typechecking too eager?

[Keean Schupke]

So, does that mean that ideally we would like it to type
check, but for implementation reasons it cannot easily
be done without a type signature?

I can use the type signature no problem.

    Keean.

Andres Loeh wrote:

>Hi there,
>
>  
>
>>The following code should compile (If the constructor
>>is valid, so is the function):
>>
>>data Test = Test (forall a . a)
>>test a = Test a
>>
>>However this fails to compile with the following error:
>>    
>>
>
>The current implementation of rank-n polymorphism
>(which is documented in the paper "Pratical type inference
>for arbitrary-rank types") does not "guess" polymorphic
>types for lambda-abstracted values.
>
>In this situation, this means that the variable "a"
>is assumed to have a monorphic type, which then cannot
>be passed to "Test" as an argument.
>
>Knowledge about polymorphism is passed down/inwards,
>but not up/outwards.
>
>This definition typechecks only if you add a type
>signature:
>
>test :: (forall a . a) -> Test
>
>If you want to know the reasons, read the paper. It explains
>the problems very well.
>
>Cheers,
>  Andres
>
>  
>