UNSTABLE_NAME_COLLISIONS in rustc_lint::builtin - Rust
Description: The `unstable_name_collisions` lint detects that you have used a name that the standard library plans to add in the future.

Skip to main content

## UNSTABLE_NAME_COLLISIONS

# Static UNSTABLE_NAME_COLLISIONS

Source

    pub static UNSTABLE_NAME_COLLISIONS: &'static Lint

Expand description

The `unstable_name_collisions` lint detects that you have used a name that the standard library plans to add in the future.

#### §Example

    trait MyIterator : Iterator {
        // is_partitioned is an unstable method that already exists on the Iterator trait
        fn is_partitioned<P>(self, predicate: P) -> bool
        where
            Self: Sized,
            P: FnMut(Self::Item) -> bool,
        {true}
    }

    impl<T: ?Sized> MyIterator for T where T: Iterator { }

    let x = vec![1, 2, 3];
    let _ = x.iter().is_partitioned(|_| true);

{{produces}}

#### §Explanation

When new methods are added to traits in the standard library, they are usually added in an “unstable” form which is only available on the nightly channel with a `feature` attribute. If there is any preexisting code which extends a trait to have a method with the same name, then the names will collide. In the future, when the method is stabilized, this will cause an error due to the ambiguity. This lint is an early-warning to let you know that there may be a collision in the future. This can be avoided by adding type annotations to disambiguate which trait method you intend to call, such as `MyIterator::is_partitioned(my_iter, my_predicate)` or renaming or removing the method.