# Bug - https://github.com/dotnet/corefx/issues/6017
MembersMustExist : Member 'System.Linq.Enumerable.Append<TSource>(System.Collections.Generic.IEnumerable<TSource>, TSource)' does not exist in the implementation but it does exist in the contract.
MembersMustExist : Member 'System.Linq.Enumerable.Prepend<TSource>(System.Collections.Generic.IEnumerable<TSource>, TSource)' does not exist in the implementation but it does exist in the contract.