tcfail181.hs:17:9: error: [GHC-39999]
    • Could not deduce ‘Monad m0’ arising from a use of ‘foo’
      from the context: Monad m
        bound by the inferred type of
                   wog :: Monad m => p -> Something (m Bool) e
        at tcfail181.hs:17:1-30
      The type variable ‘m0’ is ambiguous
      Potentially matching instances:
        instance Monad IO -- Defined in ‘GHC.Base’
        instance Monad Maybe -- Defined in ‘GHC.Base’
        ...plus six others
        ...plus one instance involving out-of-scope types
        (use -fprint-potential-instances to see them all)
    • In the expression: foo
      In a record update at field ‘bar’,
      with type constructor ‘Something’
      and data constructor ‘Something’.
      In the expression: foo {bar = return True}