diff --git a/CHANGELOG.md b/CHANGELOG.md
index 163f5bed43..97cb781c08 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -50,6 +50,7 @@
 - Build tests with bsb and move them out of jscomp. https://github.com/rescript-lang/rescript-compiler/pull/7068
 - Run `build_tests` on Windows. https://github.com/rescript-lang/rescript-compiler/pull/7065
 - Rename folder "jscomp" to "compiler". https://github.com/rescript-lang/rescript-compiler/pull/7086
+- Disable -bs-cross-module-opt for tests. https://github.com/rescript-lang/rescript-compiler/pull/7071
 
 # 12.0.0-alpha.3
 
diff --git a/lib/es6/char.js b/lib/es6/char.js
index 6686f5d84f..b2a6536046 100644
--- a/lib/es6/char.js
+++ b/lib/es6/char.js
@@ -1,10 +1,6 @@
 
 
 
-function chr(prim) {
-  return prim;
-}
-
 function escaped(param) {
   let exit = 0;
   if (param >= 40) {
@@ -83,7 +79,6 @@ function equal(c1, c2) {
 }
 
 export {
-  chr,
   escaped,
   lowercase_ascii,
   uppercase_ascii,
diff --git a/lib/js/char.js b/lib/js/char.js
index ae5ee0dba6..e854a99cd0 100644
--- a/lib/js/char.js
+++ b/lib/js/char.js
@@ -1,10 +1,6 @@
 'use strict';
 
 
-function chr(prim) {
-  return prim;
-}
-
 function escaped(param) {
   let exit = 0;
   if (param >= 40) {
@@ -82,7 +78,6 @@ function equal(c1, c2) {
   return (c1 - c2 | 0) === 0;
 }
 
-exports.chr = chr;
 exports.escaped = escaped;
 exports.lowercase_ascii = lowercase_ascii;
 exports.uppercase_ascii = uppercase_ascii;
diff --git a/runtime/char.res b/runtime/char.res
index a3f1b05ecc..133e63b873 100644
--- a/runtime/char.res
+++ b/runtime/char.res
@@ -10,7 +10,7 @@ external code: t => int = "%identity"
 
 external unsafe_chr: int => t = "%identity"
 
-let chr = unsafe_chr
+external chr: int => t = "%identity"
 
 external bytes_create: int => array<char> = "Array"
 
diff --git a/runtime/char.resi b/runtime/char.resi
index 97320d7118..3ee638c888 100644
--- a/runtime/char.resi
+++ b/runtime/char.resi
@@ -10,7 +10,7 @@ external code: char => int = "%identity"
    Raise [Invalid_argument "Char.chr"] if the argument is
    outside the range 0--255. */
 @deprecated("Use Core instead. This will be removed in v13")
-let chr: int => char
+external chr: int => char = "%identity"
 
 /** Return a string representing the given character,
     with special characters escaped following the lexical conventions
diff --git a/tests/tests/rescript.json b/tests/tests/rescript.json
index 71a10aaea0..69ceca9c90 100644
--- a/tests/tests/rescript.json
+++ b/tests/tests/rescript.json
@@ -11,7 +11,6 @@
     "in-source": true
   },
   "bsc-flags": [
-    "-bs-cross-module-opt",
     "-w -3-6-26-27-29-30-32..40-44-45-52-60-9-106+104",
     "-warn-error A"
   ]
diff --git a/tests/tests/src/Import.js b/tests/tests/src/Import.js
index 5885147fd7..0831e85187 100644
--- a/tests/tests/src/Import.js
+++ b/tests/tests/src/Import.js
@@ -1,13 +1,14 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Js_promise = require("rescript/lib/js/js_promise.js");
 
 async function eachIntAsync(list, f) {
   return (await import("rescript/lib/js/belt_List.js").then(m => m.forEach))(list, f);
 }
 
 function eachIntLazy(list, f) {
-  return import("rescript/lib/js/belt_List.js").then(m => m.forEach).then(each => Promise.resolve(each(list, f)));
+  return Js_promise.then_(each => Promise.resolve(each(list, f)), import("rescript/lib/js/belt_List.js").then(m => m.forEach));
 }
 
 eachIntLazy({
diff --git a/tests/tests/src/SafePromises.js b/tests/tests/src/SafePromises.js
index 3dd5d546de..05a637b8a0 100644
--- a/tests/tests/src/SafePromises.js
+++ b/tests/tests/src/SafePromises.js
@@ -1,6 +1,7 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Js_promise = require("rescript/lib/js/js_promise.js");
 let Js_promise2 = require("rescript/lib/js/js_promise2.js");
 
 async function nestedPromise(xxx) {
@@ -10,7 +11,7 @@ async function nestedPromise(xxx) {
     console.log("Promise2.catch_", x);
     return Promise.resolve(0);
   });
-  xx.then(x => Promise.resolve((console.log("Promise.then_", x), undefined)));
+  Js_promise.then_(x => Promise.resolve((console.log("Promise.then_", x), undefined)), xx);
 }
 
 async function create(x) {
diff --git a/tests/tests/src/belt_hashmap_test.js b/tests/tests/src/belt_hashmap_test.js
index b3ff0630a1..9500a537f2 100644
--- a/tests/tests/src/belt_hashmap_test.js
+++ b/tests/tests/src/belt_hashmap_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Mocha = require("mocha");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Hashtbl = require("rescript/lib/js/hashtbl.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
 let Test_utils = require("./test_utils.js");
@@ -9,7 +10,6 @@ let Belt_HashMap = require("rescript/lib/js/belt_HashMap.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 let Belt_SortArray = require("rescript/lib/js/belt_SortArray.js");
 let Array_data_util = require("./array_data_util.js");
-let Belt_internalBucketsType = require("rescript/lib/js/belt_internalBucketsType.js");
 
 function intEq(x, y) {
   return x === y;
@@ -19,19 +19,16 @@ let intHash = Hashtbl.hash;
 
 let cmp = Primitive_int.compare;
 
-let Y = {
-  hash: intHash,
-  eq: intEq
-};
+let Y = Belt_Id.hashable(intHash, intEq);
 
-let empty = Belt_internalBucketsType.make(intHash, intEq, 30);
+let empty = Belt_HashMap.make(30, Y);
 
 Mocha.describe("Belt_hashmap_test", () => {
   Mocha.test("fromArray", () => {
     let u = Belt_Array.concat(Array_data_util.randomRange(30, 100), Array_data_util.randomRange(40, 120));
     let v = Belt_Array.zip(u, u);
     let xx = Belt_HashMap.fromArray(v, Y);
-    Test_utils.eq("File \"belt_hashmap_test.res\", line 21, characters 7-14", xx.size, 91);
+    Test_utils.eq("File \"belt_hashmap_test.res\", line 21, characters 7-14", Belt_HashMap.size(xx), 91);
     Test_utils.eq("File \"belt_hashmap_test.res\", line 22, characters 7-14", Belt_SortArray.stableSortBy(Belt_HashMap.keysToArray(xx), cmp), Array_data_util.range(30, 120));
   });
   Mocha.test("mergeMany", () => {
@@ -54,21 +51,21 @@ Mocha.describe("Belt_hashmap_test", () => {
       ]
     ]);
     Test_utils.eq("File \"belt_hashmap_test.res\", line 27, characters 7-14", Belt_HashMap.get(empty, 2), 2);
-    Test_utils.eq("File \"belt_hashmap_test.res\", line 28, characters 7-14", empty.size, 3);
+    Test_utils.eq("File \"belt_hashmap_test.res\", line 28, characters 7-14", Belt_HashMap.size(empty), 3);
   });
   Mocha.test("remove", () => {
     let u = Belt_Array.concat(Array_data_util.randomRange(0, 100000), Array_data_util.randomRange(0, 100));
-    let v = Belt_internalBucketsType.make(intHash, intEq, 40);
+    let v = Belt_HashMap.make(40, Y);
     Belt_HashMap.mergeMany(v, Belt_Array.zip(u, u));
-    Test_utils.eq("File \"belt_hashmap_test.res\", line 35, characters 7-14", v.size, 100001);
+    Test_utils.eq("File \"belt_hashmap_test.res\", line 35, characters 7-14", Belt_HashMap.size(v), 100001);
     for (let i = 0; i <= 1000; ++i) {
       Belt_HashMap.remove(v, i);
     }
-    Test_utils.eq("File \"belt_hashmap_test.res\", line 39, characters 7-14", v.size, 99000);
+    Test_utils.eq("File \"belt_hashmap_test.res\", line 39, characters 7-14", Belt_HashMap.size(v), 99000);
     for (let i$1 = 0; i$1 <= 2000; ++i$1) {
       Belt_HashMap.remove(v, i$1);
     }
-    Test_utils.eq("File \"belt_hashmap_test.res\", line 43, characters 7-14", v.size, 98000);
+    Test_utils.eq("File \"belt_hashmap_test.res\", line 43, characters 7-14", Belt_HashMap.size(v), 98000);
     Test_utils.ok("File \"belt_hashmap_test.res\", line 44, characters 7-14", Belt_Array.every(Array_data_util.range(2001, 100000), x => Belt_HashMap.has(v, x)));
   });
 });
@@ -93,4 +90,4 @@ exports.intHash = intHash;
 exports.cmp = cmp;
 exports.Y = Y;
 exports.empty = empty;
-/* empty Not a pure module */
+/* Y Not a pure module */
diff --git a/tests/tests/src/belt_hashset_int_test.js b/tests/tests/src/belt_hashset_int_test.js
index 4cce65ce9f..ae2f9df81d 100644
--- a/tests/tests/src/belt_hashset_int_test.js
+++ b/tests/tests/src/belt_hashset_int_test.js
@@ -8,7 +8,6 @@ let Belt_SetInt = require("rescript/lib/js/belt_SetInt.js");
 let Array_data_util = require("./array_data_util.js");
 let Belt_HashSetInt = require("rescript/lib/js/belt_HashSetInt.js");
 let Belt_SortArrayInt = require("rescript/lib/js/belt_SortArrayInt.js");
-let Belt_internalBucketsType = require("rescript/lib/js/belt_internalBucketsType.js");
 
 function add(x, y) {
   return x + y | 0;
@@ -28,7 +27,7 @@ Mocha.describe("Belt_hashset_int_test", () => {
   Mocha.test("fromArray", () => {
     let u = Belt_Array.concat(Array_data_util.randomRange(30, 100), Array_data_util.randomRange(40, 120));
     let v = Belt_HashSetInt.fromArray(u);
-    Test_utils.eq("File \"belt_hashset_int_test.res\", line 22, characters 7-14", v.size, 91);
+    Test_utils.eq("File \"belt_hashset_int_test.res\", line 22, characters 7-14", Belt_HashSetInt.size(v), 91);
     let xs = Belt_SetInt.toArray(Belt_SetInt.fromArray(Belt_HashSetInt.toArray(v)));
     Test_utils.eq("File \"belt_hashset_int_test.res\", line 24, characters 7-14", xs, Array_data_util.range(30, 120));
     Test_utils.eq("File \"belt_hashset_int_test.res\", line 26, characters 7-14", Belt_HashSetInt.reduce(v, 0, add), 6825);
@@ -36,17 +35,17 @@ Mocha.describe("Belt_hashset_int_test", () => {
   });
   Mocha.test("mergeMany", () => {
     let u = Belt_Array.concat(Array_data_util.randomRange(0, 100000), Array_data_util.randomRange(0, 100));
-    let v = Belt_internalBucketsType.make(undefined, undefined, 40);
+    let v = Belt_HashSetInt.make(40);
     Belt_HashSetInt.mergeMany(v, u);
-    Test_utils.eq("File \"belt_hashset_int_test.res\", line 34, characters 7-14", v.size, 100001);
+    Test_utils.eq("File \"belt_hashset_int_test.res\", line 34, characters 7-14", Belt_HashSetInt.size(v), 100001);
     for (let i = 0; i <= 1000; ++i) {
       Belt_HashSetInt.remove(v, i);
     }
-    Test_utils.eq("File \"belt_hashset_int_test.res\", line 38, characters 7-14", v.size, 99000);
+    Test_utils.eq("File \"belt_hashset_int_test.res\", line 38, characters 7-14", Belt_HashSetInt.size(v), 99000);
     for (let i$1 = 0; i$1 <= 2000; ++i$1) {
       Belt_HashSetInt.remove(v, i$1);
     }
-    Test_utils.eq("File \"belt_hashset_int_test.res\", line 42, characters 7-14", v.size, 98000);
+    Test_utils.eq("File \"belt_hashset_int_test.res\", line 42, characters 7-14", Belt_HashSetInt.size(v), 98000);
   });
   Mocha.test("stableSortInPlace", () => {
     let u0 = Belt_HashSetInt.fromArray(Array_data_util.randomRange(0, 100000));
diff --git a/tests/tests/src/belt_list_test.js b/tests/tests/src/belt_list_test.js
index 9fcd7ddb76..bfa1e498b1 100644
--- a/tests/tests/src/belt_list_test.js
+++ b/tests/tests/src/belt_list_test.js
@@ -1791,13 +1791,7 @@ Mocha.describe("Belt_list_test", () => {
       }
     }, (x, y) => x === y), false);
   });
-  Mocha.test("add", () => Test_utils.eq("File \"belt_list_test.res\", line 307, characters 7-14", {
-    hd: 2,
-    tl: {
-      hd: 3,
-      tl: /* [] */0
-    }
-  }, {
+  Mocha.test("add", () => Test_utils.eq("File \"belt_list_test.res\", line 307, characters 7-14", Belt_List.add(Belt_List.add(/* [] */0, 3), 2), {
     hd: 2,
     tl: {
       hd: 3,
diff --git a/tests/tests/src/belt_sortarray_test.js b/tests/tests/src/belt_sortarray_test.js
index f3e6b0a8b6..67730112d2 100644
--- a/tests/tests/src/belt_sortarray_test.js
+++ b/tests/tests/src/belt_sortarray_test.js
@@ -4,6 +4,7 @@
 let Mocha = require("mocha");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
 let Belt_Range = require("rescript/lib/js/belt_Range.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Test_utils = require("./test_utils.js");
 let Belt_SortArray = require("rescript/lib/js/belt_SortArray.js");
 let Array_data_util = require("./array_data_util.js");
@@ -215,12 +216,12 @@ Mocha.describe("Belt_sortarray_test", () => {
     ]);
   });
   Mocha.test("binarySearchBy", () => {
-    Test_utils.eq("File \"belt_sortarray_test.res\", line 108, characters 7-14", Belt_SortArray.binarySearchBy([
+    Test_utils.eq("File \"belt_sortarray_test.res\", line 108, characters 7-14", Pervasives.lnot(Belt_SortArray.binarySearchBy([
       1,
       3,
       5,
       7
-    ], 4, cmp) ^ -1, 2);
+    ], 4, cmp)), 2);
     Test_utils.eq("File \"belt_sortarray_test.res\", line 109, characters 7-14", Belt_SortArray.binarySearchBy([
       1,
       2,
@@ -269,11 +270,11 @@ Mocha.describe("Belt_sortarray_test", () => {
     let aa = Array_data_util.range(0, 1000);
     Test_utils.ok("File \"belt_sortarray_test.res\", line 115, characters 7-14", Belt_Range.every(0, 1000, i => Belt_SortArray.binarySearchBy(aa, i, cmp) === i));
     let cc = Belt_Array.map(Array_data_util.range(0, 2000), x => (x << 1));
-    Test_utils.eq("File \"belt_sortarray_test.res\", line 118, characters 7-14", Belt_SortArray.binarySearchBy(cc, 5000, cmp) ^ -1, 2001);
-    Test_utils.eq("File \"belt_sortarray_test.res\", line 119, characters 7-14", Belt_SortArray.binarySearchBy(cc, -1, cmp) ^ -1, 0);
+    Test_utils.eq("File \"belt_sortarray_test.res\", line 118, characters 7-14", Pervasives.lnot(Belt_SortArray.binarySearchBy(cc, 5000, cmp)), 2001);
+    Test_utils.eq("File \"belt_sortarray_test.res\", line 119, characters 7-14", Pervasives.lnot(Belt_SortArray.binarySearchBy(cc, -1, cmp)), 0);
     Test_utils.eq("File \"belt_sortarray_test.res\", line 120, characters 7-14", Belt_SortArray.binarySearchBy(cc, 0, cmp), 0);
-    Test_utils.eq("File \"belt_sortarray_test.res\", line 122, characters 7-14", Belt_SortArray.binarySearchBy(cc, 1, cmp) ^ -1, 1);
-    Test_utils.ok("File \"belt_sortarray_test.res\", line 124, characters 6-13", Belt_Range.every(0, 1999, i => (Belt_SortArray.binarySearchBy(cc, (i << 1) + 1 | 0, cmp) ^ -1) === (i + 1 | 0)));
+    Test_utils.eq("File \"belt_sortarray_test.res\", line 122, characters 7-14", Pervasives.lnot(Belt_SortArray.binarySearchBy(cc, 1, cmp)), 1);
+    Test_utils.ok("File \"belt_sortarray_test.res\", line 124, characters 6-13", Belt_Range.every(0, 1999, i => Pervasives.lnot(Belt_SortArray.binarySearchBy(cc, (i << 1) + 1 | 0, cmp)) === (i + 1 | 0)));
   });
   Mocha.test("strictlySortedLength", () => {
     let lt = (x, y) => x < y;
diff --git a/tests/tests/src/bench.js b/tests/tests/src/bench.js
index 90120890bf..1349784df0 100644
--- a/tests/tests/src/bench.js
+++ b/tests/tests/src/bench.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 
 function map(f, a) {
   let f$1 = x => f(x);
@@ -22,11 +23,7 @@ function init(l, f) {
     return [];
   }
   if (l < 0) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Array.init",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Array.init");
   }
   let res = Belt_Array.make(l, f$1(0));
   for (let i = 1; i < l; ++i) {
diff --git a/tests/tests/src/bs_map_set_dict_test.js b/tests/tests/src/bs_map_set_dict_test.js
index 1fc35b08e0..4314bf8138 100644
--- a/tests/tests/src/bs_map_set_dict_test.js
+++ b/tests/tests/src/bs_map_set_dict_test.js
@@ -2,7 +2,9 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_Map = require("rescript/lib/js/belt_Map.js");
+let Belt_Set = require("rescript/lib/js/belt_Set.js");
 let Belt_List = require("rescript/lib/js/belt_List.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
 let Belt_MapDict = require("rescript/lib/js/belt_MapDict.js");
@@ -26,51 +28,23 @@ function b(loc, v) {
   Mt.bool_suites(test_id, suites, loc, v);
 }
 
