Sam, Richard, Adam, Vlad, Ryan, and other people interested in GHC's type system. Following discussion with Richard, I have created a new ticket #20686 for Make the design of defaulting explicithttps://gitlab.haskell.org/ghc/ghc/-/issues/20686. This should inform !6851 which is trying to finish up Concrete# constraints. Please have a look - we 'd love your views on The Choice. Richard especially, but everyone really: feel free to edit the Description to make it more clear/accurate. I propose to treat it as our master design document. Simon PS: I am leaving Microsoft at the end of November 2021, at which point simonpj@microsoft.commailto:simonpj@microsoft.com will cease to work. Use simon.peytonjones@gmail.commailto:simon.peytonjones@gmail.com instead. (For now, it just forwards to simonpj@microsoft.com.)