diff --git a/c/containers/mlhmmv.c b/c/containers/mlhmmv.c
index f16361adc..926c7d950 100644
--- a/c/containers/mlhmmv.c
+++ b/c/containers/mlhmmv.c
@@ -856,16 +856,6 @@ static void mlhmmv_level_put_terminal_no_enlarge(mlhmmv_level_t* plevel, sllmve_
 void mlhmmv_level_to_lrecs(mlhmmv_level_t* plevel, sllmv_t* pkeys, sllmv_t* pnames, sllv_t* poutrecs,
 	int do_full_prefixing, char* flatten_separator)
 {
-	// xxx gross hack. fix this.
-	if (pkeys == NULL || pkeys->phead == NULL) {
-		for (mlhmmv_level_entry_t* pentry = plevel->phead; pentry != NULL; pentry = pentry->pnext) {
-			sllmv_t* pkey = sllmv_single_no_free(&pentry->level_key);
-			mlhmmv_level_to_lrecs(plevel, pkey, pnames, poutrecs, do_full_prefixing, flatten_separator);
-			sllmv_free(pkey);
-		}
-		return;
-	}
-
 	mv_t* pfirstkey = &pkeys->phead->value;
 
 	mlhmmv_level_entry_t* ptop_entry = mlhmmv_level_look_up_and_ref_entry(plevel, pkeys->phead, NULL);
@@ -1533,6 +1523,7 @@ void mlhmmv_root_partial_to_lrecs(mlhmmv_root_t* pmap, sllmv_t* pkeys, sllmv_t*
 	int do_full_prefixing, char* flatten_separator)
 {
 	// There should be at least the oosvar basename, e.g. '@a[b][c]' or '@a[b]' or '@a' but not '@'.
+	MLR_INTERNAL_CODING_ERROR_IF(pkeys == NULL);
 	MLR_INTERNAL_CODING_ERROR_IF(pkeys->phead == NULL);
 
 	mlhmmv_level_to_lrecs(pmap->root_xvalue.pnext_level, pkeys, pnames, poutrecs, do_full_prefixing,
diff --git a/c/dsl/rxval_func_evaluators.c b/c/dsl/rxval_func_evaluators.c
index f029f008f..11655ca1d 100644
--- a/c/dsl/rxval_func_evaluators.c
+++ b/c/dsl/rxval_func_evaluators.c
@@ -25,7 +25,6 @@ static boxed_xval_t rxval_evaluator_variadic_func(void* pvstate, variables_t* pv
 		rxval_evaluator_t* parg = pstate->pargs[i];
 		boxed_xval_t* pbxval = &pstate->pbxvals[i];
 		*pbxval = parg->pprocess_func(parg->pvstate, pvars);
-		// xxx map-check ...
 	}
 
 	boxed_xval_t bxrv = pstate->pfunc(pstate->pbxvals, nargs);
diff --git a/c/todo.txt b/c/todo.txt
index 11118133c..8a0b09f5c 100644
--- a/c/todo.txt
+++ b/c/todo.txt
@@ -30,6 +30,8 @@ OTHER:
   there is a DSL so you *can* loop things out w/ variables etc etc etc but also verbs for
   often-used idioms so you don't *have* to. then show a concise and convincing example.
 
+* 'data prep' <-> 'data cleaning' at covers
+
 ================================================================
 UT FOR 5.0.0: