Make NoExtCon fields strictwip/strict-NoExtCon

This changes every unused TTG extension constructor to be strict in
its field so that the pattern-match coverage checker is smart enough
any such constructors are unreachable in pattern matches. This lets
us remove nearly every use of `noExtCon` in the GHC API. The only
ones we cannot remove are ones underneath uses of `ghcPass`, but that
is only because GHC 8.8's and 8.10's coverage checkers weren't smart
enough to perform this kind of reasoning. GHC HEAD's coverage
checker, on the other hand, _is_ smart enough, so we guard these uses
of `noExtCon` with CPP for now.

Bumps the `haddock` submodule.

Fixes #17992.

11 files changed, 2 insertions, 62 deletions

diff --git a/compiler/GHC/Tc/Gen/Annotation.hs b/compiler/GHC/Tc/Gen/Annotation.hs
index 00c52ea247..ef7168076f 100644
--- a/compiler/GHC/Tc/Gen/Annotation.hs
+++ b/compiler/GHC/Tc/Gen/Annotation.hs
@@ -58,7 +58,6 @@ tcAnnotation (L loc ann@(HsAnnotation _ _ provenance expr)) = do
     where
       safeHsErr = vcat [ text "Annotations are not compatible with Safe Haskell."
                   , text "See https://gitlab.haskell.org/ghc/ghc/issues/10826" ]
-tcAnnotation (L _ (XAnnDecl nec)) = noExtCon nec
 
 annProvenanceToTarget :: Module -> AnnProvenance Name
                       -> AnnTarget Name
diff --git a/compiler/GHC/Tc/Gen/Arrow.hs b/compiler/GHC/Tc/Gen/Arrow.hs
index 435bf4d89c..9a30f56365 100644
--- a/compiler/GHC/Tc/Gen/Arrow.hs
+++ b/compiler/GHC/Tc/Gen/Arrow.hs
@@ -128,7 +128,6 @@ tcCmdTop env (L loc (HsCmdTop names cmd)) cmd_ty@(cmd_stk, res_ty)
     do  { cmd'   <- tcCmd env cmd cmd_ty
         ; names' <- mapM (tcSyntaxName ProcOrigin (cmd_arr env)) names
         ; return (L loc $ HsCmdTop (CmdTopTc cmd_stk res_ty names') cmd') }
-tcCmdTop _ (L _ (XCmdTop nec)) _ = noExtCon nec
 
 ----------------------------------------
 tcCmd  :: CmdEnv -> LHsCmd GhcRn -> CmdType -> TcM (LHsCmd GhcTcId)
@@ -273,14 +272,12 @@ tc_cmd env
         = do { (binds', grhss') <- tcLocalBinds binds $
                                    mapM (wrapLocM (tc_grhs stk_ty res_ty)) grhss
              ; return (GRHSs x grhss' (L l binds')) }
-    tc_grhss (XGRHSs nec) _ _ = noExtCon nec
 
     tc_grhs stk_ty res_ty (GRHS x guards body)
         = do { (guards', rhs') <- tcStmtsAndThen pg_ctxt tcGuardStmt guards res_ty $
                                   \ res_ty -> tcCmd env body
                                                 (stk_ty, checkingExpType "tc_grhs" res_ty)
              ; return (GRHS x guards' rhs') }
-    tc_grhs _ _ (XGRHS nec) = noExtCon nec
 
 -------------------------------------------
 --              Do notation
@@ -325,8 +322,6 @@ tc_cmd env cmd@(HsCmdArrForm x expr f fixity cmd_args) (cmd_stk, res_ty)
             ; cmd' <- tcCmdTop env' cmd (stk_ty, res_ty)
             ; return (cmd',  mkCmdArrTy env' (mkPairTy alphaTy stk_ty) res_ty) }
 
-tc_cmd _ (XCmd nec) _ = noExtCon nec
-
 -----------------------------------------------------------------
 --              Base case for illegal commands
 -- This is where expressions that aren't commands get rejected
diff --git a/compiler/GHC/Tc/Gen/Bind.hs b/compiler/GHC/Tc/Gen/Bind.hs
index 6750a77500..8977ff3cd4 100644
--- a/compiler/GHC/Tc/Gen/Bind.hs
+++ b/compiler/GHC/Tc/Gen/Bind.hs
@@ -358,16 +358,12 @@ tcLocalBinds (HsIPBinds x (IPBinds _ ip_binds)) thing_inside
             ; let d = toDict ipClass p ty `fmap` expr'
             ; return (ip_id, (IPBind noExtField (Right ip_id) d)) }
     tc_ip_bind _ (IPBind _ (Right {}) _) = panic "tc_ip_bind"
-    tc_ip_bind _ (XIPBind nec) = noExtCon nec
 
