For some reason, I always forget which variants are smaller and which
are larger when you derive PartialOrd on an enum. And the wording in the
current docs is not entirely clear to me.

So, I often end up making a small enum, deriving PartialOrd on it, and
then writing a `#[test]` with an assert that the top one is smaller than
the bottom one (or the other way around) to figure out which way the
deriving goes.

So then I figured, it would be great if the standard library docs just
had that example, so if I keep forgetting, at least I can figure it out
quickly by looking at std's docs.

Broken in rust-lang#85600

Co-authored-by: Boxy <supbscripter@gmail.com>

Add an example for deriving PartialOrd on enums

For some reason, I always forget which variants are smaller and which
are larger when you derive PartialOrd on an enum. And the wording in the
current docs is not entirely clear to me.

So, I often end up making a small enum, deriving PartialOrd on it, and
then writing a `#[test]` with an assert that the top one is smaller than
the bottom one (or the other way around) to figure out which way the
deriving goes.

So then I figured, it would be great if the standard library docs just
had that example, so if I keep forgetting, at least I can figure it out
quickly by looking at std's docs.

…tained, r=petrochenkov

Fix LLVM libunwind build for non-musl targets

Broken in rust-lang#85600. AFAICT, [only musl, mingw, and wasm](https://github.com/rust-lang/rust/blob/673d0db5e393e9c64897005b470bfeb6d5aec61b/compiler/rustc_target/src/spec/crt_objects.rs#L128-L132) should use the “self-contained” logic in rustbuild.

…t, r=RalfJung

Add test case for using `slice::fill` with MaybeUninit

Adds test for rust-lang#87891

Looks alright? `@RalfJung`
Fixes rust-lang#87891

small const generics cleanup

remove redundant / misplaced sentence from docs

Removes sentence that seems to have drifted down into the examples section. Luckily, someone already added an explanation of what happens with packed structs back into the initial section of the doc entry and this wayward sentence can likely just be deleted.

…nieu

Update outdated docs of array::IntoIter::new.

Update primitive docs for rust 2021.

Fixes rust-lang#87701