Troels Henriksen
It is very likely that issue 17386 is the issue. With
{-# OPTIONS_GHC -Wno-overlapping-patterns -Wno-incomplete-patterns -Wno-incomplete-uni-patterns -Wno-incomplete-record-updates #-}
my module(s) compile very quickly. I'll wait and see if GHC 9 does better before I try to create a smaller case (and now I at least have a workaround).
I have now tried it with GHC 9, and unfortunately it is still very slow. As time permits, I will see if I can come up with a self-contained module that illustrates the slowdown. I do have an idea for a optimisation: In all of the cases where coverage tracking takes a long time, I have a catch-all case at the bottom. I think that is a fairly common pattern, where a program tries to detect various special cases, before falling back to a general case. Perhaps coverage checking should have a short-circuiting check for whether there is an obvious catch-all case, and if so, not bother looking any closer? -- \ Troels /\ Henriksen