# Static rustc_lint_defs::builtin::INEFFECTIVE_UNSTABLE_TRAIT_IMPL

source ·

    pub static INEFFECTIVE_UNSTABLE_TRAIT_IMPL: &Lint

Expand description

The `ineffective_unstable_trait_impl` lint detects `#[unstable]` attributes which are not used.

#### §Example

ⓘ

    #![feature(staged_api)]

    #[derive(Clone)]
    #[stable(feature = "x", since = "1")]
    struct S {}

    #[unstable(feature = "y", issue = "none")]
    impl Copy for S {}

{{produces}}

#### §Explanation

`staged_api` does not currently support using a stability attribute on `impl` blocks. `impl`s are always stable if both the type and trait are stable, and always unstable otherwise.