Hi Simon, a simplifier question... Roughly a year ago I started learning about imported Ids, their unfoldings etc. I have very small example program that compiles on Linux. ```haskell import GHC.Event main = print evtRead ``` `evtRead` is a newtype-wrapped Int. When you compile above program with HEAD GHC without optimisation, you'll see that `evtRead` gets passed directly to `show`. But with -O1 it's unfolding will be inlined, floated to toplevel, and dumped as static global data into the using Main module. This was not the case in GHC 8.4. Not sure about 8.6 (will check). Anyway here is the inlining notice that the simplifier gave me (-ddump-inlinings -dverbose-core2core)
Inlining done: GHC.Event.Internal.evtRead Inlined fn: (GHC.Types.I# 1#) `cast` (Sym (GHC.Event.Internal.N:Event[0]) :: GHC.Types.Coercible GHC.Types.Int GHC.Event.Internal.Event) Cont: Stop[BoringCtxt] GHC.Event.Internal.Event
I believe this is a regression, as copies of global data can pop up in potentially many different modules. What do you think? Which change could have caused this? Cheers, Gabor