- A parameter binding can be marked `ref` instead of `var` or the
default. It will bind to reference argument expressions in the caller
and produces a reference expression in the callee.
- Unlike pointers, a `ref` binding can't be rebound to a different
object.
- This replaces `addr`, and is not restricted to the `self` parameter.
- A `ref` binding, like a value binding, can't be used in fields of
classes or structs.
- When calling functions, arguments to non-`self` `ref` parameters are
also marked with `ref`.
- The return of a function can optionally be marked `ref`, `val`, or
`var`. These control the category of the call expression invoking the
function, and how the return expression is returned.
- These may be mixed for functions returning tuple or struct forms.
- The address of a `ref` binding is `nocapture` and `noalias`.
- We mark parameters of a function that may be referenced by the return
value with `bound`.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
In open discussion[1] we decided that "identical" rewrites would mean
that for a given LHS value, all RHS have the same value (after
evaluation), rather than requiring the RHS to all have the same
syntactic value. This means the following is valid, since the value of
`.Y` is known to be `()` while resolving the rewrite constraints of `T`.
So both rewrites of `.X` are resolved to `.X = ()`:
```
fn Identical(T:! I where .X = () and .X = .Y and .Y = ()) {}
```
The implementation of this clarification, along with test cases encoding
it, is done in https://github.com/carbon-language/carbon-lang/pull/5686.
Clarify this in the language design documents, and improve some other
clarity while we're there:
- The prose talks about a facet `T`, but the examples were using `A` as
its name. Change the facet to be `T`. This means changing the `.T`
associated constant (and `.U` and `.V`) to be `.X` (and `.Y` and `.Z`).
While doing this, use `I` for the interface name instead of `C`, which
we use more commonly for a class type name.
- Correct the comments in the cycle example that claim we find `.Y then
.Y* then .Y**`. In this example `.Y = .Z* and .Z = .Y*` which adds _two_
levels of pointers when evaluating `.Y`: `.Y => .Z* => (.Y*)* => .Y**`
[1]
https://docs.google.com/document/d/1Yt-i5AmF76LSvD4TrWRIAE_92kii6j5yFiW-S7ahzlg/edit?tab=t.0#heading=h.qti4vn50zwy
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
This proposal re-affirms (with additional rationale) that a `var`
pattern
declares a durable complete object, and refines the terminology for
binding
patterns in a `var` pattern to be more explicit about the intended
semantics. It
also makes several other changes and clarifications to the semantics of
pattern
matching on objects:
- The storage for a variable pattern is initialized eagerly, rather than
being
deferred until the end of pattern matching.
- Any initializing expressions in the scrutinee of a `match` statement
are
materialized before matching the `case`s.
- An initializing expression can only initialize temporary storage or a
single
variable pattern, not a tuple/struct pattern or a subobject of a
variable
pattern. Removing this limitation is left as future work.
Finally, as a drive-by fix, it clarifies what parts of the `match`
design are
still placeholders.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Fix destructor syntax ambiguity by switching to `fn destroy` mirroring
standard function syntax. This is a purely syntactic change, maintaining
destructor semantics.
This comes from leads question #4999
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
I believe this reflects the intent, but the phrasing of "even if
`MyBaseClass` is not" implies that `MyBaseClass` _can_ be final in
`partial MyBaseClass`. Also, make clear it's allowed on `abstract`
classes, not only `base` (this seems explicitly intended from the
`MyAbstractClass` example around line 1482).
Introduce a principle that the Carbon language should not encroach on
the
developer's namespace. Satisfy this principle by making `Core` a
keyword.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
The WORKSPACE file is deprecated; support is already off by default, and
it'll be removed in the next major bazel release. Our main dependency is
tree-sitter, and I'm trying to address that here.
We're currently using https://github.com/elliottt/rules_tree_sitter, but
that hasn't been updated in a couple years, meaning it lacks
MODULE.bazel support. In the registry, there's
https://registry.bazel.build/modules/tree-sitter-bazel, but this is only
the *parser* libraries of tree-sitter, not the *generator*. I'm using it
for that much, at least.