-let Icmp = {
-  cmp: Primitive_int.compare
-};
+let Icmp = Belt_Id.comparable(Primitive_int.compare);
 
-let Icmp2 = {
-  cmp: Primitive_int.compare
-};
+let Icmp2 = Belt_Id.comparable(Primitive_int.compare);
 
-let Ic3 = {
-  cmp: Primitive_int.compare
-};
+let Ic3 = Belt_Id.comparable(Primitive_int.compare);
 
-let m0_cmp = Icmp.cmp;
+let m0 = Belt_Map.make(Icmp);
 
-let m0 = {
-  cmp: m0_cmp,
-  data: undefined
-};
+let m00 = Belt_Set.make(Ic3);
 
-let m00_cmp = Ic3.cmp;
+let I2 = Belt_Id.comparable((x, y) => Primitive_int.compare(y, x));
 
-let m00 = {
-  cmp: m00_cmp,
-  data: undefined
-};
+let m = Belt_Map.make(Icmp2);
 
-let I2 = {
-  cmp: (x, y) => Primitive_int.compare(y, x)
-};
-
-let m_cmp = Icmp2.cmp;
-
-let m = {
-  cmp: m_cmp,
-  data: undefined
-};
+let m2 = Belt_Map.make(I2);
 
-let m2_cmp = I2.cmp;
-
-let m2 = {
-  cmp: m2_cmp,
-  data: undefined
-};
-
-let data;
+let data = Belt_Map.getData(m);
 
 Belt_Map.getId(m2);
 
@@ -80,32 +54,29 @@ for (let i = 0; i <= 100000; ++i) {
   data = Belt_MapDict.set(data, i, i, m_dict.cmp);
 }
 
-let data$1 = data;
-
-let newm_cmp = m_dict.cmp;
-
-let newm = {
-  cmp: newm_cmp,
-  data: data$1
-};
+let newm = Belt_Map.packIdData(m_dict, data);
 
 console.log(newm);
 
 let m11 = Belt_MapDict.set(undefined, 1, 1, Icmp.cmp);
 
+Belt_Map.make(Icmp);
+
 console.log(m11);
 
+let v = Belt_Set.make(Icmp2);
+
 let m_dict$1 = Belt_Map.getId(m);
 
 let cmp = m_dict$1.cmp;
 
-let data$2;
+let data$1 = Belt_Set.getData(v);
 
 for (let i$1 = 0; i$1 <= 100000; ++i$1) {
-  data$2 = Belt_SetDict.add(data$2, i$1, cmp);
+  data$1 = Belt_SetDict.add(data$1, i$1, cmp);
 }
 
-console.log(data$2);
+console.log(data$1);
 
 function f(none) {
   return Belt_Map.fromArray(none, Icmp);
@@ -122,7 +93,7 @@ let u0 = Belt_Map.fromArray(Belt_Array.map(Array_data_util.randomRange(0, 39), x
 
 let u1 = Belt_Map.set(u0, 39, 120);
 
-b("File \"bs_map_set_dict_test.res\", line 72, characters 4-11", Belt_Array.every2(Belt_MapDict.toArray(u0.data), Belt_Array.map(Array_data_util.range(0, 39), x => [
+b("File \"bs_map_set_dict_test.res\", line 72, characters 4-11", Belt_Array.every2(Belt_Map.toArray(u0), Belt_Array.map(Array_data_util.range(0, 39), x => [
   x,
   x
 ]), (param, param$1) => {
@@ -133,7 +104,7 @@ b("File \"bs_map_set_dict_test.res\", line 72, characters 4-11", Belt_Array.ever
   }
 }));
 
-b("File \"bs_map_set_dict_test.res\", line 79, characters 4-11", Belt_List.every2(Belt_MapDict.toList(u0.data), Belt_List.fromArray(Belt_Array.map(Array_data_util.range(0, 39), x => [
+b("File \"bs_map_set_dict_test.res\", line 79, characters 4-11", Belt_List.every2(Belt_Map.toList(u0), Belt_List.fromArray(Belt_Array.map(Array_data_util.range(0, 39), x => [
   x,
   x
 ])), (param, param$1) => {
@@ -156,7 +127,7 @@ let u = Belt_Map.fromArray(Belt_Array.makeByAndShuffle(10000, x => [
 eq("File \"bs_map_set_dict_test.res\", line 90, characters 5-12", Belt_Array.makeBy(10000, x => [
   x,
   x
-]), Belt_MapDict.toArray(u.data));
+]), Belt_Map.toArray(u));
 
 Mt.from_pair_suites("Bs_map_set_dict_test", suites.contents);
 
@@ -204,4 +175,4 @@ exports.ISet = ISet;
 exports.S0 = S0;
 exports.f = f;
 exports.$eq$tilde = $eq$tilde;
-/*  Not a pure module */
+/* Icmp Not a pure module */
diff --git a/tests/tests/src/bs_mutable_set_test.js b/tests/tests/src/bs_mutable_set_test.js
index 6ce4a559aa..7d51cde696 100644
--- a/tests/tests/src/bs_mutable_set_test.js
+++ b/tests/tests/src/bs_mutable_set_test.js
@@ -8,8 +8,6 @@ let Belt_Range = require("rescript/lib/js/belt_Range.js");
 let Array_data_util = require("./array_data_util.js");
 let Primitive_array = require("rescript/lib/js/primitive_array.js");
 let Belt_MutableSetInt = require("rescript/lib/js/belt_MutableSetInt.js");
-let Belt_internalAVLset = require("rescript/lib/js/belt_internalAVLset.js");
-let Belt_internalSetInt = require("rescript/lib/js/belt_internalSetInt.js");
 
 let suites = {
   contents: /* [] */0
@@ -27,11 +25,7 @@ function b(loc, x) {
   Mt.bool_suites(test_id, suites, loc, x);
 }
 
-let xs = Array_data_util.range(0, 30);
-
-let u = {
-  data: Belt_internalSetInt.fromArray(xs)
-};
+let u = Belt_MutableSetInt.fromArray(Array_data_util.range(0, 30));
 
 b("File \"bs_mutable_set_test.res\", line 21, characters 8-15", Belt_MutableSetInt.removeCheck(u, 0));
 
@@ -41,13 +35,13 @@ b("File \"bs_mutable_set_test.res\", line 23, characters 8-15", Belt_MutableSetI
 
 b("File \"bs_mutable_set_test.res\", line 24, characters 8-15", Belt_MutableSetInt.removeCheck(u, 20));
 
-eq("File \"bs_mutable_set_test.res\", line 25, characters 9-16", Belt_internalAVLset.size(u.data), 28);
+eq("File \"bs_mutable_set_test.res\", line 25, characters 9-16", Belt_MutableSetInt.size(u), 28);
 
 let r = Array_data_util.randomRange(0, 30);
 
-b("File \"bs_mutable_set_test.res\", line 27, characters 8-15", 29 === Belt_internalAVLset.maxUndefined(u.data));
+b("File \"bs_mutable_set_test.res\", line 27, characters 8-15", 29 === Belt_MutableSetInt.maxUndefined(u));
 
-b("File \"bs_mutable_set_test.res\", line 28, characters 8-15", 1 === Belt_internalAVLset.minUndefined(u.data));
+b("File \"bs_mutable_set_test.res\", line 28, characters 8-15", 1 === Belt_MutableSetInt.minUndefined(u));
 
 Belt_MutableSetInt.add(u, 3);
 
@@ -65,7 +59,7 @@ Belt_MutableSetInt.add(u, 2);
 
 Belt_MutableSetInt.add(u, 0);
 
-eq("File \"bs_mutable_set_test.res\", line 38, characters 9-16", Belt_internalAVLset.size(u.data), 3);
+eq("File \"bs_mutable_set_test.res\", line 38, characters 9-16", Belt_MutableSetInt.size(u), 3);
 
 b("File \"bs_mutable_set_test.res\", line 39, characters 8-15", !Belt_MutableSetInt.isEmpty(u));
 
@@ -79,39 +73,35 @@ Belt_MutableSetInt.mergeMany(u, Array_data_util.randomRange(0, 20000));
 
 Belt_MutableSetInt.mergeMany(u, Array_data_util.randomRange(0, 200));
 
-eq("File \"bs_mutable_set_test.res\", line 46, characters 9-16", Belt_internalAVLset.size(u.data), 20001);
+eq("File \"bs_mutable_set_test.res\", line 46, characters 9-16", Belt_MutableSetInt.size(u), 20001);
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(0, 200));
 
-eq("File \"bs_mutable_set_test.res\", line 48, characters 9-16", Belt_internalAVLset.size(u.data), 19800);
+eq("File \"bs_mutable_set_test.res\", line 48, characters 9-16", Belt_MutableSetInt.size(u), 19800);
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(0, 1000));
 
-eq("File \"bs_mutable_set_test.res\", line 50, characters 9-16", Belt_internalAVLset.size(u.data), 19000);
+eq("File \"bs_mutable_set_test.res\", line 50, characters 9-16", Belt_MutableSetInt.size(u), 19000);
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(0, 1000));
 
-eq("File \"bs_mutable_set_test.res\", line 52, characters 9-16", Belt_internalAVLset.size(u.data), 19000);
+eq("File \"bs_mutable_set_test.res\", line 52, characters 9-16", Belt_MutableSetInt.size(u), 19000);
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(1000, 10000));
 
-eq("File \"bs_mutable_set_test.res\", line 54, characters 9-16", Belt_internalAVLset.size(u.data), 10000);
+eq("File \"bs_mutable_set_test.res\", line 54, characters 9-16", Belt_MutableSetInt.size(u), 10000);
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(10000, 19999));
 
-eq("File \"bs_mutable_set_test.res\", line 56, characters 9-16", Belt_internalAVLset.size(u.data), 1);
+eq("File \"bs_mutable_set_test.res\", line 56, characters 9-16", Belt_MutableSetInt.size(u), 1);
 
-b("File \"bs_mutable_set_test.res\", line 57, characters 8-15", Belt_internalSetInt.has(u.data, 20000));
+b("File \"bs_mutable_set_test.res\", line 57, characters 8-15", Belt_MutableSetInt.has(u, 20000));
 
 Belt_MutableSetInt.removeMany(u, Array_data_util.randomRange(10000, 30000));
 
 b("File \"bs_mutable_set_test.res\", line 59, characters 8-15", Belt_MutableSetInt.isEmpty(u));
 
-let xs$1 = Array_data_util.randomRange(1000, 2000);
-
-let v = {
-  data: Belt_internalSetInt.fromArray(xs$1)
-};
+let v = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(1000, 2000));
 
 let bs = Belt_Array.map(Array_data_util.randomRange(500, 1499), x => Belt_MutableSetInt.removeCheck(v, x));
 
@@ -125,7 +115,7 @@ let indeedRemoved = Belt_Array.reduce(bs, 0, (acc, x) => {
 
 eq("File \"bs_mutable_set_test.res\", line 72, characters 9-16", indeedRemoved, 500);
 
-eq("File \"bs_mutable_set_test.res\", line 73, characters 9-16", Belt_internalAVLset.size(v.data), 501);
+eq("File \"bs_mutable_set_test.res\", line 73, characters 9-16", Belt_MutableSetInt.size(v), 501);
 
 let cs = Belt_Array.map(Array_data_util.randomRange(500, 2000), x => Belt_MutableSetInt.addCheck(v, x));
 
@@ -139,31 +129,29 @@ let indeedAded = Belt_Array.reduce(cs, 0, (acc, x) => {
 
 eq("File \"bs_mutable_set_test.res\", line 82, characters 9-16", indeedAded, 1000);
 
-eq("File \"bs_mutable_set_test.res\", line 83, characters 9-16", Belt_internalAVLset.size(v.data), 1501);
+eq("File \"bs_mutable_set_test.res\", line 83, characters 9-16", Belt_MutableSetInt.size(v), 1501);
 
-b("File \"bs_mutable_set_test.res\", line 84, characters 8-15", Belt_MutableSetInt.isEmpty({
-  data: undefined
-}));
+b("File \"bs_mutable_set_test.res\", line 84, characters 8-15", Belt_MutableSetInt.isEmpty(Belt_MutableSetInt.make()));
 
-eq("File \"bs_mutable_set_test.res\", line 85, characters 9-16", Belt_internalAVLset.minimum(v.data), 500);
+eq("File \"bs_mutable_set_test.res\", line 85, characters 9-16", Belt_MutableSetInt.minimum(v), 500);
 
-eq("File \"bs_mutable_set_test.res\", line 86, characters 9-16", Belt_internalAVLset.maximum(v.data), 2000);
+eq("File \"bs_mutable_set_test.res\", line 86, characters 9-16", Belt_MutableSetInt.maximum(v), 2000);
 
-eq("File \"bs_mutable_set_test.res\", line 87, characters 9-16", Belt_internalAVLset.minUndefined(v.data), 500);
+eq("File \"bs_mutable_set_test.res\", line 87, characters 9-16", Belt_MutableSetInt.minUndefined(v), 500);
 
-eq("File \"bs_mutable_set_test.res\", line 88, characters 9-16", Belt_internalAVLset.maxUndefined(v.data), 2000);
+eq("File \"bs_mutable_set_test.res\", line 88, characters 9-16", Belt_MutableSetInt.maxUndefined(v), 2000);
 
 eq("File \"bs_mutable_set_test.res\", line 89, characters 9-16", Belt_MutableSetInt.reduce(v, 0, (x, y) => x + y | 0), 1876250);
 
-b("File \"bs_mutable_set_test.res\", line 90, characters 8-15", Belt_List.eq(Belt_internalAVLset.toList(v.data), Belt_List.makeBy(1501, i => i + 500 | 0), (x, y) => x === y));
+b("File \"bs_mutable_set_test.res\", line 90, characters 8-15", Belt_List.eq(Belt_MutableSetInt.toList(v), Belt_List.makeBy(1501, i => i + 500 | 0), (x, y) => x === y));
 
-eq("File \"bs_mutable_set_test.res\", line 91, characters 9-16", Belt_internalAVLset.toArray(v.data), Array_data_util.range(500, 2000));
+eq("File \"bs_mutable_set_test.res\", line 91, characters 9-16", Belt_MutableSetInt.toArray(v), Array_data_util.range(500, 2000));
 
-Belt_internalAVLset.checkInvariantInternal(v.data);
+Belt_MutableSetInt.checkInvariantInternal(v);
 
-eq("File \"bs_mutable_set_test.res\", line 93, characters 9-16", Belt_internalSetInt.get(v.data, 3), undefined);
+eq("File \"bs_mutable_set_test.res\", line 93, characters 9-16", Belt_MutableSetInt.get(v, 3), undefined);
 
-eq("File \"bs_mutable_set_test.res\", line 94, characters 9-16", Belt_internalSetInt.get(v.data, 1200), 1200);
+eq("File \"bs_mutable_set_test.res\", line 94, characters 9-16", Belt_MutableSetInt.get(v, 1200), 1200);
 
 let match = Belt_MutableSetInt.split(v, 1000);
 
@@ -175,9 +163,9 @@ let aa = match$1[0];
 
 b("File \"bs_mutable_set_test.res\", line 96, characters 8-15", match[1]);
 
-b("File \"bs_mutable_set_test.res\", line 97, characters 8-15", Belt_Array.eq(Belt_internalAVLset.toArray(aa.data), Array_data_util.range(500, 999), (x, y) => x === y));
+b("File \"bs_mutable_set_test.res\", line 97, characters 8-15", Belt_Array.eq(Belt_MutableSetInt.toArray(aa), Array_data_util.range(500, 999), (x, y) => x === y));
 
-b("File \"bs_mutable_set_test.res\", line 98, characters 8-15", Belt_Array.eq(Belt_internalAVLset.toArray(bb.data), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_mutable_set_test.res\", line 98, characters 8-15", Belt_Array.eq(Belt_MutableSetInt.toArray(bb), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
 
 b("File \"bs_mutable_set_test.res\", line 99, characters 8-15", Belt_MutableSetInt.subset(aa, v));
 
@@ -199,9 +187,9 @@ let aa$1 = match$3[0];
 
 b("File \"bs_mutable_set_test.res\", line 105, characters 8-15", !match$2[1]);
 
-b("File \"bs_mutable_set_test.res\", line 106, characters 8-15", Belt_Array.eq(Belt_internalAVLset.toArray(aa$1.data), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_mutable_set_test.res\", line 106, characters 8-15", Belt_Array.eq(Belt_MutableSetInt.toArray(aa$1), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
 
-b("File \"bs_mutable_set_test.res\", line 107, characters 8-15", Belt_Array.eq(Belt_internalAVLset.toArray(bb$1.data), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_mutable_set_test.res\", line 107, characters 8-15", Belt_Array.eq(Belt_MutableSetInt.toArray(bb$1), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
 
 b("File \"bs_mutable_set_test.res\", line 108, characters 8-15", Belt_MutableSetInt.subset(aa$1, v));
 
@@ -209,156 +197,54 @@ b("File \"bs_mutable_set_test.res\", line 109, characters 8-15", Belt_MutableSet
 
 b("File \"bs_mutable_set_test.res\", line 110, characters 8-15", Belt_MutableSetInt.isEmpty(Belt_MutableSetInt.intersect(aa$1, bb$1)));
 
-let xs$2 = Array_data_util.randomRange(0, 100);
+let aa$2 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 100));
 
