Add structured error messages for GHC.Tc.Utils.Backpack

Tracking ticket: #20119

MR: !10127

This converts uses of `mkTcRnUnknownMessage` to newly added constructors
of `TcRnMessage`.
One occurrence, when handing a nested error from the interface loading
machinery, was omitted. It will be handled by a subsequent changeset
that addresses interface errors.

15 files changed, 121 insertions, 49 deletions

diff --git a/compiler/GHC/Tc/Errors/Ppr.hs b/compiler/GHC/Tc/Errors/Ppr.hs
index a800b451c9..edb30d6e98 100644
--- a/compiler/GHC/Tc/Errors/Ppr.hs
+++ b/compiler/GHC/Tc/Errors/Ppr.hs
@@ -73,6 +73,7 @@ import GHC.Types.Unique.Set ( nonDetEltsUniqSet )
 import GHC.Types.Var
 import GHC.Types.Var.Set
 import GHC.Types.Var.Env
+import GHC.Types.Fixity (defaultFixity)
 
 import GHC.Unit.State (pprWithUnitState, UnitState)
 import GHC.Unit.Module
@@ -994,6 +995,32 @@ instance Diagnostic TcRnMessage where
     TcRnIllegalHsigDefaultMethods name meths
       -> mkSimpleDecorated $
         text "Illegal default method" <> plural (NE.toList meths) <+> text "in class definition of" <+> ppr name <+> text "in hsig file"
+    TcRnHsigFixityMismatch real_thing real_fixity sig_fixity
+      ->
+      let ppr_fix f = ppr f <+> if f == defaultFixity then parens (text "default") else empty
+      in mkSimpleDecorated $
+        vcat [ppr real_thing <+> text "has conflicting fixities in the module",
+              text "and its hsig file",
+              text "Main module:" <+> ppr_fix real_fixity,
+              text "Hsig file:" <+> ppr_fix sig_fixity]
+    TcRnHsigShapeMismatch (HsigShapeSortMismatch info1 info2)
+      -> mkSimpleDecorated $
+            text "While merging export lists, could not combine"
+            <+> ppr info1 <+> text "with" <+> ppr info2
+            <+> parens (text "one is a type, the other is a plain identifier")
+    TcRnHsigShapeMismatch (HsigShapeNotUnifiable name1 name2 notHere)
+      ->
+      let extra = if notHere
+                  then text "Neither name variable originates from the current signature."
+                  else empty
+      in mkSimpleDecorated $
+        text "While merging export lists, could not unify"
+        <+> ppr name1 <+> text "with" <+> ppr name2 $$ extra
+    TcRnHsigMissingModuleExport occ unit_state impl_mod
+      -> mkSimpleDecorated $
+            quotes (ppr occ)
+        <+> text "is exported by the hsig file, but not exported by the implementing module"
+        <+> quotes (pprWithUnitState unit_state $ ppr impl_mod)
     TcRnBadGenericMethod clas op
       -> mkSimpleDecorated $
         hsep [text "Class", quotes (ppr clas),
@@ -1726,6 +1753,12 @@ instance Diagnostic TcRnMessage where
       -> WarningWithFlag Opt_WarnWarningsDeprecations
     TcRnIllegalHsigDefaultMethods{}
       -> ErrorWithoutFlag
+    TcRnHsigFixityMismatch{}
+      -> ErrorWithoutFlag
+    TcRnHsigShapeMismatch{}
+      -> ErrorWithoutFlag
+    TcRnHsigMissingModuleExport{}
+      -> ErrorWithoutFlag
     TcRnBadGenericMethod{}
       -> ErrorWithoutFlag
     TcRnWarningMinimalDefIncomplete{}
@@ -2196,6 +2229,12 @@ instance Diagnostic TcRnMessage where
       -> noHints
     TcRnIllegalHsigDefaultMethods{}
       -> noHints
+    TcRnHsigFixityMismatch{}
+      -> noHints
+    TcRnHsigShapeMismatch{}
+      -> noHints
+    TcRnHsigMissingModuleExport{}
+      -> noHints
     TcRnBadGenericMethod{}
       -> noHints
     TcRnWarningMinimalDefIncomplete{}
diff --git a/compiler/GHC/Tc/Errors/Types.hs b/compiler/GHC/Tc/Errors/Types.hs
index 82d749e4ea..85e7a18377 100644
--- a/compiler/GHC/Tc/Errors/Types.hs
+++ b/compiler/GHC/Tc/Errors/Types.hs
@@ -91,6 +91,7 @@ module GHC.Tc.Errors.Types (
   , DeclSort(..)
   , NonStandardGuards(..)
   , RuleLhsErrReason(..)
+  , HsigShapeMismatchReason(..)
   ) where
 
