Commit c45f8ceb authored by Simon Peyton Jones's avatar Simon Peyton Jones

Elaborate test for Trac #10403

parent ba7c8e59
{-# LANGUAGE PartialTypeSignatures #-}
{-# OPTIONS_GHC -fdefer-type-errors #-}
module T10403 where
data I a = I a
......@@ -11,9 +12,10 @@ instance Functor (B t) where
newtype H f = H (f ())
app :: H (B t)
app = h (H . I) (B ())
h :: _ => _
--h :: Functor m => (a -> b) -> m a -> H m
-- h :: Functor m => (a -> b) -> m a -> H m
h f b = (H . fmap (const ())) (fmap f b)
h2 :: _
-- h2 :: Functor m => (a -> b) -> m a -> H m
h2 f b = (H . fmap (const ())) (fmap f b)
T10403.hs:17:6: warning:
Found hole ‘_’ with inferred constraints: Functor f
In the type signature for ‘h’: _ => _
T10403.hs:17:11: warning:
Found hole ‘_’ with type: (a -> b) -> f a -> H f
Where: ‘f’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:19:1
‘b’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:19:1
‘a’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:19:1
In the type signature for ‘h’: _ => _
T10403.hs:15:6: warning:
Found hole ‘_’ with inferred constraints: Functor f
In the type signature for ‘h’: _ => _
T10403.hs:15:11: warning:
Found hole ‘_’ with type: (a -> b) -> f a -> H f
Where: ‘f’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:17:1
‘b’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:17:1
‘a’ is a rigid type variable bound by
the inferred type of h :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:17:1
In the type signature for ‘h’: _ => _
T10403.hs:19:7: warning:
Found hole ‘_’ with type: (a -> b) -> f a -> H f
Where: ‘f’ is a rigid type variable bound by
the inferred type of h2 :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:21:1
‘b’ is a rigid type variable bound by
the inferred type of h2 :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:21:1
‘a’ is a rigid type variable bound by
the inferred type of h2 :: Functor f => (a -> b) -> f a -> H f
at T10403.hs:21:1
In the type signature for ‘h2’: _
T10403.hs:21:1: warning:
No instance for (Functor f)
When checking that ‘h2’ has the inferred type
h2 :: forall (f :: * -> *) b a. (a -> b) -> f a -> H f
Probable cause: the inferred type is ambiguous
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