2026-07-27 — Last Week in Carbon

[geoffromer]

News

• Talks from NDC Toronto are now live:
  • Carbon: graduating from the experiment
  • Benchmarking and optimizing the Carbon compiler

Updates on leads issues

• Decisions
  • (none)
• New issues
  • (none)
• Active discussions
  • #5896 C++ interop: Using C++ constructors syntax
    • This is closely coupled to the opposite direction: when/how to export Carbon factory functions as C++ constructors.

Updates on proposals

• Decisions
  • #7299 Ensure `where` requirements in named constraints are visible to lookups
    • Approved and merged.
• New RFC proposals
  • #7536 Proposal: Core.Slice(T) type for indirect storage buffers
    • Discussed on 07-21.
  • #7545 Restrict observe declarations to names that are part of the enclosing interface
• Active discussions
  • #7362 Regularise Carbon destructors
    • Review ongoing

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

• Conduct team updates:
  • DONE: published the transparency report for the past quarter.
• Moderation interventions last week:
  • none
• Activity in the past week:
  • WIP: Turning the project landing page mockup into a PR
  • 2 new contributors! 🎉
  • 11 authors have pushed 25 commits to trunk and 26 commits to all branches.
  • On trunk, 264 files have changed and there have been 5,183 additions and 2,884 deletions
  • We merged 25 PRs, opened 16 additional PRs, and we neither closed nor opened any new issue.

Activity on toolchain

• 07-21 Scalability of observe declarations
• #toolchain Exceptions are silently exiting due to our build flags leaking into runtimes builds.
• #interop Can we remove some code added in #7042?
• #toolchain CI failure due to problems withMac system mangling.
• PRs:
  • Generics and `match_first` in #7538, #7542, #7531, #7546, #7517, #7547, #7553, #7556, #7562
  • DeclaredFacetType in #7528
  • Prelude in #7539, #7559
  • C++ export for classes, functions with generic return types, and constructors in #7537, #7541, #7550, #7560
  • Diagnostic improvements in #7554, #7558
  • Document TypeInstId in #7555
• New contributors:
  • @oli-ej made their first contribution in #7535
  • @pjmlp made their first contribution in #7549

Activity on memory safety

• 07-21 Structured concurrency and thread-local storage

Other active discussions

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

• #error-handling Performance of different approaches to multiple return paths.
• 07-20 Default arguments terminology and relation to pattern matching
• #infra The prelude is failing to build on Compiler Explorer
  • Fixed in #7559
• #naming How to refer to the type of an object's type?
• 07-21 How does the planned Carbon "landing page" relate to the existing website?
• #generics-and-templates How to handle it when interface extension redeclares an associated constant
• #strategy Interview with creator of Zig
• #style Markdown indentation style for lists
• #generics-and-templates How to write an interface that only the toolchain can implement?
• #contributing-help rumdl still isn't doing line wrapping.
• #generics-and-templates Lookup queries inside an impl decl for that impl itself can end up finding other impls which leads to incorrect/incoherent outputs.
• #evolution Do we still intend to support destructors that take var self: Self?
• 07-23 How to opt out of a default destructor (and other default impls)
• #generics-and-templates A .Self in an impl decl causes a look up into the impl itself. But what about Self? Self.(I.X) looks very similar but it’s more concrete, can it find other impls?
• #pattern-matching When and how do type conversions happen during pattern matching?
  • When the pattern has defaults, which type do we convert the scrutinee to?
• #infra FYI #7563 is proposing a new top-level directory integration_tests.
• #getting-started Should extern library count as an anchor name for the orphan rule?

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