复杂的泛型类型约束和类型推断

Question

我正在尝试在TypeScript中构建一个微型ORM，但我面临以下编译问题：

Type 'TObject' does not satisfy the constraint '{ [k in k]: object; }'.
Type 'object' is not assignable to type '{ [k in k]: object; }'.

有谁知道为什么这个代码示例会引发编译错误？ 以及如何解决它？

type NavigationProperties<T, TKey extends keyof T> = T[TKey] extends object ? TKey : never;
type Relationship<T extends { [k in TMember]: TTarget }, TMember extends keyof T, TTarget extends object = object> = {
name: TMember,
isComposite?: boolean,
};
class A<TObject extends object>
{
public readonly relationships: Partial<{ [k in NavigationProperties<TObject, keyof TObject>]: Relationship<TObject, k> }> = { }
}

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编辑

根据 Shivam 的要求，我正在为其添加更多上下文：当我有混合类型或不匹配类型时，我还想让它工作： 操场

Answer 1

问题

在类型Relationship中，T被约束于{ [k in TMember]: TTarget }，同时声明属性relationships，TObject传递的类型为object的超类型{ [k in TMember]: TTarget }。因此不相容。

溶液

type NavigationProperties<T, TKey extends keyof T> = T[TKey] extends object ? TKey : never;
type TObject<T extends object, TType extends object> = { [K in keyof T]: TType }
type Relationship<T extends TObject<T, TType>, TKeys extends keyof T, TType extends object> = {
name: TKeys,
isComposite?: boolean,
};
type Relationships<T extends TObject<T, TType>, TType extends object> = {
[K in NavigationProperties<T, keyof T>]?: Relationship<T, K, TType>
}
class A<T extends TObject<T, TType>, TType extends object = object> {
public readonly relationships: Relationships<T, TType> = { }
}
// example usage
type MyType = {
prop1: number
porp2: string
}
type X = {
a: MyType
b: MyType
}
declare const obj: A<X>
obj.relationships // type is Relationships<X, object>
// type of obj1.relationships.a is Relationship<X, "a", object>
obj.relationships.a?.name // "a"
obj.relationships.b?.name // "b"
declare const obj1: A<X, MyType>
obj1.relationships // type is Relationships<X, MyType>
// type of obj1.relationships.a is Relationship<X, "a", MyType>
obj1.relationships.a?.name // "a"
obj1.relationships.b?.name // "b"

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