var result = ToUtf8(ref MemoryMarshal.GetReference(utf16Source), utf16Source.Length, ref MemoryMarshal.GetReference(utf8Destination), utf8Destination.Length, out var bytesConsumed, out bytesWritten);
=> GetIndexOfFirstInvalidUtf8Sequence(ref MemoryMarshal.GetReference(input), input.Length, out scalarCount, out surrogatePairCount);