Private Members with Default Value on Class Extension Compiles with Member declarations before Super call if function is called before super

[jamelcole-ah]

TypeScript Version: 3.3.0-dev.201xxxxx

Search Terms:

• "Private member compile"
• "Private Properties before super"
• "compile class extension"
• "constructor order at compile time"
• "functions before super call"
  Code

function example ( number: number ) {
    return number;
} 
class ExtString extends String {
    private x: number;
    private y: number = 10;
    z: number;
    constructor(...args){
        example(args[0]);
        super(...args);
        this.z = 19;
    }
}

Expected behavior:
I would expect that when the above code compiles, that the private members get initialized with values after the super call like below:

function example(number) {
    return number;
}
class ExtString extends String {
    constructor(...args) {
        example(args[0]);
        super(...args);
        this.y = 10;
        this.z = 19;
    }
}

Actual behavior:
the private members which have values gets assigned to before the super call. This behaviour only happens when I call a function before a super call, even if said function does not alter this in the code (like below).

function example(number) {
    return number;
}
class ExtString extends String {
    constructor(...args) {
        this.y = 10;
        example(args[0]);
        super(...args);
        this.z = 19;
    }
}

This results in a compile time error.

Related Issues:
I found a similar bug that is referenced here #8277

[jamelcole-ah]

Given this issue has yet to be resolved, I wanted to share a current work around with anyone who may be experiencing this as well:

When creating private memebers, if you don't provide them with default values in the head of your class, but instead initialize them in the constructor explicitely, it will compile correctly.

i.e.

function example ( number: number ) {
    return number;
} 
class ExtString extends String {
    private x: number;
    private y: number;
    z: number;
    constructor(...args){
        example(args[0]);
        super(...args);
        this.z = 19;
        this.y = 10;
        this.x = 20;
    }
}