Not allowing NULL & having weak metaprogramming options sounds like advantages to me. you still have metaprogramming using language templates & scope shadowing, that's not at runtime but it's clearly good enough.

The problem with Crystal is more with the small community than the concept itself which is pretty good IMO.

I'm not feeling it. Compile time only metaprogramming just doesn't feel powerful enough. Just a personal thing.

I'm definitely a fan of Crystal of though as a project and would really like to see a bigger community and more libraries etc.

They don't do it because runtime metaprogramming has a lot of disadvantages, it's difficult to optimize so it runs poorly, it throws away the static typing out of the window and it's difficult to debug. I spent hours debugging Rails code in the past because of the layers of monkey patching.

It also has a lot of advantages. It's as powerful as it is dangerous.

The real reason they don't do it is because they can't. It's inherently unsafe. In order to always be sure something is never null you have to be aware of what all it's inputs are so you can reason about it. That's not possible with runtime metaprogramming techniques.

I dunno I guess I just think it's an odd choice. Don't get me wrong, it's a neat experiment and I value it. I'm just slightly miffed that that particular experiment had to mixed in with what amounts to a statically typed language with the beauty and simplicity of Ruby but the friendliness and discoverability of static typing.

> would like to see a bigger community and more libraries

Better Windows support could make wonders.

Uh, it allows stuff to be nil if you declare the type of something to include nil. But then you also have to handle it. In practice, it make my code better.

Why would you need nulls to do metaprogramming?

Because it usually involves doing a lot of things that are unsafe. Take reflection for instance. There is no way to guarantee at compile time that a string whose value is only known at run-time is actually a real method in the code that can be invoked.

To get the level of safety they have gone for they have to disallow anything that could potentially blow up.

Why would that require nulls? They could use an Option type or just throw an exception.