Build from git HEAD fails for GHC 8.10

[erikd]

Describe the bug

First I ran into https://github.com/tweag/HaskellR/issues/374

Then trying to fix that, I cloned the repo and tried to build it and got:

> cabal build inline-r --minimize-conflict-set
Resolving dependencies...
Error: cabal: Could not resolve dependencies:
[__0] trying: inline-r-0.10.5 (user goal)
[__1] next goal: singletons-th (dependency of inline-r)
[__1] rejecting: singletons-th-3.1.1 (conflict: inline-r => singletons-th>=4)
[__1] skipping: singletons-th-3.1, singletons-th-3.0 (has the same
characteristics that caused the previous version to fail: excluded by
constraint '>=4' from 'inline-r')
[__1] fail (backjumping, conflict set: inline-r, singletons-th)
After searching the rest of the dependency tree exhaustively, these were the
goals I've had most trouble fulfilling: inline-r, singletons-th

To Reproduce Steps to reproduce the behavior.

git clone https://github.com/tweag/HaskellR
cd HaskellR
# create trivial cabal.project file
cabal build inline-r --minimize-conflict-set

Expected behavior I expect it to build

Environment

• OS name + version: Debian Texting
• Version of the code: commit c3ba1023480e26ade420896bcb629ceaad59f308
• GHC version: 8.10.7
• cabal version: 3.8.1.0

Additional context Contents of cabal.project

packages:
  H
  IHaskell
  inline-r

test-show-details: direct

[idontgetoutmuch]

Hi @erikd just to let you know that the principal maintainer has this

On March 2nd, I joined the Ukrainian military (the National Guard) to play my small part in defending Ukraine.

[erikd]

@idontgetoutmuch is that Roman?

[idontgetoutmuch]

@erikd yes

[erikd]

On Hackage, the maintainer is listed as Mathieu who I believe is French.

Anyway, I hope Roman stays safe.

[andreabedini]

The bounds change in 3e6b6804c419adbb53a5923149c4f6063d30d72e seem sa bit funny to me.

-                     , singletons >= 0.9 && < 3
+                     , singletons >= 3
+                     , singletons-th >= 3

There's no code change to warrant moving from singletons >= 0.9 to singletons >= 3, and we don't need singletons-th. I will see what I can do.

[erikd]

I seem to recall that singletons (and maybe also singletons-th) is tightly version locked with the GHC version. Therefore I usually remove any version bounds on singletons and let the compiler sort it out.

[andreabedini]

singletons-th yes (singletons-th-3.1.1 has base >=4.17 && <4.18), but singletons seems to be more lenient (singletons-3.0.2 has base >=4.9 && <4.18).

[mboes]

@andreabedini gotten somewhere?

[andreabedini]

@mboes We didn't end up needing to build this package at IOG so I had stopped. I will give it a second look (especially now that #379 is merged).

[mboes]

@andreabedini I saw you opened #381, which creates a whole new cabal-based CI workflow. The issue reported here can be reproduced with either Stack or cabal-install. It's just that #366 broke building with GHC 8.10. So I extracted the minimal change from your PR that fixes the problem. It's in #384.