tslib __decorate was conflict with property decorator definition

such a code with property decorator usage:

class Controller {

	name = 'xx';

	@inject(Store)
	store: any = null;
}

after a tsc compiling:

var Controller = /** @class */ (function () {
        function Controller() {
            this.name = 'xx';
            this.store = null;
        }
        tslib_1.__decorate([
            inject_1.default(Store)
        ], Controller.prototype, "store", void 0);
        return Controller;
    }());

and here is the tslib __decorate implementation:
https://github.com/Microsoft/tslib/blob/b1ed5e1b940756d18609833caf9b781e9bc3984f/tslib.js#L85-L90
we can realize that if the property decorator return a descriptor, __decorate function will define property for us, from the code above.

but in typescript lib.es.d.ts definition, property decorator should not return anything:
https://github.com/Microsoft/TypeScript/blob/master/lib/lib.es6.d.ts#L1285

declare type PropertyDecorator = (target: Object, propertyKey: string | symbol) => void;

so which one is the truth?

Compare the __decorate implementation in tslib.js at the linked lines with the PropertyDecorator definition in TypeScript's lib/lib.es6.d.ts and the generated example in the issue. Determine whether the runtime behavior and type definition should agree, then document the expected behavior or identify the necessary change and its validation.