Convert to class declaration quick fix misses superclass

TypeScript Version: 3.4.3

Search Terms:

• class declaration quick fix
• 80002

Code

This code is a mix of ES2015- and function-style classes:

class A {
  constructor() {
    this.a = 'a';
  }
  doAThing() {
    console.log(this.a);
  }
}

/**
 * @constructor
 * @extends {A}
 */
function B() {
  this.b = 'b';
}
B.prototype = new A();

B.prototype.doBThing = function() {
  console.log('b: ', b);
};

The TS language services offer a quickfix to convert B into an ES2015 class. Great!

Expected behavior:

I'd hope that one of (or both of) the @extends and B.prototype = new A(); would result in B extends A:

class B extends A {
  constructor() {
    super();
    this.b = 'b';
  }
  doBThing() {
    console.log('b: ', b);
  }
}

Actual behavior:

The quick fix produces this code:

/**
 * @constructor
 * @extends {A}
 */
class B {
  constructor() {
    this.b = 'b';
  }
  doBThing() {
    console.log('b: ', b);
  }
}
B.prototype = new A();

TypeScript flags an error on the last line:

(property) B.prototype: B
Type 'A' is missing the following properties from type 'B': b, doBThingts(2739)

Playground Link: no quickfixes on the playground, alas!

Related Issues:

Start with the TypeScript language service quick fix that converts a function-style class into an ES2015 class, using the supplied example as the reproduction. Check how the @extends annotation and B.prototype = new A() are handled, then verify that the converted class preserves the superclass relationship and no longer produces the reported type error.