anchor.diff:      psqlSchema = "13";
       sha256 = "07z6zwr58dckaa97yl9ml240z83d1lhgaxw9aq49i8lsp21mqd0j";
       this = self.postgresql_13;
  +    thisAttr = "postgresql_13";
       inherit self;
     };
   }
  
positive.code:       , this, self, newScope, buildEnv
  
        # source specification
        , version, sha256, psqlSchema
      }:
    let
      atLeast = lib.versionAtLeast version;
  
negative.code:                        postgresql = this;
                       }
                       this.pkgs;
  
        tests.postgresql = nixosTests.postgresql-wal-receiver.${thisAttr};
      };
  
      meta = with lib; {
  