Note this isn't really specific to Google, or really much of a "convention" (insofar as a convention is something you can reasonably avoid following). This is t

Note this isn't really specific to Google, or really much of a "convention" (insofar as a convention is something you can reasonably avoid following). This is the only correct way to write C++, really -- implicit 1-arg constructors are specifically called "converting constructors" [1], precisely because their very purpose is to define implicit conversions. You don't define them unless implicit conversions make sense for your type. The standard library pays attention to this just as much -- that's why size_t isn't implicitly convertible to std::vector. [1] https://en.cppreference.com/w/cpp/language/converting_constructor https://en.cppreference.com/w/cpp/language/converting_constr...