Allow tuple affectations

``
R x=0;
R y=3;
(x,y) += (3,2);
``

src/language/ASTSymbolInitializationChecker.cpp

@@ -8,7 +8,7 @@ void
 ASTSymbolInitializationChecker::_checkSymbolInitialization(ASTNode& node)
 {
   if (node.is_type<language::declaration>()) {
-    auto set_is_initialized = [&](ASTNode& name_node) {
+    auto check_if_initialized = [&](ASTNode& name_node) {
       const std::string& symbol = name_node.string();
       auto [i_symbol, found]    = node.m_symbol_table->find(symbol, name_node.begin());
       Assert(found, "unexpected error, should have been detected through declaration checking");
@@ -19,11 +19,11 @@ ASTSymbolInitializationChecker::_checkSymbolInitialization(ASTNode& node)
     };
 
     if (node.children[1]->is_type<language::name>()) {
-      set_is_initialized(*node.children[1]);
+      check_if_initialized(*node.children[1]);
     } else if (node.children[1]->is_type<language::name_list>()) {
       ASTNode& name_list_node = *node.children[1];
       for (auto& child_node : name_list_node.children) {
-        set_is_initialized(*child_node);
+        check_if_initialized(*child_node);
       }
     }
   } else if (node.is_type<language::let_declaration>()) {
@@ -44,11 +44,22 @@ ASTSymbolInitializationChecker::_checkSymbolInitialization(ASTNode& node)
   } else if (node.is_type<language::eq_op>()) {
     // first checks for right hand side
     this->_checkSymbolInitialization(*node.children[1]);
-    // then marks left hand side as initialized
-    const std::string& symbol = node.children[0]->string();
-    auto [i_symbol, found]    = node.m_symbol_table->find(symbol, node.children[0]->begin());
+
+    auto set_is_initialized = [&](ASTNode& name_node) {
+      const std::string& symbol = name_node.string();
+      auto [i_symbol, found]    = node.m_symbol_table->find(symbol, name_node.begin());
       Assert(found, "unexpected error, should have been detected through declaration checking");
       i_symbol->attributes().setIsInitialized();
+    };
+
+    if (node.children[0]->is_type<language::name>()) {
+      set_is_initialized(*node.children[0]);
+    } else if (node.children[0]->is_type<language::name_list>()) {
+      ASTNode& name_list_node = *node.children[0];
+      for (auto& child_node : name_list_node.children) {
+        set_is_initialized(*child_node);
+      }
+    }
   } else if (node.is_type<language::name>()) {
     auto [i_symbol, found] = node.m_symbol_table->find(node.string(), node.begin());
     Assert(found, "unexpected error, should have been detected through declaration checking");

src/language/PEGGrammar.hpp

@@ -211,9 +211,10 @@ struct expression_list : seq< open_parent, expression, plus< if_must< COMMA, exp
 
 struct affect_op : sor< eq_op, multiplyeq_op, divideeq_op, pluseq_op, minuseq_op > {};
 
-struct affectation : seq< NAME , if_must< affect_op,  sor< expression_list, expression > > >{};
-
 struct name_list;
+
+struct affectation : seq< sor< NAME, name_list >, if_must< affect_op,  sor< expression_list, expression > > >{};
+
 struct declaration : if_must< type_expression, sor< NAME, name_list>, opt< if_must< seq< one< '=' >, ignored >, sor< expression_list, expression > > > >{};
 
 struct type_mapping : seq< type_expression, RIGHT_ARROW, type_expression >{};