[Haskell-cafe] Reverse Show instance

Cannot deduce (Show x) from context (Show (x, y)). Cannot deduce (Show y) from context (Show (x, y)). Um... seriously? From Prelude, we have Show x, Show y => Show (x, y) So clearly it works in the forward direction. But apparently not in the reverse direction. Is this a bug or a feature? (I.e., is there some obscure possibility I haven't thought of which means that doing the reverse inference would be incorrect?)