Typescript 使用原始类型的键索引映射类型

我正在开发一个解析CSV并返回类型化对象数组的函数.它看起来像这样.

type KeyToTransformerLookup<T> = {
  [K in keyof T as T[K] extends string ? never : K]: (
    stringValue: string
  ) => T[K];
};

export default function csvToArray<T>(
  csv: string,
  keys: Array<keyof T>,
  keyToTransformerLookup: KeyToTransformerLookup<T>,
  ignoreFirstLine = false
): T[] {
  const rows = csv.split(/\n(?=.)/);

  if (ignoreFirstLine) {
    rows.shift();
  }

  return rows.map((row) => {
    const values = row.split(/(?!\B"[^"]*),(?![^"]*"\B)/g);

    const rowObject: Record<any, any> = {};

    keys.forEach((key, index) => {
      const stringValue = values[index];

      if (key in keyToTransformerLookup) {
        rowObject[key] = keyToTransformerLookup[key](stringValue); // TypeScript complains
        return;
      }

      rowObject[key] = stringValue;
    });

    return rowObject as T;
  });
}

Type 'keyof T' cannot be used to index type 'KeyToTransformerLookup<T>'.

我猜这是因为一旦映射了K in keyof T，结果类型就不再是keyof T的部分，而是一个全新的类型.这有点令人沮丧，因为我没有转换键，而且我还在判断keyToTransformerLookup上是否存在key，所以我只想找到一种满足TypeScrip的方式来索引keyToTransformerLookup.