ES6 class decoration output means property, method & parameter decorations can not get type information from target

[jamcoupe]

function Decoration() {}
function PropertyDecoration(target: any) {
  console.log(target);
}

@Decoration
export class ClassName {

  @PropertyDecoration
  property: string = 'null';
}

compiles to:

function Decoration() { }
function PropertyDecoration(target) {
    console.log(target);
}
let ClassName = class {
    constructor() {
        this.property = 'null';
    }
};

However this means that the console.log result will be {}. Removing the @Decoration class decorator outputs:

function PropertyDecoration(target) {
    console.log(target);
}
class ClassName {
    constructor() {
        this.property = 'null';
    }
}

with the better console.log result of ClassName {}.

[mhegazy]

looks like a duplicate of #6132