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Typescript declaration order triggers runtime error

Looking for a problem I have, I found statements that the order of the class declarations does not matter in Typescript , and that 'forward declarations' are not necessary.

In the project that I am considering right now, this statement does not seem to be delayed. I confused the problem with a simple reproducible example where, although the compiler does not complain, we fail at runtime:

$ cat bug.ts
class A extends B {
    constructor(public id:number) {
        super(id);
        console.log("A():" + id);
    }
}

class B {
    constructor(public id:number) {
        console.log("B():" + id);
    }
}

var a = new A(12);

$ tsc  bug.ts
$ node  bug.js

/home/ttsiod/work/a/bug.js:4
    __.prototype = b.prototype;
                    ^
TypeError: Cannot read property 'prototype' of undefined
    at __extends (/home/ttsiod/work/a/bug.js:4:21)
    at /home/ttsiod/work/a/bug.js:8:5
    at Object.<anonymous> (/home/ttsiod/work/a/bug.js:15:3)
    at Module._compile (module.js:456:26)
    at Object.Module._extensions..js (module.js:474:10)
    at Module.load (module.js:356:32)
    at Function.Module._load (module.js:312:12)
    at Function.Module.runMain (module.js:497:10)
    at startup (node.js:119:16)
    at node.js:901:3

Either I’m missing a keyword that I don’t know about, or the statement “the order of the announcement does not matter” is not as general as one might think.

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