Strange use of [] in C++. What is happening?

First of all, this is not a dummy question about arrays or operator[] overload!

I was trying to compile Qt Creator and I've received an error in this method:

static QList getNonEditorDocumentFactories()
{
    return ExtensionSystem::PluginManager::getObjects(
        [](IDocumentFactory *factory) {
            return !qobject_cast(factory);
        });
}

The error is:

mainwindow.cpp:748: error: expected primary-expression before ‘[’ token
mainwindow.cpp:748: error: expected primary-expression before ‘]’ token
mainwindow.cpp:748: error: expected primary-expression before ‘*’ token
mainwindow.cpp:748: error: ‘factory’ was not declared in this scope

I know that I'm doing something wrong to compile Qt Creator, probably g++ version, but the question is not that.

I would like to understand this code because for me this use of [] is syntactically incorrect. Can someone please explain me what is happening here.