Remove HasSrcSpan (#17494)

Metric Decrease:
    haddock.compiler

6 files changed, 132 insertions, 137 deletions

diff --git a/compiler/GHC/Hs/Expr.hs b/compiler/GHC/Hs/Expr.hs
index 8a8eb775cd..9955efaeb1 100644
--- a/compiler/GHC/Hs/Expr.hs
+++ b/compiler/GHC/Hs/Expr.hs
@@ -920,7 +920,7 @@ ppr_expr (SectionR _ op expr)
 ppr_expr (ExplicitTuple _ exprs boxity)
     -- Special-case unary boxed tuples so that they are pretty-printed as
     -- `Unit x`, not `(x)`
-  | [dL -> L _ (Present _ expr)] <- exprs
+  | [L _ (Present _ expr)] <- exprs
   , Boxed <- boxity
   = hsep [text (mkTupleStr Boxed 1), ppr expr]
   | otherwise
diff --git a/compiler/GHC/Hs/Pat.hs b/compiler/GHC/Hs/Pat.hs
index cae7144a8c..d8ae451ee9 100644
--- a/compiler/GHC/Hs/Pat.hs
+++ b/compiler/GHC/Hs/Pat.hs
@@ -710,7 +710,7 @@ isIrrefutableHsPat
 
     go (ConPatIn {})       = False     -- Conservative
     go (ConPatOut
-        { pat_con  = (dL->L _ (RealDataCon con))
+        { pat_con  = L _ (RealDataCon con)
         , pat_args = details })
                            =
       isJust (tyConSingleDataCon_maybe (dataConTyCon con))
@@ -718,9 +718,8 @@ isIrrefutableHsPat
       -- the latter is false of existentials. See #4439
       && all goL (hsConPatArgs details)
     go (ConPatOut
-        { pat_con = (dL->L _ (PatSynCon _pat)) })
+        { pat_con = L _ (PatSynCon _pat) })
                            = False -- Conservative
-    go (ConPatOut{})       = panic "ConPatOut:Impossible Match" -- due to #15884
     go (LitPat {})         = False
     go (NPat {})           = False
     go (NPlusKPat {})      = False
@@ -790,8 +789,8 @@ conPatNeedsParens p = go
 -- | @'parenthesizePat' p pat@ checks if @'patNeedsParens' p pat@ is true, and
 -- if so, surrounds @pat@ with a 'ParPat'. Otherwise, it simply returns @pat@.
 parenthesizePat :: PprPrec -> LPat (GhcPass p) -> LPat (GhcPass p)
-parenthesizePat p lpat@(dL->L loc pat)
-  | patNeedsParens p pat = cL loc (ParPat noExtField lpat)
+parenthesizePat p lpat@(L loc pat)
+  | patNeedsParens p pat = L loc (ParPat noExtField lpat)
   | otherwise            = lpat
 
 {-
diff --git a/compiler/GHC/Hs/Types.hs b/compiler/GHC/Hs/Types.hs
index 7af0a1ee4e..e92928c78f 100644
--- a/compiler/GHC/Hs/Types.hs
+++ b/compiler/GHC/Hs/Types.hs
@@ -1063,14 +1063,14 @@ hsAllLTyVarNames (HsQTvs { hsq_ext = kvs
 hsAllLTyVarNames (XLHsQTyVars nec) = noExtCon nec
 
 hsLTyVarLocName :: LHsTyVarBndr (GhcPass p) -> Located (IdP (GhcPass p))
-hsLTyVarLocName = onHasSrcSpan hsTyVarName
+hsLTyVarLocName = mapLoc hsTyVarName
 
 hsLTyVarLocNames :: LHsQTyVars (GhcPass p) -> [Located (IdP (GhcPass p))]
 hsLTyVarLocNames qtvs = map hsLTyVarLocName (hsQTvExplicit qtvs)
 
 -- | Convert a LHsTyVarBndr to an equivalent LHsType.
 hsLTyVarBndrToType :: LHsTyVarBndr (GhcPass p) -> LHsType (GhcPass p)
-hsLTyVarBndrToType = onHasSrcSpan cvt
+hsLTyVarBndrToType = mapLoc cvt
   where cvt (UserTyVar _ n) = HsTyVar noExtField NotPromoted n
         cvt (KindedTyVar _ (L name_loc n) kind)
           = HsKindSig noExtField
diff --git a/compiler/GHC/Hs/Utils.hs b/compiler/GHC/Hs/Utils.hs
index bac4dff9d9..b0d66c66d3 100644
--- a/compiler/GHC/Hs/Utils.hs
+++ b/compiler/GHC/Hs/Utils.hs
@@ -147,13 +147,13 @@ just attach 'noSrcSpan' to everything.
 
 -- | e => (e)
 mkHsPar :: LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
-mkHsPar e = cL (getLoc e) (HsPar noExtField e)
+mkHsPar e = L (getLoc e) (HsPar noExtField e)
 
 mkSimpleMatch :: HsMatchContext (NameOrRdrName (IdP (GhcPass p)))
               -> [LPat (GhcPass p)] -> Located (body (GhcPass p))
               -> LMatch (GhcPass p) (Located (body (GhcPass p)))
 mkSimpleMatch ctxt pats rhs
-  = cL loc $
+  = L loc $
     Match { m_ext = noExtField, m_ctxt = ctxt, m_pats = pats
           , m_grhss = unguardedGRHSs rhs }
   where
@@ -163,12 +163,12 @@ mkSimpleMatch ctxt pats rhs
 
 unguardedGRHSs :: Located (body (GhcPass p))
                -> GRHSs (GhcPass p) (Located (body (GhcPass p)))
-unguardedGRHSs rhs@(dL->L loc _)
+unguardedGRHSs rhs@(L loc _)
   = GRHSs noExtField (unguardedRHS loc rhs) (noLoc emptyLocalBinds)
 
