This is a aspect of Rust that frequently trips up people who are not
aware of it yet. This diagnostic attempts to explain what's happening
and why the lifetime constraint, that was never mentioned in the source,
arose.
Deny more `~const` trait bounds
thereby fixing a family of ICEs (delayed bugs) for `feature(const_trait_impl, effects)` code.
As discussed
r? `@fee1-dead`
Add `std:#️⃣:{DefaultHasher, RandomState}` exports (needs FCP)
This implements rust-lang/libs-team#267 to move the libstd hasher types to `std::hash` where they belong, instead of `std::collections::hash_map`.
<details><summary>The below no longer applies, but is kept for clarity.</summary>
This is a small refactor for #27242, which moves the definitions of `RandomState` and `DefaultHasher` into `std::hash`, but in a way that won't be noticed in the public API.
I've opened rust-lang/libs-team#267 as a formal ACP to move these directly into the root of `std::hash`, but for now, they're at least separated out from the collections code in a way that will make moving that around easier.
I decided to simply copy the rustdoc for `std::hash` from `core::hash` since I think it would be ideal for the two to diverge longer-term, especially if the ACP is accepted. However, I would be willing to factor them out into a common markdown document if that's preferred.
</details>
Emit #[inline] on derive(Debug)
While working on https://github.com/rust-lang/rust/pull/116583 I noticed that the `cross_crate_inlinable` query identifies a lot of derived `Debug` impls as a MIR body that's little more than a call, which suggests they may be a good candidate for `#[inline]`. So here I've implemented that change specifically.
It seems to provide a nice improvement to build times.
generator layout: ignore fake borrows
fixes#117059
We emit fake shallow borrows in case the scrutinee place uses a `Deref` and there is a match guard. This is necessary to prevent the match guard from mutating the scrutinee: fab1054e17/compiler/rustc_mir_build/src/build/matches/mod.rs (L1250-L1265)
These fake borrows end up impacting the generator witness computation in `mir_generator_witnesses`, which causes the issue in #117059. This PR now completely ignores fake borrows during this computation. This is sound as thse are always removed after analysis and the actual computation of the generator layout happens afterwards.
Only the second commit impacts behavior, and could be backported by itself.
r? types
Extend builtin/auto trait args with error when they have >1 argument
Reuse `extend_with_error` to add error args to any auto trait (or built-in trait like `Copy` that is defined incorrectly) that has additional non-`Self` args.
Fixes#117628
patterns: reject raw pointers that are not just integers
Matching against `0 as *const i32` is fine, matching against `&42 as *const i32` is not.
This extends the existing check against function pointers and wide pointers: we now uniformly reject all these pointer types during valtree construction, and then later lint because of that. See [here](https://github.com/rust-lang/rust/pull/116930#issuecomment-1784654073) for some more explanation and context.
Also fixes https://github.com/rust-lang/rust/issues/116929.
Cc `@oli-obk` `@lcnr`
Rollup of 5 pull requests
Successful merges:
- #117263 (handle the case when the change-id isn't found)
- #117282 (Recover from incorrectly ordered/duplicated function keywords)
- #117679 (tests/rustdoc-json: Avoid needless use of `no_core` and `lang_items`)
- #117702 (target: move base and target specifications)
- #117713 (Add test for reexported hidden item with `--document-hidden-items`)
r? `@ghost`
`@rustbot` modify labels: rollup
Compute polonius loan scopes over the region graph
In issue #117146 a loan flows into an SCC containing a placeholder, and whose representative is an existential region. Since we currently compute loan scopes by looking at SCCs and their representatives only, polonius would compute kill points for this loan here whereas NLLs would not of course.
There are a few ways to fix this:
- don't try to be efficient by doing the computation over SCCs, and simply look for free regions and placeholders in the successors of the issuing region.
- change how the SCC representatives are picked, biasing towards placeholders over existential regions. They *shouldn't* matter much, but some downstream code may subtly depend on the current scheme (though no tests fail if we do such a change). This is for unrelated reasons also the way #116891 changes the representative computation. So that PR would also fix issue #117146.
- try to remove placeholders from the main path, and contain them to a pre-pass + a post-pass kind of polonius leak check. If possible, it would fix this issue by turning an outlives constraints to a placeholder into a constraint to 'static. This should also fix the issue, as the representative would be the free region in the SCC. We want to prototype this change to see if it's possible to try to simplify the borrowck main path from having to deal with placeholders and higher-ranked subtyping 🤞.
I'd like to take advantage of fuzzing and a crater run sooner rather than later, so that we grow more confidence that the 2 models are indeed equivalent empirically. Therefore this PR implements option 1 to fix the issue now.
We can take care of efficiency later after validation, and once we implement option 3 (which could also impact option 2 and that associated PR, maybe the lack of placeholders could remove the need to change the representative computation) to traverse SCCs and their representative again.
