Not picking on Idris here, because it's typical (first noticed it in PureScript). But note this: Idris> Just 3 Just 3 : Maybe Integer Idris> Nothing (input):Can't infer argument a to Nothing Idris> I understand the surface reason ("what kind of Nothing is it?"), but... 1/2
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Same with PureScript. Even though the `a` does not appear in `Nothing`, the type is still `Maybe a` - class elaboration happens at the type level, not the value level (it can't in general). It works in Elm because showing values is fully magic and cannot be user-specified.
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For what it's worth, I don't think a fully magic `Show` is a bad idea, since it should only be used for debugging etc. IMO anyway. We just haven't figured out the details of how we'd want to do it given you can private constructors and all sorts of things like that.
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