docs: function parseExportSpecifier() {
          var exported, local, node = new Node(), def;
          if (matchKeyword('default')) {
              // export {default} from 'something';
              def = new Node();
              lex();
              local = def.finishIdentifier('default');
          } else {
              local = parseVariableIdentifier();
          }
          if (matchContextualKeyword('as')) {
              lex();
              exported = parseNonComputedProperty();
          }
          return node.finishExportSpecifier(local, exported);
      }