MQLArticles/MqlCompilerBugs/TemplateInNamespace/Repro.mq5

//+------------------------------------------------------------------+
//|                                                        Repro.mq5 |
//|                                   Copyright 2026, Niquel Mendoza |
//|                                             https://www.mql5.com |
//+------------------------------------------------------------------+
#property copyright "Copyright 2026, Niquel Mendoza"
#property link      "https://www.mql5.com"
#property version   "1.00"
#property strict

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
namespace TSN
{
//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class CFernet
 {
private:
  uchar              hmac[16];
  uchar              aes[16];

public:
                     CFernet(void) {}
                    ~CFernet(void) {}

  //---
  void               PrintData();
  template <typename TCryptoRandomFunc>
  void               AutoKey();
 };

template <typename TCryptoRandomFunc>
void CFernet::AutoKey()  // 'CFernet' - struct undefined	Repro.mq5	36	6
 {
  uchar key[32];
  TCryptoRandomFunc::Fill(key, 32, 0);
  ArrayCopy(hmac, key, 0, 0, 16);
  ArrayCopy(aes, key, 0, 16, 16);
 }

void CFernet::PrintData(void)
 {
  ArrayPrint(hmac, 1, "|");
  ArrayPrint(aes, 1, "|");
 }
}

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
class CFiller
 {
public:
                     CFiller(void) {}
                    ~CFiller(void) {}

  static void        Fill(uchar& out[], int oult, int o_s = 0)
   {
    ArrayFill(out, o_s, oult, 0);
   }
 };

//+------------------------------------------------------------------+
//|                                                                  |
//+------------------------------------------------------------------+
void OnStart(void)
 {
  TSN::CFernet fernet;
  fernet.AutoKey<CFiller>(); // 
  fernet.PrintData();
 }
//+------------------------------------------------------------------+