Nobody answer.
So i think it is a bug of Qt Creator.
I resolve this in other way, instead of
Qt Code:
  1. m_substCodeToPair[c] = std::pair<int,int>(a,b);
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i can write
Qt Code:
  1. m_substCodeToPair[c] = std::make_pair(a,b);
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and now i not see any underline.
I write this, for a case some other people use this std classes with Qt.
Anyway QPair works at expected with Qt Creator.
Daniel