为什么VSCODE打字稿自动完成在简单 /复杂的联盟上如此奇怪

Question

基本上，我有一个带有2个属性的打字稿类型，我希望Vscode能够在完成第一个属性后能够自动完成 / IntelliSense。

真正奇怪的是，Vscode可以做到这一点，但是前提是工会足够复杂……但是如果它非常简单。

我认为最简单的解释方法是使用几个代码示例。

这可以按照您期望的方式工作：

type MyGenericType<a, b> = {
  property1: a;
  property2: b;
};
type MyUnion =
MyGenericType<"a", "a">
| MyGenericType<"b", "b">
| MyGenericType<"c", "c">
| MyGenericType<"d", "d">
| MyGenericType<"e", "e">
| MyGenericType<"f", "f">
| MyGenericType<"g", "g">
| MyGenericType<"h", "h">
| MyGenericType<"i", "i">
| MyGenericType<"j", "j">;

const myConstant: MyUnion = {
  property1: "a",
  property2: "", // VSCode can suggest correctly the only possible string here is "a"
};

但是，如果我们从联合中删除项目不起作用：

type MyGenericType<a, b> = {
  property1: a;
  property2: b;
};
type MyUnion =
MyGenericType<"a", "a">
| MyGenericType<"b", "b">
| MyGenericType<"c", "c">
| MyGenericType<"d", "d">
| MyGenericType<"e", "e">
| MyGenericType<"f", "f">
| MyGenericType<"g", "g">
| MyGenericType<"h", "h">
| MyGenericType<"i", "i">;

const myConstant: MyUnion = {
  property1: "a",
  property2: "", // VSCode suggests property2 might be any letter from "a" to "i" (of course, it can only be "a")
};

要清楚，打字稿（和vscode）正确识别何时错误地构造了我的constant。问题是自动完成 / intelisense。

如果有人知道这里发生了什么，或者是一个已知的错误...或实际上。那真是太神奇了。

谢谢。