For the *generator*, which transforms grammar.js to parser.c/h, I'm just
requiring a non-hermetic invocation (i.e., people who want to work on it
will need to install tree-sitter; see the README.md updates). I tried
running it manually, but parser.c is about 600 KB; pre-commit rejects
files that large and I don't think an exception makes sense to override
for this (it'd probably also grow substantially if the grammar were
updated to cover more syntax). In order to make the non-hermetic call
not break "bazel build //..." for most developers, I'm marking most
targets in the package as manual.
Note, I did look long and hard at using `aspect_rules_js`/`rules_nodejs`
to invoke npm. This took a lot of time, and I have a commit that's
mostly working, except I hit a point where it uses `declare_symlink`
which we disallow for compatibility reasons (commit "Lots of work for
figuring out rule_js uses declare_symlink" on the PR). As a consequence,
I think we can't use the primary supported ways to have hermetic npm
calls.
Also, `treesitter` -> `tree_sitter` because it's generally called
`tree-sitter`, two words. We even had a `treesitter/src/tree_sitter`
directory so it's a bit inconsistent.
As far as bugs here, the parser library breaks bazel queries, e.g. the
error:
```
ERROR: Evaluation of query "somepath(//..., @llvm-project//third-party/unittest:gtest)" failed: preloading transitive closure failed: no such package '@@[unknown repo 'platforms' requested from @@tree-sitter-bazel+]//': The repository '@@[unknown repo 'platforms' requested from @@tree-sitter-bazel+]' could not be resolved: No repository visible as '@platforms' from repository '@@tree-sitter-bazel+'
```
I'm just excluding tree_sitter from queries where I can to work around
the error.
Proposes a set of core features for declaring and implementing generic
variadic
functions.
A "pack expansion" is a syntactic unit beginning with `...`, which is a
kind of
compile-time loop over sequences called "packs". Packs are initialized
and
referred to using "pack bindings", which are marked with the `each`
keyword at
the point of declaration and the point of use.
The syntax and behavior of a pack expansion depends on its context, and
in some
cases by a keyword following the `...`:
- In a tuple literal expression (such as a function call argument list),
`...`
iteratively evaluates its operand expression, and treats the values as
successive elements of the tuple.
- `...and` and `...or` iteratively evaluate a boolean expression,
combining
the values using `and` and `or`, and ending the loop early if the
underlying
operator short-circuits.
- In a statement context, `...` iteratively executes a statement.
- In a tuple literal pattern (such as a function parameter list), `...`
iteratively matches the elements of the scrutinee tuple. In conjunction
with
pack bindings, this enables functions to take an arbitrary number of
arguments.
---------
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
This adds language to explain where the types of constraints can or can
not appear (attached-to an impl-as vs in-a type expression). And
describes the impact of using a rewrite vs same-type constraint inside
the body of the affected code, and thus why a rewrite is preferable when
the constraint is of a single facet type.
The prettier pre-commit mirror is no longer supported
(https://github.com/pre-commit/mirrors-prettier). This switches to a
direct call, and updates to 3.3.3. And I'm now specifying types for it
to apply to, rather than letting it ignore unknown files; overall just
trying to separate out which linter sees what.
To comment on formatting changes:
- In most cases, seems to be getting confused by `[]` use in markdown
when it's not part of a link. This looks like a regression, but not one
we're broadly affected by.
- p0107.md - caught an issue with a malformed broken bad link which I've
tried to fix.
- p3720.md - looks like a fix.
Note, prettier has a 4.0.0 alpha release. As best as I could tell, that
only affected the .prettierrc.yaml processing. I changed the glob there
for forwards compatibility.
The name ComparableFromDifferenceFn comes from the next example. In this
example ComparableFromDifference is the name of the class that will be
implictly cast to a Facet matching Comparable.
Trying to pull in key elements of #3762, #3763, and #3980 (decl matching
and `extern`, essentially). These aren't specific to any particular
declaration type, but are common to entities, so suggesting a new doc
oriented on that.
