already defined Value at testdata/language-features/adt/gadt04.reject.lc:6:3:
  Value :: a -> forall m . M2 a m
  ^^^^^
and at testdata/language-features/adt/gadt04.reject.lc:3:3:
  Value :: a -> forall m . M a m
  ^^^^^
------------ trace
'M :: Type -> String -> Type
Value :: forall a . a -> forall (b :: String) . M a b
'MCase
  :: forall (a :: forall b (c :: String) -> M b c -> Type)
    -> (forall d . forall (e :: d) -> forall (f :: String) . a d f ('Value d e f))
      -> forall g (h :: String) . forall (i :: M g h) -> a g h i
match'M
  :: forall (a :: Type -> Type)
    -> (forall b (c :: String) -> a (M b c)) -> forall d -> a d -> a d
'M2 :: Type -> String -> Type
Value :: forall a . a -> forall (b :: String) . M2 a b
!already defined Value at testdata/language-features/adt/gadt04.reject.lc:6:3:
  Value :: a -> forall m . M2 a m
  ^^^^^
and at testdata/language-features/adt/gadt04.reject.lc:3:3:
  Value :: a -> forall m . M a m
  ^^^^^
------------ tooltips
testdata/language-features/adt/gadt04.reject.lc 2:6-2:7
    Type -> String -> Type | Type -> String -> Type | Type | Type | Type
      -> String -> Type | Type | Type | Type
testdata/language-features/adt/gadt04.reject.lc 2:6-3:33
    Type
testdata/language-features/adt/gadt04.reject.lc 2:11-2:15
    Type
testdata/language-features/adt/gadt04.reject.lc 2:19-2:25
    Type
testdata/language-features/adt/gadt04.reject.lc 2:19-2:33
    Type
testdata/language-features/adt/gadt04.reject.lc 2:29-2:33
    Type | Type
testdata/language-features/adt/gadt04.reject.lc 3:3-3:8
    forall a . a -> forall (b :: String) . M a b | M _c _a
testdata/language-features/adt/gadt04.reject.lc 3:3-3:33
    Type | Type | Type | Type
testdata/language-features/adt/gadt04.reject.lc 3:12-3:13
    _b
testdata/language-features/adt/gadt04.reject.lc 3:12-3:33
    Type
testdata/language-features/adt/gadt04.reject.lc 3:17-3:33
    Type
testdata/language-features/adt/gadt04.reject.lc 3:28-3:29
    Type -> String -> Type
testdata/language-features/adt/gadt04.reject.lc 3:28-3:31
    String -> Type
testdata/language-features/adt/gadt04.reject.lc 3:28-3:33
    Type | Type
testdata/language-features/adt/gadt04.reject.lc 3:30-3:31
    Type | Type
testdata/language-features/adt/gadt04.reject.lc 3:30-3:33
    M _c _a -> Type
testdata/language-features/adt/gadt04.reject.lc 3:32-3:33
    _b | String
testdata/language-features/adt/gadt04.reject.lc 5:6-5:8
    Type -> String -> Type
testdata/language-features/adt/gadt04.reject.lc 5:12-5:16
    Type
testdata/language-features/adt/gadt04.reject.lc 5:20-5:26
    Type
testdata/language-features/adt/gadt04.reject.lc 5:20-5:34
    Type
testdata/language-features/adt/gadt04.reject.lc 5:30-5:34
    Type | Type
testdata/language-features/adt/gadt04.reject.lc 6:12-6:13
    _b
testdata/language-features/adt/gadt04.reject.lc 6:12-6:34
    Type
testdata/language-features/adt/gadt04.reject.lc 6:17-6:34
    Type
testdata/language-features/adt/gadt04.reject.lc 6:28-6:30
    Type -> String -> Type
testdata/language-features/adt/gadt04.reject.lc 6:28-6:32
    String -> Type
testdata/language-features/adt/gadt04.reject.lc 6:28-6:34
    Type | Type
testdata/language-features/adt/gadt04.reject.lc 6:31-6:32
    Type
testdata/language-features/adt/gadt04.reject.lc 6:33-6:34
    _b