[chaorace]

I suspect this is for two reasons:

* Many popular languages today predate modern asynchronous computing. This makes async-as-default impossible because it's an afterthought

* Async computing is harder to learn and confusing for those just picking up the language. There are some pretty major ergonomics issues that you have to solve if you want anything more than a DSL to achieve noteworthy adoption levels.

[devxpy]

> Many popular languages today predate modern asynchronous computing. This makes async-as-default impossible because it's an afterthought

Here's a rough sketch of how this can be achieved for a language that already has event loops -

Transpile the following -

    void main() {
        Future<int> xFuture = async doSomething()
        int x = doSomething()
         
        assert(await xFuture == x);
    }

Into -

    Future<void> main() async {
        Future<int> xFuture = (() async => await doSomething())();
        int x = await doSomething();
      
        assert(await xFuture == x);
    }

Now people can keep using a pre-existing `doSomething()` (that's either async or sync) and its compatible with our new caller based async statement.

BTW that transpiler output is runnable dart code actually works.

I know this has tons of edge cases that this simple example doesn't capture, but it's definitely "possible".