Where this is relevant: trait objects! Inside a `#![no_std]` library it's otherwise impossible to have a struct holding a trait object, and at the same time can be used from downstream std crates in a way that doesn't interfere with catch_unwind.
fn main() {
let thing: library::Thing = ...;
let _ = std::panic::catch_unwind(|| { let _ = thing; }); // does not work :(
}
```
See https://github.com/dtolnay/colorous/blob/a4131708e2f05d2377964981896ff62dbc9b027b/src/gradient.rs#L7-L15 for a real life example of needing to work around this problem. In particular that workaround would not even be viable if implementors of the trait were provided externally by a caller, as the `feature = "std"` would become non-additive in that case.
What happens without the UnwindSafe constraints:
```rust
fn main() {
let gradient = colorous::VIRIDIS;
let _ = std::panic::catch_unwind(|| { let _ = gradient; });
}
```
```console
error[E0277]: the type `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
--> src/main.rs:3:13
|
3 | let _ = std::panic::catch_unwind(|| { let _ = gradient; });
| ^^^^^^^^^^^^^^^^^^^^^^^^ `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)` may contain interior mutability and a reference may not be safely transferrable across a catch_unwind boundary
|
::: .rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/library/std/src/panic.rs:430:40
|
430 | pub fn catch_unwind<F: FnOnce() -> R + UnwindSafe, R>(f: F) -> Result<R> {
| ---------- required by this bound in `catch_unwind`
|
= help: within `Gradient`, the trait `RefUnwindSafe` is not implemented for `(dyn colorous::gradient::EvalGradient + Send + Sync + 'static)`
= note: required because it appears within the type `&'static (dyn colorous::gradient::EvalGradient + Send + Sync + 'static)`
= note: required because it appears within the type `Gradient`
= note: required because of the requirements on the impl of `UnwindSafe` for `&Gradient`
= note: required because it appears within the type `[closure@src/main.rs:3:38: 3:62]`
```
bors [Sun, 1 Aug 2021 00:12:18 +0000 (00:12 +0000)]
Auto merge of #85782 - badboy:build-ios-sim-target, r=Mark-Simulacrum
Build aarch64-apple-ios-sim as part of the full macOS build
Part of the [MCP 428](https://github.com/rust-lang/compiler-team/issues/428) to promote this target to Tier 2.
This adds the aarch64-apple-ios-sim target as a tier 2 target, currently cross-compiled from our x86_64 apple builders. The compiler team has approved the addition per the MCP noted above, and the infrastructure team has not raised concerns with this addition at this time (as the CI time impact is expected to be minimal; this is only building std).
Auto merge of #87662 - FabianWolff:rb-string, r=estebank
Suggest `br` if the unknown string prefix `rb` is found
Currently, for the following code:
```rust
fn main() {
rb"abc";
}
```
we issue the following suggestion:
```
help: consider inserting whitespace here
|
2 | rb "abc";
| --
```
With my changes (only in edition 2021, where unknown prefixes became an error), I get:
```
help: use `br` for a raw byte string
|
2 | br"abc";
| ^^
```
Auto merge of #86264 - crlf0710:trait_upcasting_part1, r=nikomatsakis
Trait upcasting coercion (part1)
This revives the first part of earlier PR #60900 .
It's not very clear to me which parts of that pr was design decisions, so i decide to cut it into pieces and land them incrementally. This allows more eyes on the details.
This is the first part, it adds feature gates, adds feature gates tests, and implemented the unsize conversion part.
(I hope i have dealt with the `ExistentialTraitRef` values correctly...)
The next part will be implementing the pointer casting.
Auto merge of #87387 - the8472:slice-iter-advance_by, r=scottmcm
Implement advance_by, advance_back_by for slice::{Iter, IterMut}
Part of #77404.
Picking up where #77633 was closed.
