regression: c"..." are experimental #113235

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1. Mark-Simulacrum

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   T-langRelevant to the language teamRelevant to the language team

   regression-from-stable-to-betaPerformance or correctness regression from stable to beta.Performance or correctness regression from stable to beta.

   on Jul 1, 2023
2. Mark-Simulacrum

   added this to the 1.71.0 milestone on Jul 1, 2023
3. rustbot

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   I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

   on Jul 1, 2023
4. fmease commented on Jul 1, 2023

   

   fmease

   on Jul 1, 2023

   Last edited by fmease

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   c"…" inside macro calls (with macro matches like c$e:expr) should definitely continue to compile in editions 2015 and 2018. Those prefixes are only reserved in edition 2021 and onward.

   The following reproducer compiles successfully on stable in editions 2015 and 2018 but fails to compile on beta and nightly while it should remain valid:

   macro_rules! m { (c$e:expr) => {}; }
   
   fn main() { m!(c"hello"); }

   stderr

   error: no rules expected the token `c"hello"`
    --> src/main.rs:3:16
     |
   1 | macro_rules! m { (c$e:expr) => {}; }
     | -------------- when calling this macro
   2 |
   3 | fn main() { m!(c"hello"); }
     |                ^^^^^^^^ no rules expected this token in macro call
     |
   note: while trying to match `c`
    --> src/main.rs:1:19
     |
   1 | macro_rules! m { (c$e:expr) => {}; }
     |                   ^
   
   error[E0658]: `c".."` literals are experimental
    --> src/main.rs:3:16
     |
   3 | fn main() { m!(c"hello"); }
     |                ^^^^^^^^
     |
     = note: see issue #105723 <https://github.com/rust-lang/rust/issues/105723> for more information
   
   

   @rustbot label S-has-mcve
5. rustbot

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   S-has-mcveStatus: A Minimal Complete and Verifiable Example has been found for this issueStatus: A Minimal Complete and Verifiable Example has been found for this issue

   on Jul 1, 2023
6. Mark-Simulacrum

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   T-compilerRelevant to the compiler team, which will review and decide on the PR/issue.Relevant to the compiler team, which will review and decide on the PR/issue.

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   T-langRelevant to the language teamRelevant to the language team

   on Jul 1, 2023
7. fmease commented on Jul 1, 2023

   

   fmease

   on Jul 1, 2023

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   This would be easy to fix if we had access to the edition in rustc_lexer but I don't know if it's acceptable to pass that information to Cursor.
   Alternatively, we could unravel CStr and CStrRaw literals into two tokens (Ident and Str / StrRaw) after the fact in rustc_parse::lexer where we have access to the edition, although that's a bit messier I guess (and other parsers like rust-analyzer's would need to remember this step & redo this work).
8. Noratrieb

   added

   F-c_str_literals`#![feature(c_str_literals)]``#![feature(c_str_literals)]`

   on Jul 1, 2023
9. hameerabbasi commented on Jul 2, 2023

   

   hameerabbasi

   on Jul 2, 2023

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   Assigning P-medium since this is only a warning, and only valid for older editions of Rust.

   @rustbot label -I-prioritize +P-medium
10. rustbot

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    P-mediumMedium priorityMedium priority

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    I-prioritizeIssue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}Issue needs a team member to assess the impact. Will be replaced by P-{low,medium,high,critical}

    on Jul 2, 2023
11. fmease commented on Jul 2, 2023

    

    fmease

    on Jul 2, 2023

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    since this is only a warning

    @hameerabbasi It's not a warning but a hard error. noc7c9/pyfection no longer compiles due to this bug. rustc lexes the crate differently than before.

    ❤️React with ❤️1Reacted by Hameer Abbasi
12. hameerabbasi commented on Jul 2, 2023

    

    hameerabbasi

    on Jul 2, 2023

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    @fmease Do you recommend P-high? Feel free to change the label if so.
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14. compiler-errors

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    E-needs-bisectionCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustcCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc

    on Jul 2, 2023
15. fmease commented on Jul 2, 2023

    

    fmease

    on Jul 2, 2023

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    Without doing a bisection, I can tell you that this regressed in #108801 (regressed in: 8ff3903, still a regression after refactoring commit: a49570f) when rustc_lexer/src/lib.rs was modified (manually reverting those changes to the lexer makes the reproducer compile again).

    @rustbot label -E-needs-bisection
16. rustbot

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    E-needs-bisectionCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustcCall for participation: This issue needs bisection: https://github.com/rust-lang/cargo-bisect-rustc

    on Jul 2, 2023
17. compiler-errors commented on Jul 4, 2023

    

    compiler-errors

    on Jul 4, 2023

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    Let's at least revert the lexer changes until @fee1-dead or someone else can fix this in a way that's compatible with the pre-2021 editions @fmease, do you want to do that, or shall I?
18. fmease commented on Jul 4, 2023

    

    fmease

    on Jul 4, 2023

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    Just reverting the lexer change & keeping everything else related to c_str_literals? I can do that within this hour when I find the time. Edit: And reverting all the tests.

    @rustbot claim
19. rustbot

    assigned

    fmease

    on Jul 4, 2023
20. compiler-errors commented on Jul 4, 2023

    

    compiler-errors

    on Jul 4, 2023

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    To be clear, all the existing cstring tests would break, so you'll have to mark some of the tests as // known-bug: ### and open an issue tracking that functionality getting added. That'll make it so someone knows to pick it up and fix it 😸

    👍React with 👍1Reacted by León Orell Valerian Liehr
21. fmease commented on Jul 4, 2023

    

    fmease

    on Jul 4, 2023

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    Slightly unrelated, but I've noticed that the GitHub label should be renamed from F-c_str_literal to F-c_str_literals and its description needs to be updated, too (see https://github.com/rust-lang/rust/blob/master/compiler/rustc_feature/src/active.rs for the source of truth).
22. fee1-dead

    added a commit that references this issue on Jul 6, 2023

    Rollup merge of rust-lang#113334 - fmease:revert-lexing-c-str-lits, r…

    ...

    1830b80
23. fmease commented on Jul 12, 2023

    

    fmease

    on Jul 12, 2023

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    This is now fixed on beta and can be closed, right?
24. nagisa commented on Jul 16, 2023

    

    nagisa

    on Jul 16, 2023

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    Correct, we have an issue tracking reimplementation at #113333
25. nagisa

    closed this as completedon Jul 16, 2023