     -- Coerces a `t` into a dictionary for `IP "x" t`.
     -- co : t -> IP "x" t
     toDict ipClass x ty = mkHsWrap $ mkWpCastR $
                           wrapIP $ mkClassPred ipClass [x,ty]
 
-tcLocalBinds (HsIPBinds _ (XHsIPBinds nec)) _ = noExtCon nec
-tcLocalBinds (XHsLocalBindsLR nec)          _ = noExtCon nec
-
 {- Note [Implicit parameter untouchables]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 We add the type variables in the types of the implicit parameters
diff --git a/compiler/GHC/Tc/Gen/Default.hs b/compiler/GHC/Tc/Gen/Default.hs
index ab3ef76fca..29fb7ee7e0 100644
--- a/compiler/GHC/Tc/Gen/Default.hs
+++ b/compiler/GHC/Tc/Gen/Default.hs
@@ -66,7 +66,6 @@ tcDefaults [L locn (DefaultDecl _ mono_tys)]
 tcDefaults decls@(L locn (DefaultDecl _ _) : _)
   = setSrcSpan locn $
     failWithTc (dupDefaultDeclErr decls)
-tcDefaults (L _ (XDefaultDecl nec):_) = noExtCon nec
 
 
 tc_default_ty :: [Class] -> LHsType GhcRn -> TcM Type
@@ -98,10 +97,9 @@ dupDefaultDeclErr (L _ (DefaultDecl _ _) : dup_things)
   = hang (text "Multiple default declarations")
        2 (vcat (map pp dup_things))
   where
+    pp :: Located (DefaultDecl GhcRn) -> SDoc
     pp (L locn (DefaultDecl _ _))
       = text "here was another default declaration" <+> ppr locn
-    pp (L _ (XDefaultDecl nec)) = noExtCon nec
-dupDefaultDeclErr (L _ (XDefaultDecl nec) : _) = noExtCon nec
 dupDefaultDeclErr [] = panic "dupDefaultDeclErr []"
 
 badDefaultTy :: Type -> [Class] -> SDoc
diff --git a/compiler/GHC/Tc/Gen/Expr.hs b/compiler/GHC/Tc/Gen/Expr.hs
index 55f2a105c6..3468a015e5 100644
--- a/compiler/GHC/Tc/Gen/Expr.hs
+++ b/compiler/GHC/Tc/Gen/Expr.hs
@@ -203,7 +203,6 @@ tcExpr (HsPragE x prag expr) res_ty
     tc_prag (HsPragSCC x1 src ann) = HsPragSCC x1 src ann
     tc_prag (HsPragCore x1 src lbl) = HsPragCore x1 src lbl
     tc_prag (HsPragTick x1 src info srcInfo) = HsPragTick x1 src info srcInfo
-    tc_prag (XHsPragE x) = noExtCon x
 
 tcExpr (HsOverLit x lit) res_ty
   = do  { lit' <- newOverloadedLit lit res_ty
@@ -1406,7 +1405,6 @@ tcTupArgs args tys
     go (L l (Missing {}),   arg_ty) = return (L l (Missing arg_ty))
     go (L l (Present x expr), arg_ty) = do { expr' <- tcPolyExpr expr arg_ty
                                            ; return (L l (Present x expr')) }
-    go (L _ (XTupArg nec), _) = noExtCon nec
 
 ---------------------------
 -- See TcType.SyntaxOpType also for commentary
@@ -1724,7 +1722,6 @@ tcCheckRecSelId rn_expr (Ambiguous _ lbl) res_ty
       Just (arg, _) -> do { sel_name <- disambiguateSelector lbl arg
                           ; tcCheckRecSelId rn_expr (Unambiguous sel_name lbl)
                                                     res_ty }
-tcCheckRecSelId _ (XAmbiguousFieldOcc nec) _ = noExtCon nec
 
 ------------------------
 tcInferRecSelId :: AmbiguousFieldOcc GhcRn -> TcM (HsExpr GhcTcId, TcRhoType)
@@ -1733,7 +1730,6 @@ tcInferRecSelId (Unambiguous sel (L _ lbl))
        ; return (expr', ty) }
 tcInferRecSelId (Ambiguous _ lbl)
   = ambiguousSelector lbl
-tcInferRecSelId (XAmbiguousFieldOcc nec) = noExtCon nec
 