I have addressed https://github.com/rust-lang/rust/pull/77633#issuecomment-771842599 by restoring `nth` and `nth_back`. So according to that comment this should already be r=m-ou-se, but it has been sitting for a while.
Auto merge of #87640 - JohnTitor:rollup-yq24nq5, r=JohnTitor
Rollup of 9 pull requests
Successful merges:
- #86072 (Cross compiling rustc_llvm on Darwin requires zlib.)
- #87385 (Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default)
- #87547 (Add missing examples for NonNull)
- #87557 (Fix issue with autofix for ambiguous associated function from Rust 2021 prelude when struct is generic)
- #87559 (Tweak borrowing suggestion in `for` loop)
- #87596 (Add warning when whitespace is not skipped after an escaped newline)
- #87606 (Add some TAIT-related regression tests)
- #87609 (Add docs about performance and `Iterator::map` to `[T; N]::map`)
- #87616 (Fix missing word in rustdoc book)
My *guess* is that this gets the attention it gets because in JavaScript
(and potentially other languages), a `map` function on arrays is very
commonly used since in those languages, arrays basically take the role
of Rust's iterator. I considered explicitly naming JavaScript in the
first paragraph I added, but I couldn't find precedence of mentioning
other languages in standard library doc, so I didn't add it.
When array::map was stabilized, we still wanted to add docs, but that
somehow did not happen in time. So here we are. Not sure if this sounds
crazy but maybe it is worth considering beta backporting this? Only if
it's not a lot of work, of course! But yeah, stabilized array::map is
already in beta and if this problem is really as big as it sometimes seems,
might be worth having the docs in place when 1.55 is released.
CC ``@CryZe``
r? ``@m-ou-se`` (since you were involved in that discussion and the stabilization)
Rollup merge of #87596 - jesyspa:issue-87318-hidden-whitespace, r=estebank
Add warning when whitespace is not skipped after an escaped newline
Fixes issue #87318, also simplifies issue #87319.
* Add support to the lexer to emit warnings as well as errors.
* Emit a warning when a string literal contains an escaped newline, but when (some of) the whitespace on the next line is not skipped due to it being non-ASCII.
Rollup merge of #87557 - rylev:fix-invalid-prelude-collision-error, r=nikomatsakis
Fix issue with autofix for ambiguous associated function from Rust 2021 prelude when struct is generic
Fixes #86940
The test cases and associated issue should make it clear what specifically this is meant to fix. The fix is slightly hacky in that we check against the literal source code of the call site for the presence of `<` in order to determine if the user has included the generics for the struct (meaning we don't need to include them for them).
Rollup merge of #87385 - Aaron1011:final-enable-semi, r=petrochenkov
Make `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` warn by default
This PR makes the `SEMICOLON_IN_EXPRESSIONS_FROM_MACROS` lint warn by default.
To avoid showing a large number of un-actionable warnings to users, we only enable the lint for macros defined in the same crate. This ensures that users will be able to fix the warning by simply removing a semicolon.
In the future, I'd like to enable this lint unconditionally, and eventually make it into a hard error in a future edition. This PR is a step towards that goal.
Auto merge of #85971 - FabianWolff:issue-85586, r=davidtwco
Use more precise span for E0282 in cast expressions
This pull request fixes #85586. The example code given there:
```rust
fn main() {
let a = [1, 2, 3].iter().sum();
let b = (a + 1) as usize;
}
```
currently produces
```
error[E0282]: type annotations needed
--> issue-85586.rs:3:13
|
3 | let b = (a + 1) as usize;
| ^^^^^^^^^^^^^^^^ cannot infer type
|
= note: type must be known at this point
error: aborting due to previous error
```
even though the type of the entire cast expression quite clearly should be `usize`. The error is in the cast's left-hand side, which is made explicit by the changes in this PR:
```
error[E0282]: type annotations needed
--> issue-85586.rs:3:13
|
3 | let b = (a + 1) as usize;
| ^^^^^^^ cannot infer type
|
= note: type must be known at this point
Auto merge of #87237 - jonas-schievink:const-for-and-try, r=oli-obk
Add feature gates for `for` and `?` in consts
These operations seems *relatively* straightforward to support, and only seem to be blocked on `impl const Trait`.
