Give seq a more precise type and remove magic

`GHC.Prim.seq` previously had the rather plain type:

    seq :: forall a b. a -> b -> b

However, it also had a special typing rule to applications
where `b` is not of kind `Type`.

Issue #17440 noted that levity polymorphism allows us to rather give
it the more precise type:

    seq :: forall (r :: RuntimeRep) a (b :: TYPE r). a -> b -> b

This allows us to remove the special typing rule that we previously
required to allow applications on unlifted arguments. T9404 contains a
non-Type application of `seq` which should verify that this works as
expected.

Closes #17440.

11 files changed, 142 insertions, 170 deletions

diff --git a/compiler/basicTypes/MkId.hs b/compiler/basicTypes/MkId.hs
index d9d23b1235..593f9ac3a9 100644
--- a/compiler/basicTypes/MkId.hs
+++ b/compiler/basicTypes/MkId.hs
@@ -1392,7 +1392,6 @@ seqId = pcMiscPrelId seqName ty info
   where
     info = noCafIdInfo `setInlinePragInfo` inline_prag
                        `setUnfoldingInfo`  mkCompulsoryUnfolding rhs
-                       `setNeverLevPoly`   ty
 
     inline_prag
          = alwaysInlinePragma `setInlinePragmaActivation` ActiveAfter
@@ -1402,11 +1401,15 @@ seqId = pcMiscPrelId seqName ty info
                   -- LHS of rules.  That way we can have rules for 'seq';
                   -- see Note [seqId magic]
 
-    ty  = mkSpecForAllTys [alphaTyVar,betaTyVar]
-                          (mkVisFunTy alphaTy (mkVisFunTy betaTy betaTy))
+    -- seq :: forall (r :: RuntimeRep) a (b :: TYPE r). a -> b -> b
+    ty  =
+      mkInvForAllTy runtimeRep2TyVar
+      $ mkSpecForAllTys [alphaTyVar, openBetaTyVar]
+      $ mkVisFunTy alphaTy (mkVisFunTy openBetaTy openBetaTy)
 
-    [x,y] = mkTemplateLocals [alphaTy, betaTy]
-    rhs = mkLams [alphaTyVar,betaTyVar,x,y] (Case (Var x) x betaTy [(DEFAULT, [], Var y)])
+    [x,y] = mkTemplateLocals [alphaTy, openBetaTy]
+    rhs = mkLams ([runtimeRep2TyVar, alphaTyVar, openBetaTyVar, x, y]) $
+          Case (Var x) x openBetaTy [(DEFAULT, [], Var y)]
 
 ------------------------------------------------
 lazyId :: Id    -- See Note [lazyId magic]
@@ -1492,19 +1495,20 @@ Note [seqId magic]
 ~~~~~~~~~~~~~~~~~~
 'GHC.Prim.seq' is special in several ways.
 
-a) In source Haskell its second arg can have an unboxed type
-      x `seq` (v +# w)
-   But see Note [Typing rule for seq] in TcExpr, which
-   explains why we give seq itself an ordinary type
-         seq :: forall a b. a -> b -> b
-   and treat it as a language construct from a typing point of view.
+a) Its fixity is set in LoadIface.ghcPrimIface
 
-b) Its fixity is set in LoadIface.ghcPrimIface
-
-c) It has quite a bit of desugaring magic.
+b) It has quite a bit of desugaring magic.
    See DsUtils.hs Note [Desugaring seq (1)] and (2) and (3)
 
-d) There is some special rule handing: Note [User-defined RULES for seq]
+c) There is some special rule handing: Note [User-defined RULES for seq]
+
+Historical note:
+    In TcExpr we used to need a special typing rule for 'seq', to handle calls
+    whose second argument had an unboxed type, e.g.  x `seq` 3#
+
+    However, with levity polymorphism we can now give seq the type seq ::
+    forall (r :: RuntimeRep) a (b :: TYPE r). a -> b -> b which handles this
+    case without special treatment in the typechecker.
 
 Note [User-defined RULES for seq]
 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
@@ -1530,13 +1534,16 @@ If we wrote
   RULE "f/seq" forall n e.  seq (f n) e = seq n e
 with rule arity 2, then two bad things would happen:
 
-  - The magical desugaring done in Note [seqId magic] item (c)
+  - The magical desugaring done in Note [seqId magic] item (b)
     for saturated application of 'seq' would turn the LHS into
     a case expression!
 
   - The code in Simplify.rebuildCase would need to actually supply
     the value argument, which turns out to be awkward.
 
+See also: Note [User-defined RULES for seq] in Simplify.
+
+
 Note [lazyId magic]
 ~~~~~~~~~~~~~~~~~~~
 lazy :: forall a?. a? -> a?   (i.e. works for unboxed types too)
diff --git a/compiler/deSugar/DsUtils.hs b/compiler/deSugar/DsUtils.hs
index 8559e9ae85..b76c4f0592 100644
--- a/compiler/deSugar/DsUtils.hs
+++ b/compiler/deSugar/DsUtils.hs
@@ -408,82 +408,88 @@ mkErrorAppDs err_id ty msg = do
     return (mkApps (Var err_id) [Type (getRuntimeRep ty), Type ty, core_msg])
 
