[英]Iterate Over TypeScript Type-level Linked List without Excessive Depth Error
** This is a question relating to TypeScript ^4.1 ** ** 这是一个关于 TypeScript ^4.1 的问题 **
I have a recursive linked-list type.我有一个递归链表类型。
interface ListNode {
value: string;
next: ListNode | undefined;
}
Here's an example of a type-level instance.这是一个类型级实例的示例。
type RootNode = {
value: "a";
next: {
value: "b";
next: {
value: "c";
next: undefined;
};
};
};
I'd like to flatten this narrow linked list type into the following type.我想将这种窄链表类型展平为以下类型。
type Flattened = [
{value: "a"},
{value: "b"},
{value: "c"},
]
I keep running into TS error 2589 (excessive depth / possibly infinite).我一直遇到 TS 错误 2589(深度过大/可能无限)。
Here are the two approaches I've taken so far.这是我迄今为止采取的两种方法。
type Flatten<T extends ListNode> = [
Omit<T, "next">,
...(T["next"] extends ListNode
? Flatten<T["next"]>
: [])
]
type Flatten<
T extends ListNode,
I extends undefined[] = []
> =
T["next"] extends ListNode
? Record<I["length"], Omit<T, "next">> & Flatten<T["next"], [...I, undefined]>
: Record<I["length"], Omit<T, "next">>;
I even tried hardcoding the incrementation.我什至尝试硬编码增量。
type Increment = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20];
type Flatten<
T extends ListNode,
I extends number = 0
> =
T["next"] extends ListNode
? Record<I, Omit<T, "next">> & Flatten<T["next"], Increment[I]>
: Record<I, Omit<T, "next">>;
Still, I get error 2589.尽管如此,我还是收到了错误 2589。
If anyone has devised a workaround, I'd be extremely grateful to hear what it is.如果有人设计了一种解决方法,我将非常感激听到它是什么。
Thank you.谢谢你。
Turns out this error only occurs when the input linked-list type is derived from other recursive types.原来只有当输入链表类型是从其他递归类型派生时才会发生此错误。 The above flatten methods work as expected.
上述展平方法按预期工作。
interface ListNode {
value: string;
next: ListNode | undefined;
}
type RootNode = {
value: "a";
next: {
value: "b";
next: {
value: "c";
next: undefined;
};
};
};
type Flatten<T extends ListNode> = [
Omit<T, "next">,
...(T["next"] extends ListNode
? Flatten<T["next"]>
: [])
]
type Result = Flatten<RootNode>; // [{value: "a"}, {value: "b"}, {value: "c"}]
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