Hello.

haskell-src-exts-1.23.1 fails to build with new happy-2.2.1:

unused rules: 3
The grammar has 12 shift/reduce conflicts.
This is different from the number given in the expect directive
Error: [Cabal-7125]
Failed to build haskell-src-exts-1.23.1 (which is required by hs-src-exts-happy-0.1.0.0). See the build log above for details.

My guess is that this difference comes from this new commit, whereas haskell-src-exts currently expects 13:

> %expect 13

I documented this on a repo here, where the old index-state chooses older happy-2.2 (ok), but the newer index-state chooses happy-2.2.1 (fails). Incidentally, it would be nice if there was a way to force the older happy even with the newer index state e.g.

constraints: happy <2.2.1

But this doesn't seem to work for Build-Tools (and, I guess, build-tool-depends).

EDIT: Looks like this works:

constraints: any.happy <2.2.1

I'm not sure what should be done here e.g. this seems like it is probably a bug on haskell-src-exts. But I figured I'd make an issue here, since this may affect happy users more generally.

Thanks!