diff --git a/RandomDo/Monad/ForInInstances.lean b/RandomDo/Monad/ForInInstances.lean
index 99d8103..7edc181 100644
--- a/RandomDo/Monad/ForInInstances.lean
+++ b/RandomDo/Monad/ForInInstances.lean
@@ -29,10 +29,17 @@ instance instMeasurableSpaceArray : MeasurableSpace (Array α) :=
 instance instMeasurableSpaceVector {n : ℕ} : MeasurableSpace (Vector α n) :=
   MeasurableSpace.comap Vector.toArray inferInstance
 
+instance instMeasurableSpaceSubarray : MeasurableSpace (Subarray α) :=
+  MeasurableSpace.comap (fun s : Subarray α ↦ s.toList) inferInstance
+
 @[fun_prop]
 lemma measurable_toList : Measurable (Array.toList : Array α → List α) :=
   Measurable.of_comap_le fun _ a ↦ a
 
+@[fun_prop]
+lemma measurable_subarray_toList : Measurable (fun s : Subarray α ↦ s.toList) :=
+  Measurable.of_comap_le fun _ a ↦ a
+
 @[fun_prop]
 lemma measurable_toArray {n : ℕ} : Measurable (Vector.toArray : Vector α n → Array α) :=
   Measurable.of_comap_le fun _ a ↦ a
diff --git a/RandomDo/Monad/Notation.lean b/RandomDo/Monad/Notation.lean
index 7d06205..2d2542b 100644
--- a/RandomDo/Monad/Notation.lean
+++ b/RandomDo/Monad/Notation.lean
@@ -139,7 +139,7 @@ def rdoForDecl := leading_parser
           | none => break
           | some ($y, s') =>
             $s:ident := s'
-            rdo $body)
+            do $body)
     doElems := doElems.push (← `(doSeqItem| for%$tk $[$h? : ]? $x:ident in $xs rdo $body))
     `(doElem| do $doElems*)
   | _ => Macro.throwUnsupported
diff --git a/Test/Gaps.lean b/Test/Gaps.lean
index 09b1b72..39aeb1c 100644
--- a/Test/Gaps.lean
+++ b/Test/Gaps.lean
@@ -18,47 +18,6 @@ open MeasureTheory ProbabilityTheory
 
 namespace Test.Gaps
 
-/-! ## `for` over several collections
-
-TODO: the expander at `RandomDo/Monad/Notation.lean:141` wraps the loop body in a fresh term-level
-`rdo` block, which severs it from the block around it. Emitting `do $body` instead — a nested
-`doElem`, which is what core's otherwise identical expander does — fixes all three tests below.
--/
-
-/--
-error: Variable `s` cannot be mutated. Only variables declared using `let mut` can be mutated.
-      If you did not intend to mutate but define `s`, consider using `let s` instead
--/
-#guard_msgs in
-def zipMut (xs ys : List ℕ) : IdM ℕ := rdo
-  let mut s := 0
-  for x in xs, y in ys rdo
-    s := s + x * y
-  return s
-
-/--
-error: Type mismatch
-  some x
-has type
-  Option ℕ
-but is expected to have type
-  Unit
--/
-#guard_msgs in
-def zipReturn (xs ys : List ℕ) : IdM (Option ℕ) := rdo
-  for x in xs, y in ys rdo
-    if x = y then
-      return some x
-  return none
-
-/-- error: `break` must be nested inside a loop -/
-#guard_msgs in
-def zipThree (xs ys zs : List ℕ) : IdM Bool := rdo
-  for x in xs, y in ys, z in zs rdo
-    if x + y = z then
-      return true
-  return false
-
 /-! ## Nested loops
 
 TODO: register a `ControlInfo` inference handler for `RDo.rdoFor`, mirroring the rule core states