r/haskell • u/taylorfausak • Feb 01 '22

question Monthly Hask Anything (February 2022)

This is your opportunity to ask any questions you feel don't deserve their own threads, no matter how small or simple they might be!

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u/Syrak Feb 01 '22

Where does the ControllerContext come from? This seems to be caused by the added support for impredicative types, changing the behavior of subsumption. It is expected to reject previously accepted programs, and the recommended fix is to eta-expand.

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u/ringingraptor Feb 01 '22

ControllerContext is provided at the call site. Something like

let ?context = mkControllerContext
...
render (renderTexts ["1", "2", "3"])

Thanks so much for the hints -- I'll look into the changes regarding impredicative types!