Kill varSetElems in tidyFreeTyCoVars

I haven't observed this to have an effect on nondeterminism,
but tidyOccName appears to modify the TidyOccEnv in a
way dependent on the order of inputs.
It's easy enough to change it to be deterministic to be on the
safe side.

Test Plan: ./validate

Reviewers: simonmar, austin, bgamari, simonpj

Reviewed By: simonpj

Subscribers: thomie

Differential Revision: https://phabricator.haskell.org/D2238

GHC Trac Issues: #4012

12 files changed, 188 insertions, 188 deletions

diff --git a/compiler/typecheck/TcErrors.hs b/compiler/typecheck/TcErrors.hs
index cdd77f1112..e7fb82757b 100644
--- a/compiler/typecheck/TcErrors.hs
+++ b/compiler/typecheck/TcErrors.hs
@@ -175,10 +175,10 @@ report_unsolved mb_binds_var err_as_warn type_errors expr_holes type_holes wante
             -- If we are deferring we are going to need /all/ evidence around,
             -- including the evidence produced by unflattening (zonkWC)
        ; let tidy_env = tidyFreeTyCoVars env0 free_tvs
-             free_tvs = tyCoVarsOfWC wanted
+             free_tvs = tyCoVarsOfWCList wanted
 
        ; traceTc "reportUnsolved (after zonking and tidying):" $
-         vcat [ pprVarSet free_tvs pprTvBndrs
+         vcat [ pprTvBndrs free_tvs
               , ppr wanted ]
 
        ; warn_redundant <- woptM Opt_WarnRedundantConstraints
@@ -2631,7 +2631,7 @@ warnDefaulting wanteds default_ty
   = do { warn_default <- woptM Opt_WarnTypeDefaults
        ; env0 <- tcInitTidyEnv
        ; let tidy_env = tidyFreeTyCoVars env0 $
-                        foldr (unionVarSet . tyCoVarsOfCt) emptyVarSet wanteds
+                        tyCoVarsOfCtsList (listToBag wanteds)
              tidy_wanteds = map (tidyCt tidy_env) wanteds
              (loc, ppr_wanteds) = pprWithArising tidy_wanteds
              warn_msg =
@@ -2663,7 +2663,7 @@ solverDepthErrorTcS loc ty
   = setCtLocM loc $
     do { ty <- zonkTcType ty
        ; env0 <- tcInitTidyEnv
-       ; let tidy_env     = tidyFreeTyCoVars env0 (tyCoVarsOfType ty)
+       ; let tidy_env     = tidyFreeTyCoVars env0 (tyCoVarsOfTypeList ty)
              tidy_ty      = tidyType tidy_env ty
              msg
                = vcat [ text "Reduction stack overflow; size =" <+> ppr depth
diff --git a/compiler/typecheck/TcRnMonad.hs b/compiler/typecheck/TcRnMonad.hs
index 2691c82638..c4e66a0216 100644
--- a/compiler/typecheck/TcRnMonad.hs
+++ b/compiler/typecheck/TcRnMonad.hs
@@ -1148,7 +1148,7 @@ tcInitTidyEnv
 
 -- | Get a 'TidyEnv' that includes mappings for all vars free in the given
 -- type. Useful when tidying open types.
-tcInitOpenTidyEnv :: TyCoVarSet -> TcM TidyEnv
+tcInitOpenTidyEnv :: [TyCoVar] -> TcM TidyEnv
 tcInitOpenTidyEnv tvs
   = do { env1 <- tcInitTidyEnv
        ; let env2 = tidyFreeTyCoVars env1 tvs
diff --git a/compiler/typecheck/TcValidity.hs b/compiler/typecheck/TcValidity.hs
index d9f43d39c3..83f64f3783 100644
--- a/compiler/typecheck/TcValidity.hs
+++ b/compiler/typecheck/TcValidity.hs
@@ -349,7 +349,7 @@ checkValidType ctxt ty
                  _              -> panic "checkValidType"
                                           -- Can't happen; not used for *user* sigs
 
