Introduce CoerceShared lang item and trait, and basic Reborrow tests #146037
Conversation
|
r? @nnethercote rustbot has assigned @nnethercote. Use |
rustbot
added
S-waiting-on-review
|
The definition I use of a marker trait is a trait with no items, so this would not be a marker trait. (This concept comes up in regards to coherence; it is sound to allow overlapping impls of marker traits, because they don't have items whose definitions can conflict.) |
Alright; I was kind of just following CoercePointee since the names are similar :D Would this be more appropriate in ops perhaps? Or somewhere else entirely? |
|
This looks fine to me from the compiler side, where very little code is added. Any controversial bits seems to be libs/lang related, where I don't have much insight. I will forward this review on to Tyler who knows more about it. I'm not sure if a library reviewer should also be involved. r? @tmandry |
aapoalas
force-pushed
the
reborrow-lang-experiment
branch
from
fb6acfa to
c4a87eb
Compare
|
This PR was rebased onto a different master commit. Here's a range-diff highlighting what actually changed. Rebasing is a normal part of keeping PRs up to date, so no action is needed—this note is just to help reviewers. |
Moved the trait to Reborrow as we talked on Thursday. |
| //~| NOTE arguments to this function are incorrect | ||
| //~| NOTE types differ in mutability | ||
| //~| NOTE expected struct `Pin<&()>` | ||
| //~| NOTE found struct `Pin<&mut ()>` |
There was a problem hiding this comment.
This seems like a lot of notes which makes the test more brittle. Maybe only "types differ in mutability" is needed?
There was a problem hiding this comment.
I couldn't remove these; the test indeed does need them to pass.
|
@bors delegate+ r=me after comments. |
bors
added
S-waiting-on-bors
… r=tmandry Introduce CoerceShared lang item and trait, and basic Reborrow tests Part of rust-lang#145612: This introduces the `CoerceShared` trait which is the `Reborrow` equivalent of a `&mut T` -> `&T` coercion. The trait has a `Target` GAT which makes this (currently) unique in the `core/src/marker.rs`; I'm not sure if this can be considered problematic. Maybe this is not the way such things should be done at the marker trait level? Or maybe it is fine. Improtantly, this PR introduces a battery of basic `Reborrow` and `CoerceShared` tests. These test the very basics of the feature; custom marker types intended to have exclusive semantics (`Custom<'a>(PhantomData<&'a mut ()>)`), custom exclusive reference wrappers, and standard library exclusive reference wrappers (`Pin<&mut T>` and `Option<&mut T>`). None of these of course work since the implementation for `Reborrow` and `CoerceShared` is entirely missing, but this is the first step towards making these work. Future PRs will introduce more tests, such as "recursive" reborrowing (ie. reborrowing structs that contain multiple reborrowable fields) and checks around the lifetime semantics of reborrowing ie. that a reborrow produces a new type with the same lifetime as the original.
Rollup of 9 pull requests Successful merges: - #140482 (std::net: update tcp deferaccept delay type to Duration.) - #146037 (Introduce CoerceShared lang item and trait, and basic Reborrow tests) - #146732 (tests: relax expectations after llvm change 902ddda120a5) - #147018 (re-order normalizations in run-make linker-warning test) - #147032 (Fix doctest compilation time display) - #147046 (Rename `rust.use-lld` to `rust.bootstrap-override-lld`) - #147050 (PassWrapper: update for new PGOOptions args in LLVM 22) - #147075 (Make `def_path_hash_to_def_id` not panic when passed an invalid hash) - #147076 (update issue number for more_float_constants) r? `@ghost` `@rustbot` modify labels: rollup
Rollup of 8 pull requests Successful merges: - #146037 (Introduce CoerceShared lang item and trait, and basic Reborrow tests) - #146732 (tests: relax expectations after llvm change 902ddda120a5) - #147018 (re-order normalizations in run-make linker-warning test) - #147032 (Fix doctest compilation time display) - #147046 (Rename `rust.use-lld` to `rust.bootstrap-override-lld`) - #147050 (PassWrapper: update for new PGOOptions args in LLVM 22) - #147075 (Make `def_path_hash_to_def_id` not panic when passed an invalid hash) - #147076 (update issue number for more_float_constants) r? `@ghost` `@rustbot` modify labels: rollup
Rollup merge of #146037 - aapoalas:reborrow-lang-experiment, r=tmandry Introduce CoerceShared lang item and trait, and basic Reborrow tests Part of #145612: This introduces the `CoerceShared` trait which is the `Reborrow` equivalent of a `&mut T` -> `&T` coercion. The trait has a `Target` GAT which makes this (currently) unique in the `core/src/marker.rs`; I'm not sure if this can be considered problematic. Maybe this is not the way such things should be done at the marker trait level? Or maybe it is fine. Improtantly, this PR introduces a battery of basic `Reborrow` and `CoerceShared` tests. These test the very basics of the feature; custom marker types intended to have exclusive semantics (`Custom<'a>(PhantomData<&'a mut ()>)`), custom exclusive reference wrappers, and standard library exclusive reference wrappers (`Pin<&mut T>` and `Option<&mut T>`). None of these of course work since the implementation for `Reborrow` and `CoerceShared` is entirely missing, but this is the first step towards making these work. Future PRs will introduce more tests, such as "recursive" reborrowing (ie. reborrowing structs that contain multiple reborrowable fields) and checks around the lifetime semantics of reborrowing ie. that a reborrow produces a new type with the same lifetime as the original.
… r=tmandry Introduce CoerceShared lang item and trait, and basic Reborrow tests Part of rust-lang#145612: This introduces the `CoerceShared` trait which is the `Reborrow` equivalent of a `&mut T` -> `&T` coercion. The trait has a `Target` GAT which makes this (currently) unique in the `core/src/marker.rs`; I'm not sure if this can be considered problematic. Maybe this is not the way such things should be done at the marker trait level? Or maybe it is fine. Improtantly, this PR introduces a battery of basic `Reborrow` and `CoerceShared` tests. These test the very basics of the feature; custom marker types intended to have exclusive semantics (`Custom<'a>(PhantomData<&'a mut ()>)`), custom exclusive reference wrappers, and standard library exclusive reference wrappers (`Pin<&mut T>` and `Option<&mut T>`). None of these of course work since the implementation for `Reborrow` and `CoerceShared` is entirely missing, but this is the first step towards making these work. Future PRs will introduce more tests, such as "recursive" reborrowing (ie. reborrowing structs that contain multiple reborrowable fields) and checks around the lifetime semantics of reborrowing ie. that a reborrow produces a new type with the same lifetime as the original.
5 participants
Part of #145612: This introduces the
CoerceSharedtrait which is theReborrowequivalent of a&mut T->&Tcoercion. The trait has aTargetGAT which makes this (currently) unique in thecore/src/marker.rs; I'm not sure if this can be considered problematic. Maybe this is not the way such things should be done at the marker trait level? Or maybe it is fine.Improtantly, this PR introduces a battery of basic
ReborrowandCoerceSharedtests. These test the very basics of the feature; custom marker types intended to have exclusive semantics (Custom<'a>(PhantomData<&'a mut ()>)), custom exclusive reference wrappers, and standard library exclusive reference wrappers (Pin<&mut T>andOption<&mut T>). None of these of course work since the implementation forReborrowandCoerceSharedis entirely missing, but this is the first step towards making these work.Future PRs will introduce more tests, such as "recursive" reborrowing (ie. reborrowing structs that contain multiple reborrowable fields) and checks around the lifetime semantics of reborrowing ie. that a reborrow produces a new type with the same lifetime as the original.