(Or we maybe will have some kind of naive position-dependent outlives propagation by then and this code would have been changed)
Fixes#117146.
r? `@matthewjasper`
Only use `normalize_param_env` when normalizing predicate in `check_item_bounds`
Only use the `normalize_param_env` when normalizing the item bound predicate in `check_item_bounds`, instead of using it when processing this obligation as well. This causes <BUG> to reoccur, but hopefully with better caching in the future, we can fix this would having such bad effects on perf.
This PR also fixes#117598. It turns out that the GAT predicate that we install is actually wrong -- given code like:
```
impl<'r> HasValueRef<'r> for Any {
type Database = Any;
}
```
We currently generate a predicate that looks like `<Any as HasValueRef<'r>>::Database = Any`, where `'r` is an early-bound variable. Really this GAT assumption should be universally quantified over the impl's args, i.e. `for<'r> <Any as HasValueRef<'r>>::Database = Any`, but then we'd need the binder to also include all the WC of the impl as well, which we don't support yet, lol.
To avoid `!matches!(...)`, which is hard to think about. Instead every
case now uses direct pattern matching and returns true or false.
Also add a couple of cases to the `stringify.rs` test that currently
print badly.
Method suggestion code tweaks
I was rummaging around the method suggestion code after https://github.com/rust-lang/rust/pull/117006#discussion_r1384153722 and saw a few things to simplify.
This is two unrelated commits, both in the same file. Review them separately, if you'd like.
r? estebank
warn when using an unstable feature with -Ctarget-feature
Setting or unsetting the wrong target features can cause ABI incompatibility (https://github.com/rust-lang/rust/issues/116344, https://github.com/rust-lang/rust/issues/116558). We need to carefully audit features for their ABI impact before stabilization. I just learned that we currently accept arbitrary unstable features on stable and if they are in the list of Rust target features, even unstable, then we don't even warn about that!1 That doesn't seem great, so I propose we introduce a warning here.
This has an obvious loophole via `-Ctarget-cpu`. I'm not sure how to best deal with that, but it seems better to fix what we can and think about the other cases later, maybe once we have a better idea for how to resolve the general mess that are ABI-affecting target features.
Give a better diagnostic for missing parens in Fn* bounds
Fixes#108109
It would be nice to try and recover here, but I'm not sure it's worth the effort, especially as the bounds on the recovered function would be incorrect.
Thir unsafeck fixes
- Recognise thread local statics in THIR unsafeck
- Add suggestion for unsafe_op_in_unsafe_fn
- Fix unsafe checking of let expressions
Only instantiate binder during dyn's built-in trait candidate probe once
See UI test for demonstration of the issue.
This was "caused" by #117131, but only because we're using the `normalize_param_env` (which has been augmented with a projection clause used to normalize GATs) which features non-lifetime bound vars in it.
Fixes#117602 technically, though that's also fixed by #117542.
r? types
When not finding assoc fn on type, look for builder fn
When we have a resolution error when looking at a fully qualified path on a type, look for all associated functions on inherent impls that return `Self` and mention them to the user.
```
error[E0599]: no function or associated item named `new` found for struct `TcpStream` in the current scope
--> tests/ui/resolve/fn-new-doesnt-exist.rs:4:28
|
4 | let stream = TcpStream::new();
| ^^^ function or associated item not found in `TcpStream`
|
note: if you're trying to build a new `TcpStream` consider using one of the following associated functions:
TcpStream::connect
TcpStream::connect_timeout
--> /home/gh-estebank/rust/library/std/src/net/tcp.rs:156:5
|
156 | pub fn connect<A: ToSocketAddrs>(addr: A) -> io::Result<TcpStream> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
...
172 | pub fn connect_timeout(addr: &SocketAddr, timeout: Duration) -> io::Result<TcpStream> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
```
Fix#69512.
When we have a resolution error when looking at a fully qualified path
on a type, look for all associated functions on inherent impls that
return `Self` and mention them to the user.
Fix#69512.
Emit explanatory note for move errors in packed struct derives
Derive expansions for packed structs with non-`Copy` fields cause move errors because they prefer copying over borrowing since borrowing the fields of a packed struct can result in unaligned access.
This underlying cause of the errors, however, is not apparent to the user. This PR adds a diagnostic note to make it clear to the user (the new note is on the second last line):
```
tests/ui/derives/deriving-with-repr-packed-move-errors.rs:13:16
|
12 | #[derive(Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Clone, Default)]
| ----- in this derive macro expansion
13 | struct StructA(String);
| ^^^^^^ move occurs because `self.0` has type `String`, which does not implement the `Copy` trait
|
= note: `#[derive(Debug)]` triggers a move because taking references to the fields of a packed struct is undefined behaviour
= note: this error originates in the derive macro `Debug` (in Nightly builds, run with -Z macro-backtrace for more info)
```
Fixes#117406
Partially addresses #110777
Rollup of 4 pull requests
Successful merges:
- #117190 (add test for #113381)
- #117516 (add test for #113375)
- #117631 (Documentation cleanup for core::error::Request.)
