error[E0432]: unresolved import `core`
  --> $DIR/feature-gate-extern_absolute_paths.rs:11:5
   |
LL | use core::default; //~ ERROR unresolved import `core`
   |     ^^^^ Maybe a missing `extern crate core;`?

error[E0433]: failed to resolve. Maybe a missing `extern crate core;`?
  --> $DIR/feature-gate-extern_absolute_paths.rs:14:19
   |
LL |     let _: u8 = ::core::default::Default(); //~ ERROR failed to resolve
   |                   ^^^^ Maybe a missing `extern crate core;`?

error: aborting due to 2 previous errors

You've got a few errors: E0432, E0433
If you want more information on an error, try using "rustc --explain E0432"