Add "algebraic" fast-math intrinsics, based on fast-math ops that cannot return poison
Setting all of LLVM's fast-math flags makes our fast-math intrinsics very dangerous, because some inputs are UB. This set of flags permits common algebraic transformations, but according to the [LangRef](https://llvm.org/docs/LangRef.html#fastmath), only the flags `nnan` (no nans) and `ninf` (no infs) can produce poison.
And this uses the algebraic float ops to fix https://github.com/rust-lang/rust/issues/120720
cc `@orlp`
macro_rules: Preserve all metavariable spans in a global side table
This PR preserves spans of `tt` metavariables used to pass tokens to declarative macros.
Such metavariable spans can then be used in span combination operations like `Span::to` to improve all kinds of diagnostics.
Spans of non-`tt` metavariables are currently kept in nonterminal tokens, but the long term plan is remove all nonterminal tokens from rustc parser and rely on the proc macro model with invisible delimiters (#114647, #67062).
In particular, `NtIdent` nonterminal (corresponding to `ident` metavariables) becomes easy to remove when this PR lands (#119412 does it).
The metavariable spans are kept in a global side table keyed by `Span`s of original tokens.
The alternative to the side table is keeping them in `SpanData` instead, but the performance regressions would be large because any spans from tokens passed to declarative macros would stop being inline and would work through span interner instead, and the penalty would be paid even if we never use the metavar span for the given original span.
(But also see the comment on `fn maybe_use_metavar_location` describing the map collision issues with the side table approach.)
There are also other alternatives - keeping the metavar span in `Token` or `TokenTree`, but associating it with `Span` itsel is the most natural choice because metavar spans are used in span combining operations, and those operations are not necessarily tied to tokens.
fixes#117448
For example unnecessary imports in std::prelude that can be eliminated:
```rust
use std::option::Option::Some;//~ WARNING the item `Some` is imported redundantly
use std::option::Option::None; //~ WARNING the item `None` is imported redundantly
```
Implement intrinsics with fallback bodies
fixes#93145 (though we can port many more intrinsics)
cc #63585
The way this works is that the backend logic for generating custom code for intrinsics has been made fallible. The only failure path is "this intrinsic is unknown". The `Instance` (that was `InstanceDef::Intrinsic`) then gets converted to `InstanceDef::Item`, which represents the fallback body. A regular function call to that body is then codegenned. This is currently implemented for
* codegen_ssa (so llvm and gcc)
* codegen_cranelift
other backends will need to adjust, but they can just keep doing what they were doing if they prefer (though adding new intrinsics to the compiler will then require them to implement them, instead of getting the fallback body).
cc `@scottmcm` `@WaffleLapkin`
### todo
* [ ] miri support
* [x] default intrinsic name to name of function instead of requiring it to be specified in attribute
* [x] make sure that the bodies are always available (must be collected for metadata)
Rollup of 11 pull requests
Successful merges:
- #120765 (Reorder diagnostics API)
- #120833 (More internal emit diagnostics cleanups)
- #120899 (Gracefully handle non-WF alias in `assemble_alias_bound_candidates_recur`)
- #120917 (Remove a bunch of dead parameters in functions)
- #120928 (Add test for recently fixed issue)
- #120933 (check_consts: fix duplicate errors, make importance consistent)
- #120936 (improve `btree_cursors` functions documentation)
- #120944 (Check that the ABI of the instance we are inlining is correct)
- #120956 (Clean inlined type alias with correct param-env)
- #120962 (Add myself to library/std review)
- #120972 (fix ICE for deref coercions with type errors)
r? `@ghost`
`@rustbot` modify labels: rollup
Suppress suggestions in derive macro
close#118809
I suppress warnings inside derive macros.
For example, the compiler emits following error by a program described in https://github.com/rust-lang/rust/issues/118809#issuecomment-1852256687 with a suggestion that indicates invalid syntax.
```
error[E0308]: `?` operator has incompatible types
--> src/main.rs:3:17
|
3 | #[derive(Debug, Deserialize)]
| ^^^^^^^^^^^ expected `u32`, found `u64`
|
= note: `?` operator cannot convert from `u64` to `u32`
= note: this error originates in the derive macro `Deserialize` (in Nightly builds, run with -Z macro-backtrace for more info)
help: you can convert a `u64` to a `u32` and panic if the converted value doesn't fit
|
3 | #[derive(Debug, Deserialize.try_into().unwrap())]
| ++++++++++++++++++++
For more information about this error, try `rustc --explain E0308`.
error: could not compile `serde_test` (bin "serde_test") due to 2 previous errors
```
In this PR, suggestions to cast are suppressed.
