Question

我从Flow得到一个我不明白的错误。

Cannot call document.createTreeWalker because:
 • Either number literal 4 [1] is incompatible with number literal 1 [2].
 • Or number literal 4 [1] is incompatible with number literal 5 [3].
 • Or number literal 4 [1] is incompatible with number literal 128 [4].
 • Or number literal 4 [1] is incompatible with number literal 129 [5].
 • Or number literal 4 [1] is incompatible with number literal 132 [6].
 • Or number literal 4 [1] is incompatible with number literal 133 [7].

     hello.js
        2│
        3│ const body = document.body;
        4│ if (body) {
        5│   document.createTreeWalker(body, NodeFilter.SHOW_TEXT, null, false);
        6│ }
        7│

     /tmp/flow/flowlib_18704f10/dom.js
 [2] 1050│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 1, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Element>;
     1051│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 4, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Text>;
 [3] 1052│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 5, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Element|Text>;
 [4] 1053│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 128, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Comment>;
 [5] 1054│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 129, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Element|Comment>;
 [6] 1055│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 132, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Text|Comment>;
 [7] 1056│   createTreeWalker<RootNodeT: Node>(root: RootNodeT, whatToShow: 133, filter?: NodeFilterInterface, entityReferenceExpansion?: boolean): TreeWalker<RootNodeT, Text|Element|Comment>;
         :
 [1] 3508│   static SHOW_TEXT: 4;

在我看来，应该允许SHOW_TEXT（即4），因为第1051行将4列为第二个参数的有效值。我错过了什么？

要重现这一点，您可以运行：

git clone https://github.com/MatrixFrog/flow-example
cd flow-example
git checkout 0f6035a8bb05cc8f0f01418d4617973991baa231
flow version # 0.73.0
flow check

Answer 1

错误是如此无益的事实似乎是Flow的一个问题，但你的错误是那个

filter?: NodeFilterInterface

接受过滤器，或undefined，null不是有效值，所以

document.createTreeWalker(body, NodeFilter.SHOW_TEXT, undefined, false);

会正确通过typechecker。

这个Flow错误是什么意思？

1 个答案: