…rator

also add smoke test to detect relocation even in rustc runs

… regions away

…nieu

Fix some aliasing issues in Vec

`Vec::extend` and `Vec::truncate` invalidated references into the vector even without reallocation, because they (implicitly) created a mutable reference covering the *entire* initialized part of the vector.

Fixes rust-lang#70301
I verified the fix by adding some new tests here that I ran in Miri.

docs: make the description of Result::map_or more clear

The documentation of [`Result::map_or`](https://doc.rust-lang.org/std/result/enum.Result.html#method.map_or) is very unclear and confusing, probably because it was copied straight from [`Option::map_or`](https://doc.rust-lang.org/std/option/enum.Option.html#method.map_or) and someone forgot to adapt it for Result.

Miri: remove an outdated FIXME

We even [have a test ](https://github.com/rust-lang/rust/blob/49dc2f9f091748beb1a8a9d5b3eb3bbe7362c3bd/src/test/ui/consts/miri_unleashed/drop.rs) making sure that we detect dropping with a non-const implementation.

r? @oli-obk

…ekmann

clarify comment in RawVec::into_box

On first reading I almost thought "len <= cap" would be all that there is to check here. Expand the comment to clarify that that is not the case.

…ddyb

fix Miri assignment sanity check

Thanks @eddyb for pointing me to the right APIs!

r? @eddyb
Fixes rust-lang#70804