fix(generic_const_exprs): Fix predicate inheritance for children of opaque types by PixelDust22 · Pull Request #99801 · rust-lang/rust

PixelDust22 · 2022-07-27T09:31:08Z

We currently have a special case to perform predicate inheritance when the const item is in the generics. I think we're also going to need this for opaque return types. When evaluating the predicates applied to the associated item, it'll inherit from its parent, the opaque type, which will never have predicates applied. This PR bypass the opaque typed parent and inherit predicates directly from the function itself.

rust-highfive · 2022-07-27T09:31:11Z

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @compiler-errors (or someone else) soon.

Please see the contribution instructions for more information.

PixelDust22 · 2022-07-27T09:32:39Z

r? @BoxyUwU

PixelDust22 · 2022-07-27T21:39:03Z

@rustbot label +A-const-generics +F-generic_const_exprs

BoxyUwU · 2022-07-28T05:23:51Z

I suspect this probably doesnt work right for -> impl Foo<Assoc = impl Bar = Baz<{ T::ASSOC }>>. I am not that familiar with opaque type stuff so going to r? @oli-obk

oli-obk · 2022-07-28T07:20:11Z

I think this will get resolved by @spastorino's work which removes this parent generics behaviour of return position impl trait. This PR is just more proof that doing that is important. It feels like a band-aid that I would prefer not to merge

PixelDust22 · 2022-07-28T08:43:28Z

@oli-obk Sure, I'm OK with closing this for now and wait for the RPIT refactor to happen. Do you have a pointer to where that is happening & the timeline? Just want to get this bug properly documented here so that other people don't end up wasting time on this.

oli-obk · 2022-07-28T08:57:52Z

I don't know where @spastorino is tracking this work. I'll let him post a link in case there's a hackmd.

We could link #99705 from the generic_const_exprs tracking issue so it doesn't get lost.

PixelDust22 · 2022-07-28T17:16:59Z

Ok sounds good. Let's keep this PR open in the mean time so that those who need this now can use the branch as a custom toolchain.

spastorino · 2022-08-11T17:58:12Z

For some reason I've missed this one. Anyway, my changes are close to be completed. Right now I'm fixing some bugs on my branch.

spastorino · 2022-09-08T12:01:36Z

PR with RPIT changes is now up #101345, we still need to address some problems that crater have found.

bors · 2022-09-27T13:43:05Z

☔ The latest upstream changes (presumably #102306) made this pull request unmergeable. Please resolve the merge conflicts.

pnkfelix · 2022-10-27T14:54:33Z

discussed in T-compiler triage meeting.

reassigning ownership for design decisions here to T-types.

@rustbot label: -T-compiler +T-types

oli-obk · 2022-10-31T15:30:55Z

I think we should "just do this PR" and remove the changes when we'll actually change the opaque type parenting logic.

So... after much work that didn't get merged after all, @Neo-Zhixing can you rebase this PR, we can then merge it.

PixelDust22 · 2022-10-31T22:17:57Z

@oli-obk changes merged with master. Thanks!

compiler-errors · 2022-10-31T23:27:29Z

@Neo-Zhixing we don't actually allow merge conflicts in the rust repo: https://rustc-dev-guide.rust-lang.org/git.html#no-merge-policy

Can you rebase this commit instead?

PixelDust22 · 2022-11-01T00:04:13Z

My apologies, I thought GitHub would be able to squash those commits for you.
Rebased. Thanks @compiler-errors

oli-obk · 2022-11-01T08:44:38Z

@bors r+

bors · 2022-11-01T08:44:40Z

📌 Commit ccd9e07281b43567de28ad9f6601c49464e44bd6 has been approved by oli-obk

It is now in the queue for this repository.

BoxyUwU · 2022-11-01T08:58:49Z

did we test if -> impl Foo<Assoc = impl Bar<{ T::ASSOC }>> is fixed by this PR?

#![feature(generic_const_exprs)]traitFoo{typeAssoc;}traitBar<constN:usize>{}implFoofor(){typeAssoc = ();}impl<constN:usize>Bar<N>for(){}traitTrait{constASSOC:usize;}fnfoo<T:Trait>() -> implFoo<Assoc = implBar<{T::ASSOC}>>{}

oli-obk · 2022-11-01T10:34:58Z

@bors r- let's add the test, but I think it should work

PixelDust22 · 2022-11-01T22:35:49Z

@rustbot label -S-waiting-on-author +S-waiting-on-review
@oli-obk @BoxyUwU Test added for the nested impl. Indeed it works! Thanks

…paque types

oli-obk · 2022-11-02T15:11:09Z

@bors r+

bors · 2022-11-02T15:11:11Z

📌 Commit 744fa61 has been approved by oli-obk

It is now in the queue for this repository.

BoxyUwU · 2022-11-02T15:44:39Z

Is there no way to get nested opaque items in current rustc 🤔 that was what i was going for with -> impl Trait<Assoc = impl Other<{ T::ASSOC }>>. Judging by the fact that the code i posted compiles it kind of implies that is nested opaques so I am slightly confused as to how this PR fixes that ✨

oli-obk · 2022-11-02T16:07:14Z

Is there no way to get nested opaque items in current rustc

yes there is. Your example does indeed show that, but it's not an issue because the inner opaque item fetches the predicates of the outer one, which fetches it from the function.

