The rules for casting `*mut X<dyn A>` -> `*mut Y<dyn B>` are as follows:
- If `B` has a principal
- `A` must have exactly the same principal (including generics)
- Auto traits of `B` must be a subset of autotraits in `A`
Note that `X<_>` and `Y<_>` can be identity, or arbitrary structs with last field being the dyn type.
The lifetime of the trait object itself (`dyn ... + 'a`) is not checked.
This prevents a few soundness issues with `#![feature(arbitrary_self_types)]` and trait upcasting.
Namely, these checks make sure that vtable is always valid for the pointee.
Optimize SipHash by reordering compress instructions
This PR optimizes hashing by changing the order of instructions in the sip.rs `compress` macro so the CPU can parallelize it better. The new order is taken directly from Fig 2.1 in [the SipHash paper](https://eprint.iacr.org/2012/351.pdf) (but with the xors moved which makes it a little faster). I attempted to optimize it some more after this, but I think this might be the optimal instruction order. Note that this shouldn't change the behavior of hashing at all, only statements that don't depend on each other were reordered.
It appears like the current order hasn't changed since its [original implementation from 2012](fada46c421 (diff-b751133c229259d7099bbbc7835324e5504b91ab1aded9464f0c48cd22e5e420R35)) which doesn't look like it was written with data dependencies in mind.
Running `./x bench library/core --stage 0 --test-args hash` before and after this change shows the following results:
Before:
```
benchmarks:
hash::sip::bench_bytes_4 7.20/iter +/- 0.70
hash::sip::bench_bytes_7 9.01/iter +/- 0.35
hash::sip::bench_bytes_8 8.12/iter +/- 0.10
hash::sip::bench_bytes_a_16 10.07/iter +/- 0.44
hash::sip::bench_bytes_b_32 13.46/iter +/- 0.71
hash::sip::bench_bytes_c_128 37.75/iter +/- 0.48
hash::sip::bench_long_str 121.18/iter +/- 3.01
hash::sip::bench_str_of_8_bytes 11.20/iter +/- 0.25
hash::sip::bench_str_over_8_bytes 11.20/iter +/- 0.26
hash::sip::bench_str_under_8_bytes 9.89/iter +/- 0.59
hash::sip::bench_u32 9.57/iter +/- 0.44
hash::sip::bench_u32_keyed 6.97/iter +/- 0.10
hash::sip::bench_u64 8.63/iter +/- 0.07
```
After:
```
benchmarks:
hash::sip::bench_bytes_4 6.64/iter +/- 0.14
hash::sip::bench_bytes_7 8.19/iter +/- 0.07
hash::sip::bench_bytes_8 8.59/iter +/- 0.68
hash::sip::bench_bytes_a_16 9.73/iter +/- 0.49
hash::sip::bench_bytes_b_32 12.70/iter +/- 0.06
hash::sip::bench_bytes_c_128 32.38/iter +/- 0.20
hash::sip::bench_long_str 102.99/iter +/- 0.82
hash::sip::bench_str_of_8_bytes 10.71/iter +/- 0.21
hash::sip::bench_str_over_8_bytes 11.73/iter +/- 0.17
hash::sip::bench_str_under_8_bytes 10.33/iter +/- 0.41
hash::sip::bench_u32 10.41/iter +/- 0.29
hash::sip::bench_u32_keyed 9.50/iter +/- 0.30
hash::sip::bench_u64 8.44/iter +/- 1.09
```
I ran this on my computer so there's some noise, but you can tell at least `bench_long_str` is significantly faster (~18%).
Also, I noticed the same compress function from the library is used in the compiler as well, so I took the liberty of copy-pasting this change to there as well.
Thanks `@semisol` for porting SipHash for another project which led me to notice this issue in Rust, and for helping investigate. <3
rustdoc: update to pulldown-cmark 0.11
r? rustdoc
This pull request updates rustdoc to the latest version of pulldown-cmark. Along with adding new markdown extensions (which this PR doesn't enable), the new pulldown-cmark version also fixes a large number of bugs. Because all text files successfully parse as markdown, these bugfixes change the output, which can break people's existing docs.
