Carbon language support

[jambo-posready-embedded-7]

Adds support for the Carbon language. Carbon is an experimental language developed by Google.

• Source code repository (carbon-language/carbon-lang)

Checklist

• I am adding a new language.
  • The extension of the new language is used in hundreds of repositories on GitHub.com.
    • Search results for each extension:
      • .carbon: https://github.com/search?q=path%3A*.carbon&type=Code&ref=advsearch&l=&l=
  • I have included a real-world usage sample for all extensions added in this PR:
    • Sample source(s):
      • .carbon: 6193d8e#diff-e2449d8cdec8d56e7a85d9ef16521ab0192a58afe147dbe907d3cac76d3b0fab
  • I have included a syntax highlighting grammar
  • I have added a color
    • Hex value: #222222
    • Rationale: Carbon uses a black circle with a C in it. This is not #000000, but they are similar.
  • I have updated the heuristics to distinguish my language from others using the same extension.

Closes #6013

[lildude]

Please follow the CONTRIBUTING.md instructions. We will also need a search result for each extension.

[jambo-posready-embedded-7]

A basic sample in /samples/Carbon, and fixed the multiple extensions problem (.carbon is the most accepted extension, so I excluded .cb)

[lildude]

Do you really want to add support without syntax highlighting? Normally the only reason people add support for a language is to get syntax highlighting on GitHub.

[jambo-posready-embedded-7]

There is no syntax highlighter for it avaliable, although I may try to add one in the future.

[Alhadis]

@btdw Usually when we add support for a language that doesn't have a syntax highlighting grammar (or one released under a permissive license), we sometimes use another language's grammar as a fallback that happens to produce "good enough" highlighting. For example, here's one of your Carbon samples highlighted using Rust:

(Click to toggle)

package Shapes api;
import Math;

// Circle

class Circle {
    var Radius: f32 = 1;
    const var Diameter: f32 = self.Radius * 2;

    const var Pi: f32 = Math.Pi;

    fn Area() -> self;
    fn Circumference() -> self;
}

fn Circle.Area() -> self {
    return Math.Pi * .Radius ^ 2
}

fn Circle.Circumference() -> self {
    return 2 * Math.Pi * .Radius
}

// Rectangle

class Rectangle {
    var Width: f32 = 3;
    var Height: f32 = 1;

    fn Area() -> self;
}

fn Rectangle.Area() -> self {
    return .Width * .Height;
}

// Square (Note: Provides same functions as "Rectangle" class.)

class Square {
    var Width: f32 = 3;
    var Height: f32 = 1;

    fn Area() -> self;
}

fn Square.Area() -> self {
    return .Width * .Height;
}

// Triangle

class Triangle {
    var Width: f32 = 3;
    var Height: f32 = 3;

    fn Area() -> self;
}

fn Triangle.Area() -> self {
    return (.Width * .Height) / 2;
}

// Hexagon

class Hexagon {
    var Side: f32 = 5;

    fn Area() -> self;
}

fn Hexagon.Area() -> self {
    return ((3 * 1.732) / 2) * .Side ^ 2
}

[jambo-posready-embedded-7]

@btdw Usually when we add support for a language that doesn't have a syntax highlighting grammar (or one released under a permissive license), we sometimes use another language's grammar as a fallback that happens to produce "good enough" highlighting. For example, here's one of your Carbon samples highlighted using Rust:

I've experimented with a couple and found the syntax for V works the best:

package Shapes api;
import Math;

// Circle

class Circle {
    var Radius: f32 = 1;
    const var Diameter: f32 = self.Radius * 2;

    const var Pi: f32 = Math.Pi;

    fn Area() -> self;
    fn Circumference() -> self;
}

fn Circle.Area() -> self {
    return Math.Pi * .Radius ^ 2
}

fn Circle.Circumference() -> self {
    return 2 * Math.Pi * .Radius
}

// Rectangle

class Rectangle {
    var Width: f32 = 3;
    var Height: f32 = 1;

    fn Area() -> self;
}

fn Rectangle.Area() -> self {
    return .Width * .Height;
}

// Square (Note: Provides same functions as "Rectangle" class.)

class Square {
    var Width: f32 = 3;
    var Height: f32 = 1;

    fn Area() -> self;
}

fn Square.Area() -> self {
    return .Width * .Height;
}

// Triangle

class Triangle {
    var Width: f32 = 3;
    var Height: f32 = 3;

    fn Area() -> self;
}

fn Triangle.Area() -> self {
    return (.Width * .Height) / 2;
}

// Hexagon

class Hexagon {
    var Side: f32 = 5;

    fn Area() -> self;
}

fn Hexagon.Area() -> self {
    return ((3 * 1.732) / 2) * .Side ^ 2
}

[jambo-posready-embedded-7]

I've experimented with a couple and found the syntax for V works the best:

9bdc91c adds V syntax highlighting to Carbon files

[jambo-posready-embedded-7]

Thanks for the suggestion, it was committed

[Alhadis]

@btdw You'll need to fix the failed test reported here. It simply involves updating vendor/README.md to include Carbon in the list. Just add this to the file on line 75:

--- expected
+++ actual
@@ -83,6 +83,7 @@
 - **Cairo:** [xshitaka/atom-language-cairo](https://github.com/xshitaka/atom-language-cairo)
 - **CameLIGO:** [pewulfman/Ligo-grammar](https://github.com/pewulfman/Ligo-grammar)
 - **Cap'n Proto:** [textmate/capnproto.tmbundle](https://github.com/textmate/capnproto.tmbundle)
+- **Carbon:** [0x9ef/vscode-vlang](https://github.com/0x9ef/vscode-vlang)

[lildude]

LGTM. Thanks.

Note: this PR will not be merged until close to when the next release is made. See here for more details.