- #117637 (Check binders with bound vars for global bounds that don't hold)
r? `@ghost`
`@rustbot` modify labels: rollup
Detect misparsed binop caused by missing semi
When encountering
```rust
foo()
*bar = baz;
```
We currently emit potentially two errors, one for the return type of
`foo` not being multiplicative by the type of `bar`, and another for
`foo() * bar` not being assignable.
We now check for this case and suggest adding a semicolon in the right
place and emit only a single error.
Fix#80446.
Stabilize `const_maybe_uninit_zeroed` and `const_mem_zeroed`
Make `MaybeUninit::zeroed` and `mem::zeroed` const stable. Newly stable API:
```rust
// core::mem
pub const unsafe fn zeroed<T>() ->;
impl<T> MaybeUninit<T> {
pub const fn zeroed() -> MaybeUninit<T>;
}
```
This relies on features based around `const_mut_refs`. Per `@RalfJung,` this should be OK since we do not leak any `&mut` to the user.
For this to be possible, intrinsics `assert_zero_valid` and `assert_mem_uninitialized_valid` were made const stable.
Tracking issue: #91850
Zulip discussion: https://rust-lang.zulipchat.com/#narrow/stream/146212-t-compiler.2Fconst-eval/topic/.60const_mut_refs.60.20dependents
r? libs-api
`@rustbot` label -T-libs +T-libs-api +A-const-eval
cc `@RalfJung` `@oli-obk` `@rust-lang/wg-const-eval`
Make sure that predicates with unmentioned bound vars are still considered global in the old solver
In the old solver, we consider predicates with late-bound vars to not be "global":
9c8a2694fa/compiler/rustc_trait_selection/src/traits/select/mod.rs (L1840-L1844)
The implementation of `has_late_bound_vars` was modified in #115834 so that we'd properly anonymize binders that had late-bound vars but didn't reference them. This fixed an ICE.
However, this also led to a behavioral change in https://github.com/rust-lang/rust/issues/117056#issuecomment-1775014545 for a couple of crates, which now consider `for<'a> GL33: Shader` (note the binder var that is *not* used in the predicate) to not be "global". This forces associated types to not be normalizable due to the old trait solver being dumb.
This PR distinguishes types which *reference* late-bound vars and binders which *have* late-bound vars. The latter is represented with the new type flag `TypeFlags::HAS_BINDER_VARS`, which is used when we only care about knowing whether binders have vars in their bound var list (even if they're not used, like for binder anonymization).
This should fix (after beta backport) the `luminance-gl` and `luminance-webgl` crates in #117056.
r? types
**(priority is kinda high on a review here given beta becomes stable on November 16.)**
Hint optimizer about try-reserved capacity
This is #116568, but limited only to the less-common `try_reserve` functions to reduce bloat in debug binaries from debug info, while still addressing the main use-case #116570
Rollup of 6 pull requests
Successful merges:
- #110340 (Deref docs: expand and remove "smart pointer" qualifier)
- #116894 (Guarantee that `char` has the same size and alignment as `u32`)
- #117534 (clarify that the str invariant is a safety, not validity, invariant)
- #117562 (triagebot no-merges: exclude different case)
- #117570 (fallback for `construct_generic_bound_failure`)
- #117583 (Remove `'tcx` lifetime on `PlaceholderConst`)
r? `@ghost`
`@rustbot` modify labels: rollup
fallback for `construct_generic_bound_failure`
Fixes#117547
This case regressed at #115882.
In this context, `generic_param_scope` is produced by `RPITVisitor` and not included by `hir_owner`. Therefore, I've added a fallback to address this.
Make `core::mem::zeroed` const stable. Newly stable API:
// core::mem
pub const unsafe fn zeroed<T>() -> T;
This is stabilized with `const_maybe_uninit_zeroed` since it is a simple
wrapper.
In order to make this possible, intrinsics `assert_zero_valid` was made
const stable under `const_assert_type2`.
`assert_mem_uninitialized_valid` was also made const stable since it is
under the same gate.
Update the alignment checks to match rust-lang/reference#1387
Previously, we had a special case to not check `Rvalue::AddressOf` in this pass because we weren't quite sure if pointers needed to be aligned in the Place passed to it: https://github.com/rust-lang/rust/pull/112026
Since https://github.com/rust-lang/reference/pull/1387 merged, this PR updates this pass to match. The behavior of the check is nearly unchanged, except we also avoid inserting a check for creating references. Most of the changes in this PR are cleanup and new tests.
Cleanup `rustc_mir_build/../check_match.rs`
The file had become pretty unwieldy, with a fair amount of duplication. As a bonus, I discovered that we weren't running some pattern checks in if-let chains.
I recommend looking commit-by-commit. The last commit is a whim, I think it makes more sense that way but I don't hold this opinion strongly.
They've been deprecated for four years.
This commit includes the following changes.
- It eliminates the `rustc_plugin_impl` crate.
