error[E0433]: failed to resolve: you might be missing crate `x`
  --> $DIR/issue-82865.rs:5:5
   |
LL | use x::y::z;
   |     ^ you might be missing crate `x`
   |
help: consider importing the `x` crate
   |
LL + extern crate x;
   |

error[E0599]: no function or associated item named `z` found for struct `Box<_, _>` in the current scope
  --> $DIR/issue-82865.rs:8:10
   |
LL |     Box::z
   |          ^ function or associated item not found in `Box<_, _>`
...
LL |     mac!();
   |     ------ in this macro invocation
   |
   = note: this error originates in the macro `mac` (in Nightly builds, run with -Z macro-backtrace for more info)

error: aborting due to 2 previous errors

Some errors have detailed explanations: E0433, E0599.
For more information about an error, try `rustc --explain E0433`.