Here is this document https://web.mit.edu/rust-lang_v1.25/arch/amd64_ubuntu1404/share/doc/rust/html/book/first-edition/unsized-types.html It is says that
Only the last field in a struct may have a dynamically sized type; the other fields must not. Enum variants must not have dynamically sized types as data..

Here I’m not able to understand reason behind such restriction. What make difference in last field?