This un-reverts the reverts of the rusti commits made awhile back. These were reverted for an LLVM failure in rustpkg. I believe that this is not a problem with these commits, but rather that rustc is being used in parallel for rustpkg tests (in-process). This is not working yet (almost! see #7011), so I serialized all the tests to run one after another.

@brson, I'm mainly just guessing as to the cause of the LLVM failures in rustpkg tests. I'm confident that running tests in parallel is more likely to be the problem than those commits I made.

Additionally, this fixes two recently reported issues with rusti.

…Manishearth

extend `single_element_loop` to match `.iter()`

This extends `single_element_loop` to also match `[..].iter()` in the loop argument. Related to rust-lang#7125, but not completely fixing it due to the lint only firing if the array expression contains a local variable.

---

changelog: none

…t-loop-over-range, r=llogiq

suggest alternatives to iterate an array of ranges

works towards rust-lang#7125
changelog: [`single_element_loop`]: suggest better syntax when iterating over an array of a single range

`@thinkerdreamer` and myself worked on this issue during a workshop by `@llogiq` at the RustLab 2023 conference. It is our first contribution to clippy.

When iterating over an array of only one element, _which is a range_, our change suggests to replace the array with the contained range itself. Additionally, a hint is printed stating that the user probably intended to iterate over the range and not the array. If the single element in the array is not a range, the previous suggestion in the form of `let {pat_snip} = {prefix}{arg_snip};{block_str}`is used.

This change lints the array with the single range directly, so any prefixes or suffixes are covered as well.