Typescript: Ambient class can merge with concrete function

[DanielRosenwasser]

declare class C {

}

function C() {

}

[weswigham]

Intentional and tested.

[weswigham]

(This is analogous to how a concrete class can merge with an interface that adds more behavior that isn't implemented)

[weswigham]

Feel free to add to the release notes if you'd like~

[weswigham]

Yes, this means you can actually declare callable constructors in proper _TS_ implementation code now.

export declare class Point2D {
    x: number;
    y: number;
    constructor(x: number, y: number);
}
export function Point2D(this: Point2D | undefined, x: number, y: number) {
    if (!(this instanceof Point2D)) {
        return new Point2D(x, y);
    }
    this.x = x;
    this.y = y;
}

That's why it closed out ole issue #183.

[DanielRosenwasser]

Seems reasonable.

[typescript-bot]

This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.

[Jack-Works]

https://github.com/microsoft/TypeScript/issues/32897#issuecomment-521511765

@wemeetagain your example code is no longer working in the TypeScript 3.9, is it a regression?

Cannot redeclare exported variable 'Point2D'.(2323)

https://www.typescriptlang.org/play/index.html?ssl=1&ssc=1&pln=5&pc=1#code/KYDwDg9gTgLgBAE2AYwDYEMrDm9BnPOABQgEsA7GAJgBE4BvAWACg424QAuOcgVwFsARsCgBuFuzgBPbnyEjxrdsgjk8MKL2QxoACi48BwqABppsoyICUigL4tQkWHABmvcttKriZSrV0wABakeNwkFNR0AD5w7kguFMAIZgZyxmYyhvJQVgwS7KQucLoAhAHBhBTq6B7AEEXhfjRWuUxKkmxYMLxQ5DzAAO4+Ef4gGTb5bPbtcEEhAHQgcAC8HIqSc3jzUivSdixAA