tests/ui/assert_is_empty.rs

#![warn(clippy::assert_is_empty)]
#![allow(clippy::useless_vec)]
#![allow(clippy::const_is_empty, clippy::needless_ifs)]

fn main() {
    let vec = vec![1, 2, 3];
    assert!(vec.is_empty());
    //~^ assert_is_empty
    assert!(!vec.is_empty());
    //~^ assert_is_empty
    debug_assert!(vec.is_empty());
    //~^ assert_is_empty
    debug_assert!(!vec.is_empty());
    //~^ assert_is_empty

    let vec_ref = &vec;
    assert!(vec_ref.is_empty());
    //~^ assert_is_empty
    assert!(!vec_ref.is_empty());
    //~^ assert_is_empty

    let vec_mut_ref = &mut vec![1, 2, 3];
    assert!(vec_mut_ref.is_empty());
    //~^ assert_is_empty

    let slice: &[i32] = &[1, 2, 3];
    assert!(slice.is_empty());
    //~^ assert_is_empty
    assert!(!slice.is_empty());
    //~^ assert_is_empty

    let array = [1, 2, 3];
    assert!(array.is_empty());
    //~^ assert_is_empty
    assert!(!array.is_empty());
    //~^ assert_is_empty

    let array_ref = &array;
    assert!(array_ref.is_empty());
    //~^ assert_is_empty

    let string = String::from("foo");
    assert!(string.is_empty());
    //~^ assert_is_empty
    assert!(!string.is_empty());
    //~^ assert_is_empty

    let str_ref = "foo";
    assert!(str_ref.is_empty());
    //~^ assert_is_empty
    assert!(!str_ref.is_empty());
    //~^ assert_is_empty

    // Don't lint: has assert message.
    assert!(vec.is_empty(), "items should be empty");
    assert!(!vec.is_empty(), "items should not be empty");
    assert!(vec.is_empty(), "unexpected values: {vec:?}");
    assert!(!vec.is_empty(), "unexpected values: {vec:?}");

    // Common chained assertion shape. The first assertion can hide the value
    // that the second assertion would otherwise help diagnose.
    let items = vec!["baz"];
    assert!(!items.is_empty());
    //~^ assert_is_empty
    assert_eq!(items[0], "bar");

    // Don't lint: the outer `assert!` is written here, but the condition comes
    // from a macro expansion. Rewriting the expanded condition span would make
    // the suggestion point at generated code rather than source code.
    macro_rules! is_empty {
        ($value:expr) => {
            $value.is_empty()
        };
    }
    assert!(is_empty!(vec));

    // Don't lint: the `assert!` itself comes from a macro expansion. The lint
    // only rewrites assert calls that are present at the call site.
    macro_rules! assert_empty {
        ($value:expr) => {
            assert!($value.is_empty())
        };
    }
    assert_empty!(vec);

    // Don't lint: not an assert macro.
    if vec.is_empty() {}
    if !vec.is_empty() {}

    // Don't lint: maps do not have a compact empty literal suggestion. This is
    // a conservative call; comparing against `HashMap::new()` may be worth
    // revisiting if the type inference cost and constructor path are acceptable
    // for aliases, custom hashers, and similar map types.
    let map = std::collections::HashMap::<i32, i32>::new();
    assert!(map.is_empty());
    assert!(!map.is_empty());

    // Don't lint: assert_eq! would require Debug and PartialEq for the element type.
    struct NotDebugOrPartialEq;
    let not_debug_or_partial_eq = vec![NotDebugOrPartialEq];
    assert!(not_debug_or_partial_eq.is_empty());

    #[derive(Debug)]
    struct NotPartialEq;
    let not_partial_eq = vec![NotPartialEq];
    assert!(not_partial_eq.is_empty());

    #[derive(PartialEq)]
    struct NotDebug;
    let not_debug = vec![NotDebug];
    assert!(not_debug.is_empty());
}