Emit type annotations as written when generating .d.ts files

[ahejlsberg]

If a type annotation is present it should be emitted exactly as written when generating a .d.ts file. For example:

module M {
    export type Value = string | number | boolean;
    export var x: Value;
}

The .d.ts file for the above is currently emitted as:

module M {
    export type Value = string | number | boolean;
    export var x: string | number | boolean;
}

The type annotation on x should be preserved and emitted exactly as written. Specifically, the declaration file emitter should only emit from Type objects when dealing with inferred types.

The current scheme of always emitting from Type objects actually leads to errors.

module M {
    type W = Window | string;
    export module N {
        export class Window { }
        export var p: W;
    }
}

Here, an error occurs when the emitter tries to emit Window | string in place of the W type annotation.

[DickvdBrink]

This is fixed in master right, at least according to my manual testing.
So I think this one can be closed?
edit not sure if there is a test though

[danquirk]

It does look like we need some tests for this, I don't see any .d.ts related tests in #1033. Need to double check whether these rules are codified in the latest spec yet.

[sheetalkamat]

@DickvdBrink @danquirk , this is not completely fixed. We want to change this to emit type annotation as user wrote and I am working on that. I have the change but I am still adding tests to cover different scenarios. This should be in by mid week.

[sheetalkamat]

#1122 handles this