Comment by wezm

It kinda does if https://www.typescriptlang.org/play#example/discriminate-typ... is what you're referring to but it appears to be missing one of the major benefits: an error/warning if you haven't handled all variants.

Edit: lots of replies showing how TypeScript can be made to do exhaustiveness checking. It's neat and all but it's a lot of gymnastics compared to languages that just have this built in, which again is part of the appeal of Gleam for me.