- It changes the language used for lints in
`compiler/rustc_driver_impl/src/lib.rs` and
`compiler/rustc_lint/src/context.rs`. External lints are now called
"loaded" lints, rather than "plugins" to avoid confusion with the old
plugins. This only has a tiny effect on the output of `-W help`.
- E0457 and E0498 are no longer used.
- E0463 is narrowed, now only relating to unfound crates, not plugins.
- The `plugin` feature was moved from "active" to "removed".
- It removes the entire plugins chapter from the unstable book.
- It removes quite a few tests, mostly all of those in
`tests/ui-fulldeps/plugin/`.
Closes#29597.
Fix incorrect trait bound restriction suggestion
Suggest
```
error[E0308]: mismatched types
--> $DIR/restrict-assoc-type-of-generic-bound.rs:9:12
|
LL | pub fn foo<A: MyTrait, B>(a: A) -> B {
| - - expected `B` because of return type
| |
| expected this type parameter
LL | return a.bar();
| ^^^^^^^ expected type parameter `B`, found associated type
|
= note: expected type parameter `B`
found associated type `<A as MyTrait>::T`
help: consider further restricting this bound
|
LL | pub fn foo<A: MyTrait<T = B>, B>(a: A) -> B {
| +++++++
```
instead of
```
error[E0308]: mismatched types
--> $DIR/restrict-assoc-type-of-generic-bound.rs:9:12
|
LL | pub fn foo<A: MyTrait, B>(a: A) -> B {
| - - expected `B` because of return type
| |
| expected this type parameter
LL | return a.bar();
| ^^^^^^^ expected type parameter `B`, found associated type
|
= note: expected type parameter `B`
found associated type `<A as MyTrait>::T`
help: consider further restricting this bound
|
LL | pub fn foo<A: MyTrait + <T = B>, B>(a: A) -> B {
| +++++++++
```
Fix#117501.
Pretty print `Fn` traits in `rustc_on_unimplemented`
I don't think that users really ever should need to think about `Fn*` traits' tupled args for a simple trait error.
r? diagnostics
Derive expansions for packed structs cause move errors because
they prefer copying over borrowing since borrowing the fields of a
packed struct can result in unaligned access and therefore undefined
behaviour.
This underlying cause of the errors, however, is not apparent
to the user. We add a diagnostic note here to remedy that.
Add all RPITITs when augmenting param-env with GAT bounds in `check_type_bounds`
When checking that associated type definitions actually satisfy their associated type bounds in `check_type_bounds`, we construct a "`normalize_param_env`" which adds a projection predicate that allows us to assume that we can project the GAT to the definition we're checking. For example, in:
```rust
type Foo {
type Bar: Display = i32;
}
```
We would add `<Self as Foo>::Bar = i32` as a projection predicate when checking that `i32: Display` holds.
That `normalize_param_env` was, for some reason, only being used to normalize the predicate before it was registered. This is sketchy, because a nested obligation may require the GAT bound to hold, and also the projection cache is broken and doesn't differentiate projection cache keys that differ by param-envs 😿.
This `normalize_param_env` is also not sufficient when we have nested RPITITs and default trait methods, since we need to be able to assume we can normalize both the RPITIT and all of its child RPITITs to sufficiently prove all of its bounds. This is the cause of #117104, which only starts to fail for RPITITs that are nested 3 and above due to the projection-cache bug above.[^1]
## First fix
Use the `normalize_param_env` everywhere in `check_type_bounds`. This is reflected in a test I've constructed that fixes a GAT-only failure.
## Second fix
For RPITITs, install projection predicates for each RPITIT in the same function in `check_type_bounds`. This fixes#117104.
not sure who to request, so...
r? `@lcnr` hehe feel free to reassign :3
[^1]: The projection cache bug specifically occurs because we try normalizing the `assumed_wf_types` with the non-normalization param-env. This causes us to insert a projection cache entry that keeps the outermost RPITIT rigid, and it trivially satisifes all its own bounds. Super sketchy![^2]
[^2]: I haven't actually gone and fixed the projection cache bug because it's only marginally related, but I could, and it should no longer be triggered here.
Suggest
```
error[E0308]: mismatched types
--> $DIR/restrict-assoc-type-of-generic-bound.rs:9:12
|
LL | pub fn foo<A: MyTrait, B>(a: A) -> B {
| - - expected `B` because of return type
| |
| expected this type parameter
LL | return a.bar();
| ^^^^^^^ expected type parameter `B`, found associated type
|
= note: expected type parameter `B`
found associated type `<A as MyTrait>::T`
help: consider further restricting this bound
|
LL | pub fn foo<A: MyTrait<T = B>, B>(a: A) -> B {
| +++++++
```
instead of
```
error[E0308]: mismatched types
--> $DIR/restrict-assoc-type-of-generic-bound.rs:9:12
|
LL | pub fn foo<A: MyTrait, B>(a: A) -> B {
| - - expected `B` because of return type
| |
| expected this type parameter
LL | return a.bar();
| ^^^^^^^ expected type parameter `B`, found associated type
|
= note: expected type parameter `B`
found associated type `<A as MyTrait>::T`
help: consider further restricting this bound
|
LL | pub fn foo<A: MyTrait + <T = B>, B>(a: A) -> B {
| +++++++++
```
Fix#117501.
