```
error[E0271]: expected `{closure@fallback-closure-wrap.rs:18:40}` to be a closure that returns `()`, but it returns `!`
--> $DIR/fallback-closure-wrap.rs:19:9
|
LL | let error = Closure::wrap(Box::new(move || {
| -------
LL | panic!("Can't connect to server.");
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found `!`
|
= note: expected unit type `()`
found type `!`
= note: required for the cast from `Box<{closure@$DIR/fallback-closure-wrap.rs:18:40: 18:47}>` to `Box<dyn FnMut()>`
```
```
error[E0271]: expected `{closure@dont-ice-for-type-mismatch-in-closure-in-async.rs:6:10}` to be a closure that returns `bool`, but it returns `Option<()>`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:6:16
|
LL | call(|| -> Option<()> {
| ---- ------^^^^^^^^^^
| | |
| | expected `bool`, found `Option<()>`
| required by a bound introduced by this call
|
= note: expected type `bool`
found enum `Option<()>`
note: required by a bound in `call`
--> $DIR/dont-ice-for-type-mismatch-in-closure-in-async.rs:3:25
|
LL | fn call(_: impl Fn() -> bool) {}
| ^^^^ required by this bound in `call`
```
```
error[E0271]: expected `{closure@f670.rs:28:13}` to be a closure that returns `Result<(), _>`, but it returns `!`
--> f670.rs:28:20
|
28 | let c = |e| -> ! {
| -------^
| |
| expected `Result<(), _>`, found `!`
...
32 | f().or_else(c);
| ------- required by a bound introduced by this call
-Ztrack-diagnostics: created at compiler/rustc_trait_selection/src/error_reporting/traits/fulfillment_errors.rs:1433:28
|
= note: expected enum `Result<(), _>`
found type `!`
note: required by a bound in `Result::<T, E>::or_else`
--> /home/gh-estebank/rust/library/core/src/result.rs:1406:39
|
1406 | pub fn or_else<F, O: FnOnce(E) -> Result<T, F>>(self, op: O) -> Result<T, F> {
| ^^^^^^^^^^^^ required by this bound in `Result::<T, E>::or_else`
```
Simplify and consolidate the way we handle construct `OutlivesEnvironment` for lexical region resolution
This is best reviewed commit-by-commit. I tried to consolidate the API for lexical region resolution *first*, then change the API when it was finally behind a single surface.
r? lcnr or reassign
Properly check that array length is valid type during built-in unsizing in index
This results in duplicated errors, but this class of errors is not new; in general, we aren't really equipped to detect cases where a WF error due to a field type would be shadowed by the parent struct of that field also not being WF.
This also adds a note for these types of mismatches to make it clear that this is due to an array type.
Fixes#134352
r? boxyuwu
Rollup of 7 pull requests
Successful merges:
- #135625 ([cfg_match] Document the use of expressions.)
- #135902 (Do not consider child bound assumptions for rigid alias)
- #135943 (Rename `Piece::String` to `Piece::Lit`)
- #136104 (Add mermaid graphs of NLL regions and SCCs to polonius MIR dump)
- #136143 (Update books)
- #136147 (ABI-required target features: warn when they are missing in base CPU)
- #136164 (Refactor FnKind variant to hold &Fn)
r? `@ghost`
`@rustbot` modify labels: rollup
Rename `Piece::String` to `Piece::Lit`
This renames Piece::String to Piece::Lit to avoid shadowing std::string::String and removes "pub use Piece::*;".
Do not consider child bound assumptions for rigid alias
r? lcnr
See first commit for the important details. For second commit, I also stacked a somewhat opinionated name change, though I can separate that if needed.
Fixes https://github.com/rust-lang/trait-system-refactor-initiative/issues/149
Pass spans to `perform_locally_in_new_solver`
Nothing changes yet, but we may be able to use these spans in the future once we start dealing w the response region constraints better.
r? lcnr
Use identifiers more in diagnostics code
This should make the diagnostics code slightly more correct when rendering idents in mixed crate edition situations. Kinda a no-op, but a cleanup regardless.
r? oli-obk or reassign
Use short type string in E0308 secondary span label
We were previously printing the full type on the "this expression has type" label.
