Use qsizetype when interfacing with QStrings and QLists to avoid warnings

From the corresponding mailinglist thread:

since QString, QList, etc. are using qsizetype for indexing- and size-operations.
What is the plan with classes working with aforementioned container classes which are still using int in their interfaces?
If they keep using int there could be a lot of warnings like this one:
warning: implicit conversion loses integer precision: 'qsizetype' (aka 'long long') to 'int' [-Wshorten-64-to-32]
Or you have to plaster your code with casts. E.g. every time you pass an index of your container to your model class.

Some classes which are probably affected:
QtCore:

• QAbstractItemModel and subclasses (using QList or std::vector as data storage)
• QModelIndex
• QRegularExpression (match offset)
• QStringMatcher
• QSyntaxHighlighter
• QTextBoundaryFinder
• QXmlString::size

QtGui:

• QTextCursor
• QTextDocument (find offset, character{At,Count})
• QTextLayout
• QValidator and subclasses (validate offset)

QtWidgets:

• QAbstractItemView and subclasses
• QLineEdit