this derivation will be built:
  /nix/store/w4nxn4w8qagx3y2ll18zv6d0ay7a6yww-treefmt-check.drv
error: Cannot build '/nix/store/w4nxn4w8qagx3y2ll18zv6d0ay7a6yww-treefmt-check.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/6lv1wkbs86h354kaqsbynkbcxlc68rjp-treefmt-check
       Last 19 log lines:
       > tribuchet: hub connection lost (hub closed event stream without a result); reconnecting
       > tribuchet: building on jamie
       > treefmt v2.5.0ERRO formatter | nixfmt: failed to apply with options '[]': exit status 1
       >
       > Error[E001]: expected ';', found '.'
       >    ┌─ docs/demo/flake.nix:7:22
       >    │
       >  6 │     let
       >  7 │       pkgs = nixpkgs.legacyPackages.@system@;
       >    │                      ^^^^^^^^^^^^^^
       >  8 │       mk = name: script: pkgs.runCommand name { nonce = "@nonce@"; } script;
       >    = note: missing semicolon after definition
       >    = help: add a semicolon at the end of the previous line
       >
       >
       > traversed 52 files
       > emitted 39 files for processing
       > formatted 33 files (0 changed) in 201ms
       > Error: failed to finalise formatting: formatting failures detected
       For full logs, run:
         nix log /nix/store/w4nxn4w8qagx3y2ll18zv6d0ay7a6yww-treefmt-check.drv