src/test/ui/feature-gates/feature-gate-needs-allocator.stderr

error[E0658]: the `#[needs_allocator]` attribute is an experimental feature
  --> $DIR/feature-gate-needs-allocator.rs:1:1
   |
LL | #![needs_allocator] //~ ERROR the `#[needs_allocator]` attribute is
   | ^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(allocator_internals)] to the crate attributes to enable

error: aborting due to previous error

For more information about this error, try `rustc --explain E0658`.