Convert diagnostics in GHC.Rename.Module to proper TcRnMessage (#20115)

I've turned almost all occurrences of TcRnUnknownMessage in GHC.Rename.Module
module into a proper TcRnMessage.
Instead, these TcRnMessage messages were introduced:
  TcRnIllegalInstanceHeadDecl
  TcRnUnexpectedStandaloneDerivingDecl
  TcRnUnusedVariableInRuleDecl
  TcRnUnexpectedStandaloneKindSig
  TcRnIllegalRuleLhs
  TcRnBadAssocRhs
  TcRnDuplicateRoleAnnot
  TcRnDuplicateKindSig
  TcRnIllegalDerivStrategy
  TcRnIllegalMultipleDerivClauses
  TcRnNoDerivStratSpecified
  TcRnStupidThetaInGadt
  TcRnBadImplicitSplice
  TcRnShadowedTyVarNameInFamResult
  TcRnIncorrectTyVarOnLhsOfInjCond
  TcRnUnknownTyVarsOnRhsOfInjCond

Was introduced one helper type:
  RuleLhsErrReason

32 files changed, 525 insertions, 224 deletions

diff --git a/compiler/GHC/Rename/Module.hs b/compiler/GHC/Rename/Module.hs
index 5441d0419a..516966044c 100644
--- a/compiler/GHC/Rename/Module.hs
+++ b/compiler/GHC/Rename/Module.hs
@@ -38,7 +38,6 @@ import GHC.Rename.Utils ( mapFvRn, bindLocalNames
 import GHC.Rename.Unbound ( mkUnboundName, notInScopeErr, WhereLooking(WL_Global) )
 import GHC.Rename.Names
 import GHC.Tc.Errors.Types
-import GHC.Tc.Errors.Ppr (pprScopeError)
 import GHC.Tc.Gen.Annotation ( annCtxt )
 import GHC.Tc.Utils.Monad
 
@@ -56,7 +55,7 @@ import GHC.Types.Name.Env
 import GHC.Types.Avail
 import GHC.Utils.Outputable
 import GHC.Data.Bag
-import GHC.Types.Basic  ( pprRuleName, TypeOrKind(..) )
+import GHC.Types.Basic  ( TypeOrKind(..) )
 import GHC.Data.FastString
 import GHC.Types.SrcLoc as SrcLoc
 import GHC.Driver.Session
@@ -75,11 +74,9 @@ import Control.Monad
 import Control.Arrow ( first )
 import Data.Foldable ( toList )
 import Data.List ( mapAccumL )
-import qualified Data.List.NonEmpty as NE
 import Data.List.NonEmpty ( NonEmpty(..), head )
 import Data.Maybe ( isNothing, fromMaybe, mapMaybe )
 import qualified Data.Set as Set ( difference, fromList, toList, null )
-import Data.Function ( on )
 import GHC.Types.ConInfo (ConInfo, mkConInfo, conInfoFields)
 
 {- | @rnSourceDecl@ "renames" declarations.
@@ -619,14 +616,7 @@ rnClsInstDecl (ClsInstDecl { cid_poly_ty = inst_ty, cid_binds = mbinds
                Just (L _ cls) -> Right cls
                Nothing        -> Left
                  ( getLocA head_ty'
-                 , mkTcRnUnknownMessage $ mkPlainError noHints $
-                   hang (text "Illegal head of an instance declaration:"
-                           <+> quotes (ppr head_ty'))
-                      2 (vcat [ text "Instance heads must be of the form"
-                              , nest 2 $ text "C ty_1 ... ty_n"
-                              , text "where" <+> quotes (char 'C')
-                                <+> text "is a class"
-                              ])
+                 , TcRnIllegalInstanceHeadDecl head_ty'
                  )
          -- ...finally, attempt to retrieve the class type constructor, failing
          -- with an error message if there isn't one. To avoid excessive
@@ -798,7 +788,7 @@ rnFamEqn doc atfi extra_kvars
                && not (cls_tkv `elemNameSet` lhs_bound_vars)
                     -- ...but not bound on the LHS.
              bad_tvs = filter improperly_scoped inst_head_tvs
-       ; unless (null bad_tvs) (badAssocRhs bad_tvs)
+       ; unless (null bad_tvs) (addErr (TcRnBadAssocRhs bad_tvs))
 
        ; let eqn_fvs = rhs_fvs `plusFV` pat_fvs
              -- See Note [Type family equations and occurrences]
@@ -845,14 +835,6 @@ rnFamEqn doc atfi extra_kvars
       [loc]      -> loc
       (loc:locs) -> loc `combineSrcSpans` last locs
 
-    badAssocRhs :: [Name] -> RnM ()
-    badAssocRhs ns
-      = addErr $ mkTcRnUnknownMessage $ mkPlainError noHints $
-           (hang (text "The RHS of an associated type declaration mentions"
-                      <+> text "out-of-scope variable" <> plural ns
-                      <+> pprWithCommas (quotes . ppr) ns)
-                   2 (text "All such variables must be bound on the LHS"))
-
 rnTyFamInstDecl :: AssocTyFamInfo
                 -> TyFamInstDecl GhcPs
                 -> RnM (TyFamInstDecl GhcRn, FreeVars)
@@ -1190,7 +1172,7 @@ simplistic solution above, as it fixes the egregious bug in #18470.
 rnSrcDerivDecl :: DerivDecl GhcPs -> RnM (DerivDecl GhcRn, FreeVars)
 rnSrcDerivDecl (DerivDecl _ ty mds overlap)
   = do { standalone_deriv_ok <- xoptM LangExt.StandaloneDeriving
-       ; unless standalone_deriv_ok (addErr standaloneDerivErr)
+       ; unless standalone_deriv_ok (addErr TcRnUnexpectedStandaloneDerivingDecl)
        ; checkInferredVars ctxt inf_err nowc_ty
        ; (mds', ty', fvs) <- rnLDerivStrategy ctxt mds $ rnHsSigWcType ctxt ty
          -- Check if there are any nested `forall`s or contexts, which are
@@ -1208,12 +1190,6 @@ rnSrcDerivDecl (DerivDecl _ ty mds overlap)
     loc = getLocA nowc_ty
     nowc_ty = dropWildCards ty
 
-standaloneDerivErr :: TcRnMessage
-standaloneDerivErr
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    hang (text "Illegal standalone deriving declaration")
-       2 (text "Use StandaloneDeriving to enable this extension")
-
 {-
 *********************************************************
 *                                                      *
@@ -1316,7 +1292,7 @@ checkValidRule rule_name ids lhs' fv_lhs'
 
                 -- Check that LHS vars are all bound
         ; let bad_vars = [var | var <- ids, not (var `elemNameSet` fv_lhs')]
-        ; mapM_ (addErr . badRuleVar rule_name) bad_vars }
+        ; mapM_ (addErr . TcRnUnusedVariableInRuleDecl rule_name) bad_vars }
 
 validRuleLhs :: [Name] -> LHsExpr GhcRn -> Maybe (HsExpr GhcRn)
 -- Nothing => OK
@@ -1353,27 +1329,15 @@ validRuleLhs foralls lhs
     checkl_es es = foldr (mplus . checkl_e) Nothing es
 -}
 
