jiebi/CodeConvo huggingface dataset:
Code change:
pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str = "attributes of the form `#[derive_*]` are reserved for the compiler"; <del> pub const EXPLAIN_LITERAL_MATCHER: &'static str = ":literal fragment specifier is experimental and subject to change"; </del> pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str = "unsized tuple coercion is not stable enough for use and is subject to change";

Related discussion:
text: I dunno, maybe this is not such a good idea after all. Re-reading the RFC in a more skeptical light, I felt like the "Motivation" section could use some more concrete use cases. Maybe this is just failure of imagination on my part, though! I think the likelihood of this feature attracting people who really want constant expressions should be acknowledged as a drawback, too.
That's fine IMO. Personally I'd like it to match only explicit literals in code to distinguish, for example, between literal and identifier and produce different code for them. Right now this is not possible because all of , , are too broad and conflict with each other.
Hi All, I have implemented this feature in my fork of Rust over 1.25.0, under this branch: Following a quick review by a rustc mentor I may have the free time to provide a full pull request for this.
BTW label has the tooltip "implemented in nightly and unstable" but I did not see it there, i.e. commits & pull requests referencing this. Did I miss it?
The implementation that I worked on was merged, yay!
Is there anything stopping an FCP for this?
It's currently merged in unstable; do you mean an FCP to declare it stable?
Yes, an FCP to stabilise. Should have clarified.
Currently, it is not possible to pass a literal from a macro to another macro. . I think this is a bug.
Interesting! That is a bug. I opened to track it.
Agreed, this should be allowed just like passing any other node types.
Is there anything else preventing this from being stabilized? The issue above has been fixed.
This has baked for some time now and I believe it should be ready for stabilization. So let's start the review. merge The feature gate test is here: Unstable book: Tests defined here:
Team member has proposed to merge this. The next step is review by the rest of the tagged teams: [x] [x] [x] [x] [x] [ ] [x] [x] [x] [ ] No concerns currently listed. Once a majority of reviewers approve (and none object), 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!
Code change:
pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str = "attributes of the form `#[derive_*]` are reserved for the compiler"; <del> pub const EXPLAIN_LITERAL_MATCHER: &'static str = ":literal fragment specifier is experimental and subject to change"; </del> pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str = "unsized tuple coercion is not stable enough for use and is subject to change";

Related discussion:
text: See for info about what commands tagged team members can give me.
Reading through the tests, I see that is a literal. While that makes sense to me, I remember hearing that it wasn't, but was instead a negation operator and a literal. Am I misremembering?
cc on
I agree that it makes sense. I would say that even if is interpreted as negation + a literal, I would probably still want the macro matcher to accept since that behavior seems more intuitive. In other words, I would see being more as an implementation detail than what a literal is in the mental model.
I think that the nuance with causes a bit of a problem, because I don't think it should be treated as a literal, but I also don't think that the current implementation of would allow detecting it either. You could naïvely allow but that would allow which is clearly wrong.
there are tests currently implemented that verify that is detected as a literal.
I worded that wrong; I meant that only having a matcher and not being able to distinguish strings and numbers means that you can't easily make not a literal.
for procedural macros the input as lexed by the compiler is (two tokens) but procedural macros can create tokens that are negatives (like ). In that sense matching for makes sense to me.
Are literals generated by the compiler counted as true literals? A quick example would be something like: This fails to match, as the expansion, I guess, happens after the selection. I just naively assumed that would have worked.
is not a literal generated by the compiler, it is an identifier followed by an exclamation mark followed by a set of parentheses containing some tokens. See for example: If you were to use it in expression position, it would be interpreted as an invocation of which expands to a string literal. In this case and in your macro though, it is never in a syntactic position where it would be treated as an expression.
I can understand semantically why it doesn't make sense, I just thought it would have, but that being said, I already changed it to , so there's no issue. It just made more sense to me as a literal, because according to the compiler, it could generate a literal from it. I guess it was more a question than an actual issue.
This is true, but there's more to it!
Code change:
pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str = "attributes of the form `#[derive_*]` are reserved for the compiler"; <del> pub const EXPLAIN_LITERAL_MATCHER: &'static str = ":literal fragment specifier is experimental and subject to change"; </del> pub const EXPLAIN_UNSIZED_TUPLE_COERCION: &'static str = "unsized tuple coercion is not stable enough for use and is subject to change";

Related discussion:
text: A few built-in macros can expand their arguments eagerly through ~m a g i c~, so they accept and likes even if they expect string literals: Fortunately (or not), this currently cannot be done in user-defined macros.