 {-
-'mkCoreAppDs' and 'mkCoreAppsDs' hand the special-case desugaring of 'seq'.
-
-Note [Desugaring seq (1)]  cf #1031
-~~~~~~~~~~~~~~~~~~~~~~~~~
-   f x y = x `seq` (y `seq` (# x,y #))
-
-The [CoreSyn let/app invariant] means that, other things being equal, because
-the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:
-
-   f x y = case (y `seq` (# x,y #)) of v -> x `seq` v
-
-But that is bad for two reasons:
-  (a) we now evaluate y before x, and
-  (b) we can't bind v to an unboxed pair
-
-Seq is very, very special!  So we recognise it right here, and desugar to
-        case x of _ -> case y of _ -> (# x,y #)
-
-Note [Desugaring seq (2)]  cf #2273
-~~~~~~~~~~~~~~~~~~~~~~~~~
-Consider
-   let chp = case b of { True -> fst x; False -> 0 }
-   in chp `seq` ...chp...
-Here the seq is designed to plug the space leak of retaining (snd x)
-for too long.
-
-If we rely on the ordinary inlining of seq, we'll get
-   let chp = case b of { True -> fst x; False -> 0 }
-   case chp of _ { I# -> ...chp... }
-
-But since chp is cheap, and the case is an alluring contet, we'll
-inline chp into the case scrutinee.  Now there is only one use of chp,
-so we'll inline a second copy.  Alas, we've now ruined the purpose of
-the seq, by re-introducing the space leak:
-    case (case b of {True -> fst x; False -> 0}) of
-      I# _ -> ...case b of {True -> fst x; False -> 0}...
-
-We can try to avoid doing this by ensuring that the binder-swap in the
-case happens, so we get his at an early stage:
-   case chp of chp2 { I# -> ...chp2... }
-But this is fragile.  The real culprit is the source program.  Perhaps we
-should have said explicitly
-   let !chp2 = chp in ...chp2...
-
-But that's painful.  So the code here does a little hack to make seq
-more robust: a saturated application of 'seq' is turned *directly* into
-the case expression, thus:
-   x  `seq` e2 ==> case x of x -> e2    -- Note shadowing!
-   e1 `seq` e2 ==> case x of _ -> e2
-
-So we desugar our example to:
-   let chp = case b of { True -> fst x; False -> 0 }
-   case chp of chp { I# -> ...chp... }
-And now all is well.
-
-The reason it's a hack is because if you define mySeq=seq, the hack
-won't work on mySeq.
-
-Note [Desugaring seq (3)] cf #2409
-~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
-The isLocalId ensures that we don't turn
-        True `seq` e
-into
-        case True of True { ... }
-which stupidly tries to bind the datacon 'True'.
+'mkCoreAppDs' and 'mkCoreAppsDs' handle the special-case desugaring of 'seq'.
+
+Note [Desugaring seq]
+~~~~~~~~~~~~~~~~~~~~~
+
+There are a few subtleties in the desugaring of `seq`:
+
+ 1. (as described in #1031)
+
+    Consider,
+       f x y = x `seq` (y `seq` (# x,y #))
+
+    The [CoreSyn let/app invariant] means that, other things being equal, because
+    the argument to the outer 'seq' has an unlifted type, we'll use call-by-value thus:
+
+       f x y = case (y `seq` (# x,y #)) of v -> x `seq` v
+
+    But that is bad for two reasons:
+      (a) we now evaluate y before x, and
+      (b) we can't bind v to an unboxed pair
+
+    Seq is very, very special!  So we recognise it right here, and desugar to
+            case x of _ -> case y of _ -> (# x,y #)
+
+ 2. (as described in #2273)
+
+    Consider
+       let chp = case b of { True -> fst x; False -> 0 }
+       in chp `seq` ...chp...
+    Here the seq is designed to plug the space leak of retaining (snd x)
+    for too long.
+
+    If we rely on the ordinary inlining of seq, we'll get
+       let chp = case b of { True -> fst x; False -> 0 }
+       case chp of _ { I# -> ...chp... }
+
+    But since chp is cheap, and the case is an alluring contet, we'll
+    inline chp into the case scrutinee.  Now there is only one use of chp,
+    so we'll inline a second copy.  Alas, we've now ruined the purpose of
+    the seq, by re-introducing the space leak:
+        case (case b of {True -> fst x; False -> 0}) of
+          I# _ -> ...case b of {True -> fst x; False -> 0}...
+
+    We can try to avoid doing this by ensuring that the binder-swap in the
+    case happens, so we get his at an early stage:
+       case chp of chp2 { I# -> ...chp2... }
+    But this is fragile.  The real culprit is the source program.  Perhaps we
+    should have said explicitly
+       let !chp2 = chp in ...chp2...
+
+    But that's painful.  So the code here does a little hack to make seq
+    more robust: a saturated application of 'seq' is turned *directly* into
+    the case expression, thus:
+       x  `seq` e2 ==> case x of x -> e2    -- Note shadowing!
+       e1 `seq` e2 ==> case x of _ -> e2
+
+    So we desugar our example to:
+       let chp = case b of { True -> fst x; False -> 0 }
+       case chp of chp { I# -> ...chp... }
+    And now all is well.
+
+    The reason it's a hack is because if you define mySeq=seq, the hack
+    won't work on mySeq.
+
+ 3. (as described in #2409)
+
+    The isLocalId ensures that we don't turn
+            True `seq` e
+    into
+            case True of True { ... }
+    which stupidly tries to bind the datacon 'True'.
 -}
 