```
error[E0308]: `?` operator has incompatible types
--> src/main.rs:3:17
|
3 | #[derive(Debug, Deserialize)]
| ^^^^^^^^^^^ expected `u32`, found `u64`
|
= note: `?` operator cannot convert from `u64` to `u32`
= note: this error originates in the derive macro `Deserialize` (in Nightly builds, run with -Z macro-backtrace for more info)
For more information about this error, try `rustc --explain E0308`.
error: could not compile `serde_test` (bin "serde_test") due to 2 previous errors
```
Invert diagnostic lints.
That is, change `diagnostic_outside_of_impl` and `untranslatable_diagnostic` from `allow` to `deny`, because more than half of the compiler has been converted to use translated diagnostics.
This commit removes more `deny` attributes than it adds `allow` attributes, which proves that this change is warranted.
r? ````@davidtwco````
Remove some `unchecked_claim_error_was_emitted` calls
We want to drive the number of these calls down as much as possible. This PR gets rid of a bunch of them.
r? ``@oli-obk``
- In `emit_producing_error_guaranteed`, only allow `Level::Error`.
- In `emit_diagnostic`, only produce `ErrorGuaranteed` for `Level` and
`DelayedBug`. (Not `Bug` or `Fatal`. They don't need it, because the
relevant `emit` methods abort.)
- Add/update various comments.
Rework support for async closures; allow them to return futures that borrow from the closure's captures
This PR implements a new lowering for async closures via `TyKind::CoroutineClosure` which handles the curious relationship between the closure and the coroutine that it returns.
I wrote up a bunch in [this hackmd](https://hackmd.io/`@compiler-errors/S1HvqQxca)` which will be copied to the dev guide after this PR lands, and hopefully left sufficient comments in the source code explaining why this change is as large as it is.
This also necessitates that they begin implementing the `AsyncFn`-family of traits, rather than the `Fn`-family of traits -- if you need `Fn` implementations, you should probably use the non-sugar `|| async {}` syntax instead.
Notably this PR does not yet implement `async Fn()` syntax sugar for bounds, but I expect to add those soon (**edit:** #120392). For now, users must use `AsyncFn()` traits directly, which necessitates adding the `async_fn_traits` feature gate as well. I will add this as a follow-up very soon.
r? oli-obk
This is based on top of #120322, but that PR is minimal.
That is, change `diagnostic_outside_of_impl` and
`untranslatable_diagnostic` from `allow` to `deny`, because more than
half of the compiler has be converted to use translated diagnostics.
This commit removes more `deny` attributes than it adds `allow`
attributes, which proves that this change is warranted.
Revert outdated version of "Add the wasm32-wasi-preview2 target"
An outdated version of #119616 was merged in rollup #120309.
This reverts those changes to enable #119616 to “retain the intended diff” after a rebase.
```@rylev``` has agreed that this would be the cleanest approach with respect to the history.
Unblocks #119616.
r? ```@petrochenkov``` or compiler or libs
Add the `min_exhaustive_patterns` feature gate
## Motivation
Pattern-matching on empty types is tricky around unsafe code. For that reason, current stable rust conservatively requires arms for empty types in all but the simplest case. It has long been the intention to allow omitting empty arms when it's safe to do so. The [`exhaustive_patterns`](https://github.com/rust-lang/rust/issues/51085) feature allows the omission of all empty arms, but hasn't been stabilized because that was deemed dangerous around unsafe code.
## Proposal
This feature aims to stabilize an uncontroversial subset of exhaustive_patterns. Namely: when `min_exhaustive_patterns` is enabled and the data we're matching on is guaranteed to be valid by rust's operational semantics, then we allow empty arms to be omitted. E.g.:
```rust
let x: Result<T, !> = foo();
match x { // ok
Ok(y) => ...,
}
let Ok(y) = x; // ok
```
If the place is not guaranteed to hold valid data (namely ptr dereferences, ref dereferences (conservatively) and union field accesses), then we keep stable behavior i.e. we (usually) require arms for the empty cases.
