RSRP-288411: Cast() when converting to LINQ expressions

Consider this simple (a bit silly) code:

IEnumerable<Stream> Yield() {
    var a = new[] {new MemoryStream()};
    foreach (var i in a)
        yield return i;
}

ReSharper 6.1.42.60 suggests to convert the foreach to a LINQ expression. This transforms the code into:

IEnumerable<Stream> Yield() {
    var a = new[] {new MemoryStream()};
    return a.Cast<Stream>();
}

Here Cast<Stream>() is unnecessary in .NET 4 (covariance), but more importantly, it should never suggest to apply Cast<T>() on an IEnumerable<T>(). Cast<T>() is not type-safe, it should only be suggested for non-generic IEnumerables. If I later change the array to something like:

var a = new[] {new StringBuilder()};

ReSharper shows a "suspicious cast" warning, but there is of course no warning or error from the compiler.

If anything, ReSharper should transform to a Select<T>() with an explicit cast, e.g. a.Select(x => (Stream)x);