code: Type attribArg(JCTree tree, Env<AttrContext> env) {
          Env<AttrContext> prevEnv = this.env;
          try {
              this.env = env;
              tree.accept(this);
              return result;
          } finally {
              this.env = prevEnv;
          }
      }
docs: Main entry point for attributing an argument with given tree and attribution environment.