these 3 derivations will be built:
  /nix/store/p51hvszzcgnbs67nfb03c7ckabym5wm1-treefmt.toml.drv
  /nix/store/galasp0m51vp5rncxvj9fwsqpf8vrz67-treefmt.drv
  /nix/store/si5dmxjgn3i1fmkc0z80civyj31i9gqa-treefmt-check.drv
this path will be fetched (774.7 KiB download, 1.8 MiB unpacked):
  /nix/store/0pcwwnii74w0cvjgpf8lbsrc19c2wmkh-alejandra-4.0.0
building '/nix/store/p51hvszzcgnbs67nfb03c7ckabym5wm1-treefmt.toml.drv'
treefmt.toml> tribuchet: building on jamie
treefmt.toml> structuredAttrs is enabled
building '/nix/store/galasp0m51vp5rncxvj9fwsqpf8vrz67-treefmt.drv'
treefmt> tribuchet: building on jamie
building '/nix/store/si5dmxjgn3i1fmkc0z80civyj31i9gqa-treefmt-check.drv'
treefmt-check> tribuchet: building on jamie
treefmt-check> treefmt v2.6.0traversed 28 files
treefmt-check> emitted 17 files for processing
treefmt-check> formatted 17 files (2 changed) in 61ms
treefmt-check>  M tests/hello-flake-v1/flake.nix
treefmt-check>  M tests/hello-flake-v2/flake.nix
treefmt-check> diff --git a/tests/hello-flake-v1/flake.nix b/tests/hello-flake-v1/flake.nix
treefmt-check> index d58aa8a..f3d5f28 100644
treefmt-check> --- a/tests/hello-flake-v1/flake.nix
treefmt-check> +++ b/tests/hello-flake-v1/flake.nix
treefmt-check> @@ -1,12 +1,10 @@
treefmt-check>  {
treefmt-check>    description = "Hello flake v1";
treefmt-check>  
treefmt-check> -  outputs =
treefmt-check> -    { self }:
treefmt-check> -    {
treefmt-check> -      packages.x86_64-linux.default = import ./default.nix;
treefmt-check> -      packages.aarch64-linux.default = import ./default.nix;
treefmt-check> -      packages.x86_64-darwin.default = import ./default.nix;
treefmt-check> -      packages.aarch64-darwin.default = import ./default.nix;
treefmt-check> -    };
treefmt-check> +  outputs = { self }: {
treefmt-check> +    packages.x86_64-linux.default = import ./default.nix;
treefmt-check> +    packages.aarch64-linux.default = import ./default.nix;
treefmt-check> +    packages.x86_64-darwin.default = import ./default.nix;
treefmt-check> +    packages.aarch64-darwin.default = import ./default.nix;
treefmt-check> +  };
treefmt-check>  }
treefmt-check> diff --git a/tests/hello-flake-v2/flake.nix b/tests/hello-flake-v2/flake.nix
treefmt-check> index 8b5f577..b4181ee 100644
treefmt-check> --- a/tests/hello-flake-v2/flake.nix
treefmt-check> +++ b/tests/hello-flake-v2/flake.nix
treefmt-check> @@ -1,12 +1,10 @@
treefmt-check>  {
treefmt-check>    description = "Hello flake v2";
treefmt-check>  
treefmt-check> -  outputs =
treefmt-check> -    { self }:
treefmt-check> -    {
treefmt-check> -      packages.x86_64-linux.default = import ./default.nix;
treefmt-check> -      packages.aarch64-linux.default = import ./default.nix;
treefmt-check> -      packages.x86_64-darwin.default = import ./default.nix;
treefmt-check> -      packages.aarch64-darwin.default = import ./default.nix;
treefmt-check> -    };
treefmt-check> +  outputs = { self }: {
treefmt-check> +    packages.x86_64-linux.default = import ./default.nix;
treefmt-check> +    packages.aarch64-linux.default = import ./default.nix;
treefmt-check> +    packages.x86_64-darwin.default = import ./default.nix;
treefmt-check> +    packages.aarch64-darwin.default = import ./default.nix;
treefmt-check> +  };
treefmt-check>  }
error: Cannot build '/nix/store/si5dmxjgn3i1fmkc0z80civyj31i9gqa-treefmt-check.drv'.
       Reason: builder failed with exit code 1.
       Output paths:
         /nix/store/806q6qbnw113a1hm60y9yh9lvi5vqhpc-treefmt-check
       Last 25 log lines:
       > +  };
       >  }
       > diff --git a/tests/hello-flake-v2/flake.nix b/tests/hello-flake-v2/flake.nix
       > index 8b5f577..b4181ee 100644
       > --- a/tests/hello-flake-v2/flake.nix
       > +++ b/tests/hello-flake-v2/flake.nix
       > @@ -1,12 +1,10 @@
       >  {
       >    description = "Hello flake v2";
       >
       > -  outputs =
       > -    { self }:
       > -    {
       > -      packages.x86_64-linux.default = import ./default.nix;
       > -      packages.aarch64-linux.default = import ./default.nix;
       > -      packages.x86_64-darwin.default = import ./default.nix;
       > -      packages.aarch64-darwin.default = import ./default.nix;
       > -    };
       > +  outputs = { self }: {
       > +    packages.x86_64-linux.default = import ./default.nix;
       > +    packages.aarch64-linux.default = import ./default.nix;
       > +    packages.x86_64-darwin.default = import ./default.nix;
       > +    packages.aarch64-darwin.default = import ./default.nix;
       > +  };
       >  }
       For full logs, run:
         nix log /nix/store/si5dmxjgn3i1fmkc0z80civyj31i9gqa-treefmt-check.drv