Proposal: add HasCallStack for all partial functions in base

[Henning Thielemann]

On Sun, 16 Jun 2019, Simon Jakobi via Libraries wrote:

> I like the idea of marking partial functions with HasCallStack.
> But I'd like to point out that we also have class methods where some but not all implementations are partial,
> such as foldr1 in Foldable.
> 
> Should methods like these also get a HasCallStack constraint?

I think only the partial implementations should get that constraint.