> Until Rust 1.53, only references to arrays implement IntoIterator. This means you can iterate over &[1, 2, 3] and &mut [1, 2, 3], but not over [1, 2, 3] directly.
...now, you can also iterate over [1, 2, 3] etc.
https://doc.rust-lang.org/edition-guide/rust-2021/IntoIterat...
"for x in myArray" works fine, just like "for x in myVector" but whereas "myVector.into_iter().foo()" does what you expect, "myArray.into_iter().foo() is actually giving foo an iterator over the references just as it would have in 2017 and now produces a warning about this into the bargain.
In Rust 2021 myArray.into_iter() does what a modern Rust programmer expects it to do, provide an iterator over myArray itself.
The warning does explain how you can get that iterator in 1.53.0 of course, but you need to write some ugly syntax whereas in Rust 2021 the obvious syntax just does what you expect as if arrays had always been IntoIterator.