[Git][ghc/ghc][master] Rephrase error message to say "visible arguments" (#24318)

Marge Bot (@marge-bot) gitlab at gitlab.haskell.org
Thu Mar 7 21:29:11 UTC 2024



Marge Bot pushed to branch master at Glasgow Haskell Compiler / GHC


Commits:
9cd9efb4 by Vladislav Zavialov at 2024-03-07T13:01:54+03:00
Rephrase error message to say "visible arguments" (#24318)

* Main change: make the error message generated by mkFunTysMsg more
  accurate by changing "value arguments" to "visible arguments".

* Refactor: define a new type synonym VisArity and use it instead of
  Arity in a few places.

It might be the case that there other places in the compiler that should
talk about visible arguments rather than value arguments, but I haven't
tried to find them all, focusing only on the error message reported in
the ticket.

- - - - -


24 changed files:

- compiler/GHC/Tc/Gen/Match.hs
- compiler/GHC/Tc/Utils/Unify.hs
- compiler/GHC/Types/Basic.hs
- testsuite/tests/ado/ado002.stderr
- testsuite/tests/ghci/scripts/Defer02.stderr
- testsuite/tests/indexed-types/should_compile/T10806.stderr
- testsuite/tests/indexed-types/should_fail/T8518.stderr
- testsuite/tests/rep-poly/T23903.stderr
- testsuite/tests/th/T5358.stderr
- testsuite/tests/typecheck/should_fail/DoExpansion2.stderr
- testsuite/tests/typecheck/should_fail/DoExpansion3.stderr
- testsuite/tests/typecheck/should_fail/FD1.stderr
- testsuite/tests/typecheck/should_fail/T13902.stderr
- testsuite/tests/typecheck/should_fail/T17139.stderr
- + testsuite/tests/typecheck/should_fail/T24318.hs
- + testsuite/tests/typecheck/should_fail/T24318.stderr
- testsuite/tests/typecheck/should_fail/T8603.stderr
- testsuite/tests/typecheck/should_fail/T9605.stderr
- testsuite/tests/typecheck/should_fail/all.T
- testsuite/tests/typecheck/should_fail/tcfail001.stderr
- testsuite/tests/typecheck/should_fail/tcfail140.stderr
- testsuite/tests/typecheck/should_fail/tcfail175.stderr
- testsuite/tests/vdq-rta/should_fail/T22326_fail_n_args.stderr
- testsuite/tests/warnings/should_fail/CaretDiagnostics1.stderr


Changes:

=====================================
compiler/GHC/Tc/Gen/Match.hs
=====================================
@@ -75,7 +75,7 @@ import GHC.Driver.DynFlags ( getDynFlags )
 import GHC.Types.Name
 import GHC.Types.Id
 import GHC.Types.SrcLoc
-import GHC.Types.Basic( Arity, isDoExpansionGenerated )
+import GHC.Types.Basic( VisArity, isDoExpansionGenerated )
 
 import Control.Monad
 import Control.Arrow ( second )
@@ -1207,7 +1207,7 @@ the variables they bind into scope, and typecheck the thing_inside.
 --       The MatchGroup for `f` has arity 2, not 3
 checkArgCounts :: AnnoBody body
                => MatchGroup GhcRn (LocatedA (body GhcRn))
-               -> TcM Arity
+               -> TcM VisArity
 checkArgCounts (MG { mg_alts = L _ [] })
     = return 1 -- See Note [Empty MatchGroups] in GHC.Rename.Bind
                --   case e of {} or \case {}
@@ -1227,6 +1227,6 @@ checkArgCounts (MG { mg_alts = L _ (match1:matches) })
     n_args1 = reqd_args_in_match match1
     mb_bad_matches = NE.nonEmpty [m | m <- matches, reqd_args_in_match m /= n_args1]
 
-    reqd_args_in_match :: LocatedA (Match GhcRn body1) -> Arity
+    reqd_args_in_match :: LocatedA (Match GhcRn body1) -> VisArity
     -- Counts the number of /required/ args in the match
     reqd_args_in_match (L _ (Match { m_pats = pats })) = count (isVisArgPat . unLoc) pats


