Type-checked examples are becoming more popular in the Scala community, e.g. using the tut tool. This is one of the few ways in which the Scala community appears to be ahead of the Haskell community, in terms of technology.
https://github.com/sol/doctest#readme - Very popular.
I do notice that after a while, I can get more and more from types alone, but I would never get to that point without examples first.
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I don't see why examples couldn't be type-checked though, so they never become out-dated – is there no way to do that with haddock?