 -- NB: Make sure the argument is not levity polymorphic
 mkCoreAppDs  :: SDoc -> CoreExpr -> CoreExpr -> CoreExpr
-mkCoreAppDs _ (Var f `App` Type ty1 `App` Type ty2 `App` arg1) arg2
-  | f `hasKey` seqIdKey            -- Note [Desugaring seq (1), (2)]
+mkCoreAppDs _ (Var f `App` Type _r `App` Type ty1 `App` Type ty2 `App` arg1) arg2
+  | f `hasKey` seqIdKey            -- Note [Desugaring seq], points (1) and (2)
   = Case arg1 case_bndr ty2 [(DEFAULT,[],arg2)]
   where
     case_bndr = case arg1 of
                    Var v1 | isInternalName (idName v1)
-                          -> v1        -- Note [Desugaring seq (2) and (3)]
+                          -> v1        -- Note [Desugaring seq], points (2) and (3)
                    _      -> mkWildValBinder ty1
 
 mkCoreAppDs s fun arg = mkCoreApp s fun arg  -- The rest is done in MkCore
diff --git a/compiler/simplCore/Simplify.hs b/compiler/simplCore/Simplify.hs
index 795b0f5654..569bcfd3dc 100644
--- a/compiler/simplCore/Simplify.hs
+++ b/compiler/simplCore/Simplify.hs
@@ -2090,11 +2090,16 @@ trySeqRules in_env scrut rhs cont
     no_cast_scrut = drop_casts scrut
     scrut_ty  = exprType no_cast_scrut
     seq_id_ty = idType seqId
+    res1_ty   = piResultTy seq_id_ty rhs_rep
+    res2_ty   = piResultTy res1_ty   scrut_ty
     rhs_ty    = substTy in_env (exprType rhs)
-    out_args  = [ TyArg { as_arg_ty  = scrut_ty
+    rhs_rep   = getRuntimeRep rhs_ty
+    out_args  = [ TyArg { as_arg_ty  = rhs_rep
                         , as_hole_ty = seq_id_ty }
+                , TyArg { as_arg_ty  = scrut_ty
+                        , as_hole_ty = res1_ty }
                 , TyArg { as_arg_ty  = rhs_ty
-                       , as_hole_ty  = piResultTy seq_id_ty scrut_ty }
+                        , as_hole_ty = res2_ty }
                 , ValArg no_cast_scrut]
     rule_cont = ApplyToVal { sc_dup = NoDup, sc_arg = rhs
                            , sc_env = in_env, sc_cont = cont }
diff --git a/compiler/typecheck/TcExpr.hs b/compiler/typecheck/TcExpr.hs
index b7a6779325..c7921070f6 100644
--- a/compiler/typecheck/TcExpr.hs
+++ b/compiler/typecheck/TcExpr.hs
@@ -63,9 +63,8 @@ import TyCoSubst (substTyWithInScope)
 import Type
 import TcEvidence
 import VarSet
-import MkId( seqId )
 import TysWiredIn
-import TysPrim( intPrimTy, mkTemplateTyVars, tYPE )
+import TysPrim( intPrimTy )
 import PrimOp( tagToEnumKey )
 import PrelNames
 import DynFlags
@@ -335,40 +334,10 @@ rule just for saturated applications of ($).
   * Decompose it; should be of form (arg2_ty -> res_ty),
        where arg2_ty might be a polytype
   * Use arg2_ty to typecheck arg2
-
-Note [Typing rule for seq]
-~~~~~~~~~~~~~~~~~~~~~~~~~~
-We want to allow
-       x `seq` (# p,q #)
-which suggests this type for seq:
-   seq :: forall (a:*) (b:Open). a -> b -> b,
-with (b:Open) meaning that be can be instantiated with an unboxed
-tuple.  The trouble is that this might accept a partially-applied
-'seq', and I'm just not certain that would work.  I'm only sure it's
-only going to work when it's fully applied, so it turns into
-    case x of _ -> (# p,q #)
-
-So it seems more uniform to treat 'seq' as if it was a language
-construct.
-
-See also Note [seqId magic] in MkId
 -}
 
 tcExpr expr@(OpApp fix arg1 op arg2) res_ty
   | (L loc (HsVar _ (L lv op_name))) <- op
-  , op_name `hasKey` seqIdKey           -- Note [Typing rule for seq]
-  = do { arg1_ty <- newFlexiTyVarTy liftedTypeKind
-       ; let arg2_exp_ty = res_ty
-       ; arg1' <- tcArg op arg1 arg1_ty 1
-       ; arg2' <- addErrCtxt (funAppCtxt op arg2 2) $
-                  tc_poly_expr_nc arg2 arg2_exp_ty
-       ; arg2_ty <- readExpType arg2_exp_ty
-       ; op_id <- tcLookupId op_name
-       ; let op' = L loc (mkHsWrap (mkWpTyApps [arg1_ty, arg2_ty])
-                                   (HsVar noExtField (L lv op_id)))
-       ; return $ OpApp fix arg1' op' arg2' }
-
-  | (L loc (HsVar _ (L lv op_name))) <- op
   , op_name `hasKey` dollarIdKey        -- Note [Typing rule for ($)]
   = do { traceTc "Application rule" (ppr op)
        ; (arg1', arg1_ty) <- tcInferSigma arg1
@@ -1161,26 +1130,11 @@ tcApp m_herald fun@(L loc (HsRecFld _ fld_lbl)) args res_ty
        ; (tc_fun, fun_ty) <- tcInferRecSelId (Unambiguous sel_name lbl)
        ; tcFunApp m_herald fun (L loc tc_fun) fun_ty args res_ty }
 
