Re: Proposal: Add conspicuously missing Functor instances for tuples

On Mon, Jan 18, 2016, at 13:22, Henning Thielemann wrote:

On Mon, 18 Jan 2016, John Wiegley wrote:

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> Henning Thielemann writes:

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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.

There may be an easier way, but one could write a Core-to-Core plugin that kills the build if it sees an expression like `fmap @(,)`.