contracts.rs

//! Unstable module containing the unstable contracts lang items and attribute macros.

pub use crate::macros::builtin::{contracts_ensures as ensures, contracts_requires as requires};

/// This is an identity function used as part of the desugaring of the `#[ensures]` attribute.
///
/// This is an existing hack to allow users to omit the type of the return value in their ensures
/// attribute.
///
/// Ideally, rustc should be able to generate the type annotation.
/// The existing lowering logic makes it rather hard to add the explicit type annotation,
/// while the function call is fairly straight forward.
#[unstable(feature = "contracts_internals", issue = "128044" /* compiler-team#759 */)]
// Similar to `contract_check_requires`, we need to use the user-facing
// `contracts` feature rather than the perma-unstable `contracts_internals`.
// Const-checking doesn't honor allow_internal_unstable logic used by contract expansion.
#[rustc_const_unstable(feature = "contracts", issue = "128044")]
#[lang = "contract_build_check_ensures"]
pub const fn build_check_ensures<Ret, C>(cond: C) -> C
where
    C: Fn(&Ret) -> bool + Copy + 'static,
{
    cond
}