tests/ui-fulldeps/internal-lints/query_stability.rs

// compile-flags: -Z unstable-options

#![feature(rustc_private)]
#![deny(rustc::potential_query_instability)]

extern crate rustc_data_structures;

use rustc_data_structures::fx::{FxHashMap, FxHashSet};

fn main() {
    let mut x = FxHashMap::<u32, i32>::default();

    for _ in x.drain() {}
    //~^ ERROR using `drain` can result in unstable

    for _ in x.iter() {}
    //~^ ERROR using `iter`

    for _ in Some(&mut x).unwrap().iter_mut() {}
    //~^ ERROR using `iter_mut`

    for _ in x {}
    //~^ ERROR using `into_iter`
}