Move A|Rc::as_ptr from feature(weak_into_raw) to feature(rc_as_ptr)

These were stabilized alongside the Weak versions, but having `feature = "weak_.."` on a fn definition for the non-weak pointers is potentially very misleading, especially in a review context where the impl header may not be immediately visible.

r? @RalfJung
@bors rollup=always

mir: mark mir construction temporaries as internal

Fixes #73914.

This PR marks temporaries from MIR construction as internal such that they are skipped in `sanitize_witness` (where each MIR local is checked to have been contained within the generator interior computed during typeck). This resolves an ICE whereby the construction of checked addition introduced a `(u64, bool)` temporary which was not in the HIR and thus not in the generator interior.

r? @matthewjasper

libstd/net/tcp.rs: #![deny(unsafe_op_in_unsafe_fn)]

Enclose unsafe operations in unsafe blocks for net/tcp.rs. Fixes part of #73904.

Audit hidden/short code suggestions

Should fix #73641.
Audit uses of `span_suggestion_short` and `tool_only_span_suggestion` (`span_suggestion_hidden` is already tested with `run-rustfix`). Leave some FIXMEs for futher improvements/fixes.
r? @estebank

typeck: adding type information to projection

This commit modifies the Place as follow:
* remove 'ty' from ProjectionKind
* add type information into to Projection
* replace 'ty' in Place with 'base_ty'
* introduce 'ty()' in `Place` to return the final type of the `Place`
* introduce `ty_before_projection()` in `Place` to return the type of
  a `Place` before i'th projection is applied

Closes https://github.com/rust-lang/project-rfc-2229/issues/5

Edit librustc_lexer top-level docs

Minor edit, and adds link to librustc_parse::lexer.

[rustdoc] Page hash handling

Fixes https://github.com/rust-lang/rust/issues/70476

A good example to see the change is to use this URL: https://doc.rust-lang.org/nightly/std/string/struct.String.html#from_iter.v-3

After the change, it actually goes to the target element (and change the page hash to something more clear for the users).

r? @kinnison

cc @ollie27

Add link to librustc_parse::lexer

Rollup of 12 pull requests

Successful merges:

 - #72688 (added .collect() into String from Box<str>)
 - #73787 (Add unstable docs for rustc_attrs)
 - #73834 (Some refactoring around intrinsic type checking)
 - #73871 (Fix try_print_visible_def_path for Rust 2018)
 - #73937 (Explain exhaustive matching on {usize,isize} maximum values)
 - #73973 (Use `Span`s to identify unreachable subpatterns in or-patterns)
 - #74000 (add `lazy_normalization_consts` feature gate)
 - #74025 (Remove unnecessary release from Arc::try_unwrap)
 - #74027 (Convert more `DefId`s to `LocalDefId`s)
 - #74055 (Fix spacing in Iterator fold doc)
 - #74057 (expected_found `&T` -> `T`)
 - #74064 (variant_count: avoid incorrect dummy implementation)

Failed merges:

r? @ghost

variant_count: avoid incorrect dummy implementation

This also avoids a stage 0 doctest failure.

expected_found `&T` -> `T`

Fix spacing in Iterator fold doc

Convert more `DefId`s to `LocalDefId`s

Remove unnecessary release from Arc::try_unwrap

The thread that recovers the unique access to Arc inner value (e.g., drop
when ref-count strong reaches zero, successful try_unwrap), ensures that
other operations on Arc inner value happened before by synchronizing
with release operations performed when decrementing the reference counter.

When try_unwrap succeeds, the current thread recovers the unique access
to Arc inner value, so release is unnecessary.

r? @Amanieu

add `lazy_normalization_consts` feature gate

In #71973 I underestimated the amount of code which is influenced by lazy normalization of consts
and decided against having a separate feature flag for this.

Looking a bit more into this, the following issues are already working with lazy norm in its current state #47814 #57739 #73980

I therefore think it is worth it to enable lazy norm separately. Note that `#![feature(const_generics)]` still automatically activates
this feature, so using `#![feature(const_generics, lazy_normalization_consts)]` is redundant.

r? @varkor @nikomatsakis

Use `Span`s to identify unreachable subpatterns in or-patterns

Fixes #71977

Explain exhaustive matching on {usize,isize} maximum values

The wording is taken from https://github.com/rust-lang/rfcs/blob/master/text/2591-exhaustive-integer-pattern-matching.md#reference-level-explanation.
Fixes #73919

r? @varkor

Fix try_print_visible_def_path for Rust 2018

The recursive check of `try_print_visible_def_path` did not properly handle the Rust 2018 case of crate-paths without 'extern crate'. Instead, it returned a "not found" via (false, self).

