Add base class in lib.scripthost.d.ts for Automation objects

TypeScript Version: 2.5.0 / nightly (2.6.0-dev.20170902)

Code

// in lib.scripthost.d.ts
class AutomationObject<T> {
  private constructor();
  private typekey: AutomationObject<T>;
}

// in activex-excel.d.ts
declare namespace Excel {
    class Application extends AutomationObject<Application> {
        Workbooks: any;
    }
}

interface ActiveXObject {
    new(progid: 'Excel.Application'): Excel.Application;
}
    
// usage
let x: Excel.Application = new ActiveXObject('Excel.Application');

This currently wouldn't compile, because of the private constructor in the base class; but pending resolution of #18283, it would be possible.

This would prevent assigning structurally matching objects to the inheriting types:

// Compiler error
x = {
    Workbooks: [];
};

and also prevent using new to create a new instance of the inheriting type:

// Compiler error
x = new Excel.Application();

I've opened an issue to define similar behavior for VarDate and SafeArray<T> in lib.scripthost.d.ts. If AutomationObject<T> is defined, then it could be used in lib.scripthost.d.ts as a base class for these types as well:

declare class VarDate extends AutomationObject<VarDate> { }
declare class SafeArray<T> extends AutomationObject<SafeArray<T>> { }

lib.scripthost.d.ts から始め、提案されている AutomationObject の宣言と、VarDate および SafeArray の基底としての使用を確認します。まず issue #18283 と #17526 の解決内容を確認してください。完了とは、宣言によって説明されている構造上および構築上の制約が適用され、scripthost の定義を壊さないことを意味します。