=====================================
compiler/GHC/Tc/Utils/Unify.hs
=====================================
@@ -751,7 +751,7 @@ Example:
 matchExpectedFunTys :: forall a.
                        ExpectedFunTyOrigin  -- See Note [Herald for matchExpectedFunTys]
                     -> UserTypeCtxt
-                    -> Arity
+                    -> VisArity
                     -> ExpSigmaType
                     -> ([ExpPatType] -> ExpRhoType -> TcM a)
                     -> TcM (HsWrapper, a)
@@ -777,7 +777,7 @@ matchExpectedFunTys herald _ arity (Infer inf_res) thing_inside
 matchExpectedFunTys herald ctx arity (Check top_ty) thing_inside
   = check 0 [] top_ty
   where
-    check :: Arity -> [ExpPatType] -> TcSigmaType -> TcM (HsWrapper, a)
+    check :: VisArity -> [ExpPatType] -> TcSigmaType -> TcM (HsWrapper, a)
     -- `check` is called only in the Check{} case
     -- It collects rev_pat_tys in reversed order
     -- n_so_far is the number of /visible/ arguments seen so far:
@@ -875,7 +875,7 @@ matchExpectedFunTys herald ctx arity (Check top_ty) thing_inside
         defer n_so_far rev_pat_tys res_ty
 
     ------------
-    defer :: Arity -> [ExpPatType] -> TcRhoType -> TcM (HsWrapper, a)
+    defer :: VisArity -> [ExpPatType] -> TcRhoType -> TcM (HsWrapper, a)
     defer n_so_far rev_pat_tys fun_ty
       = do { more_arg_tys <- mapM (new_check_arg_ty herald) [n_so_far + 1 .. arity]
            ; let all_pats = reverse rev_pat_tys ++ map mkCheckExpFunPatTy more_arg_tys
@@ -898,19 +898,15 @@ new_check_arg_ty herald arg_pos -- Position for error messages only
        ; return (mkScaled mult arg_ty) }
 
 mkFunTysMsg :: ExpectedFunTyOrigin
-            -> (Arity, TcType)
+            -> (VisArity, TcType)
             -> TidyEnv -> ZonkM (TidyEnv, SDoc)
 -- See Note [Reporting application arity errors]
-mkFunTysMsg herald (n_val_args_in_call, fun_ty) env
+mkFunTysMsg herald (n_vis_args_in_call, fun_ty) env
   = do { (env', fun_ty) <- zonkTidyTcType env fun_ty
 
        ; let (pi_ty_bndrs, _) = splitPiTys fun_ty
-
-             -- `all_arg_tys` contains visible quantifiers only, so their number matches
-             -- the number of arguments that the user needs to pass to the function.
              n_fun_args = count isVisiblePiTyBinder pi_ty_bndrs
-
-             msg | n_val_args_in_call <= n_fun_args  -- Enough args, in the end
+             msg | n_vis_args_in_call <= n_fun_args  -- Enough args, in the end
                  = text "In the result of a function call"
                  | otherwise
                  = hang (full_herald <> comma)
@@ -921,7 +917,8 @@ mkFunTysMsg herald (n_val_args_in_call, fun_ty) env
        ; return (env', msg) }
  where
   full_herald = pprExpectedFunTyHerald herald
-            <+> speakNOf n_val_args_in_call (text "value argument")
+            <+> speakNOf n_vis_args_in_call (text "visible argument")
+             -- What are "visible" arguments? See Note [Visibility and arity] in GHC.Types.Basic
 
 
 {- Note [Reporting application arity errors]
@@ -931,8 +928,8 @@ and the call  foo = f 3 4 5
 We'd like to get an error like:
 
     • Couldn't match expected type ‘t0 -> t’ with actual type ‘Int’
-    • The function ‘f’ is applied to three value arguments,
-        but its type ‘Int -> Int -> Int’ has only two
+    • The function ‘f’ is applied to three visible arguments,           -- What are "visible" arguments?
+        but its type ‘Int -> Int -> Int’ has only two                   -- See Note [Visibility and arity] in GHC.Types.Basic
 
