test-repo/tests/flow/private_class_fields/test.js

//@flow
class A {
  #p: number
  constructor() {this.#p = 3}
}

class C {
  #p: number
  #q: number
  constructor() {
    this.#p = 0; // in scope
    this.#q; // in scope
  }
  test(other: C) {
    other.#q; // in lexical scope, object has the property.
  }
}

class D {
  #p: number // Note that C also has a #p with number, and #p is in
             // lexical scope
  constructor() {this.#p = 3}
  test(other: C) {
    other.#p; // Error: other does not have access to private variables in here.
  }
}

class Outer {
 #outer: number
 constructor() {
   var Inner = class A {
      #inner: Outer
      constructor() {
        this.#inner = new Outer();
        var x = new Outer();
        x.#outer = 0; // Both inner and outer should be visible here!
        x.#inner = new Outer(); // Error, #inner is not a private field of Outer
      }
   };
 }
}

class Clash {
  #p: number
  constructor() {
    var Inner = class A {
      #p: string
      constructor() {
        (this.#p : number); // Error, #p is a string not a number
        this.#p = "test";
        this.#p = 3; // Error, #p is a string not a number
        var x = new Clash();
        (x.#p : string) // Error, here #p is a number not a string
      }
    }
  }
}

class Refinements {
  #p: ?number
  constructor () {
    if (this.#p) {
      (this.#p : number); // Refinements work properly
    } else {
      (this.#p : number); // Error #p is null or undefined
    }
  }
}

class IncompatibleGetAndSet {
  #p: number
  static #q: number
  constructor () {
    const a: number = 3;
    a.#p = 3; // Error, #p not on number
    const b: {p: number} = {p: 3}
    b.#p; // Error, #p not on b.
  }
}

class Static {
  static #p: number
  static #q: number
  #r: number
  m(): number {
    Static.#p = 2;
    if (Static.#p === 3) { // Refinements still work
      (Static.#p : 3);
    }
    return Static.#p;
  }
 bad() {
   IncompatibleGetAndSet.#q; // Error, not visible here
   Static.#q = Static.#p;
   this.#p = 3; // Error, no #p on instance
   this.#q; // Error, no #q on instance
   Static.#r; // Error, no #r on class
   Static.#r = Static.#q; // Error, no #r on class
 }
}

class Annotations {
  // Private class fields must either be annotated or have an initializer
  #p: number;
  #q = 0;
  #r;
  #s: string = 0; // Error, number ~> string
  #t: string = "yay!";
  static #sp: number;
  static #sq = 0;
  static #sr;
  static #ss: string = 0; // Error, number ~> string
  static #st: string = "yay!";
  test1(): number {
    return this.#p;
  }
  test2(): number {
    return this.#t; // Error, string ~> number
  }
  test3(): number {
    return Annotations.#sp;
  }
  test4(): number {
    return Annotations.#st; // Error, string ~> number
  }
  test5(): number {
    return this.#r;
  }
  test6(): string {
    return this.#r; // Error, number ~> string
  }
  test5And6Helper() {
    this.#r = 3;
  }
  test7(): number {
    return Annotations.#sr;
  }
  test8(): string {
    return Annotations.#sr; // Error, number ~> string
  }
  test7And9Helper() {
    Annotations.#sr = 3;
  }
}

class RefinementClashes {
  // Refinements on private fields can be considered separately from the
  // rest of heap refinements
 #p: number;
 p: number;
 static q: number;
 static #q: number;
 test1() {
   if (this.#p === 3) {
     (this.p: 3); // Error, this.#p doesn't refine this.p
     (this.#p: 3);
     this.p = 4;
     (this.p: 4);
     (this.#p: 4); // Error, this.p doesnt refine this.#p
     (this.#p: 3); // this.p doesnt havoc this.#p
     this.#p = 3;
     (this.p: 3); // Error, this.#p doesnt refine this.p
     (this.p: 4); // this.#p doesnt havoc this.p
   }
   (this.#p: 3); // Error, Havoc happens as normal
 }
 test2() {
   if (RefinementClashes.#q === 3) {
     (RefinementClashes.q: 3); // Error, RefinementClashes.#q doesn't refine RefinementClashes.q
     (RefinementClashes.#q: 3);
     RefinementClashes.q = 4;
     (RefinementClashes.q: 4);
     (RefinementClashes.#q: 4); // Error, RefinementClashes.q doesnt refine RefinementClashes.#q
     (RefinementClashes.#q: 3); // RefinementClashes.q doesnt havoc RefinementClashes.#q
     RefinementClashes.#q = 3;
     (RefinementClashes.q: 3); // Error, RefinementClashes.#q doesnt refine RefinementClashes.q
     (RefinementClashes.q: 4); // RefinementClashes.#q doesnt havoc RefinementClashes.q
   }
   (RefinementClashes.#q: 3); // Error, Havoc happens as normal
 }
 test3(other: RefinementClashes) {
   if (this.#p === 3) {
     (this.#p: 3);
     other.#p = 3;
     (this.#p: 3); // Error, other.#p does havoc this.#p
   }
  }
}