private static boolean removeReturnCheck()

in src/org/jetbrains/java/decompiler/modules/decompiler/IdeaNotNullHelper.java [208:346]
104 lines of code
44 McCabe index (conditional complexity)

  private static boolean removeReturnCheck(Statement stat, StructMethod mt) {

    Statement parent = stat.getParent();

    if (parent != null && parent.type == StatementType.IF && stat.type == StatementType.BASIC_BLOCK && stat.getExprents().size() == 1) {
      Exprent exprent = stat.getExprents().get(0);
      if (exprent.type == Exprent.EXPRENT_EXIT) {
        ExitExprent exit_exprent = (ExitExprent)exprent;
        if (exit_exprent.getExitType() == ExitExprent.EXIT_RETURN) {
          Exprent exprent_value = exit_exprent.getValue();
          //if(exprent_value.type == Exprent.EXPRENT_VAR) {
          //	VarExprent var_value = (VarExprent)exprent_value;

          IfStatement ifparent = (IfStatement)parent;
          Exprent if_condition = ifparent.getHeadexprent().getCondition();

          if (ifparent.getElsestat() == stat && if_condition.type == Exprent.EXPRENT_FUNCTION &&
              ((FunctionExprent)if_condition).getFuncType() == FunctionExprent.FUNCTION_EQ) { // TODO: reversed order possible (in theory)

            FunctionExprent func = (FunctionExprent)if_condition;
            Exprent first_param = func.getLstOperands().get(0);
            Exprent second_param = func.getLstOperands().get(1);

            StatEdge ifedge = ifparent.getIfEdge();
            StatEdge elseedge = ifparent.getElseEdge();

            Statement ifbranch = ifparent.getIfstat();
            Statement elsebranch = ifparent.getElsestat();

            if (second_param.type == Exprent.EXPRENT_CONST &&
                second_param.getExprType().getType() == CodeConstants.TYPE_NULL) { // TODO: reversed parameter order
              //if(first_param.type == Exprent.EXPRENT_VAR && ((VarExprent)first_param).getIndex() == var_value.getIndex()) {
              if (first_param.equals(exprent_value)) {        // TODO: check for absence of side effects like method invocations etc.
                if (ifbranch.type == StatementType.BASIC_BLOCK &&
                    ifbranch.getExprents().size() == 1 &&
                    // TODO: special check for IllegalStateException
                    ifbranch.getExprents().get(0).type == Exprent.EXPRENT_EXIT) {

                  ifparent.getFirst().removeSuccessor(ifedge);
                  ifparent.getFirst().removeSuccessor(elseedge);

                  ifparent.getStats().removeWithKey(ifbranch.id);
                  ifparent.getStats().removeWithKey(elsebranch.id);

                  if (!ifbranch.getAllSuccessorEdges().isEmpty()) {
                    ifbranch.removeSuccessor(ifbranch.getAllSuccessorEdges().get(0));
                  }

                  if (!ifparent.getFirst().getExprents().isEmpty()) {
                    elsebranch.getExprents().addAll(0, ifparent.getFirst().getExprents());
                  }

                  ifparent.getParent().replaceStatement(ifparent, elsebranch);
                  ifparent.getParent().setAllParent();

                  return true;
                }
              }
            }
          }
        }
      }
    }
    else if (parent != null &&
             parent.type == StatementType.SEQUENCE &&
             stat.type == StatementType.BASIC_BLOCK &&
             stat.getExprents() !=null &&
             stat.getExprents().size() == 1) {
      Exprent exprent = stat.getExprents().get(0);
      if (exprent.type == Exprent.EXPRENT_EXIT) {
        ExitExprent exit_exprent = (ExitExprent)exprent;
        if (exit_exprent.getExitType() == ExitExprent.EXIT_RETURN) {
          Exprent exprent_value = exit_exprent.getValue();

          SequenceStatement sequence = (SequenceStatement)parent;
          int sequence_stats_number = sequence.getStats().size();

          if (sequence_stats_number > 1 &&
              sequence.getStats().getLast() == stat &&
              sequence.getStats().get(sequence_stats_number - 2).type == StatementType.IF) {

            IfStatement ifstat = (IfStatement)sequence.getStats().get(sequence_stats_number - 2);
            Exprent if_condition = ifstat.getHeadexprent().getCondition();

            if (ifstat.iftype == IfStatement.IFTYPE_IF && if_condition.type == Exprent.EXPRENT_FUNCTION &&
                ((FunctionExprent)if_condition).getFuncType() == FunctionExprent.FUNCTION_EQ) { // TODO: reversed order possible (in theory)

              FunctionExprent func = (FunctionExprent)if_condition;
              Exprent first_param = func.getLstOperands().get(0);
              Exprent second_param = func.getLstOperands().get(1);

              Statement ifbranch = ifstat.getIfstat();

              if (second_param.type == Exprent.EXPRENT_CONST &&
                  second_param.getExprType().getType() == CodeConstants.TYPE_NULL) { // TODO: reversed parameter order
                if (first_param.equals(exprent_value)) {        // TODO: check for absence of side effects like method invocations etc.
                  if (ifbranch.type == StatementType.BASIC_BLOCK &&
                      ifbranch.getExprents().size() == 1 &&
                      // TODO: special check for IllegalStateException
                      (ifbranch.getExprents().get(0).type == Exprent.EXPRENT_EXIT  ||
                       (ifbranch.getExprents().get(0) instanceof InvocationExprent invocationExprent &&
                        invocationExprent.getName() != null &&
                        invocationExprent.getName().startsWith(REPORT_NOT_NULL)))) {

                    ifstat.removeSuccessor(ifstat.getAllSuccessorEdges().get(0)); // remove 'else' edge

                    if (!ifstat.getFirst().getExprents().isEmpty()) {
                      stat.getExprents().addAll(0, ifstat.getFirst().getExprents());
                    }

                    for (StatEdge edge : ifstat.getAllPredecessorEdges()) {

                      ifstat.removePredecessor(edge);
                      edge.getSource().changeEdgeNode(EdgeDirection.FORWARD, edge, stat);
                      stat.addPredecessor(edge);
                    }

                    sequence.getStats().removeWithKey(ifstat.id);
                    sequence.setFirst(sequence.getStats().get(0));

                    return true;
                  }
                }
              }
            }
          }
        }
      }
    }


    for (Statement st : stat.getStats()) {
      if (removeReturnCheck(st, mt)) {
        return true;
      }
    }

    return false;
  }