error[E0658]: rust-call ABI is subject to change
  --> $DIR/feature-gate-unboxed-closures.rs:10:12
   |
LL |     extern "rust-call" fn call_once(self, (a, b): (u32, u32)) -> u32 {
   |            ^^^^^^^^^^^
   |
   = note: see issue #29625 <https://github.com/rust-lang/rust/issues/29625> for more information
   = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0658]: the precise format of `Fn`-family traits' type parameters is subject to change
  --> $DIR/feature-gate-unboxed-closures.rs:5:6
   |
LL | impl FnOnce<(u32, u32)> for Test {
   |      ^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #29625 <https://github.com/rust-lang/rust/issues/29625> for more information
   = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable
   = note: this compiler was built on YYYY-MM-DD; consider upgrading it if it is out of date

error[E0183]: manual implementations of `FnOnce` are experimental
  --> $DIR/feature-gate-unboxed-closures.rs:5:6
   |
LL | impl FnOnce<(u32, u32)> for Test {
   |      ^^^^^^^^^^^^^^^^^^ manual implementations of `FnOnce` are experimental
   |
   = help: add `#![feature(unboxed_closures)]` to the crate attributes to enable

error: aborting due to 3 previous errors

Some errors have detailed explanations: E0183, E0658.
For more information about an error, try `rustc --explain E0183`.