[einpoklum]

I'm actually not curious about what Google's guides say, and don't accept them as technical leaders.

Having said that: It's not really unlike C++, since you have it in for loops:

    for (int x = 0; x < n; x++) { do_stuff(); }

which is like

    {
        int x;
        for (x = 0; x < n; x++) { do_stuff(); }
    }

anyway, I wouldn't mind the syntactic sugar of "with X=Y do Z" or "let X=Y in Z"