Installation fails with "cabal.project"

[serras]

Describe the bug
I am trying to use the head.hackage infrastructure to test a new branch of GHC. However, I cannot compile several of the packages due to a failing pattern match within. Cabal.

To Reproduce
I have the following cabal.project in a folder:

optional-packages: cabal-doctest-1.0.7/
extra-packages: aeson
with-compiler: /path/to/my/ghc/_build/stage1/bin/ghc
allow-newer: all
repository head.hackage.ghc.haskell.org
   url: https://ghc.gitlab.haskell.org/head.hackage/
   secure: True
   key-threshold: 3
   root-keys:
       f76d08be13e9a61a377a85e2fb63f4c5435d40f8feb3e12eb05905edb8cdea89
       7541f32a4ccca4f97aea3b22f5e593ba2c0267546016b992dfadcd2fe944e55d
       26021a13b401500c8eb2761ca95c61f2d625bfef951b939a8124ed12ecf07329

Now if I run the following command:

$ cabal new-install --lib aeson
...
Distribution/Client/CmdInstall.hs:(361,18)-(363,72): Non-exhaustive patterns in lambda

This behavior only happens for those packages whicch are mentioned in the cabal.project file (here, aeson and cabal-doctest).

Expected behavior
Cabal should not throw an exception, and if possible, should install the package.

System informataion

• Operating system: Mac OS X 10.14.6
• cabal, ghc versions: 3.0.0.0 (compiled using GHC 8.6.5), but using a custom branch of GHC for compiling packages