protected boolean checkNotNullable(
     DfaMemoryState state, DfaValue value, NullabilityProblem problem, PsiElement anchor) {
   boolean notNullable = state.checkNotNullable(value);
   if (notNullable
       && problem != NullabilityProblem.passingNullableArgumentToNonAnnotatedParameter) {
     DfaValueFactory factory = ((DfaMemoryStateImpl) state).getFactory();
     state.applyCondition(
         factory
             .getRelationFactory()
             .createRelation(value, factory.getConstFactory().getNull(), NE, false));
   }
   return notNullable;
 }
 private DfaValue getDfaContractReturnValue(
     MethodContract contract, MethodCallInstruction instruction, DfaValueFactory factory) {
   switch (contract.returnValue) {
     case NULL_VALUE:
       return factory.getConstFactory().getNull();
     case NOT_NULL_VALUE:
       return factory.createTypeValue(instruction.getResultType(), Nullness.NOT_NULL);
     case TRUE_VALUE:
       return factory.getConstFactory().getTrue();
     case FALSE_VALUE:
       return factory.getConstFactory().getFalse();
     case THROW_EXCEPTION:
       return factory.getConstFactory().getContractFail();
     default:
       return getMethodResultValue(instruction, null, factory);
   }
 }
  @Nullable
  private DfaInstructionState[] handleRelationBinop(
      BinopInstruction instruction,
      DataFlowRunner runner,
      DfaMemoryState memState,
      DfaValue dfaRight,
      DfaValue dfaLeft) {
    DfaValueFactory factory = runner.getFactory();
    final Instruction next = runner.getInstruction(instruction.getIndex() + 1);
    DfaRelationValue dfaRelation =
        factory
            .getRelationFactory()
            .createRelation(dfaLeft, dfaRight, instruction.getOperationSign(), false);
    if (dfaRelation == null) {
      return null;
    }

    myCanBeNullInInstanceof.add(instruction);

    ArrayList<DfaInstructionState> states = new ArrayList<DfaInstructionState>();

    final DfaMemoryState trueCopy = memState.createCopy();
    if (trueCopy.applyCondition(dfaRelation)) {
      trueCopy.push(factory.getConstFactory().getTrue());
      instruction.setTrueReachable();
      states.add(new DfaInstructionState(next, trueCopy));
    }

    //noinspection UnnecessaryLocalVariable
    DfaMemoryState falseCopy = memState;
    if (falseCopy.applyCondition(dfaRelation.createNegated())) {
      falseCopy.push(factory.getConstFactory().getFalse());
      instruction.setFalseReachable();
      states.add(new DfaInstructionState(next, falseCopy));
      if (instruction instanceof InstanceofInstruction && !falseCopy.isNull(dfaLeft)) {
        myUsefulInstanceofs.add((InstanceofInstruction) instruction);
      }
    }

    return states.toArray(new DfaInstructionState[states.size()]);
  }
  @Override
  public DfaInstructionState[] visitTypeCast(
      TypeCastInstruction instruction, DataFlowRunner runner, DfaMemoryState memState) {
    final DfaValueFactory factory = runner.getFactory();
    DfaValue dfaExpr = factory.createValue(instruction.getCasted());
    if (dfaExpr != null) {
      DfaTypeValue dfaType =
          (DfaTypeValue) factory.createTypeValue(instruction.getCastTo(), Nullness.UNKNOWN);
      DfaRelationValue dfaInstanceof =
          factory.getRelationFactory().createRelation(dfaExpr, dfaType, INSTANCEOF_KEYWORD, false);
      if (dfaInstanceof != null && !memState.applyInstanceofOrNull(dfaInstanceof)) {
        onInstructionProducesCCE(instruction);
      }
    }

    if (instruction.getCastTo() instanceof PsiPrimitiveType) {
      memState.push(runner.getFactory().getBoxedFactory().createUnboxed(memState.pop()));
    }

    return nextInstruction(instruction, runner, memState);
  }
  @Override
  public DfaInstructionState[] visitAssign(
      AssignInstruction instruction, DataFlowRunner runner, DfaMemoryState memState) {
    DfaValue dfaSource = memState.pop();
    DfaValue dfaDest = memState.pop();

    if (dfaDest instanceof DfaVariableValue) {
      DfaVariableValue var = (DfaVariableValue) dfaDest;

