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When trying to add constraints to the types of the arrow primitives I get a type error. I think that doing such a thing should be possible and I've attached the code I used to test this. The errors I get when using the arrow notation for the function test are as follows:

test :: Typeable a => R a a
test = proc n -> returnA -< n

bug-arrow.hs:15:8:
    Could not deduce (Typeable c) arising from a use of `arr'
    from the context (Typeable a)
      bound by the type signature for test :: Typeable a => R a a
      at bug-arrow.hs:14:9-27
    Possible fix:
      add (Typeable c) to the context of
        a type expected by the context: (b -> c) -> R b c
        or the type signature for test :: Typeable a => R a a
    In the expression: arr
    When checking that `arr' (needed by a syntactic construct)
      has the required type: forall b1 c1. (b1 -> c1) -> R b1 c1
      arising from a proc expression at bug-arrow.hs:15:8-29
    In the expression: proc n -> returnA -< n

bug-arrow.hs:15:8:
    Could not deduce (Typeable c) arising from a use of `>>>'
    from the context (Typeable a)
      bound by the type signature for test :: Typeable a => R a a
      at bug-arrow.hs:14:9-27
    Possible fix:
      add (Typeable c) to the context of
        a type expected by the context: R a1 b -> R b c -> R a1 c
        or the type signature for test :: Typeable a => R a a
    In the expression: (>>>)
    When checking that `(>>>)' (needed by a syntactic construct)
      has the required type: forall a2 b1 c1.
                             R a2 b1 -> R b1 c1 -> R a2 c1
      arising from a proc expression at bug-arrow.hs:15:8-29
    In the expression: proc n -> returnA -< n

bug-arrow.hs:15:8:
    Could not deduce (Typeable d) arising from a use of `first'
    from the context (Typeable a)
      bound by the type signature for test :: Typeable a => R a a
      at bug-arrow.hs:14:9-27
    Possible fix:
      add (Typeable d) to the context of
        a type expected by the context: R b c -> R (b, d) (c, d)
        or the type signature for test :: Typeable a => R a a
    In the expression: first
    When checking that `first' (needed by a syntactic construct)
      has the required type: forall b1 c1 d1.
                             R b1 c1 -> R (b1, d1) (c1, d1)
      arising from a proc expression at bug-arrow.hs:15:8-29
    In the expression: proc n -> returnA -< n

When I replace the definition with the translated core code (minus type applications and scoped type variables) the code compiles:

test :: Typeable a => R a a
test =
    (>>>)
      (arr (\ (n_apd) -> n_apd))
      ((>>>)
         (arr (\ (ds_dst) -> ds_dst))
         (returnA)
         )

Trac metadata

Trac field	Value
Version	7.6.2
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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