-tcApp m_herald fun@(L loc (HsVar _ (L _ fun_id))) args res_ty
+tcApp _m_herald (L loc (HsVar _ (L _ fun_id))) args res_ty
   -- Special typing rule for tagToEnum#
   | fun_id `hasKey` tagToEnumKey
   , n_val_args == 1
   = tcTagToEnum loc fun_id args res_ty
-
-  -- Special typing rule for 'seq'
-  -- In the saturated case, behave as if seq had type
-  --    forall a (b::TYPE r). a -> b -> b
-  -- for some type r.  See Note [Typing rule for seq]
-  | fun_id `hasKey` seqIdKey
-  , n_val_args == 2
-  = do { rep <- newFlexiTyVarTy runtimeRepTy
-       ; let [alpha, beta] = mkTemplateTyVars [liftedTypeKind, tYPE rep]
-             seq_ty = mkSpecForAllTys [alpha,beta]
-                      (mkTyVarTy alpha `mkVisFunTy` mkTyVarTy beta `mkVisFunTy` mkTyVarTy beta)
-             seq_fun = L loc (HsVar noExtField (L loc seqId))
-             -- seq_ty = forall (a:*) (b:TYPE r). a -> b -> b
-             -- where 'r' is a meta type variable
-        ; tcFunApp m_herald fun seq_fun seq_ty args res_ty }
   where
     n_val_args = count isHsValArg args
 
diff --git a/testsuite/tests/simplCore/should_run/SeqRule.hs b/testsuite/tests/simplCore/should_run/SeqRule.hs
index 29a1951209..406add55ca 100644
--- a/testsuite/tests/simplCore/should_run/SeqRule.hs
+++ b/testsuite/tests/simplCore/should_run/SeqRule.hs
@@ -2,7 +2,7 @@
 -- This test checks that the magic treatment of RULES 
 -- for 'seq' works right. 
 --
--- See Note [RULES for seq] in MkId for more details
+-- See Note [User-defined RULES for seq] in MkId for more details
 