 unguardedRHS :: SrcSpan -> Located (body (GhcPass p))
              -> [LGRHS (GhcPass p) (Located (body (GhcPass p)))]
-unguardedRHS loc rhs = [cL loc (GRHS noExtField [] rhs)]
+unguardedRHS loc rhs = [L loc (GRHS noExtField [] rhs)]
 
 mkMatchGroup :: (XMG name (Located (body name)) ~ NoExtField)
              => Origin -> [LMatch name (Located (body name))]
@@ -179,7 +179,7 @@ mkMatchGroup origin matches = MG { mg_ext = noExtField
 
 mkLocatedList ::  [Located a] -> Located [Located a]
 mkLocatedList [] = noLoc []
-mkLocatedList ms = cL (combineLocs (head ms) (last ms)) ms
+mkLocatedList ms = L (combineLocs (head ms) (last ms)) ms
 
 mkHsApp :: LHsExpr (GhcPass id) -> LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
 mkHsApp e1 e2 = addCLoc e1 e2 (HsApp noExtField e1 e2)
@@ -196,7 +196,7 @@ mkHsAppTypes = foldl' mkHsAppType
 
 mkHsLam :: (XMG (GhcPass p) (LHsExpr (GhcPass p)) ~ NoExtField) =>
   [LPat (GhcPass p)] -> LHsExpr (GhcPass p) -> LHsExpr (GhcPass p)
-mkHsLam pats body = mkHsPar (cL (getLoc body) (HsLam noExtField matches))
+mkHsLam pats body = mkHsPar (L (getLoc body) (HsLam noExtField matches))
   where
     matches = mkMatchGroup Generated
                            [mkSimpleMatch LambdaExpr pats' body]
@@ -225,13 +225,13 @@ nlHsTyApps fun_id tys xs = foldl' nlHsApp (nlHsTyApp fun_id tys) xs
 -- | Wrap in parens if (hsExprNeedsParens appPrec) says it needs them
 -- So   'f x'  becomes '(f x)', but '3' stays as '3'
 mkLHsPar :: LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
-mkLHsPar le@(dL->L loc e)
-  | hsExprNeedsParens appPrec e = cL loc (HsPar noExtField le)
+mkLHsPar le@(L loc e)
+  | hsExprNeedsParens appPrec e = L loc (HsPar noExtField le)
   | otherwise                   = le
 
 mkParPat :: LPat (GhcPass name) -> LPat (GhcPass name)
-mkParPat lp@(dL->L loc p)
-  | patNeedsParens appPrec p = cL loc (ParPat noExtField lp)
+mkParPat lp@(L loc p)
+  | patNeedsParens appPrec p = L loc (ParPat noExtField lp)
   | otherwise                = lp
 
 nlParPat :: LPat (GhcPass name) -> LPat (GhcPass name)
@@ -277,7 +277,7 @@ mkHsIsString src s  = OverLit noExtField (HsIsString   src s) noExpr
 mkHsDo ctxt stmts = HsDo noExtField ctxt (mkLocatedList stmts)
 mkHsComp ctxt stmts expr = mkHsDo ctxt (stmts ++ [last_stmt])
   where
-    last_stmt = cL (getLoc expr) $ mkLastStmt expr
+    last_stmt = L (getLoc expr) $ mkLastStmt expr
 
 mkHsIf :: LHsExpr (GhcPass p) -> LHsExpr (GhcPass p) -> LHsExpr (GhcPass p)
        -> HsExpr (GhcPass p)
@@ -531,7 +531,7 @@ missingTupArg = Missing noExtField
 mkLHsPatTup :: [LPat GhcRn] -> LPat GhcRn
 mkLHsPatTup []     = noLoc $ TuplePat noExtField [] Boxed
 mkLHsPatTup [lpat] = lpat
-mkLHsPatTup lpats  = cL (getLoc (head lpats)) $ TuplePat noExtField lpats Boxed
+mkLHsPatTup lpats  = L (getLoc (head lpats)) $ TuplePat noExtField lpats Boxed
 
 -- | The Big equivalents for the source tuple expressions
 mkBigLHsVarTup :: [IdP (GhcPass id)] -> LHsExpr (GhcPass id)
@@ -620,12 +620,12 @@ mkHsSigEnv get_info sigs
    -- of which use this function
   where
     (gen_dm_sigs, ordinary_sigs) = partition is_gen_dm_sig sigs
-    is_gen_dm_sig (dL->L _ (ClassOpSig _ True _ _)) = True
-    is_gen_dm_sig _                                 = False
+    is_gen_dm_sig (L _ (ClassOpSig _ True _ _)) = True
+    is_gen_dm_sig _                             = False
 
     mk_pairs :: [LSig GhcRn] -> [(Name, a)]
     mk_pairs sigs = [ (n,a) | Just (ns,a) <- map get_info sigs
-                            , (dL->L _ n) <- ns ]
+                            , L _ n <- ns ]
 
 mkClassOpSigs :: [LSig GhcPs] -> [LSig GhcPs]
 -- ^ Convert TypeSig to ClassOpSig
@@ -634,8 +634,8 @@ mkClassOpSigs :: [LSig GhcPs] -> [LSig GhcPs]
 mkClassOpSigs sigs
   = map fiddle sigs
   where
-    fiddle (dL->L loc (TypeSig _ nms ty))
-      = cL loc (ClassOpSig noExtField False nms (dropWildCards ty))
+    fiddle (L loc (TypeSig _ nms ty))
+      = L loc (ClassOpSig noExtField False nms (dropWildCards ty))
     fiddle sig = sig
 
 typeToLHsType :: Type -> LHsType GhcPs
@@ -753,7 +753,7 @@ positions in the kind of the tycon.
 ********************************************************************* -}
 
 mkLHsWrap :: HsWrapper -> LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
-mkLHsWrap co_fn (dL->L loc e) = cL loc (mkHsWrap co_fn e)
+mkLHsWrap co_fn (L loc e) = L loc (mkHsWrap co_fn e)
 
