add target features when extracting and running doctests
When rendering documentation, rustdoc will happily load target features into the cfg environment from the current target, but fails to do this when doing anything with doctests. This would lead to situations where, thanks to https://github.com/rust-lang/rust/pull/48759, functions tagged with `#[target_feature]` couldn't run doctests, thanks to the automatic `#[doc(cfg(target_feature = "..."))]`.
Currently, there's no way to pass codegen options to rustdoc that will affect its rustc sessions, but for now this will let you use target features that come default on the platform you're targeting.
Fixes https://github.com/rust-lang/rust/issues/49723
Merge the std_unicode crate into the core crate
[The standard library facade](https://github.com/rust-lang/rust/issues/27783) has historically contained a number of crates with different roles, but that number has decreased over time. `rand` and `libc` have moved to crates.io, and [`collections` was merged into `alloc`](https://github.com/rust-lang/rust/pull/42648). Today we have `core` that applies everywhere, `std` that expects a full operating system, and `alloc` in-between that only requires a memory allocator (which can be provided by users)… and `std_unicode`, which doesn’t really have a reason to be separate anymore. It contains functionality based on Unicode data tables that can be large, but as long as relevant functions are not called the tables should be removed from binaries by linkers.
This deprecates the unstable `std_unicode` crate and moves all of its contents into `core`, replacing them with `pub use` reexports. The crate can be removed later. This also removes the `CharExt` trait (replaced with inherent methods in libcore) and `UnicodeStr` trait (merged into `StrExt`). There traits were both unstable and not intended to be used or named directly.
A number of new items are newly-available in libcore and instantly stable there, but only if they were already stable in libstd.
Fixes#49319.
Use sort_by_cached_key where appropriate
A follow-up to https://github.com/rust-lang/rust/pull/48639, converting various slice sorting calls to `sort_by_cached_key` when the key functions are more expensive.
rustdoctest: suppress the default allow(unused) under --display-warnings
If you're passing rustdoc `--display-warnings`, you probably want to see the default ones too. This change modifies `test::make_test` to suppress the default `#![allow(unused)]` if the `--display-warnings` CLI flag was provided to rustdoc.
cc https://github.com/rust-lang/rust/issues/41574
rustdoc: add an --edition flag to compile docs/doctests with a certain edition
To correspond with the 2018 edition, this adds a (currently unstable) `--edition` flag to rustdoc that makes it compile crates and doctests with the given edition. Once this lands, Cargo should be updated to pass this flag when the edition configuration option is given.
Implement some trivial size_hints for various iterators
This also implements ExactSizeIterator where applicable.
Addresses most of the Iterator traits mentioned in #23708.
I intend to do more, but I don't want to make the PR too large.