-       ; env <- tcInitOpenTidyEnv (tyCoVarsOfType ty)
+       ; env <- tcInitOpenTidyEnv (tyCoVarsOfTypeList ty)
 
         -- Check the internal validity of the type itself
        ; check_type env ctxt rank ty
@@ -371,7 +371,7 @@ checkValidType ctxt ty
 checkValidMonoType :: Type -> TcM ()
 -- Assumes arguemt is fully zonked
 checkValidMonoType ty
-  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfType ty)
+  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfTypeList ty)
        ; check_type env SigmaCtxt MustBeMonoType ty }
 
 check_kind :: TidyEnv -> UserTypeCtxt -> TcType -> TcM ()
@@ -471,7 +471,7 @@ kind system should check for uses of unlifted types.  So I've
 removed the check.  See Trac #11120 comment:19.
 
 check_lifted ty
-  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfType ty)
+  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfTypeList ty)
        ; checkTcM (not (isUnliftedType ty)) (unliftedArgErr env ty) }
 
 unliftedArgErr :: TidyEnv -> Type -> (TidyEnv, SDoc)
@@ -707,7 +707,7 @@ applying the instance decl would show up two uses of ?x.  Trac #8912.
 checkValidTheta :: UserTypeCtxt -> ThetaType -> TcM ()
 -- Assumes arguemt is fully zonked
 checkValidTheta ctxt theta
-  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfTypes theta)
+  = do { env <- tcInitOpenTidyEnv (tyCoVarsOfTypesList theta)
        ; addErrCtxtM (checkThetaCtxt ctxt theta) $
          check_valid_theta env ctxt theta }
 
diff --git a/compiler/types/TyCoRep.hs b/compiler/types/TyCoRep.hs
index 04badbd533..9f792437d5 100644
--- a/compiler/types/TyCoRep.hs
+++ b/compiler/types/TyCoRep.hs
@@ -3155,11 +3155,11 @@ tidyTyBinders :: TidyEnv -> [TyBinder] -> (TidyEnv, [TyBinder])
 tidyTyBinders = mapAccumL tidyTyBinder
 
 ---------------
-tidyFreeTyCoVars :: TidyEnv -> TyCoVarSet -> TidyEnv
+tidyFreeTyCoVars :: TidyEnv -> [TyCoVar] -> TidyEnv
 -- ^ Add the free 'TyVar's to the env in tidy form,
 -- so that we can tidy the type they are free in
 tidyFreeTyCoVars (full_occ_env, var_env) tyvars
-  = fst (tidyOpenTyCoVars (full_occ_env, var_env) (varSetElems tyvars))
+  = fst (tidyOpenTyCoVars (full_occ_env, var_env) tyvars)
 
         ---------------
 tidyOpenTyCoVars :: TidyEnv -> [TyCoVar] -> (TidyEnv, [TyCoVar])
@@ -3174,8 +3174,8 @@ tidyOpenTyCoVar env@(_, subst) tyvar
   = case lookupVarEnv subst tyvar of
         Just tyvar' -> (env, tyvar')              -- Already substituted
         Nothing     ->
-          let env' = tidyFreeTyCoVars env (tyCoVarsOfType (tyVarKind tyvar)) in
-          tidyTyCoVarBndr env' tyvar  -- Treat it as a binder
+          let env' = tidyFreeTyCoVars env (tyCoVarsOfTypeList (tyVarKind tyvar))
+          in tidyTyCoVarBndr env' tyvar  -- Treat it as a binder
 
 ---------------
 tidyTyVarOcc :: TidyEnv -> TyVar -> TyVar
diff --git a/testsuite/tests/indexed-types/should_fail/T2693.stderr b/testsuite/tests/indexed-types/should_fail/T2693.stderr
index a0ac4eaeb6..c0bd7329fd 100644
--- a/testsuite/tests/indexed-types/should_fail/T2693.stderr
+++ b/testsuite/tests/indexed-types/should_fail/T2693.stderr
@@ -24,8 +24,8 @@ T2693.hs:19:15: error:
     • Relevant bindings include n :: a5 (bound at T2693.hs:19:7)
 