 That is what `mkFunTysMsg` tries to do.  But what is the "type of the function".
 Most obviously, we can report its full, polymorphic type; that is simple and
@@ -943,7 +940,7 @@ We get this error:
     • Couldn't match type ‘Int’ with ‘t0 -> t’
       Expected: Int -> t0 -> t
         Actual: Int -> Int
-    • The function ‘f’ is applied to three value arguments,
+    • The function ‘f’ is applied to three visible arguments,
         but its type ‘Bool -> t Int Int’ has only one
 
 That's not /quite/ right beause we can instantiate `t` to an arrow and get


=====================================
compiler/GHC/Types/Basic.hs
=====================================
@@ -28,7 +28,7 @@ module GHC.Types.Basic (
 
         ConTag, ConTagZ, fIRST_TAG,
 
-        Arity, RepArity, JoinArity, FullArgCount,
+        Arity, VisArity, RepArity, JoinArity, FullArgCount,
         JoinPointHood(..), isJoinPoint,
 
         Alignment, mkAlignment, alignmentOf, alignmentBytes,
@@ -183,6 +183,10 @@ instance Binary LeftOrRight where
 -- See also Note [Definition of arity] in "GHC.Core.Opt.Arity"
 type Arity = Int
 
+-- | Syntactic (visibility) arity, i.e. the number of visible arguments.
+-- See Note [Visibility and arity]
+type VisArity = Int
+
 -- | Representation Arity
 --
 -- The number of represented arguments that can be applied to a value before it does
@@ -203,6 +207,71 @@ type JoinArity = Int
 -- both type and value arguments!
 type FullArgCount = Int
 
+{- Note [Visibility and arity]
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+Arity is the number of arguments that a function expects. In a curried language
+like Haskell, there is more than one way to count those arguments.
+
+* `Arity` is the classic notion of arity, concerned with evalution, so it counts
+  the number of /value/ arguments that need to be supplied before evaluation can
+  take place, as described in notes
+    Note [Definition of arity]      in GHC.Core.Opt.Arity
+    Note [Arity and function types] in GHC.Types.Id.Info
+
+  Examples:
+    Int                       has arity == 0
+    Int -> Int                has arity <= 1
+    Int -> Bool -> Int        has arity <= 2
+  We write (<=) rather than (==) as sometimes evaluation can occur before all
+  value arguments are supplied, depending on the actual function definition.
+
+  This evaluation-focused notion of arity ignores type arguments, so:
+    forall a.   a             has arity == 0
+    forall a.   a -> a        has arity <= 1
+    forall a b. a -> b -> a   has arity <= 2
+  This is true regardless of ForAllTyFlag, so the arity is also unaffected by
+  (forall {a}. ty) or (forall a -> ty).
+
+  Class dictionaries count towards the arity, as they are passed at runtime
+    forall a.   (Num a)        => a            has arity <= 1
+    forall a.   (Num a)        => a -> a       has arity <= 2
+    forall a b. (Num a, Ord b) => a -> b -> a  has arity <= 4
+
+* `VisArity` is the syntactic notion of arity. It is the number of /visible/
+  arguments, i.e. arguments that occur visibly in the source code.
+
+  In a function call `f x y z`, we can confidently say that f's vis-arity >= 3,
+  simply because we see three arguments [x,y,z]. We write (>=) rather than (==)
+  as this could be a partial application.
+
+  At definition sites, we can acquire an underapproximation of vis-arity by
+  counting the patterns on the LHS, e.g. `f a b = rhs` has vis-arity >= 2.
+  The actual vis-arity can be higher if there is a lambda on the RHS,
+  e.g. `f a b = \c -> rhs`.
+
+  If we look at the types, we can observe the following
+    * function arrows   (a -> b)        add to the vis-arity
+    * visible foralls   (forall a -> b) add to the vis-arity
+    * constraint arrows (a => b)        do not affect the vis-arity
+    * invisible foralls (forall a. b)   do not affect the vis-arity
+
+  This means that ForAllTyFlag matters for VisArity (in contrast to Arity),
+  while the type/value distinction is unimportant (again in contrast to Arity).
+
+  Examples:
+    Int                         -- vis-arity == 0   (no args)
+    Int -> Int                  -- vis-arity == 1   (1 funarg)
+    forall a. a -> a            -- vis-arity == 1   (1 funarg)
+    forall a. Num a => a -> a   -- vis-arity == 1   (1 funarg)
+    forall a -> Num a => a      -- vis-arity == 1   (1 req tyarg, 0 funargs)
+    forall a -> a -> a          -- vis-arity == 2   (1 req tyarg, 1 funarg)
+    Int -> forall a -> Int      -- vis-arity == 2   (1 funarg, 1 req tyarg)
+
+  Wrinkle: with TypeApplications and TypeAbstractions, it is possible to visibly
+  bind and pass invisible arguments, e.g. `f @a x = ...` or `f @Int 42`. Those
+  @-prefixed arguments are ignored for the purposes of vis-arity.
+-}
+
 {-
 ************************************************************************
 *                                                                      *