A crater run, https://github.com/rust-lang/rust/pull/121659, has already been run for this change.
The first commit upgrades and fixes rustdoc. The second commit adds a lint for the footnote and block quote parser changes, which break the largest numbers of docs in the Crater run. The strikethrough change was mitigated in pulldown-cmark itself.
Unblocks https://github.com/rust-lang/rust-clippy/pull/12876
Fix incorrect suggestion for extra argument with a type error
Fixes#126246
I tried to fix it in the `find_errors` of ArgMatrix, but seems it's hard to avoid breaking some other test cases.
The root cause is we eliminate the first argument even with a type error at here:
6292b2af62/compiler/rustc_hir_typeck/src/fn_ctxt/checks.rs (L664)
So the left argument is always treated as extra one.
But if there is already a type error, an error message will be generated firstly, which make this issue a trivial one.
Make jump threading state sparse
Continuation of https://github.com/rust-lang/rust/pull/127024
Both dataflow const-prop and jump threading involve cloning the state vector a lot. This PR replaces the data structure by a sparse vector, considering:
- that jump threading state is typically very sparse (at most 1 or 2 set entries);
- that dataflow const-prop is disabled by default;
- that place/value map is very eager, and prone to creating an overly large state.
The first commit is shared with the previous PR to avoid needless conflicts.
r? `@oli-obk`
Remove global error count checks from typeck
Some of these are not reachable anymore, others can now rely on information local to the current typeck run. One check was actually invalid, because it was relying on wfcheck running before typeck, which is not guaranteed in the query system and usually easy to create ICEing examples for via const eval (which runs typeck before wfcheck)
Add `as_lang_item` to `LanguageItems`, new trait solver
Add `as_lang_item` which turns `DefId` into a `TraitSolverLangItem` in the new trait solver, so we can turn the large chain of if statements in `assemble_builtin_impl_candidates` into a match instead.
r? lcnr
linker: Link dylib crates by path
Linkers seem to support linking dynamic libraries by path.
Not sure why the previous scheme with splitting the path into a directory (passed with `-L`) and a name (passed with `-l`) was used (upd: likely due to https://github.com/rust-lang/rust/pull/126094#issuecomment-2155063414).
When we split a library path `some/dir/libfoo.so` into `-L some/dir` and `-l foo` we add `some/dir` to search directories for *all* libraries looked up by the linker, not just `foo`, and `foo` is also looked up in *all* search directories not just `some/dir`.
Technically we may find some unintended libraries this way.
Therefore linking dylibs via a full path is both simpler and more reliable.
It also makes the set of search directories more easily reproducible when we need to lookup some native library manually (like in https://github.com/rust-lang/rust/pull/123436).
Re-implement a type-size based limit
r? lcnr
This PR reintroduces the type length limit added in #37789, which was accidentally made practically useless by the caching changes to `Ty::walk` in #72412, which caused the `walk` function to no longer walk over identical elements.
Hitting this length limit is not fatal unless we are in codegen -- so it shouldn't affect passes like the mir inliner which creates potentially very large types (which we observed, for example, when the new trait solver compiles `itertools` in `--release` mode).
This also increases the type length limit from `1048576 == 2 ** 20` to `2 ** 24`, which covers all of the code that can be reached with craterbot-check. Individual crates can increase the length limit further if desired.
Perf regression is mild and I think we should accept it -- reinstating this limit is important for the new trait solver and to make sure we don't accidentally hit more type-size related regressions in the future.
Fixes#125460
Actually report normalization-based type errors correctly for alias-relate obligations in new solver
We have some special casing to report type mismatch errors that come from projection predicates, but we don't do that for alias-relate obligations. This PR implements that. There's a bit of code duplication, but 🤷
Best reviewed without whitespace.
r? lcnr
Check alias args for WF even if they have escaping bound vars
#### What
This PR stops skipping arguments of aliases if they have escaping bound vars, instead recursing into them and only discarding the resulting obligations referencing bounds vars.