-let aa$2 = {
-  data: Belt_internalSetInt.fromArray(xs$2)
-};
+let bb$2 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(40, 120));
 
-let xs$3 = Array_data_util.randomRange(40, 120);
+let cc = Belt_MutableSetInt.union(aa$2, bb$2);
 
-let bb$2 = {
-  data: Belt_internalSetInt.fromArray(xs$3)
-};
+b("File \"bs_mutable_set_test.res\", line 120, characters 8-15", Belt_MutableSetInt.eq(cc, Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 120))));
 
-let cc = Belt_MutableSetInt.union(aa$2, bb$2);
+b("File \"bs_mutable_set_test.res\", line 123, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.union(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 40))));
+
+let dd = Belt_MutableSetInt.intersect(aa$2, bb$2);
+
+b("File \"bs_mutable_set_test.res\", line 127, characters 8-15", Belt_MutableSetInt.eq(dd, Belt_MutableSetInt.fromArray(Array_data_util.randomRange(40, 100))));
 
-let xs$4 = Array_data_util.randomRange(0, 120);
+b("File \"bs_mutable_set_test.res\", line 129, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.make()));
 
-b("File \"bs_mutable_set_test.res\", line 120, characters 8-15", Belt_MutableSetInt.eq(cc, {
-  data: Belt_internalSetInt.fromArray(xs$4)
-}));
+b("File \"bs_mutable_set_test.res\", line 136, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))), Belt_MutableSetInt.make()));
 
-let xs$5 = Array_data_util.randomRange(0, 20);
+b("File \"bs_mutable_set_test.res\", line 142, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray([
+  1,
+  3,
+  4,
+  5,
+  7,
+  9
+]), Belt_MutableSetInt.fromArray([
+  2,
+  4,
+  5,
+  6,
+  8,
+  10
+])), Belt_MutableSetInt.fromArray([
+  4,
+  5
+])));
 
-let xs$6 = Array_data_util.randomRange(21, 40);
+b("File \"bs_mutable_set_test.res\", line 143, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(aa$2, bb$2), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 39))));
 
-let xs$7 = Array_data_util.randomRange(0, 40);
+b("File \"bs_mutable_set_test.res\", line 144, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(bb$2, aa$2), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(101, 120))));
 
-b("File \"bs_mutable_set_test.res\", line 123, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.union({
-  data: Belt_internalSetInt.fromArray(xs$5)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$6)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$7)
-}));
+b("File \"bs_mutable_set_test.res\", line 146, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))));
 
-let dd = Belt_MutableSetInt.intersect(aa$2, bb$2);
+b("File \"bs_mutable_set_test.res\", line 153, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))));
 
-let xs$8 = Array_data_util.randomRange(40, 100);
+b("File \"bs_mutable_set_test.res\", line 161, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, -1))));
 
-b("File \"bs_mutable_set_test.res\", line 127, characters 8-15", Belt_MutableSetInt.eq(dd, {
-  data: Belt_internalSetInt.fromArray(xs$8)
-}));
-
-let xs$9 = Array_data_util.randomRange(0, 20);
-
-let xs$10 = Array_data_util.randomRange(21, 40);
-
-b("File \"bs_mutable_set_test.res\", line 129, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray(xs$9)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$10)
-}), {
-  data: undefined
-}));
-
-let xs$11 = Array_data_util.randomRange(21, 40);
-
-let xs$12 = Array_data_util.randomRange(0, 20);
-
-b("File \"bs_mutable_set_test.res\", line 136, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray(xs$11)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$12)
-}), {
-  data: undefined
-}));
-
-b("File \"bs_mutable_set_test.res\", line 142, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray([
-    1,
-    3,
-    4,
-    5,
-    7,
-    9
-  ])
-}, {
-  data: Belt_internalSetInt.fromArray([
-    2,
-    4,
-    5,
-    6,
-    8,
-    10
-  ])
-}), {
-  data: Belt_internalSetInt.fromArray([
-    4,
-    5
-  ])
-}));
-
-let xs$13 = Array_data_util.randomRange(0, 39);
-
-b("File \"bs_mutable_set_test.res\", line 143, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(aa$2, bb$2), {
-  data: Belt_internalSetInt.fromArray(xs$13)
-}));
-
-let xs$14 = Array_data_util.randomRange(101, 120);
-
-b("File \"bs_mutable_set_test.res\", line 144, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(bb$2, aa$2), {
-  data: Belt_internalSetInt.fromArray(xs$14)
-}));
-
-let xs$15 = Array_data_util.randomRange(21, 40);
-
-let xs$16 = Array_data_util.randomRange(0, 20);
-
-let xs$17 = Array_data_util.randomRange(21, 40);
-
-b("File \"bs_mutable_set_test.res\", line 146, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$15)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$16)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$17)
-}));
-
-let xs$18 = Array_data_util.randomRange(0, 20);
-
-let xs$19 = Array_data_util.randomRange(21, 40);
-
-let xs$20 = Array_data_util.randomRange(0, 20);
-
-b("File \"bs_mutable_set_test.res\", line 153, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$18)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$19)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$20)
-}));
-
-let xs$21 = Array_data_util.randomRange(0, 20);
-
-let xs$22 = Array_data_util.randomRange(0, 40);
-
-let xs$23 = Array_data_util.randomRange(0, -1);
-
-b("File \"bs_mutable_set_test.res\", line 161, characters 8-15", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$21)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$22)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$23)
-}));
-
-let xs$24 = Array_data_util.randomRange(0, 1000);
-
-let a0 = {
-  data: Belt_internalSetInt.fromArray(xs$24)
-};
+let a0 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 1000));
 
 let a1 = Belt_MutableSetInt.keep(a0, x => x % 2 === 0);
 
@@ -389,41 +275,35 @@ Belt_List.forEach({
       }
     }
   }
-}, x => Belt_internalAVLset.checkInvariantInternal(x.data));
+}, Belt_MutableSetInt.checkInvariantInternal);
 
-let v$1 = {
-  data: undefined
-};
+let v$1 = Belt_MutableSetInt.make();
 
 for (let i$2 = 0; i$2 <= 100000; ++i$2) {
   Belt_MutableSetInt.add(v$1, i$2);
 }
 
-Belt_internalAVLset.checkInvariantInternal(v$1.data);
+Belt_MutableSetInt.checkInvariantInternal(v$1);
 
-b("File \"bs_mutable_set_test.res\", line 188, characters 10-17", Belt_Range.every(0, 100000, i => Belt_internalSetInt.has(v$1.data, i)));
+b("File \"bs_mutable_set_test.res\", line 188, characters 10-17", Belt_Range.every(0, 100000, i => Belt_MutableSetInt.has(v$1, i)));
 
-eq("File \"bs_mutable_set_test.res\", line 189, characters 5-12", Belt_internalAVLset.size(v$1.data), 100001);
+eq("File \"bs_mutable_set_test.res\", line 189, characters 5-12", Belt_MutableSetInt.size(v$1), 100001);
 
 let u$1 = Belt_Array.concat(Array_data_util.randomRange(30, 100), Array_data_util.randomRange(40, 120));
 
-let v$2 = {
-  data: undefined
-};
+let v$2 = Belt_MutableSetInt.make();
 
 Belt_MutableSetInt.mergeMany(v$2, u$1);
 
-eq("File \"bs_mutable_set_test.res\", line 196, characters 5-12", Belt_internalAVLset.size(v$2.data), 91);
+eq("File \"bs_mutable_set_test.res\", line 196, characters 5-12", Belt_MutableSetInt.size(v$2), 91);
 
-eq("File \"bs_mutable_set_test.res\", line 197, characters 5-12", Belt_internalAVLset.toArray(v$2.data), Array_data_util.range(30, 120));
+eq("File \"bs_mutable_set_test.res\", line 197, characters 5-12", Belt_MutableSetInt.toArray(v$2), Array_data_util.range(30, 120));
 
 let u$2 = Belt_Array.concat(Array_data_util.randomRange(0, 100000), Array_data_util.randomRange(0, 100));
 
-let v$3 = {
-  data: Belt_internalSetInt.fromArray(u$2)
-};
+let v$3 = Belt_MutableSetInt.fromArray(u$2);
 
-eq("File \"bs_mutable_set_test.res\", line 203, characters 5-12", Belt_internalAVLset.size(v$3.data), 100001);
+eq("File \"bs_mutable_set_test.res\", line 203, characters 5-12", Belt_MutableSetInt.size(v$3), 100001);
 
 let u$3 = Array_data_util.randomRange(50000, 80000);
 
@@ -431,7 +311,7 @@ for (let i$3 = 0, i_finish$1 = u$3.length; i$3 < i_finish$1; ++i$3) {
   Belt_MutableSetInt.remove(v$3, i$3);
 }
 
-eq("File \"bs_mutable_set_test.res\", line 210, characters 5-12", Belt_internalAVLset.size(v$3.data), 70000);
+eq("File \"bs_mutable_set_test.res\", line 210, characters 5-12", Belt_MutableSetInt.size(v$3), 70000);
 
 let vv = Array_data_util.randomRange(0, 100000);
 
@@ -439,27 +319,23 @@ for (let i$4 = 0, i_finish$2 = vv.length; i$4 < i_finish$2; ++i$4) {
   Belt_MutableSetInt.remove(v$3, Primitive_array.get(vv, i$4));
 }
 
-eq("File \"bs_mutable_set_test.res\", line 216, characters 5-12", Belt_internalAVLset.size(v$3.data), 0);
+eq("File \"bs_mutable_set_test.res\", line 216, characters 5-12", Belt_MutableSetInt.size(v$3), 0);
 
 b("File \"bs_mutable_set_test.res\", line 217, characters 4-11", Belt_MutableSetInt.isEmpty(v$3));
 
-let xs$25 = Belt_Array.makeBy(30, i => i);
-
-let v$4 = {
-  data: Belt_internalSetInt.fromArray(xs$25)
-};
+let v$4 = Belt_MutableSetInt.fromArray(Belt_Array.makeBy(30, i => i));
 
 Belt_MutableSetInt.remove(v$4, 30);
 
 Belt_MutableSetInt.remove(v$4, 29);
 
-b("File \"bs_mutable_set_test.res\", line 224, characters 4-11", 28 === Belt_internalAVLset.maxUndefined(v$4.data));
+b("File \"bs_mutable_set_test.res\", line 224, characters 4-11", 28 === Belt_MutableSetInt.maxUndefined(v$4));
 
 Belt_MutableSetInt.remove(v$4, 0);
 
-b("File \"bs_mutable_set_test.res\", line 226, characters 4-11", 1 === Belt_internalAVLset.minUndefined(v$4.data));
+b("File \"bs_mutable_set_test.res\", line 226, characters 4-11", 1 === Belt_MutableSetInt.minUndefined(v$4));
 
-eq("File \"bs_mutable_set_test.res\", line 227, characters 5-12", Belt_internalAVLset.size(v$4.data), 28);
+eq("File \"bs_mutable_set_test.res\", line 227, characters 5-12", Belt_MutableSetInt.size(v$4), 28);
 
 let vv$1 = Array_data_util.randomRange(1, 28);
 
@@ -467,14 +343,12 @@ for (let i$5 = 0, i_finish$3 = vv$1.length; i$5 < i_finish$3; ++i$5) {
   Belt_MutableSetInt.remove(v$4, Primitive_array.get(vv$1, i$5));
 }
 
-eq("File \"bs_mutable_set_test.res\", line 232, characters 5-12", Belt_internalAVLset.size(v$4.data), 0);
+eq("File \"bs_mutable_set_test.res\", line 232, characters 5-12", Belt_MutableSetInt.size(v$4), 0);
 
 function id(loc, x) {
-  let u = {
-    data: Belt_internalAVLset.fromSortedArrayUnsafe(x)
-  };
-  Belt_internalAVLset.checkInvariantInternal(u.data);
-  b(loc, Belt_Array.every2(Belt_internalAVLset.toArray(u.data), x, (prim0, prim1) => prim0 === prim1));
+  let u = Belt_MutableSetInt.fromSortedArrayUnsafe(x);
+  Belt_MutableSetInt.checkInvariantInternal(u);
+  b(loc, Belt_Array.every2(Belt_MutableSetInt.toArray(u), x, (prim0, prim1) => prim0 === prim1));
 }
 
 id("File \"bs_mutable_set_test.res\", line 242, characters 5-12", []);
@@ -560,11 +434,7 @@ id("File \"bs_mutable_set_test.res\", line 252, characters 5-12", [
 
 id("File \"bs_mutable_set_test.res\", line 253, characters 5-12", Array_data_util.range(0, 1000));
 
-let xs$26 = Array_data_util.randomRange(0, 1000);
-
-let v$5 = {
-  data: Belt_internalSetInt.fromArray(xs$26)
-};
+let v$5 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 1000));
 
 let copyV = Belt_MutableSetInt.keep(v$5, x => x % 8 === 0);
 
@@ -576,204 +446,82 @@ for (let i$6 = 0; i$6 <= 200; ++i$6) {
   Belt_MutableSetInt.remove(v$5, i$6);
 }
 
-eq("File \"bs_mutable_set_test.res\", line 264, characters 5-12", Belt_internalAVLset.size(copyV.data), 126);
+eq("File \"bs_mutable_set_test.res\", line 264, characters 5-12", Belt_MutableSetInt.size(copyV), 126);
 
-eq("File \"bs_mutable_set_test.res\", line 265, characters 5-12", Belt_internalAVLset.toArray(copyV.data), Belt_Array.makeBy(126, i => (i << 3)));
+eq("File \"bs_mutable_set_test.res\", line 265, characters 5-12", Belt_MutableSetInt.toArray(copyV), Belt_Array.makeBy(126, i => (i << 3)));
 
-eq("File \"bs_mutable_set_test.res\", line 266, characters 5-12", Belt_internalAVLset.size(v$5.data), 800);
+eq("File \"bs_mutable_set_test.res\", line 266, characters 5-12", Belt_MutableSetInt.size(v$5), 800);
 
 b("File \"bs_mutable_set_test.res\", line 267, characters 4-11", Belt_MutableSetInt.eq(copyV, match$5[0]));
 
 b("File \"bs_mutable_set_test.res\", line 268, characters 4-11", Belt_MutableSetInt.eq(cc$1, match$5[1]));
 
-let xs$27 = Array_data_util.randomRange(0, 1000);
-
-let v$6 = {
-  data: Belt_internalSetInt.fromArray(xs$27)
-};
+let v$6 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 1000));
 
 let match$6 = Belt_MutableSetInt.split(v$6, 400);
 
 let match$7 = match$6[0];
 
-let xs$28 = Array_data_util.randomRange(0, 399);
-
-b("File \"bs_mutable_set_test.res\", line 274, characters 4-11", Belt_MutableSetInt.eq(match$7[0], {
-  data: Belt_internalSetInt.fromArray(xs$28)
-}));
-
-let xs$29 = Array_data_util.randomRange(401, 1000);
+b("File \"bs_mutable_set_test.res\", line 274, characters 4-11", Belt_MutableSetInt.eq(match$7[0], Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 399))));
 
-b("File \"bs_mutable_set_test.res\", line 275, characters 4-11", Belt_MutableSetInt.eq(match$7[1], {
-  data: Belt_internalSetInt.fromArray(xs$29)
-}));
+b("File \"bs_mutable_set_test.res\", line 275, characters 4-11", Belt_MutableSetInt.eq(match$7[1], Belt_MutableSetInt.fromArray(Array_data_util.randomRange(401, 1000))));
 
-let xs$30 = Belt_Array.map(Array_data_util.randomRange(0, 1000), x => (x << 1));
-
-let d = {
-  data: Belt_internalSetInt.fromArray(xs$30)
-};
+let d = Belt_MutableSetInt.fromArray(Belt_Array.map(Array_data_util.randomRange(0, 1000), x => (x << 1)));
 
 let match$8 = Belt_MutableSetInt.split(d, 1001);
 
 let match$9 = match$8[0];
 
-let xs$31 = Belt_Array.makeBy(501, x => (x << 1));
+b("File \"bs_mutable_set_test.res\", line 278, characters 4-11", Belt_MutableSetInt.eq(match$9[0], Belt_MutableSetInt.fromArray(Belt_Array.makeBy(501, x => (x << 1)))));
 
-b("File \"bs_mutable_set_test.res\", line 278, characters 4-11", Belt_MutableSetInt.eq(match$9[0], {
-  data: Belt_internalSetInt.fromArray(xs$31)
-}));
+b("File \"bs_mutable_set_test.res\", line 279, characters 4-11", Belt_MutableSetInt.eq(match$9[1], Belt_MutableSetInt.fromArray(Belt_Array.makeBy(500, x => 1002 + (x << 1) | 0))));
 
-let xs$32 = Belt_Array.makeBy(500, x => 1002 + (x << 1) | 0);
+let aa$3 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 100));
 
-b("File \"bs_mutable_set_test.res\", line 279, characters 4-11", Belt_MutableSetInt.eq(match$9[1], {
-  data: Belt_internalSetInt.fromArray(xs$32)
-}));
+let bb$3 = Belt_MutableSetInt.fromArray(Array_data_util.randomRange(40, 120));
 
-let xs$33 = Array_data_util.randomRange(0, 100);
-
-let aa$3 = {
-  data: Belt_internalSetInt.fromArray(xs$33)
-};
+let cc$2 = Belt_MutableSetInt.union(aa$3, bb$3);
 
-let xs$34 = Array_data_util.randomRange(40, 120);
+b("File \"bs_mutable_set_test.res\", line 289, characters 4-11", Belt_MutableSetInt.eq(cc$2, Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 120))));
 
-let bb$3 = {
-  data: Belt_internalSetInt.fromArray(xs$34)
-};
+b("File \"bs_mutable_set_test.res\", line 292, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.union(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 40))));
 
-let cc$2 = Belt_MutableSetInt.union(aa$3, bb$3);
+let dd$1 = Belt_MutableSetInt.intersect(aa$3, bb$3);
 
