Add support for more declarations and access modifiers in Carbon lexer (

#2366)

pygments/lexers/carbon.py

@@ -41,12 +41,13 @@ class CarbonLexer(RegexLexer):
             # Declaration
             (r'(package|import|api|namespace|library)\b', Keyword.Namespace),
             (r'(abstract|alias|fn|class|interface|let|var|virtual|external|'
-             r'base|addr|extends)\b', Keyword.Declaration),
+             r'base|addr|extends|choice)\b', Keyword.Declaration),
             # Keywords
             (words(('as', 'or', 'not', 'and', 'break', 'continue', 'case',
                     'default', 'if', 'else', 'destructor', 'for', 'forall',
-                    'while', 'where', 'then', 'in', 'is', 'return',
-                    'returned'), suffix=r'\b'), Keyword),
+                    'while', 'where', 'then', 'in', 'is', 'return', 'returned',
+                    'friend', 'partial', 'private', 'protected', 'observe',
+                    'override', 'Self'), suffix=r'\b'), Keyword),
             (r'(self)\b', Keyword.Pseudo),
             (r'(true|false)\b', Keyword.Constant),
             (r'(auto|bool|string|i8|i16|i32|i64|u8|u16|u32|u64|'

tests/examplefiles/carbon/declarations.carbon

@@ -0,0 +1,30 @@
+package ExplorerTest api;
+
+choice MyOptionalElement(ZZ:! type, YY:! type) {
+  None(YY),
+  Element(ZZ)
+}
+
+abstract class C {
+  var a: i32;
+}
+
+base class B {
+  var value_b: i32;
+}
+
+interface Vector {
+  fn Zero() -> Self;
+  fn Add[self: Self](b: Self) -> Self;
+  fn Scale[self: Self](v: i32) -> Self;
+}
+
+class Pal {
+  private var x: i32;
+  protected var y: i32;
+  friend Buddy;
+}
+
+abstract class MyAbstractClass {
+  protected fn Create() -> partial Self { }
+}