TypeScript:推断记录联合值

Question

interface Num {
    type: 'number',
    default: number
}

interface Bool {
    type: 'boolean'
    default: boolean
}

interface Str {
    type: 'string',
    default: string
}

type UnionType = Num | Bool | Str

interface IOption<T extends string, CFG extends Record<T, UnionType>> {
    configs: CFG,
    // I don't know how to write this line to make each key matches its own value type
    // i.e. `{key1: Num, key2: Bool, key3: Str}`
    defaultOverwrite?: Partial<{ [key in T]: CFG[key]['default'] }>
}

declare function checker<T extends string, CFG extends Record<T, UnionType>>(option: IOption<T, CFG>): void

checker({
    configs: {
        // key1 errors as expected, which default should be a number
        key1: { type: 'number', default: '' },
        key2: { type: 'boolean', default: true },
        key3: { type: 'string', default: 'string' },
    },
    defaultOverwrite: {
        // the value of `key1` should match the type of configs.key1.default, which is a number.
        // expected error here, but I don't know how
        key1: '3'
    }
})

见上例。

我想检查 configs 类型，哪个值应该匹配 UnionType，另外，我想检查 defaultOverwrite 类型，它应该有 configs 的部分键和 configs 声明的相应值类型。

但是我不知道怎么办，谁能帮帮我？

我重新考虑了我的问题，真正的问题是我们需要让联合值记录在赋值时成为精确类型，比如

type A = {[key: string]: string | number}
// when declared
const a: A = {
  key1: 1,
  key2: 'str'
}

我希望 a 匹配类型 A 但也生成一个确切的类型，即

interface ExactA{
  key1: number,
  key2: string
}

Playground

Answer 1

你不能指望在一个泛型中出现不止一个错误

defaultOverwrite 中的错误将在您修复 configs 中的错误后立即出现

checker({
    configs: {
        key1: { type: 'number', default: 1 }, // error fixed
        key2: { type: 'boolean', default: true },
        key3: { type: 'string', default: 'string' },
    },
    defaultOverwrite: {
        key1: '1' // a new error has spawned
            // (property) key1?: number | undefined
            //Type 'string' is not assignable to type 'number'.(2322)
    }
})

Playground