jiebi/CodeConvo huggingface dataset:
Change:
token::Ident(..) => { e = self.parse_dot_suffix(e, lo)?; } <del> token::Literal(token::Integer(n), suf) => { </del> <ins> token::Literal(token::Integer(index_ident), suf) => { </ins> let sp = self.span; // A tuple index may not have a suffix

Discussion:
The following compiles, but I think it shouldn't?
The field name is converted to a number too eagerly. This doesn't happen in struct expressions and patterns.
Change:
//! # The Rust Core Library //! <del> //! The Rust Core Library is the dependency-free foundation of [The </del> <ins> //! The Rust Core Library is the dependency-free[^free] foundation of [The </ins> //! Rust Standard Library](../std/index.html). It is the portable glue //! between the language and its libraries, defining the intrinsic and //! primitive building blocks of all Rust code. It links to no //! upstream libraries, no system libraries, and no libc. //! <ins> //! [^free]: Strictly speaking, there are some symbols which are needed but //!          they aren't always neccesary. //! </ins> //! The core library is *minimal*: it isn't even aware of heap allocation, //! nor does it provide concurrency or I/O. These things require //! platform integration, and this library is platform-agnostic.

Discussion:
As noted in among other places, core is not really completely dependency-free. While this claim is defensible in some sense, the crate documentation could be more clear about what it means by this, for example by describing the criterion outlined by in the aforementioned issue: The docs already talk about and , but in the meantime libcore gained a few other (intentionally) undefined symbols such as and --- possibly others as well. The docs should explain those symbols too, and also explain how get around the need for them (don't use on floats, link with ).
Change:
/// /// [`None`]: ../../std/option/enum.Option.html#variant.None /// [`parent`]: struct.Path.html#method.parent <del> #[unstable(feature = "path_ancestors", issue = "48581")] </del> <ins> #[stable(feature = "path_ancestors", since = "1.28.0")] </ins> pub fn ancestors(&self) -> Ancestors { Ancestors { next: Some(&self),

Discussion:
Tracking issue for , and . Steps: [X] Implementation [X] Stabilization PR () Unresolved questions: [X] What is a good name? ? ?
cc
Change:
"{place_name} {partially_str}moved due to this method call{loop_message}", ), ); let infcx = tcx.infer_ctxt().build(); <ins> // Erase and shadow everything that could be passed to the new infcx. </ins> let ty = tcx.erase_regions(moved_place.ty(self.body, tcx).ty); <ins> let method_substs = tcx.erase_regions(method_substs); </ins> if let ty::Adt(def, substs) = ty.kind() && Some(def.did()) == tcx.lang_items().pin_type() && let ty::Ref(_, _, hir::Mutability::Mut) = substs.type_at(0).kind()

Discussion:
searched nightlies: from nightly-2023-01-27 to nightly-2023-01-28 regressed nightly: nightly-2023-01-28 searched commit range: regressed commit: <details<summarybisected with <a href=''cargo-bisect-rustc</av0.6.5</summaryHost triple: x8664-unknown-linux-gnu Reproduce with: </details label +I-ICE +F-typealiasimpltrait
Minimized it further:
Change:
/// /// [`capacity`]: ../ffi/struct.OsString.html#method.capacity /// [`OsString`]: ../ffi/struct.OsString.html <del> #[unstable(feature = "path_buf_capacity", issue = "58234")] </del> <ins> #[stable(feature = "path_buf_capacity", since = "1.44.0")] </ins> pub fn capacity(&self) -> usize { self.inner.capacity() }

