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-Znext-solver instantiate predicate binder without recanonicalizing goal
#146725
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changes to Some changes occurred to the core trait solver cc @rust-lang/initiative-trait-system-refactor |
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-Znext-solver instantiate predicate binder without recanonicalizing goal
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@rfcbot fcp merge |
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Team member @lcnr has proposed to merge this. The next step is review by the rest of the tagged team members: No concerns currently listed. Once a majority of reviewers approve (and at most 2 approvals are outstanding), this will enter its final comment period. If you spot a major issue that hasn't been raised at any point in this process, please speak up! See this document for info about what commands tagged team members can give me. |
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@bors rollup=never |
| ty::PredicateKind::Ambiguous => { | ||
| self.evaluate_added_goals_and_make_canonical_response(Certainty::AMBIGUOUS) | ||
| } | ||
| self.enter_forall(kind, |ecx, kind| match kind { |
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much cleaner, nice :>
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🔔 This is now entering its final comment period, as per the review above. 🔔 |
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Finished benchmarking commit (e5a41b8): comparison URL. Overall result: ❌✅ regressions and improvements - no action neededBenchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf. @bors rollup=never Instruction countOur most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.
Max RSS (memory usage)Results (secondary 3.9%)A less reliable metric. May be of interest, but not used to determine the overall result above.
CyclesResults (secondary 4.4%)A less reliable metric. May be of interest, but not used to determine the overall result above.
Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 473.415s -> 471.736s (-0.35%) |
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r=me if CI passes |
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@bors r=BoxyUwU |
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☀️ Test successful - checks-actions |
What is this?This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.Comparing 695857b (parent) -> 37ec98f (this PR) Test differencesShow 21 test diffsStage 1
Stage 2
Additionally, 15 doctest diffs were found. These are ignored, as they are noisy. Job group index
Test dashboardRun cargo run --manifest-path src/ci/citool/Cargo.toml -- \
test-dashboard 37ec98f5d33c0876a9ffa5ee17dc0895659efe37 --output-dir test-dashboardAnd then open Job duration changes
How to interpret the job duration changes?Job durations can vary a lot, based on the actual runner instance |
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Finished benchmarking commit (37ec98f): comparison URL. Overall result: ✅ improvements - no action needed@rustbot label: -perf-regression Instruction countOur most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.
Max RSS (memory usage)Results (primary -0.8%)A less reliable metric. May be of interest, but not used to determine the overall result above.
CyclesThis benchmark run did not return any relevant results for this metric. Binary sizeThis benchmark run did not return any relevant results for this metric. Bootstrap: 472.072s -> 472.516s (0.09%) |
This MR contains the following updates: | Package | Update | Change | |---|---|---| | [rust](https://github.com/rust-lang/rust) | minor | `1.91.1` -> `1.92.0` | MR created with the help of [el-capitano/tools/renovate-bot](https://gitlab.com/el-capitano/tools/renovate-bot). **Proposed changes to behavior should be submitted there as MRs.** --- ### Release Notes <details> <summary>rust-lang/rust (rust)</summary> ### [`v1.92.0`](https://github.com/rust-lang/rust/blob/HEAD/RELEASES.md#Version-1920-2025-12-11) [Compare Source](rust-lang/rust@1.91.1...1.92.0) \========================== <a id="1.92.0-Language"></a> ## Language - [Document `MaybeUninit` representation and validity](rust-lang/rust#140463) - [Allow `&raw [mut | const]` for union field in safe code](rust-lang/rust#141469) - [Prefer item bounds of associated types over where-bounds for auto-traits and `Sized`](rust-lang/rust#144064) - [Do not materialize `X` in `[X; 0]` when `X` is unsizing a const](rust-lang/rust#145277) - [Support combining `#[track_caller]` and `#[no_mangle]` (requires every declaration specifying `#[track_caller]` as well)](rust-lang/rust#145724) - [Make never type lints `never_type_fallback_flowing_into_unsafe` and `dependency_on_unit_never_type_fallback` deny-by-default](rust-lang/rust#146167) - [Allow specifying multiple bounds for same associated item, except in trait objects](rust-lang/rust#146593) - [Slightly strengthen higher-ranked region handling in coherence](rust-lang/rust#146725) - [The `unused_must_use` lint no longer warns on `Result<(), Uninhabited>` (for instance, `Result<(), !