-badRuleVar :: FastString -> Name -> TcRnMessage
-badRuleVar name var
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    sep [text "Rule" <+> doubleQuotes (ftext name) <> colon,
-         text "Forall'd variable" <+> quotes (ppr var) <+>
-                text "does not appear on left hand side"]
 
 badRuleLhsErr :: FastString -> LHsExpr GhcRn -> HsExpr GhcRn -> TcRnMessage
 badRuleLhsErr name lhs bad_e
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    sep [text "Rule" <+> pprRuleName name <> colon,
-         nest 2 (vcat [err,
-                       text "in left-hand side:" <+> ppr lhs])]
-    $$
-    text "LHS must be of form (f e1 .. en) where f is not forall'd"
+  = TcRnIllegalRuleLhs errReason name lhs bad_e
   where
-    err =
-      case bad_e of
-        HsUnboundVar _ uv ->
-          pprScopeError uv $ notInScopeErr WL_Global uv
-        _ -> text "Illegal expression:" <+> ppr bad_e
+    errReason = case bad_e of
+      HsUnboundVar _ uv ->
+        UnboundVariable uv $ notInScopeErr WL_Global uv
+      _ -> IllegalExpression
 
 {- **************************************************************
          *                                                      *
@@ -1618,17 +1582,12 @@ rnStandaloneKindSignature
   -> RnM (StandaloneKindSig GhcRn, FreeVars)
 rnStandaloneKindSignature tc_names (StandaloneKindSig _ v ki)
   = do  { standalone_ki_sig_ok <- xoptM LangExt.StandaloneKindSignatures
-        ; unless standalone_ki_sig_ok $ addErr standaloneKiSigErr
+        ; unless standalone_ki_sig_ok $ addErr TcRnUnexpectedStandaloneKindSig
         ; new_v <- lookupSigCtxtOccRnN (TopSigCtxt tc_names) (text "standalone kind signature") v
         ; let doc = StandaloneKindSigCtx (ppr v)
         ; (new_ki, fvs) <- rnHsSigType doc KindLevel ki
         ; return (StandaloneKindSig noExtField new_v new_ki, fvs)
         }
-  where
-    standaloneKiSigErr :: TcRnMessage
-    standaloneKiSigErr = mkTcRnUnknownMessage $ mkPlainError noHints $
-      hang (text "Illegal standalone kind signature")
-         2 (text "Did you mean to enable StandaloneKindSignatures?")
 
 depAnalTyClDecls :: GlobalRdrEnv
                  -> KindSig_FV_Env
@@ -1698,34 +1657,12 @@ rnRoleAnnots tc_names role_annots
            ; return $ RoleAnnotDecl noExtField tycon' roles }
 
 dupRoleAnnotErr :: NonEmpty (LRoleAnnotDecl GhcPs) -> RnM ()
-dupRoleAnnotErr list
-  = addErrAt (locA loc) $ mkTcRnUnknownMessage $ mkPlainError noHints $
-    hang (text "Duplicate role annotations for" <+>
-          quotes (ppr $ roleAnnotDeclName first_decl) <> colon)
-       2 (vcat $ map pp_role_annot $ NE.toList sorted_list)
-    where
-      sorted_list = NE.sortBy cmp_loc list
-      ((L loc first_decl) :| _) = sorted_list
-
-      pp_role_annot (L loc decl) = hang (ppr decl)
-                                      4 (text "-- written at" <+> ppr (locA loc))
-
-      cmp_loc = SrcLoc.leftmost_smallest `on` getLocA
+dupRoleAnnotErr list@(L loc _ :| _)
+  = addErrAt (locA loc) (TcRnDuplicateRoleAnnot list)
 
 dupKindSig_Err :: NonEmpty (LStandaloneKindSig GhcPs) -> RnM ()
-dupKindSig_Err list
-  = addErrAt (locA loc) $ mkTcRnUnknownMessage $ mkPlainError noHints $
-    hang (text "Duplicate standalone kind signatures for" <+>
-          quotes (ppr $ standaloneKindSigName first_decl) <> colon)
-       2 (vcat $ map pp_kisig $ NE.toList sorted_list)
-    where
-      sorted_list = NE.sortBy cmp_loc list
-      ((L loc first_decl) :| _) = sorted_list
-
-      pp_kisig (L loc decl) =
-        hang (ppr decl) 4 (text "-- written at" <+> ppr (locA loc))
-
-      cmp_loc = SrcLoc.leftmost_smallest `on` getLocA
+dupKindSig_Err list@(L loc _ :| _)
+  = addErrAt (locA loc) (TcRnDuplicateKindSig list)
 
 {- Note [Role annotations in the renamer]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1955,7 +1892,7 @@ rnDataDefn doc (HsDataDefn { dd_cType = cType, dd_ctxt = context, dd_cons = cond
   = do  { -- DatatypeContexts (i.e., stupid contexts) can't be combined with
           -- GADT syntax. See Note [The stupid context] in GHC.Core.DataCon.
           checkTc (h98_style || null (fromMaybeContext context))
-                  (badGadtStupidTheta doc)
+                  (TcRnStupidThetaInGadt doc)
 
         -- Check restrictions on "type data" declarations.
         -- See Note [Type data declarations].
@@ -1991,7 +1928,7 @@ rnDataDefn doc (HsDataDefn { dd_cType = cType, dd_ctxt = context, dd_cons = cond
     rn_derivs ds
       = do { deriv_strats_ok <- xoptM LangExt.DerivingStrategies
            ; failIfTc (lengthExceeds ds 1 && not deriv_strats_ok)
-               multipleDerivClausesErr
+               TcRnIllegalMultipleDerivClauses
            ; (ds', fvs) <- mapFvRn (rnLHsDerivingClause doc) ds
            ; return (ds', fvs) }
 
@@ -2213,21 +2150,10 @@ warnNoDerivStrat mds loc
   = do { dyn_flags <- getDynFlags
        ; case mds of
            Nothing ->
-             let dia = mkTcRnUnknownMessage $
-                   mkPlainDiagnostic (WarningWithFlag Opt_WarnMissingDerivingStrategies) noHints $
-                     (if xopt LangExt.DerivingStrategies dyn_flags
-                       then no_strat_warning
-                       else no_strat_warning $+$ deriv_strat_nenabled
-                     )
-             in addDiagnosticAt loc dia
+             addDiagnosticAt loc $ TcRnNoDerivStratSpecified
+              (xopt LangExt.DerivingStrategies dyn_flags)
            _ -> pure ()
        }
-  where
-    no_strat_warning :: SDoc
-    no_strat_warning = text "No deriving strategy specified. Did you want stock"
-                       <> text ", newtype, or anyclass?"
-    deriv_strat_nenabled :: SDoc
-    deriv_strat_nenabled = text "Use DerivingStrategies to specify a strategy."
 
 rnLHsDerivingClause :: HsDocContext -> LHsDerivingClause GhcPs
                     -> RnM (LHsDerivingClause GhcRn, FreeVars)
@@ -2291,7 +2217,7 @@ rnLDerivStrategy doc mds thing_inside
             = LangExt.DerivingStrategies
 
       unlessXOptM extNeeded $
-        failWith $ illegalDerivStrategyErr ds
+        failWith $ TcRnIllegalDerivStrategy ds
 
       case ds of
         StockStrategy    _ -> boring_case (StockStrategy noExtField)
@@ -2319,32 +2245,6 @@ rnLDerivStrategy doc mds thing_inside
       (thing, fvs) <- thing_inside
       pure (ds, thing, fvs)
 
