…g to FFI

The UEFI variables set by the env vars should be volatile, otherwise
they will persist after reboot and use up scarce non-volatile storage.

should-fail is only meant for testing the compiletest framework itself.
It checks that the test runner itself panicked.

Instead keep parent modules in `DeclData` itself

Otherwise the std testsuite fails on older kernels.

…ndancy

When encountering code like `impl<N> Bar<N> for [u8; N]`, suggest `impl<const N: Type> Bar<N> for [u8; N]` as a possibility.

```
error[E0423]: expected value, found type parameter `T`
  --> $DIR/issue-69654.rs:5:25
   |
LL | impl<T> Bar<T> for [u8; T] {}
   |      -                  ^ not a value
   |      |
   |      found this type parameter
   |
help: you might have meant to write a const parameter here
   |
LL | impl<const T: /* Type */> Bar<T> for [u8; T] {}
   |      +++++  ++++++++++++
```

It's described as a "backwards compatibility hack to keep the diff
small". Removing it requires only a modest amount of churn, and the
resulting code is clearer without the invisible derefs.

…ross35,dtolnay

refactor: remove Ord bound from BinaryHeap::new etc

This adds consistency with e.g `BTreeMap::new`, and makes it easier to e.g `#[derive(Default)]`[^1]

[^1]: https://play.rust-lang.org/?version=stable&mode=debug&edition=2024&gist=f848e472a176fae155f17455bdfe0aee

…bk,BoxyUwU,fmease

Change some `matches!(.., .. if ..)` with let-chains

Follow up to rust-lang#149933.

std: move `errno` and related functions into `sys::io`

Part of rust-lang#117276.

Currently, `errno` and related functions like `decode_error_kind` are split across `sys::pal` and `sys::pal::os`. This PR moves all of them into a new module inside `sys::io`.

resolve: Refactor away the side table `decl_parent_modules`

Instead keep parent modules in `DeclData` itself.
Follow up to rust-lang#150445.

r? @nnethercote

…ieb,workingjubilee

Update to_uppercase docs to avoid ß->SS example

Fixes rust-lang#150888

Updates the `to_uppercase` documentation examples to avoid relying on the ß → "SS" mapping and instead uses a stable multi-character case-mapping example ('ffi' → "FFI").

Note: the example uses U+FB03 (LATIN SMALL LIGATURE FFI), not the ASCII string "ffi".

std: Change UEFI env vars to volatile storage

The UEFI variables set by the env vars should be volatile, otherwise they will persist after reboot and use up scarce non-volatile storage.

CC @Ayush1325

Better handle when trying to iterate on a `Range` of a type that isn't `Step`

Mention when a trait bound corresponds to an unstable trait.

Mention `Range` when `Step` bound is unment, and explain that only some std types impl `Iterator` for `Range`.

CC rust-lang#151026

Avoid should-fail in two ui tests and a codegen-llvm test

`should-fail` is only meant for testing the compiletest framework itself. It checks that the test runner itself panicked.

With this there are still a bunch of rustdoc-html tests that use it due to this test suite not supporting anything like `//@ doc-fail`.