 module Main where
 
diff --git a/testsuite/tests/typecheck/should_compile/T13050.stderr b/testsuite/tests/typecheck/should_compile/T13050.stderr
index 36e22ae3f8..87b1312b4b 100644
--- a/testsuite/tests/typecheck/should_compile/T13050.stderr
+++ b/testsuite/tests/typecheck/should_compile/T13050.stderr
@@ -12,10 +12,6 @@ T13050.hs:4:9: warning: [-Wtyped-holes (in -Wdefault)]
         f :: Int -> Int -> Int (bound at T13050.hs:4:1)
         g :: Int -> Int -> Int (bound at T13050.hs:5:1)
         q :: Int -> Int -> Int (bound at T13050.hs:6:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T13050.hs:1:8-17
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
@@ -76,6 +72,10 @@ T13050.hs:4:9: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T13050.hs:1:8-17
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
@@ -98,10 +98,6 @@ T13050.hs:5:11: warning: [-Wtyped-holes (in -Wdefault)]
         g :: Int -> Int -> Int (bound at T13050.hs:5:1)
         f :: Int -> Int -> Int (defined at T13050.hs:4:1)
         q :: Int -> Int -> Int (bound at T13050.hs:6:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T13050.hs:1:8-17
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
@@ -162,6 +158,10 @@ T13050.hs:5:11: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T13050.hs:1:8-17
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
@@ -185,10 +185,6 @@ T13050.hs:6:11: warning: [-Wtyped-holes (in -Wdefault)]
         q :: Int -> Int -> Int (bound at T13050.hs:6:1)
         f :: Int -> Int -> Int (defined at T13050.hs:4:1)
         g :: Int -> Int -> Int (defined at T13050.hs:5:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T13050.hs:1:8-17
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
@@ -249,6 +245,10 @@ T13050.hs:6:11: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T13050.hs:1:8-17
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T13050.hs:1:8-17
diff --git a/testsuite/tests/typecheck/should_compile/T14590.stderr b/testsuite/tests/typecheck/should_compile/T14590.stderr
index 455898be1a..52ecc8335d 100644
--- a/testsuite/tests/typecheck/should_compile/T14590.stderr
+++ b/testsuite/tests/typecheck/should_compile/T14590.stderr
@@ -13,10 +13,6 @@ T14590.hs:4:13: warning: [-Wtyped-holes (in -Wdefault)]
         f2 :: Int -> Int -> Int (bound at T14590.hs:5:1)
         f3 :: Int -> Int -> Int (bound at T14590.hs:6:1)
         f4 :: Int -> Int -> Int (bound at T14590.hs:7:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T14590.hs:1:8-13
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -77,6 +73,10 @@ T14590.hs:4:13: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T14590.hs:1:8-13
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -101,10 +101,6 @@ T14590.hs:5:13: warning: [-Wtyped-holes (in -Wdefault)]
         f1 :: Int -> Int -> Int (defined at T14590.hs:4:1)
         f3 :: Int -> Int -> Int (bound at T14590.hs:6:1)
         f4 :: Int -> Int -> Int (bound at T14590.hs:7:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T14590.hs:1:8-13
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -165,6 +161,10 @@ T14590.hs:5:13: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T14590.hs:1:8-13