Remove support for alias `-Z symbol-mangling-version`
(This is very similar to the removal of `-Z instrument-coverage` in #117111.)
`-C symbol-mangling-version` was stabilized back in rustc 1.59.0 (2022-02-24) via #90128, with the old unstable flag kept around (with a warning) as an alias to ease migration.
Clarify `Unsize` documentation
The documentation erroneously says that:
```rust
/// - Types implementing a trait `Trait` also implement `Unsize<dyn Trait>`.
/// - Structs `Foo<..., T, ...>` implement `Unsize<Foo<..., U, ...>>` if all of these conditions
/// are met:
/// - `T: Unsize<U>`.
/// - Only the last field of `Foo` has a type involving `T`.
/// - `Bar<T>: Unsize<Bar<U>>`, where `Bar<T>` stands for the actual type of that last field.
```
Specifically, `T: Unsize<U>` is not required to hold -- only the final field must implement `FinalField<T>: Unsize<FinalField<U>>`. This can be demonstrated by the test I added.
---
Second commit fleshes out the documentation a lot more.
Don't check for alias bounds in liveness when aliases have escaping bound vars
I actually have no idea how we *should* be treating aliases with escaping bound vars here... but the simplest behavior is just doing what we used to do before.
r? aliemjay
Fixes#117455
Account for `ref` and `mut` in the wrong place for pattern ident renaming
If the user writes `S { ref field: name }` instead of `S { field: ref name }`, we suggest the correct code.
Fix#72298.
Support enum variants in offset_of!
This MR implements support for navigating through enum variants in `offset_of!`, placing the enum variant name in the second argument to `offset_of!`. The RFC placed it in the first argument, but I think it interacts better with nested field access in the second, as you can then write things like
```rust
offset_of!(Type, field.Variant.field)
```
Alternatively, a syntactic distinction could be made between variants and fields (e.g. `field::Variant.field`) but I'm not convinced this would be helpful.
[RFC 3308 # Enum Support](https://rust-lang.github.io/rfcs/3308-offset_of.html#enum-support-offset_ofsomeenumstructvariant-field_on_variant)
Tracking Issue #106655.
Match usize/isize exhaustively with half-open ranges
The long-awaited finale to the saga of [exhaustiveness checking for integers](https://github.com/rust-lang/rust/pull/50912)!
```rust
match 0usize {
0.. => {} // exhaustive!
}
match 0usize {
0..usize::MAX => {} // helpful error message!
}
```
Features:
- Half-open ranges behave as expected for `usize`/`isize`;
- Trying to use `0..usize::MAX` will tell you that `usize::MAX..` is missing and explain why. No more unhelpful "`_` is missing";
- Everything else stays the same.
This should unblock https://github.com/rust-lang/rust/issues/37854.
Review-wise:
- I recommend looking commit-by-commit;
- This regresses perf because of the added complexity in `IntRange`; hopefully not too much;
- I measured each `#[inline]`, they all help a bit with the perf regression (tho I don't get why);
- I did not touch MIR building; I expect there's an easy PR there that would skip unnecessary comparisons when the range is half-open.
Rollup of 5 pull requests
Successful merges:
- #116267 (Some codegen cleanups around SIMD checks)
- #116712 (When encountering unclosed delimiters during lexing, check for diff markers)
- #117416 (Also consider TAIT to be uncomputable if the MIR body is tainted)
- #117421 (coverage: Replace impossible `coverage::Error` with assertions)
- #117438 (Do not ICE on constant evaluation failure in GVN.)
r? `@ghost`
`@rustbot` modify labels: rollup
Also consider TAIT to be uncomputable if the MIR body is tainted
Not totally sure if this is the best solution. We could, alternatively, look at the hir typeck results and try to take a type from there instead of just falling back to type error, inferring `u8` instead of `{type error}`. Not certain it really matters, though.
Happy to iterate on this.
Fixes#117413
r? ``@oli-obk`` cc ``@Nadrieril``
Store #[deprecated] attribute's `since` value in parsed form
This PR implements the first followup bullet listed in https://github.com/rust-lang/rust/pull/117148#issue-1960240108.
We centralize error handling to the attribute parsing code in `compiler/rustc_attr/src/builtin.rs`, and thereby remove some awkward error codepaths from later phases of compilation that had to make sense of these #\[deprecated\] attributes, namely `compiler/rustc_passes/src/stability.rs` and `compiler/rustc_middle/src/middle/stability.rs`.
Detect object safety errors when assoc type is missing
When an associated type with GATs isn't specified in a `dyn Trait`, emit an object safety error instead of only complaining about the missing associated type, as it will lead the user down a path of three different errors before letting them know that what they were trying to do is impossible to begin with.
