Allow assignment of properties from one object to another using destructuring / structuring.

let a = { x:1, y:2 };
let b = { z:3 };
b.{ x, y } = a;
//b is now { z:3, x:1, y:2 }

Currently, .{ is a syntax error, so this syntax is unambiguous.
And its meaning is so intuitive, that this post does not even have any more explaining to do. :-|