[Interest] Operator QMap<uint, uint>[] is casting to int?

[Jason H]

Given the code below:
QMap<uint, uint> reverseHistogram;
...
QList<uint> reverseKeys = reverseHistogram.keys();
int foregroundIndex = reverseHistogram.size()-2;           // arg, QMap::size() returns signed
uint foregroundPixels = reverseKeys[foregroundIndex];
uint foregroundColor = reverseKeys[foregroundPixels];
uint foregroundColor = reverseKeys[foregroundPixels]; //main.cpp:66:37: warning: implicit conversion changes signedness: 'uint' (aka 'unsigned int') to 'int'

Where is the "signed" conversion happening?