 -- | Avoid (HsWrap co (HsWrap co' _)).
 -- See Note [Detecting forced eta expansion] in DsExpr
@@ -771,14 +771,14 @@ mkHsWrapCoR :: TcCoercionR   -- A Representational coercion  a ~R b
 mkHsWrapCoR co e = mkHsWrap (mkWpCastR co) e
 
 mkLHsWrapCo :: TcCoercionN -> LHsExpr (GhcPass id) -> LHsExpr (GhcPass id)
-mkLHsWrapCo co (dL->L loc e) = cL loc (mkHsWrapCo co e)
+mkLHsWrapCo co (L loc e) = L loc (mkHsWrapCo co e)
 
 mkHsCmdWrap :: HsWrapper -> HsCmd (GhcPass p) -> HsCmd (GhcPass p)
 mkHsCmdWrap w cmd | isIdHsWrapper w = cmd
                   | otherwise       = HsCmdWrap noExtField w cmd
 
 mkLHsCmdWrap :: HsWrapper -> LHsCmd (GhcPass p) -> LHsCmd (GhcPass p)
-mkLHsCmdWrap w (dL->L loc c) = cL loc (mkHsCmdWrap w c)
+mkLHsCmdWrap w (L loc c) = L loc (mkHsCmdWrap w c)
 
 mkHsWrapPat :: HsWrapper -> Pat (GhcPass id) -> Type -> Pat (GhcPass id)
 mkHsWrapPat co_fn p ty | isIdHsWrapper co_fn = p
@@ -824,7 +824,7 @@ mkHsVarBind :: SrcSpan -> RdrName -> LHsExpr GhcPs -> LHsBind GhcPs
 mkHsVarBind loc var rhs = mkSimpleGeneratedFunBind loc var [] rhs
 
 mkVarBind :: IdP (GhcPass p) -> LHsExpr (GhcPass p) -> LHsBind (GhcPass p)
-mkVarBind var rhs = cL (getLoc rhs) $
+mkVarBind var rhs = L (getLoc rhs) $
                     VarBind { var_ext = noExtField,
                               var_id = var, var_rhs = rhs, var_inline = False }
 
@@ -852,8 +852,8 @@ isInfixFunBind _ = False
 mkSimpleGeneratedFunBind :: SrcSpan -> RdrName -> [LPat GhcPs]
                 -> LHsExpr GhcPs -> LHsBind GhcPs
 mkSimpleGeneratedFunBind loc fun pats expr
-  = cL loc $ mkFunBind Generated (cL loc fun)
-              [mkMatch (mkPrefixFunRhs (cL loc fun)) pats expr
+  = L loc $ mkFunBind Generated (L loc fun)
+              [mkMatch (mkPrefixFunRhs (L loc fun)) pats expr
                        (noLoc emptyLocalBinds)]
 
 -- | Make a prefix, non-strict function 'HsMatchContext'
@@ -873,8 +873,8 @@ mkMatch ctxt pats expr lbinds
                  , m_pats  = map paren pats
                  , m_grhss = GRHSs noExtField (unguardedRHS noSrcSpan expr) lbinds })
   where
-    paren lp@(dL->L l p)
-      | patNeedsParens appPrec p = cL l (ParPat noExtField lp)
+    paren lp@(L l p)
+      | patNeedsParens appPrec p = L l (ParPat noExtField lp)
       | otherwise                = lp
 
 {-
@@ -954,7 +954,7 @@ isBangedHsBind :: HsBind GhcTc -> Bool
 isBangedHsBind (AbsBinds { abs_binds = binds })
   = anyBag (isBangedHsBind . unLoc) binds
 isBangedHsBind (FunBind {fun_matches = matches})
-  | [dL->L _ match] <- unLoc $ mg_alts matches
+  | [L _ match] <- unLoc $ mg_alts matches
   , FunRhs{mc_strictness = SrcStrict} <- m_ctxt match
   = True
 isBangedHsBind (PatBind {pat_lhs = pat})
@@ -976,8 +976,8 @@ collectHsIdBinders, collectHsValBinders
 collectHsIdBinders  = collect_hs_val_binders True
 collectHsValBinders = collect_hs_val_binders False
 
-collectHsBindBinders :: (SrcSpanLess (LPat p) ~ Pat p, HasSrcSpan (LPat p))=>
-                        HsBindLR p idR -> [IdP p]
+collectHsBindBinders :: XRec pass Pat ~ Located (Pat pass) =>
+                        HsBindLR pass idR -> [IdP pass]
 -- ^ Collect both Ids and pattern-synonym binders
 collectHsBindBinders b = collect_bind False b []
 
@@ -1003,16 +1003,17 @@ collect_binds :: Bool -> LHsBindsLR (GhcPass p) idR ->
 -- ^ Collect Ids, or Ids + pattern synonyms, depending on boolean flag
 collect_binds ps binds acc = foldr (collect_bind ps . unLoc) acc binds
 
-collect_bind :: (SrcSpanLess (LPat p) ~ Pat p , HasSrcSpan (LPat p)) =>
-                Bool -> HsBindLR p idR -> [IdP p] -> [IdP p]
+collect_bind :: XRec pass Pat ~ Located (Pat pass) =>
+                Bool -> HsBindLR pass idR ->
+                [IdP pass] -> [IdP pass]
 collect_bind _ (PatBind { pat_lhs = p })           acc = collect_lpat p acc
-collect_bind _ (FunBind { fun_id = (dL->L _ f) })  acc = f : acc
+collect_bind _ (FunBind { fun_id = L _ f })        acc = f : acc
 collect_bind _ (VarBind { var_id = f })            acc = f : acc
 collect_bind _ (AbsBinds { abs_exports = dbinds }) acc = map abe_poly dbinds ++ acc
         -- I don't think we want the binders from the abe_binds
 
