Sorry, I just didn't want to give people the impression that it's more difficult than other languages. To upgrade you'd just have to remove the original install directory and untar the new release.
I'm not familiar with Snap, but I did find https://snapcraft.io/swift
Also, upgrading will be less common than Rust since almost everyone uses the latest release/toolchain. There's not really a reason to use the daily builds unless you're contributing to the Swift project.