[Haskell-cafe] What causes this "Ambiguous type variable" message (involving an existential type)?

James Cook falsifian at falsifian.org
Sat Jul 18 17:49:41 UTC 2020

On 2020-07-18 5:33 p.m., James Cook wrote:
> Hi haskell-cafe,
> I've run into a strange error. It's easy for me to work around, but I
> still would like to know what causes it.
> Here's a minimal example.

Oops, I just realized I'm not using existential types at all. A value of 
type T needs to be able to produce *any* instance of show requested, so 
the error makes sense.

Sorry for the noise. I'm resurrecting some old code of mine and 
misinterpreted what I was doing.


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