Cool to see Java getting these features. After having been a Java dev most of my life, and then moving to Typescript years ago, it's hard to believe I went so long without this.

Related, Typescript is the only language I know of that through flow analysis does not require you to redefine the variable. E.g. you can do something like

  if (typeof foo === 'string') {
    //Typescript knows foo is a string here
  }

All the other languages I know of, like this proposal for Java, require the variable to be redefined. I personally find the Typescript way, as VSCode will give you appropriate type warnings in the right places, easier to use in practice. Just curious if there are any other languages that do it like TS.

Don't be mistaken, Typescript do not has proper pattern matching support, The proposal is far from being adopted https://github.com/tc39/proposal-pattern-matching

> Related, Typescript is the only language I know of that through flow analysis does not require you to redefine the variable. E.g. you can do something like

This is called smart casting and is widely used in Kotlin