-let xs$35 = Array_data_util.randomRange(0, 120);
+b("File \"bs_mutable_set_test.res\", line 296, characters 4-11", Belt_MutableSetInt.eq(dd$1, Belt_MutableSetInt.fromArray(Array_data_util.randomRange(40, 100))));
 
-b("File \"bs_mutable_set_test.res\", line 289, characters 4-11", Belt_MutableSetInt.eq(cc$2, {
-  data: Belt_internalSetInt.fromArray(xs$35)
-}));
+b("File \"bs_mutable_set_test.res\", line 298, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.make()));
 
-let xs$36 = Array_data_util.randomRange(0, 20);
+b("File \"bs_mutable_set_test.res\", line 302, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))), Belt_MutableSetInt.make()));
 
-let xs$37 = Array_data_util.randomRange(21, 40);
+b("File \"bs_mutable_set_test.res\", line 305, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect(Belt_MutableSetInt.fromArray([
+  1,
+  3,
+  4,
+  5,
+  7,
+  9
+]), Belt_MutableSetInt.fromArray([
+  2,
+  4,
+  5,
+  6,
+  8,
+  10
+])), Belt_MutableSetInt.fromArray([
+  4,
+  5
+])));
 
-let xs$38 = Array_data_util.randomRange(0, 40);
+b("File \"bs_mutable_set_test.res\", line 306, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(aa$3, bb$3), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 39))));
 
-b("File \"bs_mutable_set_test.res\", line 292, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.union({
-  data: Belt_internalSetInt.fromArray(xs$36)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$37)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$38)
-}));
+b("File \"bs_mutable_set_test.res\", line 307, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(bb$3, aa$3), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(101, 120))));
 
-let dd$1 = Belt_MutableSetInt.intersect(aa$3, bb$3);
+b("File \"bs_mutable_set_test.res\", line 309, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))));
 
-let xs$39 = Array_data_util.randomRange(40, 100);
+b("File \"bs_mutable_set_test.res\", line 316, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(21, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20))));
 
-b("File \"bs_mutable_set_test.res\", line 296, characters 4-11", Belt_MutableSetInt.eq(dd$1, {
-  data: Belt_internalSetInt.fromArray(xs$39)
-}));
-
-let xs$40 = Array_data_util.randomRange(0, 20);
-
-let xs$41 = Array_data_util.randomRange(21, 40);
-
-b("File \"bs_mutable_set_test.res\", line 298, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray(xs$40)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$41)
-}), {
-  data: undefined
-}));
-
-let xs$42 = Array_data_util.randomRange(21, 40);
-
-let xs$43 = Array_data_util.randomRange(0, 20);
-
-b("File \"bs_mutable_set_test.res\", line 302, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray(xs$42)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$43)
-}), {
-  data: undefined
-}));
-
-b("File \"bs_mutable_set_test.res\", line 305, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.intersect({
-  data: Belt_internalSetInt.fromArray([
-    1,
-    3,
-    4,
-    5,
-    7,
-    9
-  ])
-}, {
-  data: Belt_internalSetInt.fromArray([
-    2,
-    4,
-    5,
-    6,
-    8,
-    10
-  ])
-}), {
-  data: Belt_internalSetInt.fromArray([
-    4,
-    5
-  ])
-}));
-
-let xs$44 = Array_data_util.randomRange(0, 39);
-
-b("File \"bs_mutable_set_test.res\", line 306, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(aa$3, bb$3), {
-  data: Belt_internalSetInt.fromArray(xs$44)
-}));
-
-let xs$45 = Array_data_util.randomRange(101, 120);
-
-b("File \"bs_mutable_set_test.res\", line 307, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(bb$3, aa$3), {
-  data: Belt_internalSetInt.fromArray(xs$45)
-}));
-
-let xs$46 = Array_data_util.randomRange(21, 40);
-
-let xs$47 = Array_data_util.randomRange(0, 20);
-
-let xs$48 = Array_data_util.randomRange(21, 40);
-
-b("File \"bs_mutable_set_test.res\", line 309, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$46)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$47)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$48)
-}));
-
-let xs$49 = Array_data_util.randomRange(0, 20);
-
-let xs$50 = Array_data_util.randomRange(21, 40);
-
-let xs$51 = Array_data_util.randomRange(0, 20);
-
-b("File \"bs_mutable_set_test.res\", line 316, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$49)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$50)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$51)
-}));
-
-let xs$52 = Array_data_util.randomRange(0, 20);
-
-let xs$53 = Array_data_util.randomRange(0, 40);
-
-let xs$54 = Array_data_util.randomRange(0, -1);
-
-b("File \"bs_mutable_set_test.res\", line 324, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff({
-  data: Belt_internalSetInt.fromArray(xs$52)
-}, {
-  data: Belt_internalSetInt.fromArray(xs$53)
-}), {
-  data: Belt_internalSetInt.fromArray(xs$54)
-}));
+b("File \"bs_mutable_set_test.res\", line 324, characters 4-11", Belt_MutableSetInt.eq(Belt_MutableSetInt.diff(Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 20)), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, 40))), Belt_MutableSetInt.fromArray(Array_data_util.randomRange(0, -1))));
 
 Mt.from_pair_suites("Bs_mutable_set_test", suites.contents);
 
diff --git a/tests/tests/src/bs_poly_map_test.js b/tests/tests/src/bs_poly_map_test.js
index 3cbeb6dc00..51db7fab94 100644
--- a/tests/tests/src/bs_poly_map_test.js
+++ b/tests/tests/src/bs_poly_map_test.js
@@ -2,10 +2,10 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_Map = require("rescript/lib/js/belt_Map.js");
 let Belt_Set = require("rescript/lib/js/belt_Set.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
-let Belt_MapDict = require("rescript/lib/js/belt_MapDict.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 let Array_data_util = require("./array_data_util.js");
 let Primitive_option = require("rescript/lib/js/primitive_option.js");
@@ -26,9 +26,7 @@ function b(loc, v) {
   Mt.bool_suites(test_id, suites, loc, v);
 }
 
-let Icmp = {
-  cmp: Primitive_int.compare
-};
+let Icmp = Belt_Id.comparable(Primitive_int.compare);
 
 function mapOfArray(x) {
   return Belt_Map.fromArray(x, Icmp);
@@ -39,40 +37,34 @@ function setOfArray(x) {
 }
 
 function emptyMap() {
-  return {
-    cmp: Icmp.cmp,
-    data: undefined
-  };
+  return Belt_Map.make(Icmp);
 }
 
 function mergeInter(s1, s2) {
-  let m = Belt_Map.merge(s1, s2, (k, v1, v2) => {
+  return Belt_Set.fromArray(Belt_Map.keysToArray(Belt_Map.merge(s1, s2, (k, v1, v2) => {
     if (v1 !== undefined && v2 !== undefined) {
       return Primitive_option.some(undefined);
     }
     
-  });
-  return Belt_Set.fromArray(Belt_MapDict.keysToArray(m.data), Icmp);
+  })), Icmp);
 }
 
 function mergeUnion(s1, s2) {
-  let m = Belt_Map.merge(s1, s2, (k, v1, v2) => {
+  return Belt_Set.fromArray(Belt_Map.keysToArray(Belt_Map.merge(s1, s2, (k, v1, v2) => {
     if (v1 !== undefined || v2 !== undefined) {
       return Primitive_option.some(undefined);
     }
     
-  });
-  return Belt_Set.fromArray(Belt_MapDict.keysToArray(m.data), Icmp);
+  })), Icmp);
 }
 
 function mergeDiff(s1, s2) {
-  let m = Belt_Map.merge(s1, s2, (k, v1, v2) => {
+  return Belt_Set.fromArray(Belt_Map.keysToArray(Belt_Map.merge(s1, s2, (k, v1, v2) => {
     if (v1 !== undefined && v2 === undefined) {
       return Primitive_option.some(undefined);
     }
     
-  });
-  return Belt_Set.fromArray(Belt_MapDict.keysToArray(m.data), Icmp);
+  })), Icmp);
 }
 
 function randomRange(i, j) {
@@ -149,14 +141,14 @@ let a7 = Belt_Map.removeMany(a0, [
   6
 ]);
 
-eq("File \"bs_poly_map_test.res\", line 99, characters 5-12", Belt_MapDict.keysToArray(a7.data), [
+eq("File \"bs_poly_map_test.res\", line 99, characters 5-12", Belt_Map.keysToArray(a7), [
   9,
   10
 ]);
 
 let a8 = Belt_Map.removeMany(a7, Array_data_util.randomRange(0, 100));
 
-b("File \"bs_poly_map_test.res\", line 101, characters 4-11", Belt_MapDict.isEmpty(a8.data));
+b("File \"bs_poly_map_test.res\", line 101, characters 4-11", Belt_Map.isEmpty(a8));
 
 let u0$1 = Belt_Map.fromArray(randomRange(0, 100), Icmp);
 
@@ -176,12 +168,7 @@ function acc(m, is) {
   }));
 }
 
-let m_cmp = Icmp.cmp;
-
-let m = {
-  cmp: m_cmp,
-  data: undefined
-};
+let m = Belt_Map.make(Icmp);
 
 let m1 = acc(m, Belt_Array.concat(Array_data_util.randomRange(0, 20), Array_data_util.randomRange(10, 30)));
 
@@ -190,12 +177,7 @@ b("File \"bs_poly_map_test.res\", line 125, characters 4-11", Belt_Map.eq(m1, Be
   i >= 10 && i <= 20 ? 2 : 1
 ]), Icmp), (x, y) => x === y));
 
-let v0_cmp = Icmp.cmp;
-
-let v0 = {
-  cmp: v0_cmp,
-  data: undefined
-};
+let v0 = Belt_Map.make(Icmp);
 
 let v1 = Belt_Map.mergeMany(v0, Belt_Array.map(Array_data_util.randomRange(0, 10000), x => [
   x,
@@ -239,25 +221,15 @@ let match$4 = Belt_Map.get(v4, -10);
 
 b("File \"bs_poly_map_test.res\", line 174, characters 4-11", match$4 !== undefined ? match$4 === 0 : false);
 
-let map = Belt_Map.remove({
-  cmp: Icmp.cmp,
-  data: undefined
-}, 0);
-
-b("File \"bs_poly_map_test.res\", line 180, characters 4-11", Belt_MapDict.isEmpty(map.data));
-
-let map$1 = Belt_Map.removeMany({
-  cmp: Icmp.cmp,
-  data: undefined
-}, [0]);
+b("File \"bs_poly_map_test.res\", line 180, characters 4-11", Belt_Map.isEmpty(Belt_Map.remove(Belt_Map.make(Icmp), 0)));
 
-b("File \"bs_poly_map_test.res\", line 181, characters 4-11", Belt_MapDict.isEmpty(map$1.data));
+b("File \"bs_poly_map_test.res\", line 181, characters 4-11", Belt_Map.isEmpty(Belt_Map.removeMany(Belt_Map.make(Icmp), [0])));
 
 b("File \"bs_poly_map_test.res\", line 183, characters 4-11", pres !== undefined ? pres === 5000 : false);
 
-b("File \"bs_poly_map_test.res\", line 189, characters 4-11", Belt_Array.eq(Belt_MapDict.keysToArray(match$1[0].data), Belt_Array.makeBy(5000, i => i), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_map_test.res\", line 189, characters 4-11", Belt_Array.eq(Belt_Map.keysToArray(match$1[0]), Belt_Array.makeBy(5000, i => i), (prim0, prim1) => prim0 === prim1));
 
-b("File \"bs_poly_map_test.res\", line 190, characters 4-11", Belt_Array.eq(Belt_MapDict.keysToArray(match$1[1].data), Belt_Array.makeBy(5000, i => 5001 + i | 0), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_map_test.res\", line 190, characters 4-11", Belt_Array.eq(Belt_Map.keysToArray(match$1[1]), Belt_Array.makeBy(5000, i => 5001 + i | 0), (prim0, prim1) => prim0 === prim1));
 
 let v7 = Belt_Map.remove(v3, 5000);
 
@@ -267,9 +239,9 @@ let match$6 = match$5[0];
 
 b("File \"bs_poly_map_test.res\", line 195, characters 4-11", match$5[1] === undefined);
 
-b("File \"bs_poly_map_test.res\", line 201, characters 4-11", Belt_Array.eq(Belt_MapDict.keysToArray(match$6[0].data), Belt_Array.makeBy(5000, i => i), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_map_test.res\", line 201, characters 4-11", Belt_Array.eq(Belt_Map.keysToArray(match$6[0]), Belt_Array.makeBy(5000, i => i), (prim0, prim1) => prim0 === prim1));
 
-b("File \"bs_poly_map_test.res\", line 202, characters 4-11", Belt_Array.eq(Belt_MapDict.keysToArray(match$6[1].data), Belt_Array.makeBy(5000, i => 5001 + i | 0), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_map_test.res\", line 202, characters 4-11", Belt_Array.eq(Belt_Map.keysToArray(match$6[1]), Belt_Array.makeBy(5000, i => 5001 + i | 0), (prim0, prim1) => prim0 === prim1));
 
 Mt.from_pair_suites("Bs_poly_map_test", suites.contents);
 
@@ -298,4 +270,4 @@ exports.mergeUnion = mergeUnion;
 exports.mergeDiff = mergeDiff;
 exports.randomRange = randomRange;
 exports.acc = acc;
-/* u0 Not a pure module */
+/* Icmp Not a pure module */
diff --git a/tests/tests/src/bs_poly_mutable_map_test.js b/tests/tests/src/bs_poly_mutable_map_test.js
index a81d4cbb4a..5b6ab9b546 100644
--- a/tests/tests/src/bs_poly_mutable_map_test.js
+++ b/tests/tests/src/bs_poly_mutable_map_test.js
@@ -2,12 +2,12 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_Set = require("rescript/lib/js/belt_Set.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 let Array_data_util = require("./array_data_util.js");
 let Belt_MutableMap = require("rescript/lib/js/belt_MutableMap.js");
-let Belt_internalAVLtree = require("rescript/lib/js/belt_internalAVLtree.js");
 
 let suites = {
   contents: /* [] */0
@@ -25,9 +25,7 @@ function b(loc, v) {
   Mt.bool_suites(test_id, suites, loc, v);
 }
 
-let Icmp = {
-  cmp: Primitive_int.compare
-};
+let Icmp = Belt_Id.comparable(Primitive_int.compare);
 
 function f(x) {
   return Belt_MutableMap.fromArray(x, Icmp);
@@ -64,7 +62,7 @@ Belt_MutableMap.removeMany(a0, [
   6
 ]);
 
-eq("File \"bs_poly_mutable_map_test.res\", line 29, characters 5-12", Belt_internalAVLtree.keysToArray(a0.data), [
+eq("File \"bs_poly_mutable_map_test.res\", line 29, characters 5-12", Belt_MutableMap.keysToArray(a0), [
   9,
   10
 ]);
@@ -81,7 +79,7 @@ Belt_MutableMap.removeMany(a0$1, Belt_Array.map(randomRange(0, 1998), prim => pr
 
 Belt_MutableMap.removeMany(a0$1, Belt_Array.map(randomRange(2002, 11000), prim => prim[0]));
 
-eq("File \"bs_poly_mutable_map_test.res\", line 39, characters 5-12", Belt_internalAVLtree.toArray(a0$1.data), [
+eq("File \"bs_poly_mutable_map_test.res\", line 39, characters 5-12", Belt_MutableMap.toArray(a0$1), [
   [
     1999,
     1999
@@ -118,4 +116,4 @@ exports.I = I;
 exports.f = f;
 exports.ff = ff;
 exports.randomRange = randomRange;
-/* a0 Not a pure module */
+/* Icmp Not a pure module */
diff --git a/tests/tests/src/bs_poly_mutable_set_test.js b/tests/tests/src/bs_poly_mutable_set_test.js
index 99f79dde25..5810c1cdfc 100644
--- a/tests/tests/src/bs_poly_mutable_set_test.js
+++ b/tests/tests/src/bs_poly_mutable_set_test.js
@@ -2,12 +2,12 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_List = require("rescript/lib/js/belt_List.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 let Array_data_util = require("./array_data_util.js");
 let Belt_MutableSet = require("rescript/lib/js/belt_MutableSet.js");
-let Belt_internalAVLset = require("rescript/lib/js/belt_internalAVLset.js");
 
 let suites = {
   contents: /* [] */0
@@ -25,19 +25,14 @@ function b(loc, x) {
   Mt.bool_suites(test_id, suites, loc, x);
 }
 
-let IntCmp = {
-  cmp: Primitive_int.compare
-};
+let IntCmp = Belt_Id.comparable(Primitive_int.compare);
 
 function fromArray(none) {
   return Belt_MutableSet.fromArray(none, IntCmp);
 }
 
 function empty() {
-  return {
-    cmp: IntCmp.cmp,
-    data: undefined
-  };
+  return Belt_MutableSet.make(IntCmp);
 }
 
 let u = Belt_MutableSet.fromArray(Array_data_util.range(0, 30), IntCmp);
@@ -50,13 +45,13 @@ b("File \"bs_poly_mutable_set_test.res\", line 18, characters 4-11", Belt_Mutabl
 
 b("File \"bs_poly_mutable_set_test.res\", line 19, characters 4-11", Belt_MutableSet.removeCheck(u, 20));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 20, characters 5-12", Belt_internalAVLset.size(u.data), 28);
+eq("File \"bs_poly_mutable_set_test.res\", line 20, characters 5-12", Belt_MutableSet.size(u), 28);
 
 let r = Array_data_util.randomRange(0, 30);
 
-b("File \"bs_poly_mutable_set_test.res\", line 22, characters 4-11", 29 === Belt_internalAVLset.maxUndefined(u.data));
+b("File \"bs_poly_mutable_set_test.res\", line 22, characters 4-11", 29 === Belt_MutableSet.maxUndefined(u));
 
-b("File \"bs_poly_mutable_set_test.res\", line 23, characters 4-11", 1 === Belt_internalAVLset.minUndefined(u.data));
+b("File \"bs_poly_mutable_set_test.res\", line 23, characters 4-11", 1 === Belt_MutableSet.minUndefined(u));
 
