RFC 140 migration: misleading CI error for aliases

[zeuner]

Describe the bug

When defining an alias for a top-level package in pkgs/top-level/all-packages.nix, the RFC 140 related CI will misinterpret it as a callPackage invocation and complain. Even if aliases were forbidden by RFC 140 (which isn't obvious, the public document lists them as "unresolved"), the error message should not be misleading.

Steps To Reproduce

Steps to reproduce the behavior:

1. Push PR that defines an alias in pkgs/top-level/all-packages.nix
2. See CI fail on "Check pkgs/by-name"

Expected behavior

Since there is no indication that aliases are disallowed, there should be no error at all. At the very least, it should not be misleading.

Additional context

Can be seen in #256115 (https://github.com/NixOS/nixpkgs/actions/runs/7732190624/job/21081562936?pr=256115)

Notify maintainers

Not sure where to lookup maintainers here. I guess @infinisil might be knowledgeable about this due to dedicated involvement in RFC 140 automation.

Metadata

Please run nix-shell -p nix-info --run "nix-info -m" and paste the result.

[user@system:~]$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"x86_64-linux"`
 - host os: `Linux 4.19.0-8-amd64, Ubuntu, 20.04.6 LTS (Focal Fossa), nobuild`
 - multi-user?: `no`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.16.1`
 - nixpkgs: `/nixpkgs`

Add a 👍 reaction to issues you find important.

[infinisil]

Thanks for the report! I'm already aware of this problem and created a PR to fix it yesterday: #285089

[infinisil]

Actually let's leave this open until the new tooling is used in CI