Improve feedback for abstract class instantiation error messages

SUGGESTION

Recently, I was trying to use a library written in ES2015 in an Ionic 2 project, and kept getting a Cannot instantiate abstract class 'Foo'. Foo is a concrete class that extends abstract class Bar, which extends abstract class Baz. The problem turned out to be a typo in Bar.d.ts (see below), which (I believe) made Typescript think that Foo did not implement some abstract methods of Bar and/or Baz (I'm still not sure which), but it took me a day and half to figure out what was going on. This error message should have more information about why Foo is abstract: Foo is declared as abstract or Foo does not implement abstract methods ...

TypeScript Version: 2.0.9

Code

Baz.d.ts

export as namespace Baz;

declare abstract class Baz {
  abstract baz(): string;
}

Bar.d.ts

export as namespace BarTypo;

declare abstract class Bar extends Baz {
  abstract foo(): void;
  abstract bar(): string;
  baz(): string;
}

export { Bar };

Foo.d.ts

import { Bar } from './bar.d';

export as namespace Foo;

declare class Foo extends Bar {
  constructor(opts?);

  foo(): void;
  bar(a: string): string;
}

export { Foo };

otherProject.ts

import { Foo } from 'library';

export class Service {
  foo: Foo;

  constructor()  {
    this.foo = new Foo({ opt: true });
  }
}

Expected behavior:
Error: Cannot instantiate abstract class 'Foo'. It does not implement abstract method(s): baz.
OR
Error: Cannot instantiate abstract class 'Foo'. It does not implement abstract method(s): foo, bar.
OR
Error: Cannot instantiate abstract class 'Foo'. It does not implement abstract method(s): baz (from Baz); foo, bar (from Bar).

Actual behavior:
Error: Cannot instantiate abstract class 'Foo'.

Bắt đầu bằng cách tái hiện chẩn đoán với Baz.d.ts, Bar.d.ts, Foo.d.ts và otherProject.ts, sử dụng hành vi của TypeScript 2.0.9 được mô tả ở đây. Truy vết lỗi khởi tạo lớp trừu tượng của trình biên dịch và làm cho thông báo xác định các phương thức trừu tượng hoặc khai báo liên quan bị thiếu. Được xem là hoàn tất khi ví dụ báo cáo lý do Foo không thể được khởi tạo, khớp với một trong các thông báo dự kiến được đề xuất.