 This fixes #56175.

Some refactoring around intrinsic type checking

So... This PR went a bit overboard. I wanted to make the `rustc_peek` intrinsic safe (cc @ecstatic-morse ), and remembered a long-standing itch of mine. So I made that huge `&str` match for the intrinsic name a match on `Symbol`s (so basically `u32`s). This is unlikely to have a positive perf effect, even if it likely has better codegen (intrinsics are used rarely, mostly once in their wrapper), so it's mostly a consistency thing since other places actually match on the symbol name of the intrinsics.

Add unstable docs for rustc_attrs

r? @RalfJung

added .collect() into String from Box<str>

I have not created an rfc, because i felt like this is a very minor change.

i have just set a random feature name and rust version as stability attribute, i expect to have to change that, i just don't know what the policy on that is. all guides i could find focused on contributing to the compiler, not contributing to the standard library.

drawbacks: more code in the standard library, could be replaced with specialization: base-implementation for AsRef\<str> and specialization for String and Cow. i can write that code if ppl want it.

advantages: using "real strings" i.e. Box\<str> is as ergonomic as string slices (&str) and string buffers (String) with iterators.

Handle inactive enum variants in `MaybeUninitializedPlaces`

Resolves the first part of #69715.

This is the equivalent of #68528 but for `MaybeUninitializedPlaces`. Because we now notify drop elaboration that inactive enum variants might be uninitialized, some drops get marked as ["open" that were previously "static"](https://github.com/rust-lang/rust/blob/e0e5d82e1677c82d209b214bbfc2cc5705c2336a/src/librustc_mir/transform/elaborate_drops.rs#L191). Unlike in #69715, this isn't strictly better: An "open" drop expands to more MIR than a simple call to the drop shim. However, because drop elaboration considers each field of an "open" drop separately, it can sometimes eliminate unnecessary drops of moved-from or unit-like enum variants. This is the case for `Option::unwrap`, which is reflected in the `mir-opt` test.

cc @EddyB
r? @oli-obk

Co-authored-by: Nvarkor <github@varkor.com>

The thread that recovers the unique access to Arc inner value (e.g., drop
when ref-count strong reaches zero, successful try_unwrap), ensures that
other operations on Arc inner value happened before by synchronizing
with release operations performed when decrementing the reference counter.

When try_unwrap succeeds, the current thread recovers the unique access
to Arc inner value, so release is unnecessary.

ship rust analyzer

This successfully  builds rust-analyzer as a part of rust repo. I haven't yet added required changes to dist.rs -- seems like I just have to copy-paste quite a bit of code I don't really understand :-)

Rollup of 12 pull requests

Successful merges:

 - #73140 (Fallback to xml.etree.ElementTree)
 - #73670 (Add `format_args_capture` feature)
 - #73693 (Use exhaustive match in const_prop.rs)
 - #73845 (Use &raw in A|Rc::as_ptr)
 - #73861 (Create E0768)
 - #73881 (Standardize bibliographic citations in rustc API docs)
 - #73925 (Improve comments from #72617, as suggested by RalfJung)
 - #73949 ([mir-opt] Fix mis-optimization and other issues with the SimplifyArmIdentity pass)
 - #73984 (Edit docs for rustc_data_structures::graph::scc)
 - #73985 (Fix "getting started" link)
 - #73997 (fix typo)
 - #73999 (Bump mingw-check CI image from Ubuntu 16.04 to 18.04.)

Failed merges:

 - #74000 (add `lazy_normalization_consts` feature gate)

r? @ghost

Bump mingw-check CI image from Ubuntu 16.04 to 18.04.

I chose 18.04 because we use it for other builders, and it's enough to get a version of MinGW that can build `libssh2-sys`.

This is a prereq for #73902, where `libssh2-sys` shows up as an indirect dependency of `x.py check src/tools/semverver` (through `src/tools/cargo`, which we don't currently `x.py check` because it's not in-tree). See also https://github.com/rust-lang/rust/pull/73902#issuecomment-652414502.

r? @Mark-Simulacrum cc @mati865

fix typo

r? @Dylan-DPC

Fix "getting started" link

The previous link is 404.