```
error[E0308]: mismatched types
--> $DIR/secondary-label-with-long-type.rs:8:9
|
LL | let () = x;
| ^^ - this expression has type `((..., ..., ..., ...), ..., ..., ...)`
| |
| expected `((..., ..., ..., ...), ..., ..., ...)`, found `()`
|
= note: expected tuple `((..., ..., ..., ...), ..., ..., ...)`
found unit type `()`
= note: the full type name has been written to '$TEST_BUILD_DIR/diagnostic-width/secondary-label-with-long-type/secondary-label-with-long-type.long-type-3987761834644699448.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Reported in a comment of #135919.
Forbid usage of `hir` `Infer` const/ty variants in ambiguous contexts
The feature `generic_arg_infer` allows providing `_` as an argument to const generics in order to infer them. This introduces a syntactic ambiguity as to whether generic arguments are type or const arguments. In order to get around this we introduced a fourth `GenericArg` variant, `Infer` used to represent `_` as an argument to generic parameters when we don't know if its a type or a const argument.
This made hir visitors that care about `TyKind::Infer` or `ConstArgKind::Infer` very error prone as checking for `TyKind::Infer`s in `visit_ty` would find *some* type infer arguments but not *all* of them as they would sometimes be lowered to `GenericArg::Infer` instead.
Additionally the `visit_infer` method would previously only visit `GenericArg::Infer` not *all* infers (e.g. `TyKind::Infer`), this made it very easy to override `visit_infer` and expect it to visit all infers when in reality it would only visit *some* infers.
---
This PR aims to fix those issues by making the `TyKind` and `ConstArgKind` types generic over whether the infer types/consts are represented by `Ty/ConstArgKind::Infer` or out of line (e.g. by a `GenericArg::Infer` or accessible by overiding `visit_infer`). We then make HIR Visitors convert all const args and types to the versions where infer vars are stored out of line and call `visit_infer` in cases where a `Ty`/`Const` would previously have had a `Ty/ConstArgKind::Infer` variant:
API Summary
```rust
enum AmbigArg {}
enum Ty/ConstArgKind<Unambig = ()> {
...
Infer(Unambig),
}
impl Ty/ConstArg {
fn try_as_ambig_ty/ct(self) -> Option<Ty/ConstArg<AmbigArg>>;
}
impl Ty/ConstArg<AmbigArg> {
fn as_unambig_ty/ct(self) -> Ty/ConstArg;
}
enum InferKind {
Ty(Ty),
Const(ConstArg),
Ambig(InferArg),
}
trait Visitor {
...
fn visit_ty/const_arg(&mut self, Ty/ConstArg<AmbigArg>) -> Self::Result;
fn visit_infer(&mut self, id: HirId, sp: Span, kind: InferKind) -> Self::Result;
}
// blanket impl'd, not meant to be overriden
trait VisitorExt {
fn visit_ty/const_arg_unambig(&mut self, Ty/ConstArg) -> Self::Result;
}
fn walk_unambig_ty/const_arg(&mut V, Ty/ConstArg) -> Self::Result;
fn walk_ty/const_arg(&mut V, Ty/ConstArg<AmbigArg>) -> Self::Result;
```
The end result is that `visit_infer` visits *all* infer args and is also the *only* way to visit an infer arg, `visit_ty` and `visit_const_arg` can now no longer encounter a `Ty/ConstArgKind::Infer`. Representing this in the type system means that it is now very difficult to mess things up, either accessing `TyKind::Infer` "just works" and you won't miss *some* type infers- or it doesn't work and you have to look at `visit_infer` or some `GenericArg::Infer` which forces you to think about the full complexity involved.
Unfortunately there is no lint right now about explicitly matching on uninhabited variants, I can't find the context for why this is the case 🤷♀️
I'm not convinced the framing of un/ambig ty/consts is necessarily the right one but I'm not sure what would be better. I somewhat like calling them full/partial types based on the fact that `Ty<Partial>`/`Ty<Full>` directly specifies how many of the type kinds are actually represented compared to `Ty<Ambig>` which which leaves that to the reader to figure out based on the logical consequences of it the type being in an ambiguous position.
