Typescript defaultProps不检查类型

Question

I'm using TypeScript 3.0 and according to the documentation from https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-0.html

Use static defaultProps: Pick<Props, "name">; as an explicit type annotation instead, or do not add a type annotation as done in the example above.

However if I write:

import React, { Component } from 'react';

interface Props {
  counter: number;
}

export default class NumberCounter extends Component<Props> {
  static defaultProps = {
    counter: "i am not a number"
  };

  render() {

    return (
      <div>{this.props.counter}</div>
    );
  }
}

It compiles and works, apparently the prop's default value isn't typechecked. Nonetheless, when I try to use the component erroneously:

<NumberCounter 
  counter="still not a number"
/>

It shows an error, and typechecks correctly when it is used elsewhere. Is this a known bug with TypeScript?

Answer 1

You should have a type assigned to defaultProps not only the component itself:

static defaultProps: Props = {
    counter: "i am not a number"
};