Description

David Koblas (koblas)

opened on Jan 31, 2018

Issue body actions

Upgrading from TypeScript 2.6.2 to 2.7.1 and got a private variable scoping problem.

TypeScript Version: 2.7.1

Search Terms:

private property does not exist

Code

class Parent {
  pubValue: number;

  private priValue: number;
  private priXXX: number;

  constructor(value: number) {
    this.priValue = value;
    this.pubValue = 7;
  }

  cloneImpl(kind: boolean): Child | OtherChild {
    const copy = kind ? new Child(this.priValue) : new OtherChild(this.priValue);
    copy.pubValue = this.pubValue + 1;
    copy.priXXX = this.priXXX;

    return copy;
  }
}

class Child extends Parent {
  myData: number;

  clone() {
    return this.cloneImpl(true) as Child;
  }
}

class OtherChild extends Parent {
  clone() {
    return this.cloneImpl(false) as OtherChild;
  }
}

const child = new Child(6);

child.clone();

Expected behavior:

In typescript 2.6.2 the code was working and not generating an error. Since cloneImpl() is in the parent class it should have access to it's own private (tried with protected as well) variables.

Actual behavior:

test.ts (16,10): Property 'priXXX' does not exist on type 'Child | OtherChild'. (2339)

Playground Link:

https://www.typescriptlang.org/play/#src=class%20Parent%20%7B%0D%0A%20%20pubValue%3A%20number%3B%0D%0A%0D%0A%20%20protected%20priValue%3A%20number%3B%0D%0A%20%20protected%20priXXX%3A%20number%3B%0D%0A%0D%0A%20%20constructor(value%3A%20number)%20%7B%0D%0A%20%20%20%20this.priValue%20%3D%20value%3B%0D%0A%20%20%20%20this.pubValue%20%3D%207%3B%0D%0A%20%20%7D%0D%0A%0D%0A%20%20cloneImpl(kind%3A%20boolean)%3A%20Child%20%7C%20OtherChild%20%7B%0D%0A%20%20%20%20const%20copy%20%3D%20kind%20%3F%20new%20Child(this.priValue)%20%3A%20new%20OtherChild(this.priValue)%3B%0D%0A%20%20%20%20copy.pubValue%20%3D%20this.pubValue%20%2B%201%3B%0D%0A%20%20%20%20copy.priXXX%20%3D%20this.priXXX%3B%0D%0A%0D%0A%20%20%20%20return%20copy%3B%0D%0A%20%20%7D%0D%0A%7D%0D%0A%0D%0Aclass%20Child%20extends%20Parent%20%7B%0D%0A%20%20myData%3A%20number%3B%0D%0A%0D%0A%20%20clone()%20%7B%0D%0A%20%20%20%20return%20this.cloneImpl(true)%20as%20Child%3B%0D%0A%20%20%7D%0D%0A%7D%0D%0A%0D%0Aclass%20OtherChild%20extends%20Parent%20%7B%0D%0A%20%20clone()%20%7B%0D%0A%20%20%20%20return%20this.cloneImpl(false)%20as%20OtherChild%3B%0D%0A%20%20%7D%0D%0A%7D%0D%0A%0D%0Aconst%20child%20%3D%20new%20Child(6)%3B%0D%0A%0D%0Achild.clone()%3B

Related Issues:

None found

Activity

1. David Koblas (koblas)

   changed the title [-]regression with private class members and loosing visibility.[/-] [+]regression with private class members and loosing visibility[/+] on Jan 31, 2018
2. mhegazy commented on Jan 31, 2018

   

   Mohamed Hegazy (mhegazy)

   on Jan 31, 2018

   Contributor

   More actions

   This is a side effect of #19671. the type copy is now inferred as Child | OtherChild instead of just Child. private properties are not exposed on the union, since it is not always possible to know if they are applicable to the specific use case or not.
   A work around would be to use a type assertion as:

    const copy = kind ? new Child(this.priValue) : <Child> new OtherChild(this.priValue);
3. Mohamed Hegazy (mhegazy)

   added

   Breaking ChangeWould introduce errors in existing codeWould introduce errors in existing code

   on Jan 31, 2018
4. Mohamed Hegazy (mhegazy)

   closed this as completedon Mar 9, 2018
5. microsoft

   locked and limited conversation to collaborators on Jul 25, 2018

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