Fix#103155.
When an associated type with GATs isn't specified in a `dyn Trait`, emit
an object safety error instead of only complaining about the missing
associated type, as it will lead the user down a path of three different
errors before letting them know that what they were trying to do is
impossible to begin with.
Fix#103155.
Rollup of 7 pull requests
Successful merges:
- #116862 (Detect when trait is implemented for type and suggest importing it)
- #117389 (Some diagnostics improvements of `gen` blocks)
- #117396 (Don't treat closures/coroutine types as part of the public API)
- #117398 (Correctly handle nested or-patterns in exhaustiveness)
- #117403 (Poison check_well_formed if method receivers are invalid to prevent typeck from running on it)
- #117411 (Improve some diagnostics around `?Trait` bounds)
- #117414 (Don't normalize to an un-revealed opaque when we hit the recursion limit)
r? `@ghost`
`@rustbot` modify labels: rollup
Don't normalize to an un-revealed opaque when we hit the recursion limit
Currently, we will normalize `Opaque := Option<&Opaque>` to something like `Option<&Option<&Option<&...Opaque>>>`, hitting a limit and bottoming out in an unnormalized opaque after the recursion limit gets hit.
Unfortunately, during `layout_of`, we'll simply recurse and try again if the type normalizes to something different than the type:
e6e931dda5/compiler/rustc_ty_utils/src/layout.rs (L58-L60)
That means then we'll try to normalize `Option<&Option<&Option<&...Opaque>>>` again, substituting `Opaque` into itself even deeper. Eventually this will get to the point that we're just stack-overflowing on a really deep type before even hitting an opaque again.
To fix this, we just bottom out into `ty::Error` instead of the unrevealed opaque type.
Fixes#117412
r? `@oli-obk`
Improve some diagnostics around `?Trait` bounds
* uses better spans
* clarifies a message that was only talking about generic params, but applies to `dyn ?Trait` and `impl ?Trait` as well
Poison check_well_formed if method receivers are invalid to prevent typeck from running on it
fixes#117379
Though if some code invokes typeck without having first invoked `check_well_formed` then we'll encounter this ICE again. This can happen in const and const fn bodies if they are evaluated due to other `check_well_formed` checks or similar
Correctly handle nested or-patterns in exhaustiveness
I had assumed nested or-patterns were flattened, and they mostly are but not always.
Fixes https://github.com/rust-lang/rust/issues/117378
Fix missing leading space in suggestion
For a local pattern with no space between `let` and `(` e.g.:
```rust
let(_a) = 3;
```
we were previously suggesting this illegal code:
```rust
let_a = 3;
```
After this change the suggestion will instead be:
```rust
let _a = 3;
```
Fixes#117380
C-variadic error improvements
A couple improvements for c-variadic errors:
1. Fix the bad-c-variadic error being emitted multiple times. If a function incorrectly contains multiple `...` args, and is also not foreign or `unsafe extern "C"`, only emit the latter error once rather than once per `...`.
2. Explicitly reject `const` C-variadic functions. Trying to use C-variadics in a const function would previously fail with an error like "destructor of `VaListImpl<'_>` cannot be evaluated at compile-time". Add an explicit check for const C-variadics to provide a clearer error: "functions cannot be both `const` and C-variadic". This also addresses one of the concerns in https://github.com/rust-lang/rust/issues/44930: "Ensure that even when this gets stabilized for regular functions, it is still rejected on const fn."
On object safety error, mention new enum as alternative
When we encounter a `dyn Trait` that isn't object safe, look for its implementors. If there's one, mention using it directly If there are less than 9, mention the possibility of creating a new enum and using that instead.
Fix#80194.
Trying to use C-variadics in a const function would previously fail with
an error like "destructor of `VaListImpl<'_>` cannot be evaluated at
compile-time".
Add an explicit check for const C-variadics to provide a clearer error:
"functions cannot be both `const` and C-variadic".
For a local pattern with no space between `let` and `(` e.g.:
let(_a) = 3;
we were previously suggesting this illegal code:
let_a =3;
After this change the suggestion will instead be:
let _a =3;
(Note the space after `let`)
Fail typeck for illegal break-with-value
This is fixes the issue wherein typeck was succeeding for break-with-value exprs at illegal locations such as inside `while`, `while let` and `for` loops which eventually caused an ICE during MIR interpretation for const eval.
Now we fail typeck for such code which prevents faulty MIR from being generated and interpreted, thus fixing the ICE.
Fixes#114529
Ignore RPIT duplicated lifetimes in `opaque_types_defined_by`
An RPIT's or TAIT's own generics are kinda useless -- so just ignore them. For TAITs, they will always be empty, and for RPITs, they're always duplicated lifetimes.
Fixes#115013.
