Panic when using mem::uninitialized or mem::zeroed on an uninhabited type
All code by @japaric. This re-submits one half of https://github.com/rust-lang/rust/pull/53508. This is likely not the one that introduced the perf regression, but just to be sure I'll do a perf run anyway.
This commit special cases the move out of borrowed content error,
previously:
```
error[E0507]: cannot move out of borrowed content
--> src/main.rs:7:10
|
7 | drop(x.field);
| ^ cannot move out of borrowed content
```
to instead mention that it is a move out of a `Rc`/`Arc` which is more
helpful:
```
error[E0507]: cannot move out of an `Rc`
--> src/main.rs:7:10
|
7 | drop(x.field);
| ^ cannot move out of an `Rc`
```
This commit introduces language items for `Arc` and `Rc` so that types
can later be checked to be `Arc` or `Rc` in the NLL borrow checker. The
`lang` attribute is currently limited to `stage1` as it requires a
compiler built with knowledge of the expected language items.
Rollup of 13 pull requests
Successful merges:
- #53784 (Document that slices cannot be larger than `isize::MAX` bytes)
- #54308 (Better user experience when attempting to call associated functions with dot notation)
- #54488 (in which we include attributes in unused `extern crate` suggestion spans)
- #54544 (Indicate how to move value out of Box in docs.)
- #54623 (Added help message for `impl_trait_in_bindings` feature gate)
- #54641 (A few cleanups and minor improvements to rustc/infer)
- #54656 (Correct doc for WorkQueue<T>::pop().)
- #54674 (update miri)
- #54676 (Remove `-Z disable_ast_check_for_mutation_in_guard`)
- #54679 (Improve bug! message for impossible case in Relate)
- #54681 (Rename sanitizer runtime libraries on OSX)
- #54708 (Make ./x.py help <cmd> invoke ./x.py <cmd> -h on its own)
- #54713 (Add nightly check for tool_lints warning)
Remove `-Z disable_ast_check_for_mutation_in_guard`
One should use `#![feature(bind_by_move_pattern_guards)]` over `-Z disable_ast_check_for_mutation_in_guard`
cc #15287
Rename sanitizer runtime libraries on OSX
Currently we ship sanitizer libraries as they're built, but these names
unfortunately conflict with the names of the sanitizer libraries
installed on the system. If a crate, for example, links in C code that
wants to use the system sanitizer and the Rust code doesn't use
sanitizers at all, then using `cargo` may accidentally pull in the
Rust-installed sanitizer library due to a conflict in names.
This change is intended to be entirely transparent for Rust users of
sanitizers, it should only hopefully improve our story with other users!
Closes#54134
Improve bug! message for impossible case in Relate
Hitting this branch [in Clippy][clippy_issue] and I think it makes sense to print
both values here in case other people hit this branch, too.
(still have to figure out why this branch is hit)
[clippy_issue]: https://github.com/rust-lang-nursery/rust-clippy/issues/2831#issuecomment-424597092
Correct doc for WorkQueue<T>::pop().
The old function doc looks like copy-pasta from WorkQueue::insert().
WorkQueue::pop() does not enqueue nor does it return a boolean false. Doc corrected accordingly.
A few cleanups and minor improvements to rustc/infer
- use unwrap_or(_else) where applicable
- convert single-branch matches to if-let
- use to_owned instead of to_string with string literals
- improve vector allocations
- readability improvements
- miscellaneous minor code improvements
rust: Add a `-C default-linker-libraries` option
This commit adds a new codegen option for the compiler which disables
rustc's passing of `-nodefaultlibs` by default on relevant platforms.
Sometimes Rust is linked with C code which fails to link with
`-nodefaultlibs` and is unnecessarily onerous to get linking correctly
with `-nodefaultlibs`.
An example of this is that when you compile C code with sanitizers and
then pass `-fsanitize=address` to the linker, it's incompatible with
`-nodefaultlibs` also being passed to the linker.
In these situations it's easiest to turn off Rust's default passing of
`-nodefaultlibs`, which was more ideological to start with than
anything! Preserving the default is somewhat important but having this
be opt-in shouldn't cause any breakage.
Closes#54237
Fix Once perf regression
Because `call_once` is generic, but `is_completed` is not, we need
`#[inline]` annotation to allow LLVM to inline `is_completed` into
`call_once` in downstream crates.
cc https://github.com/rust-lang/rust/pull/53027/files#r221418859
Don't lint non-extern-prelude extern crate's in Rust 2018.
Fixes#54381 by silencing the lint telling users to remove `extern crate` when `use` doesn't work.
r? @alexcrichton cc @petrochenkov @nikomatsakis @Centril
Add a per-tree error cache to the obligation forest
This implements part of what @nikomatsakis mentioned in https://github.com/rust-lang/rust/pull/30533#issuecomment-170705871:
> 1. If you find that a new obligation is a duplicate of one already in the tree, the proper processing is:
> * if that other location is your parent, you should abort with a cycle error (or accept it, if coinductive)
> * if that other location is not an ancestor, you can safely ignore the new obligation
In particular it implements the "if that other location is your parent accept it, if coinductive" part. This fixes#40827.
I have to say that I'm not 100% confident that this is rock solid. This is my first pull request 🎉, and I didn't know anything about the trait resolver before this. In particular I'm not totally sure that comparing predicates is enough (for instance, do we need to compare `param_env` as well?). Also, I'm not sure what @nikomatsakis mentions [here](https://github.com/rust-lang/rust/issues/30977#issue-127091096), but it might be something that affects this PR:
> In particular, I am wary of getting things wrong around inference variables! We can always add things to the set in their current state, and if unifications occur then the obligation is just kind of out-of-date, but I want to be sure we don't accidentally fail to notice that something is our ancestor. I decided this was subtle enough to merit its own PR.
Anyway, go ahead and review 🙂.
Ref #30977.
# Performance
We are now copying vectors around, so I decided to do some benchmarking. A simple benchmark shows that this does not seem to affect performance in a measurable way:
I ran `cargo clean && cargo build` 20 times on actix-web (84b27db) and these are the results:
```text
rustc master:
Mean Std.Dev. Min Median Max
real 66.637 2.996 57.220 67.714 69.314
user 307.293 14.741 258.093 312.209 320.702
sys 12.524 0.653 10.499 12.726 13.193
rustc fix-bug-overflow-send:
Mean Std.Dev. Min Median Max
real 66.297 4.310 53.532 67.516 70.348
user 306.812 22.371 236.917 314.748 326.229
sys 12.757 0.952 9.671 13.125 13.544
```
I will do a more comprehensive benchmark (compiling rustc stage1) and post the results.
r? @nikomatsakis, @nnethercote
PS: It is better to review this commit-by-commit.
