Getting error on IEnumerable Sum() method: "violates the constraint of type 'TAccumulator'."

[pburrows]

I have an expression:

Enemies.Sum(p=>p.TotalDollarsEarned) > 50

Where "Enemies" is a parameter of type List<ComplexExpressionParameter>

Defined as:

    private class ComplexExpressionParameter
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public decimal TotalDollarsEarned { get; set; }
    }

I am getting the error (I'll paste the full error at the bottom):

 ---> System.Security.VerificationException: Method System.Linq.Enumerable.Sum: type argument 'System.Object' violates the constraint of type parameter 'TAccumulator'.

Is there something I'm missing in getting Sum() to work? It looks like some issue where the variable Enemies is an object and not an IEnumerable, but I'm not sure what to do about that. I already tried casting it as List in my expression and that doesn't work.

---

Full Error:

System.ArgumentException: GenericArguments[2], 'System.Object', on 'TResult Sum[TSource,TResult,TAccumulator](System.Collections.Generic.IEnumerable`1[TSource], System.Func`2[TSource,TResult])' violates the constraint of type 'TAccumulator'.
 ---> System.Security.VerificationException: Method System.Linq.Enumerable.Sum: type argument 'System.Object' violates the constraint of type parameter 'TAccumulator'.
   at System.RuntimeMethodHandle.GetStubIfNeeded(RuntimeMethodHandleInternal method, RuntimeType declaringType, RuntimeType[] methodInstantiation)
   at System.Reflection.RuntimeMethodInfo.MakeGenericMethod(Type[] methodInstantiation)
   --- End of inner exception stack trace ---
   at System.RuntimeType.ValidateGenericArguments(MemberInfo definition, RuntimeType[] genericArguments, Exception e)
   at System.Reflection.RuntimeMethodInfo.MakeGenericMethod(Type[] methodInstantiation)
   at DynamicExpresso.Parsing.Parser.MakeGenericMethod(MethodData method)
   at DynamicExpresso.Parsing.Parser.CheckIfMethodIsApplicableAndPrepareIt(MethodData method, Expression[] args)
   at DynamicExpresso.Parsing.Parser.<>c__DisplayClass110_0.<FindBestMethod>b__0(MethodData m)
   at System.Linq.Enumerable.WhereEnumerableIterator`1.ToArray()
   at DynamicExpresso.Parsing.Parser.FindBestMethod(IEnumerable`1 methods, Expression[] args)
   at DynamicExpresso.Parsing.Parser.FindBestMethod(IEnumerable`1 methods, Expression[] args)
   at DynamicExpresso.Parsing.Parser.FindExtensionMethods(String methodName, Expression[] args)
   at DynamicExpresso.Parsing.Parser.ParseExtensionMethodInvocation(Type type, Expression instance, Int32 errorPos, String id, Expression[] args)
   at DynamicExpresso.Parsing.Parser.ParseMethodInvocation(Type type, Expression instance, Int32 errorPos, String methodName)
   at DynamicExpresso.Parsing.Parser.ParseMemberAccess(Type type, Expression instance)
   at DynamicExpresso.Parsing.Parser.ParseMemberAccess(Expression instance)
   at DynamicExpresso.Parsing.Parser.ParsePrimary()
   at DynamicExpresso.Parsing.Parser.ParseUnary()
   at DynamicExpresso.Parsing.Parser.ParseMultiplicative()
   at DynamicExpresso.Parsing.Parser.ParseAdditive()
   at DynamicExpresso.Parsing.Parser.ParseShift()
   at DynamicExpresso.Parsing.Parser.ParseTypeTesting()
   at DynamicExpresso.Parsing.Parser.ParseComparison()
   at DynamicExpresso.Parsing.Parser.ParseLogicalAnd()
   at DynamicExpresso.Parsing.Parser.ParseLogicalXor()
   at DynamicExpresso.Parsing.Parser.ParseLogicalOr()
   at DynamicExpresso.Parsing.Parser.ParseConditionalAnd()
   at DynamicExpresso.Parsing.Parser.ParseConditionalOr()
   at DynamicExpresso.Parsing.Parser.ParseConditional()
   at DynamicExpresso.Parsing.Parser.ParseAssignment()
   at DynamicExpresso.Parsing.Parser.ParseExpressionSegment()
   at DynamicExpresso.Parsing.Parser.ParseExpressionSegment(Type returnType)
   at DynamicExpresso.Parsing.Parser.Parse()
   at DynamicExpresso.Parsing.Parser.Parse(ParserArguments arguments)
   at DynamicExpresso.Interpreter.ParseAsLambda(String expressionText, Type expressionType, Parameter[] parameters)
   at DynamicExpresso.Interpreter.Parse(String expressionText, Type expressionType, Parameter[] parameters)
   at DynamicExpresso.Interpreter.Parse(String expressionText, Parameter[] parameters)
   at Commissions.Api.CommissionPlans.Engine.ExpressionEngines.DynamicExpresso.DynamicExpressoHelpers.GetLambdaFromExpression(String expression, Parameter[] parameters, Boolean cache) in ...

[davideicardi]

Can you provide a simple unit test like this to reproduce the problem?
Where we can also see how you have configured the Interpreter.

[pburrows]

Here is a self-contained unit test that fails with the above error:

    [Fact]
    public async Task SimpleTest()
    {
        
        var expression = "Enemies.Sum(p=>p.TotalDollarsEarned) > 50";
        var parameters = new List<Parameter>()
        {
            new("Enemies", typeof(List<ComplexType>), new List<ComplexType>()
            {
                new ComplexType() { FirstName = "A", LastName = "B", TotalDollarsEarned = 75 },
                new ComplexType() { FirstName = "C", LastName = "D", TotalDollarsEarned = 792 },
            })
        };
       
        var options = InterpreterOptions.Default | InterpreterOptions.LambdaExpressions;
        var interpreter = new Interpreter(options)
            .Reference(typeof(DateTime))
            .Reference(typeof(DateTimeOffset))
            .Reference(typeof(TimeSpan));
        interpreter.SetDefaultNumberType(DefaultNumberType.Decimal);
        var lambda = interpreter.Parse(expression, parameters.ToArray());
    }

    private class ComplexType
    {
        public string FirstName { get; set; }
        public string LastName { get; set; }
        public decimal TotalDollarsEarned { get; set; }
    }

note: I add DateTime, DateTimeOffset, and TimeSpan references because of other uses, this is a cut-down example, but I wanted to leave that bit in case it was conflicting with something.

[pburrows]

Hey @davideicardi , do you think this is a bug? Should I report it as an Issue?

[davideicardi]

Yes, it looks like a bug. I will convert this to an issue.

[pburrows]

Thanks!

[metoule]

This seems like a duplicate of #270, which is fixed via #274. Not sure if it's part of a release yet?

[metoule]

Fixed in 2.16.0 🎉