         -- binding (hence see AbsBinds) is in zonking in TcHsSyn
-collect_bind omitPatSyn (PatSynBind _ (PSB { psb_id = (dL->L _ ps) })) acc
+collect_bind omitPatSyn (PatSynBind _ (PSB { psb_id = L _ ps })) acc
   | omitPatSyn                  = acc
   | otherwise                   = ps : acc
 collect_bind _ (PatSynBind _ (XPatSynBind _)) acc = acc
@@ -1066,8 +1067,8 @@ collectPatsBinders :: [LPat (GhcPass p)] -> [IdP (GhcPass p)]
 collectPatsBinders pats = foldr collect_lpat [] pats
 
 -------------
-collect_lpat :: (SrcSpanLess (LPat p) ~ Pat p , HasSrcSpan (LPat p)) =>
-                 LPat p -> [IdP p] -> [IdP p]
+collect_lpat :: XRec pass Pat ~ Located (Pat pass) =>
+                LPat pass -> [IdP pass] -> [IdP pass]
 collect_lpat p bndrs
   = go (unLoc p)
   where
@@ -1160,39 +1161,37 @@ hsLTyClDeclBinders :: Located (TyClDecl (GhcPass p))
 -- Each returned (Located name) has a SrcSpan for the /whole/ declaration.
 -- See Note [SrcSpan for binders]
 
-hsLTyClDeclBinders (dL->L loc (FamDecl { tcdFam = FamilyDecl
-                                            { fdLName = (dL->L _ name) } }))
-  = ([cL loc name], [])
-hsLTyClDeclBinders (dL->L _ (FamDecl { tcdFam = XFamilyDecl nec }))
+hsLTyClDeclBinders (L loc (FamDecl { tcdFam = FamilyDecl
+                                            { fdLName = (L _ name) } }))
+  = ([L loc name], [])
+hsLTyClDeclBinders (L _ (FamDecl { tcdFam = XFamilyDecl nec }))
   = noExtCon nec
-hsLTyClDeclBinders (dL->L loc (SynDecl
-                               { tcdLName = (dL->L _ name) }))
-  = ([cL loc name], [])
-hsLTyClDeclBinders (dL->L loc (ClassDecl
-                               { tcdLName = (dL->L _ cls_name)
+hsLTyClDeclBinders (L loc (SynDecl
+                               { tcdLName = (L _ name) }))
+  = ([L loc name], [])
+hsLTyClDeclBinders (L loc (ClassDecl
+                               { tcdLName = (L _ cls_name)
                                , tcdSigs  = sigs
                                , tcdATs   = ats }))
-  = (cL loc cls_name :
-     [ cL fam_loc fam_name | (dL->L fam_loc (FamilyDecl
+  = (L loc cls_name :
+     [ L fam_loc fam_name | (L fam_loc (FamilyDecl
                                         { fdLName = L _ fam_name })) <- ats ]
      ++
-     [ cL mem_loc mem_name | (dL->L mem_loc (ClassOpSig _ False ns _)) <- sigs
-                           , (dL->L _ mem_name) <- ns ]
+     [ L mem_loc mem_name | (L mem_loc (ClassOpSig _ False ns _)) <- sigs
+                          , (L _ mem_name) <- ns ]
     , [])
-hsLTyClDeclBinders (dL->L loc (DataDecl    { tcdLName = (dL->L _ name)
-                                           , tcdDataDefn = defn }))
-  = (\ (xs, ys) -> (cL loc name : xs, ys)) $ hsDataDefnBinders defn
-hsLTyClDeclBinders (dL->L _ (XTyClDecl nec)) = noExtCon nec
-hsLTyClDeclBinders _ = panic "hsLTyClDeclBinders: Impossible Match"
-                             -- due to #15884
+hsLTyClDeclBinders (L loc (DataDecl    { tcdLName = (L _ name)
+                                       , tcdDataDefn = defn }))
+  = (\ (xs, ys) -> (L loc name : xs, ys)) $ hsDataDefnBinders defn
+hsLTyClDeclBinders (L _ (XTyClDecl nec)) = noExtCon nec
 
 
 -------------------
 hsForeignDeclsBinders :: [LForeignDecl pass] -> [Located (IdP pass)]
 -- ^ See Note [SrcSpan for binders]
 hsForeignDeclsBinders foreign_decls
-  = [ cL decl_loc n
-    | (dL->L decl_loc (ForeignImport { fd_name = (dL->L _ n) }))
+  = [ L decl_loc n
+    | L decl_loc (ForeignImport { fd_name = L _ n })
         <- foreign_decls]
 
 
@@ -1213,24 +1212,22 @@ addPatSynSelector bind sels
 getPatSynBinds :: [(RecFlag, LHsBinds id)] -> [PatSynBind id id]
 getPatSynBinds binds
   = [ psb | (_, lbinds) <- binds
-          , (dL->L _ (PatSynBind _ psb)) <- bagToList lbinds ]
+          , L _ (PatSynBind _ psb) <- bagToList lbinds ]
 
 -------------------
 hsLInstDeclBinders :: LInstDecl (GhcPass p)
                    -> ([Located (IdP (GhcPass p))], [LFieldOcc (GhcPass p)])
-hsLInstDeclBinders (dL->L _ (ClsInstD
+hsLInstDeclBinders (L _ (ClsInstD
                              { cid_inst = ClsInstDecl
                                           { cid_datafam_insts = dfis }}))
   = foldMap (hsDataFamInstBinders . unLoc) dfis
-hsLInstDeclBinders (dL->L _ (DataFamInstD { dfid_inst = fi }))
+hsLInstDeclBinders (L _ (DataFamInstD { dfid_inst = fi }))
   = hsDataFamInstBinders fi
-hsLInstDeclBinders (dL->L _ (TyFamInstD {})) = mempty
-hsLInstDeclBinders (dL->L _ (ClsInstD _ (XClsInstDecl nec)))
+hsLInstDeclBinders (L _ (TyFamInstD {})) = mempty
+hsLInstDeclBinders (L _ (ClsInstD _ (XClsInstDecl nec)))
   = noExtCon nec
-hsLInstDeclBinders (dL->L _ (XInstDecl nec))
+hsLInstDeclBinders (L _ (XInstDecl nec))
   = noExtCon nec
-hsLInstDeclBinders _ = panic "hsLInstDeclBinders: Impossible Match"
-                             -- due to #15884
 
