Contracts core intrinsics.

These are hooks to:

  1. control whether contract checks are run
  2. allow 3rd party tools to intercept and reintepret the results of running contracts.

compiler/rustc_feature/src/builtin_attrs.rs

@@ -19,6 +19,7 @@ const GATED_CFGS: &[GatedCfg] = &[
     // (name in cfg, feature, function to check if the feature is enabled)
     (sym::overflow_checks, sym::cfg_overflow_checks, Features::cfg_overflow_checks),
     (sym::ub_checks, sym::cfg_ub_checks, Features::cfg_ub_checks),
+    (sym::contract_checks, sym::cfg_contract_checks, Features::cfg_contract_checks),
     (sym::target_thread_local, sym::cfg_target_thread_local, Features::cfg_target_thread_local),
     (
         sym::target_has_atomic_equal_alignment,

compiler/rustc_feature/src/unstable.rs

@@ -403,6 +403,8 @@ declare_features! (
     (unstable, c_variadic, "1.34.0", Some(44930)),
     /// Allows the use of `#[cfg(<true/false>)]`.
     (unstable, cfg_boolean_literals, "1.83.0", Some(131204)),
+    /// Allows the use of `#[cfg(contract_checks)` to check if contract checks are enabled.
+    (unstable, cfg_contract_checks, "CURRENT_RUSTC_VERSION", Some(133866)),
     /// Allows the use of `#[cfg(overflow_checks)` to check if integer overflow behaviour.
     (unstable, cfg_overflow_checks, "1.71.0", Some(111466)),
     /// Provides the relocation model information as cfg entry