There's probably more that could be said here, I'm just focused on
getting the recent formal discussion mirrored into the design.
---------
Co-authored-by: josh11b <15258583+josh11b@users.noreply.github.com>
Update the operator precedence to achieve a few goals:
- Form operators into groups which behave similarly
- Make the group of operators ("top-level operators") that capture
everything to the right, like `if`...`then`...`else`, behave similarly
to the left, so that rearranging expressions won't change how they
group.
- Add the `where` operator, used to specify constraints on facet types,
to the precedence chart, to define how it interacts with other
operators.
- Make the operator precedence diagram prettier, so that it eventually
can be made into a poster that Carbon programmers can hang on their
walls.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
The current approach was done to work-around a limitation that we can
only have a single link per box, but is unscalable. Instead have a
single link to a new sections of the document that describes the box,
and has multiple links.
---------
Co-authored-by: Josh L <josh11b@users.noreply.github.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Update broken links to aid in following links while perusing the
documentation. Closes#3778
I don't imagine I got every one of these right. Some 404s may be
reported due to permissions.
Using the lychee command in #3778, only the following link is reported
as not found, but it's just a permission issue:
```
[proposals/p1367.md]:
✗ [404] https://github.com/carbon-language/carbon-lang/settings/access | Failed: Network error: Not Found
```
I tried to get it down to as few as possible, partially so that future
link scans won't run into repeat errors.
---------
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Carbon Infra Bot <carbon-external-infra@google.com>
Improve the exposition of the design changes from #3646 to integrate
better into the overall description of member access design.
This fixes the incorrect description of the rules for `->` by instead
relying on the general rule that `->` is rewritten to use `*` and `.`
before any other processing is done, and generally makes
*integer-literal* names be less of a special case.
Add support for extracting elements of a tuple by their numerical index.
Also formally add the well-established basic syntactic and semantic
rules for
tuples, for which we have had leads issues but no proposal, into the
design.
The version of `flake8` was too old to support with Python 3.12 -- there
is new F-string support that caused false positives sadly. The updated
version has fixes for all of these.
This in turn updates codespell which has picked up several new fixes
that actually fire in our code, so also fix everything. While we don't
do more in-depth updates to old proposals, similar to simply fixing
broken links, fixing automatically detected typos seems scalable and
fine.
All edits were automatically generated here.
- Require namespace members be declared in the same name scope as the
namespace is declared.
- Allow binding patterns to directly declare names in namespaces.
- Disallow using different namespaces in the same binding pattern.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
When there is no `package` directive, default to `Main//default api`
instead of
`Main//default impl`. This means:
- The extension will be `.carbon`, not `.impl.carbon`.
- There can only be one such file when compiling.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Continued from part 1: #3231. Second step updating
`docs/design/generics/details.md`. There remains some work to
incorporate proposal #2200.
- The biggest changes are incorporating much of the text of proposals:
- #2173
- #2687
- It incorporates changes from proposals:
- #989
- #1178
- #2138
- #2200
- #2360
- #2964
- #3162
- It also updates the text to reflect the latest thinking from leads
issues:
- #996
- #2153 -- most notably deleting the section on `TypeId`.
- Update to rule for prioritization blocks with mixed type structures
from [discussion on
2023-07-18](https://docs.google.com/document/d/1gnJBTfY81fZYvI_QXjwKk1uQHYBNHGqRLI2BS_cYYNQ/edit?resourcekey=0-ql1Q1WvTcDvhycf8LbA9DQ#heading=h.7jxges9ojgy3)
- Adds reference links to proposals, issues, and discussions relevant to
the text.
- Also tries to use more precise language when talking about
implementations, to avoid confusing `impl` declaration and definitions
with the `impls` operator used in `where` clauses, an issue brought up
in
- #2495
- #2483
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Geoff RomerandJon Ross-Perkins
Boaz Brickner
Ivan Duranandjosh11b
David Blaikie
cui fliter