#### An example:
From the test:
```
trait Trait {
type Gat<U: ?Sized>;
}
fn test<T>(f: for<'a> fn(<&'a T as Trait>::Gat<&'a [str]>)) where for<'a> &'a T: Trait {}
//~^ ERROR the size for values of type `[()]` cannot be known at compilation time
fn main() {}
```
We now prove that `str: Sized` in order for `&'a [str]` to be well-formed. We were previously unconditionally skipping over `&'a [str]` as it referenced a buond variable. We now recurse into it and instead only discard the `[str]: 'a` obligation because of the escaping bound vars.
#### Why?
This is a change that improves consistency about proving well-formedness earlier in the pipeline, which is necessary for future work on where-bounds in binders and correctly handling higher-ranked implied bounds. I don't expect this to fix any unsoundness.
#### What doesn't it fix?
Specifically, this doesn't check projection predicates' components are well-formed, because there are too many regressions: https://github.com/rust-lang/rust/pull/123737#issuecomment-2052198478
Since this codegen flag now only controls LLVM-generated comments rather than
all assembly comments, make the name more accurate (and also match Clang).
Rewrite handling of universe-leaking placeholder regions into outlives constraints
This commit prepares for Polonius by moving handling of leak check/universe errors out of the inference step by rewriting any universe error into an outlives-static constraint.
This variant is a work in progress but seems to pass most tests.
Note that a few debug assertions no longer hold; a few extra eyes on those changes are appreciated!
Fix `FnMut::call_mut`/`Fn::call` shim for async closures that capture references
I adjusted async closures to be able to implement `Fn` and `FnMut` *even if* they capture references, as long as those references did not need to borrow data from the closure captures themselves. See #125259.
However, when I did this, I didn't actually relax an assertion in the `build_construct_coroutine_by_move_shim` shim code, which builds the `Fn`/`FnMut`/`FnOnce` implementations for async closures. Therefore, if we actually tried to *call* `FnMut`/`Fn` on async closures, it would ICE.
This PR adjusts this assertion to ensure that we only capture immutable references in closures if they implement `Fn`/`FnMut`. It also adds a bunch of tests and makes more of the async-closure tests into `build-pass` since we often care about these tests actually generating the right closure shims and stuff. I think it might be excessive to *always* use build-pass here, but 🤷 it's not that big of a deal.
Fixes#127019Fixes#127012
r? oli-obk
Parenthesize break values containing leading label
The AST pretty printer previously produced invalid syntax in the case of `break` expressions with a value that begins with a loop or block label.
```rust
macro_rules! expr {
($e:expr) => {
$e
};
}
fn main() {
loop {
break expr!('a: loop { break 'a 1; } + 1);
};
}
```
`rustc -Zunpretty=expanded main.rs `:
```console
#![feature(prelude_import)]
#![no_std]
#[prelude_import]
use ::std::prelude::rust_2015::*;
#[macro_use]
extern crate std;
macro_rules! expr { ($e:expr) => { $e }; }
fn main() { loop { break 'a: loop { break 'a 1; } + 1; }; }
```
The expanded code is not valid Rust syntax. Printing invalid syntax is bad because it blocks `cargo expand` from being able to format the output as Rust syntax using rustfmt.
```console
error: parentheses are required around this expression to avoid confusion with a labeled break expression
--> <anon>:9:26
|
9 | fn main() { loop { break 'a: loop { break 'a 1; } + 1; }; }
| ^^^^^^^^^^^^^^^^^^^^^^^^
|
help: wrap the expression in parentheses
|
9 | fn main() { loop { break ('a: loop { break 'a 1; }) + 1; }; }
| + +
```
This PR updates the AST pretty-printer to insert parentheses around the value of a `break` expression as required to avoid this edge case.
And update the comment. Clearly the return type of this function was
changed at some point in the past, but its name and comment weren't
updated to match.
