There are many cases where you can replace a call to `.iter()` in your Rust code to a call to `.par_iter()` from `rayon`. Those cases are trivial, and it's great.
That's a very nice feature but I don't know that it belongs in the category of new ideas from programming language theory. Fortran 90 had automatically parallelized language constructs and OpenMP added them to C and C++ as compiler intrinsics in 2002.