I actually just realised that I can't change it to , as it's used in . So, I've just had to manually unroll the macro. ! It doesn't look pretty. :( Ninja edit: I just tested what actually happens if you try to pass in a non-literal with . It rejects it the exact same way. Does the already make use of this feature? If not, the seems to propagate the required token. Oh, unless the compiler steps in... That's actually probably the case... I've reverted it back to the type.
: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.
Since you implemented this, would you be willing to write up the stabilization PR?
sure
This appears to be missing from the Rust reference
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: The AVR-Rust post continues to track AVR-LLVM, which is tracking upstream LLVM. That means we are running into changes from the future LLVM 4.0. I figured we could open up this issue now to track the changes required to stay compatible. This is the current list of upgrade hazards. Note that some of the text may be nonsensical as I don't truly grok all the internals of LLVM so some changes are wild stabs in the dark. It's also possible that some failed fix for earlier problems actually caused later problems: [x] DIDescriptorFlags became a real C++ enum and not a bitset () [x] An EH personality is required for every function that can unwind () [x] pass changed header and constructor name () [x] changed API () [x] Bitcode/ReaderWriter.h has been renamed / API changed () () [x] changed API () [x] changed API () [x] prefers over () [x] string type changes () [x] is not guaranteed to be null terminated () [x] changed return types () [x] Archive support changed error handling types () [x] Teach Rust about an LLVM 4.0 API change for creating debug info for global variables () [x] Check all errors in LLVMRustArchiveIterator API () [x] Upgrade emscripten (kripken/emscripten-fastcomp, kripken/emscripten-fastcomp-clang) [x] Alignment now represented with 32 bits instead of 64 () [x] API changed again () [x] now takes an instead of a and () [x] Symbol lookup error when linking dylibs () [x] Undefined behavior in tests () [x] Unoptimised builds of compilerbuiltins on ARM have references to () A WIP PR that performs the upgrade! Some issues whose resolution is believed to be blocked on LLVM 4.0: [ ]
Next time we do this upgrade we'll need emscripten to do it to. It would be good if we could pull in a working llvm wasm backend in the same upgrade, but that may not be ready before the end of the year.
For the record, I am also working with a fork of LLVM that is tracking upstream (not AVR-LLVM but similar in spirit) and am starting to work on this now.
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: I'm looking through the AVR-Rust commits and I'd love to coordinate --- feel free to ping me on IRC () or via mail!
Note that there is a regression reported against llvm 4.0 regarding the powi intrinsic on armhf targets: I'm explicitly mentioning this here, because there were previously problems with it, see and related issues. Also cc rust-lang-nursery/compiler-builtins, an issue about the same problem in the compiler-rt rust port.
To clarify what I think the is referring to (correct me if I'm wrong) In LLVM 3.9 and before, the calling convention LLVM used with the powidf2 and powisf2 intrinsics was basically the C calling convention In LLVM 4.0, the backend was corrected to expect these intrinsics to have the aapcs calling convention One person that aapcs is expected for powis2f and powid2f, while another a claiming that the normal C calling convention should be used. So it seems that if the LLVM change is not reverted (expected powisf2 to be aapcs) then we need to update our definition. This is going to be a huge PITA for supporting multiple LLVM versions as well. We need to select the calling convention depending on the LLVM version as well...
Any objections to doing that coordination here on GitHub, or on one of our forks?
I don't have strong preferences for the communication channel.
should address what is listed as API changes" above (the core of the change is in how attributes are represented).
I would prefer to upstream LLVM 4.0 compatibility patches sooner rather than later. That includes my own work obviously, but I'm also looking at the commits I cherry-picked from AVR-Rust. In particular, looks like a reasonable simplification even independent of LLVM 4.0 compatibility, and looks like a nice little self-contained fix. Could you create PRs for those? (If you don't have the time but are otherwise fine with upstreaming, I'd be happy to manage that, giving proper credit of course.)
Absolutely! I wasn't really sure how much we could expect LLVM 4 to change as it goes towards stable / how much churn the Rust maintainers would want to put up with. I'll get those pulled out and submitted soon. I think I'm also starting to understand some of the silly error handling that the new LLVM does.
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: Awesome, thanks in advance!
