Migration advice for `hashable-1.4`

[sjakobi]

What's the best way to make code -Wredundant-constraints-clean with hashable-1.4 while retaining compatibility with hashable < 1.4?

In unordered-containers, I'd rather not have CPP-conditionals on every function that so far required both Eq and Hashable, like this:

f ::
#if MIN_VERSION_hashable(1,4,0)
  (Hashable k)
#else 
  (Eq k, Hashable k)
#endif
  => bla k

Is there a recommended way to achieve the same effect with less visual noise?

(CC @treeowl)

[phadej]

@sjakobi don't try. Turn the warning off for time being. That's why I suggested to do (another alterntative) release soon, with hashable >=1.4 lower bound.

[phadej]

a CPP hack is to do

#if MIN_VERSION_hashable(1,4,0)
#define HASHABLE(k) Hashable k
#else
#define HASHABLE(k) Eq k, Hashable k
#endif

f :: (HASHABLE(k)) => bla k

but the sooner you get rid of it, the saner you'll be.

[sjakobi]

Thanks for the advice, @phadej! Indeed it seems best not to change the constraints for now. We can consider requiring hashable >= 1.4 in a few months.

Maybe leave this issue open for a bit, so other users with similar questions can find it more easily.