 T2693.hs:19:23: error:
-    • Couldn't match expected type ‘(a3, a5)’ with actual type ‘TFn a4’
-      The type variables ‘a4’, ‘a3’, ‘a5’ are ambiguous
+    • Couldn't match expected type ‘(a4, a5)’ with actual type ‘TFn a3’
+      The type variables ‘a3’, ‘a4’, ‘a5’ are ambiguous
     • In the first argument of ‘snd’, namely ‘x’
       In the second argument of ‘(+)’, namely ‘snd x’
       In the expression: fst x + snd x
diff --git a/testsuite/tests/overloadedrecflds/should_fail/overloadedlabelsfail01.stderr b/testsuite/tests/overloadedrecflds/should_fail/overloadedlabelsfail01.stderr
index b9d3bba31b..f938d03169 100644
--- a/testsuite/tests/overloadedrecflds/should_fail/overloadedlabelsfail01.stderr
+++ b/testsuite/tests/overloadedrecflds/should_fail/overloadedlabelsfail01.stderr
@@ -1,31 +1,31 @@
 
 overloadedlabelsfail01.hs:6:5: error:
-    No instance for (IsLabel "x" t2)
-      arising from the overloaded label ‘#x’
-    In the expression: #x
-    In an equation for ‘a’: a = #x
+    • No instance for (IsLabel "x" t2)
+        arising from the overloaded label ‘#x’
+    • In the expression: #x
+      In an equation for ‘a’: a = #x
 
 overloadedlabelsfail01.hs:9:5: error:
-    No instance for (IsLabel "x" (t0 -> t1))
-      arising from the overloaded label ‘#x’
-      (maybe you haven't applied a function to enough arguments?)
-    In the expression: #x
-    In the expression: #x #y
-    In an equation for ‘b’: b = #x #y
+    • No instance for (IsLabel "x" (t1 -> t0))
+        arising from the overloaded label ‘#x’
+        (maybe you haven't applied a function to enough arguments?)
+    • In the expression: #x
+      In the expression: #x #y
+      In an equation for ‘b’: b = #x #y
 
 overloadedlabelsfail01.hs:9:8: error:
-    No instance for (IsLabel "y" t0)
-      arising from the overloaded label ‘#y’
-    In the first argument of ‘#x’, namely ‘#y’
-    In the expression: #x #y
-    In an equation for ‘b’: b = #x #y
+    • No instance for (IsLabel "y" t1)
+        arising from the overloaded label ‘#y’
+    • In the first argument of ‘#x’, namely ‘#y’
+      In the expression: #x #y
+      In an equation for ‘b’: b = #x #y
 
 overloadedlabelsfail01.hs:13:5: error:
-    Could not deduce (IsLabel "y" t)
-      arising from the overloaded label ‘#y’
-    from the context: IsLabel "x" t
-      bound by the type signature for:
-                 c :: IsLabel "x" t => t
-      at overloadedlabelsfail01.hs:12:1-23
-    In the expression: #y
-    In an equation for ‘c’: c = #y
+    • Could not deduce (IsLabel "y" t)
+        arising from the overloaded label ‘#y’
+      from the context: IsLabel "x" t
+        bound by the type signature for:
+                   c :: IsLabel "x" t => t
+        at overloadedlabelsfail01.hs:12:1-23
+    • In the expression: #y
+      In an equation for ‘c’: c = #y
diff --git a/testsuite/tests/parser/should_fail/T7848.stderr b/testsuite/tests/parser/should_fail/T7848.stderr
index f7617ee606..e1a64e4668 100644
--- a/testsuite/tests/parser/should_fail/T7848.stderr
+++ b/testsuite/tests/parser/should_fail/T7848.stderr
@@ -1,9 +1,9 @@
 