-badGadtStupidTheta :: HsDocContext -> TcRnMessage
-badGadtStupidTheta _
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    vcat [text "No context is allowed on a GADT-style data declaration",
-          text "(You can put a context on each constructor, though.)"]
-
-illegalDerivStrategyErr :: DerivStrategy GhcPs -> TcRnMessage
-illegalDerivStrategyErr ds
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    vcat [ text "Illegal deriving strategy" <> colon <+> derivStrategyName ds
-         , text enableStrategy ]
-
-  where
-    enableStrategy :: String
-    enableStrategy
-      | ViaStrategy{} <- ds
-      = "Use DerivingVia to enable this extension"
-      | otherwise
-      = "Use DerivingStrategies to enable this extension"
-
-multipleDerivClausesErr :: TcRnMessage
-multipleDerivClausesErr
-  = mkTcRnUnknownMessage $ mkPlainError noHints $
-    vcat [ text "Illegal use of multiple, consecutive deriving clauses"
-         , text "Use DerivingStrategies to allow this" ]
-
 rnFamDecl :: Maybe Name -- Just cls => this FamilyDecl is nested
                         --             inside an *class decl* for cls
                         --             used for associated types
@@ -2407,11 +2307,8 @@ rnFamResultSig doc (TyVarSig _ tvbndr)
           rdr_env <- getLocalRdrEnv
        ;  let resName = hsLTyVarName tvbndr
        ;  when (resName `elemLocalRdrEnv` rdr_env) $
-          addErrAt (getLocA tvbndr) $ mkTcRnUnknownMessage $ mkPlainError noHints $
-                     (hsep [ text "Type variable", quotes (ppr resName) <> comma
-                           , text "naming a type family result,"
-                           ] $$
-                      text "shadows an already bound type variable")
+          addErrAt (getLocA tvbndr) $
+            TcRnShadowedTyVarNameInFamResult resName
 
        ; bindLHsTyVarBndr doc Nothing -- This might be a lie, but it's used for
                                       -- scoping checks that are irrelevant here
@@ -2481,20 +2378,13 @@ rnInjectivityAnn tvBndrs (L _ (TyVarSig _ resTv))
    -- not-in-scope variables) don't check the validity of injectivity
    -- annotation. This gives better error messages.
    ; when (noRnErrors && not lhsValid) $
-        addErrAt (getLocA injFrom) $ mkTcRnUnknownMessage $ mkPlainError noHints $
-              ( vcat [ text $ "Incorrect type variable on the LHS of "
-                           ++ "injectivity condition"
-              , nest 5
-              ( vcat [ text "Expected :" <+> ppr resName
-                     , text "Actual   :" <+> ppr injFrom ])])
+        addErrAt (getLocA injFrom) $
+          TcRnIncorrectTyVarOnLhsOfInjCond resName injFrom
 
    ; when (noRnErrors && not (Set.null rhsValid)) $
       do { let errorVars = Set.toList rhsValid
-         ; addErrAt (locA srcSpan) $ mkTcRnUnknownMessage $ mkPlainError noHints $
-                        ( hsep
-                        [ text "Unknown type variable" <> plural errorVars
-                        , text "on the RHS of injectivity condition:"
-                        , interpp'SP errorVars ] ) }
+         ; addErrAt (locA srcSpan) $
+              TcRnUnknownTyVarsOnRhsOfInjCond errorVars }
 
    ; return injDecl' }
 
@@ -2783,9 +2673,7 @@ add gp loc (SpliceD _ splice@(SpliceDecl _ _ flag)) ds
        ; return (gp, Just (splice, ds)) }
   where
     badImplicitSplice :: TcRnMessage
-    badImplicitSplice = mkTcRnUnknownMessage $ mkPlainError noHints $
-                        text "Parse error: module header, import declaration"
-                     $$ text "or top-level declaration expected."
+    badImplicitSplice = TcRnBadImplicitSplice
                      -- The compiler should suggest the above, and not using
                      -- TemplateHaskell since the former suggestion is more
                      -- relevant to the larger base of users.
diff --git a/compiler/GHC/Tc/Errors/Ppr.hs b/compiler/GHC/Tc/Errors/Ppr.hs
index a9b9718433..a800b451c9 100644
--- a/compiler/GHC/Tc/Errors/Ppr.hs
+++ b/compiler/GHC/Tc/Errors/Ppr.hs
@@ -1324,6 +1324,88 @@ instance Diagnostic TcRnMessage where
           = vcat [ text "Starting from GHC 9.10, this warning will turn into an error." ]
         user_manual =
           vcat [ text "See the user manual, § Undecidable instances and loopy superclasses." ]
+    TcRnIllegalInstanceHeadDecl head_ty -> mkSimpleDecorated $
+      hang (text "Illegal head of an instance declaration:"
+              <+> quotes (ppr head_ty))
+        2 (vcat [ text "Instance heads must be of the form"
+                , nest 2 $ text "C ty_1 ... ty_n"
+                , text "where" <+> quotes (char 'C')
+                  <+> text "is a class"
+                ])
+    TcRnUnexpectedStandaloneDerivingDecl -> mkSimpleDecorated $
+      text "Illegal standalone deriving declaration"
+    TcRnUnusedVariableInRuleDecl name var -> mkSimpleDecorated $
+      sep [text "Rule" <+> doubleQuotes (ftext name) <> colon,
+          text "Forall'd variable" <+> quotes (ppr var) <+>
+                  text "does not appear on left hand side"]
+    TcRnUnexpectedStandaloneKindSig -> mkSimpleDecorated $
+      text "Illegal standalone kind signature"
+    TcRnIllegalRuleLhs errReason name lhs bad_e -> mkSimpleDecorated $
+      sep [text "Rule" <+> pprRuleName name <> colon,
+           nest 2 (vcat [err,
+                         text "in left-hand side:" <+> ppr lhs])]
+      $$
+      text "LHS must be of form (f e1 .. en) where f is not forall'd"
+      where
+        err = case errReason of
+          UnboundVariable uv nis -> pprScopeError uv nis
+          IllegalExpression -> text "Illegal expression:" <+> ppr bad_e
+    TcRnBadAssocRhs ns -> mkSimpleDecorated $
+      hang (text "The RHS of an associated type declaration mentions"
+                <+> text "out-of-scope variable" <> plural ns
+                <+> pprWithCommas (quotes . ppr) ns)
+              2 (text "All such variables must be bound on the LHS")
+    TcRnDuplicateRoleAnnot list -> mkSimpleDecorated $
+      hang (text "Duplicate role annotations for" <+>
+            quotes (ppr $ roleAnnotDeclName first_decl) <> colon)
+        2 (vcat $ map pp_role_annot $ NE.toList sorted_list)
+      where
+        sorted_list = NE.sortBy cmp_loc list
+        ((L _ first_decl) :| _) = sorted_list
+
+        pp_role_annot (L loc decl) = hang (ppr decl)
+                                        4 (text "-- written at" <+> ppr (locA loc))
+
+        cmp_loc = leftmost_smallest `on` getLocA
+    TcRnDuplicateKindSig list -> mkSimpleDecorated $
+      hang (text "Duplicate standalone kind signatures for" <+>
+            quotes (ppr $ standaloneKindSigName first_decl) <> colon)
+        2 (vcat $ map pp_kisig $ NE.toList sorted_list)
+      where
+        sorted_list = NE.sortBy cmp_loc list
+        ((L _ first_decl) :| _) = sorted_list
+
+        pp_kisig (L loc decl) =
+          hang (ppr decl) 4 (text "-- written at" <+> ppr (locA loc))
+
+        cmp_loc = leftmost_smallest `on` getLocA
+    TcRnIllegalDerivStrategy ds -> mkSimpleDecorated $
+      text "Illegal deriving strategy" <> colon <+> derivStrategyName ds
+    TcRnIllegalMultipleDerivClauses -> mkSimpleDecorated $
+      text "Illegal use of multiple, consecutive deriving clauses"
+    TcRnNoDerivStratSpecified{} -> mkSimpleDecorated $ text
+      "No deriving strategy specified. Did you want stock, newtype, or anyclass?"
+    TcRnStupidThetaInGadt{} -> mkSimpleDecorated $
+      vcat [text "No context is allowed on a GADT-style data declaration",
+            text "(You can put a context on each constructor, though.)"]
+    TcRnBadImplicitSplice -> mkSimpleDecorated $
+         text "Parse error: module header, import declaration"
+      $$ text "or top-level declaration expected."
+    TcRnShadowedTyVarNameInFamResult resName -> mkSimpleDecorated $
+       hsep [ text "Type variable", quotes (ppr resName) <> comma
+            , text "naming a type family result,"
+            ] $$
+      text "shadows an already bound type variable"
+    TcRnIncorrectTyVarOnLhsOfInjCond resName injFrom -> mkSimpleDecorated $
+        vcat [ text $ "Incorrect type variable on the LHS of "
+                   ++ "injectivity condition"
+      , nest 5
+      ( vcat [ text "Expected :" <+> ppr resName
+             , text "Actual   :" <+> ppr injFrom ])]
+    TcRnUnknownTyVarsOnRhsOfInjCond errorVars -> mkSimpleDecorated $
+      hsep [ text "Unknown type variable" <> plural errorVars
+           , text "on the RHS of injectivity condition:"
+           , interpp'SP errorVars ]
 
