The issue arises when the unchecked union contains both a fixed part and
a variant part, and is subject to a full representation clause covering
all the components in all the variants, when the component clauses do not
align the variant boundaries with byte boundaries consistently.
Tested on x86_6
The issue arises when the unchecked union contains nested variants, i.e.
variants containing themselves a variant part, and is subject to a full
representation clause covering all the components in all the variants,
when the component clauses do not align the variant boundaries with byte
boundaries
