Programming

I wouldn't use this and most people will forget that it exists. Most of the time you have do use the language and avoid hacks like that.

Don't you have alternatives in Dart?

overwriting [] seems like readability nightmare.

Won't something like this work more clearly?

extension NullCall<T> on T? {
  R? let<R>(R Function(T) f) => this == null ? null : f(this as T);
}

void example() {  
  int? n;  
  n.let(math.sqrt);
}  

This kind of immitates Kotlin let.

So you're using [] as an alternative function call syntax to (), usable with nullable parameters?

What's the alternative? let x = n is null ? null : math.sqrt(n);?

In principle, I like the idea. I wonder whether something with a question mark would make more sense, because I'm used to alternative null handling with question marks (C#, ??, ?.ToString(), etc). And I would want to see it in practice before coming to an early conclusion on whether to establish as a project principle or not.

math.sqrt?() may imply the function itself may be null. (? ) for math.sqrt(?n)? 🤔

I find [] problematic because it's an index accessor. So it may be ambiguous between prop or field indexed access and method optional param calls. Dunno how that is in Dart specifically.

Don't overload things if the semantics don't match. You're not accessing something in a container; you're calling a function.