Syntax IN dont work with nullable Enums

[fheck]

Similar to #63, I try to build an expression where I want to filter with enum string-values in a list.
Edit: Tested with versions 1.6.4 and 1.6.5.

Consider the following model:

public class Test
{
    public TestEnum? EnumValue { get; set; }
}

public enum TestEnum
{
    Undefined = 0,
    Value1 = 1,
    Value2 = 2,
    Other = 3,
}

Now I try to use the following expression:
"it.EnumValue in (\"Value1\",\"Value2\")"

Unfortunately, this results in the following exception:

System.InvalidOperationException: No coercion operator is defined between types 'System.Nullable`1[TestEnum]' and 'System.Nullable`1[System.Decimal]'.
   at System.Linq.Expressions.Expression.GetUserDefinedCoercionOrThrow(ExpressionType coercionType, Expression expression, Type convertToType)
   at System.Linq.Dynamic.Core.Parser.ExpressionPromoter.Promote(Expression sourceExpression, Type type, Boolean exact, Boolean convertExpression)
   at System.Linq.Dynamic.Core.Parser.SupportedMethods.MethodFinder.IsApplicable(MethodData method, Expression[] args)
   at System.Linq.Dynamic.Core.Parser.SupportedMethods.MethodFinder.<>c__DisplayClass10_0.<FindBestMethodBasedOnArguments>b__1(MethodData m)
   at System.Linq.Enumerable.WhereEnumerableIterator`1.ToArray()
   at System.Linq.Dynamic.Core.Parser.SupportedMethods.MethodFinder.FindBestMethodBasedOnArguments(IEnumerable`1 methods, Expression[]& args, MethodBase& method)
   at System.Linq.Dynamic.Core.Parser.SupportedMethods.MethodFinder.FindMethod(Type type, String methodName, Boolean staticAccess, Expression& instance, Expression[]& args, MethodBase& method)
   at System.Linq.Dynamic.Core.Parser.SupportedMethods.MethodFinder.ContainsMethod(Type type, String methodName, Boolean staticAccess, Expression instance, Expression[]& args)
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.CheckAndPromoteOperands(Type signatures, TokenId opId, String opName, Expression& left, Expression& right, Int32 errorPos)
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseIn()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseAndOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseOrOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseLambdaOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseNullCoalescingOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseConditionalOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.Parse(Type resultType, Boolean createParameterCtor)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(Type delegateType, ParsingConfig parsingConfig, Boolean createParameterCtor, ParameterExpression[] parameters, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(ParsingConfig parsingConfig, Boolean createParameterCtor, ParameterExpression[] parameters, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(ParsingConfig parsingConfig, Boolean createParameterCtor, Type itType, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicQueryableExtensions.Where(IQueryable source, ParsingConfig config, String predicate, Object[] args)
   at System.Linq.Dynamic.Core.DynamicQueryableExtensions.Where[TSource](IQueryable`1 source, ParsingConfig config, String predicate, Object[] args)

If I change the expression and try to go with an parameter instead:

"it.EnumValue in @0", new Dictionary<string, object>{ ["@0", new List<TestEnum> { TestEnum.Value1, TestEnum.Value2 }

I get the following, different, exception:

System.InvalidOperationException: No generic method 'Contains' on type 'System.Linq.Enumerable' is compatible with the supplied type arguments and arguments. No type arguments should be provided if the method is non-generic. 
   at System.Linq.Expressions.Expression.FindMethod(Type type, String methodName, Type[] typeArgs, Expression[] args, BindingFlags flags)
   at System.Linq.Expressions.Expression.Call(Type type, String methodName, Type[] typeArguments, Expression[] arguments)
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseIn()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseAndOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseOrOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseLambdaOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseNullCoalescingOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.ParseConditionalOperator()
   at System.Linq.Dynamic.Core.Parser.ExpressionParser.Parse(Type resultType, Boolean createParameterCtor)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(Type delegateType, ParsingConfig parsingConfig, Boolean createParameterCtor, ParameterExpression[] parameters, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(ParsingConfig parsingConfig, Boolean createParameterCtor, ParameterExpression[] parameters, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicExpressionParser.ParseLambda(ParsingConfig parsingConfig, Boolean createParameterCtor, Type itType, Type resultType, String expression, Object[] values)
   at System.Linq.Dynamic.Core.DynamicQueryableExtensions.Where(IQueryable source, ParsingConfig config, String predicate, Object[] args)
   at System.Linq.Dynamic.Core.DynamicQueryableExtensions.Where[TSource](IQueryable`1 source, ParsingConfig config, String predicate, Object[] args)

It seems the nullabilty of the property breaks something in the expression parser. But I'm not sure how to work around this at the moment.

[StefH]

#932

[StefH]

@fheck thanks for reporting; it's indeed a bug, I'll make a PR.

[fheck]

Wow, thanks for the fast feedback! If I should test something, I will gladly do so tomorrow, when I'm back at work.
(I'm not yet sure how easy it is to build the library with your change applied, but I will figure it out)

[fheck]

@StefH I was able to verify that a local build based on the branch from #932 did not produce the errors from variant 1 above. Thank you very much for the quick fix!

[StefH]

I'll merge PR and close issue.

And I'll try to create a new NuGet version today.