A unsolved ambiguous compile error

[Radongas]

When we try to use it after import in out project on Unity3D 2018.4.23f1, the compiler alert the following exception:

error CS0121: The call is ambiguous between the following methods or properties: 'RSG.Promises.EnumerableExt.Each(System.Collections.Generic.IEnumerable, System.Action<T, int>)' and 'RSG.Promises.EnumerableExt.Each(System.Collections.Generic.IEnumerable, System.Action<T, int>)'

It seems that there are 2 methods with exactly same name in the file "EnumerableExt.cs", which are both named with "Each" with different uses of paramater.
We have try to rename each of these two guys but it did not work in their other referenced block.