code: private DynamicImportTree parseDynamicImportExpression() {
      SourcePosition start = getTreeStartLocation();
      eat(TokenType.IMPORT);
      eat(TokenType.OPEN_PAREN);
      ParseTree argument = parseAssignmentExpression();
      eat(TokenType.CLOSE_PAREN);
      recordFeatureUsed(Feature.DYNAMIC_IMPORT);
      return new DynamicImportTree(getTreeLocation(start), argument);
    }
docs: https://tc39.github.io/proposal-dynamic-import