For Each over Dictionary.Keys can report Array as the element type

Iterating over the Keys property from an untyped Dictionary with a typed For Each loop variable can produce a misleading compiler error: For Each variable type 'String' does not match collection element type 'Array'. The bundled dictionary docs also show key-iteration examples without making clear that For Each key As String In dict.Keys requires a parameterised dictionary such as Dictionary(Of String, ...), making the example easy to copy into code that uses an untyped dictionary.