Add Null Coalescing operator

include/CrossLang.hpp

@@ -664,7 +664,8 @@ typedef enum {
     PUSHBREAK,
     PUSHCONTINUE,
     JMPIFBREAK,
-    JMPIFCONTINUE
+    JMPIFCONTINUE,
+    JMPIFDEFINED
 } Instruction;
 /**
  * @brief Base type for bytecode instruction
@@ -1274,6 +1275,10 @@ constexpr std::string_view RelativePathExpression = "relativePathExpression";
  * @brief await expression for async/await
  */
 constexpr std::string_view AwaitExpression = "awaitExpression";
+/**
+ * @brief ?? operator
+ */
+constexpr std::string_view NullCoalescingExpression = "nullCoalescingExpression";
 /**
  * @brief Advanced AST node
  * 
@@ -1346,6 +1351,7 @@ class Parser {
     SyntaxNode ParseFactor();
     SyntaxNode ParseValue();
     SyntaxNode ParseUnary();
+    SyntaxNode ParseNullCoalescing();
     void ParseHtml(std::vector<SyntaxNode>& nodes,std::string var);
     GC* gc;
     TRootEnvironment* env;
@@ -2254,6 +2260,7 @@ class GC {
             bool ExecuteMethod2(GC* gc, TObject instance, std::string key, std::vector<TObject> args);
         protected:
             static void* ThreadCallback(void* ptr);
+            bool JumpIfDefined(GC* gc);
             bool Add(GC* gc);
             bool Sub(GC* gc);
             bool Times(GC* gc);

src/compiler/codegen.cpp

@@ -521,7 +521,18 @@ namespace Tesses::CrossLang
             TWO_EXPR(NotEqualsExpression, NEQ)
             TWO_EXPR(EqualsExpression, EQ)
             TWO_EXPR(XOrExpression, XOR)
-            if(adv.nodeName == ClassStatement && adv.nodes.size() >= 3 && std::holds_alternative<std::string>(adv.nodes[0]))
+            if(adv.nodeName == NullCoalescingExpression && adv.nodes.size() == 2)
+            {
+                uint32_t ifId = NewId();
+                std::string ifIdTrue = "__compGenTrue";
+                ifIdTrue.append(std::to_string(ifId));
+                GenNode(instructions,adv.nodes[0],scope,contscope,brkscope,contI,brkI);
+                instructions.push_back(new JumpStyleInstruction(Instruction::JMPIFDEFINED, ifIdTrue));
+                GenNode(instructions,adv.nodes[1],scope,contscope,brkscope,contI,brkI);
+                instructions.push_back(new LabelInstruction(ifIdTrue));    
+                
+            }
+            else if(adv.nodeName == ClassStatement && adv.nodes.size() >= 3 && std::holds_alternative<std::string>(adv.nodes[0]))
             {
                 CodeGenClass cls;
                 cls.documentation = GetString(std::get<std::string>(adv.nodes[0]));

src/compiler/lexer.cpp

@@ -579,6 +579,7 @@ namespace Tesses::CrossLang
                     break;
                 case '<':
                 case '>':
+                case '?':
                     if(peek == read)
                     {
                         Flush();
@@ -670,7 +671,6 @@ namespace Tesses::CrossLang
                 case ':':
                 case ';':
                 case ',':
-                case '?':
                     Flush();
                     Symbol({read});
                     break;

src/compiler/parser.cpp

@@ -1088,6 +1088,10 @@ namespace Tesses::CrossLang
         {
             return AdvancedSyntaxNode::Create(CompoundAssignExpression,true,{AdvancedSyntaxNode::Create(XOrExpression,true,{ node,ParseAssignment()})});
         }
+        else if(IsSymbol("?\?="))
+        {
+            return AdvancedSyntaxNode::Create(CompoundAssignExpression,true,{AdvancedSyntaxNode::Create(NullCoalescingExpression,true,{ node,ParseAssignment()})});
+        }
         return node;
     }
     SyntaxNode Parser::ParseNode(bool isRoot)
@@ -1547,9 +1551,18 @@ namespace Tesses::CrossLang
         EnsureSymbol(";");
         return v;
     }
+    SyntaxNode Parser::ParseNullCoalescing()
+    {
+        SyntaxNode expr = ParseLOr();
+        while(IsSymbol("?\?"))
+        {
+            expr = AdvancedSyntaxNode::Create(NullCoalescingExpression,true,{expr,ParseLOr()});
+        }
+        return expr;
+    }
     SyntaxNode Parser::ParseTernary()
     {
-        SyntaxNode node = ParseLOr();
+        SyntaxNode node = ParseNullCoalescing();
         if(IsSymbol("?"))
         {
             auto yes = ParseTernary();

src/vm/vm.cpp

@@ -6163,6 +6163,32 @@ namespace Tesses::CrossLang {
         }
         return false;
     }
+    bool InterperterThread::JumpIfDefined(GC* gc)
+    {
+        
+        std::vector<CallStackEntry*>& cse=this->call_stack_entries;
+        auto stk = cse.back();
+
+        if(stk->ip + 4 <= stk->callable->closure->code.size())
+        {
+            uint32_t n=BitConverter::ToUint32BE(stk->callable->closure->code[stk->ip]);
+                            
+            GCList ls(gc);
+            auto _res2 = stk->Pop(ls);
+                                
+            stk->ip = stk->ip + 4;
+            if(!std::holds_alternative<Undefined>(_res2) && !std::holds_alternative<std::nullptr_t>(_res2))
+            {
+                stk->ip = n;
+                stk->Push(gc,_res2);
+            }
+                            
+                            
+        }
+        else
+            throw VMException("Can't read jmpifdefined pc.");
+        return false;
+    }
     bool InterperterThread::JumpIfBreak(GC* gc)
     {