'this' type in augment function is any

[todoubaba]

TypeScript Version:

1.8.7

Code

/* foo.ts*/
export class Foo {
    name: string;
}

/*bar.ts*/
import {Foo} from './foo'
declare module './foo' {
    interface Foo {
        bar(): string;
    }
}

Foo.prototype.bar = function() {
    return this.name; // this's type is any
}

Expected behavior:
The type of this in augment function bar is any.
Actual behavior:
The type of this is Foo.

[mhegazy]

this is currently by design. this is of type any outside the body of a class. issue #6018 tracks adding the ability to declare it.