nix flake show fails

[teto]

Describe the bug

I use https://github.com/oxalica/nil as a nix LSP server, which is quite practical. Not sure if my setup or nil changed but recently nil has started freaking out whenever it sees an error in flakes (which lead me to find issues in my own flakes). That includes this repo:

nix flake show github:numtide/treefmt-nix/27107cf3dfdc3c809d2477954d92fc2cc68b4401
├───formatter
│   ├───aarch64-darwin omitted (use '--all-systems' to show)
│   ├───aarch64-linux omitted (use '--all-systems' to show)
│   ├───x86_64-darwin omitted (use '--all-systems' to show)
error:
       … while evaluating the attribute 'checks.x86_64-linux.wrapper'

         at /nix/store/qyyw6dd6lqlhz3cqap31d071cbyh34bf-source/lib/attrsets.nix:484:14:

          483|     value:
          484|     { inherit name value; };
             |              ^
          485|

       error: attribute 'wrapper' missing

       at /nix/store/gzq17ccnn7sbfl08c26hhy9c3vmxfbhv-source/flake.nix:23:9:

           22|       formatter = eachSystem (system:
           23|         self.checks.${system}.wrapper
             |         ^
           24|       );

To Reproduce

Steps to reproduce the behavior: nix flake show github:numtide/treefmt-nix/27107cf3dfdc3c809d2477954d92fc2cc68b4401

Expected behavior

no error

System information

nixos-unstable

Additional context

[zimbatm]

thanks!