Moving to TS 2.0 causes grief due to d.ts file incompatibility #10412

TypeScript Version: 1.8.x and 2.0
Code

export class A {
    get value(): number {
        return 10;
    }
}

A d.ts file for this ts file looks with 2.0 like this:

export declare class A {
    readonly value: number;
}

This d.ts file can't be consumed by clients still using 1.8.10 compiler. To ease transition to 2.0 the compiler should allow to generate 1.8 compliant d.ts file if possible, which is not possible for example with using undefined as a type.