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#[lang_item] for core::ptr::Unique #112662

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merged 1 commit into from Jun 17, 2023
Merged

#[lang_item] for core::ptr::Unique #112662

merged 1 commit into from Jun 17, 2023

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Vanille-N
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@Vanille-N Vanille-N commented Jun 15, 2023 •
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Tree Borrows is about to introduce experimental special handling of core::ptr::Unique in Miri to give it a semantics.
As of now there does not seem to be a clean way (i.e. other than &format!("{adt:?}") == "std::ptr::Unique") to check if an AdtDef represents a Unique.

r? @RalfJung

Draft: making a lang item

@rustbot rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 15, 2023
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Are you using this just for diagnostics, or is correctness in Miri dependent on always being able to know what a Unique is? If the latter, perhaps this should be a lang item instead.

@RalfJung
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RalfJung commented Jun 15, 2023 via email •
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@compiler-errors
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No, they're compiler-internal details so there's no stability guarantee or anything, not that that would matter for Miri or anything. I think my approval should be sufficient.

@RalfJung
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Okay, in that case -- @Vanille-N looks like I guessed wrong and a lang item is preferable here. Sorry for that.

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My understanding is that both the compiler and tools should work, perhaps with degraded diagnostics, if all diagnostic items are stripped from the standard library -- but the compiler (and by extension, compiler-adjacent tools) should be allowed to depend on the existence and well-formedness of a lang item. We don't expect the compiler to work the lang = "copy" is stripped, but we do if rustc_diagnostic_item = "RefCell" is.

@Nilstrieb
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yeah, branching on the happy path should be a lang item
(Ideally also with a comment inside core explaining that it's used experimentally inside Miri)

@compiler-errors compiler-errors self-assigned this Jun 15, 2023
@Vanille-N Vanille-N marked this pull request as draft June 15, 2023 18:34
@Vanille-N
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This seems to be the minimum needed for use by Miri, but there's probably more that should be added.

  • should it get some GenericRequirement other than None ?
  • should mini_core.rs inside rustc_codegen_{cranelift,gcc} get it as well ?
  • test usage ? I'll save the full PR on semantics of Unique for the miri repository, but maybe I should add here a simple test that the lang item is recognized.

This compiles after some --stage 1 --keep-stage 0 manipulations, but I'm not even sure it'll pass the CI checks.

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@RalfJung
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This seems to be the minimum needed for use by Miri, but there's probably more that should be added.

* should it get some `GenericRequirement` other than `None` ?

I wouldn't worry about it, None is fine.

* should `mini_core.rs` inside `rustc_codegen_{cranelift,gcc}` get it as well ?

No, the lang item doesn't have to exist.

* test usage ? I'll save the full PR on semantics of `Unique` for the miri repository, but maybe I should add here a simple test that the lang item is recognized.

How would you test this, other than implementing Unique semantics?

@Vanille-N Vanille-N changed the title rustc_diagnostic_item for core::ptr::Unique #[lang_item] for core::ptr::Unique Jun 16, 2023
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it has one generic parameter, just use Exact(1)

@RalfJung
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LGTM, please squash the commits then we can land this. :)

@Vanille-N Vanille-N marked this pull request as ready for review June 16, 2023 15:12
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@bors r=RalfJung

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bors commented Jun 16, 2023

📌 Commit dc3e91c has been approved by RalfJung

It is now in the queue for this repository.

@bors bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jun 16, 2023
@compiler-errors compiler-errors mentioned this pull request Jun 16, 2023
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bors added a commit to rust-lang-ci/rust that referenced this pull request Jun 16, 2023
@bors
Auto merge of rust-lang#112716 - compiler-errors:rollup-h77daia, r=co…
670a0ed 
…mpiler-errors

Rollup of 7 pull requests

Successful merges:

 - rust-lang#111074 (Relax implicit `T: Sized` bounds on `BufReader<T>`, `BufWriter<T>` and `LineWriter<T>`)
 - rust-lang#112226 (std: available_parallelism using native netbsd api first)
 - rust-lang#112474 (Support 128-bit enum variant in debuginfo codegen)
 - rust-lang#112662 (`#[lang_item]` for `core::ptr::Unique`)
 - rust-lang#112665 (Make assumption functions in new solver take `Binder<'tcx, Clause<'tcx>>`)
 - rust-lang#112684 (Disable alignment checks on i686-pc-windows-msvc)
 - rust-lang#112706 (Add `SyntaxContext::is_root`)

r? `@ghost`
`@rustbot` modify labels: rollup
@bors bors merged commit 38fc6be into rust-lang:master Jun 17, 2023
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@rustbot rustbot added this to the 1.72.0 milestone Jun 17, 2023
@Vanille-N Vanille-N mentioned this pull request Jun 20, 2023
Merged
compiler-errors added a commit to compiler-errors/rust that referenced this pull request Jun 20, 2023
@compiler-errors
Rollup merge of rust-lang#112844 - Vanille-N:unique, r=RalfJung
3dd1406 
Add retag in MIR transform: `Adt` for `Unique` may contain a reference

Following rust-lang#112662 , `may_contain_reference` in `rustc_mir_transform::add_retag` underapproximates too much the types that require retagging.

r? `@RalfJung`
Nilstrieb added a commit to Nilstrieb/rust that referenced this pull request Jun 21, 2023
@Nilstrieb
Rollup merge of rust-lang#112844 - Vanille-N:unique, r=RalfJung
82e6a16 
Add retag in MIR transform: `Adt` for `Unique` may contain a reference

Following rust-lang#112662 , `may_contain_reference` in `rustc_mir_transform::add_retag` underapproximates too much the types that require retagging.

r? ``@RalfJung``
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