```rust
unsafe {
let ptr: *const Result<u32, !> = ...;
match *ptr {
Ok(x) => { ... }
Err(_) => { ... } // still required
}
}
let foo: Result<u32, &!> = ...;
match foo {
Ok(x) => { ... }
Err(&_) => { ... } // still required because of the dereference
}
unsafe {
let ptr: *const ! = ...;
match *ptr {} // already allowed on stable
}
```
Note that we conservatively consider that a valid reference can point to invalid data, hence we don't allow arms of type `&!` and similar cases to be omitted. This could eventually change depending on [opsem decisions](https://github.com/rust-lang/unsafe-code-guidelines/issues/413). Whenever opsem is undecided on a case, we conservatively keep today's stable behavior.
I proposed this behavior in the [`never_patterns`](https://github.com/rust-lang/rust/issues/118155) feature gate but it makes sense on its own and could be stabilized more quickly. The two proposals nicely complement each other.
## Unresolved Questions
Part of the question is whether this requires an RFC. I'd argue this doesn't need one since there is no design question beyond the intent to omit unreachable patterns, but I'm aware the problem can be framed in ways that require design (I'm thinking of the [original never patterns proposal](https://smallcultfollowing.com/babysteps/blog/2018/08/13/never-patterns-exhaustive-matching-and-uninhabited-types-oh-my/), which would frame this behavior as "auto-nevering" happening).
EDIT: I initially proposed a future-compatibility lint as part of this feature, I don't anymore.
remove StructuralEq trait
The documentation given for the trait is outdated: *all* function pointers implement `PartialEq` and `Eq` these days. So the `StructuralEq` trait doesn't really seem to have any reason to exist any more.
One side-effect of this PR is that we allow matching on some consts that do not implement `Eq`. However, we already allowed matching on floats and consts containing floats, so this is not new, it is just allowed in more cases now. IMO it makes no sense at all to allow float matching but also sometimes require an `Eq` instance. If we want to require `Eq` we should adjust https://github.com/rust-lang/rust/pull/115893 to check for `Eq`, and rule out float matching for good.
Fixes https://github.com/rust-lang/rust/issues/115881
Add `AsyncFn` family of traits
I'm proposing to add a new family of `async`hronous `Fn`-like traits to the standard library for experimentation purposes.
## Why do we need new traits?
On the user side, it is useful to be able to express `AsyncFn` trait bounds natively via the parenthesized sugar syntax, i.e. `x: impl AsyncFn(&str) -> String` when experimenting with async-closure code.
This also does not preclude `AsyncFn` becoming something else like a trait alias if a more fundamental desugaring (which can take many[^1] different[^2] forms) comes around. I think we should be able to play around with `AsyncFn` well before that, though.
I'm also not proposing stabilization of these trait names any time soon (we may even want to instead express them via new syntax, like `async Fn() -> ..`), but I also don't think we need to introduce an obtuse bikeshedding name, since `AsyncFn` just makes sense.
## The lending problem: why not add a more fundamental primitive of `LendingFn`/`LendingFnMut`?
Firstly, for `async` closures to be as flexible as possible, they must be allowed to return futures which borrow from the async closure's captures. This can be done by introducing `LendingFn`/`LendingFnMut` traits, or (equivalently) by adding a new generic associated type to `FnMut` which allows the return type to capture lifetimes from the `&mut self` argument of the trait. This was proposed in one of [Niko's blog posts](https://smallcultfollowing.com/babysteps/blog/2023/05/09/giving-lending-and-async-closures/).
Upon further experimentation, for the purposes of closure type- and borrow-checking, I've come to the conclusion that it's significantly harder to teach the compiler how to handle *general* lending closures which may borrow from their captures. This is, because unlike `Fn`/`FnMut`, the `LendingFn`/`LendingFnMut` traits don't form a simple "inheritance" hierarchy whose top trait is `FnOnce`.
```mermaid
flowchart LR
Fn
FnMut
FnOnce
LendingFn
LendingFnMut
Fn -- isa --> FnMut
FnMut -- isa --> FnOnce
LendingFn -- isa --> LendingFnMut
Fn -- isa --> LendingFn
FnMut -- isa --> LendingFnMut
```
For example:
```
fn main() {
let s = String::from("hello, world");
let f = move || &s;
let x = f(); // This borrows `f` for some lifetime `'1` and returns `&'1 String`.
