XID_Start / XID_Continue might not be quite right #4928

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1. ghost assigned

   graydon

   on Feb 14, 2013
2. catamorphism commented on Aug 19, 2013

   

   catamorphism

   on Aug 19, 2013

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   Bug triage. Re-nominating to change to milestone 1, well-defined.
3. graydon commented on Aug 22, 2013

   

   graydon

   on Aug 22, 2013

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   accepted for backwards-compatible milestone
4. emberian commented on Apr 7, 2014

   

   emberian

   on Apr 7, 2014

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   Non-ascii identifiers are currently feature gated, so this isn't as pressing, but we still need to figure out what to do here. Re-nominating, I don't think this needs to be backcompat.
5. emberian

   added

   I-nominated

   on Apr 7, 2014
6. pnkfelix commented on Apr 10, 2014

   

   pnkfelix

   on Apr 10, 2014

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   Correct, non-ascii idents are feature-gated. Recategorizing as P-low (and not 1.0).
7. pnkfelix

   added

   P-low

   and removed

   P-backcompat-lang

   on Apr 10, 2014
8. brson

   removed

   I-nominated

   on Apr 10, 2014
9. thestinger

   removed

   I-completion

   on Sep 16, 2014
10. yongqli commented on Jun 23, 2015

    

    yongqli

    on Jun 23, 2015

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    I would really like to see Unicode superscripts allowed, as subscripts already are. I would be willing to make a pull request to implement this.
11. steveklabnik commented on Nov 15, 2016

    

    steveklabnik

    on Nov 15, 2016

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    Triage: unicode identifiers are still feature gated, no changes.
12. pnkfelix

    added

    T-langRelevant to the language teamRelevant to the language team

    on Nov 18, 2016
13. Mark-Simulacrum

    added

    C-enhancementCategory: An issue proposing an enhancement or a PR with one.Category: An issue proposing an enhancement or a PR with one.

    and removed

    A-frontendArea: Compiler frontend (errors, parsing and HIR)Area: Compiler frontend (errors, parsing and HIR)

    on Jul 19, 2017
14. rurban commented on Nov 9, 2017

    

    rurban

    on Nov 9, 2017

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    XID_Start / XID_Continue has one small bug, and is not enough to get proper unicode identifiers safe. See also http://websec.github.io/unicode-security-guide/
    You need to add mixed script protections (TR39 Restriction levels), normalize them (to NFC or NFKC_Casefold), and maybe disallow confusables.
    A short overview is here: http://perl11.org/blog/unicode-identifiers.html

    bug: U+3164 HANGUL FILLER and U+ffa0 are wrongly specified as ID_Continue. Disallow these.
15. Centril commented on Oct 29, 2018

    

    Centril

    on Oct 29, 2018

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    Closing in favor of #55467.
16. Centril

    closed this as completedon Oct 29, 2018
17. SimonSapin commented on Oct 29, 2018

    

    SimonSapin

    on Oct 29, 2018

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    @Centril, is this specific issue actually addressed in rust-lang/rfcs#2457 or tracked in #55467? As far as I can tell they specify unmodified XID_Start and XID_Continue.
18. Centril commented on Oct 29, 2018

    

    Centril

    on Oct 29, 2018

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    @SimonSapin at least tracked in that issue to consolidate; tho I didn't read the issue description in detail.
19. SimonSapin commented on Oct 29, 2018

    

    SimonSapin

    on Oct 29, 2018

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    I’ve added this as a checkbox in Unresolved Questions in #55467
20. RalfJung

    added a commit that references this issue on Mar 30, 2026

    Merge pull request rust-lang#4928 from RalfJung/open-flag-sub

    ...

    2791e43
21. U007D

    added a commit that references this issue on Aug 21, 2026

    Merge rust-lang#4928

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    19701b3