I have included a working test for `const_try`, but `const_for` is currently unusable without reimplementing *every single* defaulted `Iterator` method, so I didn't do that.
(both features still need tracking issues before this is merged)
Auto merge of #87615 - JohnTitor:rollup-t5jpmrg, r=JohnTitor
Rollup of 10 pull requests
Successful merges:
- #87052 (Optimize fmt::PadAdapter::wrap)
- #87522 (Fix assert in diy_float)
- #87553 (Fix typo in rustc_driver::version)
- #87554 (2229: Discr should be read when PatKind is Range)
- #87564 (min_type_alias_impl_trait is going to be removed in 1.56)
- #87574 (Update the examples in `String` and `VecDeque::retain`)
- #87583 (Refactor compression cache in v0 symbol mangler)
- #87585 (Add missing links for core::char types)
- #87594 (fs File get_path procfs usage for netbsd same as linux.)
- #87602 ([backtraces]: look for the `begin` symbol only after seeing `end`)
Notice that `__rust_begin_short_backtrace` appears on frame 11 before
`__rust_end_short_backtrace` on frame 12. This is because in typical
release binaries without debug symbols, dbghelp.dll, which we use to walk
and symbolize the stack, does not know where CGU internal functions
start or end and so the closure invoked by `__rust_end_short_backtrace`
is incorrectly described as `__rust_begin_short_backtrace` because it
happens to be near that symbol.
While that can obviously change, this has been happening quite
consistently since #75048. Since this is a very small change to the std
and the change makes sense by itself, I think this is worth doing.
This doesn't completely resolve the situation for release binaries on
Windows, since without debug symbols, the stack printed can still show
incorrect symbol names (this is why the test uses `#[no_mangle]`) but it
does slightly improve the situation in that you see the same backtrace
you would see with `RUST_BACKTRACE=full` or in a debugger (without the
uninteresting bits at the top and bottom).
Rollup merge of #87583 - tmiasko:compression-cache, r=wesleywiser
Refactor compression cache in v0 symbol mangler
* Remove redundant option around compression caches (they are always present).
* Flatten compression caches into symbol mangler to avoid dynamic memory allocation.
* Implement printer for `&mut SymbolMangler` instead of `SymbolMangler` to avoid passing now slightly larger symbol mangler by value.
Rollup merge of #87574 - cuviper:retain-examples, r=joshtriplett
Update the examples in `String` and `VecDeque::retain`
The examples added in #60396 used a "clever" post-increment hack,
unrelated to the actual point of the examples. That hack was found
[confusing] in the users forum, and #81811 already changed the `Vec`
example to use a more direct iterator. This commit changes `String` and
`VecDeque` in the same way for consistency.
Rollup merge of #87564 - spastorino:adjust-min-tait-removed-version, r=jackh726
min_type_alias_impl_trait is going to be removed in 1.56
#87501 removed `min_type_alias_impl_trait` but meanwhile that PR was approved in homu queue, a new beta was cut so we need to bump the version because it won't be removed in 1.55.
Rollup merge of #87052 - phlopsi:patch-1, r=jyn514
Optimize fmt::PadAdapter::wrap
After adding the first `write!` usage to my project and printing the result to the console, I noticed, that my binary contains the strings "called `Option::unwrap()` on a `None` value`" and more importantly "C:\Users\Patrick Fischer\.rustup\toolchains\nightly-x86_64-pc-windows-msvc\lib\rustlib\src\rust\library\core\src\fmt\builders.rs", with my release build being configured as follows:
```
[profile.release]
panic = "abort"
codegen-units = 1
strip = "symbols" # the important bit
lto = true
```
I am in a no_std environment and my custom panic handler is a simple `loop {}`. I did not expect the above information to be preserved. I heavily suspect the edited function to be the culprit. It contains the only direct use of `Option::unwrap` in the entire file and I tracked the symbols in the assembly to be used from the section `_ZN68_$LT$core..fmt..builders..PadAdapter$u20$as$u20$core..fmt..Write$GT$9write_str17ha1d5e5efe167202aE`.
