Cant satisfy complier on calls x implements y, where y is class.

[shlomiassaf]

Hi,

Typescript 1.6.2
When trying to implement a class with private variables complier wants the derived class to implement the parent's private variables.

export class Father {
    private hidden: string;
    public visible: string;
}

export  class Child implements Father{
    public visible: string;
}

(7,15): error TS2420: Class 'child' incorrectly implements interface 'father'.
Property 'hidden' is missing in type 'child'.

Trying to do the wrong thing and do implement the private variable results in the compiler not happy since we implement a private variable of the parent (In a typed language this is wrong as well, but in JS it might be a good catch...)

export class Father {
    private hidden: string;
    public visible: string;
}

export  class Child implements Father{
    private hidden: string;
    public visible: string;

}

(7,15): error TS2420: Class 'child' incorrectly implements interface 'father'.
Types have separate declarations of a private property 'hidden'.

[sandersn]

Can you try extends instead of implements ? implements is for interfaces.

[shlomiassaf]

I can try and it will probably work, but i'm trying to do some "mixin" stuff

Typescript has an official documented approach for it, https://github.com/Microsoft/TypeScript-Handbook/blob/master/pages/Mixins.md

I'm sure I've seen some other places in the docs that "implement" concrete classes...
So it should be possible

[mhegazy]

the issue here is the private property declaration. When implementing a class with private, the implementing class gets the property declaration but not its implementation. private members can not be re-implemented, the only allowed implementation for them is their original declaration. so now you have a class is not implementable.
for mix-in patterns, do not use private members, or split your non-private declarations in an interface and use that.

[mhegazy]

see #1101 for more details.