diff --git a/builtin/iterator.mbt b/builtin/iterator.mbt
index 60718df2b..4ac9c7e0a 100644
--- a/builtin/iterator.mbt
+++ b/builtin/iterator.mbt
@@ -75,7 +75,9 @@ pub impl[X : Show] Show for Iter[X] with output(self, logger) {
 
 ///|
 pub impl[X : ToJson] ToJson for Iter[X] with to_json(self) {
-  Json::array(self.map(x => x.to_json()).collect())
+  [
+    for x in self => x
+  ]
 }
 
 ///|
diff --git a/deque/deque.mbt b/deque/deque.mbt
index 6cd6d3431..7f4bc059b 100644
--- a/deque/deque.mbt
+++ b/deque/deque.mbt
@@ -1675,7 +1675,9 @@ pub fn Deque::join(self : Deque[String], separator : StringView) -> String {
 /// ```
 ///
 pub impl[A : ToJson] ToJson for Deque[A] with to_json(self : Deque[A]) -> Json {
-  Json::array([ for x in self => x.to_json() ])
+  [
+    for x in self => x
+  ]
 }
 
 ///|
diff --git a/hashset/hashset.mbt b/hashset/hashset.mbt
index 4ba3437dd..de0748900 100644
--- a/hashset/hashset.mbt
+++ b/hashset/hashset.mbt
@@ -672,13 +672,9 @@ pub fn[K] HashSet::copy(self : HashSet[K]) -> HashSet[K] {
 ///|
 /// ToJson implementation for hashset
 pub impl[X : ToJson] ToJson for HashSet[X] with to_json(self) {
-  let res = Array::new(capacity=self.size)
-  for entry in self.entries {
-    if entry is Some({ key, .. }) {
-      res.push(key.to_json())
-    }
-  }
-  Json::array(res)
+  [
+    for key in self => key
+  ]
 }
 
 ///|
diff --git a/immut/priority_queue/types.mbt b/immut/priority_queue/types.mbt
index f4375e294..45d6eee2d 100644
--- a/immut/priority_queue/types.mbt
+++ b/immut/priority_queue/types.mbt
@@ -30,5 +30,7 @@ priv enum Node[A] {
 pub impl[A : ToJson + Compare] ToJson for PriorityQueue[A] with to_json(
   self : PriorityQueue[A],
 ) {
-  Json::array([ for item in self => item.to_json() ])
+  [
+    for item in self => item
+  ]
 }
diff --git a/immut/sorted_set/immutable_set.mbt b/immut/sorted_set/immutable_set.mbt
index baef33676..50d129590 100644
--- a/immut/sorted_set/immutable_set.mbt
+++ b/immut/sorted_set/immutable_set.mbt
@@ -791,7 +791,9 @@ pub impl[A : Show] Show for SortedSet[A] with output(self, logger) {
 
 ///|
 pub impl[A : ToJson] ToJson for SortedSet[A] with to_json(self) {
-  Json::array([ for a in self => a.to_json() ])
+  [
+    for a in self => a.to_json()
+  ]
 }
 
 ///|
diff --git a/immut/vector/vector.mbt b/immut/vector/vector.mbt
index 8c55c2f6e..a23314630 100644
--- a/immut/vector/vector.mbt
+++ b/immut/vector/vector.mbt
@@ -666,7 +666,9 @@ pub impl[A : Show] Show for Vector[A] with output(self, logger) {
 
 ///|
 pub impl[A : ToJson] ToJson for Vector[A] with to_json(self) {
-  Json::array([ for value in self => value.to_json() ])
+  [
+    for value in self => value
+  ]
 }
 
 ///|
diff --git a/immut/vector/vector_test.mbt b/immut/vector/vector_test.mbt
index 770db86e3..82fbaada1 100644
--- a/immut/vector/vector_test.mbt
+++ b/immut/vector/vector_test.mbt
@@ -79,7 +79,7 @@ test "to_array empty" {
 ///|
 test "to_json" {
   let v = @vector.from_iter((0).until(40))
-  let expected = Json::array(Array::makei(40, i => i.to_json()))
+  let expected : Json = [ for i in 0..<40 => i ]
   @json.json_inspect(v, content=expected)
   let empty : @vector.Vector[Int] = @vector.new()
   @json.json_inspect(empty, content=[])
diff --git a/list/list.mbt b/list/list.mbt
index 766a850be..bfd46ed81 100644
--- a/list/list.mbt
+++ b/list/list.mbt
@@ -94,13 +94,9 @@ pub impl[A : Show] Show for List[A] with output(xs, logger) {
 /// ToJson implementation for List.
 /// Converts a list to a JSON array.
 pub impl[A : ToJson] ToJson for List[A] with to_json(self) {
-  let capacity = self.length()
-  guard capacity != 0 else { return [] }
-  let jsons = Array::new(capacity~)
-  for a in self {
-    jsons.push(a.to_json())
-  }
-  Json::array(jsons)
+  [
+    for a in self => a
+  ]
 }
 
 ///|
diff --git a/priority_queue/moon.pkg b/priority_queue/moon.pkg
index 4437e2f80..3c969ea88 100644
--- a/priority_queue/moon.pkg
+++ b/priority_queue/moon.pkg
@@ -4,12 +4,12 @@ import {
   "moonbitlang/core/debug",
   "moonbitlang/core/quickcheck",
   "moonbitlang/core/quickcheck/splitmix",
-  "moonbitlang/core/json",
 }
 
 import {
   "moonbitlang/core/random",
   "moonbitlang/core/cmp",
+  "moonbitlang/core/json",
 } for "test"
 
 options(
diff --git a/priority_queue/priority_queue.mbt b/priority_queue/priority_queue.mbt
index a80aff59c..2ad65990c 100644
--- a/priority_queue/priority_queue.mbt
+++ b/priority_queue/priority_queue.mbt
@@ -142,7 +142,9 @@ pub fn[A : Compare] PriorityQueue::iter(self : PriorityQueue[A]) -> Iter[A] {
 
 ///|
 pub impl[A : ToJson + Compare] ToJson for PriorityQueue[A] with to_json(self) {
-  Json::array([ for x in self => x.to_json() ])
+  [
+    for x in self => x
+  ]
 }
 
 ///|
diff --git a/set/linked_hash_set.mbt b/set/linked_hash_set.mbt
index b067d816e..f9f416828 100644
--- a/set/linked_hash_set.mbt
+++ b/set/linked_hash_set.mbt
@@ -594,11 +594,9 @@ pub fn[K : Hash + Eq] Set::intersection(
 
 ///|
 pub impl[X : ToJson] ToJson for Set[X] with to_json(self) {
-  let res = Array::new(capacity=self.size)
-  for v in self {
-    res.push(v.to_json())
-  }
-  Json::array(res)
+  [
+    for v in self => v
+  ]
 }
 
 ///|