private void ParseDeclaration(IAbstractSyntaxTree lexerNode)
        {
            var declaration = DeclarationInfo.Parse(Parser, lexerNode);

            if (declaration.Initializer != null && declaration.Initializer.IsFunctionDeclaration() && !declaration.Modifiers.HasFlag(Modifiers.Mutable))
            {
                //method
                var method = FunctionDeclarationNode.ParseAsMethod(this, declaration);
                declaredMethods.Add(method);
            }
            else
            {
                //field
                var field = new FieldDeclarationNode(this, declaration, Parser.GetSequencePoint(lexerNode));
                fields.Add(field);
            }
        }