Discussion:
, should probably not be stabilized before , see
Happy to take this on as a first contribution to rust.
Great! I'd be happy to help you get started, just let me know if you want mentoring/instructions at any level!
are you able to define a list of the methods that need to be implemented as part of this PR?
I think all of these will essentially call the underlying functions on . [ ] [ ] [ ] [ ] [ ] [ ] [ ] -- this one is more of a maybe, since it's unstable on OsString. We can reuse the same tracking issue for this. We'll probably want to add all of these under the same feature gate.
thanks for that. I have the implementation drafted locally. I'm having some difficulty however in running the tests for stdlib - even a is producing errors not related to my changes. Is there any documentation I've missed for best practices on compiling / working on stdlib?
You'll want to use x.py; for your scenario I believe and/or are the commands you want. I'm not sure where the most current documentation is.
describes how to use .
Triage: since has been merged, can this be closed?
No, this is now the tracking issue for the stabilization of those APIs.
Reviewing this since then, I think it may be worth removing these APIs and replacing them with something like and . These aren't really commonly used so hiding them as such seems reasonable and is less heavy.
I'd love to see these stabilized. I have a tool that manipulates lots of paths, so I'd like to avoid needless reallocations. I generate lots of temporary paths in a loop. would work nicely to reuse the buffer. I need to concatenate several components. I know their length, so I could use I want to store lots of paths for later. is a bit smaller than , but if I can't reserve exact capacity, will reallocate.
merge
Team member has proposed to merge this. The next step is review by the rest of the tagged team members: [x] [ ] [x] [x] [x] [ ] 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 for info about what commands tagged team members can give me.
reviewed assuming we're only stabilizing capacity + withcapacity + clear + reserve + reserveexact + shrinktofit;&ensp;and shrink_to is being moved to instead.
:bell: This is now entering its final comment period, as per the . :bell:
The final comment period, with a disposition to merge, as per the , is now complete. As the automated representative of the governance process, I would like to thank the author for their work and everyone else who contributed. The RFC will be merged soon.
I've posted a stabilization PR in .
Change:
trait_def.generics.types.as_slice(), trait_def.generics.regions.as_slice(), trait_ref.substs, <del> variance); </del> <ins> self.invariant); </ins> } ty::ty_trait(ref data) => {

Discussion:
showed me program which fails to compile. Here is a reduced version: This yields: However, if you change the type of to , it builds. Seems like there is a missing constraint somewhere in the region inference graph.
I tagged this as associated items as my best guess is that the constraint that would to affect is somehow getting lost.
I think the problem is actually variance, as guessed initially, or perhaps a question of what the subtyping rules for associated types ought to be. Let's consider a simple trait : The normal variance inference will conclude that is contravariant w/r/t , because only appears in a contravariant position in the method signature for . Now imagine I have and , where . What can we say about the relationship between and , if any? My first thought was that since (since is contravariant), we could say that . But that doesn't seem to make any sense -- after all, this contravariance result is based purely on method signatures, and has no relation to the associated type definitions. And anyway we can easily concoct some examples where that relationship doesn't hold: Now if and , where , then . So we'd expect that if my initial rules were correct, then -- and hence . But in fact , since fn types are covariant in their return type and . So in this case . But clearly we also can't conclude that in general either. After all, we can easily build another example where the relationship is the opposite: So it seems like the only thing we can conclude is that iff . In other words, a projection type is invariant with respect to its trait reference. This seems awfully strong but it's not clear to me how to make a weaker rule, at least not without some kind of declaration in the trait somehow relating the variance of to the trait inputs.
Yes, I think your examples have hit it on the head: In general one cannot draw any conclusion about the relationship between and without adding constraints (in the trait definition itself) on (1.) what the implementing type chooses for the associated item and/or (2.) the variance of that associated type with respect to the trait inputs and/or the type. And we do not currently have anyway to express such constraints in the language, AFAICT.

I'll try to get a fix up for this today, but in the meantime you CAN workaround it by adding a method like this to the trait:
I already implemented the fix but I'm a bit stymied on how to write nice unit tests without support for style where clauses. I may just go off on a yak shave and implement those, which I've been meaning to do for other reasons.
Fix enqueued ().
Thanks! I'll use the workaround for now.
Change:
return; } <ins> if is_unsize { // If the obligation failed due to a missing implementation of the // `Unsize` trait, give a pointer to why that might be the case err.note( "all implementations of `Unsize` are provided  automatically by the compiler, see  <https://doc.rust-lang.org/stable/std/marker/trait.Unsize.html>  for more information", ); } </ins> // Try to report a help message if !trait_ref.has_infer_types_or_consts() && self.predicate_can_apply(obligation.param_env, trait_ref)

Discussion:
I was playing with while I encountered a The simplest example I have producing the bug is Here is . It works if I remove the struct and put the directly in . The complete backtrace is <!-- TRIAGEBOTSTART --<!-- TRIAGEBOTASSIGNSTART --This issue has been assigned to via . <!-- TRIAGEBOTASSIGNDATASTARTTRIAGEBOTASSIGNDATAEND --<!-- TRIAGEBOTASSIGNEND --<!-- TRIAGEBOTEND --
minimised ()
claim
Change:
help: use `Box::new()` instead | LL |     let _: Box<()> = Box::new(()); <del> |                      ~~~~~~~~~~~~ </del> <ins> |                      ~~~~~~~~~  + </ins> error: aborting due to 5 previous errors

