$ nix-build -A emacs-macport
error:
       … while evaluating the attribute 'emacs-macport'

         at /Users/djm/src/personal/nixpkgs/pkgs/applications/editors/emacs/default.nix:57:5:

           56|
           57|     emacs-macport = callPackage (self.sources.emacs-macport) {
             |     ^
           58|       inherit gconf;

       … while evaluating a branch condition

         at /Users/djm/src/personal/nixpkgs/lib/customisation.nix:173:8:

          172|
          173|     in if missingArgs == [] then makeOverridable f allArgs else abort error;
             |        ^
          174|

       (stack trace truncated; use '--show-trace' to show the full trace)

       error: syntax error, unexpected '}', expecting '.' or '='

       at /Users/djm/src/personal/nixpkgs/pkgs/applications/editors/emacs/sources.nix:25:85:

           24|     '';
           25|     changelog = https://www.gnu.org/savannah-checkouts/gnu/emacs/news/NEWS.${version};
             |                                                                                     ^
           26|     license = lib.licenses.gpl3Plus;

$ nix-shell -p nix-info --run "nix-info -m"
 - system: `"aarch64-darwin"`
 - host os: `Darwin 22.5.0, macOS 13.4.1`
 - multi-user?: `yes`
 - sandbox: `no`
 - version: `nix-env (Nix) 2.15.1`
 - channels(user): `""`
 - channels(root): `""`
 - nixpkgs: `/nix/store/p2h0d2k7r835bp1dwy3hxzfzd74wywbg-source`