 ------------------------
 tcInferId :: Name -> TcM (HsExpr GhcTcId, TcSigmaType)
@@ -1955,9 +1951,9 @@ too_many_args fun args
     hang (text "Too many type arguments to" <+> text fun <> colon)
        2 (sep (map pp args))
   where
+    pp :: LHsExprArgIn -> SDoc
     pp (HsValArg e)                             = ppr e
     pp (HsTypeArg _ (HsWC { hswc_body = L _ t })) = pprHsType t
-    pp (HsTypeArg _ (XHsWildCardBndrs nec)) = noExtCon nec
     pp (HsArgPar _) = empty
 
 
@@ -2242,7 +2238,6 @@ disambiguateRecordBinds record_expr record_rho rbnds res_ty
     isUnambiguous x = case unLoc (hsRecFieldLbl (unLoc x)) of
                         Unambiguous sel_name _ -> Just (x, sel_name)
                         Ambiguous{}            -> Nothing
-                        XAmbiguousFieldOcc nec -> noExtCon nec
 
     -- Look up the possible parents and selector GREs for each field
     getUpdFieldsParents :: TcM [(LHsRecUpdField GhcRn
@@ -2442,7 +2437,6 @@ tcRecordField con_like flds_w_tys (L loc (FieldOcc sel_name lbl)) rhs
            ; return Nothing }
   where
         field_lbl = occNameFS $ rdrNameOcc (unLoc lbl)
-tcRecordField _ _ (L _ (XFieldOcc nec)) _ = noExtCon nec
 
 
 checkMissingFields ::  ConLike -> HsRecordBinds GhcRn -> TcM ()
diff --git a/compiler/GHC/Tc/Gen/HsType.hs b/compiler/GHC/Tc/Gen/HsType.hs
index c7a7f298f5..be5b4f7694 100644
--- a/compiler/GHC/Tc/Gen/HsType.hs
+++ b/compiler/GHC/Tc/Gen/HsType.hs
@@ -218,7 +218,6 @@ kcClassSigType skol_info names (HsIB { hsib_ext  = sig_vars
 
        ; emitResidualTvConstraint skol_info Nothing spec_tkvs
                                   tc_lvl wanted }
-kcClassSigType _ _ (XHsImplicitBndrs nec) = noExtCon nec
 
 tcClassSigType :: SkolemInfo -> [Located Name] -> LHsSigType GhcRn -> TcM Type
 -- Does not do validity checking
@@ -271,7 +270,6 @@ tcStandaloneKindSig (L _ kisig) = case kisig of
     do { kind <- tcTopLHsType kindLevelMode ksig (expectedKindInCtxt ctxt)
        ; checkValidType ctxt kind
        ; return (name, kind) }
-  XStandaloneKindSig nec -> noExtCon nec
 
 tc_hs_sig_type :: SkolemInfo -> LHsSigType GhcRn
                -> ContextKind -> TcM (Bool, TcType)
@@ -309,8 +307,6 @@ tc_hs_sig_type skol_info hs_sig_type ctxt_kind
 
        ; return (insolubleWC wanted, mkInvForAllTys kvs ty1) }
 
-tc_hs_sig_type _ (XHsImplicitBndrs nec) _ = noExtCon nec
-
 tcTopLHsType :: TcTyMode -> LHsSigType GhcRn -> ContextKind -> TcM Type
 -- tcTopLHsType is used for kind-checking top-level HsType where
 --   we want to fully solve /all/ equalities, and report errors
@@ -334,8 +330,6 @@ tcTopLHsType mode hs_sig_type ctxt_kind
        ; traceTc "End tcTopLHsType }" (vcat [ppr hs_ty, ppr final_ty])
        ; return final_ty}
 
-tcTopLHsType _ (XHsImplicitBndrs nec) _ = noExtCon nec
-
 -----------------
 tcHsDeriv :: LHsSigType GhcRn -> TcM ([TyVar], Class, [Type], [Kind])
 -- Like tcHsSigType, but for the ...deriving( C t1 ty2 ) clause
@@ -421,7 +415,6 @@ tcHsTypeApp wc_ty kind
        ; ty <- zonkTcType ty
        ; checkValidType TypeAppCtxt ty
        ; return ty }
-tcHsTypeApp (XHsWildCardBndrs nec) _ = noExtCon nec
 
