Introduce GeneratorWitnessMIR.

compiler/rustc_const_eval/src/interpret/intrinsics.rs

@@ -101,6 +101,7 @@ pub(crate) fn eval_nullary_intrinsic<'tcx>(
             | ty::Closure(_, _)
             | ty::Generator(_, _, _)
             | ty::GeneratorWitness(_)
+            | ty::GeneratorWitnessMIR(_, _)
             | ty::Never
             | ty::Tuple(_)
             | ty::Error(_) => ConstValue::from_machine_usize(0u64, &tcx),

compiler/rustc_const_eval/src/interpret/validity.rs

@@ -602,6 +602,7 @@ impl<'rt, 'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> ValidityVisitor<'rt, 'mir, '
             | ty::Bound(..)
             | ty::Param(..)
             | ty::Alias(..)
+            | ty::GeneratorWitnessMIR(..)
             | ty::GeneratorWitness(..) => bug!("Encountered invalid type {:?}", ty),
         }
     }