---
tool changes have been modified in their own commits for easier reviewing by anyone getting cc'd from subtree changes. I also attempted to split out "bug fixes arising from the refactoring" into their own commit so they arent lumped in with a big general refactor commit
Fixes#112110
Remove usages of `QueryNormalizer` in the compiler
I want to get rid of the `QueryNormalizer`, possibly changing it to be special cased just for normalizing erasing regions, or perhaps adapting `normalize_erasing_regions` to use the assoc type normalizer if caching is sufficient and removing it altogther.
This removes the last two usages of `.query_normalize` in the *compiler*. There are a few usages left in rustdoc and clippy, which exist only because the query normalizer is more resilient to errors and non-well-formed alias types. I will remove those next.
r? lcnr or reassign
We were previously printing the full type on the "this expression has type" label.
```
error[E0308]: mismatched types
--> $DIR/secondary-label-with-long-type.rs:8:9
|
LL | let () = x;
| ^^ - this expression has type `((..., ..., ..., ...), ..., ..., ...)`
| |
| expected `((..., ..., ..., ...), ..., ..., ...)`, found `()`
|
= note: expected tuple `((..., ..., ..., ...), ..., ..., ...)`
found unit type `()`
= note: the full type name has been written to '$TEST_BUILD_DIR/diagnostic-width/secondary-label-with-long-type/secondary-label-with-long-type.long-type-3987761834644699448.txt'
= note: consider using `--verbose` to print the full type name to the console
```
Reported in a comment of #135919.
Add missing check for async body when suggesting await on futures.
Currently the compiler suggests adding `.await` to resolve some type conflicts without checking if the conflict happens in an async context. This can lead to the compiler suggesting `.await` in function signatures where it is invalid. Example:
```rs
trait A {
fn a() -> impl Future<Output = ()>;
}
struct B;
impl A for B {
fn a() -> impl Future<Output = impl Future<Output = ()>> {
async { async { () } }
}
}
```
```
error[E0271]: expected `impl Future<Output = impl Future<Output = ()>>` to be a future that resolves to `()`, but it resolves to `impl Future<Output = ()>`
--> bug.rs:6:15
|
6 | fn a() -> impl Future<Output = impl Future<Output = ()>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ expected `()`, found future
|
note: calling an async function returns a future
--> bug.rs:6:15
|
6 | fn a() -> impl Future<Output = impl Future<Output = ()>> {
| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
note: required by a bound in `A::{synthetic#0}`
--> bug.rs:2:27
|
2 | fn a() -> impl Future<Output = ()>;
| ^^^^^^^^^^^ required by this bound in `A::{synthetic#0}`
help: consider `await`ing on the `Future`
|
6 | fn a() -> impl Future<Output = impl Future<Output = ()>>.await {
| ++++++
```
The documentation of suggest_await_on_expect_found (`compiler/rustc_trait_selection/src/error_reporting/infer/suggest.rs:156`) even mentions such a check but does not actually implement it.
This PR adds that check to ensure `.await` is only suggested within async blocks.
There were 3 unit tests whose expected output needed to be changed because they had the suggestion outside of async. One of them (`tests/ui/async-await/dont-suggest-missing-await.rs`) actually tests that exact problem but expects it to be present.
Thanks to `@llenck` for initially noticing the bug and helping with fixing it
Don't pick `T: FnPtr` nested goals as the leaf goal in diagnostics for new solver
r? `@lcnr`
See `tests/ui/traits/next-solver/diagnostics/dont-pick-fnptr-bound-as-leaf.rs` for a minimized example of what code this affects the diagnostics off. The output of running nightly `-Znext-solver` on that test is the following:
```
error[E0277]: the trait bound `Foo: Trait` is not satisfied
--> src/lib.rs:14:20
|
14 | requires_trait(Foo);
| -------------- ^^^ the trait `FnPtr` is not implemented for `Foo`
| |
| required by a bound introduced by this call
|
note: required for `Foo` to implement `Trait`
--> src/lib.rs:7:16
|
7 | impl<T: FnPtr> Trait for T {}
| ----- ^^^^^ ^
| |
| unsatisfied trait bound introduced here
note: required by a bound in `requires_trait`
--> src/lib.rs:11:22
|
11 | fn requires_trait<T: Trait>(_: T) {}
| ^^^^^ required by this bound in `requires_trait`
```
Part of rust-lang/trait-system-refactor-initiative#148
Use `structurally_normalize` instead of manual `normalizes-to` goals in alias relate errors
r? `@lcnr`
I added `structurally_normalize_term` so that code that is generic over ty or const can use the structurally normalize helpers. See `tests/ui/traits/next-solver/diagnostics/alias_relate_error_uses_structurally_normalize.rs` for a description of the reason for the (now fixed) ICEs
This CL makes a number of small changes to dyn compatibility errors:
- "object safety" has been renamed to "dyn-compatibility" throughout
- "Convert to enum" suggestions are no longer generated when there
exists a type-generic impl of the trait or an impl for `dyn OtherTrait`
- Several error messages are reorganized for user readability
Additionally, the dyn compatibility error creation code has been
split out into functions.