 {- Note [Wildcards in visible type application]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1947,7 +1940,6 @@ kcCheckDeclHeader_cusk name flav
   where
     ctxt_kind | tcFlavourIsOpen flav = TheKind liftedTypeKind
               | otherwise            = AnyKind
-kcCheckDeclHeader_cusk _ _ (XLHsQTyVars nec) _ = noExtCon nec
 
 -- | Kind-check a 'LHsQTyVars'. Used in 'inferInitialKind' (for tycon kinds and
 -- other kinds).
@@ -2004,8 +1996,6 @@ kcInferDeclHeader name flav
     ctxt_kind | tcFlavourIsOpen flav = TheKind liftedTypeKind
               | otherwise            = AnyKind
 
-kcInferDeclHeader _ _ (XLHsQTyVars nec) _ = noExtCon nec
-
 -- | Kind-check a declaration header against a standalone kind signature.
 -- See Note [Arity inference in kcCheckDeclHeader_sig]
 kcCheckDeclHeader_sig
@@ -2201,7 +2191,6 @@ kcCheckDeclHeader_sig kisig name flav
             unifyKind (Just (HsTyVar noExtField NotPromoted v))
                       (tyBinderType tb)
                       v_ki
-        XTyVarBndr nec -> noExtCon nec
 
     -- Split the invisible binders that should become a part of 'tyConBinders'
     -- rather than 'tyConResKind'.
@@ -2217,8 +2206,6 @@ kcCheckDeclHeader_sig kisig name flav
           n_inst = n_sig_invis_bndrs - n_res_invis_bndrs
       in splitPiTysInvisibleN n_inst sig_ki
 
-kcCheckDeclHeader_sig _ _ _ (XLHsQTyVars nec) _ = noExtCon nec
-
 -- A quantifier from a kind signature zipped with a user-written binder for it.
 data ZippedBinder =
   ZippedBinder TyBinder (Maybe (LHsTyVarBndr GhcRn))
@@ -2709,7 +2696,6 @@ tcHsTyVarBndr new_tv (UserTyVar _ (L _ tv_nm))
 tcHsTyVarBndr new_tv (KindedTyVar _ (L _ tv_nm) lhs_kind)
   = do { kind <- tcLHsKindSig (TyVarBndrKindCtxt tv_nm) lhs_kind
        ; new_tv tv_nm kind }
-tcHsTyVarBndr _ (XTyVarBndr nec) = noExtCon nec
 
 -----------------
 tcHsQTyVarBndr :: ContextKind
@@ -2742,8 +2728,6 @@ tcHsQTyVarBndr _ new_tv (KindedTyVar _ (L _ tv_nm) lhs_kind)
     hs_tv = HsTyVar noExtField NotPromoted (noLoc tv_nm)
             -- Used for error messages only
 
-tcHsQTyVarBndr _ _ (XTyVarBndr nec) = noExtCon nec
-
 --------------------------------------
 -- Binding type/class variables in the
 -- kind-checking and typechecking phases
@@ -3200,9 +3184,6 @@ tcHsPartialSigType ctxt sig_ty
        ; traceTc "tcHsPartialSigType" (ppr tv_prs)
        ; return (wcs, wcx, tv_prs, theta, tau) }
 
-tcHsPartialSigType _ (HsWC _ (XHsImplicitBndrs nec)) = noExtCon nec
-tcHsPartialSigType _ (XHsWildCardBndrs nec) = noExtCon nec
-
 tcPartialContext :: HsContext GhcRn -> TcM (TcThetaType, Maybe TcType)
 tcPartialContext hs_theta
   | Just (hs_theta1, hs_ctxt_last) <- snocView hs_theta
@@ -3342,9 +3323,6 @@ tcHsPatSigType ctxt sig_ty
              -- NB: tv's Name may be fresh (in the case of newPatSigTyVar)
            ; return (name, tv) }
 
-tcHsPatSigType _ (HsWC _ (XHsImplicitBndrs nec)) = noExtCon nec
-tcHsPatSigType _ (XHsWildCardBndrs nec)          = noExtCon nec
-
 tcPatSig :: Bool                    -- True <=> pattern binding
          -> LHsSigWcType GhcRn
          -> ExpSigmaType
diff --git a/compiler/GHC/Tc/Gen/Match.hs b/compiler/GHC/Tc/Gen/Match.hs
index 314b81faa8..8ef022edbe 100644
--- a/compiler/GHC/Tc/Gen/Match.hs
+++ b/compiler/GHC/Tc/Gen/Match.hs
@@ -235,7 +235,6 @@ tcMatches ctxt pat_tys rhs_ty (MG { mg_alts = L l matches
        ; return (MG { mg_alts = L l matches'
                     , mg_ext = MatchGroupTc pat_tys rhs_ty
                     , mg_origin = origin }) }
-tcMatches _ _ _ (XMatchGroup nec) = noExtCon nec
 
