我在 TypeScript 中遇到循环默认问题，我不知道如何解决

Question

我想通过以下方式定义类型：

export type SequenceNode<
  T extends ComponentSequenceNode = ComponentSequenceNode,
  U extends ContainerSequenceNode = ContainerSequenceNode
> = T | U;

export interface ComponentSequenceNode<T extends SequenceNode = SequenceNode> {
  id: string;
  node: "sequence";
  sequence: "component";
  next: T[];
}

export interface ContainerSequenceNode<T extends SequenceNode = SequenceNode> {
  id: string;
  node: "sequence";
  sequence: "container";
  next: T[];
  into: T[];
}

但是，我收到一条消息，说我对这些类型有循环默认设置。

我想使用泛型并使用此结构来定义类型，但我不知道如何实现它。

Answer 1

问题是，这个类型参数定义是递归的，

SequenceNode

的默认类型可能是这样的

SequenceNode<SequenceNode<SequenceNode<..., ...>, SequenceNode<..., ...>>, SequenceNode<SequenceNode<..., ...>, SequenceNode<..., ...>>>

编译器将尝试评估那个永无止境的链。

因此，默认情况下，使用

SequenceNode<any, any>

，以便链条“停止”在那里：

export type SequenceNode<
  T extends ComponentSequenceNode = ComponentSequenceNode,
  U extends ContainerSequenceNode = ContainerSequenceNode
> = T | U;

export interface ComponentSequenceNode<T extends SequenceNode = SequenceNode<any, any>> {
  id: string;
  node: "sequence";
  sequence: "component";
  next: T[];
}

export interface ContainerSequenceNode<T extends SequenceNode = SequenceNode<any, any>> {
  id: string;
  node: "sequence";
  sequence: "container";
  next: T[];
  into: T[];
}

您的代码仍然工作相同，任何

SequenceNode<Something, SomethingElse>

都满足

T extends SequenceNode

类型，但默认情况下它的类型更具体。

这是 TS-Playground 链接：https://tsplay.dev/wXL3Jw