feat: error handling, better prelude, double linked lists usage etc

include/parser/lexer.hpp

@@ -92,11 +92,11 @@ public:
 public:
     bool NextToken()
     {
-        if (m_pos >= m_code.size || m_code.data[m_pos] == '\0')
-        {
-            m_token = Token(TokenType::Eof);
-            return false;
-        }
+        // if (m_pos >= m_code.len())
+        // {
+        //     m_token = Token(TokenType::Eof);
+        //     return false;
+        // }
 
         char c = m_code.data[m_pos++];
 
@@ -109,6 +109,12 @@ public:
             c = m_code.data[m_pos++];
         }
 
+        if (m_pos >= m_code.len())
+        {
+            m_token = Token(TokenType::Eof);
+            return false;
+        }
+
         if (std::isalpha(c) != 0 || c == '_')
         {
             StringBuilder s;