 -------------
 tcMatch :: (Outputable (body GhcRn)) => TcMatchCtxt body
@@ -255,7 +254,6 @@ tcMatch ctxt pat_tys rhs_ty match
            ; return (Match { m_ext = noExtField
                            , m_ctxt = mc_what ctxt, m_pats = pats'
                            , m_grhss = grhss' }) }
-    tc_match  _ _ _ (XMatch nec) = noExtCon nec
 
         -- For (\x -> e), tcExpr has already said "In the expression \x->e"
         -- so we don't want to add "In the lambda abstraction \x->e"
@@ -280,7 +278,6 @@ tcGRHSs ctxt (GRHSs _ grhss (L l binds)) res_ty
                mapM (wrapLocM (tcGRHS ctxt res_ty)) grhss
 
         ; return (GRHSs noExtField grhss' (L l binds')) }
-tcGRHSs _ (XGRHSs nec) _ = noExtCon nec
 
 -------------
 tcGRHS :: TcMatchCtxt body -> ExpRhoType -> GRHS GhcRn (Located (body GhcRn))
@@ -293,7 +290,6 @@ tcGRHS ctxt res_ty (GRHS _ guards rhs)
         ; return (GRHS noExtField guards' rhs') }
   where
     stmt_ctxt  = PatGuard (mc_what ctxt)
-tcGRHS _ _ (XGRHS nec) = noExtCon nec
 
 {-
 ************************************************************************
@@ -483,7 +479,6 @@ tcLcStmt m_tc ctxt (ParStmt _ bndr_stmts_s _ _) elt_ty thing_inside
                       ; (pairs', thing) <- loop pairs
                       ; return (ids, pairs', thing) }
            ; return ( ParStmtBlock x stmts' ids noSyntaxExpr : pairs', thing ) }
-    loop (XParStmtBlock nec:_) = noExtCon nec
 
 tcLcStmt m_tc ctxt (TransStmt { trS_form = form, trS_stmts = stmts
                               , trS_bndrs =  bindersMap
@@ -1060,12 +1055,9 @@ tcApplicativeStmts ctxt pairs rhs_ty thing_inside
                   }
            ; return (ApplicativeArgMany x stmts' ret' pat') }
 
-    goArg _body_ty (XApplicativeArg nec, _, _) = noExtCon nec
-
     get_arg_bndrs :: ApplicativeArg GhcTcId -> [Id]
     get_arg_bndrs (ApplicativeArgOne { app_arg_pattern = pat }) = collectPatBinders pat
     get_arg_bndrs (ApplicativeArgMany { bv_pattern =  pat }) = collectPatBinders pat
-    get_arg_bndrs (XApplicativeArg nec)          = noExtCon nec
 
 {- Note [ApplicativeDo and constraints]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1121,5 +1113,3 @@ checkArgs fun (MG { mg_alts = L _ (match1:matches) })
 
     args_in_match :: LMatch GhcRn body -> Int
     args_in_match (L _ (Match { m_pats = pats })) = length pats
-    args_in_match (L _ (XMatch nec)) = noExtCon nec
-checkArgs _ (XMatchGroup nec) = noExtCon nec
diff --git a/compiler/GHC/Tc/Gen/Pat.hs b/compiler/GHC/Tc/Gen/Pat.hs
index 0fa2b74c14..f218b4e1be 100644
--- a/compiler/GHC/Tc/Gen/Pat.hs
+++ b/compiler/GHC/Tc/Gen/Pat.hs
@@ -1017,8 +1017,6 @@ tcConArgs con_like arg_tys (RecCon (HsRecFields rpats dd)) penv thing_inside
            ; (pat', res) <- tcConArg (pat, pat_ty) penv thing_inside
            ; return (L l (HsRecField (L loc (FieldOcc sel' (L lr rdr))) pat'
                                                                     pun), res) }
-    tc_field (L _ (HsRecField (L _ (XFieldOcc _)) _ _)) _ _
-           = panic "tcConArgs"
 