 import GHC.Prelude
@@ -105,6 +106,7 @@ import GHC.Tc.Types.Origin ( CtOrigin (ProvCtxtOrigin), SkolemInfoAnon (SigSkol)
                            , FixedRuntimeRepOrigin(..) )
 import GHC.Tc.Types.Rank (Rank)
 import GHC.Tc.Utils.TcType (IllegalForeignTypeReason, TcType)
+import GHC.Types.Avail (AvailInfo)
 import GHC.Types.Error
 import GHC.Types.Hint (UntickedPromotedThing(..))
 import GHC.Types.ForeignCall (CLabelString)
@@ -2239,10 +2241,39 @@ data TcRnMessage where
     Test case:
       bkpfail40
   -}
-
   TcRnIllegalHsigDefaultMethods :: !Name -- ^ 'Name' of the class
                                 -> NE.NonEmpty (LHsBind GhcRn) -- ^ default methods
                                 -> TcRnMessage
+
+  {-| TcRnHsigFixityMismatch is an error indicating that the fixity decl in a
+    Backpack signature file differs from the one in the source file for the same
+    operator.
+
+    Test cases:
+      bkpfail37, bkpfail38
+  -}
+  TcRnHsigFixityMismatch :: !TyThing -- ^ The operator whose fixity is defined
+                         -> !Fixity -- ^ the fixity used in the source file
+                         -> !Fixity -- ^ the fixity used in the signature
+                         -> TcRnMessage
+
+  {-| TcRnHsigShapeMismatch is a group of errors related to mismatches between
+    backpack signatures.
+  -}
+  TcRnHsigShapeMismatch :: !HsigShapeMismatchReason
+                         -> TcRnMessage
+
+  {-| TcRnHsigMissingModuleExport is an error indicating that a module doesn't
+    export a name exported by its signature.
+
+    Test cases:
+      bkpfail01, bkpfail05, bkpfail09, bkpfail16, bkpfail35, bkpcabal06
+  -}
+  TcRnHsigMissingModuleExport :: !OccName -- ^ The missing name
+                              -> !UnitState -- ^ The module's unit state
+                              -> !Module -- ^ The implementation module
+                              -> TcRnMessage
+
   {-| TcRnBadGenericMethod
      This test ensures that if you provide a "more specific" type signatures
      for the default method, you must also provide a binding.
@@ -4419,3 +4450,24 @@ data NonStandardGuards where
 data RuleLhsErrReason
   = UnboundVariable RdrName NotInScopeError
   | IllegalExpression
+
+data HsigShapeMismatchReason =
+  {-| HsigShapeSortMismatch is an error indicating that an item in the
+    export list of a signature doesn't match the item of the same name in
+    another signature when merging the two – one is a type while the other is a
+    plain identifier.
+
+    Test cases:
+      none
+  -}
+  HsigShapeSortMismatch !AvailInfo !AvailInfo
+  |
+  {-| HsigShapeNotUnifiable is an error indicating that a name in the
+    export list of a signature cannot be unified with a name of the same name in
+    another signature when merging the two.
+
+    Test cases:
+      bkpfail20, bkpfail21
+  -}
+  HsigShapeNotUnifiable !Name !Name !Bool
+  deriving (Generic)
diff --git a/compiler/GHC/Tc/Utils/Backpack.hs b/compiler/GHC/Tc/Utils/Backpack.hs
index f11b900d6e..bc70d18684 100644
--- a/compiler/GHC/Tc/Utils/Backpack.hs
+++ b/compiler/GHC/Tc/Utils/Backpack.hs
@@ -88,21 +88,6 @@ import Data.List (find)
 