Allows `#[diagnostic::on_unimplemented]` attributes to have multiple
notes
This commit extends the `#[diagnostic::on_unimplemented]` (and `#[rustc_on_unimplemented]`) attributes to allow multiple `note` options. This enables emitting multiple notes for custom error messages. For now I've opted to not change any of the existing usages of `#[rustc_on_unimplemented]` and just updated the relevant compile tests.
r? `@compiler-errors`
I'm happy to adjust any of the existing changed location to emit the old error message if that's desired.
This is fixes the issue wherein typeck was succeeding for break-with-value
at illegal locations such as inside `while`, `while let` and `for` loops which
eventually caused an ICE during MIR interpetation for const eval.
Now we fail typeck for such code which prevents faulty MIR from being generated
and interpreted, thus fixing the ICE.
When we encounter a `dyn Trait` that isn't object safe, look for its
implementors. If there's one, mention using it directly If there are
less than 9, mention the possibility of creating a new enum and using
that instead.
Account for object unsafe `impl Trait on dyn Trait {}`. Make a
distinction between public and sealed traits.
Fix#80194.
Consider alias bounds when computing liveness in NLL (but this time sound hopefully)
This is a revival of #116040, except removing the changes to opaque lifetime captures check to make sure that we're not triggering any unsoundness due to the lack of general existential regions and the currently-existing `ReErased` hack we use instead.
r? `@aliemjay` -- I appreciate you pointing out the unsoundenss in the previous iteration of this PR, and I'd like to hear that you're happy with this iteration of this PR before this goes back into FCP :>
Fixes#116794 as well
---
(mostly copied from #116040 and reworked slightly)
# Background
Right now, liveness analysis in NLL is a bit simplistic. It simply walks through all of the regions of a type and marks them as being live at points. This is problematic in the case of aliases, since it requires that we mark **all** of the regions in their args[^1] as live, leading to bugs like #42940.
In reality, we may be able to deduce that fewer regions are allowed to be present in the projected type (or "hidden type" for opaques) via item bounds or where clauses, and therefore ideally, we should be able to soundly require fewer regions to be live in the alias.
For example:
```rust
trait Captures<'a> {}
impl<T> Captures<'_> for T {}
fn capture<'o>(_: &'o mut ()) -> impl Sized + Captures<'o> + 'static {}
fn test_two_mut(mut x: ()) {
let _f1 = capture(&mut x);
let _f2 = capture(&mut x);
//~^ ERROR cannot borrow `x` as mutable more than once at a time
}
```
In the example above, we should be able to deduce from the `'static` bound on `capture`'s opaque that even though `'o` is a captured region, it *can never* show up in the opaque's hidden type, and can soundly be ignored for liveness purposes.
# The Fix
We apply a simple version of RFC 1214's `OutlivesProjectionEnv` and `OutlivesProjectionTraitDef` rules to NLL's `make_all_regions_live` computation.
Specifically, when we encounter an alias type, we:
1. Look for a unique outlives bound in the param-env or item bounds for that alias. If there is more than one unique region, bail, unless any of the outlives bound's regions is `'static`, and in that case, prefer `'static`. If we find such a unique region, we can mark that outlives region as live and skip walking through the args of the opaque.
2. Otherwise, walk through the alias's args recursively, as we do today.
## Limitation: Multiple choices
This approach has some limitations. Firstly, since liveness doesn't use the same type-test logic as outlives bounds do, we can't really try several options when we're faced with a choice.
If we encounter two unique outlives regions in the param-env or bounds, we simply fall back to walking the opaque via its args. I expect this to be mostly mitigated by the special treatment of `'static`, and can be fixed in a forwards-compatible by a more sophisticated analysis in the future.
## Limitation: Opaque hidden types
Secondly, we do not employ any of these rules when considering whether the regions captured by a hidden type are valid. That causes this code (cc #42940) to fail:
```rust
trait Captures<'a> {}
impl<T> Captures<'_> for T {}
fn a() -> impl Sized + 'static {
b(&vec![])
}
fn b<'o>(_: &'o Vec<i32>) -> impl Sized + Captures<'o> + 'static {}
```
We need to have existential regions to avoid [unsoundness](https://github.com/rust-lang/rust/pull/116040#issuecomment-1751628189) when an opaque captures a region which is not represented in its own substs but which outlives a region that does.
## Read more
Context: https://github.com/rust-lang/rust/pull/115822#issuecomment-1731153952 (for the liveness case)
More context: https://github.com/rust-lang/rust/issues/42940#issuecomment-455198309 (for the opaque capture case, which this does not fix)
[^1]: except for bivariant region args in opaques, which will become less relevant when we move onto edition 2024 capture semantics for opaques.
Implement `gen` blocks in the 2024 edition
Coroutines tracking issue https://github.com/rust-lang/rust/issues/43122
`gen` block tracking issue https://github.com/rust-lang/rust/issues/117078
This PR implements `gen` blocks that implement `Iterator`. Most of the logic with `async` blocks is shared, and thus I renamed various types that were referring to `async` specifically.