      DfaValueFactory factory = runner.getFactory();
      if (dfaSource instanceof DfaVariableValue
          && factory.getVarFactory().getAllQualifiedBy(var).contains(dfaSource)) {
        Nullness nullability =
            memState.isNotNull(dfaSource)
                ? Nullness.NOT_NULL
                : ((DfaVariableValue) dfaSource).getInherentNullability();
        dfaSource =
            factory.createTypeValue(((DfaVariableValue) dfaSource).getVariableType(), nullability);
      }

      if (var.getInherentNullability() == Nullness.NOT_NULL) {
        checkNotNullable(
            memState,
            dfaSource,
            NullabilityProblem.assigningToNotNull,
            instruction.getRExpression());
      }
      final PsiModifierListOwner psi = var.getPsiVariable();
      if (!(psi instanceof PsiField) || !psi.hasModifierProperty(PsiModifier.VOLATILE)) {
        memState.setVarValue(var, dfaSource);
      }
    } else if (dfaDest instanceof DfaTypeValue && ((DfaTypeValue) dfaDest).isNotNull()) {
      checkNotNullable(
          memState, dfaSource, NullabilityProblem.assigningToNotNull, instruction.getRExpression());
    }

    memState.push(dfaDest);

    return nextInstruction(instruction, runner, memState);
  }
  @NotNull
  private DfaValue getMethodResultValue(
      MethodCallInstruction instruction,
      @Nullable DfaValue qualifierValue,
      DfaValueFactory factory) {
    DfaValue precalculated = instruction.getPrecalculatedReturnValue();
    if (precalculated != null) {
      return precalculated;
    }

    final PsiType type = instruction.getResultType();
    final MethodCallInstruction.MethodType methodType = instruction.getMethodType();

    if (methodType == MethodCallInstruction.MethodType.UNBOXING) {
      return factory.getBoxedFactory().createUnboxed(qualifierValue);
    }

    if (methodType == MethodCallInstruction.MethodType.BOXING) {
      DfaValue boxed = factory.getBoxedFactory().createBoxed(qualifierValue);
      return boxed == null ? factory.createTypeValue(type, Nullness.NOT_NULL) : boxed;
    }

    if (methodType == MethodCallInstruction.MethodType.CAST) {
      assert qualifierValue != null;
      if (qualifierValue instanceof DfaConstValue) {
        Object casted =
            TypeConversionUtil.computeCastTo(((DfaConstValue) qualifierValue).getValue(), type);
        return factory
            .getConstFactory()
            .createFromValue(casted, type, ((DfaConstValue) qualifierValue).getConstant());
      }
      return qualifierValue;
    }

    if (type != null && (type instanceof PsiClassType || type.getArrayDimensions() > 0)) {
      Nullness nullability = myReturnTypeNullability.get(instruction);
      if (nullability == Nullness.UNKNOWN && factory.isUnknownMembersAreNullable()) {
        nullability = Nullness.NULLABLE;
      }
      return factory.createTypeValue(type, nullability);
    }
    return DfaUnknownValue.getInstance();
  }
  private List<DfaMemoryState> addContractResults(
      DfaValue[] argValues,
      MethodContract contract,
      List<DfaMemoryState> states,
      MethodCallInstruction instruction,
      DfaValueFactory factory,
      Set<DfaMemoryState> finalStates) {
    DfaConstValue.Factory constFactory = factory.getConstFactory();
    List<DfaMemoryState> falseStates = ContainerUtil.newArrayList();
    for (int i = 0; i < argValues.length; i++) {
      DfaValue argValue = argValues[i];
      MethodContract.ValueConstraint constraint = contract.arguments[i];
      DfaConstValue expectedValue = constraint.getComparisonValue(factory);
      if (expectedValue == null) continue;

      boolean invertCondition = constraint.shouldUseNonEqComparison();
      DfaValue condition =
          factory
              .getRelationFactory()
              .createRelation(argValue, expectedValue, EQEQ, invertCondition);
      if (condition == null) {
        if (!(argValue instanceof DfaConstValue)) {
          for (DfaMemoryState state : states) {
            falseStates.add(state.createCopy());
          }
          continue;
        }
        condition =
            constFactory.createFromValue(
                (argValue == expectedValue) != invertCondition, PsiType.BOOLEAN, null);
      }

      List<DfaMemoryState> nextStates = ContainerUtil.newArrayList();
      for (DfaMemoryState state : states) {
        boolean unknownVsNull =
            expectedValue == constFactory.getNull()
                && argValue instanceof DfaVariableValue
                && ((DfaMemoryStateImpl) state)
                        .getVariableState((DfaVariableValue) argValue)
                        .getNullability()
                    == Nullness.UNKNOWN;
        DfaMemoryState falseCopy = state.createCopy();
        if (state.applyCondition(condition)) {
          if (unknownVsNull && !invertCondition) {
            state.markEphemeral();
          }
          nextStates.add(state);
        }
        if (falseCopy.applyCondition(condition.createNegated())) {
          if (unknownVsNull && invertCondition) {
            falseCopy.markEphemeral();
          }
          falseStates.add(falseCopy);
        }
      }
      states = nextStates;
    }

    for (DfaMemoryState state : states) {
      state.push(getDfaContractReturnValue(contract, instruction, factory));
      finalStates.add(state);
    }

    return falseStates;
  }