error[E0658]: use of unstable library feature 'structural_match'
  --> $DIR/feature-gate.rs:29:6
   |
LL | impl std::marker::StructuralPartialEq for Foo { }
   |      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #31434 <https://github.com/rust-lang/rust/issues/31434> for more information
   = help: add `#![feature(structural_match)]` to the crate attributes to enable

error[E0658]: use of unstable library feature 'structural_match'
  --> $DIR/feature-gate.rs:31:6
   |
LL | impl std::marker::StructuralEq for Foo { }
   |      ^^^^^^^^^^^^^^^^^^^^^^^^^
   |
   = note: see issue #31434 <https://github.com/rust-lang/rust/issues/31434> for more information
   = help: add `#![feature(structural_match)]` to the crate attributes to enable

error: aborting due to 2 previous errors

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