index.ts

class A {
  private foo;
  private bar;

  func() {
    console.log({
      a: () => { console.log(this.foo); }, // this is fine
      b() { console.log(this.bar); }, // here's the bug
    });
  }
}

tsconfig.json

{
  "include": ["*.ts"],
  "compilerOptions": {
    "noUnusedLocals": true,
    "target": "es5"
  }
}