Clear STL module and network state on entering new

Sets the typecheck to the correct state for verifying new blocks or
networks.

Limitations: The accumulator is unaffected by this. It needs to be
investigated whether the accumulator gets reset at all in TIA.

Author: MatWise

src/statement-list/statement_list_typecheck.cpp

@@ -343,12 +343,12 @@ void statement_list_typecheckt::typecheck_statement_list_networks(
   if(tia_symbol.value.is_nil())
     tia_symbol.value = code_blockt{};
 
+  clear_module_state();
   typecheck_temp_var_decls(tia_module, tia_symbol);
 
   for(const auto &network : tia_module.networks)
   {
-    // Set RLO to true each time a new network is entered (TIA behaviour).
-    rlo_bit = true_exprt();
+    clear_network_state();
     for(const auto &instruction : network.instructions)
       typecheck_statement_list_instruction(instruction, tia_symbol);
   }
@@ -1804,6 +1804,21 @@ void statement_list_typecheckt::initialize_bit_expression(const exprt &op)
   rlo_bit = op;
 }
 
+void statement_list_typecheckt::clear_network_state()
+{
+  rlo_bit = true_exprt{};
+  fc_bit = false;
+  or_bit = false;
+  nesting_stack.clear();
+}
+
+void statement_list_typecheckt::clear_module_state()
+{
+  clear_network_state();
+  label_references.clear();
+  stl_labels.clear();
+}
+
 void statement_list_typecheckt::save_rlo_state(symbolt &tia_element)
 {
   symbol_exprt temp_rlo{

src/statement-list/statement_list_typecheck.h

@@ -756,6 +756,16 @@ class statement_list_typecheckt : public typecheckt
   /// \param op: Operand of the encountered instruction.
   void initialize_bit_expression(const exprt &op);
 
+  /// Modifies the state of the typecheck to resemble the beginning of a new
+  /// module. All changes to the implicit typecheck fields are close to the
+  /// original TIA behaviour.
+  void clear_module_state();
+
+  /// Modifies the state of the typecheck to resemble the beginning of a new
+  /// network. All changes to the implicit typecheck fields are close to the
+  /// original TIA behaviour.
+  void clear_network_state();
+
   /// Saves the current RLO bit to a temporary variable to prevent false
   /// overrides when modifying boolean variables.
   /// \param tia_element: Symbol representation of the TIA element.