Discussion:
Found by grepping through the compiler via while reviewing an unrelated PR. File : File : : . or move source file . : . <details<summaryFull compiler output</summary</details:
Solution: Get rid of altogether and use a multi-part suggestion (, ).
Change:
/// ``` #[inline] #[stable(feature = "rust1", since = "1.0.0")] <del> pub fn new() -> Vec<T> { </del> <ins> #[rustc_const_unstable(feature = "const_vec_new")] pub const fn new() -> Vec<T> { </ins> Vec { buf: RawVec::new(), len: 0,

Discussion:
It should either elaborate on AssertUnwindSafe or else drop the claim that it will elaborate below.
Change:
} try!(fulfill_cx.select_all_or_error(infcx, closure_typer)); let resolved_value = infcx.resolve_type_vars_if_possible(&normalized_value); <del> debug!("normalize_param_env: resolved_value={}", resolved_value.repr(tcx)); </del> <ins> debug!("normalize_param_env: resolved_value={}", resolved_value.repr(tcx)); </ins> Ok(resolved_value) }

Discussion:
Attempting to compile with and yields the following ICE:
Reduced test case: Still ICEs with The ICE goes away if the on the is changed to a bare instead of a reference.
Slightly different test case: EDIT: Nevermind, it's the same but uses a closure instead of the more general .
I have bisected this issue to rust-lang/rust (from )
A workaround would be simply:
This doesn't help much if you need to call methods that are on the trait (which was on the original code).
cc me
This is blocking collect-rs from compiling.
This is interesting. The culprit is : it registers obligations from implementation's methods into an hybrid parameter environment which has trait's methods in it. In the example given in this issue, when the associate type is projected out, the implementation's method acquires an extra lifetime variable. The trait's method doesn't have it so the lifetime resolution fails in an ICE later on. I'm not sure how to fix that though.
This compiles so at first glance it looks like a viable workaround: But if one tries to really use as an , compiler panics on an assertion failure:
Getting this with some hashing code.

will output something along the lines of: Start hash BYTES: [69, 84, 87, 87, 100, 57, 118, 102, 80, 97, 122, 56, 100, 116, 80, 82, 74, 78, 104, 116, 109, 51, 88, 54, 56, 98, 56, 97, 66, 119, 105, 116, 90, 114, 50, 83, 107, 99, 51, 52, 89, 121, 121, 112, 86, 116, 57, 66, 120, 87, 86, 112, 88, 55, 66, 49, 76, 90, 86, 48, 49, 53, 56, 53, 52, 48, 56, 56, 49, 53, 54, 48, 51] lyra2 finished: CfV9jehQVXsVnx6Vrg5f9VgHVkWeatbrFGxKVz2knfEc Starting argon thread 'certificate::tests::checkcertdiff' panicked at 'index out of bounds: the len is 0 but the index is 31',
Change:
) -> Vec<CoverageSpan> { let mut coverage_spans = CoverageSpans { mir_body, <del> fn_sig_span, </del> <ins> fn_sig_span: fn_sig_source_span(fn_sig_span, body_span), </ins> body_span, basic_coverage_blocks, sorted_spans_iter: None,

Discussion:
I tried to generate test code coverage with this source file using and the LLVM tools. Source File: I expected to see this happen: Instead, this happened: . cargo-kcov, -Zprofile+grcov, and tarpaulin agree on 76%. In the output below lines , , were not executable but should have been executable+uncovered. Line should be executable+covered. <details<summarycoverage output</summary<p</p</details:
label: +A-code-coverage cc
Thanks for the bug report ! There was a recent bug fix (PR ) that addresses most of the missing coverage in your example (except for the last one). I just tested with and I see the expected coverage now for the first three ranges you reported seeing no coverage. These three are now showing coverage (with 0 executions) as expected: I was surprised to see no coverage for line 169, and I do see the did print, so that does seem to be a bug. So as of today, this issue is still a bug that I will need to look into further:
cc: Note, here is a snippet showing the missing coverage and code relevant to its codepath. I haven't thoroughly investigated this. I should be able to reproduce this in a simplified test (without the asynctrait and executor dependencies) that I can add to our unit tests. I don't have a theory yet. It could either be the closure's MIR is not included in coverage (seems unlikely to me), or is silently dropping coverage because it doesn't like something. (This is what was happening for the other missing coverage reported in this issue, that has since been resolved.) The test (shown at the bottom) calls and awaits the implementation of below: I do see the test output, including the from above, and from the awaited call to , below: The async closure seems to be missing coverage, as shown here. Note the wrapper function is covered and called (showing the coverage of on line 168), but there should also be coverage for the awaited implicit closure (lines 168-170, I believe). Since the program output proves this is called, the coverage should be showing execution. And the test that invokes it is covered:
Thank you. I see improvement in the latest nightly.