An example usage of `gen` blocks is
```rust
fn foo() -> impl Iterator<Item = i32> {
gen {
yield 42;
for i in 5..18 {
if i.is_even() { continue }
yield i * 2;
}
}
}
```
The limitations (to be resolved) of the implementation are listed in the tracking issue
Cleanup and improve `--check-cfg` implementation
This PR removes some indentation in the code, as well as preventing some bugs/misusages and fix a nit in the doc.
r? ```@petrochenkov``` (maybe)
When encountering sealed traits, point types that implement it
```
error[E0277]: the trait bound `S: d::Hidden` is not satisfied
--> $DIR/sealed-trait-local.rs:53:20
|
LL | impl c::Sealed for S {}
| ^ the trait `d::Hidden` is not implemented for `S`
|
note: required by a bound in `c::Sealed`
--> $DIR/sealed-trait-local.rs:17:23
|
LL | pub trait Sealed: self::d::Hidden {
| ^^^^^^^^^^^^^^^ required by this bound in `Sealed`
= note: `Sealed` is a "sealed trait", because to implement it you also need to implement `c::d::Hidden`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it
= help: the following types implement the trait:
- c::X
- c::Y
```
The last `help` is new.
Allow partially moved values in match
This PR attempts to unify the behaviour between `let _ = PLACE`, `let _: TY = PLACE;` and `match PLACE { _ => {} }`.
The logical conclusion is that the `match` version should not check for uninitialised places nor check that borrows are still live.
The `match PLACE {}` case is handled by keeping a `FakeRead` in the unreachable fallback case to verify that `PLACE` has a legal value.
Schematically, `match PLACE { arms }` in surface rust becomes in MIR:
```rust
PlaceMention(PLACE)
match PLACE {
// Decision tree for the explicit arms
arms,
// An extra fallback arm
_ => {
FakeRead(ForMatchedPlace, PLACE);
unreachable
}
}
```
`match *borrow { _ => {} }` continues to check that `*borrow` is live, but does not read the value.
`match *borrow {}` both checks that `*borrow` is live, and fake-reads the value.
Continuation of ~https://github.com/rust-lang/rust/pull/102256~ ~https://github.com/rust-lang/rust/pull/104844~
Fixes https://github.com/rust-lang/rust/issues/99180https://github.com/rust-lang/rust/issues/53114
Fix ICE: Restrict param constraint suggestion
When encountering an associated item with a type param that could be constrained, do not look at the parent item if the type param comes from the associated item.
Fix#117209, fix#89868.
Properly restore snapshot when failing to recover parsing ternary
If the recovery parsed an expression, then failed to eat a `:`, it would return `false` without restoring the snapshot. Fix this by always restoring the snapshot when returning `false`.
Draft for now because I'd like to try and improve this recovery further.
Fixes#117208
```
error[E0277]: the trait bound `S: d::Hidden` is not satisfied
--> $DIR/sealed-trait-local.rs:53:20
|
LL | impl c::Sealed for S {}
| ^ the trait `d::Hidden` is not implemented for `S`
|
note: required by a bound in `c::Sealed`
--> $DIR/sealed-trait-local.rs:17:23
|
LL | pub trait Sealed: self::d::Hidden {
| ^^^^^^^^^^^^^^^ required by this bound in `Sealed`
= note: `Sealed` is a "sealed trait", because to implement it you also need to implement `c::d::Hidden`, which is not accessible; this is usually done to force you to use one of the provided types that already implement it
= help: the following types implement the trait:
- c::X
- c::Y
```
The last `help` is new.
When encountering
```rust
foo()
*bar = baz;
```
We currently emit potentially two errors, one for the return type of
`foo` not being multiplyiable by the type of `bar`, and another for
`foo() * bar` not being assignable.
We now check for this case and suggest adding a semicolon in the right
place.
Fix#80446.
Lint overlapping ranges as a separate pass
This reworks the [`overlapping_range_endpoints`](https://doc.rust-lang.org/beta/nightly-rustc/rustc_lint_defs/builtin/static.OVERLAPPING_RANGE_ENDPOINTS.html) lint. My motivations are:
- It was annoying to have this lint entangled with the exhaustiveness algorithm, especially wrt librarification;
- This makes the lint behave consistently.
Here's the consistency story. Take the following matches:
```rust
match (0u8, true) {
(0..=10, true) => {}
(10..20, true) => {}
(10..20, false) => {}
_ => {}
}
match (true, 0u8) {
(true, 0..=10) => {}
(true, 10..20) => {}
(false, 10..20) => {}
_ => {}
}
```
There are two semantically consistent options: option 1 we lint all overlaps between the ranges, option 2 we only lint the overlaps that could actually occur (i.e. the ones with `true`). Option 1 is what this PR does. Option 2 is possible but would require the exhaustiveness algorithm to track more things for the sake of the lint. The status quo is that we're inconsistent between the two.
Option 1 generates more false postives, but I prefer it from a maintainer's perspective. I do think the difference is minimal; cases where the difference is observable seem rare.
This PR adds a separate pass, so this will have a perf impact. Let's see how bad, it looked ok locally.