 Belt_MutableSet.add(u, 3);
 
@@ -74,7 +69,7 @@ Belt_MutableSet.add(u, 2);
 
 Belt_MutableSet.add(u, 0);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 33, characters 5-12", Belt_internalAVLset.size(u.data), 3);
+eq("File \"bs_poly_mutable_set_test.res\", line 33, characters 5-12", Belt_MutableSet.size(u), 3);
 
 b("File \"bs_poly_mutable_set_test.res\", line 34, characters 4-11", !Belt_MutableSet.isEmpty(u));
 
@@ -88,27 +83,27 @@ Belt_MutableSet.mergeMany(u, Array_data_util.randomRange(0, 20000));
 
 Belt_MutableSet.mergeMany(u, Array_data_util.randomRange(0, 200));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 41, characters 5-12", Belt_internalAVLset.size(u.data), 20001);
+eq("File \"bs_poly_mutable_set_test.res\", line 41, characters 5-12", Belt_MutableSet.size(u), 20001);
 
 Belt_MutableSet.removeMany(u, Array_data_util.randomRange(0, 200));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 43, characters 5-12", Belt_internalAVLset.size(u.data), 19800);
+eq("File \"bs_poly_mutable_set_test.res\", line 43, characters 5-12", Belt_MutableSet.size(u), 19800);
 
 Belt_MutableSet.removeMany(u, Array_data_util.randomRange(0, 1000));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 45, characters 5-12", Belt_internalAVLset.size(u.data), 19000);
+eq("File \"bs_poly_mutable_set_test.res\", line 45, characters 5-12", Belt_MutableSet.size(u), 19000);
 
 Belt_MutableSet.removeMany(u, Array_data_util.randomRange(0, 1000));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 47, characters 5-12", Belt_internalAVLset.size(u.data), 19000);
+eq("File \"bs_poly_mutable_set_test.res\", line 47, characters 5-12", Belt_MutableSet.size(u), 19000);
 
 Belt_MutableSet.removeMany(u, Array_data_util.randomRange(1000, 10000));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 49, characters 5-12", Belt_internalAVLset.size(u.data), 10000);
+eq("File \"bs_poly_mutable_set_test.res\", line 49, characters 5-12", Belt_MutableSet.size(u), 10000);
 
 Belt_MutableSet.removeMany(u, Array_data_util.randomRange(10000, 19999));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 51, characters 5-12", Belt_internalAVLset.size(u.data), 1);
+eq("File \"bs_poly_mutable_set_test.res\", line 51, characters 5-12", Belt_MutableSet.size(u), 1);
 
 b("File \"bs_poly_mutable_set_test.res\", line 52, characters 4-11", Belt_MutableSet.has(u, 20000));
 
@@ -130,7 +125,7 @@ let indeedRemoved = Belt_Array.reduce(bs, 0, (acc, x) => {
 
 eq("File \"bs_poly_mutable_set_test.res\", line 67, characters 5-12", indeedRemoved, 500);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 68, characters 5-12", Belt_internalAVLset.size(v.data), 501);
+eq("File \"bs_poly_mutable_set_test.res\", line 68, characters 5-12", Belt_MutableSet.size(v), 501);
 
 let cs = Belt_Array.map(Array_data_util.randomRange(500, 2000), x => Belt_MutableSet.addCheck(v, x));
 
@@ -144,28 +139,25 @@ let indeedAded = Belt_Array.reduce(cs, 0, (acc, x) => {
 
 eq("File \"bs_poly_mutable_set_test.res\", line 77, characters 5-12", indeedAded, 1000);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 78, characters 5-12", Belt_internalAVLset.size(v.data), 1501);
+eq("File \"bs_poly_mutable_set_test.res\", line 78, characters 5-12", Belt_MutableSet.size(v), 1501);
 
-b("File \"bs_poly_mutable_set_test.res\", line 79, characters 4-11", Belt_MutableSet.isEmpty({
-  cmp: IntCmp.cmp,
-  data: undefined
-}));
+b("File \"bs_poly_mutable_set_test.res\", line 79, characters 4-11", Belt_MutableSet.isEmpty(Belt_MutableSet.make(IntCmp)));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 80, characters 5-12", Belt_internalAVLset.minimum(v.data), 500);
+eq("File \"bs_poly_mutable_set_test.res\", line 80, characters 5-12", Belt_MutableSet.minimum(v), 500);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 81, characters 5-12", Belt_internalAVLset.maximum(v.data), 2000);
+eq("File \"bs_poly_mutable_set_test.res\", line 81, characters 5-12", Belt_MutableSet.maximum(v), 2000);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 82, characters 5-12", Belt_internalAVLset.minUndefined(v.data), 500);
+eq("File \"bs_poly_mutable_set_test.res\", line 82, characters 5-12", Belt_MutableSet.minUndefined(v), 500);
 
-eq("File \"bs_poly_mutable_set_test.res\", line 83, characters 5-12", Belt_internalAVLset.maxUndefined(v.data), 2000);
+eq("File \"bs_poly_mutable_set_test.res\", line 83, characters 5-12", Belt_MutableSet.maxUndefined(v), 2000);
 
 eq("File \"bs_poly_mutable_set_test.res\", line 84, characters 5-12", Belt_MutableSet.reduce(v, 0, (x, y) => x + y | 0), 1876250);
 
-b("File \"bs_poly_mutable_set_test.res\", line 85, characters 4-11", Belt_List.eq(Belt_internalAVLset.toList(v.data), Belt_List.makeBy(1501, i => i + 500 | 0), (x, y) => x === y));
+b("File \"bs_poly_mutable_set_test.res\", line 85, characters 4-11", Belt_List.eq(Belt_MutableSet.toList(v), Belt_List.makeBy(1501, i => i + 500 | 0), (x, y) => x === y));
 
-eq("File \"bs_poly_mutable_set_test.res\", line 86, characters 5-12", Belt_internalAVLset.toArray(v.data), Array_data_util.range(500, 2000));
+eq("File \"bs_poly_mutable_set_test.res\", line 86, characters 5-12", Belt_MutableSet.toArray(v), Array_data_util.range(500, 2000));
 
-Belt_internalAVLset.checkInvariantInternal(v.data);
+Belt_MutableSet.checkInvariantInternal(v);
 
 eq("File \"bs_poly_mutable_set_test.res\", line 88, characters 5-12", Belt_MutableSet.get(v, 3), undefined);
 
@@ -181,9 +173,9 @@ let aa = match$1[0];
 
 b("File \"bs_poly_mutable_set_test.res\", line 91, characters 4-11", match[1]);
 
-b("File \"bs_poly_mutable_set_test.res\", line 92, characters 4-11", Belt_Array.eq(Belt_internalAVLset.toArray(aa.data), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_mutable_set_test.res\", line 92, characters 4-11", Belt_Array.eq(Belt_MutableSet.toArray(aa), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
 
-b("File \"bs_poly_mutable_set_test.res\", line 93, characters 4-11", Belt_Array.eq(Belt_internalAVLset.toArray(bb.data), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_mutable_set_test.res\", line 93, characters 4-11", Belt_Array.eq(Belt_MutableSet.toArray(bb), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
 
 b("File \"bs_poly_mutable_set_test.res\", line 94, characters 4-11", Belt_MutableSet.subset(aa, v));
 
@@ -205,9 +197,9 @@ let aa$1 = match$3[0];
 
 b("File \"bs_poly_mutable_set_test.res\", line 100, characters 4-11", !match$2[1]);
 
-b("File \"bs_poly_mutable_set_test.res\", line 101, characters 4-11", Belt_Array.eq(Belt_internalAVLset.toArray(aa$1.data), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_mutable_set_test.res\", line 101, characters 4-11", Belt_Array.eq(Belt_MutableSet.toArray(aa$1), Array_data_util.range(500, 999), (prim0, prim1) => prim0 === prim1));
 
-b("File \"bs_poly_mutable_set_test.res\", line 102, characters 4-11", Belt_Array.eq(Belt_internalAVLset.toArray(bb$1.data), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
+b("File \"bs_poly_mutable_set_test.res\", line 102, characters 4-11", Belt_Array.eq(Belt_MutableSet.toArray(bb$1), Array_data_util.range(1001, 2000), (prim0, prim1) => prim0 === prim1));
 
 b("File \"bs_poly_mutable_set_test.res\", line 103, characters 4-11", Belt_MutableSet.subset(aa$1, v));
 
@@ -229,15 +221,9 @@ let dd = Belt_MutableSet.intersect(aa$2, bb$2);
 
 b("File \"bs_poly_mutable_set_test.res\", line 122, characters 4-11", Belt_MutableSet.eq(dd, Belt_MutableSet.fromArray(Array_data_util.randomRange(40, 100), IntCmp)));
 
-b("File \"bs_poly_mutable_set_test.res\", line 124, characters 4-11", Belt_MutableSet.eq(Belt_MutableSet.intersect(Belt_MutableSet.fromArray(Array_data_util.randomRange(0, 20), IntCmp), Belt_MutableSet.fromArray(Array_data_util.randomRange(21, 40), IntCmp)), {
-  cmp: IntCmp.cmp,
-  data: undefined
-}));
+b("File \"bs_poly_mutable_set_test.res\", line 124, characters 4-11", Belt_MutableSet.eq(Belt_MutableSet.intersect(Belt_MutableSet.fromArray(Array_data_util.randomRange(0, 20), IntCmp), Belt_MutableSet.fromArray(Array_data_util.randomRange(21, 40), IntCmp)), Belt_MutableSet.make(IntCmp)));
 
-b("File \"bs_poly_mutable_set_test.res\", line 128, characters 4-11", Belt_MutableSet.eq(Belt_MutableSet.intersect(Belt_MutableSet.fromArray(Array_data_util.randomRange(21, 40), IntCmp), Belt_MutableSet.fromArray(Array_data_util.randomRange(0, 20), IntCmp)), {
-  cmp: IntCmp.cmp,
-  data: undefined
-}));
+b("File \"bs_poly_mutable_set_test.res\", line 128, characters 4-11", Belt_MutableSet.eq(Belt_MutableSet.intersect(Belt_MutableSet.fromArray(Array_data_util.randomRange(21, 40), IntCmp), Belt_MutableSet.fromArray(Array_data_util.randomRange(0, 20), IntCmp)), Belt_MutableSet.make(IntCmp)));
 
 b("File \"bs_poly_mutable_set_test.res\", line 131, characters 4-11", Belt_MutableSet.eq(Belt_MutableSet.intersect(Belt_MutableSet.fromArray([
   1,
@@ -299,7 +285,7 @@ Belt_List.forEach({
       }
     }
   }
-}, x => Belt_internalAVLset.checkInvariantInternal(x.data));
+}, Belt_MutableSet.checkInvariantInternal);
 
 Mt.from_pair_suites("Bs_poly_mutable_set_test", suites.contents);
 
@@ -331,4 +317,4 @@ exports.empty = empty;
 exports.$plus$plus = $plus$plus;
 exports.f = f;
 exports.$eq$tilde = $eq$tilde;
-/* u Not a pure module */
+/* IntCmp Not a pure module */
diff --git a/tests/tests/src/bs_poly_set_test.js b/tests/tests/src/bs_poly_set_test.js
index 6329f59150..d63957698a 100644
--- a/tests/tests/src/bs_poly_set_test.js
+++ b/tests/tests/src/bs_poly_set_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_Set = require("rescript/lib/js/belt_Set.js");
 let Belt_List = require("rescript/lib/js/belt_List.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
@@ -31,9 +32,7 @@ function t(loc, x) {
   Mt.throw_suites(test_id, suites, loc, x);
 }
 
-let IntCmp = {
-  cmp: Primitive_int.compare
-};
+let IntCmp = Belt_Id.comparable(Primitive_int.compare);
 
 let u0 = Belt_Set.fromArray(Array_data_util.range(0, 30), IntCmp);
 
@@ -85,43 +84,43 @@ b("File \"bs_poly_set_test.res\", line 34, characters 4-11", u0 !== u1);
 
 b("File \"bs_poly_set_test.res\", line 35, characters 4-11", u2 === u1);
 
-eq("File \"bs_poly_set_test.res\", line 36, characters 5-12", Belt_SetDict.size(u4.data), 28);
+eq("File \"bs_poly_set_test.res\", line 36, characters 5-12", Belt_Set.size(u4), 28);
 
-b("File \"bs_poly_set_test.res\", line 37, characters 4-11", 29 === Belt_SetDict.maxUndefined(u4.data));
+b("File \"bs_poly_set_test.res\", line 37, characters 4-11", 29 === Belt_Set.maxUndefined(u4));
 
-b("File \"bs_poly_set_test.res\", line 38, characters 4-11", 1 === Belt_SetDict.minUndefined(u4.data));
+b("File \"bs_poly_set_test.res\", line 38, characters 4-11", 1 === Belt_Set.minUndefined(u4));
 
 b("File \"bs_poly_set_test.res\", line 39, characters 4-11", u4 === u5);
 
-b("File \"bs_poly_set_test.res\", line 40, characters 4-11", Belt_SetDict.isEmpty(u6.data));
+b("File \"bs_poly_set_test.res\", line 40, characters 4-11", Belt_Set.isEmpty(u6));
 
-eq("File \"bs_poly_set_test.res\", line 41, characters 5-12", Belt_SetDict.size(u7.data), 3);
+eq("File \"bs_poly_set_test.res\", line 41, characters 5-12", Belt_Set.size(u7), 3);
 
-b("File \"bs_poly_set_test.res\", line 42, characters 4-11", !Belt_SetDict.isEmpty(u7.data));
+b("File \"bs_poly_set_test.res\", line 42, characters 4-11", !Belt_Set.isEmpty(u7));
 
-b("File \"bs_poly_set_test.res\", line 43, characters 4-11", Belt_SetDict.isEmpty(u8.data));
+b("File \"bs_poly_set_test.res\", line 43, characters 4-11", Belt_Set.isEmpty(u8));
 
 b("File \"bs_poly_set_test.res\", line 46, characters 4-11", Belt_Set.has(u10, 20));
 
 b("File \"bs_poly_set_test.res\", line 47, characters 4-11", Belt_Set.has(u10, 21));
 
-eq("File \"bs_poly_set_test.res\", line 48, characters 5-12", Belt_SetDict.size(u10.data), 20001);
+eq("File \"bs_poly_set_test.res\", line 48, characters 5-12", Belt_Set.size(u10), 20001);
 
-eq("File \"bs_poly_set_test.res\", line 49, characters 5-12", Belt_SetDict.size(u11.data), 19800);
+eq("File \"bs_poly_set_test.res\", line 49, characters 5-12", Belt_Set.size(u11), 19800);
 
-eq("File \"bs_poly_set_test.res\", line 50, characters 5-12", Belt_SetDict.size(u12.data), 19000);
+eq("File \"bs_poly_set_test.res\", line 50, characters 5-12", Belt_Set.size(u12), 19000);
 
-eq("File \"bs_poly_set_test.res\", line 52, characters 5-12", Belt_SetDict.size(u13.data), Belt_SetDict.size(u12.data));
+eq("File \"bs_poly_set_test.res\", line 52, characters 5-12", Belt_Set.size(u13), Belt_Set.size(u12));
 
-eq("File \"bs_poly_set_test.res\", line 53, characters 5-12", Belt_SetDict.size(u14.data), 10000);
+eq("File \"bs_poly_set_test.res\", line 53, characters 5-12", Belt_Set.size(u14), 10000);
 
-eq("File \"bs_poly_set_test.res\", line 54, characters 5-12", Belt_SetDict.size(u15.data), 1);
+eq("File \"bs_poly_set_test.res\", line 54, characters 5-12", Belt_Set.size(u15), 1);
 
 b("File \"bs_poly_set_test.res\", line 55, characters 4-11", Belt_Set.has(u15, 20000));
 
 b("File \"bs_poly_set_test.res\", line 56, characters 4-11", !Belt_Set.has(u15, 2000));
 
-b("File \"bs_poly_set_test.res\", line 57, characters 4-11", Belt_SetDict.isEmpty(u16.data));
+b("File \"bs_poly_set_test.res\", line 57, characters 4-11", Belt_Set.isEmpty(u16));
 
 let u17 = Belt_Set.fromArray(Array_data_util.randomRange(0, 100), IntCmp);
 
@@ -141,10 +140,7 @@ let u24 = Belt_Set.union(u18, u17);
 
 let u25 = Belt_Set.add(u22, 59);
 
-let u26 = Belt_Set.add({
-  cmp: IntCmp.cmp,
-  data: undefined
-}, 3);
+let u26 = Belt_Set.add(Belt_Set.make(IntCmp), 3);
 
 let ss = Belt_Array.makeByAndShuffle(100, i => (i << 1));
 
@@ -156,17 +152,17 @@ let u29 = Belt_Set.union(u26, u27);
 
 b("File \"bs_poly_set_test.res\", line 71, characters 4-11", Belt_Set.eq(u28, u29));
 
-b("File \"bs_poly_set_test.res\", line 72, characters 4-11", Primitive_object.equal(Belt_SetDict.toArray(u29.data), Belt_SortArray.stableSortBy(Belt_Array.concat(ss, [3]), Primitive_int.compare)));
+b("File \"bs_poly_set_test.res\", line 72, characters 4-11", Primitive_object.equal(Belt_Set.toArray(u29), Belt_SortArray.stableSortBy(Belt_Array.concat(ss, [3]), Primitive_int.compare)));
 
 b("File \"bs_poly_set_test.res\", line 73, characters 4-11", Belt_Set.eq(u19, u20));
 
-eq("File \"bs_poly_set_test.res\", line 74, characters 5-12", Belt_SetDict.toArray(u21.data), Array_data_util.range(59, 100));
+eq("File \"bs_poly_set_test.res\", line 74, characters 5-12", Belt_Set.toArray(u21), Array_data_util.range(59, 100));
 
