error[E0793]: reference to packed field is unaligned
  --> $DIR/repr_packed.rs:21:24
   |
LL |         println!("{}", foo.x);
   |                        ^^^^^
   |
   = note: packed structs are only aligned by one byte, and many modern architectures penalize unaligned field accesses
   = note: creating a misaligned reference is undefined behavior (even if that reference is never dereferenced)
   = help: copy the field contents to a local variable, or replace the reference with a raw pointer and use `read_unaligned`/`write_unaligned` (loads and stores via `*p` must be properly aligned even when using raw pointers)
   = note: this error originates in the macro `$crate::format_args_nl` which comes from the expansion of the macro `println` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to previous error

For more information about this error, try `rustc --explain E0793`.