[actionfromafar]

What languages could fit that description today? I don't really understand what it even means but maybe I could understand better if I could look at examples in languages which have them.

[phi-go]

For example Rust: https://doc.rust-lang.org/std/keyword.enum.html

[jghn]

Also Scala

[seivan]

Swift, Typescript depending on your opinion with structural typing, and Rust.

Think Scala, Elm and Haskell have it as well.

Having that and elixirs pattern matching would be insane.