 T7848.hs:6:1: error:
     • Occurs check: cannot construct the infinite type:
-        t ~ t0 -> t1 -> A -> A -> A -> A -> t2 -> t
+        t ~ t2 -> t1 -> A -> A -> A -> A -> t0 -> t
     • When checking that:
-          t0 -> t1 -> A -> A -> A -> A -> forall t2. t2 -> t
+          t2 -> t1 -> A -> A -> A -> A -> forall t4. t4 -> t
         is more polymorphic than: t
     • Relevant bindings include x :: t (bound at T7848.hs:6:1)
 
diff --git a/testsuite/tests/rename/should_fail/T10618.stderr b/testsuite/tests/rename/should_fail/T10618.stderr
index 8b4dc2c28d..21c35471dd 100644
--- a/testsuite/tests/rename/should_fail/T10618.stderr
+++ b/testsuite/tests/rename/should_fail/T10618.stderr
@@ -1,6 +1,6 @@
 
 T10618.hs:3:22: error:
-    • Variable not in scope: (<>) :: Maybe (Maybe a0) -> Maybe a1 -> t
+    • Variable not in scope: (<>) :: Maybe (Maybe a1) -> Maybe a0 -> t
     • Perhaps you meant one of these:
         ‘<$>’ (imported from Prelude), ‘*>’ (imported from Prelude),
         ‘<$’ (imported from Prelude)
diff --git a/testsuite/tests/typecheck/should_fail/T11355.stderr b/testsuite/tests/typecheck/should_fail/T11355.stderr
index 68375400a8..6c649e4187 100644
--- a/testsuite/tests/typecheck/should_fail/T11355.stderr
+++ b/testsuite/tests/typecheck/should_fail/T11355.stderr
@@ -1,6 +1,6 @@
 
 T11355.hs:5:7: error:
-    • Illegal polymorphic type: forall (a :: TYPE t0). a
+    • Illegal polymorphic type: forall (a :: TYPE t1). a
       GHC doesn't yet support impredicative polymorphism
     • In the expression:
         const @_ @((forall a. a) -> forall a. a) () (id @(forall a. a))
diff --git a/testsuite/tests/typecheck/should_fail/T5684.stderr b/testsuite/tests/typecheck/should_fail/T5684.stderr
index b2d0b01c46..673b7de92c 100644
--- a/testsuite/tests/typecheck/should_fail/T5684.stderr
+++ b/testsuite/tests/typecheck/should_fail/T5684.stderr
@@ -1,144 +1,144 @@
 
