Trade::id is const – and this constructor tries to set it with an ordinary assignment in the body, exactly
the pattern the lesson warned doesn’t work for const (or reference) members. Submit as-is and read both errors
before fixing anything.
The fix isn’t complicated once you see it: move id’s initialization out of the body entirely and into the member
initializer list, : id(tradeId), which is the only place a const member can legally be given its value. Once
set there, id remains 42 (or whatever value it starts with) for the rest of that Trade object’s life – which
is exactly the point of marking a field like an ID const in the first place.