 import {-# SOURCE #-} GHC.Tc.Module
 
-
-fixityMisMatch :: TyThing -> Fixity -> Fixity -> TcRnMessage
-fixityMisMatch real_thing real_fixity sig_fixity =
-  mkTcRnUnknownMessage $ mkPlainError noHints $
-    vcat [ppr real_thing <+> text "has conflicting fixities in the module",
-          text "and its hsig file",
-          text "Main module:" <+> ppr_fix real_fixity,
-          text "Hsig file:" <+> ppr_fix sig_fixity]
-  where
-    ppr_fix f =
-        ppr f <+>
-        (if f == defaultFixity
-            then parens (text "default")
-            else empty)
-
 checkHsigDeclM :: ModIface -> TyThing -> TyThing -> TcRn ()
 checkHsigDeclM sig_iface sig_thing real_thing = do
     let name = getName real_thing
@@ -115,7 +100,7 @@ checkHsigDeclM sig_iface sig_thing real_thing = do
                         Just f -> f
     when (real_fixity /= sig_fixity) $
       addErrAt (nameSrcSpan name)
-        (fixityMisMatch real_thing real_fixity sig_fixity)
+        (TcRnHsigFixityMismatch real_thing real_fixity sig_fixity)
 
 -- | Given a 'ModDetails' of an instantiated signature (note that the
 -- 'ModDetails' must be knot-tied consistently with the actual implementation)
@@ -677,7 +662,7 @@ mergeSignatures
             -- 3(d). Extend the name substitution (performing shaping)
             mb_r <- extend_ns nsubst as2
             case mb_r of
-                Left err -> failWithTc (mkTcRnUnknownMessage $ mkPlainError noHints err)
+                Left err -> failWithTc (TcRnHsigShapeMismatch err)
                 Right nsubst' -> return (nsubst',oks',(imod, thinned_iface):ifaces)
         nsubst0 = mkNameShape (moduleName inner_mod) (mi_exports lcl_iface0)
         ok_to_use0 = mkOccSet (exportOccs (mi_exports lcl_iface0))
@@ -1004,10 +989,7 @@ checkImplements impl_mod req_mod@(Module uid mod_name) = do
     -- we need.  (Notice we IGNORE the Modules in the AvailInfos.)
     forM_ (exportOccs (mi_exports isig_iface)) $ \occ ->
         case lookupGlobalRdrEnv impl_gr occ of
-            [] -> addErr $ mkTcRnUnknownMessage $ mkPlainError noHints $
-                        quotes (ppr occ)
-                    <+> text "is exported by the hsig file, but not exported by the implementing module"
-                    <+> quotes (pprWithUnitState unit_state $ ppr impl_mod)
+            [] -> addErr $ TcRnHsigMissingModuleExport occ unit_state impl_mod
             _ -> return ()
     failIfErrsM
 
diff --git a/compiler/GHC/Types/Error/Codes.hs b/compiler/GHC/Types/Error/Codes.hs
index dca0923ce7..bc991393c4 100644
--- a/compiler/GHC/Types/Error/Codes.hs
+++ b/compiler/GHC/Types/Error/Codes.hs
@@ -471,6 +471,11 @@ type family GhcDiagnosticCode c = n | n -> c where
   GhcDiagnosticCode "TcRnIllegalTypeOperatorDecl"                   = 50649
 
   GhcDiagnosticCode "TcRnIllegalHsigDefaultMethods"                 = 93006
+  GhcDiagnosticCode "TcRnHsigFixityMismatch"                        = 93007
+  GhcDiagnosticCode "HsigShapeSortMismatch"                         = 93008
+  GhcDiagnosticCode "HsigShapeNotUnifiable"                         = 93009
+  GhcDiagnosticCode "TcRnHsigNoIface"                               = 93010
+  GhcDiagnosticCode "TcRnHsigMissingModuleExport"                   = 93011
   GhcDiagnosticCode "TcRnBadGenericMethod"                          = 59794
   GhcDiagnosticCode "TcRnWarningMinimalDefIncomplete"               = 13511
   GhcDiagnosticCode "TcRnDefaultMethodForPragmaLacksBinding"        = 28587
@@ -691,6 +696,7 @@ type family ConRecursInto con where
   ConRecursInto "TcRnPragmaWarning"        = 'Just (WarningTxt GhcRn)
   ConRecursInto "TcRnNotInScope"           = 'Just NotInScopeError
   ConRecursInto "TcRnIllegalNewtype"       = 'Just IllegalNewtypeReason
+  ConRecursInto "TcRnHsigShapeMismatch"    = 'Just HsigShapeMismatchReason
 