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -188,10 +188,6 @@ T14590.hs:6:11: warning: [-Wtyped-holes (in -Wdefault)]
         f1 :: Int -> Int -> Int (defined at T14590.hs:4:1)
         f2 :: Int -> Int -> Int (defined at T14590.hs:5:1)
         f4 :: Int -> Int -> Int (bound at T14590.hs:7:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T14590.hs:1:8-13
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -252,6 +248,10 @@ T14590.hs:6:11: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T14590.hs:1:8-13
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -276,10 +276,6 @@ T14590.hs:7:11: warning: [-Wtyped-holes (in -Wdefault)]
         f1 :: Int -> Int -> Int (defined at T14590.hs:4:1)
         f2 :: Int -> Int -> Int (defined at T14590.hs:5:1)
         f3 :: Int -> Int -> Int (defined at T14590.hs:6:1)
-        seq :: forall a b. a -> b -> b
-          with seq @Int @Int
-          (imported from ‘Prelude’ at T14590.hs:1:8-13
-           (and originally defined in ‘GHC.Prim’))
         (-) :: forall a. Num a => a -> a -> a
           with (-) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
@@ -340,6 +336,10 @@ T14590.hs:7:11: warning: [-Wtyped-holes (in -Wdefault)]
           with min @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
            (and originally defined in ‘GHC.Classes’))
+        seq :: forall a b. a -> b -> b
+          with seq @Int @Int
+          (imported from ‘Prelude’ at T14590.hs:1:8-13
+           (and originally defined in ‘GHC.Prim’))
         return :: forall (m :: * -> *) a. Monad m => a -> m a
           with return @((->) Int) @Int
           (imported from ‘Prelude’ at T14590.hs:1:8-13
diff --git a/testsuite/tests/typecheck/should_compile/abstract_refinement_hole_fits.stderr b/testsuite/tests/typecheck/should_compile/abstract_refinement_hole_fits.stderr
index 227df63ecc..e422b8629e 100644
--- a/testsuite/tests/typecheck/should_compile/abstract_refinement_hole_fits.stderr
+++ b/testsuite/tests/typecheck/should_compile/abstract_refinement_hole_fits.stderr
@@ -108,10 +108,10 @@ abstract_refinement_hole_fits.hs:4:5: warning: [-Wtyped-holes (in -Wdefault)]
           where fst :: forall a b. (a, b) -> a
         snd (_ :: (a0, [Integer] -> Integer))
           where snd :: forall a b. (a, b) -> b
-        seq (_ :: a13) (_ :: [Integer] -> Integer)
-          where seq :: forall a b. a -> b -> b
         const (_ :: [Integer] -> Integer) (_ :: b6)
           where const :: forall a b. a -> b -> a
+        seq (_ :: a13) (_ :: [Integer] -> Integer)
+          where seq :: forall a b. a -> b -> b
         ($) (_ :: a5 -> [Integer] -> Integer) (_ :: a5)
           where ($) :: forall a b. (a -> b) -> a -> b
         return (_ :: [Integer] -> Integer) (_ :: t1)
@@ -228,10 +228,10 @@ abstract_refinement_hole_fits.hs:7:5: warning: [-Wtyped-holes (in -Wdefault)]
           where fst :: forall a b. (a, b) -> a
         snd (_ :: (a0, Integer -> [Integer] -> Integer))
           where snd :: forall a b. (a, b) -> b
-        seq (_ :: a13) (_ :: Integer -> [Integer] -> Integer)
-          where seq :: forall a b. a -> b -> b
         const (_ :: Integer -> [Integer] -> Integer) (_ :: b6)
           where const :: forall a b. a -> b -> a
