Also:
- Introduce `buf` so that existing examples using arrays can be updated
to use it.
- Update the examples linked to on the Carbon front page to something
closer to what we expect, moving away from old array syntax. Uses
`slice` though that name hasn't been settled. Updating the SVGs actually
referenced will need to be done as a separate step.
- Update links to the expression operators while I'm touching that
section.
Assisted-by: Gemini via Antigravity
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Nicholas Bishop <nbishop@nbishop.net>
Implements proposal #7016: `self` moves from the deduced implicit list
(`fn F[self: Self]()`) to the front of the explicit list. Its type may
be written explicitly (`fn F(self: Self)`) or omitted, in which case it
defaults to `Self` (`fn F(self)`, `fn F(ref self)`); `self` in the
implicit list is rejected.
Throughout checking, `self` is modeled as the first explicit parameter.
Because a method is just a function whose first parameter is `self`, it
can also be called as an ordinary function with the receiver passed
explicitly (`Type.M(obj, ...)`), not only as `obj.M(...)`. A new
`SemIR::CallArgParamPatterns` helper chooses the parameters matched
against the explicit arguments, excluding a leading `self` only when it
is supplied as a method-call receiver; arity checking, conversion, and
generic deduction use it. The resulting SemIR and lowering are
unchanged: `self` is still `call_param0`, and witnesses, thunks, and
vtables are unaffected.
An omitted `self` type is parsed as a `SelfBindingPattern` node with no
type expression; checking synthesizes the `Self` type so it behaves
exactly like `self: Self`. However, the exact spelling used must match
between a forward declaration and a definition, following #3763's rules
around declaration matching.
Generated functions, thunks, and C++ interop import/export build `self`
as the first explicit parameter, and the `self`-type override (e.g.
Derived->Base for a virtual override) applies to the explicit `self`.
Placement is validated by new diagnostics: `SelfInImplicitParamList`,
`SelfNotFirstParam`, and `SelfOutsideParamList`. The benchmark source
generator and the documentation adopt the `(self)` shorthand; the
prelude, the examples, and the test data are migrated in the following
commits.
Assisted-by: Claude Code with Claude Opus 4.7
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
My understanding is that `auto` is encouraged even when there's no
applicable naming convention for the variable, and that suffixes like
`_id` are encouraged where applicable, even if the type is explicit, so
there's really no connection between the two policies.
This proposal clarifies some unclear aspects of the interop support for
object-like macros. In particular:
- Carbon supports importing an object-like macro if its definition can
be evaluated as a constant expression, without further restrictions on
that definition.
- When importing the result of that evaluation, C++ lvalues are imported
as references, and rvalues are imported as values.
This provides a native harness with several advantages over
`pre-commit`:
- Faster when initializing the cache
- Smaller cache sizes: under 43mb compared to over 62mb
- Better integration with `uv` for Python usage
Steps for migrating for existing contributors:
1. Install `prek` following instructions in the updated docs.
2. Replace hooks in an existing checkout with a special flag:
```sh
prek install --overwrite
```
The `--overwrite` flag is what removes the old hooks.
If you used the pre-push variant:
```sh
prek install --hook-type pre-push --overwrite
```
3. Optional cleanups:
```sh
rm -rf ~/.cache/pre-commit # reclaim the old hook-environment cache
pipx uninstall pre-commit # if installed via pipx; or `brew uninstall
pre-commit`
```
Assisted-by: Antigravity with Gemini
Update the orphan rule to require a name to be defined within, or by,
the same scope as the impl declaration. Since libraries can not be
nested, this also enforces the old rule, but rejects more impl
declarations. In particular, it rejects an impl declaration in a generic
context which would have no way to provide a value for the generic
bindings it inherited from its enclosing scope, making the impl
unusable.
Discussed in open discussion
[2026-05-04](https://docs.google.com/document/d/1mjllGO3ZCL4qGt9uJHUtcxKoHAGEY7Y999ie4EtBWB8/edit?tab=t.3ifnhz83n73d#heading=h.p45zfugbmdih).
Instead of requiring just one to have a designator, require each one.
You can't write `(type where A == B) & (type where C == .Self)` because
`A == B` has no designator. If the two facet types are combined into a
single `where` syntactically, their meaning does not change, and what we
allow should not change either. That is, `type where A == B and C ==
.Self` should be rejected since `A == B` does not contain a designator.
