made multi(..) path formulas pass the fragment check

src/storm/logic/FragmentChecker.cpp

@@ -202,7 +202,7 @@ namespace storm {
             bool result = inherited.getSpecification().areProbabilityOperatorsAllowed();
             result = result && (!f.hasQualitativeResult() || inherited.getSpecification().areQualitativeOperatorResultsAllowed());
             result = result && (!f.hasQuantitativeResult() || inherited.getSpecification().areQuantitativeOperatorResultsAllowed());
-            result = result && (f.getSubformula().isProbabilityPathFormula() || f.getSubformula().isConditionalProbabilityFormula());
+            result = result && (f.getSubformula().isProbabilityPathFormula() || f.getSubformula().isConditionalProbabilityFormula() || f.getSubformula().isMultiObjectiveFormula());
             if (!inherited.getSpecification().areNestedOperatorsAllowed()) {
                 result = result && boost::any_cast<bool>(f.getSubformula().accept(*this, InheritedInformation(inherited.getSpecification().copy().setOperatorsAllowed(false))));
             } else {

src/storm/logic/FragmentSpecification.cpp

@@ -89,7 +89,8 @@ namespace storm {
             
             multiObjective.setMultiObjectiveFormulasAllowed(true);
             multiObjective.setMultiObjectiveFormulaAtTopLevelRequired(true);
-            multiObjective.setOperatorsAtTopLevelOfMultiObjectiveFormulasRequired(true);
+            multiObjective.setNestedMultiObjectiveFormulasAllowed(true);
+            multiObjective.setOperatorsAtTopLevelOfMultiObjectiveFormulasRequired(false);
             multiObjective.setProbabilityOperatorsAllowed(true);
             multiObjective.setUntilFormulasAllowed(true);
             multiObjective.setGloballyFormulasAllowed(true);

src/storm/parser/FormulaParserGrammar.cpp

@@ -113,7 +113,7 @@ namespace storm {
             orStateFormula = andStateFormula[qi::_val = qi::_1] >> *(qi::lit("|") >> andStateFormula)[qi::_val = phoenix::bind(&FormulaParserGrammar::createBinaryBooleanStateFormula, phoenix::ref(*this), qi::_val, qi::_1, storm::logic::BinaryBooleanStateFormula::OperatorType::Or)];
             orStateFormula.name("or state formula");
             
-            multiObjectiveFormula = (qi::lit("multi") > qi::lit("(") >> (stateFormula  % qi::lit(",")) >> qi::lit(")"))[qi::_val = phoenix::bind(&FormulaParserGrammar::createMultiObjectiveFormula, phoenix::ref(*this), qi::_1)];
+            multiObjectiveFormula = (qi::lit("multi") > qi::lit("(") >> ((pathFormula(storm::logic::FormulaContext::Probability) | stateFormula) % qi::lit(",")) >> qi::lit(")"))[qi::_val = phoenix::bind(&FormulaParserGrammar::createMultiObjectiveFormula, phoenix::ref(*this), qi::_1)];
             multiObjectiveFormula.name("Multi-objective formula");
             
             stateFormula = (orStateFormula | multiObjectiveFormula);