Any idea when this was added? I am relatively certain that it was not possible in Haskell 98, and admittedly most of my Haskell experience is a decade old.

I have picked up three well-regarded Haskell books over the past decade trying to get back into the language, and don't recall any mention of this capability.

That's another issue, the dearth of anything like tutorials or books on how to do something practical with Haskell, rather than the whirlwind tour of language features. I keep being told that serious software is being built in Haskell, but the knowledge of how to get from university-grade code to production-grade code is an unmarked wilderness that everyone must apparently navigate on their own.