[Haskell-cafe] NB: DO NOT USE `pure = return`

[Brandon Allbery]

Most likely because MonadOfNoReturn will transitionally define return =
pure, and instead of a compile error error you would end up with runtime
infinite loops.

On Mon, Jul 1, 2019 at 3:09 PM Johannes Waldmann <
johannes.waldmann at htwk-leipzig.de> wrote:

> Dear Cafe,
>
> the migration guide (for AMP)
>
>
> https://gitlab.haskell.org/ghc/ghc/wikis/migration/7.10#ghc-says-no-instance-for-applicative-
>
> contains this advice:
>
> instance Applicative Foo where
>     -- NB: DO NOT USE `pure = return`
>
> Why not? Because it would require another refactoring
> once "monad of no return" comes true?
>
> So defining `return` in the Monad instance should work fine until then?
> Which is when exactly? I can't quite make it out from
>
> https://gitlab.haskell.org/ghc/ghc/wikis/proposal/monad-of-no-return/discussion
>
>
> - J.W.
>
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-- 
brandon s allbery kf8nh
allbery.b at gmail.com
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