody)
  
  rnGRHS' :: HsMatchContextRn
          -> (LocatedA (body GhcPs) -> RnM (LocatedA (body GhcRn), FreeVars))
          -> GRHS GhcPs (LocatedA (body GhcPs))
          -> RnM (GRHS GhcRn (LocatedA (body GhcRn)), FreeVars)
  rnGRHS' ctxt rnBody (GRHS _ guards rhs)
    = do  { pattern_guards_allowed <- xoptM LangExt.PatternGuards
          ; ((guards', rhs'), fvs) <- rnStmts (PatGuard ctxt) rnExpr guards $ \ _ ->
                                      rnBody rhs
  
          ; unless (pattern_guards_allowed || is_standard_guard guards') $
              addDiagnostic (nonStdGuardErr guards')
  
          ; return (GRHS noAnn guards' rhs', fvs) }
    where
          -- Standard Haskell 1.4 guards are just a single boolean
          -- expression, rather than a list of qualifiers as in the
          -- Glasgow extension
      is_standard_guard []                  = True
      is_standard_guard [L _ (BodyStmt {})] = True
      is_standard_guard _                   = False
  
  {-
  *********************************************************
  *                                                       *
          Source-code fixity declarations
  *                                                       *
  *********************************************************
  -}
  
  rnSrcFixityDecl :: HsSigCtxt -> FixitySig GhcPs -> RnM (FixitySig GhcRn)
  -- Rename a fixity decl, so we can put
  -- the renamed decl in the renamed syntax tree
  -- Errors if the thing being fixed is not defined locally.
  rnSrcFixityDecl sig_ctxt = rn_decl
    where
      rn_decl :: FixitySig GhcPs -> RnM (FixitySig GhcRn)
          -- GHC extension: look up both the tycon and data con
          -- for con-like things; hence returning a list
          -- If neither are in scope, report an error; otherwise
          -- return a fixity sig for each (slightly odd)
      rn_decl sig@(FixitySig ns_spec fnames fixity)
        = do unlessXOptM LangExt.ExplicitNamespaces $
               when (ns_spec /= NoNamespaceSpecifier) $
               addErr (TcRnNamespacedFixitySigWithoutFlag sig)
             names <- concatMapM (lookup_one ns_spec) fnames
             return (FixitySig ns_spec names fixity)
  
      lookup_one :: NamespaceSpecifier -> LocatedN RdrName -> RnM [LocatedN Name]
      lookup_one ns_spec (L name_loc rdr_name)
        = setSrcSpanA name_loc $
                      -- This lookup will fail if the name is not defined in the
                      -- same binding group as this fixity declaration.
          do names <- lookupLocalTcNames sig_ctxt SigLikeFixitySig ns_spec rdr_name
             return [ L name_loc name | (_, name) <- names ]
  
  {-
  ************************************************************************
  *                                                                      *
  \subsection{Error messages}
  *                                                                      *
  ************************************************************************
  -}
  
  dupSigDeclErr :: NonEmpty (LocatedN RdrName, Sig GhcPs) -> RnM ()
  dupSigDeclErr pairs@((L loc _, _) :| _)
    = addErrAt (locA loc) $ TcRnDuplicateSigDecl pairs
  
  misplacedSigErr :: LSig GhcRn -> RnM ()
  misplacedSigErr (L loc sig)
    = addErrAt (locA loc) $ TcRnMisplacedSigDecl sig
  
  nonStdGuardErr :: (Outputable body,
                     Anno (Stmt GhcRn body) ~ SrcSpanAnnA)
                 => [LStmtLR GhcRn GhcRn body] -> TcRnMessage
  nonStdGuardErr guards = TcRnNonStdGuards (NonStandardGuards guards)
  
  dupMinimalSigErr :: LSig GhcPs -> LSig GhcPs -> [LSig GhcPs] -> RnM ()
  dupMinimalSigErr sig1 sig2 otherSigs
    = addErrAt (getLocA sig1) $ TcRnDuplicateMinimalSig sig1 sig2 otherSigs
  