alt Hacker NewsFWIW, as far back as 2015 my feature check library documents Visual Studio as supporting "__typeof".[1] Note the leading but not trailing underscores. Perhaps I was mistaken, but I usually tested that sort of thing. It's also possible __typeof had slightly different semantics.
[1] See https://github.com/wahern/autoguess/blob/b44556e4/config.h.g... (that's the 2015 revision, but HEAD has the same code).
msvc 19.39 is the first to support it, which I mention in the article. You can confirm it didn't work up through 19.38 in godbolt [1]. I don't use Visual Studio, so I don't know what version of that first started using msvc 19.39
[1] https://godbolt.org/z/M7zPYdssP