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T2494.hs:15:14: error: [GHC-25897]
• Couldn't match type ‘b’ with ‘a’
Expected: Maybe (m a) -> Maybe (m a)
Actual: Maybe (m b) -> Maybe (m b)
‘b’ is a rigid type variable bound by
the RULE "foo/foo"
at T2494.hs:(12,1)-(15,33)
‘a’ is a rigid type variable bound by
the RULE "foo/foo"
at T2494.hs:(12,1)-(15,33)
• In the first argument of ‘foo’, namely ‘g’
In the second argument of ‘foo’, namely ‘(foo g x)’
In the expression: foo f (foo g x)
• Relevant bindings include
f :: forall (m :: * -> *). Monad m => Maybe (m a) -> Maybe (m a)
(bound at T2494.hs:13:11)
g :: forall (m :: * -> *). Monad m => Maybe (m b) -> Maybe (m b)
(bound at T2494.hs:14:11)
x :: Maybe a (bound at T2494.hs:14:65)
T2494.hs:15:30: error: [GHC-25897]
• Couldn't match type ‘b’ with ‘a’
Expected: Maybe (m a) -> Maybe (m a)
Actual: Maybe (m b) -> Maybe (m b)
‘b’ is a rigid type variable bound by
the RULE "foo/foo"
at T2494.hs:(12,1)-(15,33)
‘a’ is a rigid type variable bound by
the RULE "foo/foo"
at T2494.hs:(12,1)-(15,33)
• In the second argument of ‘(.)’, namely ‘g’
In the first argument of ‘foo’, namely ‘(f . g)’
In the expression: foo (f . g) x
• Relevant bindings include
f :: forall (m :: * -> *). Monad m => Maybe (m a) -> Maybe (m a)
(bound at T2494.hs:13:11)
g :: forall (m :: * -> *). Monad m => Maybe (m b) -> Maybe (m b)
(bound at T2494.hs:14:11)
x :: Maybe a (bound at T2494.hs:14:65)
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