[Haskell-cafe] Re: Ambiguous type with PolymorphicComponents

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(...)

When you have

data Test = Test (forall w. (C1 w, C2 w, ..., Cn w) => w)

and

function (Test w) = classmethod w,

there is no way to decide which instance to use, hence the type variable is ambiguous. (...)

But, then, how can I reach the data inside a polymorphic component? Or, better, what can I do with it? If I say: function (Test w) = classmethod (w :: specificType) then I have to suppose that w is always of 'specificType', and this may not be true. Thanks, Maurício