2026-05-11 — Last Week in Carbon

[josh11b]

News

• There were 2 talks about Carbon at NDC Tornoto!

Updates on leads issues

• Decisions
  • (none)
• New issues
  • (none)
• Active discussions
  • #7138 How to treat ambiguous .Self?

Updates on proposals

• Decisions
  • #5990 Principle: The signature is the contract
    • Withdrawn. Instead #7179 adds something to the information accumulation principle.
• New RFC proposals
  • (none)
• Active discussions
  • #7016 Updating self syntax and adding static member variables
    • No concerns with the overall direction, just drilling into some of the details and phrasing in the design.
  • #7140 Orphan rule for scopes
    • Positive reviews

Updates on moderation across our community spaces (Discord and GitHub)

• Conduct team updates:
  • none
• Moderation updates last week:
  • Banned an account after Automod detected a spamming attempt.
  • Discussed how we want to deal with GitHub issues we deem labelled incorrectly, including “questions for leads”.
  • BLOCKED: discussing if and how we want to share self-learning quizzes related to our community culture more broadly
• Activity in the past week:
  • 1 new contributor! 🎉
  • 9 authors have pushed 18 commits to trunk and all branches.
  • On trunk, 446 files have changed and there have been 21,568 additions and 15,951 deletions
  • We merged 18 PRs, opened 5 additional PRs, closed 1 issue, and opened 2 new issues.

Activity on toolchain

• 05-05 Some changes that would be nice for demoing, e.g. at NDC Toronto
  • 05-07 Making Run without a return use 0
• 05-05 Support negate operation on float literals so the code from old newsletters works
• 05-07 How to clone patterns
• #toolchain Clang might need Check during Lower - some things can move to sem_ir to be shared, might need some other shared location
• #toolchain BundleStore and printing raw SemIR
• #toolchain Importing C++ range-based-for-able types to Carbon for interface, toolchain support for necessary interface features
• #toolchain Compiler explorer V test divergence due to LLVM IR optimizations running in the former and not the latter
• #toolchain TryEvalTypedInst<SemIR::SymbolicBinding semantics
• #interop Given a direction that uses call-site specific mappings for Carbon calling C++ function signatures, how should we handle virtual functions, where the call site/syntax can’t be known
• PRs:
  • .Self in #7147 #7133
  • nested facet types in #7139
  • impl declarations in #7161 #7164 #7170
  • Carbon destructors from C++ in #7143
  • BundleStore in #7173
  • mangling in #7177
  • impl lookup in #7178
  • Run return in #7180
  • C++ comparison operators in #7163
  • others in #7166 #7172 #7176 #7175 #7184
• New contributors:
  • @hystericca made their first contribution in #7175

Activity on memory safety

• #safety Unstructured thread creation effects should not be stopped by being done in a structured thread scope
  • Structured concurrency API described in Notes on structured concurrency, or: Go statement considered harmful — njs blog

Other active discussions

These include Discord Chat, GitHub Discussions, or open discussion sessions.

• #infra Still working out the kinks in the dependent-PR bot.
  • Note that it assumes PRs can't depend on PRs with higher numbers.
• #generics-and-templates 05-04 Making the orphan rule incorporate scope restrictions
• #error-handling Blog post about adding context during error propagation.
• 05-04 05-05 05-07 Two Carbon talks at NDC Toronto
• 05-04 str and strbuf proposal
• #infra FizzBot will now remind you when your PRs are waiting for action from you.
• #generics-and-templates How to tell when two scopes are the same scope.
• #naming Should we rename Inst::ArgAndKind to AnyId?
• #style Why does ssize_t perform better than size_t?
• #generics-and-templates How to get the ConstantDependence of a SpecificId?
• #contributing-help How to resolve the issue with Run() -> () leading to an uninitialized exit code?
• #language-questions Can deduction see through an optional? Also, how to make an interface for functions with a given signature?
  #generics-and-templates Can an inst have a concrete constant value but a symbolic type?
• #generics-and-templates ImplWitnessAccess was being treated as a concrete type unconditionally by type iterator, but it can be symbolic
• #general-design How will memory allocation work in Carbon? Will it be separate from initialization?
• #getting-started When will the talks from NDC Toronto be public?
  • Unknown, but we'll announce them in #strategy when they are.
• #contributing-help How can I get information about discussions in the past week?
• #language-questions Will we make any guarantees about equality of functions with identical definitions?
  • Will there be a way for types to expose states that can be "stolen" for use as sentinels (e.g. nullopt)?

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