I minified the test case to the async issues for anyone looking at this (but it still uses executor and asynctrait.) Since this function is missing coverage too the issue isn't specific to async_trait thought.
So it turns out that the internal (auto-generated) closure actually does get coverage, but for some reason the code region for the macro, by itself, is not or not counted. I've created a draft PR with a new test and current results, demonstrating this issue. Once I figure out how to fix it, I'll submit the PR with the updated results.
Update: fixes the issue.
Change:
err.span_label(lo, WHILE_PARSING_OR_MSG); err })?; <del> self.maybe_recover_unexpected_comma(pat.span, rc)?; </del> <ins> self.maybe_recover_unexpected_comma(pat.span, rc, gate_or)?; </ins> pats.push(pat); } let or_pattern_span = lo.to(self.prev_token.span);

Discussion:
When forgetting to include parenthesis around a tuple pattern in a for loop, the compiler gives a suggestion to use an or pattern. I would expect this, a. because it's not what most would expect if you use a comma to separate two values in a pattern, and b. because or patterns in for loops are still an unstable feature. I tried this code: As expected, the compiler gives an , error, because I forgot the parenthesis around . However, the compiler also suggests that I add a "vertical bar to match on multiple alternatives". While it does provide the correct answer (adding parenthesis), it also provides the vertical bar option, which is an unstable feature in this . While the RFC does not explicitly single out for loops as a situation where this is necessary, I believe it does apply here, because in (credit /u/ehuss for the example, which is a situation where the or pattern syntax is being used correctly, I get a error, as expected, and including resolves the error. I tested this on stable, beta, and nightly in the rust playground. The output is identical for all 3 of them. <!-- TRIAGEBOTSTART --<!-- TRIAGEBOTASSIGNSTART --<!-- TRIAGEBOTASSIGNDATASTARTTRIAGEBOTASSIGNDATAEND --<!-- TRIAGEBOTASSIGNEND --<!-- TRIAGEBOT_END --
I would like to work on this, if possible Would it just be only giving if like ?
that seems like the right approach :)
claim
Looking at this more closely I'm not sure the fix is that simple, since and seems to (Which matches the comment for )
Looking at usages of GateOr::{Yes, No}, it looks like the only top level things (Which are the only ones that give the suggestion AIUI) that are GateOr::Yes are local variable declaration patterns and for patterns EDIT: I'm gonna try just propagating the GateOr into mayberecoverunexpected_comma
Change:
// More generally, the expected type wants a tuple variant with one field of an // N-arity-tuple, e.g., `V_i((p_0, .., p_N))`. Meanwhile, the user supplied a pattern // with the subpatterns directly in the tuple variant pattern, e.g., `V_i(p_0, .., p_N)`. <del> let missing_parenthesis = match expected.kind { ty::Adt(_, substs) if fields.len() == 1 => { let field_ty = fields[0].ty(self.tcx, substs); </del> <ins> let missing_parenthesis = match (&expected.kind, fields, had_err) { // #67037: only do this if we could sucessfully type-check the expected type against // the tuple struct pattern. Otherwise the substs could get out of range on e.g., // `let P() = U;` where `P != U` with `struct P<T>(T);`. (ty::Adt(_, substs), [field], false) => { let field_ty = self.field_ty(pat_span, field, substs); </ins> match field_ty.kind { ty::Tuple(_) => field_ty.tuple_fields().count() == subpats.len(), _ => false,

