The relevant part of your first link seems to be right at the beginning: > If the operand passed to an arithmetic operator is integral or unscoped enumeration

The relevant part of your first link seems to be right at the beginning: > If the operand passed to an arithmetic operator is integral or unscoped enumeration type, then before any other action (but after lvalue-to-rvalue conversion, if applicable), the operand undergoes integral promotion. Clicking "integral promotion" leads here: https://en.cppreference.com/w/cpp/language/implicit_conversion#Integral_promotion https://en.cppreference.com/w/cpp/language/implicit_conversi...