Avoid collecting an interator just to re-iterate immediately.
Rather reuse the previous iterator. (clippy::needless_collect)

Following up on rust-lang#87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.

Use `/etc/os-release` instead of `/etc/NIXOS`.
The latter one does not exist on NixOS when using tmpfs as root.

Fix NixOS detection

Use `/etc/os-release` instead of `/etc/NIXOS` for detection.
The latter one does not exist on NixOS when using tmpfs as root.

…dtwco

avoid temporary vectors/reuse iterators

Avoid collecting an interator just to re-iterate immediately.
Rather reuse the previous iterator. (clippy::needless_collect)

…low, r=notriddle

Fix docblock <table> overflow

Before:

![Screenshot from 2021-07-18 00-05-23](https://user-images.githubusercontent.com/3050060/126050272-ce08bc5f-74ff-4135-bc12-d708d87470cc.png)

After:

![Screenshot from 2021-07-18 00-03-55](https://user-images.githubusercontent.com/3050060/126050273-42f41b4d-ad57-4a87-91de-18e63f8504ec.png)

cc `@SergioBenitez`

r? `@notriddle`

…=oli-obk

Recognize bounds on impls as const bounds

r? ```@oli-obk```

…alfJung

Add comments explaining the unix command-line argument support.

Following up on rust-lang#87236, add comments to the unix command-line argument
support explaining that the code doesn't mutate the system-provided
argc/argv, and that this is why the code doesn't need a lock or special
memory ordering.

r? ```@RalfJung```

…n514

Fix typo in compile.rs

…bank

Get back the more precise suggestion spans of old regionck

I noticed that when you turn on nll, the structured suggestion replaces a snippet instead of appending a snippet. It seems clearer to the user to only highlight the newly added characters instead of the entire `impl Trait` (and old regionck already does it this way).

r? ``@estebank``

…eGomez

Add long explanation for E0722

Helps with rust-lang#61137

…eGomez

Add long explanation for E0757

Helps with rust-lang#61137