Add Never to SMIR

compiler/rustc_smir/src/rustc_smir/mod.rs

@@ -132,7 +132,7 @@ impl<'tcx> Tables<'tcx> {
             ty::Dynamic(_, _, _) => todo!(),
             ty::Closure(_, _) => todo!(),
             ty::Generator(_, _, _) => todo!(),
-            ty::Never => todo!(),
+            ty::Never => TyKind::RigidTy(RigidTy::Never),
             ty::Tuple(fields) => TyKind::RigidTy(RigidTy::Tuple(
                 fields.iter().map(|ty| self.intern_ty(ty)).collect(),
             )),

compiler/rustc_smir/src/stable_mir/ty.rs

@@ -32,6 +32,7 @@ pub enum RigidTy {
     Slice(Ty),
     RawPtr(Ty, Mutability),
     Ref(Region, Ty, Mutability),
+    Never,
     Tuple(Vec<Ty>),
 }