```
That trait hierarchy means that in general for "lending" closures, like `f` above, there's not really a meaningful return type for `<typeof(f) as FnOnce>::Output` -- it can't return `&'static str`, for example.
### Special-casing this problem:
By splitting out these traits manually, and making sure that each trait has its own associated future type, we side-step the issue of having to answer the questions of a general `LendingFn`/`LendingFnMut` implementation, since the compiler knows how to generate built-in implementations for first-class constructs like async closures, including the required future types for the (by-move) `AsyncFnOnce` and (by-ref) `AsyncFnMut`/`AsyncFn` trait implementations.
[^1]: For example, with trait transformers, we may eventually be able to write: `trait AsyncFn = async Fn;`
[^2]: For example, via the introduction of a more fundamental "`LendingFn`" trait, plus a [special desugaring with augmented trait aliases](https://rust-lang.zulipchat.com/#narrow/stream/213817-t-lang/topic/Lending.20closures.20and.20Fn*.28.29.20-.3E.20impl.20Trait/near/408471480).
Replacement of #114390: Add new intrinsic `is_var_statically_known` and optimize pow for powers of two
This adds a new intrinsic `is_val_statically_known` that lowers to [``@llvm.is.constant.*`](https://llvm.org/docs/LangRef.html#llvm-is-constant-intrinsic).` It also applies the intrinsic in the int_pow methods to recognize and optimize the idiom `2isize.pow(x)`. See #114390 for more discussion.
While I have extended the scope of the power of two optimization from #114390, I haven't added any new uses for the intrinsic. That can be done in later pull requests.
Note: When testing or using the library, be sure to use `--stage 1` or higher. Otherwise, the intrinsic will be a noop and the doctests will be skipped. If you are trying out edits, you may be interested in [`--keep-stage 0`](https://rustc-dev-guide.rust-lang.org/building/suggested.html#faster-builds-with---keep-stage).
Fixes#47234Resolves#114390
`@Centri3`
Add a new `wasm32-wasi-preview2` target
This is the initial implementation of the MCP https://github.com/rust-lang/compiler-team/issues/694 creating a new tier 3 target `wasm32-wasi-preview2`. That MCP has been seconded and will most likely be approved in a little over a week from now. For more information on the need for this target, please read the [MCP](https://github.com/rust-lang/compiler-team/issues/694).
There is one aspect of this PR that will become insta-stable once these changes reach a stable compiler:
* A new `target_family` named `wasi` is introduced. This target family incorporates all wasi targets including `wasm32-wasi` and its derivative `wasm32-wasi-preview1-threads`. The difference between `target_family = wasi` and `target_os = wasi` will become much clearer when `wasm32-wasi` is renamed to `wasm32-wasi-preview1` and the `target_os` becomes `wasm32-wasi-preview1`. You can read about this target rename in [this MCP](https://github.com/rust-lang/compiler-team/issues/695) which has also been seconded and will hopefully be officially approved soon.
Additional technical details include:
* Both `std::sys::wasi_preview2` and `std::os::wasi_preview2` have been created and mostly use `#[path]` annotations on their submodules to reach into the existing `wasi` (soon to be `wasi_preview1`) modules. Over time the differences between `wasi_preview1` and `wasi_preview2` will grow and most like all `#[path]` based module aliases will fall away.
* Building `wasi-preview2` relies on a [`wasi-sdk`](https://github.com/WebAssembly/wasi-sdk) in the same way that `wasi-preview1` does (one must include a `wasi-root` path in the `Config.toml` pointing to sysroot included in the wasi-sdk). The target should build against [wasi-sdk v21](https://github.com/WebAssembly/wasi-sdk/releases/tag/wasi-sdk-21) without modifications. However, the wasi-sdk itself is growing [preview2 support](https://github.com/WebAssembly/wasi-sdk/pull/370) so this might shift rapidly. We will be following along quickly to make sure that building the target remains possible as the wasi-sdk changes.
* This requires a [patch to libc](https://github.com/rylev/rust-libc/tree/wasm32-wasi-preview2) that we'll need to land in conjunction with this change. Until that patch lands the target won't actually build.
Consolidate logic around resolving built-in coroutine trait impls
Deduplicates a lot of code. Requires defining a new lang item for `Coroutine::resume` for consistency, but it seems not harmful at worst, and potentially later useful at best.
r? oli-obk
