System information (version)

• OpenCV =>3.20
• Operating System / Platform =>Windows 64 Bit
• Compiler => Visual Studio 2013

Detailed description

cv::Matx33f tmp = true

compiles because it uses the single-parameter constructor Matx(_Tp v0); //!< 1x1 matrix.
This is especially a problem here:

bool foo(std::string, cv::Matx33f bar, bool foobar = true) {}

foo("awesome", true); // You are not warned that you forgot a parameter