-T5684.hs:20:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op False False, op 'c' undefined, op True undefined]
-    In an equation for ‘flop1’:
-        flop1 = [op False False, op 'c' undefined, op True undefined]
-
-T5684.hs:24:12:
-    No instance for (B Char b10) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op False False, op 'c' undefined, op True undefined]
-    In an equation for ‘flop1’:
-        flop1 = [op False False, op 'c' undefined, op True undefined]
-
-T5684.hs:25:12:
-    No instance for (A b11) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op False False, op 'c' undefined, op True undefined]
-    In an equation for ‘flop1’:
-        flop1 = [op False False, op 'c' undefined, op True undefined]
-
-T5684.hs:29:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op False False, op True undefined, op 'c' undefined]
-    In an equation for ‘flop2’:
-        flop2 = [op False False, op True undefined, op 'c' undefined]
-
-T5684.hs:30:12:
-    No instance for (A b8) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op False False, op True undefined, op 'c' undefined]
-    In an equation for ‘flop2’:
-        flop2 = [op False False, op True undefined, op 'c' undefined]
-
-T5684.hs:31:12:
-    No instance for (B Char b9) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op False False, op True undefined, op 'c' undefined]
-    In an equation for ‘flop2’:
-        flop2 = [op False False, op True undefined, op 'c' undefined]
-
-T5684.hs:35:12:
-    No instance for (B Char b6) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op 'c' undefined, op True undefined, op False False]
-    In an equation for ‘flop3’:
-        flop3 = [op 'c' undefined, op True undefined, op False False]
-
-T5684.hs:36:12:
-    No instance for (A b7) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op 'c' undefined, op True undefined, op False False]
-    In an equation for ‘flop3’:
-        flop3 = [op 'c' undefined, op True undefined, op False False]
-
-T5684.hs:37:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op 'c' undefined, op True undefined, op False False]
-    In an equation for ‘flop3’:
-        flop3 = [op 'c' undefined, op True undefined, op False False]
-
-T5684.hs:40:12:
-    No instance for (B Char b4) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op 'c' undefined, op False False, op True undefined]
-    In an equation for ‘flop4’:
-        flop4 = [op 'c' undefined, op False False, op True undefined]
-
-T5684.hs:41:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op 'c' undefined, op False False, op True undefined]
-    In an equation for ‘flop4’:
-        flop4 = [op 'c' undefined, op False False, op True undefined]
-
-T5684.hs:42:12:
-    No instance for (A b5) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op 'c' undefined, op False False, op True undefined]
-    In an equation for ‘flop4’:
-        flop4 = [op 'c' undefined, op False False, op True undefined]
-
-T5684.hs:46:12:
-    No instance for (A b2) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op True undefined, op 'c' undefined, op False False]
-    In an equation for ‘flop5’:
-        flop5 = [op True undefined, op 'c' undefined, op False False]
-
-T5684.hs:47:12:
-    No instance for (B Char b3) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op True undefined, op 'c' undefined, op False False]
-    In an equation for ‘flop5’:
-        flop5 = [op True undefined, op 'c' undefined, op False False]
-
-T5684.hs:48:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op True undefined, op 'c' undefined, op False False]
-    In an equation for ‘flop5’:
-        flop5 = [op True undefined, op 'c' undefined, op False False]
-
-T5684.hs:52:12:
-    No instance for (A b0) arising from a use of ‘op’
-    In the expression: op True undefined
-    In the expression:
-      [op True undefined, op False False, op 'c' undefined]
-    In an equation for ‘flop6’:
-        flop6 = [op True undefined, op False False, op 'c' undefined]
-
-T5684.hs:53:12:
-    No instance for (A Bool) arising from a use of ‘op’
-    In the expression: op False False
-    In the expression:
-      [op True undefined, op False False, op 'c' undefined]
-    In an equation for ‘flop6’:
-        flop6 = [op True undefined, op False False, op 'c' undefined]
-
-T5684.hs:54:12:
-    No instance for (B Char b1) arising from a use of ‘op’
-    In the expression: op 'c' undefined
-    In the expression:
-      [op True undefined, op False False, op 'c' undefined]
-    In an equation for ‘flop6’:
-        flop6 = [op True undefined, op False False, op 'c' undefined]
+T5684.hs:20:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op False False, op 'c' undefined, op True undefined]
+      In an equation for ‘flop1’:
+          flop1 = [op False False, op 'c' undefined, op True undefined]
+
+T5684.hs:24:12: error:
+    • No instance for (B Char b10) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op False False, op 'c' undefined, op True undefined]
+      In an equation for ‘flop1’:
+          flop1 = [op False False, op 'c' undefined, op True undefined]
+
+T5684.hs:25:12: error:
+    • No instance for (A b11) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op False False, op 'c' undefined, op True undefined]
+      In an equation for ‘flop1’:
