testsuite/tests/typecheck/should_fail/T8883.stderr


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T8883.hs:20:1: error:
    Non type-variable argument in the constraint: Functor (PF a)
    (Use FlexibleContexts to permit this)
    When checking the inferred type
      fold :: forall b a.
              (Functor (PF a), Regular a) =>
              (PF a b -> b) -> a -> b