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_smir/src/rustc_smir/convert/mir.rs

@@ -291,6 +291,7 @@ impl<'tcx> Stable<'tcx> for mir::NullOp<'tcx> {
                 indices.iter().map(|idx| idx.stable(tables)).collect(),
             ),
             UbChecks => stable_mir::mir::NullOp::UbChecks,
+            ContractChecks => stable_mir::mir::NullOp::ContractChecks,
         }
     }
 }