Remove support for `dyn*` from the compiler
This PR removes support for `dyn*` (https://github.com/rust-lang/rust/issues/102425), which are a currently un-RFC'd experiment that was opened a few years ago to explore a component that we thought was necessary for AFIDT (async fn in dyn trait).
It doesn't seem like we are going to need `dyn*` types -- even in an not-exposed-to-the-user way[^1] -- for us to implement AFIDT. Given that AFIDT was the original motivating purpose of `dyn*` types, I don't really see a compelling reason to have to maintain their implementation in the compiler.
[^1]: Compared to, e.g., generators whih are an unstable building block we use to implement stable syntax like `async {}`.
We've learned quite a lot from `dyn*`, but I think at this point its current behavior leads to more questions than answers. For example, `dyn*` support today remains somewhat fragile; it ICEs in many cases where the current "normal" `dyn Trait` types rely on their unsizedness for their vtable-based implementation to be sound I wouldn't be surprised if it's unsound in other ways, though I didn't play around with it too much. See the examples below.
```rust
#![feature(dyn_star)]
trait Foo {
fn hello(self);
}
impl Foo for usize {
fn hello(self) {
println!("hello, world");
}
}
fn main() {
let x: dyn* Foo = 1usize;
x.hello();
}
```
And:
```rust
#![feature(dyn_star)]
trait Trait {
type Out where Self: Sized;
}
fn main() {
let x: <dyn* Trait as Trait>::Out;
}
```
...and probably many more problems having to do with the intersection of dyn-compatibility and `Self: Sized` bounds that I was too lazy to look into like:
* GATs
* Methods with invalid signatures
* Associated consts
Generally, `dyn*` types also end up getting in the way of working with [normal `dyn` types](https://github.com/rust-lang/rust/issues/102425#issuecomment-1712604409) to an extent that IMO outweighs the benefit of experimentation.
I recognize that there are probably other, more creative usages of `dyn*` that are orthogonal to AFIDT. However, I think any work along those lines should first have to think through some of the more fundamental interactions between `dyn*` and dyn-compatibility before we think about reimplementing them in the type system.
---
I'm planning on removing the `DynKind` enum and the `PointerLike` built-in trait from the compiler after this PR lands.
Closesrust-lang/rust#102425.
cc `@eholk` `@rust-lang/lang` `@rust-lang/types`
Closesrust-lang/rust#116979.
Closesrust-lang/rust#119694.
Closesrust-lang/rust#134591.
Closesrust-lang/rust#104800.
Rollup of 12 pull requests
Successful merges:
- rust-lang/rust#136801 (Implement `Random` for tuple)
- rust-lang/rust#141867 (Describe Future invariants more precisely)
- rust-lang/rust#142760 (docs(fs): Touch up grammar on lock api)
- rust-lang/rust#143181 (Improve testing and error messages for malformed attributes)
- rust-lang/rust#143210 (`tests/ui`: A New Order [19/N] )
- rust-lang/rust#143212 (`tests/ui`: A New Order [20/N])
- rust-lang/rust#143230 ([COMPILETEST-UNTANGLE 2/N] Make some compiletest errors/warnings/help more visually obvious)
- rust-lang/rust#143240 (Port `#[rustc_object_lifetime_default]` to the new attribute parsing …)
- rust-lang/rust#143255 (Do not enable LLD by default in the dist profile)
- rust-lang/rust#143262 (mir: Mark `Statement` and `BasicBlockData` as `#[non_exhaustive]`)
- rust-lang/rust#143269 (bootstrap: make comment more clear)
- rust-lang/rust#143279 (Remove `ItemKind::descr` method)
Failed merges:
- rust-lang/rust#143237 (Port `#[no_implicit_prelude]` to the new attribute parsing infrastructure)
r? `@ghost`
`@rustbot` modify labels: rollup
Remove `ItemKind::descr` method
Follow-up of rust-lang/rust#143234.