The design is also updated to make this clear.
Note that #7266 has already updated the toolchain for `char`, but not
`Core.CharLiteral`.
Assisted-by: Gemini via Antigravity
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Geoff Romer <gromer@google.com>
We've talked about adding the title to the filename several times over
the years and it seems really valuable. This requires us to compute a
"slug" for the title spelling that can be part of the filename.
Beyond that, we crossed 7000 recently, and so it seems likely that we
will need to add digits sooner rather than later here, so this goes
ahead and moves us to 6 digits so we don't have to adjust again for a
reasonable length of time.
To implement this and ensure we can sustain it going forward this adds a
tool to our pre-commit that validates (and corrects if needed) the
filename.
In order to update everything and keep links working, there are a _lot_
of changes, but the most interesting for direct review are in
`proposals/scripts`.
Assisted-by: Antigravity with Gemini
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This removes the need to install any specific version of Python or
figure out how to configure it by instead asking users to install `uv`
and letting it manage Python. Among other advantages, `uv` is designed
to be fast enough to embed directly into our scripts.
We were already using this in `bench_runner.py` so that the script could
import non standard library dependencies. Moving to it for the rest of
our Python unifies the approach and will also enable dependencies
whenever needed.
I've left `github_tools` alone as it has special handling with its own
Bazel setup.
I've updated the contributing tools to explain the approach here.
`@` refers to the current workspace's working copy, but if we want the
command to respect the working copies of other workspaces, we should use
`working_copies()` instead; see
https://docs.jj-vcs.dev/latest/revsets/#functions .
Also remove `all() &` while here, since it is always redundant.
Assisted-by: Google Antigravity
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Update the syntax for class (and interface/`impl`) methods to move
`self` into
the parameter parentheses `()` and make the type in its binding optional
(defaulting to `Self`). Introduce the `static` keyword for non-instance
member
variables to indicate static storage. Reflects the decision in leads
issue
[#6931](https://github.com/carbon-language/carbon-lang/issues/6931).
Updates the directly relevant design, but leaves a systematic update of
examples
to a future PR.
Assisted-by: Antigravity with Gemini
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
jj moved the repo config outside the repo. The config.toml might exist
as a symlink in older repos (probably migration), but not clean repos.
So, overall, just switching the advice setup to make it a bit more
robust with config locations.
Also adding "trunk" to the repo config.
Assisted-by: Google Antigravity with Gemini
This gives a setup where `jj b a` / `jj bookmark advance` can reliably
be used to advance a bookmark for a github pull request, without
advancing other bookmarks such as `trunk` or pointing the bookmark at an
empty commit.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Also increases the default optimization to `-Og` which is likely to give
faster turn-around time which is what we want to optimize for here. This
should also _substantially_ shrink binary sizes, etc.
ASan is still available via `--config=asan`, and is added to the CI
infrastructure. However, my current thought is to only run it after push
rather than in PRs and in the merge queue.
Allow partially identifying a named constraint inside its definition,
and allow the query self in an impl lookup with a non-identified facet
type to be used to provide witnesses from that facet type. This allows
impl lookup on `Self` to find `require` decls that have been written
earlier in the named constraint, so that the named constraint to be used
to provide witnesses from inside its definition.
But disallow an incomplete named constraint from being part of an
identified facet type, to prevent forming facet values that store a
witness set that can be invalidated as the named constraint adds
interfaces to its identified facet type.
This was discussed in open discussion [on
2026-03-12](https://docs.google.com/document/d/1mjllGO3ZCL4qGt9uJHUtcxKoHAGEY7Y999ie4EtBWB8/edit?tab=t.0#heading=h.1dvbbrp5a6t3).
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
In addition to the general updates, this switches to a required python
3.10 for pre-commit (3.9 is losing support from black).
Note endpoints for build actions are expanding significantly: see
https://app.stepsecurity.io/github/carbon-language/carbon-lang/actions/runs/22779388360?tab=recommendations&jobId=66080970460
for example, I think just the sources are being increased as a
side-effect of updates (and possibly also things not performing as well
as they should have before).
Similarly allowing sudo in pre-commit because it was actually causing
errors in part of build setup, which used sudo to remove files.