 -------------------
 -- | the SrcLoc returned are for the whole declarations, not just the names
@@ -1278,13 +1275,13 @@ hsConDeclsBinders cons
            -- remove only the first occurrence of any seen field in order to
            -- avoid circumventing detection of duplicate fields (#9156)
            ConDeclGADT { con_names = names, con_args = args }
-             -> (map (cL loc . unLoc) names ++ ns, flds ++ fs)
+             -> (map (L loc . unLoc) names ++ ns, flds ++ fs)
              where
                 (remSeen', flds) = get_flds remSeen args
                 (ns, fs) = go remSeen' rs
 
            ConDeclH98 { con_name = name, con_args = args }
-             -> ([cL loc (unLoc name)] ++ ns, flds ++ fs)
+             -> ([L loc (unLoc name)] ++ ns, flds ++ fs)
              where
                 (remSeen', flds) = get_flds remSeen args
                 (ns, fs) = go remSeen' rs
diff --git a/compiler/GHC/HsToCore/PmCheck.hs b/compiler/GHC/HsToCore/PmCheck.hs
index 1467ef07f4..86a9717c02 100644
--- a/compiler/GHC/HsToCore/PmCheck.hs
+++ b/compiler/GHC/HsToCore/PmCheck.hs
@@ -282,7 +282,7 @@ checkSingle' locn var p = do
     (Covered   , _          ) -> plain                              -- useful
     (NotCovered, NotDiverged) -> plain { pmresultRedundant = m    } -- redundant
     (NotCovered, Diverged   ) -> plain { pmresultInaccessible = m } -- inaccessible rhs
-  where m = [cL locn [cL locn p]]
+  where m = [L locn [L locn p]]
 
 -- | Exhaustive for guard matches, is used for guards in pattern bindings and
 -- in @MultiIf@ expressions.
@@ -293,7 +293,7 @@ checkGuardMatches hs_ctx guards@(GRHSs _ grhss _) = do
     dflags <- getDynFlags
     let combinedLoc = foldl1 combineSrcSpans (map getLoc grhss)
         dsMatchContext = DsMatchContext hs_ctx combinedLoc
-        match = cL combinedLoc $
+        match = L combinedLoc $
                   Match { m_ext = noExtField
                         , m_ctxt = hs_ctx
                         , m_pats = []
@@ -360,8 +360,8 @@ checkMatches' vars matches = do
         (NotCovered, Diverged )   -> (rs, final_u, m:is, pc1 Semi.<> pc2)
 
     hsLMatchToLPats :: LMatch id body -> Located [LPat id]
-    hsLMatchToLPats (dL->L l (Match { m_pats = pats })) = cL l pats
-    hsLMatchToLPats _                                   = panic "checkMatches'"
+    hsLMatchToLPats (L l (Match { m_pats = pats })) = L l pats
+    hsLMatchToLPats _                               = panic "checkMatches'"
 
 getNFirstUncovered :: [Id] -> Int -> [Delta] -> DsM [Delta]
 getNFirstUncovered _    0 _              = pure []
@@ -465,7 +465,7 @@ translatePat fam_insts x pat = case pat of
 
   -- (x@pat)   ==>   Translate pat with x as match var and handle impedance
   --                 mismatch with incoming match var
-  AsPat _ (dL->L _ y) p -> (mkPmLetVar y x ++) <$> translateLPat fam_insts y p
+  AsPat _ (L _ y) p -> (mkPmLetVar y x ++) <$> translateLPat fam_insts y p
 
   SigPat _ p _ty -> translateLPat fam_insts x p
 
@@ -481,7 +481,7 @@ translatePat fam_insts x pat = case pat of
         pure (PmLet y (wrap_rhs_y (Var x)) : grds)
 
   -- (n + k)  ===>   let b = x >= k, True <- b, let n = x-k
-  NPlusKPat _pat_ty (dL->L _ n) k1 k2 ge minus -> do
+  NPlusKPat _pat_ty (L _ n) k1 k2 ge minus -> do
     b <- mkPmId boolTy
     let grd_b = vanillaConGrd b trueDataCon []
     [ke1, ke2] <- traverse dsOverLit [unLoc k1, k2]
@@ -527,14 +527,14 @@ translatePat fam_insts x pat = case pat of
     --
     -- See #14547, especially comment#9 and comment#10.
 
-  ConPatOut { pat_con     = (dL->L _ con)
+  ConPatOut { pat_con     = L _ con
             , pat_arg_tys = arg_tys
             , pat_tvs     = ex_tvs
             , pat_dicts   = dicts
             , pat_args    = ps } -> do
     translateConPatOut fam_insts x con arg_tys ex_tvs dicts ps
 
