message: Preserve parent relation in case statements
diff: @@ -432,7 +432,7 @@ UHDM::atomic_stmt* CompileHelper::compileCaseStmt(PortNetHolder* component, File
  case_stmt->Case_items(case_items);
  result = case_stmt;
  case_stmt->VpiCondition((UHDM::expr*) cond_exp);
  - if (cond_exp)
  + if (cond_exp && !cond_exp->VpiParent())
  cond_exp->VpiParent(case_stmt);
  VObjectType CaseType = fC->Type(Case_type);
  switch (CaseType) {
  @@ -486,7 +486,7 @@ UHDM::atomic_stmt* CompileHelper::compileCaseStmt(PortNetHolder* component, File
  if (fC->Type(Expression) == VObjectType::slExpression) {
  // Expr
  UHDM::any* item_exp = compileExpression(component, fC, Expression, compileDesign);
  - if (item_exp) {
  + if (item_exp && !item_exp->VpiParent()) {
  item_exp->VpiParent(case_item);
  exprs->push_back(item_exp);
  } else {
  @@ -515,7 +515,7 @@ UHDM::atomic_stmt* CompileHelper::compileCaseStmt(PortNetHolder* component, File
  while (Value_range) {
  UHDM::expr* item_exp = (expr*)compileExpression(
  component, fC, Value_range, compileDesign);
  - if (item_exp) {
  + if (item_exp && !item_exp->VpiParent()) {
  item_exp->VpiParent(case_item);
  exprs->push_back(item_exp);
  }
  