Upgrade to LLVM 16
This updates Rust to LLVM 16. It also updates our host compiler for dist-x86_64-linux to LLVM 16. The reason for that is that Bolt from LLVM 15 is not capable of compiling LLVM 16 (https://github.com/llvm/llvm-project/issues/61114).
LLVM 16.0.0 has been [released](https://discourse.llvm.org/t/llvm-16-0-0-release/69326) on March 18, while Rust 1.70 will become stable on June 1.
Tested images: `dist-x86_64-linux`, `dist-riscv64-linux` (alt), `dist-x86_64-illumos`, `dist-various-1`, `dist-various-2`, `dist-powerpc-linux`, `wasm32`, `armhf-gnu`
Tested images until the usual IPv6 failures: `test-various`
Update host compiler to LLVM 16
Update the host compiler for dist-x86_64-linux to LLVM 16. In particular, this pulls in 1de305da42, which is needed to update Rust's own LLVM (https://github.com/rust-lang/rust/pull/107224).
Tweak implementation of overflow checking assertions
Extract and reuse logic controlling behaviour of overflow checking assertions instead of duplicating it three times.
r? `@cjgillot`
Previously, it would walk each directory twice: once in the main `Walk`
iterator, and once to count the number of entries in the directory. Now
it only walks each directory once.
- Skip files in `skip` wherever possible to avoid reading their contents
- Don't look for `tidy-alphabetic-start` in tests. It's never currently used and slows the check down a lot.
- Add new `filter_not_rust` helper function
Fix invalid markdown link references
Fixes invalid link references in librustdoc's template documentation.
`[text](link)` was interpreted as a relative path to the file, making the link invalid, while `[text][label]` references a label defined in the file itself: <https://www.markdownguide.org/basic-syntax/#reference-style-links>
Install projection from RPITIT to default trait method opaque correctly
1. For new lowering strategy `-Zlower-impl-trait-in-trait-to-assoc-ty`, install the correct default trait method projection predicates (RPITIT -> opaque). This makes default trait body tests pass!
2. Fix two WF-checking bugs -- first, we want to make sure that we're always looking for an opaque type in `check_return_position_impl_trait_in_trait_bounds`. That's because the RPITIT projections are normalized to opaques during wfcheck. Second, fix RPITIT's param-envs by not adding the projection predicates that we install on trait methods to make default RPITITs work -- I left a comment why.
3. Also, just a small drive-by for `rustc_on_unimplemented`. Not sure if it affects any tests, but can't hurt.
r? ````@spastorino,```` based off of #109140
Prevent stable `libtest` from supporting `-Zunstable-options`
Took a while for me to get around to this but seems trivial (unless I'm missing some reason this will break all our tests). Fixes#75526
Basically `libtest` already tries to handle this in 501ad021b9/library/test/src/cli.rs (L310-L318)
But that env var was not passed. I'm guessing at one point [this code](501ad021b9/src/bootstrap/compile.rs (L842-L844)) (or a common ancestor) was used to compile the standard library/libtest, but that is no longer the case (or perhaps it never worked, I don't have time to go digging).
I don't love that this is a "allow unstable by default" situation, as it means things like [`rustc-build-sysroot`](https://github.com/RalfJung/rustc-build-sysroot) could accidentally get unstable (CC ````@RalfJung)```` even if this is fixed here, but it's consistent with what happens in `rustc_feature`, so... yeah.
This is user-facing after all, even if it's hard to imagine the outcome of that conversation being "lets continue allowing use of `-Zunstable-features` from stable rust" (especially since a `RUSTC_BOOTSTRAP=1`-shaped loophole remains)... I think it probably should get a vibe check in the t-libs meeting (and plausibly a relnote along the lines of "hey `cargo test -- -Zunstable-options --some --unstable --stuff=here` used to work on stable, that's been fixed, sorry").
I'll nominate it for that after CI comes up green (I've done a smoke check but don't know what (if anything) will need `bootstrap` to enable `RUSTC_BOOTSTRAP=1` when running tests)
r? ````@jyn514````
Remove box expressions from HIR
After #108516, `#[rustc_box]` is used at HIR->THIR lowering and this is no longer emitted, so it can be removed.
This is based on top of #108471 to help with conflicts, so 43490488ccacd1a822e9c621f5ed6fca99959a0b is the only relevant commit (sorry for all the duplicated pings!)
````@rustbot```` label +S-blocked
Flatten/inline format_args!() and (string and int) literal arguments into format_args!()
Implements https://github.com/rust-lang/rust/issues/78356
Gated behind `-Zflatten-format-args=yes`.
Part of #99012
This change inlines string literals, integer literals and nested format_args!() into format_args!() during ast lowering, making all of the following pairs result in equivalent hir:
```rust
println!("Hello, {}!", "World");
println!("Hello, World!");
```
```rust
println!("[info] {}", format_args!("error"));
println!("[info] error");
```
```rust
println!("[{}] {}", status, format_args!("error: {}", msg));
println!("[{}] error: {}", status, msg);
```
```rust
println!("{} + {} = {}", 1, 2, 1 + 2);
println!("1 + 2 = {}", 1 + 2);
```
And so on.
This is useful for macros. E.g. a `log::info!()` macro could just pass the tokens from the user directly into a `format_args!()` that gets efficiently flattened/inlined into a `format_args!("info: {}")`.
It also means that `dbg!(x)` will have its file, line, and expression name inlined:
```rust
eprintln!("[{}:{}] {} = {:#?}", file!(), line!(), stringify!(x), x); // before
eprintln!("[example.rs:1] x = {:#?}", x); // after
```
Which can be nice in some cases, but also means a lot more unique static strings than before if dbg!() is used a lot.
make `define_opaque_types` fully explicit
based on the idea of #108389. Moved `define_opaque_types` into the actual operations, e.g. `eq`, instead of `infcx.at` because normalization doesn't use `define_opaque_types` and even creates it's own `At` with a different `define_opaque_types` internally.
Somewhat surprisingly, coherence actually relies on `DefineOpaqueTypes::Yes` for soundness which was revealed because I've incorrectly used `DefineOpaqueTypes::No` in `equate_impl_headers`. It feels concerning that even though this is the case, we still sometimes use `DefineOpaqueTypes::No` in coherence. I did not look into this as part of this PR as it is purely changing the structure of the code without changing behavior in any way.
r? ```@oli-obk```
rustdoc: DocFS: Replace rayon with threadpool and enable it for all targets
Fixes https://github.com/rust-lang/rust/issues/109060.
Switching to `threadpool` makes it a bit simpler for us to wait for all tasks in `DocFS` directly in the `Drop` implementation. I'm also curious if making all the writes into a thread pool could improve run time for rustdoc on all other platforms than Windows as well.
I'll run a perf check to see.
cc ```@ehuss```
r? ```@notriddle```