     --
     -- TH errors
diff --git a/compiler/GHC/Types/Name/Shape.hs b/compiler/GHC/Types/Name/Shape.hs
index 5e134001c1..19e97ef2c6 100644
--- a/compiler/GHC/Types/Name/Shape.hs
+++ b/compiler/GHC/Types/Name/Shape.hs
@@ -25,8 +25,8 @@ import GHC.Types.Name.Env
 
 import GHC.Tc.Utils.Monad
 import GHC.Iface.Env
+import GHC.Tc.Errors.Types
 
-import GHC.Utils.Outputable
 import GHC.Utils.Panic.Plain
 
 import Control.Monad
@@ -106,7 +106,7 @@ mkNameShape mod_name as =
 -- restricted notion of shaping than in Backpack'14: we do shaping
 -- *as* we do type-checking.  Thus, once we shape a signature, its
 -- exports are *final* and we're not allowed to refine them further,
-extendNameShape :: HscEnv -> NameShape -> [AvailInfo] -> IO (Either SDoc NameShape)
+extendNameShape :: HscEnv -> NameShape -> [AvailInfo] -> IO (Either HsigShapeMismatchReason NameShape)
 extendNameShape hsc_env ns as =
     case uAvailInfos (ns_mod_name ns) (ns_exports ns) as of
         Left err -> return (Left err)
@@ -224,7 +224,7 @@ mergeAvails as1 as2 =
 
 -- | Unify two lists of 'AvailInfo's, given an existing substitution @subst@,
 -- with only name holes from @flexi@ unifiable (all other name holes rigid.)
-uAvailInfos :: ModuleName -> [AvailInfo] -> [AvailInfo] -> Either SDoc ShNameSubst
+uAvailInfos :: ModuleName -> [AvailInfo] -> [AvailInfo] -> Either HsigShapeMismatchReason ShNameSubst
 uAvailInfos flexi as1 as2 = -- pprTrace "uAvailInfos" (ppr as1 $$ ppr as2) $
     let mkOE as = listToUFM $ do a <- as
                                  n <- availNames a
@@ -236,34 +236,27 @@ uAvailInfos flexi as1 as2 = -- pprTrace "uAvailInfos" (ppr as1 $$ ppr as2) $
 -- | Unify two 'AvailInfo's, given an existing substitution @subst@,
 -- with only name holes from @flexi@ unifiable (all other name holes rigid.)
 uAvailInfo :: ModuleName -> ShNameSubst -> AvailInfo -> AvailInfo
-           -> Either SDoc ShNameSubst
+           -> Either HsigShapeMismatchReason ShNameSubst
 uAvailInfo flexi subst (Avail (NormalGreName n1)) (Avail (NormalGreName n2)) = uName flexi subst n1 n2
 uAvailInfo flexi subst (AvailTC n1 _) (AvailTC n2 _) = uName flexi subst n1 n2
-uAvailInfo _ _ a1 a2 = Left $ text "While merging export lists, could not combine"
-                           <+> ppr a1 <+> text "with" <+> ppr a2
-                           <+> parens (text "one is a type, the other is a plain identifier")
+uAvailInfo _ _ a1 a2 = Left $ HsigShapeSortMismatch a1 a2
 
 -- | Unify two 'Name's, given an existing substitution @subst@,
 -- with only name holes from @flexi@ unifiable (all other name holes rigid.)
-uName :: ModuleName -> ShNameSubst -> Name -> Name -> Either SDoc ShNameSubst
+uName :: ModuleName -> ShNameSubst -> Name -> Name -> Either HsigShapeMismatchReason ShNameSubst
 uName flexi subst n1 n2
     | n1 == n2      = Right subst
     | isFlexi n1    = uHoleName flexi subst n1 n2
     | isFlexi n2    = uHoleName flexi subst n2 n1
-    | otherwise     = Left (text "While merging export lists, could not unify"
-                         <+> ppr n1 <+> text "with" <+> ppr n2 $$ extra)
+    | otherwise     = Left (HsigShapeNotUnifiable n1 n2 (isHoleName n1 || isHoleName n2))
   where
     isFlexi n = isHoleName n && moduleName (nameModule n) == flexi
-    extra | isHoleName n1 || isHoleName n2
-          = text "Neither name variable originates from the current signature."
-          | otherwise
-          = empty
 
