Cannot access variant accessors from other class method with `this` context

[whzx5byb]

Bug Report

🔎 Search Terms

🕗 Version & Regression Information

• This changed between versions 4.2.3 and 4.3.0-dev.20210330

⏯ Playground Link

Playground link with relevant code

💻 Code

class A {
  private _x: number = 0;

  get x() {
    return this._x;
  }

  protected set x(v: number) {
    this._x = v;
  }
}

class B {
  foo(this: A) {
    this.x = 1; // Property 'x' is protected and only accessible through an instance of class 'B'. This is an instance of class 'A'.(2446)
  }
}

function bar(this: A) {
  this.x = 1; // This is OK.
}

🙁 Actual behavior

The behavior of a protected setter is influenced by the accessibility of getter.
If you change the modifier of get x() to protected, the error will go away.

Also the error message is unclear. It says Property 'x' is protected and only accessible through an instance of class 'B', but x is only accessible through an instance of 'A', not 'B'.

🙂 Expected behavior

No error.