+        seq (_ :: a13) (_ :: Integer -> [Integer] -> Integer)
+          where seq :: forall a b. a -> b -> b
         ($) (_ :: a5 -> Integer -> [Integer] -> Integer) (_ :: a5)
           where ($) :: forall a b. (a -> b) -> a -> b
         return (_ :: Integer -> [Integer] -> Integer) (_ :: t1)
diff --git a/testsuite/tests/typecheck/should_compile/holes.stderr b/testsuite/tests/typecheck/should_compile/holes.stderr
index 016c31372b..bcf7dc060d 100644
--- a/testsuite/tests/typecheck/should_compile/holes.stderr
+++ b/testsuite/tests/typecheck/should_compile/holes.stderr
@@ -164,7 +164,6 @@ holes.hs:11:15: warning: [-Wtyped-holes (in -Wdefault)]
         quot :: forall a. Integral a => a -> a -> a
         quotRem :: forall a. Integral a => a -> a -> (a, a)
         rem :: forall a. Integral a => a -> a -> a
-        seq :: forall a b. a -> b -> b
         zip :: forall a b. [a] -> [b] -> [(a, b)]
         fst :: forall a b. (a, b) -> a
         snd :: forall a b. (a, b) -> b
@@ -185,6 +184,7 @@ holes.hs:11:15: warning: [-Wtyped-holes (in -Wdefault)]
                           a -> (b, a)
         round :: forall a b. (RealFrac a, Integral b) => a -> b
         truncate :: forall a b. (RealFrac a, Integral b) => a -> b
+        seq :: forall a b. a -> b -> b
         ($) :: forall a b. (a -> b) -> a -> b
         either :: forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
         curry :: forall a b c. ((a, b) -> c) -> a -> b -> c
diff --git a/testsuite/tests/typecheck/should_compile/holes3.stderr b/testsuite/tests/typecheck/should_compile/holes3.stderr
index bad5877d2e..7a8f513f25 100644
--- a/testsuite/tests/typecheck/should_compile/holes3.stderr
+++ b/testsuite/tests/typecheck/should_compile/holes3.stderr
@@ -167,7 +167,6 @@ holes3.hs:11:15: error:
         quot :: forall a. Integral a => a -> a -> a
         quotRem :: forall a. Integral a => a -> a -> (a, a)
         rem :: forall a. Integral a => a -> a -> a
-        seq :: forall a b. a -> b -> b
         zip :: forall a b. [a] -> [b] -> [(a, b)]
         fst :: forall a b. (a, b) -> a
         snd :: forall a b. (a, b) -> b
@@ -188,6 +187,7 @@ holes3.hs:11:15: error:
                           a -> (b, a)
         round :: forall a b. (RealFrac a, Integral b) => a -> b
         truncate :: forall a b. (RealFrac a, Integral b) => a -> b
+        seq :: forall a b. a -> b -> b
         ($) :: forall a b. (a -> b) -> a -> b
         either :: forall a c b. (a -> c) -> (b -> c) -> Either a b -> c
         curry :: forall a b c. ((a, b) -> c) -> a -> b -> c
diff --git a/testsuite/tests/warnings/should_compile/PluralS.stderr b/testsuite/tests/warnings/should_compile/PluralS.stderr
index d03efa5ad6..42c81daf5f 100644
--- a/testsuite/tests/warnings/should_compile/PluralS.stderr
+++ b/testsuite/tests/warnings/should_compile/PluralS.stderr
@@ -1,7 +1,7 @@
 
 PluralS.hs:15:17: warning: [-Wtype-defaults (in -Wall)]
     • Defaulting the following constraint to type ‘Integer’
-        Num t0 arising from the literal ‘123’
+        Num a0 arising from the literal ‘123’
     • In the first argument of ‘seq’, namely ‘123’
       In the expression: 123 `seq` ()
       In an equation for ‘defaultingNum’: defaultingNum = 123 `seq` ()