After this PR is merged, it will remain two `descr` methods:
* `hir::GenericArg::descr`
* `hir::AssocItemConstraintKind::descr`
For both these enums, I don't think there is the right equivalent in `hir::DefKind` so unless I missed something, we can't remove these two methods because we can't convert these enums into `hir::DefKind`.
r? `@oli-obk`
`tests/ui`: A New Order [20/N]
> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? `@tgross35`
`tests/ui`: A New Order [19/N]
> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? `@tgross35`
Start moving wf checking away from HIR
I'm trying to only access the HIR in the error path. My hope is that once we move significant portions of wfcheck off HIR that incremental will be able to cache wfcheck queries significantly better.
I think I am reaching a blocker because we normally need to provide good spans to `ObligationCause`, so that the trait solver can report good errors. In some cases I have been able to use bad spans and improve them depending on the `ObligationCauseCode` (by loading HIR in the case where we actually want to error). To scale that further we'll likely need to remove spans from the `ObligationCause` entirely (leaving it to some variants of `ObligationCauseCode` to have a span when they can't recompute the information later). Unsure this is the right approach, but we've already been using it. I will create an MCP about it, but that should not affect this PR, which is fairly limited in where it does those kind of tricks.
Especially b862d8828e is interesting here, because I think it improves spans in all cases
Port `#[rustc_layout_scalar_valid_range_start/end]` to the new attrib…
Ports `rustc_layout_scalar_valid_range_start` and `rustc_layout_scalar_valid_range_end` to the new attribute parsing infrastructure for https://github.com/rust-lang/rust/issues/131229#issuecomment-2971353197
r? `@jdonszelmann`
fix: Emit suggestion filename if primary diagnostic span is dummy
While working on using `annotate-snippets` as `rustc`'s emitter, I came across [`tests/ui/resolve/resolve-conflict-extern-crate-vs-extern-crate.stderr`](b03b3a7ec9/tests/ui/resolve/resolve-conflict-extern-crate-vs-extern-crate.stderr), which lacked a filename for both the annotation and the suggestion, which seemed like a bug to me. After some investigation, I found that this is happening because the primary span is a dummy, so its filename doesn't get output, and its filename matches the one for the suggestion, so the suggestion's filename doesn't get output. To fix this issue, I made it so that the filename for a suggestion will get output if the primary span is a dummy.
Replace `ItemCtxt::report_placeholder_type_error` match with a call to `TyCtxt::def_descr`
Fixesrust-lang/rust#143128.
We could likely use `tcx.def_descr` in more places (and therefore remove more `descr` methods). If it's something that we want to do, I can send a follow-up.
r? `@oli-obk`
inherit `#[align]` from trait method prototypes
````@workingjubilee```` this seems straightforward enough. Now that we're planning to make `-Cmin-function-alignment` a target modifier, I don't think there are any cross-crate complications here?
````@Jules-Bertholet```` is this the behavior you had in mind? In particular the inheritance of the attribute of a default impl is maybe a bit unintuitive at first? (but I think it's ok if that behavior is explicitly documented).
r? ghost
`syntax-errors` currently contains both syntax error tests (which don't
need expansion) and tests for incorrect instantiations of the `count`
metavariable expression (which do need expansion). Split the
expansion-dependent tests to a separate file and remove unneeded
invocations from `syntax-errors`, to ensure we are catching these before
expansion.
`tests/ui`: A New Order [17/N]
> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? `@tgross35`
`tests/ui`: A New Order [16/N]
> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? `@tgross35`
(just small one to test new method, also I should squash all this commits except move commit, so we after review will end up having like one move commit and one commit with changes, right?)
Do not freshen `ReError`
Because `ReError` has `ErrorGuaranteed` in it, it affects candidate selection and thus causes incompleteness which leads to weirdness in eval. See the comment in the test.
Also remove an unnecessary `lookup_op_method` since it doesn't effect tests.
Fixesrust-lang/rust#132882.
r? types
`tests/ui`: A New Order [15/N]
> [!NOTE]
>
> Intermediate commits are intended to help review, but will be squashed prior to merge.
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? `@jieyouxu`
`tests/ui`: A New Order [13/N]
Some `tests/ui/` housekeeping, to trim down number of tests directly under `tests/ui/`. Part of rust-lang/rust#133895.
r? ```@jieyouxu```
With a long macro name that could fit on one line, but currently isn't
formatted that way, because the name would overlap with the maximum
width of the "Uses" column. (The next commit will fix this.)
