## Summary My library package has a module which imports `Ghc.Prim`. If I use `-Werror=unused-packages`, ghc both requires `ghc-prim` to be listed as a dependency and requires it _not to_ be listed as a dependency. ## Steps to reproduce Note: `cabal` is used here for convenience, but is not required to reproduce. The `ghc` commands to reproduce are also given here. - have a cabal project for a library pacakge in the current directory - have a source file with `import Ghc.Prim`, which is listed in exposed-modules in the cabal file - cabal file's library.ghc-options includes `-Werror=unused-packages` - when the cabal file's library.build-depends includes ghc-prim: - `ghc -Werror=unused-packages src/A.hs -pacakge-id ghc-prim-0.8.0`, or `cabal build` gives this error: ``` <no location info>: error: [-Wunused-packages, -Werror=unused-packages] The following packages were specified via -package or -package-id flags, but were not needed for compilation: - ghc-prim-0.8.0 ``` - when the cabal file's library.build-depends _does not_ include ghc-prim: - `ghc -Werror=unused-packages src/A.hs`, or `cabal build` gives this error: ``` src/A.hs:3:1: error: Could not find module ‘Ghc.Prim’ Perhaps you meant GHC.Prim (needs flag -package-id ghc-prim-0.8.0) Use -v (or `:set -v` in ghci) to see a list of the files searched for. | 3 | import Ghc.Prim | ^^^^^^^^^^^^^^^ ``` ## Expected behavior Since `ghc-prim` is required for compilation, `-Werror=unused-packages` should not error saying that it is not required. ## Environment * GHC version used: 9.2.5 Optional: * Operating System: NixOS 22.11pre-git (Raccoon) * System Architecture: x86_64