[vitus]

Quoting the full section on `T t;`:

- If T is a class type and there is a default constructor, run it.

- If T is an array type, default-initialize each element.

- Otherwise, do nothing.

That decision tree should read: "If T is a class type: it will invoke the default constructor. It is a compile-time error to write this if T does not have a default constructor." Not "if there is a default constructor, run it; otherwise, fall back to doing nothing."

The "do nothing" applies to scalar types such as ints, and indirectly to scalar member variables that aren't explicitly initialized one way or another. Not to classes that have deleted the default constructor.