Add Lexer and Parser support for the switch expression

mavasani · Apr 28, 2017 · 2414444 · 2414444
1 parent 4b50f66
commit 2414444
Show file tree

Hide file tree

Showing 3 changed files with 16 additions and 0 deletions.
diff --git a/src/Compilers/CSharp/Portable/Parser/LanguageParser.cs b/src/Compilers/CSharp/Portable/Parser/LanguageParser.cs
@@ -9423,6 +9423,14 @@ private ExpressionSyntax ParseSubExpressionCore(Precedence precedence)
                 var colonRight = this.ParseExpressionCore();
                 leftOperand = _syntaxFactory.ConditionalExpression(leftOperand, questionToken, colonLeft, colon, colonRight);
             }
+            else if (tk == SyntaxKind.QuestionColonToken && precedence <= Precedence.Ternary)
+            {
+                var questionColonToken = this.EatToken();
+                var labels = this.ParseBracketedArgumentList();
+                var colon = this.EatToken(SyntaxKind.ColonToken);
+                var values = this.ParseBracketedArgumentList();
+                leftOperand = _syntaxFactory.SwitchExpression(leftOperand, questionColonToken, labels, colon, values);
+            }
 
             return leftOperand;
         }
@@ -10541,6 +10549,7 @@ private static bool CanFollowCast(SyntaxKind kind)
                 case SyntaxKind.MinusGreaterThanToken:
                 case SyntaxKind.QuestionQuestionToken:
                 case SyntaxKind.EndOfFileToken:
+                case SyntaxKind.QuestionColonToken:
                     return false;
                 default:
                     return true;

diff --git a/src/Compilers/CSharp/Portable/Parser/Lexer.cs b/src/Compilers/CSharp/Portable/Parser/Lexer.cs
@@ -562,6 +562,11 @@ private void ScanSyntaxToken(ref TokenInfo info)
                         TextWindow.AdvanceChar();
                         info.Kind = SyntaxKind.QuestionQuestionToken;
                     }
+                    else if (TextWindow.PeekChar() == ':')
+                    {
+                        TextWindow.AdvanceChar();
+                        info.Kind = SyntaxKind.QuestionColonToken;
+                    }
                     else
                     {
                         info.Kind = SyntaxKind.QuestionToken;

diff --git a/src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs b/src/Compilers/CSharp/Portable/Syntax/SyntaxKindFacts.cs
@@ -1275,6 +1275,8 @@ public static string GetText(SyntaxKind kind)
                     return "<?";
                 case SyntaxKind.XmlProcessingInstructionEndToken:
                     return "?>";
+                case SyntaxKind.QuestionColonToken:
+                    return "?:";
 
                 // compound
                 case SyntaxKind.BarBarToken: