[Manishearth]

I don't think swift has borrowed much from Rust.

Rather, both are borrowing from older functional languages. These features are relatively new for procedural languages so it seems like Swift borrowed from Rust, but both have borrowed these features from other languages.

Rust did borrow `if let` from Swift (might have existed in other languages, but Swift is where the idea came from). I'm sure there are a few features swift has borrowed from Rust, but not many.

And it's not a bad thing to borrow! (As a Rustacean) I'm happy that Swift is similar to Rust. One of the problems with Rust is the learning curve for folks coming from other languages. With more languages similar to Rust, this is less of an issue. Swift in particular is set up to be used a lot since Apple is pushing it in its ecosystem, which is great.