-eq("File \"bs_poly_set_test.res\", line 75, characters 5-12", Belt_SetDict.toArray(u22.data), Array_data_util.range(0, 58));
+eq("File \"bs_poly_set_test.res\", line 75, characters 5-12", Belt_Set.toArray(u22), Array_data_util.range(0, 58));
 
 b("File \"bs_poly_set_test.res\", line 76, characters 4-11", Belt_Set.eq(u24, u19));
 
-eq("File \"bs_poly_set_test.res\", line 77, characters 5-12", Belt_SetDict.toArray(u23.data), Array_data_util.range(101, 200));
+eq("File \"bs_poly_set_test.res\", line 77, characters 5-12", Belt_Set.toArray(u23), Array_data_util.range(101, 200));
 
 b("File \"bs_poly_set_test.res\", line 78, characters 4-11", Belt_Set.subset(u23, u18));
 
@@ -184,21 +180,21 @@ b("File \"bs_poly_set_test.res\", line 84, characters 4-11", Belt_Set.getUndefin
 
 b("File \"bs_poly_set_test.res\", line 85, characters 4-11", undefined === Belt_Set.get(u22, 59));
 
-eq("File \"bs_poly_set_test.res\", line 87, characters 5-12", Belt_SetDict.size(u25.data), 60);
+eq("File \"bs_poly_set_test.res\", line 87, characters 5-12", Belt_Set.size(u25), 60);
 
-b("File \"bs_poly_set_test.res\", line 88, characters 4-11", Belt_SetDict.minimum(undefined) === undefined);
+b("File \"bs_poly_set_test.res\", line 88, characters 4-11", Belt_Set.minimum(Belt_Set.make(IntCmp)) === undefined);
 
-b("File \"bs_poly_set_test.res\", line 89, characters 4-11", Belt_SetDict.maximum(undefined) === undefined);
+b("File \"bs_poly_set_test.res\", line 89, characters 4-11", Belt_Set.maximum(Belt_Set.make(IntCmp)) === undefined);
 
-b("File \"bs_poly_set_test.res\", line 90, characters 4-11", Belt_SetDict.minUndefined(undefined) === undefined);
+b("File \"bs_poly_set_test.res\", line 90, characters 4-11", Belt_Set.minUndefined(Belt_Set.make(IntCmp)) === undefined);
 
-b("File \"bs_poly_set_test.res\", line 91, characters 4-11", Belt_SetDict.maxUndefined(undefined) === undefined);
+b("File \"bs_poly_set_test.res\", line 91, characters 4-11", Belt_Set.maxUndefined(Belt_Set.make(IntCmp)) === undefined);
 
 function testIterToList(xs) {
   let v = {
     contents: /* [] */0
   };
-  Belt_SetDict.forEach(xs.data, x => {
+  Belt_Set.forEach(xs, x => {
     v.contents = {
       hd: x,
       tl: v.contents
@@ -211,7 +207,7 @@ function testIterToList2(xs) {
   let v = {
     contents: /* [] */0
   };
-  Belt_SetDict.forEach(xs.data, x => {
+  Belt_SetDict.forEach(Belt_Set.getData(xs), x => {
     v.contents = {
       hd: x,
       tl: v.contents
@@ -230,45 +226,23 @@ b("File \"bs_poly_set_test.res\", line 110, characters 4-11", Belt_List.every2(t
 
 b("File \"bs_poly_set_test.res\", line 111, characters 4-11", Belt_List.every2(testIterToList2(u0$1), Belt_List.makeBy(21, i => i), (x, y) => x === y));
 
-b("File \"bs_poly_set_test.res\", line 112, characters 4-11", Belt_List.every2(testIterToList(u0$1), Belt_SetDict.toList(u0$1.data), (x, y) => x === y));
+b("File \"bs_poly_set_test.res\", line 112, characters 4-11", Belt_List.every2(testIterToList(u0$1), Belt_Set.toList(u0$1), (x, y) => x === y));
 
-function f(x) {
-  return x === 17;
-}
+b("File \"bs_poly_set_test.res\", line 113, characters 4-11", Belt_Set.some(u0$1, x => x === 17));
 
-b("File \"bs_poly_set_test.res\", line 113, characters 4-11", Belt_SetDict.some(u0$1.data, f));
+b("File \"bs_poly_set_test.res\", line 114, characters 4-11", !Belt_Set.some(u1$1, x => x === 17));
 
-function f$1(x) {
-  return x === 17;
-}
+b("File \"bs_poly_set_test.res\", line 115, characters 4-11", Belt_Set.every(u0$1, x => x < 24));
 
-b("File \"bs_poly_set_test.res\", line 114, characters 4-11", !Belt_SetDict.some(u1$1.data, f$1));
+b("File \"bs_poly_set_test.res\", line 116, characters 4-11", Belt_SetDict.every(Belt_Set.getData(u0$1), x => x < 24));
 
-function f$2(x) {
-  return x < 24;
-}
+b("File \"bs_poly_set_test.res\", line 117, characters 4-11", !Belt_Set.every(u2$1, x => x < 24));
 
-b("File \"bs_poly_set_test.res\", line 115, characters 4-11", Belt_SetDict.every(u0$1.data, f$2));
-
-b("File \"bs_poly_set_test.res\", line 116, characters 4-11", Belt_SetDict.every(u0$1.data, x => x < 24));
-
-function f$3(x) {
-  return x < 24;
-}
-
-b("File \"bs_poly_set_test.res\", line 117, characters 4-11", !Belt_SetDict.every(u2$1.data, f$3));
-
-function f$4(x) {
-  return x === 2;
-}
-
-let m = Belt_Set.fromArray([
+b("File \"bs_poly_set_test.res\", line 118, characters 4-11", !Belt_Set.every(Belt_Set.fromArray([
   1,
   2,
   3
-], IntCmp);
-
-b("File \"bs_poly_set_test.res\", line 118, characters 4-11", !Belt_SetDict.every(m.data, f$4));
+], IntCmp), x => x === 2));
 
 b("File \"bs_poly_set_test.res\", line 119, characters 4-11", Belt_Set.cmp(u1$1, u0$1) < 0);
 
@@ -302,9 +276,9 @@ t("File \"bs_poly_set_test.res\", line 132, characters 4-11", () => {
   Belt_Set.getExn(a0, -1);
 });
 
-eq("File \"bs_poly_set_test.res\", line 133, characters 5-12", Belt_SetDict.size(a0.data), 1001);
+eq("File \"bs_poly_set_test.res\", line 133, characters 5-12", Belt_Set.size(a0), 1001);
 
-b("File \"bs_poly_set_test.res\", line 134, characters 4-11", !Belt_SetDict.isEmpty(a0.data));
+b("File \"bs_poly_set_test.res\", line 134, characters 4-11", !Belt_Set.isEmpty(a0));
 
 let match$1 = Belt_Set.split(a0, 200);
 
@@ -312,9 +286,9 @@ let match$2 = match$1[0];
 
 b("File \"bs_poly_set_test.res\", line 136, characters 4-11", match$1[1]);
 
-eq("File \"bs_poly_set_test.res\", line 137, characters 5-12", Belt_SetDict.toArray(match$2[0].data), Belt_Array.makeBy(200, i => i));
+eq("File \"bs_poly_set_test.res\", line 137, characters 5-12", Belt_Set.toArray(match$2[0]), Belt_Array.makeBy(200, i => i));
 
-eq("File \"bs_poly_set_test.res\", line 138, characters 5-12", Belt_SetDict.toList(match$2[1].data), Belt_List.makeBy(800, i => i + 201 | 0));
+eq("File \"bs_poly_set_test.res\", line 138, characters 5-12", Belt_Set.toList(match$2[1]), Belt_List.makeBy(800, i => i + 201 | 0));
 
 let a7 = Belt_Set.remove(a0, 200);
 
@@ -328,13 +302,13 @@ let a8 = match$4[0];
 
 b("File \"bs_poly_set_test.res\", line 141, characters 4-11", !match$3[1]);
 
-eq("File \"bs_poly_set_test.res\", line 142, characters 5-12", Belt_SetDict.toArray(a8.data), Belt_Array.makeBy(200, i => i));
+eq("File \"bs_poly_set_test.res\", line 142, characters 5-12", Belt_Set.toArray(a8), Belt_Array.makeBy(200, i => i));
 
-eq("File \"bs_poly_set_test.res\", line 143, characters 5-12", Belt_SetDict.toList(a9.data), Belt_List.makeBy(800, i => i + 201 | 0));
+eq("File \"bs_poly_set_test.res\", line 143, characters 5-12", Belt_Set.toList(a9), Belt_List.makeBy(800, i => i + 201 | 0));
 
-eq("File \"bs_poly_set_test.res\", line 144, characters 5-12", Belt_SetDict.minimum(a8.data), 0);
+eq("File \"bs_poly_set_test.res\", line 144, characters 5-12", Belt_Set.minimum(a8), 0);
 
-eq("File \"bs_poly_set_test.res\", line 145, characters 5-12", Belt_SetDict.minimum(a9.data), 201);
+eq("File \"bs_poly_set_test.res\", line 145, characters 5-12", Belt_Set.minimum(a9), 201);
 
 Belt_List.forEach({
   hd: a0,
@@ -351,24 +325,19 @@ Belt_List.forEach({
       }
     }
   }
-}, x => Belt_SetDict.checkInvariantInternal(x.data));
+}, Belt_Set.checkInvariantInternal);
 
 let a = Belt_Set.fromArray([], IntCmp);
 
-let m$1 = Belt_Set.keep(a, x => x % 2 === 0);
-
-b("File \"bs_poly_set_test.res\", line 151, characters 4-11", Belt_SetDict.isEmpty(m$1.data));
+b("File \"bs_poly_set_test.res\", line 151, characters 4-11", Belt_Set.isEmpty(Belt_Set.keep(a, x => x % 2 === 0)));
 
-let match$5 = Belt_Set.split({
-  cmp: IntCmp.cmp,
-  data: undefined
-}, 0);
+let match$5 = Belt_Set.split(Belt_Set.make(IntCmp), 0);
 
 let match$6 = match$5[0];
 
-b("File \"bs_poly_set_test.res\", line 156, characters 4-11", Belt_SetDict.isEmpty(match$6[0].data));
+b("File \"bs_poly_set_test.res\", line 156, characters 4-11", Belt_Set.isEmpty(match$6[0]));
 
-b("File \"bs_poly_set_test.res\", line 157, characters 4-11", Belt_SetDict.isEmpty(match$6[1].data));
+b("File \"bs_poly_set_test.res\", line 157, characters 4-11", Belt_Set.isEmpty(match$6[1]));
 
 b("File \"bs_poly_set_test.res\", line 158, characters 4-11", !match$5[1]);
 
@@ -400,4 +369,4 @@ exports.IntCmp = IntCmp;
 exports.L = L;
 exports.testIterToList = testIterToList;
 exports.testIterToList2 = testIterToList2;
-/* u0 Not a pure module */
+/* IntCmp Not a pure module */
diff --git a/tests/tests/src/bs_queue_test.js b/tests/tests/src/bs_queue_test.js
index 311d15799f..238b5d0f49 100644
--- a/tests/tests/src/bs_queue_test.js
+++ b/tests/tests/src/bs_queue_test.js
@@ -36,13 +36,9 @@ function $plus$plus(q, x) {
   return q;
 }
 
-let q = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q = Belt_MutableQueue.make();
 
-if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), []) && q.length === 0)) {
+if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), []) && Belt_MutableQueue.size(q) === 0)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -54,7 +50,7 @@ if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), []) && q.length === 0
   };
 }
 
-if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q, 1), q)), [1]) && q.length === 1)) {
+if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q, 1), q)), [1]) && Belt_MutableQueue.size(q) === 1)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -69,7 +65,7 @@ if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q,
 if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q, 2), q)), [
     1,
     2
-  ]) && q.length === 2)) {
+  ]) && Belt_MutableQueue.size(q) === 2)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -85,7 +81,7 @@ if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q,
     1,
     2,
     3
-  ]) && q.length === 3)) {
+  ]) && Belt_MutableQueue.size(q) === 3)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -102,7 +98,7 @@ if (!(Primitive_object.equal(Belt_MutableQueue.toArray((Belt_MutableQueue.add(q,
     2,
     3,
     4
-  ]) && q.length === 4)) {
+  ]) && Belt_MutableQueue.size(q) === 4)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -130,7 +126,7 @@ if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), [
     2,
     3,
     4
-  ]) && q.length === 3)) {
+  ]) && Belt_MutableQueue.size(q) === 3)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -157,7 +153,7 @@ if (Belt_MutableQueue.popExn(q) !== 2) {
 if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), [
     3,
     4
-  ]) && q.length === 2)) {
+  ]) && Belt_MutableQueue.size(q) === 2)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -181,7 +177,7 @@ if (Belt_MutableQueue.popExn(q) !== 3) {
   };
 }
 
-if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), [4]) && q.length === 1)) {
+if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), [4]) && Belt_MutableQueue.size(q) === 1)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -205,7 +201,7 @@ if (Belt_MutableQueue.popExn(q) !== 4) {
   };
 }
 
-if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), []) && q.length === 0)) {
+if (!(Primitive_object.equal(Belt_MutableQueue.toArray(q), []) && Belt_MutableQueue.size(q) === 0)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -229,11 +225,7 @@ if (!does_raise(Belt_MutableQueue.popExn, q)) {
   };
 }
 
-let q$1 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q$1 = Belt_MutableQueue.make();
 
 if (Belt_MutableQueue.popExn((Belt_MutableQueue.add(q$1, 1), q$1)) !== 1) {
   throw {
@@ -283,7 +275,7 @@ if (!does_raise(Belt_MutableQueue.popExn, q$1)) {
   };
 }
 
-if (q$1.length !== 0) {
+if (Belt_MutableQueue.size(q$1) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -295,11 +287,7 @@ if (q$1.length !== 0) {
   };
 }
 
-let q$2 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q$2 = Belt_MutableQueue.make();
 
 if (Belt_MutableQueue.peekExn((Belt_MutableQueue.add(q$2, 1), q$2)) !== 1) {
   throw {
@@ -433,11 +421,7 @@ if (!does_raise(Belt_MutableQueue.peekExn, q$2)) {
   };
 }
 
-let q$3 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q$3 = Belt_MutableQueue.make();
 
 for (let i = 1; i <= 10; ++i) {
   Belt_MutableQueue.add(q$3, i);
@@ -445,7 +429,7 @@ for (let i = 1; i <= 10; ++i) {
 
 Belt_MutableQueue.clear(q$3);
 
-if (q$3.length !== 0) {
+if (Belt_MutableQueue.size(q$3) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -469,11 +453,7 @@ if (!does_raise(Belt_MutableQueue.popExn, q$3)) {
   };
 }
 
-if (!Primitive_object.equal(q$3, {
-    length: 0,
-    first: undefined,
-    last: undefined
-  })) {
+if (!Primitive_object.equal(q$3, Belt_MutableQueue.make())) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -499,11 +479,7 @@ if (Belt_MutableQueue.popExn(q$3) !== 42) {
   };
 }
 
-let q1 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q1 = Belt_MutableQueue.make();
 
 for (let i$1 = 1; i$1 <= 10; ++i$1) {
   Belt_MutableQueue.add(q1, i$1);
@@ -557,7 +533,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2), [
   };
 }
 
-if (q1.length !== 10) {
+if (Belt_MutableQueue.size(q1) !== 10) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -569,7 +545,7 @@ if (q1.length !== 10) {
   };
 }
 
-if (q2.length !== 10) {
+if (Belt_MutableQueue.size(q2) !== 10) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -611,13 +587,9 @@ for (let i$3 = 1; i$3 <= 10; ++i$3) {
   
 }
 
-let q$4 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q$4 = Belt_MutableQueue.make();
 
-if (q$4.length !== 0) {
+if (!Belt_MutableQueue.isEmpty(q$4)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -631,7 +603,7 @@ if (q$4.length !== 0) {
 
 for (let i$4 = 1; i$4 <= 10; ++i$4) {
   Belt_MutableQueue.add(q$4, i$4);
-  if (q$4.length !== i$4) {
+  if (Belt_MutableQueue.size(q$4) !== i$4) {
     throw {
       RE_EXN_ID: "Assert_failure",
       _1: [
@@ -642,7 +614,7 @@ for (let i$4 = 1; i$4 <= 10; ++i$4) {
       Error: new Error()
     };
   }
-  if (q$4.length === 0) {
+  if (Belt_MutableQueue.isEmpty(q$4)) {
     throw {
       RE_EXN_ID: "Assert_failure",
       _1: [
@@ -657,7 +629,7 @@ for (let i$4 = 1; i$4 <= 10; ++i$4) {
 }
 
 for (let i$5 = 10; i$5 >= 1; --i$5) {
-  if (q$4.length !== i$5) {
+  if (Belt_MutableQueue.size(q$4) !== i$5) {
     throw {
       RE_EXN_ID: "Assert_failure",
       _1: [
@@ -668,7 +640,7 @@ for (let i$5 = 10; i$5 >= 1; --i$5) {
       Error: new Error()
     };
   }
-  if (q$4.length === 0) {
+  if (Belt_MutableQueue.isEmpty(q$4)) {
     throw {
       RE_EXN_ID: "Assert_failure",
       _1: [
@@ -682,7 +654,7 @@ for (let i$5 = 10; i$5 >= 1; --i$5) {
   Belt_MutableQueue.popExn(q$4);
 }
 
-if (q$4.length !== 0) {
+if (Belt_MutableQueue.size(q$4) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -694,7 +666,7 @@ if (q$4.length !== 0) {
   };
 }
 
-if (q$4.length !== 0) {
+if (!Belt_MutableQueue.isEmpty(q$4)) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -706,11 +678,7 @@ if (q$4.length !== 0) {
   };
 }
 
-let q$5 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q$5 = Belt_MutableQueue.make();
 
 for (let i$6 = 1; i$6 <= 10; ++i$6) {
   Belt_MutableQueue.add(q$5, i$6);
@@ -735,19 +703,11 @@ Belt_MutableQueue.forEach(q$5, j => {
   i$7.contents = i$7.contents + 1 | 0;
 });
 