+          flop1 = [op False False, op 'c' undefined, op True undefined]
+
+T5684.hs:29:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op False False, op True undefined, op 'c' undefined]
+      In an equation for ‘flop2’:
+          flop2 = [op False False, op True undefined, op 'c' undefined]
+
+T5684.hs:30:12: error:
+    • No instance for (A b8) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op False False, op True undefined, op 'c' undefined]
+      In an equation for ‘flop2’:
+          flop2 = [op False False, op True undefined, op 'c' undefined]
+
+T5684.hs:31:12: error:
+    • No instance for (B Char b9) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op False False, op True undefined, op 'c' undefined]
+      In an equation for ‘flop2’:
+          flop2 = [op False False, op True undefined, op 'c' undefined]
+
+T5684.hs:35:12: error:
+    • No instance for (B Char b6) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op 'c' undefined, op True undefined, op False False]
+      In an equation for ‘flop3’:
+          flop3 = [op 'c' undefined, op True undefined, op False False]
+
+T5684.hs:36:12: error:
+    • No instance for (A b7) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op 'c' undefined, op True undefined, op False False]
+      In an equation for ‘flop3’:
+          flop3 = [op 'c' undefined, op True undefined, op False False]
+
+T5684.hs:37:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op 'c' undefined, op True undefined, op False False]
+      In an equation for ‘flop3’:
+          flop3 = [op 'c' undefined, op True undefined, op False False]
+
+T5684.hs:40:12: error:
+    • No instance for (B Char b4) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op 'c' undefined, op False False, op True undefined]
+      In an equation for ‘flop4’:
+          flop4 = [op 'c' undefined, op False False, op True undefined]
+
+T5684.hs:41:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op 'c' undefined, op False False, op True undefined]
+      In an equation for ‘flop4’:
+          flop4 = [op 'c' undefined, op False False, op True undefined]
+
+T5684.hs:42:12: error:
+    • No instance for (A b5) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op 'c' undefined, op False False, op True undefined]
+      In an equation for ‘flop4’:
+          flop4 = [op 'c' undefined, op False False, op True undefined]
+
+T5684.hs:46:12: error:
+    • No instance for (A b3) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op True undefined, op 'c' undefined, op False False]
+      In an equation for ‘flop5’:
+          flop5 = [op True undefined, op 'c' undefined, op False False]
+
+T5684.hs:47:12: error:
+    • No instance for (B Char b2) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op True undefined, op 'c' undefined, op False False]
+      In an equation for ‘flop5’:
+          flop5 = [op True undefined, op 'c' undefined, op False False]
+
+T5684.hs:48:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op True undefined, op 'c' undefined, op False False]
+      In an equation for ‘flop5’:
+          flop5 = [op True undefined, op 'c' undefined, op False False]
+
+T5684.hs:52:12: error:
+    • No instance for (A b0) arising from a use of ‘op’
+    • In the expression: op True undefined
+      In the expression:
+        [op True undefined, op False False, op 'c' undefined]
+      In an equation for ‘flop6’:
+          flop6 = [op True undefined, op False False, op 'c' undefined]
+
+T5684.hs:53:12: error:
+    • No instance for (A Bool) arising from a use of ‘op’
+    • In the expression: op False False
+      In the expression:
+        [op True undefined, op False False, op 'c' undefined]
+      In an equation for ‘flop6’:
+          flop6 = [op True undefined, op False False, op 'c' undefined]
+
+T5684.hs:54:12: error:
+    • No instance for (B Char b1) arising from a use of ‘op’
+    • In the expression: op 'c' undefined
+      In the expression:
+        [op True undefined, op False False, op 'c' undefined]
+      In an equation for ‘flop6’:
+          flop6 = [op True undefined, op False False, op 'c' undefined]
diff --git a/testsuite/tests/typecheck/should_fail/T7851.stderr b/testsuite/tests/typecheck/should_fail/T7851.stderr
index 14efa7c7c9..b8ec6b8f32 100644
--- a/testsuite/tests/typecheck/should_fail/T7851.stderr
+++ b/testsuite/tests/typecheck/should_fail/T7851.stderr
@@ -1,7 +1,7 @@
 
 T7851.hs:5:10: error:
-    • Couldn't match expected type ‘IO a0’
-                  with actual type ‘a1 -> IO ()’
+    • Couldn't match expected type ‘IO a1’
+                  with actual type ‘a0 -> IO ()’
     • Probable cause: ‘print’ is applied to too few arguments
       In a stmt of a 'do' block: print
       In the expression:
diff --git a/testsuite/tests/typecheck/should_fail/tcfail001.stderr b/testsuite/tests/typecheck/should_fail/tcfail001.stderr
index 0b0a799c04..61604469e5 100644
--- a/testsuite/tests/typecheck/should_fail/tcfail001.stderr
+++ b/testsuite/tests/typecheck/should_fail/tcfail001.stderr
@@ -1,7 +1,7 @@
 
 tcfail001.hs:9:2: error:
     • Couldn't match expected type ‘[a]’
-                  with actual type ‘[t0] -> [t1]’
+                  with actual type ‘[t1] -> [t0]’
     • The equation(s) for ‘op’ have one argument,
       but its type ‘[a]’ has none
       In the instance declaration for ‘A [a]’