What approaches and tools do Haskell developers take to guard against this? I assume in the head case a Maybe would be a better return type? But then why doesn't the Haskell core do that in the head function?
The type system isn't helping you at all there.
The feeling I had was that much of the prelude stuff was there to provide for beautiful, terse examples of functional programming and less to protect a software engineer.
I've just started my Haskell journey and the undefined paths through partial function implementation caught me by surprise.
Just skimming Wikipedia it looks like I would want to use "total/strong functional programming" but apparently "total functional programming is not Turing-complete"
https://en.wikipedia.org/wiki/Total_functional_programming
Also found this on the Haskell site after some more googling:
It isn't, but usually Turing completeness isn't what you want. Take a look at Idris, where functions may explicitly be total or not-necessarily-total.