It is used exactly once and can be replaced with the equally fast
.as_str().len()

Avoids a bunch of manual pointer manipulation.

Currently, with the new 2021 edition, if a closure captures all of the
fields of an upvar, we'll drop those fields in the order they are used
within the closure instead of the normal drop order (the definition
order of the fields in the type).

This changes that so we sort the captured fields by the definition order
which causes them to drop in that same order as well.

Fixes rust-lang/project-rfc-2229#42

Co-authored-by: Josh Triplett <josh@joshtriplett.org>

…lbini

Add 1.56.0 release notes

Notable things:

* Rustdoc section currently absent, for lack of things to call out that I could find. It seems like rust-lang#87451 is the only potential candidate, but that seems like more of a bugfix and doesn't seem to warrant inclusion to me. But we can add it if desired.

As with the 1.55.0 release notes, my intent is to leave this open for approximately 1-2 weeks at the early part of the cycle, and then merge it in (after fixing any feedback). Further iteration can happen in subsequent issues (and PRs).

[Rendered](https://github.com/Mark-Simulacrum/rust/blob/relnotes/RELEASES.md)

…akis

Be explicit about using Binder::dummy

This is somewhat of a late followup to the binder refactor PR. It removes `ToPredicate` and `ToPolyTraitImpls` that hide the use of `Binder::dummy`. While this does make code a bit more verbose, it allows us be more careful about where we create binders.

Another alternative here might be to add a new trait `ToBinder` or something with a `dummy()` fn. Which could still allow grepping but allows doing something like `trait_ref.dummy()` (but I also wonder if longer-term, it would be better to be even more explicit with a `bind_with_vars(ty::List::empty())` *but* that's not clear yet.

r? ``@nikomatsakis``

…lwoerister

Avoid a couple of Symbol::as_str calls in cg_llvm

This should improve performance a tiny bit. Also remove `Symbol::len` and make `SymbolIndex` private.

…nagisa,bjorn3

Simplify scoped_thread

Avoids a bunch of manual pointer manipulation in favor of using the appropriate std API.

…ikomatsakis

[rfc 2229] Drop fully captured upvars in the same order as the regular drop code

Currently, with the new 2021 edition, if a closure captures all of the
fields of an upvar, we'll drop those fields in the order they are used
within the closure instead of the normal drop order (the definition
order of the fields in the type).

This changes that so we sort the captured fields by the definition order
which causes them to drop in that same order as well.

Fixes rust-lang/project-rfc-2229#42

r? `@nikomatsakis`

Add missing time complexities to linked_list.rs

Most functions in LinkedList have time complexities in their description:
Like push front:

```
Adds an element first in the list.

This operation should compute in O(1) time.
```

Time complexities were missing for the following, so I've added them in this PR:

contains: O(n)
front: O(1)
front_mut: O(1)
back: O(1)
back_mut: O(1)

…-rust-tools, r=jyn514

Enable "generate-link-to-definition" option on rust tools docs as well

Just realized that we enable the option for the compiler crates, but we don't have it for rustdoc and the other tools documentation...

Part of rust-lang#89095.

cc ``@rust-lang/rustdoc``
r? ``@Mark-Simulacrum``

…bank

Give better error for `macro_rules! name!`

r? ``@estebank``

``@rustbot`` modify labels: +A-diagnostics +A-parser