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_mir_dataflow/src/move_paths/builder.rs

@@ -417,7 +417,11 @@ impl<'a, 'tcx, F: Fn(Ty<'tcx>) -> bool> MoveDataBuilder<'a, 'tcx, F> {
             | Rvalue::Discriminant(..)
             | Rvalue::Len(..)
             | Rvalue::NullaryOp(
-                NullOp::SizeOf | NullOp::AlignOf | NullOp::OffsetOf(..) | NullOp::UbChecks,
+                NullOp::SizeOf
+                | NullOp::AlignOf
+                | NullOp::OffsetOf(..)
+                | NullOp::UbChecks
+                | NullOp::ContractChecks,
                 _,
             ) => {}
         }