error: auto traits are experimental and possibly buggy (see issue #13231)
  --> $DIR/feature-gate-optin-builtin-traits.rs:20:1
   |
20 | auto trait AutoDummyTrait {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(optin_builtin_traits)] to the crate attributes to enable

error: auto trait implementations are experimental and possibly buggy (see issue #13231)
  --> $DIR/feature-gate-optin-builtin-traits.rs:24:1
   |
24 | impl DummyTrait for .. {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(optin_builtin_traits)] to the crate attributes to enable

error: negative trait bounds are not yet fully implemented; use marker types for now (see issue #13231)
  --> $DIR/feature-gate-optin-builtin-traits.rs:27:1
   |
27 | impl !DummyTrait for DummyStruct {}
   | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = help: add #![feature(optin_builtin_traits)] to the crate attributes to enable

error: aborting due to 3 previous errors