Hi, On 16/10/2021 10:55, Markus Läll wrote:
Is there any consensus on unticked promoted constructors -- are they generally safe to use?
Currently the warning is part of -Wall, but having promoted constructors unticked is just aesthetically nicer.
I don't know if there is a consensus, but I have long been of the opinion that -Wunticked-promoted-constructors should be dropped from -Wall and that GHC should not insert ticks when printing inferred types unless including them is necessary for disambiguation. In particular, as a library author I want to use DataKinds without my users having to know or care what it does. You can sometimes hide the ticks by defining a type synonym, e.g. data T = MkT type MkT = 'MkT but there are cases where GHC exposes the difference still, e.g. if you mention MkT in a class instance head. Cheers, Adam -- Adam Gundry, Haskell Consultant Well-Typed LLP, https://www.well-typed.com/ Registered in England & Wales, OC335890 118 Wymering Mansions, Wymering Road, London W9 2NF, England