   diagnosticReason = \case
     TcRnUnknownMessage m
@@ -1756,6 +1838,38 @@ instance Diagnostic TcRnMessage where
       -> ErrorWithoutFlag
     TcRnLoopySuperclassSolve{}
       -> WarningWithFlag Opt_WarnLoopySuperclassSolve
+    TcRnIllegalInstanceHeadDecl{}
+      -> ErrorWithoutFlag
+    TcRnUnexpectedStandaloneDerivingDecl{}
+      -> ErrorWithoutFlag
+    TcRnUnusedVariableInRuleDecl{}
+      -> ErrorWithoutFlag
+    TcRnUnexpectedStandaloneKindSig{}
+      -> ErrorWithoutFlag
+    TcRnIllegalRuleLhs{}
+      -> ErrorWithoutFlag
+    TcRnBadAssocRhs{}
+      -> ErrorWithoutFlag
+    TcRnDuplicateRoleAnnot{}
+      -> ErrorWithoutFlag
+    TcRnDuplicateKindSig{}
+      -> ErrorWithoutFlag
+    TcRnIllegalDerivStrategy{}
+      -> ErrorWithoutFlag
+    TcRnIllegalMultipleDerivClauses{}
+      -> ErrorWithoutFlag
+    TcRnNoDerivStratSpecified{}
+      -> WarningWithFlag Opt_WarnMissingDerivingStrategies
+    TcRnStupidThetaInGadt{}
+      -> ErrorWithoutFlag
+    TcRnBadImplicitSplice{}
+      -> ErrorWithoutFlag
+    TcRnShadowedTyVarNameInFamResult{}
+      -> ErrorWithoutFlag
+    TcRnIncorrectTyVarOnLhsOfInjCond{}
+      -> ErrorWithoutFlag
+    TcRnUnknownTyVarsOnRhsOfInjCond{}
+      -> ErrorWithoutFlag
 
   diagnosticHints = \case
     TcRnUnknownMessage m
@@ -2204,6 +2318,40 @@ instance Diagnostic TcRnMessage where
         cls_or_qc = case ctLocOrigin wtd_loc of
           ScOrigin c_or_q _ -> c_or_q
           _                 -> IsClsInst -- shouldn't happen
+    TcRnIllegalInstanceHeadDecl{}
+      -> noHints
+    TcRnUnexpectedStandaloneDerivingDecl{}
+      -> [suggestExtension LangExt.StandaloneDeriving]
+    TcRnUnusedVariableInRuleDecl{}
+      -> noHints
+    TcRnUnexpectedStandaloneKindSig{}
+      -> [suggestExtension LangExt.StandaloneKindSignatures]
+    TcRnIllegalRuleLhs{}
+      -> noHints
+    TcRnBadAssocRhs{}
+      -> noHints
+    TcRnDuplicateRoleAnnot{}
+      -> noHints
+    TcRnDuplicateKindSig{}
+      -> noHints
+    TcRnIllegalDerivStrategy ds -> case ds of
+      ViaStrategy{} -> [suggestExtension LangExt.DerivingVia]
+      _ -> [suggestExtension LangExt.DerivingStrategies]
+    TcRnIllegalMultipleDerivClauses{}
+      -> [suggestExtension LangExt.DerivingStrategies]
+    TcRnNoDerivStratSpecified isDSEnabled -> if isDSEnabled
+      then noHints
+      else [suggestExtension LangExt.DerivingStrategies]
+    TcRnStupidThetaInGadt{}
+      -> noHints
+    TcRnBadImplicitSplice{}
+      -> noHints
+    TcRnShadowedTyVarNameInFamResult{}
+      -> noHints
+    TcRnIncorrectTyVarOnLhsOfInjCond{}
+      -> noHints
+    TcRnUnknownTyVarsOnRhsOfInjCond{}
+      -> noHints
 
   diagnosticCode = constructorCode
 
diff --git a/compiler/GHC/Tc/Errors/Types.hs b/compiler/GHC/Tc/Errors/Types.hs
index 108eba5ab0..82d749e4ea 100644
--- a/compiler/GHC/Tc/Errors/Types.hs
+++ b/compiler/GHC/Tc/Errors/Types.hs
@@ -90,6 +90,7 @@ module GHC.Tc.Errors.Types (
   , UnexpectedStatement(..)
   , DeclSort(..)
   , NonStandardGuards(..)
+  , RuleLhsErrReason(..)
   ) where
 
 import GHC.Prelude
@@ -2959,6 +2960,224 @@ data TcRnMessage where
                            -> PredType -- ^ Wanted 'PredType'
                            -> TcRnMessage
 
