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Comment by charcircuit | Hacker News Reader

It's always bothered me how

  public A(String s) {
   this(s.isEmpty());
  }

is allowed but

  public A(String s) {
    boolean helpfulName = s.isEmpty();
    this(helpfulName);
  }

isn't

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There's something to be said for making sure the parent constructor is the first call made. It means any method you call in the current constructor will work correctly or obviously be your fault, not the parent class's.

Yes, in your particular case, the compiler could figure out that you're not using "this," but you can only make a compiler so clever.

It's not too hard to make the compiler (or more specifically, the language) know about this. The solution isn't even that clever, you just don't put "this" into scope until the super() call.

It's not that simple, because you can't find where super is called in the general case. Consider: `var foo = { bar: super }; foo['b' + 'a' + 'r']();` - you need to evaluate it in order to define scoping. But JS has lexical scoping as a design choice...

This article is about Java, your comment is about JavaScript.

Ooof. Didn't realize it. Still, I believe the same applies, we can't dynamically analyze pointers at the time scoping must be settled.

What does it have to do with pointers? super() in Java is a special language construct, it's not a method that you can have a pointer to. Thus it can be analyzed exactly the same as e.g. definitive variable assignment, and "this" be unavailable on any codepath on which super() has not been definitively called.

Yes, though in that case you can use

  public A(String s) {
    this(helpfulName(s));
  }

with a static method.

bingo - exactly the way to do it in java

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