Typescript: Set is not an array type

With Babel, I can use spread syntax on a Set. For example, the following neat trick returns the unique elements in an array:

const a = [ 0, 1, 2, 3, 2, 1, 0];
console.log([...new Set(a)]);

// outputs [0, 1, 2, 3]

However in Typescript, I get the following error: Set is not an array type. I presume this is a problem with the lib.d.ts typings?

BTW, I also tried this on http://www.typescriptlang.org/Playground, but there I got the error: "Cannot find the name 'Set'".
Is the Playground not up to date with the latest tsc version?