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.
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>
Updated string_literals.md to mitigate confusion around newline behavior
in the context of block string literals.
Addresses #2887
---------
Co-authored-by: jonmeow <jperkins@google.com>
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.
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.
Use `"` for simple string literals and `'''` for block string literals.
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This follows #1274 , #1325 , #1328 , #1336 , and #1347 . This has miscellaneous changes to the design overview without a particular focus.
Also adds some missing keywords to our list of keywords.
Co-authored-by: Jon Ross-Perkins <jperkins@google.com>
Reorganizes the sections, and makes a pass filling in and updating the first sections including: types, functions, user-defined types. The following sections are left for part 2, including names, generics, and interop.
Also some smaller updates to, not revisiting the text: `pattern_matching.md`, `control_flow/return.md`, and `lexical_conventions/numeric_literals.md`
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Operators rewrite to calls of specific operator interface functions, so you overload an operator for a type by implementing an interface for it. There is a `like` operator for defining a set if implementations for supporting implicit conversions more conveniently.
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This proposal introduces a conditional operator of the form:
```
if cond then value1 else value2
```
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
Allowing interfaces to define default values for its associated entities. This:
- Helps with evolution by reducing the changes needed to add new members to an interface.
- Reduces boilerplate when some value is more common than others.
- Addresses the gap between the minimum necessary for a type to provide the desired functionality of an interface and the breadth of API that user's desire.
As an alternative, final values can be provided instead, which can't be overridden, but are more predictable for users and may avoid dynamic dispatch overhead in some cases.
Example:
```
// Interface parameter has a default of `Self`
interface Add(Right:! Type = Self) {
// `AddWith` *always* equals `Right`
final let AddWith:! Type = Right;
// `Result` has a default of `Self`
let Result:! Type = Self;
fn DoAdd[me: Self](right: Right) -> Result;
}
impl String as Add() {
// Right == AddWith == Result == Self == String
fn DoAdd[me: Self](right: Self) -> Self;
}
```
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
This proposal describes `where` clauses that can add constraints on a type-of-type, for example define restrictions on its associated types. Example:
```
fn FindFirstPrime[T:! Container where .Element = i32]
(c: T) -> Optional(i32) {
// The elements of `c` have type `T.Element`, which is `i32`.
...
}
fn PrintContainer[T:! Container where .Element is Printable](c: T) {
// The type of the elements of `c` is not known, but we do know
// that type satisfies the `Printable` interface.
...
}
```
Some other constraints, such as `Sized` are defined as type-of-types directly, possibly parameterized.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Co-authored-by: Chandler Carruth <chandlerc@gmail.com>
This proposal provides an `as` expression for casting. This supports implicit conversions plus some safe and unsurprising conversions that we do not support implicitly:
* lossy but fully defined conversions to floating-point types
* conversion from `bool` to integer types
* conversion between adaptors and their adapted type, and more generally between compatible types
This facility can be extended by implementing the `As(TargetType)` interface for a type.
Co-authored-by: Geoff Romer <gromer@google.com>
Co-authored-by: josh11b <josh11b@users.noreply.github.com>
This list was extracted from currently-approved proposals and
corresponding design documents. This is intended to be a summary of the
status quo, not a change.
This is based on discussion on #732: that we should probably parse the invalid whitespace, then reject it as part of string validation, rather than having different parses. I worry the question of "how is this parsed" may lead to subtly unexpected results if we aren't consistent, so I'm switching the logic from the lexer to the unescape library (and also adjusting the list of rejected whitespace).
I've modified the text from the proposal slightly, focusing the overview more on a design setup, but mostly kept the details. One important thing here is I noticed that raw tab characters are disallowed -- this was a little buried before, and I've now updated the list of characters allowed in a string to exclude tabs. Additionally, I've noted `\0D` in the list of escapes as explicitly invalid.
Co-authored-by: Richard Smith <richard@metafoo.co.uk>
Adopts new copyright and markdown toc checks.
The new toc check generates the toc header, so that's why all the md files changed (this had felt better to me for the long-term, more auto-generated content)
Jon Ross-PerkinsandChandler Carruth
Richard Smith
josh11bandChandler Carruth
mx42andjosh11b
T.J. Givenandjonmeow
Aswin ShailajanandAvi Aaron
Aleksey Kladov
Jon Meow
Richard Smith