Fixed SD2-457: C# lexer crash on "0x"

git-svn-id: svn://svn.sharpdevelop.net/sharpdevelop/trunk@518 1ccf3a8d-04fe-1044-b7c0-cef0b8235c61

src/Libraries/NRefactory/Project/Src/Lexer/CSharp/Lexer.cs

@@ -162,6 +162,10 @@ namespace ICSharpCode.NRefactory.Parser.CSharp
 					while (IsHex((char)ReaderPeek())) {
 						sb.Append(Char.ToUpper((char)ReaderRead(), CultureInfo.InvariantCulture));
 					}
+					if (sb.Length == 0) {
+						sb.Append('0'); // dummy value to prevent exception
+						errors.Error(y, x, "Invalid hexadecimal integer literal");
+					}
 					ishex = true;
 					prefix = "0x";
 					peek = (char)ReaderPeek();

src/Libraries/NRefactory/Test/Lexer/CSharp/NumberLexerTest.cs

@@ -70,6 +70,16 @@ namespace ICSharpCode.NRefactory.Tests.Lexer.CSharp
 			CheckToken("0xAB1f", 0xAB1f);
 		}
 		
+		[Test]
+		public void InvalidHexadecimalInteger()
+		{
+			// don't check result, just make sure there is no exception
+			GenerateLexer(new StringReader("0x2GF")).NextToken();
+			GenerateLexer(new StringReader("0xG2F")).NextToken();
+			// SD2-457
+			GenerateLexer(new StringReader("0x")).NextToken();
+		}
+		
 		[Test]
 		public void TestLongHexadecimalInteger()
 		{