BTW the PR reference for "llvm::AttrBuilder changed API" is wrong, it points at this issue instead of
Does anyone have ETA? I'd like to know when I can use AVR. :)
You should follow along at avr-rust/rust for the AVR-specific issues. Upgrading to LLVM 4 will not magically yield AVR support.
Ok, thank you!
I've created for the API change.
I've also created for another debug info API change.
After putting all of those patches on top of master, was successfully built. I got several undefined references, most likely due to my local LLVM setup.
I think the next step after all those patches land is to allow LLVM 4.0 in the configure/rustbuild scripts and then actually update the submodule.
We'll also need to fix that AAPCS bug first, I just noticed it
Don't forget : I think that means that the Rust fork of LLVM is following the Emscripten fork of LLVM, thus Emscripten needs to upgrade to LLVM 4.0 / master before Rust can.
And I'm hoping to supersede it with
I just ran into which changed the alignment from u64 to u32. Will think about a proper fix later, unless someone beats me to it (but should merge first to avoid further conflicts).
And it says So, that will be "exciting".
Is there much left blocking an upgrade?
This: Has to be done too but I don't know if it's currently being worked on. Any info on that ^?
No nobody is actively working on an emscripten upgrade. Since even when that is done it will probably take a lot of work to land an LLVM upgrade, there's probably more we can do to prepare. Once we decide we want to do it, somebody can prepare a patch to throw at the bots. It seems likely stuff will not work and it will be a slog to fix it all, which will give us time. We don't need emcc to generate wasm stds, just a fairly small patch on our LLVM branch that will hopefully port without much difficulty. So if somebody feels motivated, it's not too soon to start going after it. As to the emscripten upgrade, we should at least let know that we're starting to think seriously about doing the upgrade, and need emscripten to upgrade LLVM too.
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: It seems like that could be a big effort. Another alternative is to use the LLVM wasm backend, but I still have not heard that it is generally usable yet. cc
I can look into the effort needed to update emscripten's fastcomp LLVM version, but I need to know a commit to aim for. Sounds like the goal here is 4.0, which hasn't released yet, so I guess I have to wait on that?
So far as AVR is concerned, any commit within the last month will do. There will likely be a few more months until 4.0 is actually tagged (every ~6 months a new release is made). It is quite common for projects to track LLVM master, which I'm personally a fan of.
But is it common to release snapshots from LLVM master? When LLVM itself only releases every 6 months, it seems incongruous for Rust to pick arbitrary snapshots in its 6-week release cycle.
LLVM 4.0 will branch in a week and the final release will happen in late feburary (schedule says 21st for final tag, but this is flexible IIRC).
From the llvm-dev mailing list:
branch has happened
An update on the "powidf2 / powisf2 calling convention changed" situation: The regression has been fixed on llvm master () however from what I can tell the fixes are not yet in the 4.0 branch, although the fix may be backported ().
I've started working on updating emscripten kripken/emscripten-fastcomp kripken/emscripten-fastcomp-clang I've also created a new bug requesting that the regression fix be merged into 4.0 .
says the emcc LLVM upgrade is ready to go. or are we prepared to begin the Rust LLVM upgrade? I think what needs to happen is to submit the Rust PR and start throwing it against the bots. Once it looks like that is close to landing then we'll have to coordinate both project's upgrades to minimize the breakage window where rustc and emcc have different backends. I'm not sure how best to do that - we might just try to upgrade as simultaneously as possible and accept up to a few days of breakage, or we might ask emscripten to stage their build such that they can swap their incoming branch right after we land to master.
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: needs to know the exact LLVM commit we're moving to as well, and that will become clear once the PR starts working through the queue. The stars are aligning. Let's make this happen. Thanks for doing the fastcomp upgrade.
We are not fully compatible with LLVM 4.0. I have heard from at least one person (on IRC) that building against stock LLVM 4.0 (RC) does not work. I haven't personally inspected all failures, but there's at least two things still missing: (and possibly ). It shouldn't be a conceptually difficult patch to apply the equivalent changes to rustc, but possibly a big diff. I haven't digested the implications yet, but it might be a relatively simple change localized to the function in that currently calls .
The fix has been merged into the 4.0 release (). I'm going to try and build Rust against stock LLVM 4.0 and figure out what needs modifying.
On top of what mentioned: now takes an instead of a and ()
I've got a half-baked patch to use the new signature for I'm not familiar enough with Rust internals to finish it off. I ran into a problem in as it is given a but in order to use we need a . We need to call in order to build an instance of .
I've opened for the change that mentioned. I've also opened for the 32-bit alignment change. I believe that is the only thing we need to update aside from these two PRs in order to get the compiler to successfully be built with LLVM 4.0.
So to summarize where we are with LLVM 4 (correct me if I'm wrong): 4.0 will be released in about 1 week (2/21). are no known issues with supporting LLVM 4.0, but there are probably issues that will be discovered once we try to use it in nightlies. runs on in-tree LLVM + LLVM 3.7 (so PRs haven't actually been tested on LLVM 4.0 yet). support LLVM back to ~3.6(?
Code change:
exit_success_if_unwind::bar(do_panic); } } <del> let s = Command::new(env::args_os().next().unwrap()).arg("foo").status(); </del> <ins> let mut cmd = Command::new(env::args_os().next().unwrap()); cmd.arg("foo"); // ARMv6 hanges while printing the backtrace, see #41004 if cfg!(target_arch = "arm") && cfg!(target_env = "gnu") { cmd.env("RUST_BACKTRACE", "0"); } let s = cmd.status(); </ins> assert!(s.unwrap().code() != Some(0)); }

Related discussion:
text: )~ 3.7 and will continue to support it until either: a. It's so old that it can be removed without bothering package maintainers b. We need at least version X in order to fix an important bug c. The API is so different from version Y that it's a huge pain to support will open a PR to update the submodule shortly after release but it will take a month to land due to: a. Waiting for emscripten ( -) b. Bugs in upstream c. Missed LLVM API changes d. Making bors happy e. All of the above
Thanks for the summary The only correction I'd make is that in your point (4) you can s/3.6/3.7/, but otherwise it's accurate :) If you'd like to start preparing a PR to update to LLVM 4.0 I don't think we need to block waiting for LLVM itself to release 4.0. Currently only one Travis builder runs on each PR but we could temporarily allow more builders running on an LLVM 4.0 PR to start weeding out bugs before it hits
I gave it a go but I don't think my git-fu (or patience) is strong enough to handle a big merge like this. What I can do is try to run rustc with upstream LLVM and file/fix issues as I find them. There is at least one issue remaining as of (details to come).
Whoever ends up doing the LLVM upgrade, please also upgrade the compiler-rt submodule so that the sanitizer related LLVM passes don't diverge from what the sanitizer runtimes expect.
In fact, if you upgrade before the release, they usually mention your project in the release notes. :)
So whats the next issue(s) to subscribe to in the race-to-AVR? :)
As says on , we can integrate the latest Rust master into the avr-rust compiler. After that, we can spend some time getting compiling for AVR. Once that is working, we could then start looking into upstreaming the AVR target to Rust.
AVR-specific issues can be raised / tracked in For example, there are two that I'm aware of right now:
has been closed, so that can be checked off in the top post.
Code change:
<ins> // This tests the parser recovery in `recover_intersection_pat` // and serves as a regression test for the diagnostics issue #65400. // // The general idea is that for `$pat_lhs @ $pat_rhs` where // `$pat_lhs` is not generated by `ref? mut? $ident` we want // to suggest either switching the order or note that intersection // patterns are not allowed. fn main() { let s: Option<u8> = None; match s { Some(x) @ y => {} //~^ ERROR pattern on wrong side of `@` //~| pattern on the left, should be on the right //~| binding on the right, should be on the left //~| HELP switch the order //~| SUGGESTION y @ Some(x) _ => {} } match s { Some(x) @ Some(y) => {} //~^ ERROR left-hand side of `@` must be a binding //~| interpreted as a pattern, not a binding //~| also a pattern //~| NOTE bindings are `x`, `mut x`, `ref x`, and `ref mut x` _ => {} } match 2 { 1 ..= 5 @ e => {} //~^ ERROR pattern on wrong side of `@` //~| pattern on the left, should be on the right //~| binding on the right, should be on the left //~| HELP switch the order //~| SUGGESTION e @ 1 ..=5 _ => {} } } </ins>

Related discussion:
text: The compiler could suggest that identifier must precede the pattern in the following code: playpen link: Current error message: It could be improved as:
modify labels: A-diagnostics C-feature-request T-compiler
So what happens after is that we've parsed a and then follows which is not a valid token after a parsed . To fix this we can, after having parsed in , check if follows and then emit appropriate suggestions. We will need to use some heuristics to figure out what the user wants based on the structure of . Some of the suggestions would be and some not. cc