+  {-| TcRnIllegalInstanceHeadDecl is an error triggered by malformed head of
+      type class instance
+
+      Examples:
+
+        instance 42
+
+        instance !Show D
+
+      Test cases: parser/should_fail/T3811c
+                  rename/should_fail/T18240a
+  -}
+  TcRnIllegalInstanceHeadDecl :: LHsType GhcRn -> TcRnMessage
+
+  {-| TcRnUnexpectedStandaloneDerivingDecl is an error thrown when a user uses
+      standalone deriving without enabling the StandaloneDeriving extension.
+
+      Example:
+
+        deriving instance Eq Foo
+
+      Test cases: rename/should_fail/RnUnexpectedStandaloneDeriving
+  -}
+  TcRnUnexpectedStandaloneDerivingDecl :: TcRnMessage
+
+  {-| TcRnUnusedVariableInRuleDecl is an error triggered by forall'd variable in
+      rewrite rule that does not appear on left-hand side
+
+      Example:
+
+        {-# RULES "rule" forall a. id = id #-}
+
+      Test cases: rename/should_fail/ExplicitForAllRules2
+  -}
+  TcRnUnusedVariableInRuleDecl :: FastString -> Name -> TcRnMessage
+
+  {-| TcRnUnexpectedStandaloneKindSig is an error thrown when a user uses standalone
+      kind signature without enabling the StandaloneKindSignatures extension.
+
+      Example:
+
+        type D :: Type
+        data D = D
+
+      Test cases: saks/should_fail/saks_fail001
+  -}
+  TcRnUnexpectedStandaloneKindSig :: TcRnMessage
+
+  {-| TcRnIllegalRuleLhs is an error triggered by malformed left-hand side
+      of rewrite rule
+
+      Examples:
+
+        {-# RULES "test" forall x. f x = x #-}
+
+        {-# RULES "test" forall x. case x of = x #-}
+
+      Test cases: rename/should_fail/T15659
+  -}
+  TcRnIllegalRuleLhs
+    :: RuleLhsErrReason
+    -> FastString -- Rule name
+    -> LHsExpr GhcRn -- Full expression
+    -> HsExpr GhcRn -- Bad expression
+    -> TcRnMessage
+
+  {-| TcRnBadAssocRhs is an error triggered by out-of-scope type variables
+      occurred in right-hand side of an associated type declaration
+
+      Example:
+
+        instance forall a. C Int where
+          data instance D Int = MkD1 a
+
+       cases: indexed-types/should_fail/T5515
+                  polykinds/T9574
+                  rename/should_fail/T18021
+  -}
+  TcRnBadAssocRhs :: [Name] -> TcRnMessage
+
+  {-| TcRnDuplicateRoleAnnot is an error triggered by two or more role
+      annotations for one type
+
+      Example:
+
+        data D a
+        type role D phantom
+        type role D phantom
+
+      Test cases: roles/should_fail/Roles8
+  -}
+  TcRnDuplicateRoleAnnot :: NE.NonEmpty (LRoleAnnotDecl GhcPs) -> TcRnMessage
+
+  {-| TcRnDuplicateKindSig is an error triggered by two or more standalone
+      kind signatures for one type
+
+      Example:
+
+        type D :: Type
+        type D :: Type
+        data D
+
+      Test cases: saks/should_fail/saks_fail002
+  -}
+  TcRnDuplicateKindSig :: NE.NonEmpty (LStandaloneKindSig GhcPs) -> TcRnMessage
+
+  {-| TcRnIllegalDerivStrategy  is an error thrown when a user uses deriving
+      strategy without enabling the DerivingStrategies extension or uses deriving
+      via without enabling the DerivingVia extension.
+
+      Examples:
+
+        data T = T deriving stock Eq
+
+        data T = T deriving via Eq T
+
+      Test cases: deriving/should_fail/deriving-via-fail3
+                  deriving/should_fail/T10598_fail4
+  -}
+  TcRnIllegalDerivStrategy :: DerivStrategy GhcPs -> TcRnMessage
+
+  {-| TcRnIllegalMultipleDerivClauses is an error thrown when a user uses two or more
+      deriving clauses without enabling the DerivingStrategies extension.
+
+      Example:
+
+        data T = T
+          deriving Eq
+          deriving Ord
+
+      Test cases: deriving/should_fail/T10598_fail5
+  -}
+  TcRnIllegalMultipleDerivClauses :: TcRnMessage
+
+  {-| TcRnNoDerivStratSpecified is a warning implied by -Wmissing-deriving-strategies
+      and triggered by deriving clause without specified deriving strategy.
+
+      Example:
+
+        data T = T
+          deriving Eq
+
+      Test cases: rename/should_compile/T15798a
+                  rename/should_compile/T15798b
+                  rename/should_compile/T15798c
+  -}
+  TcRnNoDerivStratSpecified
+    :: Bool -- True if DerivingStrategies is enabled
+    -> TcRnMessage
+
+  {-| TcRnStupidThetaInGadt is an error triggered by data contexts in GADT-style
+      data declaration
+
+      Example:
+
+        data (Eq a) => D a where
+          MkD :: D Int
+
+      Test cases: rename/should_fail/RnStupidThetaInGadt
+  -}
+  TcRnStupidThetaInGadt :: HsDocContext -> TcRnMessage
+
+  {-| TcRnBadImplicitSplice is an error thrown when a user uses top-level implicit
+      TH-splice without enabling the TemplateHaskell extension.
+
+      Example:
+
+        pure [] -- on top-level
+
+      Test cases: ghci/prog019/prog019
+                  ghci/scripts/T1914
+                  ghci/scripts/T6106
+                  rename/should_fail/T4042
+                  rename/should_fail/T12146
+  -}
+  TcRnBadImplicitSplice :: TcRnMessage
+
+  {-| TcRnShadowedTyVarNameInFamResult is an error triggered by type variable in
+      type family result that shadows type variable from left hand side
+
+      Example:
+
+        type family F a b c = b
+
+      Test cases: ghci/scripts/T6018ghcirnfail
+                  rename/should_fail/T6018rnfail
+  -}
+  TcRnShadowedTyVarNameInFamResult :: IdP GhcPs -> TcRnMessage
+
+  {-| TcRnIncorrectTyVarOnRhsOfInjCond is an error caused by a situation where the
+      left-hand side of an injectivity condition of a type family is not a variable
+      referring to the type family result.
+      See Note [Renaming injectivity annotation] for more details.
+
+      Example:
+
+        type family F a = r | a -> a
+
+      Test cases: ghci/scripts/T6018ghcirnfail
+                  rename/should_fail/T6018rnfail
+  -}
+  TcRnIncorrectTyVarOnLhsOfInjCond
+    :: IdP GhcRn -- Expected
+    -> LIdP GhcPs -- Actual
+    -> TcRnMessage
+
+  {-| TcRnUnknownTyVarsOnRhsOfInjCond is an error triggered by out-of-scope type
+      variables on the right-hand side of a of an injectivity condition of a type family
+
+      Example:
+
+        type family F a = res | res -> b
+
+      Test cases: ghci/scripts/T6018ghcirnfail
+                  rename/should_fail/T6018rnfail
+  -}
+  TcRnUnknownTyVarsOnRhsOfInjCond :: [Name] -> TcRnMessage
+
   deriving Generic
 
 -- | Things forbidden in @type data@ declarations.
@@ -4196,3 +4415,7 @@ data NonStandardGuards where
         Anno (Stmt GhcRn body) ~ SrcSpanAnnA)
     => [LStmtLR GhcRn GhcRn body]
     -> NonStandardGuards
+
+data RuleLhsErrReason
+  = UnboundVariable RdrName NotInScopeError
+  | IllegalExpression
diff --git a/compiler/GHC/Types/Error/Codes.hs b/compiler/GHC/Types/Error/Codes.hs
index 9d3fe30084..dca0923ce7 100644
--- a/compiler/GHC/Types/Error/Codes.hs
+++ b/compiler/GHC/Types/Error/Codes.hs
@@ -514,6 +514,22 @@ type family GhcDiagnosticCode c = n | n -> c where
   GhcDiagnosticCode "TcRnBindInBootFile"                            = 11247
   GhcDiagnosticCode "TcRnDuplicateMinimalSig"                       = 85346
   GhcDiagnosticCode "TcRnLoopySuperclassSolve"                      = 36038
+  GhcDiagnosticCode "TcRnIllegalInstanceHeadDecl"                   = 12222
+  GhcDiagnosticCode "TcRnUnexpectedStandaloneDerivingDecl"          = 95159
+  GhcDiagnosticCode "TcRnUnusedVariableInRuleDecl"                  = 65669
+  GhcDiagnosticCode "TcRnUnexpectedStandaloneKindSig"               = 45906
+  GhcDiagnosticCode "TcRnIllegalRuleLhs"                            = 63294
+  GhcDiagnosticCode "TcRnBadAssocRhs"                               = 53634
+  GhcDiagnosticCode "TcRnDuplicateRoleAnnot"                        = 97170
+  GhcDiagnosticCode "TcRnDuplicateKindSig"                          = 43371
+  GhcDiagnosticCode "TcRnIllegalDerivStrategy"                      = 87139
+  GhcDiagnosticCode "TcRnIllegalMultipleDerivClauses"               = 30281
+  GhcDiagnosticCode "TcRnNoDerivStratSpecified"                     = 55631
+  GhcDiagnosticCode "TcRnStupidThetaInGadt"                         = 18403
+  GhcDiagnosticCode "TcRnBadImplicitSplice"                         = 25277
+  GhcDiagnosticCode "TcRnShadowedTyVarNameInFamResult"              = 99412
+  GhcDiagnosticCode "TcRnIncorrectTyVarOnLhsOfInjCond"              = 88333
+  GhcDiagnosticCode "TcRnUnknownTyVarsOnRhsOfInjCond"               = 48254
 