-let q1$1 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q1$1 = Belt_MutableQueue.make();
 
-let q2$1 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q2$1 = Belt_MutableQueue.make();
 
-if (q1$1.length !== 0) {
+if (Belt_MutableQueue.size(q1$1) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -771,7 +731,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$1), [])) {
   };
 }
 
-if (q2$1.length !== 0) {
+if (Belt_MutableQueue.size(q2$1) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -797,7 +757,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$1), [])) {
 
 Belt_MutableQueue.transfer(q1$1, q2$1);
 
-if (q1$1.length !== 0) {
+if (Belt_MutableQueue.size(q1$1) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -821,7 +781,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$1), [])) {
   };
 }
 
-if (q2$1.length !== 0) {
+if (Belt_MutableQueue.size(q2$1) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -845,23 +805,15 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$1), [])) {
   };
 }
 
-let q1$2 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q1$2 = Belt_MutableQueue.make();
 
-let q2$2 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q2$2 = Belt_MutableQueue.make();
 
 for (let i$8 = 1; i$8 <= 4; ++i$8) {
   Belt_MutableQueue.add(q1$2, i$8);
 }
 
-if (q1$2.length !== 4) {
+if (Belt_MutableQueue.size(q1$2) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -890,7 +842,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$2), [
   };
 }
 
-if (q2$2.length !== 0) {
+if (Belt_MutableQueue.size(q2$2) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -916,7 +868,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$2), [])) {
 
 Belt_MutableQueue.transfer(q1$2, q2$2);
 
-if (q1$2.length !== 0) {
+if (Belt_MutableQueue.size(q1$2) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -940,7 +892,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$2), [])) {
   };
 }
 
-if (q2$2.length !== 4) {
+if (Belt_MutableQueue.size(q2$2) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -969,23 +921,15 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$2), [
   };
 }
 
-let q1$3 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q1$3 = Belt_MutableQueue.make();
 
-let q2$3 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q2$3 = Belt_MutableQueue.make();
 
 for (let i$9 = 5; i$9 <= 8; ++i$9) {
   Belt_MutableQueue.add(q2$3, i$9);
 }
 
-if (q1$3.length !== 0) {
+if (Belt_MutableQueue.size(q1$3) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1009,7 +953,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$3), [])) {
   };
 }
 
-if (q2$3.length !== 4) {
+if (Belt_MutableQueue.size(q2$3) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1040,7 +984,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$3), [
 
 Belt_MutableQueue.transfer(q1$3, q2$3);
 
-if (q1$3.length !== 0) {
+if (Belt_MutableQueue.size(q1$3) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1064,7 +1008,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$3), [])) {
   };
 }
 
-if (q2$3.length !== 4) {
+if (Belt_MutableQueue.size(q2$3) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1093,17 +1037,9 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$3), [
   };
 }
 
-let q1$4 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q1$4 = Belt_MutableQueue.make();
 
-let q2$4 = {
-  length: 0,
-  first: undefined,
-  last: undefined
-};
+let q2$4 = Belt_MutableQueue.make();
 
 for (let i$10 = 1; i$10 <= 4; ++i$10) {
   Belt_MutableQueue.add(q1$4, i$10);
@@ -1113,7 +1049,7 @@ for (let i$11 = 5; i$11 <= 8; ++i$11) {
   Belt_MutableQueue.add(q2$4, i$11);
 }
 
-if (q1$4.length !== 4) {
+if (Belt_MutableQueue.size(q1$4) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1142,7 +1078,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q1$4), [
   };
 }
 
-if (q2$4.length !== 4) {
+if (Belt_MutableQueue.size(q2$4) !== 4) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1173,7 +1109,7 @@ if (!Primitive_object.equal(Belt_MutableQueue.toArray(q2$4), [
 
 Belt_MutableQueue.transfer(q1$4, q2$4);
 
-if (q1$4.length !== 0) {
+if (Belt_MutableQueue.size(q1$4) !== 0) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1208,7 +1144,7 @@ let v = [
   4
 ];
 
-if (q2$4.length !== 8) {
+if (Belt_MutableQueue.size(q2$4) !== 8) {
   throw {
     RE_EXN_ID: "Assert_failure",
     _1: [
@@ -1262,13 +1198,9 @@ eq("File \"bs_queue_test.res\", line 197, characters 5-12", Belt_MutableQueue.to
   3
 ]);
 
-let q$7 = Belt_MutableQueue.fromArray([]);
-
-b("File \"bs_queue_test.res\", line 198, characters 4-11", q$7.length === 0);
-
-let q$8 = Belt_MutableQueue.map(Belt_MutableQueue.fromArray([]), x => x + 1 | 0);
+b("File \"bs_queue_test.res\", line 198, characters 4-11", Belt_MutableQueue.isEmpty(Belt_MutableQueue.fromArray([])));
 
-b("File \"bs_queue_test.res\", line 199, characters 4-11", q$8.length === 0);
+b("File \"bs_queue_test.res\", line 199, characters 4-11", Belt_MutableQueue.isEmpty(Belt_MutableQueue.map(Belt_MutableQueue.fromArray([]), x => x + 1 | 0)));
 
 Mt.from_pair_suites("Bs_queue_test", suites.contents);
 
@@ -1281,4 +1213,4 @@ exports.b = b;
 exports.Q = Q;
 exports.does_raise = does_raise;
 exports.$plus$plus = $plus$plus;
-/*  Not a pure module */
+/* q Not a pure module */
diff --git a/tests/tests/src/bs_stack_test.js b/tests/tests/src/bs_stack_test.js
index 57e02c31ec..196666dbef 100644
--- a/tests/tests/src/bs_stack_test.js
+++ b/tests/tests/src/bs_stack_test.js
@@ -21,20 +21,14 @@ function eq(loc, x, y) {
 
 function inOrder(v) {
   let current = v;
-  let s = {
-    root: undefined
-  };
-  let q = {
-    length: 0,
-    first: undefined,
-    last: undefined
-  };
+  let s = Belt_MutableStack.make();
+  let q = Belt_MutableQueue.make();
   while (current !== undefined) {
     let v$1 = current;
     Belt_MutableStack.push(s, v$1);
     current = v$1.left;
   };
-  while (s.root !== undefined) {
+  while (!Belt_MutableStack.isEmpty(s)) {
     current = Belt_MutableStack.popUndefined(s);
     let v$2 = current;
     Belt_MutableQueue.add(q, v$2.value);
@@ -50,14 +44,8 @@ function inOrder(v) {
 
 function inOrder3(v) {
   let current = v;
-  let s = {
-    root: undefined
-  };
-  let q = {
-    length: 0,
-    first: undefined,
-    last: undefined
-  };
+  let s = Belt_MutableStack.make();
+  let q = Belt_MutableQueue.make();
   while (current !== undefined) {
     let v$1 = current;
     Belt_MutableStack.push(s, v$1);
@@ -78,26 +66,20 @@ function inOrder3(v) {
 function inOrder2(v) {
   let todo = true;
   let cursor = v;
-  let s = {
-    root: undefined
-  };
-  let q = {
-    length: 0,
-    first: undefined,
-    last: undefined
-  };
+  let s = Belt_MutableStack.make();
+  let q = Belt_MutableQueue.make();
   while (todo) {
     if (cursor !== undefined) {
       let v$1 = cursor;
       Belt_MutableStack.push(s, v$1);
       cursor = v$1.left;
-    } else if (s.root !== undefined) {
+    } else if (Belt_MutableStack.isEmpty(s)) {
+      todo = false;
+    } else {
       cursor = Belt_MutableStack.popUndefined(s);
       let current = cursor;
       Belt_MutableQueue.add(q, current.value);
       cursor = current.right;
-    } else {
-      todo = false;
     }
   };
 }
diff --git a/tests/tests/src/coercion_module_alias_test.js b/tests/tests/src/coercion_module_alias_test.js
index 85cb699628..43611c975f 100644
--- a/tests/tests/src/coercion_module_alias_test.js
+++ b/tests/tests/src/coercion_module_alias_test.js
@@ -16,9 +16,7 @@ console.log(66);
 
 let C3 = Char;
 
-let prim = 66;
-
-console.log(prim);
+console.log(66);
 
 let f = Belt_List.length;
 
@@ -32,9 +30,7 @@ function F(X) {
 
 let C4 = Char;
 
-let prim$1 = 66;
-
-console.log(prim$1);
+console.log(66);
 
 function G(X) {
   return X;
@@ -141,22 +137,28 @@ let M8 = {
   C$p: C$p$1
 };
 
+let M9_C = {
+  chr: prim => prim
+};
+
 let M9 = {
-  C: Char,
+  C: M9_C,
   C$p: C$p$1
 };
 
-let prim$2 = Char.chr(66);
+let prim = M9_C.chr(66);
 
-console.log(prim$2);
+console.log(prim);
 
 let M10 = {
-  C$p: Char
+  C$p: {
+    chr: prim => prim
+  }
 };
 
-let prim$3 = M10.C$p.chr(66);
+let prim$1 = M10.C$p.chr(66);
 
-console.log(prim$3);
+console.log(prim$1);
 
 let C;
 
diff --git a/tests/tests/src/const_defs_test.js b/tests/tests/src/const_defs_test.js
index a1b5eba93b..5511950d6a 100644
--- a/tests/tests/src/const_defs_test.js
+++ b/tests/tests/src/const_defs_test.js
@@ -1,15 +1,12 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Pervasives = require("rescript/lib/js/pervasives.js");
 
 let u = 3;
 
 function f() {
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "hi",
-    Error: new Error()
-  };
+  return Pervasives.invalid_arg("hi");
 }
 
 exports.u = u;
diff --git a/tests/tests/src/defunctor_make_test.js b/tests/tests/src/defunctor_make_test.js
index fd815af76e..09e8db0f75 100644
--- a/tests/tests/src/defunctor_make_test.js
+++ b/tests/tests/src/defunctor_make_test.js
@@ -1,6 +1,7 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 
 function getcompare(x) {
@@ -44,11 +45,7 @@ function bal(l, x, d, r) {
   hr = typeof r !== "object" ? 0 : r._4;
   if (hl > (hr + 2 | 0)) {
     if (typeof l !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.bal");
     }
     let lr = l._3;
     let ld = l._2;
@@ -56,15 +53,11 @@ function bal(l, x, d, r) {
     let ll = l._0;
     if (height(ll) >= height(lr)) {
       return create(ll, lv, ld, create(lr, x, d, r));
-    }
-    if (typeof lr === "object") {
+    } else if (typeof lr !== "object") {
+      return Pervasives.invalid_arg("Map.bal");
+    } else {
       return create(create(ll, lv, ld, lr._0), lr._1, lr._2, create(lr._3, x, d, r));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
   }
   if (hr <= (hl + 2 | 0)) {
     return {
@@ -77,11 +70,7 @@ function bal(l, x, d, r) {
     };
   }
   if (typeof r !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.bal");
   }
   let rr = r._3;
   let rd = r._2;
@@ -89,15 +78,11 @@ function bal(l, x, d, r) {
   let rl = r._0;
   if (height(rr) >= height(rl)) {
     return create(create(l, x, d, rl), rv, rd, rr);
-  }
-  if (typeof rl === "object") {
+  } else if (typeof rl !== "object") {
+    return Pervasives.invalid_arg("Map.bal");
+  } else {
     return create(create(l, x, d, rl._0), rl._1, rl._2, create(rl._3, rv, rd, rr));
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Map.bal",
-    Error: new Error()
-  };
 }
 
 function add(x, data, compare, x_) {
diff --git a/tests/tests/src/earger_curry_test.js b/tests/tests/src/earger_curry_test.js
index c2e3cea1be..f8a1a9d400 100644
--- a/tests/tests/src/earger_curry_test.js
+++ b/tests/tests/src/earger_curry_test.js
@@ -3,6 +3,7 @@
 
 let Mt = require("./mt.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 
 function map(f, a) {
   let f$1 = x => f(x);
@@ -23,11 +24,7 @@ function init(l, f) {
     return [];
   }
   if (l < 0) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Array.init",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Array.init");
   }
   let res = Belt_Array.make(l, f$1(0));
   for (let i = 1; i < l; ++i) {
diff --git a/tests/tests/src/ext_array_test.js b/tests/tests/src/ext_array_test.js
index af70707333..40e4a2ffea 100644
--- a/tests/tests/src/ext_array_test.js
+++ b/tests/tests/src/ext_array_test.js
@@ -3,6 +3,7 @@
 
 let Belt_List = require("rescript/lib/js/belt_List.js");
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_option = require("rescript/lib/js/primitive_option.js");
 
 function reverse_range(a, i, len) {
@@ -104,25 +105,19 @@ function filter_map(f, a) {
 
 function range(from, to_) {
   if (from > to_) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Ext_array_test.range",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Ext_array_test.range");
+  } else {
+    return Belt_Array.init((to_ - from | 0) + 1 | 0, i => i + from | 0);
   }
-  return Belt_Array.init((to_ - from | 0) + 1 | 0, i => i + from | 0);
 }
 
 function map2i(f, a, b) {
   let len = a.length;
   if (len !== b.length) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Ext_array_test.map2i",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Ext_array_test.map2i");
+  } else {
+    return Belt_Array.mapWithIndex(a, (i, a) => f(i, a, b[i]));
   }
-  return Belt_Array.mapWithIndex(a, (i, a) => f(i, a, b[i]));
 }
 
 function tolist_aux(a, f, _i, _res) {
diff --git a/tests/tests/src/flexible_array_test.js b/tests/tests/src/flexible_array_test.js
index 8b53d5b11a..c08e701a7b 100644
--- a/tests/tests/src/flexible_array_test.js
+++ b/tests/tests/src/flexible_array_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Belt_Array = require("rescript/lib/js/belt_Array.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_array = require("rescript/lib/js/primitive_array.js");
 let Primitive_object = require("rescript/lib/js/primitive_object.js");
 
@@ -163,12 +164,9 @@ function length(param) {
 function get(param, i) {
   if (i >= 0 && i < param[1]) {
     return sub(param[0], i + 1 | 0);
+  } else {
+    return Pervasives.invalid_arg("Array.get");
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Array.get",
-    Error: new Error()
-  };
 }
 
 function set(param, i, v) {
@@ -178,12 +176,9 @@ function set(param, i, v) {
       update(param[0], i + 1 | 0, v),
       k
     ];
+  } else {
+    return Pervasives.invalid_arg("Array.set");
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Array.set",
-    Error: new Error()
-  };
 }
 
 function push_front(param, v) {
@@ -200,12 +195,9 @@ function pop_front(param) {
       lorem(param[0]),
       k - 1 | 0
     ];
+  } else {
+    return Pervasives.invalid_arg("Array.pop_front");
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Array.pop_front",
-    Error: new Error()
-  };
 }
 
 function push_back(param, v) {
@@ -223,12 +215,9 @@ function pop_back(param) {
       $$delete(param[0], k),
       k - 1 | 0
     ];
+  } else {
+    return Pervasives.invalid_arg("Array.pop_back");
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Array.pop_back",
-    Error: new Error()
-  };
 }
 
 function filter_from(i, p, s) {
diff --git a/tests/tests/src/gpr_1423_app_test.js b/tests/tests/src/gpr_1423_app_test.js
index f3e36863a1..ab493e1656 100644
--- a/tests/tests/src/gpr_1423_app_test.js
+++ b/tests/tests/src/gpr_1423_app_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Gpr_1423_nav = require("./gpr_1423_nav.js");
 
 let suites = {
   contents: /* [] */0
@@ -30,13 +31,13 @@ function foo(f) {
   console.log(f("a1", undefined));
 }
 
-foo((none, extra) => none + "a2");
+foo((none, extra) => Gpr_1423_nav.busted(none, "a2", extra));
 
 function foo2(f) {
   return f("a1", undefined);
 }
 
-eq("File \"gpr_1423_app_test.res\", line 18, characters 12-19", "a1a2", "a1a2");
+eq("File \"gpr_1423_app_test.res\", line 18, characters 12-19", Gpr_1423_nav.busted("a1", "a2", undefined), "a1a2");
 
 Mt.from_pair_suites("Gpr_1423_app_test", suites.contents);
 
diff --git a/tests/tests/src/gpr_2316_test.js b/tests/tests/src/gpr_2316_test.js
index 75a2d85d7a..d899c5ae1c 100644
--- a/tests/tests/src/gpr_2316_test.js
+++ b/tests/tests/src/gpr_2316_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_exceptions = require("rescript/lib/js/primitive_exceptions.js");
 
 let suites = {
@@ -30,11 +31,8 @@ function eq(loc, x, y) {
 let y;
 
 try {
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "boo",
-    Error: new Error()
-  };
+  Pervasives.failwith("boo");
+  y = undefined;
 } catch (raw_msg) {
   let msg = Primitive_exceptions.internalToException(raw_msg);
   if (msg.RE_EXN_ID === "Failure") {
@@ -48,12 +46,11 @@ let x;
 
 let exit = 0;
 
+let e;
+
 try {
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "boo",
-    Error: new Error()
-  };
+  e = Pervasives.failwith("boo");
+  exit = 1;
 } catch (raw_msg$1) {
   let msg$1 = Primitive_exceptions.internalToException(raw_msg$1);
   if (msg$1.RE_EXN_ID === "Failure") {
diff --git a/tests/tests/src/gpr_3865.js b/tests/tests/src/gpr_3865.js
index 1eb9de4f87..332dd4de57 100644
--- a/tests/tests/src/gpr_3865.js
+++ b/tests/tests/src/gpr_3865.js
@@ -1,16 +1,17 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Gpr_3865_bar = require("./gpr_3865_bar.js");
 let Gpr_3865_foo = require("./gpr_3865_foo.js");
 
-let B = Gpr_3865_foo;
+let B = Gpr_3865_bar.Make(Gpr_3865_foo);
 
 console.log(Gpr_3865_foo.$$return);
 
