why doesn't this work?

[Luck]

struct Base
{
Base() : i(0){}
int i;
};

struct Derived : public Base
{
Derived() : i(1){}
};

 

[Victor Bazarov]

struct Base
{
Base() : i(0){}
int i;
};

struct Derived : public Base
{
Derived() : i(1){}
};

You're only allowed to initialise classes own bases and members.
Exception is a virtual base class, but yours is not the case.

If you need to initialise 'i' in derived, you need to give Base
a parameterised constructor:

struct Base
{
Base(int i_ = 0) : i(i_) {}
int i;
};

struct Derived : public Base
{
Derived() : Base(1) {}
};

Notice how I kept 'Base's constructor "default" by giving its 'i_'
the default value of 0. Essentially it's the same as your Base().

V