The meaning of "fetched from memory" is vague, and the two uses of term
"access" [defns.access] are inappropreate here because
  - it causes undefined behavior to access an inactive member of a
    union, based on the rule of out-of-lifetime object [basic.life]:
    > The program has undefined behavior if:
    >   - the glvalue is used to access the object, or
  - it implies reading the referenced object of std::nullptr_t,
    which is defined to be a side effect for volatile-qualified case.
    [intro.execution]
    > Reading an object designated by a volatile glvalue, ... are all
    > side effects, ...

- "read the object" -> "access the object"
  The "read" was derived from the rule at [intro.execution], but it
  didn't fit well here.
- "the object" -> "the object to which the glvalue refers"
  Make it clear what "the object" refers to.

cplusplus#2372 (review)