-  NPat ty (dL->L _ olit) mb_neg _ -> do
+  NPat ty (L _ olit) mb_neg _ -> do
     -- See Note [Literal short cut] in MatchLit.hs
     -- We inline the Literal short cut for @ty@ here, because @ty@ is more
     -- precise than the field of OverLitTc, which is all that dsOverLit (which
@@ -657,7 +657,7 @@ translateConPatOut fam_insts x con univ_tys ex_tvs dicts = \case
 -- Translate a single match
 translateMatch :: FamInstEnvs -> [Id] -> LMatch GhcTc (LHsExpr GhcTc)
                -> DsM (GrdVec, [GrdVec])
-translateMatch fam_insts vars (dL->L _ (Match { m_pats = pats, m_grhss = grhss }))
+translateMatch fam_insts vars (L _ (Match { m_pats = pats, m_grhss = grhss }))
   = do
       pats'   <- concat <$> zipWithM (translateLPat fam_insts) vars pats
       guards' <- mapM (translateGuards fam_insts) guards
@@ -665,8 +665,8 @@ translateMatch fam_insts vars (dL->L _ (Match { m_pats = pats, m_grhss = grhss }
       return (pats', guards')
       where
         extractGuards :: LGRHS GhcTc (LHsExpr GhcTc) -> [GuardStmt GhcTc]
-        extractGuards (dL->L _ (GRHS _ gs _)) = map unLoc gs
-        extractGuards _                       = panic "translateMatch"
+        extractGuards (L _ (GRHS _ gs _)) = map unLoc gs
+        extractGuards _                   = panic "translateMatch"
 
         guards = map extractGuards (grhssGRHSs grhss)
 translateMatch _ _ _ = panic "translateMatch"
@@ -1247,10 +1247,10 @@ dsPmWarn dflags ctx@(DsMatchContext kind loc) vars pm_result
       when (approx && (exists_u || exists_i)) $
         putSrcSpanDs loc (warnDs NoReason approx_msg)
 
-      when exists_r $ forM_ redundant $ \(dL->L l q) -> do
+      when exists_r $ forM_ redundant $ \(L l q) -> do
         putSrcSpanDs l (warnDs (Reason Opt_WarnOverlappingPatterns)
                                (pprEqn q "is redundant"))
-      when exists_i $ forM_ inaccessible $ \(dL->L l q) -> do
+      when exists_i $ forM_ inaccessible $ \(L l q) -> do
         putSrcSpanDs l (warnDs (Reason Opt_WarnOverlappingPatterns)
                                (pprEqn q "has inaccessible right hand side"))
       when exists_u $ putSrcSpanDs loc $ warnDs flag_u_reason $
@@ -1366,7 +1366,7 @@ pprContext singular (DsMatchContext kind _loc) msg rest_of_msg_fun
 
     (ppr_match, pref)
         = case kind of
-             FunRhs { mc_fun = (dL->L _ fun) }
+             FunRhs { mc_fun = L _ fun }
                   -> (pprMatchContext kind, \ pp -> ppr fun <+> pp)
              _    -> (pprMatchContext kind, \ pp -> pp)
 
diff --git a/compiler/GHC/ThToHs.hs b/compiler/GHC/ThToHs.hs
index eb38d36319..2a813344df 100644
--- a/compiler/GHC/ThToHs.hs
+++ b/compiler/GHC/ThToHs.hs
@@ -118,15 +118,14 @@ getL = CvtM (\_ loc -> Right (loc,loc))
 setL :: SrcSpan -> CvtM ()
 setL loc = CvtM (\_ _ -> Right (loc, ()))
 
-returnL :: HasSrcSpan a => SrcSpanLess a -> CvtM a
-returnL x = CvtM (\_ loc -> Right (loc, cL loc x))
+returnL :: a -> CvtM (Located a)
+returnL x = CvtM (\_ loc -> Right (loc, L loc x))
 
-returnJustL :: HasSrcSpan a => SrcSpanLess a -> CvtM (Maybe a)
+returnJustL :: a -> CvtM (Maybe (Located a))
 returnJustL = fmap Just . returnL
 
-wrapParL :: HasSrcSpan a =>
-            (a -> SrcSpanLess a) -> SrcSpanLess a -> CvtM (SrcSpanLess  a)
-wrapParL add_par x = CvtM (\_ loc -> Right (loc, add_par (cL loc x)))
+wrapParL :: (Located a -> a) -> a -> CvtM a
+wrapParL add_par x = CvtM (\_ loc -> Right (loc, add_par (L loc x)))
 
 wrapMsg :: (Show a, TH.Ppr a) => String -> a -> CvtM b -> CvtM b
 -- E.g  wrapMsg "declaration" dec thing
@@ -142,10 +141,10 @@ wrapMsg what item (CvtM m)
                     then text (show item)
                     else text (pprint item))
 
-wrapL :: HasSrcSpan a => CvtM (SrcSpanLess a) -> CvtM a
+wrapL :: CvtM a -> CvtM (Located a)
 wrapL (CvtM m) = CvtM $ \origin loc -> case m origin loc of
   Left err -> Left err
-  Right (loc',v) -> Right (loc',cL loc v)
+  Right (loc', v) -> Right (loc', L loc v)
 
 -------------------------------------------------------------------
 cvtDecs :: [TH.Dec] -> CvtM [LHsDecl GhcPs]
@@ -279,14 +278,14 @@ cvtDec (InstanceD o ctxt ty decs)
         ; (binds', sigs', fams', ats', adts') <- cvt_ci_decs doc decs
         ; unless (null fams') (failWith (mkBadDecMsg doc fams'))
         ; ctxt' <- cvtContext funPrec ctxt
-        ; (dL->L loc ty') <- cvtType ty
-        ; let inst_ty' = mkHsQualTy ctxt loc ctxt' $ cL loc ty'
+        ; (L loc ty') <- cvtType ty
+        ; let inst_ty' = mkHsQualTy ctxt loc ctxt' $ L loc ty'
         ; returnJustL $ InstD noExtField $ ClsInstD noExtField $
           ClsInstDecl { cid_ext = noExtField, cid_poly_ty = mkLHsSigType inst_ty'
                       , cid_binds = binds'
                       , cid_sigs = Hs.mkClassOpSigs sigs'
                       , cid_tyfam_insts = ats', cid_datafam_insts = adts'
-                      , cid_overlap_mode = fmap (cL loc . overlap) o } }
+                      , cid_overlap_mode = fmap (L loc . overlap) o } }
   where
   overlap pragma =
     case pragma of
@@ -350,7 +349,7 @@ cvtDec (NewtypeInstD ctxt bndrs tys ksig constr derivs)
                                   , feqn_fixity = Prefix } }}}
 
