Like so many modern web pages, swift.org seems to block/intercept/disable the cmd-left-click action on a link. This is supposed to open a link in a new tab but right now it simply opens the link in the current tab. This is incredibly annoying and requires using the right click menu to select "Open link in new tab".
I can't think of any useful reason for blocking this standard key/mouse combo. It's a real impediment to using the website, in my opinion.