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.
Impressing confused Python users with magical diagnostics is perhaps
worth this not-grossly-unreasonable (only 40ish lines) extra complexity
in the parser?
Thanks to Vadim Petrochenkov for guidance.
This resolves#46836.
Expand macros in `extern {}` blocks
This permits macro and proc-macro and attribute invocations (the latter only with the `proc_macro` feature of course) in `extern {}` blocks, gated behind a new `macros_in_extern` feature.
A tracking issue is now open at #49476closes#48747
Expand Attributes on Statements and Expressions
This enables attribute-macro expansion on statements and expressions while retaining the `stmt_expr_attributes` feature requirement for attributes on expressions.
closes#41475
cc #38356 @petrochenkov @jseyfried
r? @nrc
Fix escaped backslash in windows file not found message
When a module is declared, but no matching file exists, rustc gives
an error like `help: name the file either foo.rs or foo/mod.rs inside
the directory "src/bar"`. However, at on windows, the backslash was
double-escaped when naming the directory.
It did this because the string was printed in debug mode (`"{:?}"`) to
surround it with quotes. However, it should just be printed like any
other directory in an error message and surrounded by escaped quotes,
rather than relying on the debug print to add quotes (`"\"{}\""`).
I also checked the test suite to see if this output is being correctly tested. It's not - it only tests up to the word "directory". Presumably this is so that the test is not dependent on its exact position in the source tree. I don't know a better way to test this, unless the test suite supports regex?
When a module is declared, but no matching file exists, rustc gives
an error like 'help: name the file either foo.rs or foo/mod.rs inside
the directory "src/bar"'. However, at on windows, the backslash was
double-escaped when naming the directory.
It did this because the string was printed in debug mode ( "{:?}" ) to
surround it with quotes. However, it should just be printed like any
other directory in an error message and surrounded by escaped quotes,
rather than relying on the debug print to add quotes ( "\"{}\"" ).
libsyntax: Remove obsolete.rs
This little piece of infra is obsolete (ha-ha) and is unlikely to be used in the future, even if new obsolete syntax appears.
Vadim Petrochenkov