 -- | Unify a name @h@ which 'isHoleName' with another name, given an existing
 -- substitution @subst@, with only name holes from @flexi@ unifiable (all
 -- other name holes rigid.)
 uHoleName :: ModuleName -> ShNameSubst -> Name {- hole name -} -> Name
-          -> Either SDoc ShNameSubst
+          -> Either HsigShapeMismatchReason ShNameSubst
 uHoleName flexi subst h n =
     assert (isHoleName h) $
     case lookupNameEnv subst h of
diff --git a/testsuite/tests/backpack/cabal/bkpcabal06/bkpcabal06.stderr b/testsuite/tests/backpack/cabal/bkpcabal06/bkpcabal06.stderr
index a266829205..24defef3c5 100644
--- a/testsuite/tests/backpack/cabal/bkpcabal06/bkpcabal06.stderr
+++ b/testsuite/tests/backpack/cabal/bkpcabal06/bkpcabal06.stderr
@@ -1,4 +1,4 @@
 
-sig/P.hsig:1:1: error:
+sig/P.hsig:1:1: error: [GHC-93011]
     • ‘p’ is exported by the hsig file, but not exported by the implementing module ‘bkpcabal06-0.1.0.0:impl:P’
     • while checking that bkpcabal06-0.1.0.0:impl:P implements signature P in bkpcabal06-0.1.0.0:sig[P=bkpcabal06-0.1.0.0:impl:P]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail01.stderr b/testsuite/tests/backpack/should_fail/bkpfail01.stderr
index e88d122fa4..7197fa3eb2 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail01.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail01.stderr
@@ -10,10 +10,10 @@
     Instantiating p[H=q:H]
     [1 of 2] Compiling H[sig]           ( p/H.hsig, nothing )
 
-bkpfail01.out/p/p-D5Mg3foBSCrDbQDKH4WGSG/../H.hi:1:1: error:
+bkpfail01.out/p/p-D5Mg3foBSCrDbQDKH4WGSG/../H.hi:1:1: error: [GHC-93011]
     • ‘H’ is exported by the hsig file, but not exported by the implementing module ‘q:H’
     • while checking that q:H implements signature H in p[H=q:H]
 
-bkpfail01.out/p/p-D5Mg3foBSCrDbQDKH4WGSG/../H.hi:1:1: error:
+bkpfail01.out/p/p-D5Mg3foBSCrDbQDKH4WGSG/../H.hi:1:1: error: [GHC-93011]
     • ‘H’ is exported by the hsig file, but not exported by the implementing module ‘q:H’
     • while checking that q:H implements signature H in p[H=q:H]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail05.stderr b/testsuite/tests/backpack/should_fail/bkpfail05.stderr
index da996cfb7e..c07426fc6b 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail05.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail05.stderr
@@ -18,6 +18,6 @@
       Instantiating h[H=h-impl:H]
       [1 of 1] Compiling H[sig]           ( h/H.hsig, bkpfail05.out/h/h-5FYQgnNkfSvBT5yogOxPpf/H.o )
 
-bkpfail05.out/h/h-5FYQgnNkfSvBT5yogOxPpf/../H.hi:1:1: error:
+bkpfail05.out/h/h-5FYQgnNkfSvBT5yogOxPpf/../H.hi:1:1: error: [GHC-93011]
     • ‘T1’ is exported by the hsig file, but not exported by the implementing module ‘h-impl:H’
     • while checking that h-impl:H implements signature H in h[H=h-impl:H]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail09.stderr b/testsuite/tests/backpack/should_fail/bkpfail09.stderr
index de1d100a34..858f292001 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail09.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail09.stderr
@@ -8,10 +8,10 @@
   [1 of 3] Compiling H2[sig]          ( r/H2.hsig, nothing )
   [2 of 3] Instantiating p
 
-Command line argument: -unit-id p[H=H]:0:0: error:
+Command line argument: -unit-id p[H=H]:0:0: error: [GHC-93011]
     • ‘H’ is exported by the hsig file, but not exported by the implementing module ‘q:H’
     • while checking that q:H implements signature H in p[H=q:H]
 
-Command line argument: -unit-id p[H=H]:0:0: error:
+Command line argument: -unit-id p[H=H]:0:0: error: [GHC-93011]
     • ‘H’ is exported by the hsig file, but not exported by the implementing module ‘q:H’
     • while checking that q:H implements signature H in p[H=q:H]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail16.stderr b/testsuite/tests/backpack/should_fail/bkpfail16.stderr
index b3bea76954..af4d241106 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail16.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail16.stderr
@@ -6,6 +6,6 @@
     Instantiating p[ShouldFail=base-4.13.0.0:Data.Bool]
     [1 of 1] Compiling ShouldFail[sig]  ( p/ShouldFail.hsig, bkpfail16.out/p/p-1OqLaT7dAn947wScQQKCw5/ShouldFail.o )
 
