, scrut_var /= case_bndr

       -- Consider: case x of x { ... }

       -- Do not add [x :-> x] to occ_bs_env, else lookupBndrSwap will loop

         , occ_bs_rng = rng_vars `extendVarSet` case_bndr'

                        `unionVarSet` tyCoVarsOfMCo mco }

     env1 = addBinderUnfolding env case_bndr con_app_unf

     -- See Note [Add unfolding for scrutinee]

     env2 | DoBinderSwap v mco <- bndr_swap

          = addBinderUnfolding env1 v $

               if isReflMCo mco  -- isReflMCo: avoid calling mk_simple_unf

               then con_app_unf  --            twice in the common case

          | otherwise = env1

 scrutOkForBinderSwap :: OutExpr -> BinderSwapDecision

 -- If (scrutOkForBinderSwap e = DoBinderSwap v mco, then

 -- See Note [Case of cast]

 -- See Historical Note [Care with binder-swap on dictionaries]

 --

   = case e of

       Tick _ e        -> scrutOkForBinderSwap e  -- Drop ticks

       Var v           -> DoBinderSwap v MRefl

                          -- Cast: see Note [Case of cast]

       _               -> NoBinderSwap