Object types don’t have a self type specified. Therefore, when
we convert the principal trait-ref into a normal trait-ref,
you must give some self type. A common choice is
or some placeholder type.
Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain
repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.
Size: 24 bytes