B3, default values, and implicit initialization

[Quân Anh Mai]

> As I mentioned yesterday, the high-order bit here is how we describe a
class whose (null-restricted) instances can tolerate (and possibly even
encourage) uninitialized use, just as the primitives do today.

I think a good starting position would be to consider the way C++ call
them, which is "trivially default constructible", referring to a class with
a zero-argument constructor which performs no action [1]. This name seems
to fit quite well because:

1, It is tied to the action of construction, which immediately signifies
aspects of behaviours it concerns with.

2, It helps the author of the class to make a decision whether the no-op
constructor is a sensible one (a constructor that does not initialize
anything).

3, It helps the users of the class to know whether a class can be
constructed without explicitly invoking a constructor (that is the default
value can be trivially obtainable).

Thanks,
Quan Anh

[1]:
https://en.cppreference.com/w/cpp/language/default_constructor#:~:text=A%20trivial%20default%20constructor%20is,)%20are%20trivially%20default%2Dconstructible
.
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