Discussion:
Source code:
Please provide the source code needed to reproduce this (or preferably a reduced version of that)
Sourced code provided at the end of the document. I'm willing to provide more info if needed.
Reconstructed from first principles:
The problem occurs here:
triage: has PR. P-high, removing nomination.
Change:
<ins> error[E0599]: no method named `foo` found for struct `Qux` in the current scope --> $DIR/method-ambiguity-no-rcvr.rs:12:9 | LL | struct Qux; | ---------- method `foo` not found for this struct ... LL |     Qux.foo(); |         ^^^ this is an associated function, not a method | = note: found the following associated functions; to be used as methods, functions must have a `self` parameter note: candidate #1 is defined in the trait `Foo` --> $DIR/method-ambiguity-no-rcvr.rs:4:5 | LL |     fn foo(); |     ^^^^^^^^^ note: candidate #2 is defined in the trait `FooBar` --> $DIR/method-ambiguity-no-rcvr.rs:8:5 | LL |     fn foo() {} |     ^^^^^^^^ help: disambiguate the associated function for candidate #1 | LL |     <Qux as Foo>::foo(Qux); |     ~~~~~~~~~~~~~~~~~~~~~~ help: disambiguate the associated function for candidate #2 | LL |     <Qux as FooBar>::foo(Qux); |     ~~~~~~~~~~~~~~~~~~~~~~~~~ error: aborting due to previous error For more information about this error, try `rustc --explain E0599`. </ins>

Discussion:
<!-- ICE: Rustc '' 'thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0'', 'thread 'rustc' panicked at 'index out of bounds: the len is 0 but the index is 0'' File: --auto-reduced (treereduce-rust): &lt;details&lt;summary&lt;strongoriginal code&lt;/strong&lt;/summary&lt;poriginal: </p</detailsVersion information ` Command: <!-- Include a backtrace in the code block by setting in your environment. E.g. . --<details<summary<strongProgram output</strong</summary<p</p</details
/ ping
Change:
//@compile-flags: -Zmiri-strict-provenance <del> //@error-in-other-file: /retag .* tag does not exist in the borrow stack/ </del> fn main() { unsafe { let a = [1, 2, 3]; let s = &a[0..0]; assert_eq!(s.len(), 0); <del> assert_eq!(*s.get_unchecked(1), 2); </del> <ins> assert_eq!(*s.as_ptr().add(1), 2); //~ ERROR: /retag .* tag does not exist in the borrow stack/ </ins> } }

Discussion:
<!-- Thank you for filing a bug report! Please provide a short summary of the bug, along with any information you feel relevant to replicating the bug. --I tried this code: Compile with on () I expected to see this happen: Both functions should compile to approximately the same thing, with no bounds check on the since the optimizer should be able to see that the slice is at least of length 2 due to the previous unchecked indexing. Instead, this happened: contains a bounds check (only does not contain a bounds check). rustc stable (1.73.0), nightly (2023-10-17), and 1.58.0 (when was stabilized) all have approximately the same codegen. : (no backtrace) label +C-optimization -C-bug
contains an assume intrinsic, doesn't. Might be worth adding it to the latter and see how that impacts perf, it's not guaranteed that it would actually improve things since we'd be emitting more IR and llvm would have to work harder. Commonly it's the case that if one uses one does so for all accesses on the slice, so this seems like an unusual pattern.
Change:
#![feature(core_intrinsics)] #![feature(const_fn)] #![feature(decl_macro)] <ins> #![feature(drain_filter)] </ins> #![feature(exhaustive_patterns)] #![feature(never_type)] #![feature(specialization)]

Discussion:
Offending snippet using : The code shouldn't build, as per the first few errors below, but currently on nightly it also causes the compiler to panic. It does not panic on stable or beta. Version: 1.40.0-nightly (2019-10-12 ) Playground: Quite possibly a duplicate of just buried inside the macro expansion but I'm not familiar enough with Rust compiler internals to make that determination.
cc
I've to the following: A mutable reference is required in all variants of this, so this particular mismatch does not represent a true backwards compatibility hazard: Creating a reference that would allow mutation is forbidden in all contexts. We could simply stop triggering the mismatch ICE when both lists contain the same error. The underlying issue, however, is that is being too conservative once again. As soon as a mutable reference is taken to , we use type-based qualification instead of looking at the qualif which gets cleared when is moved from. Increasing the precision here would require a dataflow analysis. This would get checked first whenever was queried (much like how we currently check first). I believe this will be necessary when we do allow in contexts, otherwise writing code would be quite painful. I could hack together a solution for this particular case that doesn't require another dataflow analysis. Basically, during validation, we could keep track of which s have been moved out of in the current basic block and use that as a conservative approximation of . This would fail if the local was moved from in one basic block and then dropped in a successor of that block. It seems relatively hard to write rust code that gets translated to that MIR, however. For example, the following does not do it, but I think it should be possible.
cc
Checking for moves in the same block fails pretty often. I've implemented the first fix described above, but we probably want to use a analysis in the long term.
triage: P-medium. Assigning to . Removing nomination label.