>`), or `ControlFlow<Uninhabited, ()>`](rust-lang/rust#147382). This avoids having to check for an error that can never happen. <a id="1.92.0-Compiler"></a> ## Compiler - [Make `mips64el-unknown-linux-muslabi64` link dynamically](rust-lang/rust#146858) - [Remove current code for embedding command-line args in PDB](rust-lang/rust#147022) Command-line information is typically not needed by debugging tools, and the removed code was causing problems for incremental builds even on targets that don't use PDB debuginfo. <a id="1.92.0-Libraries"></a> ## Libraries - [Specialize `Iterator::eq{_by}` for `TrustedLen` iterators](rust-lang/rust#137122) - [Simplify `Extend` for tuples](rust-lang/rust#138799) - [Added details to `Debug` for `EncodeWide`](rust-lang/rust#140153). - [`iter::Repeat::last`](rust-lang/rust#147258) and [`count`](rust-lang/rust#146410) will now panic, rather than looping infinitely. <a id="1.92.0-Stabilized-APIs"></a> ## Stabilized APIs - [`NonZero<u{N}>::div_ceil`](https://doc.rust-lang.org/stable/std/num/struct.NonZero.html#method.div_ceil) - [`Location::file_as_c_str`](https://doc.rust-lang.org/stable/std/panic/struct.Location.html#method.file_as_c_str) - [`RwLockWriteGuard::downgrade`](https://doc.rust-lang.org/stable/std/sync/struct.RwLockWriteGuard.html#method.downgrade) - [`Box::new_zeroed`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.new_zeroed) - [`Box::new_zeroed_slice`](https://doc.rust-lang.org/stable/std/boxed/struct.Box.html#method.new_zeroed_slice) - [`Rc::new_zeroed`](https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.new_zeroed) - [`Rc::new_zeroed_slice`](https://doc.rust-lang.org/stable/std/rc/struct.Rc.html#method.new_zeroed_slice) - [`Arc::new_zeroed`](https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.new_zeroed) - [`Arc::new_zeroed_slice`](https://doc.rust-lang.org/stable/std/sync/struct.Arc.html#method.new_zeroed_slice) - [`btree_map::Entry::insert_entry`](https://doc.rust-lang.org/stable/std/collections/btree_map/enum.Entry.html#method.insert_entry) - [`btree_map::VacantEntry::insert_entry`](https://doc.rust-lang.org/stable/std/collections/btree_map/struct.VacantEntry.html#method.insert_entry) - [`impl Extend<proc_macro::Group> for proc_macro::TokenStream`](https://doc.rust-lang.org/stable/proc_macro/struct.TokenStream.html#impl-Extend%3CGroup%3E-for-TokenStream) - [`impl Extend<proc_macro::Literal> for proc_macro::TokenStream`](https://doc.rust-lang.org/stable/proc_macro/struct.TokenStream.html#impl-Extend%3CLiteral%3E-for-TokenStream) - [`impl Extend<proc_macro::Punct> for proc_macro::TokenStream`](https://doc.rust-lang.org/stable/proc_macro/struct.TokenStream.html#impl-Extend%3CPunct%3E-for-TokenStream) - [`impl Extend<proc_macro::Ident> for proc_macro::TokenStream`](https://doc.rust-lang.org/stable/proc_macro/struct.TokenStream.html#impl-Extend%3CIdent%3E-for-TokenStream) These previously stable APIs are now stable in const contexts: - [`<[_]>::rotate_left`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.rotate_left) - [`<[_]>::rotate_right`](https://doc.rust-lang.org/stable/std/primitive.slice.html#method.rotate_right) <a id="1.92.0-Cargo"></a> ## Cargo - [Added a new chapter](rust-lang/cargo#16119) to the Cargo book, ["Optimizing Build Performance"](https://doc.rust-lang.org/stable/cargo/guide/build-performance.html). <a id="1.92.0-Rustdoc"></a> ## Rustdoc - [If a trait item appears in rustdoc search, hide the corresponding impl items](rust-lang/rust#145898). Previously a search for "last" would show both `Iterator::last` as well as impl methods like `std::vec::IntoIter::last`. Now these impl methods will be hidden, freeing up space for inherent methods like `BTreeSet::last`. - [Relax rules for identifiers in search](rust-lang/rust#147860). Previously you could only search for identifiers that were valid in rust code, now searches only need to be valid as part of an identifier. For example, you can now perform a search that starts with a digit. <a id="1.92.0-Compatibility-Notes"></a> ## Compatibility Notes - [Fix backtraces with `-C panic=abort` on Linux by generating unwind tables by default](rust-lang/rust#143613). Build with `-C force-unwind-tables=no` to keep omitting unwind tables. * As part of the larger effort refactoring compiler built-in attributes and their diagnostics, [the future-compatibility lint `invalid_macro_export_arguments` is upgraded to deny-by-default and will be reported in dependencies too.](rust-lang/rust#143857) * [Update the minimum external LLVM to 20](rust-lang/rust#145071) * [Prevent downstream `impl DerefMut for Pin<LocalType>`](rust-lang/rust#145608) * [Don't apply temporary lifetime extension rules to the arguments of non-extended `pin!` and formatting macros](rust-lang/rust#145838) </details> --- ### Configuration 📅 **Schedule**: Branch creation - At any time (no schedule defined), Automerge - At any time (no schedule defined). 🚦 **Automerge**: Disabled by config. 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This strengthens the leak check to match the old trait solver. The new trait solver now also instantiates higher ranked goals in the same scope as candidate selection, so the leak check in each candidate detects placeholder errors involving this higher ranked goal.
E.g. let's look at tests/ui/higher-ranked/leak-check/leak-check-in-selection-2.rs
Here proving
(): for<'a> Trait<&'a str, ?u>viaimpl<'a> Trait<&'a str, &'a str> for ()equates?uwith&'!a strwhich results in a leak check error as?ucannot name'a. If this leak check error happens while considering candidates we drop the first impl and infer?utoString. If not, this remains ambiguous.This behavior is a bit iffy, see the FCP proposal in #119820 for more details on why this current behavior is somewhat undesirable. However, considering placeholders from higher-ranked goals for candidate selection does allow more code to compile and a lot of the code feels like it should compile. This caused us to revert the change of #119820 in #127568.
I originally expected that we can avoid breakage with the new solver differently here, e.g. by considering OR-region constraints. However, doing so is a significant change and I don't have a great idea for how that should work. Matching the old solver behavior for now should not make this cleaner approach any more difficult in the future, so let's just go with what actually allows us to stabilize the new solver for now.
This PR changing the new solver to match the behavior of the old one wrt the leak check. As the new solver is already used by default in coherence, this allows more code to compile, see
tests/ui/higher-ranked/leak-check/leak-check-in-selection-7-coherence.rs:This behavior is quite arbitrary and not something I expect users to rely on in practice, however, it should still go through an FCP imo.
r? @BoxyUwU originally implemented by @compiler-errors in #136997. Closes rust-lang/trait-system-refactor-initiative#120.