Aside from me suspecting this function to be the culprit, the replaced code performs the same operation as `Option::insert`, but without the `unreachable_unchecked` optimization `Option::insert` provides. Therefore, it makes sense to me to use the more optimized version, instead.
As I don't change any semantics, I hope a simple pull request suffices.
Mir borrowck does not generate lifetime variables for 'static lifetimes during opaque type resolution
Fixes #87455
This situation was unreachable before #87287 as we used to just grab the resolved opaque type from typeck and replaced all regions with new inference vars. After #87287 we let the `InferCx` in mir borrowck figure out the opaque type all by itself (which it already did before, but it only used the result to sanity check with the typeck result).
Auto merge of #87285 - GuillaumeGomez:intra-doc-span, r=estebank
Improve intra doc errors display
#87169
`@jyn514` This is what I had in mind to avoid having duplicated backticks. I also gave a try to simply updating the span for the suggestion/help messages but I think this current one is better because less "noisy". Anyway, that allows you to see the result. ;)
Auto merge of #85901 - ijackson:bufwriter-tweaks, r=joshtriplett
Bufwriter disassembly tweaks
In #80690 `@BurntSushi` observed that `WriterPanicked` was erroneously not exported, and suggested renaming `into_raw_parts` to `into_parts`. (More info in my commit messages.)
Notice that `__rust_begin_short_backtrace` appears on frame 11 before
`__rust_end_short_backtrace` on frame 12. This is because in typical
release binaries without debug symbols, dbghelp.dll, which we use to walk
and symbolize the stack, does not know where CGU internal functions
start or end and so the closure invoked by `__rust_end_short_backtrace`
is incorrectly described as `__rust_begin_short_backtrace` because it
happens to be near that symbol.
While that can obviously change, this has been happening quite
consistently since #75048. Since this is a very small change to the std
and the change makes sense by itself, I think this is worth doing.
This doesn't completely resolve the situation for release binaries on
Windows, since without debug symbols, the stack printed can still show
incorrect symbol names (this is why the test uses `#[no_mangle]`) but it
does slightly improve the situation in that you see the same backtrace
you would see with `RUST_BACKTRACE=full` or in a debugger (without the
uninteresting bits at the top and bottom).
Ian Jackson [Tue, 1 Jun 2021 15:47:26 +0000 (16:47 +0100)]
BufWriter: rename `into_parts` from `into_raw_parts`
I looked in stdlib and as @BurntSushi thought, `raw` is generally
used for raw pointers, or other hazardous kinds of thing. stdlib does
not have `into_parts` apart from the one I added to `IntoInnerError`.
I did an ad-hoc search of the rustdocs for my current game project
Otter, which includes quite a large number of dependencies.
`into_parts` seems heavily used for things quite like this.
So change this name.
Suggested-by: Andrew Gallant <jamslam@gmail.com> Signed-off-by: Ian Jackson <ijackson@chiark.greenend.org.uk>
Tomasz Miąsko [Thu, 29 Jul 2021 00:00:00 +0000 (00:00 +0000)]
Flatten compression caches into symbol mangler
The compression caches currently don't have any dedicated functionality
that would benefit from being separated. Incorporating caches directly
into the symbol manger also avoids dynamic memory allocation.
The symbol mangler, which is often passed by value, is now slightly
larger. This aspect will be addressed by a follow-up commit.
Auto merge of #86664 - m-ou-se:uninit-track-caller, r=JohnTitor
Add #[track_caller] for some function in core::mem.
