SlackBuildsOrg/development/swift

Swift is a general-purpose programming language built using a modern
approach to safety, performance, and software design patterns.

It is intended as a replacement for C-based languages (C, C++, and
Objective-C). As such, Swift must be comparable to those languages in
performance for most tasks. Performance must also be predictable and
consistent, not just fast in short bursts that require clean-up later.

It ships with its own LLDB.