QString::fromUtf16 cannot be replaced with QString(const ushort *, int)

Reading the documentation for QString::fromUtf16 [1]:
> This function is comparatively slow. Use QString(const ushort *, int) if possible.

So I did, and here is what I got:
> main.cpp:97: error: invalid conversion from 'const ushort*' to 'int'
> main.cpp:97: error: initializing argument 1 of 'QString::QString(int, QChar)'

Note that the documentation page for QString does not mention QString(const ushort *, int). The following constructors are documented:

QString ()
QString ( const QChar * unicode, int size )
QString ( QChar ch )
QString ( int size, QChar ch )
QString ( const QLatin1String & str )
QString ( const QString & other )
QString ( const char * str )
QString ( const QByteArray & ba )

The constructor QString ( const QChar * unicode, int size ) seems most appropriate; however, I think that having QString ( const ushort* unicode, int size ) would be a good thing.

[1] <URL:http://doc.trolltech.com/4.6/qstring.html#fromUtf16>