=====================================
testsuite/tests/ado/ado002.stderr
=====================================
@@ -2,7 +2,7 @@
 ado002.hs:8:8: error: [GHC-83865]
     • Couldn't match expected type: Char -> IO b0
                   with actual type: IO Char
-    • The function ‘getChar’ is applied to one value argument,
+    • The function ‘getChar’ is applied to one visible argument,
         but its type ‘IO Char’ has none
       In a stmt of a 'do' block: y <- getChar 'a'
       In the expression:
@@ -45,7 +45,7 @@ ado002.hs:15:13: error: [GHC-83865]
 ado002.hs:23:9: error: [GHC-83865]
     • Couldn't match expected type: Char -> IO a0
                   with actual type: IO Char
-    • The function ‘getChar’ is applied to one value argument,
+    • The function ‘getChar’ is applied to one visible argument,
         but its type ‘IO Char’ has none
       In a stmt of a 'do' block: x5 <- getChar x4
       In the expression:


=====================================
testsuite/tests/ghci/scripts/Defer02.stderr
=====================================
@@ -26,7 +26,7 @@ Defer01.hs:24:4: warning: [GHC-40564] [-Winaccessible-code (in -Wdefault)]
 
 Defer01.hs:30:5: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefault)]
     • Couldn't match expected type ‘Char -> t’ with actual type ‘Char’
-    • The function ‘e’ is applied to one value argument,
+    • The function ‘e’ is applied to one visible argument,
         but its type ‘Char’ has none
       In the expression: e 'q'
       In an equation for ‘f’: f = e 'q'
@@ -95,7 +95,7 @@ Defer01.hs:49:5: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefault)]
 (deferred type error)
 *** Exception: Defer01.hs:30:5: error: [GHC-83865]
     • Couldn't match expected type ‘Char -> t’ with actual type ‘Char’
-    • The function ‘e’ is applied to one value argument,
+    • The function ‘e’ is applied to one visible argument,
         but its type ‘Char’ has none
       In the expression: e 'q'
       In an equation for ‘f’: f = e 'q'


=====================================
testsuite/tests/indexed-types/should_compile/T10806.stderr
=====================================
@@ -2,7 +2,7 @@
 T10806.hs:11:32: error: [GHC-83865]
     • Couldn't match expected type: Char -> Bool
                   with actual type: IO ()
-    • The function ‘print’ is applied to two value arguments,
+    • The function ‘print’ is applied to two visible arguments,
         but its type ‘Show a => a -> IO ()’ has only one
       In the expression: print 'x' 'y'
       In an equation for ‘triggersLoop’:


=====================================
testsuite/tests/indexed-types/should_fail/T8518.stderr
=====================================
@@ -2,7 +2,7 @@
 T8518.hs:14:18: error: [GHC-83865]
     • Couldn't match expected type: Z c -> B c -> t0
                   with actual type: F c
-    • The function ‘rpt’ is applied to four value arguments,
+    • The function ‘rpt’ is applied to four visible arguments,
         but its type ‘t1 -> t2 -> F t2’ has only two
       In the expression: rpt (4 :: Int) c z b
       In an equation for ‘callCont’:


=====================================
testsuite/tests/rep-poly/T23903.stderr
=====================================
@@ -6,5 +6,5 @@ T23903.hs:21:1: error: [GHC-55287]
         t0 :: TYPE cx0
       Cannot unify ‘Rep a’ with the type variable ‘cx0’
       because the former is not a concrete ‘RuntimeRep’.
-    • The equation for ‘f’ has one value argument,
+    • The equation for ‘f’ has one visible argument,
         but its type ‘a #-> ()’ has none


=====================================
testsuite/tests/th/T5358.stderr
=====================================
@@ -1,17 +1,17 @@
 
 T5358.hs:7:1: error: [GHC-83865]
     • Couldn't match expected type ‘Int’ with actual type ‘t1 -> t1’
-    • The equation for ‘t1’ has one value argument,
+    • The equation for ‘t1’ has one visible argument,
         but its type ‘Int’ has none
 
 T5358.hs:8:1: error: [GHC-83865]
     • Couldn't match expected type ‘Int’ with actual type ‘t0 -> t0’
-    • The equation for ‘t2’ has one value argument,
+    • The equation for ‘t2’ has one visible argument,
         but its type ‘Int’ has none
 
 T5358.hs:10:13: error: [GHC-83865]
     • Couldn't match expected type ‘t -> a0’ with actual type ‘Int’
-    • The function ‘t1’ is applied to one value argument,
+    • The function ‘t1’ is applied to one visible argument,
         but its type ‘Int’ has none
       In the first argument of ‘(==)’, namely ‘t1 x’
       In the expression: t1 x == t2 x
@@ -21,7 +21,7 @@ T5358.hs:10:13: error: [GHC-83865]
 
 T5358.hs:10:21: error: [GHC-83865]
     • Couldn't match expected type ‘t -> a0’ with actual type ‘Int’
-    • The function ‘t2’ is applied to one value argument,
+    • The function ‘t2’ is applied to one visible argument,
         but its type ‘Int’ has none
       In the second argument of ‘(==)’, namely ‘t2 x’
       In the expression: t1 x == t2 x


=====================================
testsuite/tests/typecheck/should_fail/DoExpansion2.stderr
=====================================
@@ -55,7 +55,7 @@ DoExpansion2.hs:31:19: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefaul
 DoExpansion2.hs:34:22: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefault)]
     • Couldn't match expected type: t0 -> IO (Maybe Int)
                   with actual type: IO String
-    • The function ‘getVal’ is applied to two value arguments,
+    • The function ‘getVal’ is applied to two visible arguments,
         but its type ‘Int -> IO String’ has only one
       In a stmt of a 'do' block: Just x <- getVal 3 4
       In the expression:


=====================================
testsuite/tests/typecheck/should_fail/DoExpansion3.stderr
=====================================
@@ -10,7 +10,7 @@ DoExpansion3.hs:15:20: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefaul
 DoExpansion3.hs:18:20: warning: [GHC-83865] [-Wdeferred-type-errors (in -Wdefault)]
     • Couldn't match expected type: t0 -> t
                   with actual type: IO Char
-    • The function ‘getChar’ is applied to one value argument,
+    • The function ‘getChar’ is applied to one visible argument,
         but its type ‘IO Char’ has none
       In the expression: getChar 2
       In an equation for ‘y’: y = getChar 2


=====================================
testsuite/tests/typecheck/should_fail/FD1.stderr
=====================================
@@ -5,6 +5,6 @@ FD1.hs:16:1: error: [GHC-25897]
         the type signature for:
           plus :: forall a. E a (Int -> Int) => Int -> a
         at FD1.hs:15:1-38
-    • The equation for ‘plus’ has two value arguments,
+    • The equation for ‘plus’ has two visible arguments,
         but its type ‘Int -> a’ has only one
     • Relevant bindings include plus :: Int -> a (bound at FD1.hs:16:1)