-bkpfail16.out/p/p-1OqLaT7dAn947wScQQKCw5/../ShouldFail.hi:1:1: error:
+bkpfail16.out/p/p-1OqLaT7dAn947wScQQKCw5/../ShouldFail.hi:1:1: error: [GHC-93011]
     • ‘Booly’ is exported by the hsig file, but not exported by the implementing module ‘Data.Bool’
     • while checking that Data.Bool implements signature ShouldFail in p[ShouldFail=Data.Bool]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail20.stderr b/testsuite/tests/backpack/should_fail/bkpfail20.stderr
index bd450f9f8c..799d58a44b 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail20.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail20.stderr
@@ -5,7 +5,7 @@
 [3 of 3] Processing r
   [1 of 3] Compiling B[sig]           ( r/B.hsig, nothing )
 
-bkpfail20.bkp:1:1: error:
+bkpfail20.bkp:1:1: error: [GHC-93009]
     • While merging export lists, could not unify Data.STRef.Lazy.newSTRef with GHC.STRef.newSTRef
     • while merging the signatures from:
         • p[A=<B>]:A
diff --git a/testsuite/tests/backpack/should_fail/bkpfail21.stderr b/testsuite/tests/backpack/should_fail/bkpfail21.stderr
index bc40bbc344..72444b2fd2 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail21.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail21.stderr
@@ -9,7 +9,7 @@
   [2 of 5] Compiling H1[sig]          ( r/H1.hsig, nothing )
   [3 of 5] Compiling H3[sig]          ( r/H3.hsig, nothing )
 
-bkpfail21.bkp:1:1: error:
+bkpfail21.bkp:1:1: error: [GHC-93009]
     • While merging export lists, could not unify {H1.T} with {H2.T}
       Neither name variable originates from the current signature.
     • while merging the signatures from:
diff --git a/testsuite/tests/backpack/should_fail/bkpfail35.stderr b/testsuite/tests/backpack/should_fail/bkpfail35.stderr
index 893a8dd2ae..f72bd23184 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail35.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail35.stderr
@@ -13,6 +13,6 @@
     Instantiating q[A=aimpl:A]
     [1 of 1] Compiling A[sig]           ( q/A.hsig, bkpfail35.out/q/q-E72T6bb4XRkIeTPWK2mCKa/A.o )
 
-bkpfail35.out/q/q-E72T6bb4XRkIeTPWK2mCKa/../A.hi:1:1: error:
+bkpfail35.out/q/q-E72T6bb4XRkIeTPWK2mCKa/../A.hi:1:1: error: [GHC-93011]
     • ‘y’ is exported by the hsig file, but not exported by the implementing module ‘aimpl:A’
     • while checking that aimpl:A implements signature A in q[A=aimpl:A]
diff --git a/testsuite/tests/backpack/should_fail/bkpfail37.stderr b/testsuite/tests/backpack/should_fail/bkpfail37.stderr
index a10c05fbeb..4158517b28 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail37.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail37.stderr
@@ -9,7 +9,7 @@
     Instantiating p[A=q:A]
     [1 of 1] Compiling A[sig]           ( p/A.hsig, bkpfail37.out/p/p-HVmFlcYSefiK5n1aDP1v7x/A.o )
 
-bkpfail37.bkp:9:9: error:
+bkpfail37.bkp:9:9: error: [GHC-93007]
     • Identifier ‘op’ has conflicting fixities in the module
       and its hsig file
       Main module: infixr 4
diff --git a/testsuite/tests/backpack/should_fail/bkpfail38.stderr b/testsuite/tests/backpack/should_fail/bkpfail38.stderr
index 264e150783..41c713925b 100644
--- a/testsuite/tests/backpack/should_fail/bkpfail38.stderr
+++ b/testsuite/tests/backpack/should_fail/bkpfail38.stderr
@@ -5,7 +5,7 @@
 [3 of 3] Processing r
   [1 of 3] Compiling A[sig]           ( r/A.hsig, nothing )
 
-bkpfail38.bkp:8:9: error:
+bkpfail38.bkp:8:9: error: [GHC-93007]
     • Identifier ‘op’ has conflicting fixities in the module
       and its hsig file
       Main module: infixr 4