//@ compile-flags: -Zcontract-checks=yes #![feature(contracts)] //~^ WARN the feature `contracts` is incomplete and may not be safe to use and/or cause compiler crashes [incomplete_features] struct Baz { baz: i32 } #[track_caller] #[core::contracts::requires(x.baz > 0)] #[core::contracts::ensures({let old = x; move |ret:&Baz| ret.baz == old.baz*2 })] // Relevant thing is this: ^^^^^^^^^^^ // because we are capturing state that is non-Copy. //~^^^ ERROR trait bound `Baz: std::marker::Copy` is not satisfied fn doubler(x: Baz) -> Baz { Baz { baz: x.baz + 10 } } fn main() { assert_eq!(doubler(Baz { baz: 10 }).baz, 20); assert_eq!(doubler(Baz { baz: 100 }).baz, 200); }