Ask HN: What are the nice feature you need in a programming language?

I'm developing a programming language, the keywords and features mostly based on Swift 5 but some additional features like,

1. async function will be called from no async function but no async/await keyword. If you want to block main thread then block_main() function will be used. block_main() /* operations */ unblock_main()

2. protocol can inherit another protocol(s) & protocol can confirm a class like swift.

3. no `let`. only `var`. compiler can optimize further.

4. if (a == (10 || 20 || 30) || b == a) && c { }

5. `Asterisk` is replaced to `x` operator for mul operations.

What are the features you found or you need in a programming language?