=====================================
testsuite/tests/typecheck/should_fail/T13902.stderr
=====================================
@@ -1,7 +1,7 @@
 
 T13902.hs:8:5: error: [GHC-83865]
     • Couldn't match expected type ‘t0 -> Int’ with actual type ‘Int’
-    • The function ‘f’ is applied to two value arguments,
+    • The function ‘f’ is applied to two visible arguments,
         but its type ‘a -> a’ has only one
       In the expression: f @Int 42 5
       In an equation for ‘g’: g = f @Int 42 5


=====================================
testsuite/tests/typecheck/should_fail/T17139.stderr
=====================================
@@ -7,7 +7,7 @@ T17139.hs:15:16: error: [GHC-88464]
                  lift :: forall a b (f :: * -> *). (a -> b) -> TypeFam f (a -> b)
                at T17139.hs:14:1-38
     • In the expression: _ (f <*> x)
-      The lambda expression ‘\ x -> ...’ has one value argument,
+      The lambda expression ‘\ x -> ...’ has one visible argument,
         but its type ‘TypeFam f (a -> b)’ has none
       In the expression: \ x -> _ (f <*> x)
     • Relevant bindings include


=====================================
testsuite/tests/typecheck/should_fail/T24318.hs
=====================================
@@ -0,0 +1,8 @@
+{-# LANGUAGE ExplicitNamespaces, RequiredTypeArguments #-}
+
+module T24318 where
+
+import Data.Kind
+
+f :: forall (a :: Type) -> Bool
+f (type t) x = True


=====================================
testsuite/tests/typecheck/should_fail/T24318.stderr
=====================================
@@ -0,0 +1,5 @@
+
+T24318.hs:8:1: error: [GHC-83865]
+    • Couldn't match expected type ‘Bool’ with actual type ‘t0 -> Bool’
+    • The equation for ‘f’ has two visible arguments,
+        but its type ‘forall a -> Bool’ has only one


=====================================
testsuite/tests/typecheck/should_fail/T8603.stderr
=====================================
@@ -6,7 +6,7 @@ T8603.hs:33:17: error: [GHC-18872]
         [a2] :: *
       Expected: [a2] -> StateT s RV a0
         Actual: t0 ((->) [a1]) (StateT s RV a0)
-    • The function ‘lift’ is applied to two value arguments,
+    • The function ‘lift’ is applied to two visible arguments,
         but its type ‘(Control.Monad.Trans.Class.MonadTrans t, Monad m) =>
                       m a -> t m a’
         has only one


=====================================
testsuite/tests/typecheck/should_fail/T9605.stderr
=====================================
@@ -3,7 +3,7 @@ T9605.hs:7:6: error: [GHC-83865]
     • Couldn't match type ‘Bool’ with ‘m Bool’
       Expected: t0 -> m Bool
         Actual: t0 -> Bool
-    • The function ‘f1’ is applied to one value argument,
+    • The function ‘f1’ is applied to one visible argument,
         but its type ‘Monad m => m Bool’ has none
       In the expression: f1 undefined
       In an equation for ‘f2’: f2 = f1 undefined


=====================================
testsuite/tests/typecheck/should_fail/all.T
=====================================
@@ -712,6 +712,7 @@ test('ErrorIndexLinks', normal, compile_fail, ['-fprint-error-index-links=always
 test('T24064', normal, compile_fail, [''])
 test('T24298', normal, compile_fail, [''])
 test('T24279', normal, compile_fail, [''])
+test('T24318', normal, compile_fail, [''])
 
 # all the various do expansion fail messages
 test('DoExpansion1', normal, compile, ['-fdefer-type-errors'])


=====================================
testsuite/tests/typecheck/should_fail/tcfail001.stderr
=====================================
@@ -2,7 +2,7 @@
 tcfail001.hs:9:2: error: [GHC-83865]
     • Couldn't match expected type: [a]
                   with actual type: [a0] -> [a1]
-    • The equation for ‘op’ has one value argument,
+    • The equation for ‘op’ has one visible argument,
         but its type ‘[a]’ has none
       In the instance declaration for ‘A [a]’
     • Relevant bindings include op :: [a] (bound at tcfail001.hs:9:2)