 
     find_field_ty :: Name -> FieldLabelString -> TcM TcType
diff --git a/compiler/GHC/Tc/Gen/Rule.hs b/compiler/GHC/Tc/Gen/Rule.hs
index 373dd42a83..eaa0534770 100644
--- a/compiler/GHC/Tc/Gen/Rule.hs
+++ b/compiler/GHC/Tc/Gen/Rule.hs
@@ -108,7 +108,6 @@ tcRuleDecls (HsRules { rds_src = src
         ; return $ HsRules { rds_ext   = noExtField
                            , rds_src   = src
                            , rds_rules = tc_decls } }
-tcRuleDecls (XRuleDecls nec) = noExtCon nec
 
 tcRule :: RuleDecl GhcRn -> TcM (RuleDecl GhcTcId)
 tcRule (HsRule { rd_ext  = ext
@@ -180,7 +179,6 @@ tcRule (HsRule { rd_ext  = ext
                                          (qtkvs ++ tpl_ids)
                          , rd_lhs  = mkHsDictLet lhs_binds lhs'
                          , rd_rhs  = mkHsDictLet rhs_binds rhs' } }
-tcRule (XRuleDecl nec) = noExtCon nec
 
 generateRuleConstraints :: Maybe [LHsTyVarBndr GhcRn] -> [LRuleBndr GhcRn]
                         -> LHsExpr GhcRn -> LHsExpr GhcRn
@@ -238,7 +236,6 @@ tcRuleTmBndrs (L _ (RuleBndrSig _ (L _ name) rn_ty) : rule_bndrs)
         ; (tyvars, tmvars) <- tcExtendNameTyVarEnv tvs $
                                    tcRuleTmBndrs rule_bndrs
         ; return (map snd tvs ++ tyvars, id : tmvars) }
-tcRuleTmBndrs (L _ (XRuleBndr nec) : _) = noExtCon nec
 
 ruleCtxt :: FastString -> SDoc
 ruleCtxt name = text "When checking the transformation rule" <+>
diff --git a/compiler/GHC/Tc/Gen/Sig.hs b/compiler/GHC/Tc/Gen/Sig.hs
index a6dfdcc2f4..cf7bd3c51d 100644
--- a/compiler/GHC/Tc/Gen/Sig.hs
+++ b/compiler/GHC/Tc/Gen/Sig.hs
@@ -258,8 +258,6 @@ isCompleteHsSig :: LHsSigWcType GhcRn -> Bool
 isCompleteHsSig (HsWC { hswc_ext  = wcs
                       , hswc_body = HsIB { hsib_body = hs_ty } })
    = null wcs && no_anon_wc hs_ty
-isCompleteHsSig (HsWC _ (XHsImplicitBndrs nec)) = noExtCon nec
-isCompleteHsSig (XHsWildCardBndrs nec) = noExtCon nec
 
 no_anon_wc :: LHsType GhcRn -> Bool
 no_anon_wc lty = go lty
@@ -300,7 +298,6 @@ no_anon_wc_bndrs ltvs = all (go . unLoc) ltvs
   where
     go (UserTyVar _ _)      = True
     go (KindedTyVar _ _ ki) = no_anon_wc ki
-    go (XTyVarBndr nec)     = noExtCon nec
 
 {- Note [Fail eagerly on bad signatures]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -465,7 +462,6 @@ tcPatSynSig name sig_ty
         mkSpecForAllTys ex $
         mkPhiTy prov $
         body
-tcPatSynSig _ (XHsImplicitBndrs nec) = noExtCon nec
 
 ppr_tvs :: [TyVar] -> SDoc
 ppr_tvs tvs = braces (vcat [ ppr tv <+> dcolon <+> ppr (tyVarKind tv)
diff --git a/compiler/GHC/Tc/Gen/Splice.hs b/compiler/GHC/Tc/Gen/Splice.hs
index 3de1e2063d..f60f6682d2 100644
--- a/compiler/GHC/Tc/Gen/Splice.hs
+++ b/compiler/GHC/Tc/Gen/Splice.hs
@@ -274,7 +274,6 @@ brackTy b =
     (PatBr {})  -> mkTy patTyConName  -- Result type is m Pat
     (DecBrL {}) -> panic "tcBrackTy: Unexpected DecBrL"
     (TExpBr {}) -> panic "tcUntypedBracket: Unexpected TExpBr"
-    (XBracket nec) -> noExtCon nec
 
 ---------------
 -- | Typechecking a pending splice from a untyped bracket