Proposal: Add conspicuously missing Functor instances for tuples

[Henning Thielemann]

On Mon, 18 Jan 2016, John Wiegley wrote:

>>>>>> Henning Thielemann <lemming at henning-thielemann.de> writes:
>
>> I would never use such an instance. Can I be warned if I accidentally use it
>> anyway?
>
> I don't know why "I wouldn't use it" should extend to "it shouldn't exist".

Because I cannot turn it off and I cannot get warning. It is inserted by 
GHC whenever it matches, even if I made a mistake when programming.