   -- IllegalNewtypeReason
   GhcDiagnosticCode "DoesNotHaveSingleField"                        = 23517
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail4.stderr b/testsuite/tests/deriving/should_fail/T10598_fail4.stderr
index e5447d9489..ce6a1cd4d8 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail4.stderr
+++ b/testsuite/tests/deriving/should_fail/T10598_fail4.stderr
@@ -1,4 +1,4 @@
 
-T10598_fail4.hs:4:12: error:
+T10598_fail4.hs:4:12: error: [GHC-87139]
     Illegal deriving strategy: stock
-    Use DerivingStrategies to enable this extension
+    Suggested fix: Perhaps you intended to use DerivingStrategies
diff --git a/testsuite/tests/deriving/should_fail/T10598_fail5.stderr b/testsuite/tests/deriving/should_fail/T10598_fail5.stderr
index af38cdcc51..b6b3877d32 100644
--- a/testsuite/tests/deriving/should_fail/T10598_fail5.stderr
+++ b/testsuite/tests/deriving/should_fail/T10598_fail5.stderr
@@ -1,4 +1,4 @@
 
-T10598_fail5.hs:3:1: error:
+T10598_fail5.hs:3:1: error: [GHC-30281]
     Illegal use of multiple, consecutive deriving clauses
-    Use DerivingStrategies to allow this
+    Suggested fix: Perhaps you intended to use DerivingStrategies
diff --git a/testsuite/tests/deriving/should_fail/deriving-via-fail3.stderr b/testsuite/tests/deriving/should_fail/deriving-via-fail3.stderr
index 43c395e5cd..b2fb98469a 100644
--- a/testsuite/tests/deriving/should_fail/deriving-via-fail3.stderr
+++ b/testsuite/tests/deriving/should_fail/deriving-via-fail3.stderr
@@ -1,4 +1,4 @@
 
-deriving-via-fail3.hs:3:20: error:
+deriving-via-fail3.hs:3:20: error: [GHC-87139]
     Illegal deriving strategy: via
-    Use DerivingVia to enable this extension
+    Suggested fix: Perhaps you intended to use DerivingVia
diff --git a/testsuite/tests/ghci/prog019/prog019.stderr b/testsuite/tests/ghci/prog019/prog019.stderr
index 2a6fd015e4..208cbd6087 100644
--- a/testsuite/tests/ghci/prog019/prog019.stderr
+++ b/testsuite/tests/ghci/prog019/prog019.stderr
@@ -1,8 +1,8 @@
 
-B2.hs:3:1: error:
+B2.hs:3:1: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
 
-D.hs:3:1: error:
+D.hs:3:1: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
diff --git a/testsuite/tests/ghci/scripts/T1914.stderr b/testsuite/tests/ghci/scripts/T1914.stderr
index 6dd83fab58..1344f3ce04 100644
--- a/testsuite/tests/ghci/scripts/T1914.stderr
+++ b/testsuite/tests/ghci/scripts/T1914.stderr
@@ -1,4 +1,4 @@
 
-T1914A.hs:1:38:
+T1914A.hs:1:38: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
diff --git a/testsuite/tests/ghci/scripts/T6018ghcirnfail.stderr b/testsuite/tests/ghci/scripts/T6018ghcirnfail.stderr
index 96b4dcd95d..d1d9d5ce38 100644
--- a/testsuite/tests/ghci/scripts/T6018ghcirnfail.stderr
+++ b/testsuite/tests/ghci/scripts/T6018ghcirnfail.stderr
@@ -1,46 +1,46 @@
 
-<interactive>:10:23: error:
+<interactive>:10:23: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-<interactive>:11:24: error:
+<interactive>:11:24: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-<interactive>:12:37: error:
+<interactive>:12:37: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-<interactive>:15:19: error:
+<interactive>:15:19: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:16:20: error:
+<interactive>:16:20: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:19:20: error:
+<interactive>:19:20: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:19:24: error:
+<interactive>:19:24: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
-<interactive>:20:21: error:
+<interactive>:20:21: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:20:25: error:
+<interactive>:20:25: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
-<interactive>:21:35: error:
+<interactive>:21:35: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:21:39: error:
+<interactive>:21:39: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
 <interactive>:24:1: error: [GHC-76037]
@@ -61,9 +61,9 @@
 <interactive>:36:23: error: [GHC-76037]
     Not in scope: type variable ‘c’
 
-<interactive>:39:33: error:
+<interactive>:39:33: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-<interactive>:42:37: error:
+<interactive>:42:37: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: b
diff --git a/testsuite/tests/ghci/scripts/T6106.stderr b/testsuite/tests/ghci/scripts/T6106.stderr
index 7023e2f709..e7e7047e05 100644
--- a/testsuite/tests/ghci/scripts/T6106.stderr
+++ b/testsuite/tests/ghci/scripts/T6106.stderr
@@ -1,4 +1,4 @@
 
-T6106.hs:1:1:
+T6106.hs:1:1: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
diff --git a/testsuite/tests/indexed-types/should_fail/T5515.stderr b/testsuite/tests/indexed-types/should_fail/T5515.stderr
index 688eef697e..29690e469b 100644
--- a/testsuite/tests/indexed-types/should_fail/T5515.stderr
+++ b/testsuite/tests/indexed-types/should_fail/T5515.stderr
@@ -1,8 +1,8 @@
 
-T5515.hs:9:3: error:
+T5515.hs:9:3: error: [GHC-53634]
     The RHS of an associated type declaration mentions out-of-scope variable ‘a’
       All such variables must be bound on the LHS
 
-T5515.hs:15:3: error:
+T5515.hs:15:3: error: [GHC-53634]
     The RHS of an associated type declaration mentions out-of-scope variable ‘a’
       All such variables must be bound on the LHS
diff --git a/testsuite/tests/parser/should_fail/T3811c.stderr b/testsuite/tests/parser/should_fail/T3811c.stderr
index 6d662a9b16..5d9b794f98 100644
--- a/testsuite/tests/parser/should_fail/T3811c.stderr
+++ b/testsuite/tests/parser/should_fail/T3811c.stderr
@@ -1,7 +1,7 @@
 
-T3811c.hs:6:10: error:
-    Illegal head of an instance declaration: ‘!Show D’
-      Instance heads must be of the form
-        C ty_1 ... ty_n
-      where ‘C’ is a class
-    In an instance declaration
+T3811c.hs:6:10: error: [GHC-12222]
+    • Illegal head of an instance declaration: ‘!Show D’
+        Instance heads must be of the form
+          C ty_1 ... ty_n
+        where ‘C’ is a class
+    • In an instance declaration
diff --git a/testsuite/tests/polykinds/T9574.stderr b/testsuite/tests/polykinds/T9574.stderr
index 26f2925ed9..c21c599d2f 100644
--- a/testsuite/tests/polykinds/T9574.stderr
+++ b/testsuite/tests/polykinds/T9574.stderr
@@ -1,4 +1,4 @@
 
