Parse tilde as missing output parameter marker

Parser.Tests/MParserShould.cs

@@ -387,5 +387,18 @@ namespace Parser.Tests
             Assert.IsInstanceOf<BinaryOperationExpressionNode>(f.Body);
             Assert.AreEqual(text, actual.FullText);            
         }
+
+        [Test]
+        public void ParseTildeAsResultReplacement()
+        {
+            var text = "[a, ~, b]";
+            var sut = CreateParser(text);
+            var actual = sut.ParseExpression();
+            Assert.IsInstanceOf<ArrayLiteralExpressionNode>(actual);
+            var f = (ArrayLiteralExpressionNode) actual;
+            Assert.AreEqual(3, f.Elements.Elements.Count);
+            Assert.IsInstanceOf<UnaryPrefixOperationExpressionNode>(f.Elements.Elements[1]);
+            Assert.AreEqual(text, actual.FullText);
+        }
     }
 }

Parser/MParser.cs

@@ -598,6 +598,17 @@ namespace Parser
                 var unaryTokenKind = ConvertToUnaryTokenKind(operation.Kind);
                 var newPrecedence = GetPrecedence(unaryTokenKind);
                 var operand = ParseSubExpression(options, newPrecedence);
+                if (operand == null)
+                {
+                    if (options.ParsingArrayElements && operation.Kind == TokenKind.Not)
+                    {
+                        operand = Factory.EmptyExpression();
+                    }
+                    else
+                    {
+                        throw new ParsingException($"Unexpected token {CurrentToken.Kind} at {operation.PureToken.Position}.");
+                    }
+                }
                 lhs = Factory.UnaryPrefixOperationExpression(Factory.Token(operation), operand);
             }
             else if (CurrentToken.Kind == TokenKind.At)

Parser/SyntaxNode.cs

@@ -449,6 +449,7 @@ namespace Parser
             get { yield break; }
         }
 
+        public override string FullText => "";
     }
 
     public class CompoundNameNode : ExpressionNode