Assisted-by: Google Antigravity with Gemini
Giving both of these their own sections under optional tools because I'm
mainly doing this to share example configs.
Assisted-by: Google Antigravity with Gemini
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This proposal defines the concrete technical mechanisms for C++
interoperability. It specifies the precise syntax and semantics for
importing
C++ APIs. This includes the `import Cpp library "..."` and implicitly
importing
C++ built-in entities, and the establishment of the `Cpp` package as the
dedicated namespace for all imported entities.
This PR also includes high level language C++ Interop design and the
basics of importing C++ APIs and function calling.
Leaving plenty of TODOs to make it easier to fill in more details in
followups.
Part of #4666.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
This proposal introduces the concept of a _form_, which is a
generalization of
"type" that encompasses all of the information about an expression
that's
visible to the type system, including type and expression category.
Forms can be
composed into _tuple forms_ and _struct forms_, which lets us track the
categories of individual tuple and struct literal elements.
The proposal PR also adds `ref` bindings to the pattern matching
documentation,
but that is not part of the proposal itself; it's just bringing the
documentation
up to date with proposal
[#5434](https://github.com/carbon-language/carbon-lang/pull/5434).
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
Adding the note about recursion because it occasionally comes up, and
I'm thinking it'd be helpful to document why we prefer iterative
algorithms.
Also moves a few long style points to headers so that they're easier to
link (I wasn't sure it makes sense to do to all of "syntax and
formatting", but either way what's remaining is shorter if that _is_
linked for reference).
---------
Co-authored-by: Dana Jansens <danakj@orodu.net>
This proposal removes the definition of the term "value binding" as a
primitive
category conversion from reference to value, replacing it with the term
"value
acquisition". The other meaning of "value binding", a binding declared
by a
value binding pattern, is unchanged.
Proposal [p5337](https://docs.carbon-lang.dev/proposals/p5337.html)
renamed and introduced new syntax for extending an interface or named
constraint with another.
- The `require` keyword can now be modified by `extend`, instead of it
being a separate thing altogether.
- Interfaces can `extend impl as I` to gain the members of `I` and
implicitly use them to implement `I`. Named constraints can not.
The `Identity` example is meant to not know anything about the type of
the object its passing through, but it ends up making a copy of it. Fix
the example to not by using a pointer.
~~Added explanatory comment about math package usage~~
Changed Main() entry point to Run() as per design and toolchain
This small update of front page code snippets will add
explanatory comment to highlight that provided Carbon code
is hypothetical and meant to show the look and feel of the language.
Also it delivers change of Main() to Run() to
highlight correct entry point for Carbon lang.
Updates the documentation under `docs/design/` to use `ref` instead of
`addr` after their removal in #5434. Care was taken to manually clean up
edge cases and, in a couple cases, surrounding text (see
3d72c49bb75c0f40ca7e8114b6a1369b941e1697). After this change, there are
no matches for `addr(?!ess)` in `docs/design/`.
Closes#6032
Require language design proposals to either update the design documents
to
reflect the proposed changes, or add "TODO" comments to mark where those
changes
will be needed, with links back to the proposal. This is intended to
ensure that
the design documentation accurately informs readers about the current
language
design, without excessively burdening the proposal process.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
# Changes
## Terminology Updates
This PR updates documentation to align with the expression phase
terminology changes introduced in
[#2964](https://github.com/carbon-language/carbon-lang/pull/2964):
* **"symbolic value" → "symbolic constant"**: Updated all remaining
instances using find-and-replace
## Scope of Changes
* Focused on documentation that predates the July 2023 terminology
change
* Used git blame history to identify instances likely using the old
"constant" definition
* Manually reviewed each "constant" usage to distinguish between:
- New definition (unchanged): the broader category including symbolic
constants
Closes
[#5599](https://github.com/carbon-language/carbon-lang/issues/5599)
---------
Co-authored-by: Hitesh Joshi <hitesh@mitsu.care>
josh11bandJosh L
Chandler Carruthandjosh11b
Richard Smith
Geoff Romer
Jon Ross-Perkins
Nicholas Bishop
Özgür
Burak EmirandDana Jansens
gleb
Calvin
Hitesh JoshiandHitesh Joshi