warning: the feature `contracts` is incomplete and may not be safe to use and/or cause compiler crashes
  --> $DIR/contract-attributes-nest.rs:19:12
   |
LL | #![feature(contracts)]
   |            ^^^^^^^^^
   |
   = note: see issue #128044 <https://github.com/rust-lang/rust/issues/128044> for more information
   = note: `#[warn(incomplete_features)]` on by default

warning: 1 warning emitted