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 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.
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>
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.
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>
Includes proposals:
- #990
- #2188
- #2138
- #2200
- #2360
- #2760
- #2964
- #3162
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 and #2483;
- "binding patterns", like `x: i32`, and "bindings" like `x`.
---------
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
First step in updating `docs/design/generics/details.md`. It
incorporates changes from proposals: #989#2138#2173#2200#2360#2964#3162 , but there are still more changes from those proposals to be
made.
It also switches away from suggesting static-dispatch witness tables,
and creates an appendix to describe that decision.
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Change terminology away from terms that are ambiguous:
- Reserve "generic type" for types with (compile-time) parameters, like
`Vector` in `Vector(T:! type)`. Don't use that term to refer to `T`, as
it would with
[#2360](https://github.com/carbon-language/carbon-lang/blob/trunk/proposals/p2360.md#terminology).
- Use the term "compile-time" instead of "constant" to mean "template or
symbolic." Expand the term "constant" to include values, such as from
`let` bindings.
This reflects changes from a number of approved proposals:
- #2138 : "generic" -> "checked generic", "template" -> "template
generic"
- #2360 : "type", "facet type", "facet". Note: I am not using the term
"generic type" from #2360 since that meaning conflicts with the
generally accepted meaning of "generic type" of a type with a
compile-time parameter.
- #2760 / #2770 : internal/external impl -> extending impl
- #2964 : "symbolic constant" and "template constant"
---------
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Introduce a concrete design for how Carbon values, objects, storage,
variables,
and pointers will work. This includes fleshing out the design for:
- The expression categories used in Carbon to represent values and
objects,
how they interact, and terminology that anchors on their expression
nature.
- An expression category model for readonly, abstract values that can
efficiently support function inputs.
- A customization system for value expression representations,
especially as
seen on function boundaries in the calling convention.
- An expression category model for references instead of a type system
model.
- How patterns match different expression categories.
- How initialization works in conjunction with function returns.
- Specific pointer syntax, semantics, and library customization
mechanisms.
- A `const` type qualifier for use when the value expression category
system
is too abstracted from the underlying objects in storage.
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Adrien Leravat <Pixep@users.noreply.github.com>
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This reflects changes from a number of approved proposals:
- #920 : concrete statements about orphan and overlap in Carbon
- #2138 : "generic" -> "checked generic", "template" -> "template
generic"
- #2188 : binding patterns are forbidden in type position
- #2360 : "type", "facet type", "facet". Note: I am not using the term
"generic type" from #2360 since that meaning conflicts with the
generally accepted meaning of "generic type" of a type with a
compile-time parameter.
- #2760 / #2770 : internal/external impl -> extending impl
- #2964 : "symbolic constant" and "template constant"
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This includes:
- Syntax changes from this chart:
| Before | After |
| ------------------------------- | --------------------------------------- |
| `class D extends B { ... }` | `class D { extend base: B; ... }` |
| `external impl C as Sub;` | `impl C as Sub;` |
| `class C { impl as Sortable; }` | `class C { extend impl as Sortable; }` |
| `adapter A for C { ... }` | `class A { adapt C; ... }` |
| `adapter A extends C { ... }` | `class A { extend adapt C; ... }` |
| `interface I { impl as J; }` | `interface I { require Self impls J; }` |
| `interface I { extends J; }` | `interface I { extend J; }` |
- Dropping the syntax for conditionally implemented internal interfaces.
This does not include:
- terminology changes from #2760 ("internal" and "external")
- changes to code, such as explorer, toolchain, language grammars, or other tooling
Allow an `impl` to overlap with a `final impl` if they agree on the overlap. Agreement is defined as all values comparing equal, and functions never comparing equal. Implements the decision in question-for-leads issue #1077.
Use the keyword `impls` instead of `is` when writing a `where` constraint that a type variable needs to implement an interface or named constraint.
What was previously (provisionally) written:
```
fn Sort[T:! Container where .ElementType is Ordered](x: T*);
```
will now be written:
```
fn Sort[T:! Container where .ElementType impls Ordered](x: T*);
```
---------
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Also make minor updates to the skeletal design in
docs/design/name_lookup.md following #2113, as there are no longer any prelude names that are made available to unqualified name lookup by default.
Add `type` to the keyword list in
docs/design/lexical_conventions/words.md, following #2360.
Require `impl as` constraints in an `interface` or `constraint` definition to mention `Self` implicitly or explicitly. Require `where` clauses to refer to `.Self` directly, or through a designator like `.Foo`.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
A number of smaller changes grouped together in one proposal:
- Make `Self` a keyword.
- Clarify that `Self` refers to the current type in a base class and in impl declarations.
- Clarify when `.Self` is legal, and what type it has.
- Also specify that `where` is not an associative operator.
The most significant change here is that explorer now uses the chosen spelling
rather than the old `Bool` spelling. Also update a few documentation examples
and some skeletal design docs to use the chosen spelling.
The previous implementation model involved the caller of a function knowing what impls the function will need. With the addition of blanket impls and specialization to the design, that is in general no longer possible. Instead the caller provides a type which is used as a key to look up the impl, which is expected to occur during monomorphization, though we allow the compiler to employ other strategies when the set of impls is predictable.
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
This proposal:
- Adds support for interfaces requiring other types than `Self` to implement interfaces, as in:
```
interface IntLike {
impl i32 as As(Self);
// ...
}
```
- Defines requirements on how to satisfy those requirements that have a `where` clause.
- Extends `observe` declarations to include saying a type implements an interface, so code can provide a proof instead of the compiler having to perform a recursive search.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This proposal has three main contributions:
- Types with generic parameters have an identity that consists of the types names plus the values of those parameters.
- The parameters of a type may be deduced from a function's argument.
- Types with generic parameters do not support specialization. Instead, a type can delegate to an interface to opt in to allowing specific customization points.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Allow interfaces and implementations to be forward declared.
```
// Forward declare interface `F`
interface F;
class C {
// Forward declare `C` implements `F`
impl as F;
}
// Definitions corresponding to forward declarations
interface F { ... }
impl C as F { ... }
```
To allow members of interfaces with default definitions to be forward declared, prefix them with the keyword `default`, following #1082.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Dana Jansens
Jon Ross-Perkins
Richard Smith
cui fliter
Amr Hesham
Kareem Ergawyandergawy
micttyl
David Poliakoff
Krishna Agarwal
Josh Soref
Ryan Russell