These functions can panic for some types. This makes the panic point to the code that calls e.g. mem::uninitialized(), instead of inside the definition of mem::uninitialized.
Auto merge of #86998 - m-ou-se:const-panic-fmt-as-str, r=oli-obk
Make const panic!("..") work in Rust 2021.
During const eval, this replaces calls to core::panicking::panic_fmt and std::panicking::being_panic_fmt with a call to a new const fn: core::panicking::const_panic_fmt. That function uses fmt::Arguments::as_str() to get the str and calls panic_str with that instead.
panic!() invocations with formatting arguments are still not accepted, as the creation of such a fmt::Arguments cannot be done in constant functions right now.
Auto merge of #87416 - Aaron1011:query-side-effect, r=cjgillot
Create `QuerySideEffects` and use it for diagnostics
The code for saving and loading diagnostics during execution is generalized to handle a new `QuerySideEffects` struct. Currently, this struct just holds diagnostics - in a follow-up PR, I plan to add support for storing attriutes marked as used during query execution.
This is a pure refactor, with no intended behavior changes.
Removes the implementations that depend on the user-definable trait `Copy`.
Fixes #85873 in the most straightforward way.
<hr>
_Edit:_ This PR now contains additional trait infrastructure to avoid performance regressions around in-place collect, see the discussion in this thread starting from the codegen test failure at https://github.com/rust-lang/rust/pull/85874#issuecomment-872327577.
With this PR, `TrustedRandomAccess` gains additional documentation that specifically allows for and specifies the safety conditions around subtype coercions – those coercions can happen in safe Rust code with the `Zip` API’s usage of `TrustedRandomAccess`. This PR introduces a new supertrait of `TrustedRandomAccess`(currently named `TrustedRandomAccessNoCoerce`) that _doesn’t allow_ such coercions, which means it can be still be useful for optimizing cases such as in-place collect where no iterator is handed out to a user (who could do coercions) after a `get_unchecked` call; the benefit of the supertrait is that it doesn’t come with the additional safety conditions around supertraits either, so it can be implemented for more types than `TrustedRandomAccess`.
The `TrustedRandomAccess` implementations for `vec::IntoIter`, `vec_deque::IntoIter`, and `array::IntoIter` are removed as they don’t conform with the newly documented safety conditions, this way unsoundness is removed. But this PR in turn (re-)adds a `TrustedRandomAccessNoCoerce` implementation for `vec::IntoIter` to avoid performance regressions from stable in a case of in-place collecting of `Vec`s [the above-mentioned codegen test failure]. Re-introducing the (currently nightly+beta-only) impls for `VecDeque`’s and `[T; N]`’s iterators is technically possible, but goes beyond the scope of this PR (i.e. it can happen in a future PR).
Josh Stone [Wed, 28 Jul 2021 23:35:59 +0000 (16:35 -0700)]
Update the examples in `String` and `VecDeque::retain`
The examples added in #60396 used a "clever" post-increment hack,
unrelated to the actual point of the examples. That hack was found
[confusing] in the users forum, and #81811 already changed the `Vec`
example to use a more direct iterator. This commit changes `String` and
`VecDeque` in the same way for consistency.
Auto merge of #87569 - JohnTitor:rollup-7ydfetw, r=JohnTitor
Rollup of 10 pull requests
Successful merges:
- #81050 (Stabilize core::task::ready!)
- #81363 (Remove P: Unpin bound on impl Future for Pin)
- #86839 (Add doc aliases to fs.rs)
- #87435 (fix example code for E0617)
- #87451 (Add support for tuple struct field documentation)
- #87491 (Integrate context into the memorial to Anna)
- #87521 (Add long explanation for E0498)
- #87527 (Don't run MIR unsafeck at all when using `-Zthir-unsafeck`)
- #87550 (Add `CI_ONLY_WHEN_CHANNEL` and run `x86_64-gnu-stable` only on nightly)
- #87565 (Use backticks when referring to `core::future::Ready` in panic message)