=====================================
testsuite/tests/typecheck/should_fail/tcfail140.stderr
=====================================
@@ -1,7 +1,7 @@
 
 tcfail140.hs:11:7: error: [GHC-83865]
     • Couldn't match expected type ‘t1 -> t’ with actual type ‘Int’
-    • The function ‘f’ is applied to two value arguments,
+    • The function ‘f’ is applied to two visible arguments,
         but its type ‘Int -> Int’ has only one
       In the expression: f 3 9
       In an equation for ‘bar’: bar = f 3 9
@@ -9,7 +9,7 @@ tcfail140.hs:11:7: error: [GHC-83865]
 
 tcfail140.hs:13:10: error: [GHC-83865]
     • Couldn't match expected type ‘t2 -> t’ with actual type ‘Int’
-    • The function ‘f’ is applied to two value arguments,
+    • The function ‘f’ is applied to two visible arguments,
         but its type ‘Int -> Int’ has only one
       In the expression: 3 `f` 4
       In an equation for ‘rot’: rot xs = 3 `f` 4
@@ -28,11 +28,11 @@ tcfail140.hs:15:15: error: [GHC-83865]
 tcfail140.hs:17:8: error: [GHC-27346]
     • The data constructor ‘Just’ should have 1 argument, but has been given none
     • In the pattern: Just
-      The lambda expression ‘\ Just x -> ...’ has two value arguments,
+      The lambda expression ‘\ Just x -> ...’ has two visible arguments,
         but its type ‘Maybe a -> a’ has only one
       In the expression: ((\ Just x -> x) :: Maybe a -> a) (Just 1)
 
 tcfail140.hs:20:1: error: [GHC-83865]
     • Couldn't match expected type ‘Int’ with actual type ‘t0 -> Bool’
-    • The equation for ‘g’ has two value arguments,
+    • The equation for ‘g’ has two visible arguments,
         but its type ‘Int -> Int’ has only one


=====================================
testsuite/tests/typecheck/should_fail/tcfail175.stderr
=====================================
@@ -6,7 +6,7 @@ tcfail175.hs:11:1: error: [GHC-25897]
         the type signature for:
           evalRHS :: forall a. Int -> a
         at tcfail175.hs:10:1-19
-    • The equation for ‘evalRHS’ has three value arguments,
+    • The equation for ‘evalRHS’ has three visible arguments,
         but its type ‘Int -> a’ has only one
     • Relevant bindings include
         evalRHS :: Int -> a (bound at tcfail175.hs:11:1)


=====================================
testsuite/tests/vdq-rta/should_fail/T22326_fail_n_args.stderr
=====================================
@@ -5,5 +5,5 @@ T22326_fail_n_args.hs:6:1: error: [GHC-25897]
         the type signature for:
           f :: a -> forall b -> b
         at T22326_fail_n_args.hs:6:1-26
-    • The equation for ‘f’ has three value arguments,
+    • The equation for ‘f’ has three visible arguments,
         but its type ‘a -> forall b -> b’ has only two


=====================================
testsuite/tests/warnings/should_fail/CaretDiagnostics1.stderr
=====================================
@@ -37,7 +37,7 @@ CaretDiagnostics1.hs:13:7-11: error: [GHC-83865]
 
 CaretDiagnostics1.hs:(13,16)-(14,13): error: [GHC-83865]
     • Couldn't match expected type ‘Char -> t0’ with actual type ‘()’
-    • The function ‘()’ is applied to one value argument,
+    • The function ‘()’ is applied to one visible argument,
         but its type ‘()’ has none
       In the expression: () '0'
       In a case alternative: "γηξ" -> () '0'



View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9cd9efb4de3757fd5eaec006739f75cef288e5eb

-- 
View it on GitLab: https://gitlab.haskell.org/ghc/ghc/-/commit/9cd9efb4de3757fd5eaec006739f75cef288e5eb
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