-T9574.hs:13:5: error:
+T9574.hs:13:5: error: [GHC-53634]
     The RHS of an associated type declaration mentions out-of-scope variable ‘o’
       All such variables must be bound on the LHS
diff --git a/testsuite/tests/rename/should_compile/T15798a.stderr b/testsuite/tests/rename/should_compile/T15798a.stderr
index 6832205228..90615e8302 100644
--- a/testsuite/tests/rename/should_compile/T15798a.stderr
+++ b/testsuite/tests/rename/should_compile/T15798a.stderr
@@ -1,3 +1,3 @@
 
-T15798a.hs:11:3: warning: [-Wmissing-deriving-strategies]
+T15798a.hs:11:3: warning: [GHC-55631] [-Wmissing-deriving-strategies]
     No deriving strategy specified. Did you want stock, newtype, or anyclass?
diff --git a/testsuite/tests/rename/should_compile/T15798b.stderr b/testsuite/tests/rename/should_compile/T15798b.stderr
index de1b09ee48..a2a368b8b7 100644
--- a/testsuite/tests/rename/should_compile/T15798b.stderr
+++ b/testsuite/tests/rename/should_compile/T15798b.stderr
@@ -1,4 +1,4 @@
 
-T15798b.hs:9:19: warning: [-Wmissing-deriving-strategies]
+T15798b.hs:9:19: warning: [GHC-55631] [-Wmissing-deriving-strategies]
     No deriving strategy specified. Did you want stock, newtype, or anyclass?
-    Use DerivingStrategies to specify a strategy.
+    Suggested fix: Perhaps you intended to use DerivingStrategies
diff --git a/testsuite/tests/rename/should_compile/T15798c.stderr b/testsuite/tests/rename/should_compile/T15798c.stderr
index 868266aa3a..5b36d2b733 100644
--- a/testsuite/tests/rename/should_compile/T15798c.stderr
+++ b/testsuite/tests/rename/should_compile/T15798c.stderr
@@ -1,4 +1,4 @@
 
-T15798c.hs:6:3: warning: [-Wmissing-deriving-strategies]
+T15798c.hs:6:3: warning: [GHC-55631] [-Wmissing-deriving-strategies]
     No deriving strategy specified. Did you want stock, newtype, or anyclass?
-    Use DerivingStrategies to specify a strategy.
+    Suggested fix: Perhaps you intended to use DerivingStrategies
diff --git a/testsuite/tests/rename/should_fail/ExplicitForAllRules2.stderr b/testsuite/tests/rename/should_fail/ExplicitForAllRules2.stderr
index 8930d4d1fd..09b48e0272 100644
--- a/testsuite/tests/rename/should_fail/ExplicitForAllRules2.stderr
+++ b/testsuite/tests/rename/should_fail/ExplicitForAllRules2.stderr
@@ -2,7 +2,7 @@
 ExplicitForAllRules2.hs:6:41: error: [GHC-76037]
     Not in scope: type variable ‘b’
 
-ExplicitForAllRules2.hs:7:11: error:
+ExplicitForAllRules2.hs:7:11: error: [GHC-65669]
     Rule "new5":
     Forall'd variable ‘x’ does not appear on left hand side
 
diff --git a/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.hs b/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.hs
new file mode 100644
index 0000000000..e9310af418
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.hs
@@ -0,0 +1,6 @@
+{-# LANGUAGE DatatypeContexts #-}
+module RnStupidThetaInGadt where
+
+
+data (Eq a) => Foo a where
+  MkFoo :: Int
diff --git a/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.stderr b/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.stderr
new file mode 100644
index 0000000000..f1bf190b6e
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/RnStupidThetaInGadt.stderr
@@ -0,0 +1,7 @@
+
+RnStupidThetaInGadt.hs:1:14: warning: [-Wdeprecated-flags (in -Wdefault)]
+    -XDatatypeContexts is deprecated: It was widely considered a misfeature, and has been removed from the Haskell language.
+
+RnStupidThetaInGadt.hs:5:1: error: [GHC-18403]
+    No context is allowed on a GADT-style data declaration
+    (You can put a context on each constructor, though.)
diff --git a/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.hs b/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.hs
new file mode 100644
index 0000000000..93670a40cb
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.hs
@@ -0,0 +1,7 @@
+{-# LANGUAGE Haskell2010 #-}
+
+module RnUnexpectedStandaloneDeriving where
+
+data Foo = Foo
+
+deriving instance Eq Foo
diff --git a/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.stderr b/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.stderr
new file mode 100644
index 0000000000..33cbd49a29
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/RnUnexpectedStandaloneDeriving.stderr
@@ -0,0 +1,4 @@
+
+RnUnexpectedStandaloneDeriving.hs:7:1: error: [GHC-95159]
+    Illegal standalone deriving declaration
+    Suggested fix: Perhaps you intended to use StandaloneDeriving
diff --git a/testsuite/tests/rename/should_fail/T12146.stderr b/testsuite/tests/rename/should_fail/T12146.stderr
index 0dcd15470d..ad84fbbaa8 100644
--- a/testsuite/tests/rename/should_fail/T12146.stderr
+++ b/testsuite/tests/rename/should_fail/T12146.stderr
@@ -1,4 +1,4 @@
 
-T12146.hs:5:1:
+T12146.hs:5:1: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
diff --git a/testsuite/tests/rename/should_fail/T15659.stderr b/testsuite/tests/rename/should_fail/T15659.stderr
index e1cbf9f079..d090f3c6d3 100644
--- a/testsuite/tests/rename/should_fail/T15659.stderr
+++ b/testsuite/tests/rename/should_fail/T15659.stderr
@@ -1,5 +1,5 @@
 
-T15659.hs:3:11: error:
+T15659.hs:3:11: error: [GHC-63294]
     Rule "test":
       Not in scope: ‘f’
       in left-hand side: f x
diff --git a/testsuite/tests/rename/should_fail/T18021.stderr b/testsuite/tests/rename/should_fail/T18021.stderr
index 11fcea9964..c335a11a25 100644
--- a/testsuite/tests/rename/should_fail/T18021.stderr
+++ b/testsuite/tests/rename/should_fail/T18021.stderr
@@ -1,8 +1,8 @@
 
-T18021.hs:12:3: error:
+T18021.hs:12:3: error: [GHC-53634]
     The RHS of an associated type declaration mentions out-of-scope variable ‘a’
       All such variables must be bound on the LHS
 
-T18021.hs:17:3: error:
+T18021.hs:17:3: error: [GHC-53634]
     The RHS of an associated type declaration mentions out-of-scope variable ‘a’
       All such variables must be bound on the LHS
diff --git a/testsuite/tests/rename/should_fail/T18240a.stderr b/testsuite/tests/rename/should_fail/T18240a.stderr
index 50b419add4..165ede31c6 100644
--- a/testsuite/tests/rename/should_fail/T18240a.stderr
+++ b/testsuite/tests/rename/should_fail/T18240a.stderr
@@ -1,43 +1,43 @@
 
 T18240a.hs:11:11: error:
-    Instance head cannot contain nested ‘forall’s or contexts
-    In an instance declaration
+    • Instance head cannot contain nested ‘forall’s or contexts
+    • In an instance declaration
 
 T18240a.hs:12:15: error: [GHC-76037]
     Not in scope: type variable ‘a’
 
 T18240a.hs:14:11: error:
-    Instance head cannot contain nested ‘forall’s or contexts
-    In an instance declaration
+    • Instance head cannot contain nested ‘forall’s or contexts
+    • In an instance declaration
 