BoxyUwU · 2022-11-02T17:34:52Z

I thought the bug was that opaque type items dont have all the predicates of the parent, so anon consts inheriting predicates from the opaque is incorrect since they should have "all" of them. Clearly i've misunderstood something here since if that was true the anon const having a parent of the outter opaque type would not be correct 😅

…iaskrgr Rollup of 6 pull requests Successful merges: - rust-lang#99801 (fix(generic_const_exprs): Fix predicate inheritance for children of opaque types) - rust-lang#103610 (Allow use of `-Clto=thin` with `-Ccodegen-units=1` in general) - rust-lang#103870 (Fix `inferred_kind` ICE) - rust-lang#103875 (Simplify astconv item def id handling) - rust-lang#103886 (rustdoc: Fix merge of attributes for reexports of local items) - rust-lang#103890 (rustdoc: remove unused mobile CSS `.rustdoc { padding-top: 0 }`) Failed merges: - rust-lang#103884 (Add visit_fn_ret_ty to hir intravisit) r? `@ghost` `@rustbot` modify labels: rollup

bors · 2022-11-03T03:01:07Z

⌛ Testing commit 744fa61 with merge 96787c4...

…-ct, r=BoxyUwU Resolve anon const's parent predicates to direct parent instead of opaque's parent When an anon const is inside of an opaque, rust-lang#99801 added a hack to resolve the anon const's parent predicates *not* to the opaque's predicates, but to the opaque's *parent's* predicates. This is insufficient when considering nested opaques. This means that the `predicates_of` an anon const might reference duplicated lifetimes (installed by `compute_bidirectional_outlives_predicates`) when computing known outlives in MIR borrowck, leading to these ICEs: Fixesrust-lang#121574Fixesrust-lang#118403 ~~Instead, we should be using the `OpaqueTypeOrigin` to acquire the owner item (fn/type alias/etc) of the opaque, whose predicates we're fine to mention.~~ ~~I think it's a bit sketchy that we're doing this at all, tbh; I think it *should* be fine for the anon const to inherit the predicates of the opaque it's located inside. However, that would also mean that we need to make sure the `generics_of` that anon const line up in the same way.~~ ~~None of this is important to solve right now; I just want to fix these ICEs so we can land rust-lang#125468, which accidentally fixes these issues in a different and unrelated way.~~ edit: We don't need this special case anyways because we install the right parent item in `generics_of` anyways: https://github.com/rust-lang/rust/blob/213ad10c8f0fc275648552366275dc4e07f97462/compiler/rustc_hir_analysis/src/collect/generics_of.rs#L150 r? `@BoxyUwU`

Rollup merge of rust-lang#125501 - compiler-errors:opaque-opaque-anon-ct, r=BoxyUwU Resolve anon const's parent predicates to direct parent instead of opaque's parent When an anon const is inside of an opaque, rust-lang#99801 added a hack to resolve the anon const's parent predicates *not* to the opaque's predicates, but to the opaque's *parent's* predicates. This is insufficient when considering nested opaques. This means that the `predicates_of` an anon const might reference duplicated lifetimes (installed by `compute_bidirectional_outlives_predicates`) when computing known outlives in MIR borrowck, leading to these ICEs: Fixesrust-lang#121574Fixesrust-lang#118403 ~~Instead, we should be using the `OpaqueTypeOrigin` to acquire the owner item (fn/type alias/etc) of the opaque, whose predicates we're fine to mention.~~ ~~I think it's a bit sketchy that we're doing this at all, tbh; I think it *should* be fine for the anon const to inherit the predicates of the opaque it's located inside. However, that would also mean that we need to make sure the `generics_of` that anon const line up in the same way.~~ ~~None of this is important to solve right now; I just want to fix these ICEs so we can land rust-lang#125468, which accidentally fixes these issues in a different and unrelated way.~~ edit: We don't need this special case anyways because we install the right parent item in `generics_of` anyways: https://github.com/rust-lang/rust/blob/213ad10c8f0fc275648552366275dc4e07f97462/compiler/rustc_hir_analysis/src/collect/generics_of.rs#L150 r? `@BoxyUwU`

rust-highfive assigned compiler-errors Jul 27, 2022

rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Jul 27, 2022

rust-highfive added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Jul 27, 2022

rust-highfive assigned BoxyUwU and unassigned compiler-errors Jul 27, 2022

rustbot added A-const-generics Area: const generics (parameters and arguments) F-generic_const_exprs `#![feature(generic_const_exprs)]` labels Jul 27, 2022

rust-highfive assigned oli-obk and unassigned BoxyUwU Jul 28, 2022

PixelDust22 mentioned this pull request Jul 28, 2022
No associated item found when the associated item was used as const generic parameter in return type #99705
Closed

oli-obk added the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Jul 29, 2022

rustbot added T-types Relevant to the types team, which will review and decide on the PR/issue. and removed T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. labels Oct 27, 2022

oli-obk removed the S-blocked Status: Blocked on something else such as an RFC or other implementation work. label Oct 27, 2022

PixelDust22 force-pushed the fix/generic_const_exprs_parent_opaque_predicates branch from 25a0dd5 to ccd9e07Compare November 1, 2022 00:02

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 Nov 1, 2022

bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Nov 1, 2022

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Nov 1, 2022

fix(generic_const_exprs): Fix predicate inheritance for children of o…
744fa61
…paque types

PixelDust22 force-pushed the fix/generic_const_exprs_parent_opaque_predicates branch from a553575 to 744fa61Compare November 1, 2022 22:41

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 Nov 2, 2022

matthiaskrgr mentioned this pull request Nov 2, 2022
Rollup of 6 pull requests #103903
Merged

bors merged commit 214d6b6 into rust-lang:masterNov 3, 2022

rustbot added this to the 1.67.0 milestone Nov 3, 2022

compiler-errors mentioned this pull request May 24, 2024
Resolve anon const's parent predicates to direct parent instead of opaque's parent #125501
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