 cvtDec (TySynInstD eqn)
-  = do  { (dL->L _ eqn') <- cvtTySynEqn eqn
+  = do  { (L _ eqn') <- cvtTySynEqn eqn
         ; returnJustL $ InstD noExtField $ TyFamInstD
             { tfid_ext = noExtField
             , tfid_inst = TyFamInstDecl { tfid_eqn = eqn' } } }
@@ -376,8 +375,8 @@ cvtDec (TH.RoleAnnotD tc roles)
 cvtDec (TH.StandaloneDerivD ds cxt ty)
   = do { cxt' <- cvtContext funPrec cxt
        ; ds'  <- traverse cvtDerivStrategy ds
-       ; (dL->L loc ty') <- cvtType ty
-       ; let inst_ty' = mkHsQualTy cxt loc cxt' $ cL loc ty'
+       ; (L loc ty') <- cvtType ty
+       ; let inst_ty' = mkHsQualTy cxt loc cxt' $ L loc ty'
        ; returnJustL $ DerivD noExtField $
          DerivDecl { deriv_ext =noExtField
                    , deriv_strategy = ds'
@@ -523,29 +522,29 @@ cvt_tyfam_head (TypeFamilyHead tc tyvars result injectivity)
 -------------------------------------------------------------------
 
 is_fam_decl :: LHsDecl GhcPs -> Either (LFamilyDecl GhcPs) (LHsDecl GhcPs)
-is_fam_decl (dL->L loc (TyClD _ (FamDecl { tcdFam = d }))) = Left (cL loc d)
+is_fam_decl (L loc (TyClD _ (FamDecl { tcdFam = d }))) = Left (L loc d)
 is_fam_decl decl = Right decl
 
 is_tyfam_inst :: LHsDecl GhcPs -> Either (LTyFamInstDecl GhcPs) (LHsDecl GhcPs)
-is_tyfam_inst (dL->L loc (Hs.InstD _ (TyFamInstD { tfid_inst = d })))
-  = Left (cL loc d)
+is_tyfam_inst (L loc (Hs.InstD _ (TyFamInstD { tfid_inst = d })))
+  = Left (L loc d)
 is_tyfam_inst decl
   = Right decl
 
 is_datafam_inst :: LHsDecl GhcPs
                 -> Either (LDataFamInstDecl GhcPs) (LHsDecl GhcPs)
-is_datafam_inst (dL->L loc (Hs.InstD  _ (DataFamInstD { dfid_inst = d })))
-  = Left (cL loc d)
+is_datafam_inst (L loc (Hs.InstD  _ (DataFamInstD { dfid_inst = d })))
+  = Left (L loc d)
 is_datafam_inst decl
   = Right decl
 
 is_sig :: LHsDecl GhcPs -> Either (LSig GhcPs) (LHsDecl GhcPs)
-is_sig (dL->L loc (Hs.SigD _ sig)) = Left (cL loc sig)
-is_sig decl                        = Right decl
+is_sig (L loc (Hs.SigD _ sig)) = Left (L loc sig)
+is_sig decl                    = Right decl
 
 is_bind :: LHsDecl GhcPs -> Either (LHsBind GhcPs) (LHsDecl GhcPs)
-is_bind (dL->L loc (Hs.ValD _ bind)) = Left (cL loc bind)
-is_bind decl                         = Right decl
+is_bind (L loc (Hs.ValD _ bind)) = Left (L loc bind)
+is_bind decl                     = Right decl
 
 is_ip_bind :: TH.Dec -> Either (String, TH.Exp) TH.Dec
 is_ip_bind (TH.ImplicitParamBindD n e) = Left (n, e)
@@ -582,12 +581,12 @@ cvtConstr (InfixC st1 c st2)
 cvtConstr (ForallC tvs ctxt con)
   = do  { tvs'      <- cvtTvs tvs
         ; ctxt'     <- cvtContext funPrec ctxt
-        ; (dL->L _ con')  <- cvtConstr con
+        ; L _ con'  <- cvtConstr con
         ; returnL $ add_forall tvs' ctxt' con' }
   where
     add_cxt lcxt         Nothing           = Just lcxt
-    add_cxt (dL->L loc cxt1) (Just (dL->L _ cxt2))
-      = Just (cL loc (cxt1 ++ cxt2))
+    add_cxt (L loc cxt1) (Just (L _ cxt2))
+      = Just (L loc (cxt1 ++ cxt2))
 
     add_forall tvs' cxt' con@(ConDeclGADT { con_qvars = qvars, con_mb_cxt = cxt })
       = con { con_forall = noLoc $ not (null all_tvs)
@@ -611,7 +610,7 @@ cvtConstr (GadtC [] _strtys _ty)
 cvtConstr (GadtC c strtys ty)
   = do  { c'      <- mapM cNameL c
         ; args    <- mapM cvt_arg strtys
-        ; (dL->L _ ty') <- cvtType ty
+        ; L _ ty' <- cvtType ty
         ; c_ty    <- mk_arr_apps args ty'
         ; returnL $ fst $ mkGadtDecl c' c_ty}
 
@@ -646,12 +645,12 @@ cvt_arg (Bang su ss, ty)
 
 cvt_id_arg :: (TH.Name, TH.Bang, TH.Type) -> CvtM (LConDeclField GhcPs)
 cvt_id_arg (i, str, ty)
-  = do  { (dL->L li i') <- vNameL i
+  = do  { L li i' <- vNameL i
         ; ty' <- cvt_arg (str,ty)
         ; return $ noLoc (ConDeclField
                           { cd_fld_ext = noExtField
                           , cd_fld_names
-                              = [cL li $ FieldOcc noExtField (cL li i')]
+                              = [L li $ FieldOcc noExtField (L li i')]
                           , cd_fld_type =  ty'
                           , cd_fld_doc = Nothing}) }
 
@@ -1132,8 +1131,8 @@ cvtHsDo do_or_lc stmts
         ; let Just (stmts'', last') = snocView stmts'
 
