regression: local ambiguity: multiple parsing options: built-in NTs lifetime  #70446

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1. Mark-Simulacrum

   added

   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.

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

   on Mar 26, 2020
2. Centril

   added

   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

   E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable ExampleCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example

   on Mar 26, 2020
3. Centril commented on Mar 26, 2020

   

   Centril

   on Mar 26, 2020

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   Possibly accidentally injected by #70074.
   Would be good to find out why this is happening, so let's @rustbot ping cleanup
   and see if we can bisect / shrink the problem down to something usable for finding a fix.
4. Centril commented on Mar 26, 2020

   

   Centril

   on Mar 26, 2020

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   @rustbot ping cleanup
5. rustbot commented on Mar 26, 2020

   

   rustbot

   on Mar 26, 2020

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   Hey Cleanup Crew ICE-breakers! This bug has been identified as a good
   "Cleanup ICE-breaking candidate". In case it's useful, here are some
   instructions for tackling these sorts of bugs. Maybe take a look?
   Thanks! <3

   cc @AminArria @chrissimpkins @contrun @DutchGhost @elshize @ethanboxx @h-michael @HallerPatrick @hdhoang @hellow554 @imtsuki @jakevossen5 @kanru @KarlK90 @LeSeulArtichaut @MAdrianMattocks @matheus-consoli @mental32 @nmccarty @Noah-Kennedy @pard68 @PeytonT @pierreN @Redblueflame @RobbieClarken @RobertoSnap @robjtede @SarthakSingh31 @senden9 @shekohex @sinato @spastorino @turboladen @woshilapin @yerke
6. rustbot

   added

   ICEBreaker-Cleanup-Crew

   on Mar 26, 2020
7. jonas-schievink

   added

   C-bugCategory: This is a bug.Category: This is a bug.

   A-macrosArea: All kinds of macros (custom derive, macro_rules!, proc macros, ..)Area: All kinds of macros (custom derive, macro_rules!, proc macros, ..)

   on Mar 26, 2020
8. LeSeulArtichaut commented on Mar 26, 2020

   

   LeSeulArtichaut

   on Mar 26, 2020

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   Failed to confirm that #70074 is the cause:
   tested 342c5f33d097b2dc07a2dbc0ca45a37379d2ff60, got Yes
   Seems like it regressed prior to 342c5f3
9. AminArria commented on Mar 26, 2020

   

   AminArria

   on Mar 26, 2020

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   searched nightlies: from nightly-2020-02-26 to nightly-2020-03-04
   regressed nightly: nightly-2020-02-29
   searched commits: from https://github.com/rust-lang/rust/commit/6d69caba110c0c2fb90180df1cbc8be5033b91d4 to https://github.com/rust-lang/rust/commit/0eb878d2aa6e3a1cb315f3f328681b26bb4bffdb
   regressed commit: https://github.com/rust-lang/rust/commit/0eb878d2aa6e3a1cb315f3f328681b26bb4bffdb
   

   For code I used:

   use pin_project_lite::pin_project;
   
   pin_project! {
       pub struct Struct<T: 'static> {
           field: T
       }
   }
   
   
   fn main() {
   
   }

   👍React with 👍1Reacted by Léo Lanteri Thauvin
10. LeSeulArtichaut commented on Mar 26, 2020

    

    LeSeulArtichaut

    on Mar 26, 2020

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    @rustbot modify labels: -E-needs-bisection
11. rustbot

    removed

    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 Mar 26, 2020
12. LeSeulArtichaut commented on Mar 26, 2020

    

    LeSeulArtichaut

    on Mar 26, 2020

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    My progress on an MCVE so far
13. steffahn commented on Mar 26, 2020

    

    steffahn

    on Mar 26, 2020

    Last edited by steffahn

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    Reduced example:

    macro_rules! m {
              (          $(: $p:path)? : $l:lifetime)
        => {m!{@internal $(: $p     )? : $l         }};
    
              (@internal $(: $p:path)? : $l:lifetime) => {};
    }
    
    m! {: 'static}
    
    fn main() {}

    (Playground)

    Errors:

       Compiling playground v0.0.1 (/playground)
    error: local ambiguity: multiple parsing options: built-in NTs lifetime ('l') or path ('p').
     --> src/main.rs:3:38
      |
    3 |     => {m!{@internal $(: $p     )? : $l         }};
      |                                      ^^
    ...
    8 | m! {: 'static}
      | -------------- in this macro invocation
      |
      = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
    
    error: aborting due to previous error
    
    error: could not compile `playground`.
    
    To learn more, run the command again with --verbose.
    
    
14. LeSeulArtichaut commented on Mar 26, 2020

    

    LeSeulArtichaut

    on Mar 26, 2020

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    Split the macro in two parts to make it easier to follow, and removed the special lifetime 'static:

    macro_rules! foo {
        ($(: $p:path)?  $(: $l:lifetime)? ) => { bar! {$(: $p)?  $(: $l)?  } };
    }
    
    macro_rules! bar {
        ($(: $p:path)?  $(: $l:lifetime)? ) => {};
    }
    
    foo! {: 'a }

    (Playground)

    Error:

    error: local ambiguity: multiple parsing options: built-in NTs lifetime ('l') or path ('p').
      --> src/lib.rs:2:66
       |
    2  |     ($(: $p:path)?  $(: $l:lifetime)? ) => { bar! {$(: $p)?  $(: $l)?  } };
       |                                                                  ^^
    ...
    10 | foo! {: 'a }
       | ------------ in this macro invocation
       |
       = note: this error originates in a macro (in Nightly builds, run with -Z macro-backtrace for more info)
    
    error: aborting due to previous error
    

    I think we can now @rustbot modify labels: -E-needs-mcve
15. rustbot

    removed

    E-needs-mcveCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable ExampleCall for participation: This issue has a repro, but needs a Minimal Complete and Verifiable Example

    on Mar 26, 2020
16. LeSeulArtichaut commented on Mar 26, 2020

    

    LeSeulArtichaut

    on Mar 26, 2020

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    I believe that the most probable culprit is #69384, cc @petrochenkov
17. petrochenkov

    self-assigned this

    on Mar 27, 2020
18. LeSeulArtichaut commented on Mar 27, 2020

    

    LeSeulArtichaut

    on Mar 27, 2020

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    #69384 is indeed the culprit, I can reproduce the bug on b2605c1
19. spastorino commented on Apr 1, 2020

    

    spastorino

    on Apr 1, 2020

    Last edited by spastorino

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    This was briefly discussed during pre-triage. Assigning P-high for now until we have a better understanding of what's going on.

    👍React with 👍1Reacted by Léo Lanteri Thauvin
20. spastorino

    added

    P-highHigh priorityHigh priority

    on Apr 1, 2020
21. petrochenkov commented on Apr 4, 2020

    

    petrochenkov

    on Apr 4, 2020

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    Fixed in #70768.
22. petrochenkov

    removed their assignment

    on Apr 4, 2020
23. Dylan-DPC-zz

    added a commit that references this issue on Apr 5, 2020

    Rollup merge of rust-lang#70768 - petrochenkov:macambig, r=Centril,ma…

    ...

    d0dda18
24. bors

    closed this as completedin d0dda18on Apr 5, 2020