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Generic constraints are sometimes lost #18552

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@kujon

Description

@kujon

TypeScript Version: 2.4.2

Code

type A = {
    foo: number;
    bar: string;
};

class Component<T> {
    props: T;
    constructor(props: T) {
        this.props = props;
    }
    render(): Component<T> | null {
        return null;
    };
}

const exampleHOC = <T extends A>(
    WrappedComponent: Component<T>
) => {
    return class ExampleHOC extends Component<T> {
        render() {
            /** Rest types may only be created from object types.  */
            const { foo, ...rest } = this.props;

            return new Component(this.props);
        }
    }
};

Expected behavior:
The code above compiles.

Actual behavior:
Rest types may only be created from object types. error message is shown, which leads me to believe that at the time of destructuring the props, T doesn't have any constraints applied to it.

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