Immutably and implicitly borrow all pattern ids for their guards (NLL only)
This is an important piece of rust-lang/rust#27282.
It applies only to NLL mode. It is a change to MIR codegen that is currently toggled on only when NLL is turned on. It thus affect MIR-borrowck but not the earlier static analyses (such as the type checker).
This change makes it so that any pattern bindings of type T for a match arm will map to a `&T` within the context of the guard expression for that arm, but will continue to map to a `T` in the context of the arm body.
To avoid surfacing this type distinction in the user source code (which would be a severe change to the language and would also require far more revision to the compiler internals), any occurrence of such an identifier in the guard expression will automatically get a deref op applied to it.
So an input like:
```rust
let place = (1, Foo::new());
match place {
(1, foo) if inspect(foo) => feed(foo),
...
}
```
will be treated as if it were really something like:
```rust
let place = (1, Foo::new());
match place {
(1, Foo { .. }) if { let tmp1 = &place.1; inspect(*tmp1) }
=> { let tmp2 = place.1; feed(tmp2) },
...
}
```
And an input like:
```rust
let place = (2, Foo::new());
match place {
(2, ref mut foo) if inspect(foo) => feed(foo),
...
}
```
will be treated as if it were really something like:
```rust
let place = (2, Foo::new());
match place {
(2, Foo { .. }) if { let tmp1 = & &mut place.1; inspect(*tmp1) }
=> { let tmp2 = &mut place.1; feed(tmp2) },
...
}
```
In short, any pattern binding will always look like *some* kind of `&T` within the guard at least in terms of how the MIR-borrowck views it, and this will ensure that guard expressions cannot mutate their the match inputs via such bindings. (It also ensures that guard expressions can at most *copy* values from such bindings; non-Copy things cannot be moved via these pattern bindings in guard expressions, since one cannot move out of a `&T`.)
Remove the deprecated std::net::{lookup_host,LookupHost}
These are unstable, and were deprecated by #47510, since Rust 1.25. The
internal `sys` implementations are still kept to support the call in the
common `resolve_socket_addr`.
nano-optimization for memchr::repeat_byte
This replaces the multiple shifts & bitwise or with a single multiplication
In my benchmarks this performs equally well or better, especially on 64bit systems (it shaves a stable nanosecond on my skylake). This may go against conventional wisdom, but the shifts and bitwise ors cannot be pipelined because of hard data dependencies.
While it may or may not be worthwile from an optimization standpoint, it also reduces code size, so there's basically no downside.
Update RLS and Rustfmt (and Cargo)
Updates RLS and Rustfmt (the latter fixing tests). Cargo is updated too (to fix RLS tests), but that is covered by https://github.com/rust-lang/rust/pull/50417, so probably won't do much.
r? @alexcrichton
Refactorings in preparation for the removal of the leak check
This contains all of the commits from #48407 that I was able to pull out on their own. This has most of the refactoring/ground work to unblock other work, but without the behavior changes that still need a crater run and NLL changes.
r? @nikomatsakis
These are unstable, and were deprecated by #47510, since Rust 1.25. The
internal `sys` implementations are still kept to support the call in the
common `resolve_socket_addr`.
Rollup of 12 pull requests
Successful merges:
- #50302 (Add query search order check)
- #50320 (Fix invalid path generation in rustdoc search)
- #50349 (Rename "show type declaration" to "show declaration")
- #50360 (Clarify wordings of the `unstable_name_collision` lint.)
- #50365 (Use two vectors in nearest_common_ancestor.)
- #50393 (Allow unaligned reads in constants)
- #50401 (Revert "Implement FromStr for PathBuf")
- #50406 (Forbid constructing empty identifiers from concat_idents)
- #50407 (Always inline simple BytePos and CharPos methods.)
- #50416 (check if the token is a lifetime before parsing)
- #50417 (Update Cargo)
- #50421 (Fix ICE when using a..=b in a closure.)
Failed merges:
Forbid constructing empty identifiers from concat_idents
The empty identifier is a [reserved identifier](8a37c75a3a/src/libsyntax_pos/symbol.rs (L300-L305)) in rust, apparently used for black magicks like representing the crate root or somesuch... and therefore, being able to construct it is Ungood. Presumably.
...even if the macro that lets you construct it is so useless that you can't actually do any damage with it. (and believe me, I tried)
Fixes#50403.
**Note:** I noticed that when you try to do something similar with `proc_macro::Term`, the compiler actually catches it and flags the identifier as reserved. Perhaps a better solution would be to somehow have that same check applied here.
Revert "Implement FromStr for PathBuf"
This reverts commit 05a9acc3b8.
The libs team was discussing https://github.com/rust-lang/rust/issues/44431 today and the changes originally added in https://github.com/rust-lang/rust/pull/48292 and the conclusion was that we'd like to revert this for now until `!` is stable. This'll provide us maximal flexibility to tweak the error type here in the future, and it looks like `!` is close-ish to stabilization so hopefully this won't be delayed for too long.
Use two vectors in nearest_common_ancestor.
When looking at any scope in scope chain A, we only need to look for
matches among scopes previously seen in scope chain B, and vice versa.
This halves the number of "seen before?" comparisons, speeding up some
runs of style-servo, clap-rs, and syn by 1--2%.
Thanks to @kirillkh for the suggestion.
r? @nikomatsakis
`cmt` is a ref-counted wrapper around `cmt_` The use of refcounting
keeps `cmt` handling simple, but a lot of `cmt` instances are very
short-lived, and heap-allocating the short-lived ones takes up time.
This patch changes things in the following ways.
- Most of the functions that produced `cmt` instances now produce `cmt_`
instances. The `Rc::new` calls that occurred within those functions
now occur at their call sites (but only when necessary, which isn't
that often).
- Many of the functions that took `cmt` arguments now take `&cmt_`
arguments. This includes all the methods in the `Delegate` trait.
As a result, the vast majority of the heap allocations are avoided. In
an extreme case, the number of calls to malloc in tuple-stress drops
from 9.9M to 7.9M, a drop of 20%. And the compile times for many runs of
coercions, deep-vector, and tuple-stress drop by 1--2%.
guard expressions of matches (activated only when using
new NLL mode).
Review feedback: removed 27282 from filename. (The test still
references it in a relevant comment in the file itself so that seemed
like a reasonable compromise.)
deref'ing such borrows within that guard.
Review feedback: Add comment noting a point where we may or may not
need to add a cast when we finish the work on rust-lang/rust#27282.
Review feedback: Pass a newtype'd `ArmHasGuard` rather than a raw boolean.
Review feedback: toggle "ref binding in guards" semantics via specific
method. (This should ease a follow-up PR that just unconditionally
adopts the new semantics.)
Implement tool_attributes feature (RFC 2103)
cc #44690
This is currently just a rebased and compiling (hopefully) version of #47773.
Let's see if travis likes this. I will add the implementation for `tool_lints` this week.
