I have the following code

-- foo.hs
module Foo where

class Foo a where
    bar :: a -> a

instance Foo Int where
    bar i = i + 10

------------------

It fails to compile withe following error
*Foo> bar 10

<interactive>:1:4:
    Ambiguous type variable `t' in the constraints:
      `Num t' arising from the literal `10' at <interactive>:1:4-5
      `Foo t' arising from a use of `bar' at <interactive>:1:0-5
    Probable fix: add a type signature that fixes these type variable(s)
*Foo>

- Thanks
Amitava Shee