使用 rest 语法解构道具时，Typescript 无法推断道具

Question

I have a custom generic type that uses React's ComponentProps internally.
When I create the type of a component's props using this custom type, TS behaves strangely.
Here is a simple example:
Codesandbox Link

You can see in the link above that when I use PropsWithAs generic type, TS only understands that fallbackText is in the props if I access it directly. But it fails to get the fact that fallbackText is in in the rest variable when I use rest syntax.

type Props<T extends ElementType = "div"> = PropsWithAs<
  T,
  {
    fallbackText: string;
    counter: number;
  }
>;

const Foo = <T extends ElementType>(props: Props<T>): JSX.Element => {
  // fallbackText is present and identified by TS here without any issue:
  const { fallbackText } = props;
  
  const { counter, ...rest } = props;

  // But TS doesn't see that `rest` also includes fallbackText here:
  return <Bar {...rest} />;
};

Answer 1

The problem seems to be the definition of PropsWithAs. I don't really understand why you are using & Omit<ComponentProps<T>, keyof U> , it seems to be the contrary of what you want.

Anyways, if you remove that piece of code everything should work just fine.

Answer 2

I believe I found the problem

Omit<ComponentProps<T>, keyof U>

this is because omit remove from the type the keys you want ts document about omit It means that you remove from the T the U keys it doesn't mean you gonna have those keys in the rest if they do not exist in the T