static_cast<const int&>(v1 = 1) = 1
static_cast<const double&>(v1 = 3.14) = 3.14
static_cast<const double&>(v2 = v1) = 3.14
static_cast<const char* const&>(v2 = "abc") = abc
static_cast<const char* const&>(v1 = v2) = abc
static_cast<const char&>(v3) = exception