         ; last'' <- case last' of
-                    (dL->L loc (BodyStmt _ body _ _))
-                      -> return (cL loc (mkLastStmt body))
+                    (L loc (BodyStmt _ body _ _))
+                      -> return (L loc (mkLastStmt body))
                     _ -> failWith (bad_last last')
 
         ; return $ HsDo noExtField do_or_lc (noLoc (stmts'' ++ [last''])) }
@@ -1162,8 +1161,8 @@ cvtMatch :: HsMatchContext RdrName
 cvtMatch ctxt (TH.Match p body decs)
   = do  { p' <- cvtPat p
         ; let lp = case p' of
-                     (dL->L loc SigPat{}) -> cL loc (ParPat noExtField p') -- #14875
-                     _                    -> p'
+                     (L loc SigPat{}) -> L loc (ParPat noExtField p') -- #14875
+                     _                -> p'
         ; g' <- cvtGuard body
         ; decs' <- cvtLocalDecs (text "a where clause") decs
         ; returnL $ Hs.Match noExtField ctxt [lp] (GRHSs noExtField g' (noLoc decs')) }
@@ -1298,10 +1297,10 @@ cvtp (ViewP e p)       = do { e' <- cvtl e; p' <- cvtPat p
 
 cvtPatFld :: (TH.Name, TH.Pat) -> CvtM (LHsRecField GhcPs (LPat GhcPs))
 cvtPatFld (s,p)
-  = do  { (dL->L ls s') <- vNameL s
+  = do  { L ls s' <- vNameL s
         ; p' <- cvtPat p
         ; return (noLoc $ HsRecField { hsRecFieldLbl
-                                         = cL ls $ mkFieldOcc (cL ls s')
+                                         = L ls $ mkFieldOcc (L ls s')
                                      , hsRecFieldArg = p'
                                      , hsRecPun      = False}) }
 
@@ -1503,7 +1502,7 @@ cvtTypeKind ty_str ty
            PromotedConsT  -- See Note [Representing concrete syntax in types]
                           -- in Language.Haskell.TH.Syntax
               | Just normals <- m_normals
-              , [ty1, dL->L _ (HsExplicitListTy _ ip tys2)] <- normals
+              , [ty1, L _ (HsExplicitListTy _ ip tys2)] <- normals
               -> do
                   returnL (HsExplicitListTy noExtField ip (ty1:tys2))
               | otherwise
@@ -1576,7 +1575,7 @@ mk_apps head_ty type_args = do
   go type_args
    where
     -- See Note [Adding parens for splices]
-    add_parens lt@(dL->L _ t)
+    add_parens lt@(L _ t)
       | hsTypeNeedsParens appPrec t = returnL (HsParTy noExtField lt)
       | otherwise                   = return lt
 
@@ -1680,9 +1679,9 @@ cvtPatSynSigTy (ForallT univs reqs (ForallT exis provs ty))
   | null exis, null provs = cvtType (ForallT univs reqs ty)
   | null univs, null reqs = do { l   <- getL
                                ; ty' <- cvtType (ForallT exis provs ty)
-                               ; return $ cL l (HsQualTy { hst_ctxt = cL l []
-                                                         , hst_xqual = noExtField
-                                                         , hst_body = ty' }) }
+                               ; return $ L l (HsQualTy { hst_ctxt = L l []
+                                                        , hst_xqual = noExtField
+                                                        , hst_body = ty' }) }
   | null reqs             = do { l      <- getL
                                ; univs' <- hsQTvExplicit <$> cvtTvs univs
                                ; ty'    <- cvtType (ForallT exis provs ty)
@@ -1690,11 +1689,11 @@ cvtPatSynSigTy (ForallT univs reqs (ForallT exis provs ty))
                                               { hst_fvf = ForallInvis
                                               , hst_bndrs = univs'
                                               , hst_xforall = noExtField
-                                              , hst_body = cL l cxtTy }
-                                     cxtTy = HsQualTy { hst_ctxt = cL l []
+                                              , hst_body = L l cxtTy }
+                                     cxtTy = HsQualTy { hst_ctxt = L l []
                                                       , hst_xqual = noExtField
                                                       , hst_body = ty' }
-                               ; return $ cL l forTy }
+                               ; return $ L l forTy }
   | otherwise             = cvtType (ForallT univs reqs (ForallT exis provs ty))
 cvtPatSynSigTy ty         = cvtType ty
 
@@ -1753,10 +1752,10 @@ mkHsForAllTy :: [TH.TyVarBndr]
              -- ^ The complete type, quantified with a forall if necessary
 mkHsForAllTy tvs loc fvf tvs' rho_ty
   | null tvs  = rho_ty
-  | otherwise = cL loc $ HsForAllTy { hst_fvf = fvf
-                                    , hst_bndrs = hsQTvExplicit tvs'
-                                    , hst_xforall = noExtField
-                                    , hst_body = rho_ty }
+  | otherwise = L loc $ HsForAllTy { hst_fvf = fvf
+                                   , hst_bndrs = hsQTvExplicit tvs'
+                                   , hst_xforall = noExtField
+                                   , hst_body = rho_ty }
 
 -- | If passed an empty 'TH.Cxt', this simply returns the third argument
 -- (an 'LHsType'). Otherwise, return an 'HsQualTy' using the provided
@@ -1778,9 +1777,9 @@ mkHsQualTy :: TH.Cxt
            -- ^ The complete type, qualified with a context if necessary
 mkHsQualTy ctxt loc ctxt' ty
   | null ctxt = ty
-  | otherwise = cL loc $ HsQualTy { hst_xqual = noExtField
-                                  , hst_ctxt  = ctxt'
-                                  , hst_body  = ty }
+  | otherwise = L loc $ HsQualTy { hst_xqual = noExtField
+                                 , hst_ctxt  = ctxt'
+                                 , hst_body  = ty }
 
 --------------------------------------------------------------------
 --      Turning Name back into RdrName