TypeScript版本： 3.2.0-dev.20181103
代码

import React = require("react");
declare function F(): C;
class C extends React.Component<{ title?: string }> {}
<F title="My Title" />

预期行为：

没有错误，就像ts3.1一样。

实际行为：

src/a.tsx:4:2 - error TS2322: Type '{ title: string; }' is not assignable to type 'IntrinsicAttributes'.
  Property 'title' does not exist on type 'IntrinsicAttributes'.

4 <F title="My Title" />
   ~

Found 1 error.

在DefinitelyTyped上发现了react-helmet/v4和react-flag-icon-css。react-flag-icon-css的变化更像这样：

import React = require("react");
declare class C extends React.PureComponent<{}> {}
declare const F: (props: {}) => C;
<C />; // OK
<F />; // Error