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

[Johannes Waldmann]

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.