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@supki
Created November 27, 2018 10:20
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$300
>>> data M a = M (Proxy M)
<interactive>:21:12: error:
• Data constructor ‘M’ has existential type variables, a context, or a specialised result type
M :: forall k (a :: k) k. Proxy (k -> *) (M k) -> M k a
(Use ExistentialQuantification or GADTs to allow this)
• In the definition of data constructor ‘M’
In the data type declaration for ‘M’
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