This is a Hopper plugin (not script) written in Swift for demangling Swift symbols.
Download the latest release from here. Then:
$ unzip SwiftDemangle.hopperTool.zip
$ mkdir -p ~/Library/Application\ Support/Hopper/PlugIns/v4/Tools/
$ mv Swift\ Demangle.hopperTool ~/Library/Application\ Support/Hopper/PlugIns/v4/Tools/
Once you've installed the plugin you should have a new Tool Plugins menu item. There you can see the added Swift demangle commands.
