overrideAttrs question

test.nix

[
  {
    # builds
    bcrypt = super.bcrypt.overrideAttrs (old: {
      cargoDeps = pkgs.rustPlatform.fetchCargoTarball {
        name = "${old.pname}-${old.version}";
        src = old.src;
        sourceRoot = "${old.pname}-${old.version}/src/_bcrypt";
        sha256 = "19j1hcwr6c7r3p9b3af5dfa9m5jimxk0cwmspd692d84svmrfdcl";
      };
    });
  }
  {
    # fails
    bcrypt = super.bcrypt.overrideAttrs (old: {
      cargoDeps = old.cargoDeps.overrideAttrs (_: {
        sha256 = "19j1hcwr6c7r3p9b3af5dfa9m5jimxk0cwmspd692d84svmrfdcl";
      });
    });
  }
]

probably need this:

    bcrypt = super.bcrypt.overrideAttrs (old: {
      cargoDeps = old.cargoDeps.overrideAttrs (oldAttrs: oldAttrs // {
        sha256 = "19j1hcwr6c7r3p9b3af5dfa9m5jimxk0cwmspd692d84svmrfdcl";
      });
    });