 T18240a.hs:17:11: error:
-    Instance head cannot contain nested ‘forall’s or contexts
-    In an instance declaration
+    • Instance head cannot contain nested ‘forall’s or contexts
+    • In an instance declaration
 
 T18240a.hs:18:22: error: [GHC-76037]
     Not in scope: type variable ‘a’
 
 T18240a.hs:20:21: error:
-    Instance head cannot contain nested ‘forall’s or contexts
-    In an instance declaration
+    • Instance head cannot contain nested ‘forall’s or contexts
+    • In an instance declaration
 
 T18240a.hs:21:24: error: [GHC-76037]
     Not in scope: type variable ‘b’
 
 T18240a.hs:23:19: error:
-    Instance head cannot contain nested ‘forall’s or contexts
-    In an instance declaration
-
-T18240a.hs:28:10: error:
-    Illegal head of an instance declaration: ‘42’
-      Instance heads must be of the form
-        C ty_1 ... ty_n
-      where ‘C’ is a class
-    In an instance declaration
-
-T18240a.hs:29:10: error:
-    Illegal head of an instance declaration: ‘Int -> Int’
-      Instance heads must be of the form
-        C ty_1 ... ty_n
-      where ‘C’ is a class
-    In an instance declaration
+    • Instance head cannot contain nested ‘forall’s or contexts
+    • In an instance declaration
+
+T18240a.hs:28:10: error: [GHC-12222]
+    • Illegal head of an instance declaration: ‘42’
+        Instance heads must be of the form
+          C ty_1 ... ty_n
+        where ‘C’ is a class
+    • In an instance declaration
+
+T18240a.hs:29:10: error: [GHC-12222]
+    • Illegal head of an instance declaration: ‘Int -> Int’
+        Instance heads must be of the form
+          C ty_1 ... ty_n
+        where ‘C’ is a class
+    • In an instance declaration
diff --git a/testsuite/tests/rename/should_fail/T4042.stderr b/testsuite/tests/rename/should_fail/T4042.stderr
index 65d737b6bd..a3b87404e1 100644
--- a/testsuite/tests/rename/should_fail/T4042.stderr
+++ b/testsuite/tests/rename/should_fail/T4042.stderr
@@ -1,4 +1,4 @@
 
-T4042.hs:6:1:
+T4042.hs:6:1: error: [GHC-25277]
     Parse error: module header, import declaration
     or top-level declaration expected.
diff --git a/testsuite/tests/rename/should_fail/T6018rnfail.stderr b/testsuite/tests/rename/should_fail/T6018rnfail.stderr
index 8833ad8fbd..55abeccbcf 100644
--- a/testsuite/tests/rename/should_fail/T6018rnfail.stderr
+++ b/testsuite/tests/rename/should_fail/T6018rnfail.stderr
@@ -1,46 +1,46 @@
 
-T6018rnfail.hs:8:23: error:
+T6018rnfail.hs:8:23: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-T6018rnfail.hs:9:24: error:
+T6018rnfail.hs:9:24: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-T6018rnfail.hs:12:19: error:
+T6018rnfail.hs:12:19: error: [GHC-88333]
     Incorrect type variable on the LHS of injectivity condition
          Expected : r
          Actual   : a
 
-T6018rnfail.hs:15:19: error:
+T6018rnfail.hs:15:19: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:16:20: error:
+T6018rnfail.hs:16:20: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:20:20: error:
+T6018rnfail.hs:20:20: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:20:24: error:
+T6018rnfail.hs:20:24: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
-T6018rnfail.hs:21:21: error:
+T6018rnfail.hs:21:21: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:21:25: error:
+T6018rnfail.hs:21:25: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
-T6018rnfail.hs:24:16: error:
+T6018rnfail.hs:24:16: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:24:20: error:
+T6018rnfail.hs:24:20: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: a
 
 T6018rnfail.hs:27:1: error: [GHC-76037]
@@ -61,11 +61,11 @@ T6018rnfail.hs:35:1: error: [GHC-76037]
 T6018rnfail.hs:38:3: error: [GHC-76037]
     Not in scope: type variable ‘c’
 
-T6018rnfail.hs:42:15: error:
+T6018rnfail.hs:42:15: error: [GHC-99412]
     Type variable ‘a’, naming a type family result,
     shadows an already bound type variable
 
-T6018rnfail.hs:46:19: error:
+T6018rnfail.hs:46:19: error: [GHC-48254]
     Unknown type variable on the RHS of injectivity condition: b
 
 T6018rnfail.hs:49:21: error: [GHC-76037]
diff --git a/testsuite/tests/rename/should_fail/all.T b/testsuite/tests/rename/should_fail/all.T
index 6234f4a85d..2255117886 100644
--- a/testsuite/tests/rename/should_fail/all.T
+++ b/testsuite/tests/rename/should_fail/all.T
@@ -192,3 +192,5 @@ test('RnMultipleFixityFail', normal, compile_fail, [''])
 test('RnEmptyCaseFail', normal, compile_fail, [''])
 test('RnDefaultSigFail', normal, compile_fail, [''])
 test('RnMultipleMinimalPragmaFail', normal, compile_fail, [''])
+test('RnUnexpectedStandaloneDeriving', normal, compile_fail, [''])
+test('RnStupidThetaInGadt', normal, compile_fail, [''])
diff --git a/testsuite/tests/roles/should_fail/Roles8.stderr b/testsuite/tests/roles/should_fail/Roles8.stderr
index 5f21527942..e06e03bfb5 100644
--- a/testsuite/tests/roles/should_fail/Roles8.stderr
+++ b/testsuite/tests/roles/should_fail/Roles8.stderr
@@ -1,10 +1,10 @@
 
-Roles8.hs:7:1:
+Roles8.hs:8:1: error: [GHC-97170]
     Duplicate role annotations for ‘T1’:
       type role T1 nominal -- written at Roles8.hs:7:1-20
       type role T1 nominal -- written at Roles8.hs:8:1-20
 
-Roles8.hs:12:1:
+Roles8.hs:13:1: error: [GHC-97170]
     Duplicate role annotations for ‘T2’:
       type role T2 representational -- written at Roles8.hs:12:1-29
       type role T2 phantom -- written at Roles8.hs:13:1-20
diff --git a/testsuite/tests/saks/should_fail/saks_fail001.stderr b/testsuite/tests/saks/should_fail/saks_fail001.stderr
index ed20d70860..a85605cafc 100644
--- a/testsuite/tests/saks/should_fail/saks_fail001.stderr
+++ b/testsuite/tests/saks/should_fail/saks_fail001.stderr
@@ -1,4 +1,4 @@
 
-saks_fail001.hs:8:1: error:
+saks_fail001.hs:8:1: error: [GHC-45906]
     Illegal standalone kind signature
-      Did you mean to enable StandaloneKindSignatures?
+    Suggested fix: Perhaps you intended to use StandaloneKindSignatures
diff --git a/testsuite/tests/saks/should_fail/saks_fail002.stderr b/testsuite/tests/saks/should_fail/saks_fail002.stderr
index bac0492f3a..c9069d2265 100644
--- a/testsuite/tests/saks/should_fail/saks_fail002.stderr
+++ b/testsuite/tests/saks/should_fail/saks_fail002.stderr
@@ -1,5 +1,5 @@
 
-saks_fail002.hs:9:1: error:
+saks_fail002.hs:11:1: error: [GHC-43371]
     Duplicate standalone kind signatures for ‘D’:
       type D :: Type -- written at saks_fail002.hs:9:1-14
       type D :: Type -- written at saks_fail002.hs:10:1-14