cc #132713
cc #133267
remove support for the (unstable) #[start] attribute
As explained by `@Noratrieb:`
`#[start]` should be deleted. It's nothing but an accidentally leaked implementation detail that's a not very useful mix between "portable" entrypoint logic and bad abstraction.
I think the way the stable user-facing entrypoint should work (and works today on stable) is pretty simple:
- `std`-using cross-platform programs should use `fn main()`. the compiler, together with `std`, will then ensure that code ends up at `main` (by having a platform-specific entrypoint that gets directed through `lang_start` in `std` to `main` - but that's just an implementation detail)
- `no_std` platform-specific programs should use `#![no_main]` and define their own platform-specific entrypoint symbol with `#[no_mangle]`, like `main`, `_start`, `WinMain` or `my_embedded_platform_wants_to_start_here`. most of them only support a single platform anyways, and need cfg for the different platform's ways of passing arguments or other things *anyways*
`#[start]` is in a super weird position of being neither of those two. It tries to pretend that it's cross-platform, but its signature is a total lie. Those arguments are just stubbed out to zero on ~~Windows~~ wasm, for example. It also only handles the platform-specific entrypoints for a few platforms that are supported by `std`, like Windows or Unix-likes. `my_embedded_platform_wants_to_start_here` can't use it, and neither could a libc-less Linux program.
So we have an attribute that only works in some cases anyways, that has a signature that's a total lie (and a signature that, as I might want to add, has changed recently, and that I definitely would not be comfortable giving *any* stability guarantees on), and where there's a pretty easy way to get things working without it in the first place.
Note that this feature has **not** been RFCed in the first place.
*This comment was posted [in May](https://github.com/rust-lang/rust/issues/29633#issuecomment-2088596042) and so far nobody spoke up in that issue with a usecase that would require keeping the attribute.*
Closes https://github.com/rust-lang/rust/issues/29633
try-job: x86_64-gnu-nopt
try-job: x86_64-msvc-1
try-job: x86_64-msvc-2
try-job: test-various
Rework dyn trait lowering to stop being so intertwined with trait alias expansion
This PR reworks the trait object lowering code to stop handling trait aliases so funky, and removes the `TraitAliasExpander` in favor of a much simpler design. This refactoring is important for making the code that I'm writing in https://github.com/rust-lang/rust/pull/133397 understandable and easy to maintain, so the diagnostics regressions are IMO inevitable.
In the old trait object lowering code, we used to be a bit sloppy with the lists of traits in their unexpanded and expanded forms. This PR largely rewrites this logic to expand the trait aliases *once* and handle them more responsibly throughout afterwards.
Please review this with whitespace disabled.
r? lcnr
new solver: prefer trivial builtin impls
As discussed [on zulip](https://rust-lang.zulipchat.com/#narrow/channel/364551-t-types.2Ftrait-system-refactor/topic/needs_help.3A.20trivial.20builtin.20impls), this PR:
- adds a new `BuiltinImplSource::Trivial` source, and marks the `Sized` builtin impls as trivial
- prefers these trivial builtin impls in `merge_trait_candidates`
The comments can likely be wordsmithed a bit better, and I ~stole~ was inspired by the old solver ones. Let me know how you want them improved.
When enabling the new solver for tests, 3 UI tests now pass:
- `regions/issue-26448-1.rs` and its sibling `regions/issue-26448-2.rs` were rejected by the new solver but accepted by the old one
- and `issues/issue-42796.rs` where the old solver emitted some overflow errors in addition to the expected error
(For some reason one of these tests is run-pass, but I can take care of that another day)
r? lcnr
