TryCast returns Warning BC4322 on String

[paul1956]

Version Used:
Vs 2017 15.5.2
Steps to Reproduce:

1. The description of TryCast says that it will not throw an exception, and this error only appears on the line where I am trying to assign the result to a string. String does implement IEnumerable(Of Char).
   Below is not a complete implementation of this routine just enough to show the warning and several cases without the warning.

       Function IsEmpty(Of T)(ByVal lSource As IEnumerable(Of T)) As Boolean
            Dim readOnlyCollection As IReadOnlyCollection(Of T) = TryCast(lSource, IReadOnlyCollection(Of T))
            If readOnlyCollection IsNot Nothing Then
                Return readOnlyCollection.Count = 0
            End If

            Dim genericCollection As ICollection(Of T) = TryCast(lSource, ICollection(Of T))
            If genericCollection IsNot Nothing Then
                Return genericCollection.Count = 0
            End If

            Dim collection As ICollection = TryCast(lSource, ICollection)
            If collection IsNot Nothing Then
                Return collection.Count = 0
            End If

           ' The following line gets Warning on iSource
            Dim str As String = TryCast(**lSource**, String)
            If str IsNot Nothing Then
                Return str.Length = 0
            End If
            Return True
        End Function

2. With the code above there should be no warnings
   Expected Behavior:
   No Warnings
   Actual Behavior:
   Warning BC42322 Runtime errors might occur when converting 'IEnumerable(Of T)' to 'String'.

[AdamSpeight2008]

IEnumerable(Of Char) is trying to be cast as a String. Not String being cast to IEnumerable(Of Char)

[paul1956]

@AdamSpeight2008 good point, it works in C#.

		public static bool IsEmpty<T>(this IEnumerable<T> source)
		{
			var readOnlyCollection = source as IReadOnlyCollection<T>;
			if (readOnlyCollection != null) {
				return readOnlyCollection.Count == 0;
			}

			var genericCollection = source as ICollection<T>;
			if (genericCollection != null) {
				return genericCollection.Count == 0;
			}

			var collection = source as ICollection;
			if (collection != null) {
				return collection.Count == 0;
			}

			var str = source as string;
			if (str != null) {
				return str.Length == 0;
			}
			return true;
		}