-console.log(Gpr_3865_foo.$$return);
+console.log(B.$$return);
 
 let F;
 
 exports.F = F;
 exports.B = B;
-/*  Not a pure module */
+/* B Not a pure module */
diff --git a/tests/tests/src/gpr_4265_test.js b/tests/tests/src/gpr_4265_test.js
index 30f8a89405..639981fc25 100644
--- a/tests/tests/src/gpr_4265_test.js
+++ b/tests/tests/src/gpr_4265_test.js
@@ -3,7 +3,6 @@
 
 let Mt = require("./mt.js");
 let Belt_MutableMapInt = require("rescript/lib/js/belt_MutableMapInt.js");
-let Belt_internalMapInt = require("rescript/lib/js/belt_internalMapInt.js");
 
 let suites = {
   contents: /* [] */0
@@ -17,9 +16,7 @@ function eq(loc, x, y) {
   Mt.eq_suites(test_id, suites, loc, x, y);
 }
 
-let mockMap = {
-  data: undefined
-};
+let mockMap = Belt_MutableMapInt.make();
 
 function add(id) {
   Belt_MutableMapInt.set(mockMap, id, id);
@@ -38,7 +35,7 @@ add(486);
 
 Belt_MutableMapInt.remove(mockMap, 1726);
 
-let n1 = Belt_internalMapInt.getExn(mockMap.data, 6667);
+let n1 = Belt_MutableMapInt.getExn(mockMap, 6667);
 
 eq("File \"gpr_4265_test.res\", line 18, characters 3-10", n, n1);
 
@@ -52,4 +49,4 @@ exports.add = add;
 exports.remove = remove;
 exports.n = n;
 exports.n1 = n1;
-/*  Not a pure module */
+/* mockMap Not a pure module */
diff --git a/tests/tests/src/hello_res.js b/tests/tests/src/hello_res.js
index 34fadda626..8c6da225f1 100644
--- a/tests/tests/src/hello_res.js
+++ b/tests/tests/src/hello_res.js
@@ -18,7 +18,7 @@ let a = b - 1 | 0;
 
 console.log("hello, res");
 
-Belt_List.length({
+Belt_List.add(/* [] */0, Belt_List.length({
   hd: 1,
   tl: {
     hd: 2,
@@ -27,7 +27,7 @@ Belt_List.length({
       tl: /* [] */0
     }
   }
-});
+}));
 
 console.log(3);
 
diff --git a/tests/tests/src/inline_const_test.js b/tests/tests/src/inline_const_test.js
index 62db03c4f0..a04ff5fd8d 100644
--- a/tests/tests/src/inline_const_test.js
+++ b/tests/tests/src/inline_const_test.js
@@ -16,7 +16,7 @@ function eq(loc, x, y) {
   Mt.eq_suites(test_id, suites, loc, x, y);
 }
 
-let H = {};
+let H = Inline_const.N1({});
 
 let f = "hello";
 
@@ -64,4 +64,4 @@ exports.f4 = f4;
 exports.f5 = f5;
 exports.f6 = f6;
 exports.f7 = f7;
-/*  Not a pure module */
+/* H Not a pure module */
diff --git a/tests/tests/src/inline_map2_test.js b/tests/tests/src/inline_map2_test.js
index 207455b1c8..baf869cdab 100644
--- a/tests/tests/src/inline_map2_test.js
+++ b/tests/tests/src/inline_map2_test.js
@@ -3,6 +3,7 @@
 
 let Mt = require("./mt.js");
 let Belt_List = require("rescript/lib/js/belt_List.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 let Primitive_option = require("rescript/lib/js/primitive_option.js");
 let Primitive_string = require("rescript/lib/js/primitive_string.js");
@@ -42,11 +43,7 @@ function Make(Ord) {
     hr = typeof r !== "object" ? 0 : r._4;
     if (hl > (hr + 2 | 0)) {
       if (typeof l !== "object") {
-        throw {
-          RE_EXN_ID: "Invalid_argument",
-          _1: "Map.bal",
-          Error: new Error()
-        };
+        return Pervasives.invalid_arg("Map.bal");
       }
       let lr = l._3;
       let ld = l._2;
@@ -54,15 +51,11 @@ function Make(Ord) {
       let ll = l._0;
       if (height(ll) >= height(lr)) {
         return create(ll, lv, ld, create(lr, x, d, r));
-      }
-      if (typeof lr === "object") {
+      } else if (typeof lr !== "object") {
+        return Pervasives.invalid_arg("Map.bal");
+      } else {
         return create(create(ll, lv, ld, lr._0), lr._1, lr._2, create(lr._3, x, d, r));
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
     }
     if (hr <= (hl + 2 | 0)) {
       return {
@@ -75,11 +68,7 @@ function Make(Ord) {
       };
     }
     if (typeof r !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.bal");
     }
     let rr = r._3;
     let rd = r._2;
@@ -87,15 +76,11 @@ function Make(Ord) {
     let rl = r._0;
     if (height(rr) >= height(rl)) {
       return create(create(l, x, d, rl), rv, rd, rr);
-    }
-    if (typeof rl === "object") {
+    } else if (typeof rl !== "object") {
+      return Pervasives.invalid_arg("Map.bal");
+    } else {
       return create(create(l, x, d, rl._0), rl._1, rl._2, create(rl._3, rv, rd, rr));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
   };
   let is_empty = x => {
     if (typeof x !== "object") {
@@ -208,11 +193,7 @@ function Make(Ord) {
   };
   let remove_min_binding = x => {
     if (typeof x !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.remove_min_elt",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.remove_min_elt");
     }
     let l = x._0;
     if (typeof l !== "object") {
@@ -667,11 +648,7 @@ function bal(l, x, d, r) {
   hr = typeof r !== "object" ? 0 : r._4;
   if (hl > (hr + 2 | 0)) {
     if (typeof l !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.bal");
     }
     let lr = l._3;
     let ld = l._2;
@@ -679,15 +656,11 @@ function bal(l, x, d, r) {
     let ll = l._0;
     if (height(ll) >= height(lr)) {
       return create(ll, lv, ld, create(lr, x, d, r));
-    }
-    if (typeof lr === "object") {
+    } else if (typeof lr !== "object") {
+      return Pervasives.invalid_arg("Map.bal");
+    } else {
       return create(create(ll, lv, ld, lr._0), lr._1, lr._2, create(lr._3, x, d, r));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
   }
   if (hr <= (hl + 2 | 0)) {
     return {
@@ -700,11 +673,7 @@ function bal(l, x, d, r) {
     };
   }
   if (typeof r !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.bal");
   }
   let rr = r._3;
   let rd = r._2;
@@ -712,15 +681,11 @@ function bal(l, x, d, r) {
   let rl = r._0;
   if (height(rr) >= height(rl)) {
     return create(create(l, x, d, rl), rv, rd, rr);
-  }
-  if (typeof rl === "object") {
+  } else if (typeof rl !== "object") {
+    return Pervasives.invalid_arg("Map.bal");
+  } else {
     return create(create(l, x, d, rl._0), rl._1, rl._2, create(rl._3, rv, rd, rr));
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Map.bal",
-    Error: new Error()
-  };
 }
 
 function is_empty(x) {
@@ -840,11 +805,7 @@ function max_binding(_x) {
 
 function remove_min_binding(x) {
   if (typeof x !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.remove_min_elt",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.remove_min_elt");
   }
   let l = x._0;
   if (typeof l !== "object") {
@@ -1349,11 +1310,7 @@ function bal$1(l, x, d, r) {
   hr = typeof r !== "object" ? 0 : r._4;
   if (hl > (hr + 2 | 0)) {
     if (typeof l !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.bal");
     }
     let lr = l._3;
     let ld = l._2;
@@ -1361,15 +1318,11 @@ function bal$1(l, x, d, r) {
     let ll = l._0;
     if (height$1(ll) >= height$1(lr)) {
       return create$1(ll, lv, ld, create$1(lr, x, d, r));
-    }
-    if (typeof lr === "object") {
+    } else if (typeof lr !== "object") {
+      return Pervasives.invalid_arg("Map.bal");
+    } else {
       return create$1(create$1(ll, lv, ld, lr._0), lr._1, lr._2, create$1(lr._3, x, d, r));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
   }
   if (hr <= (hl + 2 | 0)) {
     return {
@@ -1382,11 +1335,7 @@ function bal$1(l, x, d, r) {
     };
   }
   if (typeof r !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.bal");
   }
   let rr = r._3;
   let rd = r._2;
@@ -1394,15 +1343,11 @@ function bal$1(l, x, d, r) {
   let rl = r._0;
   if (height$1(rr) >= height$1(rl)) {
     return create$1(create$1(l, x, d, rl), rv, rd, rr);
-  }
-  if (typeof rl === "object") {
+  } else if (typeof rl !== "object") {
+    return Pervasives.invalid_arg("Map.bal");
+  } else {
     return create$1(create$1(l, x, d, rl._0), rl._1, rl._2, create$1(rl._3, rv, rd, rr));
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Map.bal",
-    Error: new Error()
-  };
 }
 
 function is_empty$1(x) {
@@ -1522,11 +1467,7 @@ function max_binding$1(_x) {
 
 function remove_min_binding$1(x) {
   if (typeof x !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.remove_min_elt",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.remove_min_elt");
   }
   let l = x._0;
   if (typeof l !== "object") {
diff --git a/tests/tests/src/inline_map_test.js b/tests/tests/src/inline_map_test.js
index 6da2b307a3..dd0942860a 100644
--- a/tests/tests/src/inline_map_test.js
+++ b/tests/tests/src/inline_map_test.js
@@ -3,6 +3,7 @@
 
 let Mt = require("./mt.js");
 let Belt_List = require("rescript/lib/js/belt_List.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_int = require("rescript/lib/js/primitive_int.js");
 
 function height(x) {
@@ -33,11 +34,7 @@ function bal(l, x, d, r) {
   hr = typeof r !== "object" ? 0 : r._4;
   if (hl > (hr + 2 | 0)) {
     if (typeof l !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Map.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Map.bal");
     }
     let lr = l._3;
     let ld = l._2;
@@ -45,15 +42,11 @@ function bal(l, x, d, r) {
     let ll = l._0;
     if (height(ll) >= height(lr)) {
       return create(ll, lv, ld, create(lr, x, d, r));
-    }
-    if (typeof lr === "object") {
+    } else if (typeof lr !== "object") {
+      return Pervasives.invalid_arg("Map.bal");
+    } else {
       return create(create(ll, lv, ld, lr._0), lr._1, lr._2, create(lr._3, x, d, r));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
   }
   if (hr <= (hl + 2 | 0)) {
     return {
@@ -66,11 +59,7 @@ function bal(l, x, d, r) {
     };
   }
   if (typeof r !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Map.bal",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Map.bal");
   }
   let rr = r._3;
   let rd = r._2;
@@ -78,15 +67,11 @@ function bal(l, x, d, r) {
   let rl = r._0;
   if (height(rr) >= height(rl)) {
     return create(create(l, x, d, rl), rv, rd, rr);
-  }
-  if (typeof rl === "object") {
+  } else if (typeof rl !== "object") {
+    return Pervasives.invalid_arg("Map.bal");
+  } else {
     return create(create(l, x, d, rl._0), rl._1, rl._2, create(rl._3, rv, rd, rr));
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "Map.bal",
-    Error: new Error()
-  };
 }
 
 function add(x, data, x_) {
diff --git a/tests/tests/src/int_map.js b/tests/tests/src/int_map.js
index c3a14ba60c..cd29ea61bd 100644
--- a/tests/tests/src/int_map.js
+++ b/tests/tests/src/int_map.js
@@ -1,21 +1,17 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 'use strict';
 
+let Belt_Id = require("rescript/lib/js/belt_Id.js");
 let Belt_Map = require("rescript/lib/js/belt_Map.js");
 let Primitive_object = require("rescript/lib/js/primitive_object.js");
 
 let cmp = Primitive_object.compare;
 
-let IntCmp = {
+let IntCmp = Belt_Id.MakeComparable({
   cmp: cmp
-};
+});
 
-let m_cmp = IntCmp.cmp;
-
-let m = {
-  cmp: m_cmp,
-  data: undefined
-};
+let m = Belt_Map.make(IntCmp);
 
 let m$1 = Belt_Map.set(m, 0, "test");
 
diff --git a/tests/tests/src/js_exception_catch_test.js b/tests/tests/src/js_exception_catch_test.js
index 9d89afdca8..961acada64 100644
--- a/tests/tests/src/js_exception_catch_test.js
+++ b/tests/tests/src/js_exception_catch_test.js
@@ -3,6 +3,7 @@
 
 let Mt = require("./mt.js");
 let Js_exn = require("rescript/lib/js/js_exn.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 let Primitive_exceptions = require("rescript/lib/js/primitive_exceptions.js");
 
 let suites = {
@@ -124,21 +125,9 @@ eq("File \"js_exception_catch_test.res\", line 45, characters 5-12", test(() =>
   };
 }), "Not_found");
 
-eq("File \"js_exception_catch_test.res\", line 46, characters 5-12", test(() => {
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "x",
-    Error: new Error()
-  };
-}), "Invalid_argument");
+eq("File \"js_exception_catch_test.res\", line 46, characters 5-12", test(() => Pervasives.invalid_arg("x")), "Invalid_argument");
 
-eq("File \"js_exception_catch_test.res\", line 47, characters 5-12", test(() => {
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "",
-    Error: new Error()
-  };
-}), "Invalid_any");
+eq("File \"js_exception_catch_test.res\", line 47, characters 5-12", test(() => Pervasives.invalid_arg("")), "Invalid_any");
 
 eq("File \"js_exception_catch_test.res\", line 48, characters 5-12", test(() => {
   throw {
@@ -181,17 +170,9 @@ eq("File \"js_exception_catch_test.res\", line 52, characters 5-12", test(() =>
   };
 }), "C_any");
 
-eq("File \"js_exception_catch_test.res\", line 53, characters 5-12", test(() => {
-  throw new Error("x");
-}), "Js_error");
+eq("File \"js_exception_catch_test.res\", line 53, characters 5-12", test(() => Js_exn.raiseError("x")), "Js_error");
 
-eq("File \"js_exception_catch_test.res\", line 54, characters 5-12", test(() => {
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "x",
-    Error: new Error()
-  };
-}), "Any");
+eq("File \"js_exception_catch_test.res\", line 54, characters 5-12", test(() => Pervasives.failwith("x")), "Any");
 
 Mt.from_pair_suites("Js_exception_catch_test", suites.contents);
 
diff --git a/tests/tests/src/js_option_test.js b/tests/tests/src/js_option_test.js
index af3d8a471a..6063f2a913 100644
--- a/tests/tests/src/js_option_test.js
+++ b/tests/tests/src/js_option_test.js
@@ -13,7 +13,7 @@ let option_suites_0 = [
   param => ({
     TAG: "Eq",
     _0: true,
-    _1: true
+    _1: Js_option.isSome(1)
   })
 ];
 
@@ -23,7 +23,7 @@ let option_suites_1 = {
     param => ({
       TAG: "Eq",
       _0: false,
-      _1: false
+      _1: Js_option.isSome(undefined)
     })
   ],
   tl: {
@@ -32,7 +32,7 @@ let option_suites_1 = {
       param => ({
         TAG: "Eq",
         _0: false,
-        _1: false
+        _1: Js_option.isNone(1)
       })
     ],
     tl: {
@@ -41,7 +41,7 @@ let option_suites_1 = {
         param => ({
           TAG: "Eq",
           _0: true,
-          _1: true
+          _1: Js_option.isNone(undefined)
         })
       ],
       tl: {
diff --git a/tests/tests/src/js_string_test.js b/tests/tests/src/js_string_test.js
index f04e75c9c0..bf7b1a16f7 100644
--- a/tests/tests/src/js_string_test.js
+++ b/tests/tests/src/js_string_test.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Mt = require("./mt.js");
+let Js_string = require("rescript/lib/js/js_string.js");
 let Belt_Option = require("rescript/lib/js/belt_Option.js");
 let Primitive_option = require("rescript/lib/js/primitive_option.js");
 
@@ -419,7 +420,7 @@ let suites_1 = {
                                                                                     ":",
                                                                                     "c"
                                                                                   ],
-                                                                                  _1: "a#b#:c".split(/(#)(:)?/)
+                                                                                  _1: Js_string.splitByRe(/(#)(:)?/, "a#b#:c")
                                                                                 })
                                                                               ],
                                                                               tl: {
@@ -432,7 +433,7 @@ let suites_1 = {
                                                                                       "#",
                                                                                       undefined
                                                                                     ],
-                                                                                    _1: "a#b#:c".split(/(#)(:)?/, 3)
+                                                                                    _1: Js_string.splitByReAtMost(/(#)(:)?/, 3, "a#b#:c")
                                                                                   })
                                                                                 ],
                                                                                 tl: {
diff --git a/tests/tests/src/mario_game.js b/tests/tests/src/mario_game.js
index a183b1dd7a..e9a2900d90 100644
--- a/tests/tests/src/mario_game.js
+++ b/tests/tests/src/mario_game.js
@@ -1497,11 +1497,7 @@ function game_win(ctx) {
   ctx.fillStyle = "white";
   ctx.font = "20px 'Press Start 2P'";
   ctx.fillText("You win!", 180, 128);
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "Game over.",
-    Error: new Error()
-  };
+  return Pervasives.failwith("Game over.");
 }
 
 function game_loss(ctx) {
@@ -1511,11 +1507,7 @@ function game_loss(ctx) {
   ctx.fillStyle = "white";
   ctx.font = "20px 'Press Start 2P'";
   ctx.fillText("GAME OVER. You lose!", 60, 128);
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "Game over.",
-    Error: new Error()
-  };
+  return Pervasives.failwith("Game over.");
 }
 
 let Draw = {
@@ -2475,11 +2467,7 @@ function choose_enemy_typ(typ) {
     case 2 :
       return "Goomba";
     default:
-      throw {
-        RE_EXN_ID: "Failure",
-        _1: "Shouldn't reach here",
-        Error: new Error()
-      };
+      return Pervasives.failwith("Shouldn't reach here");
   }
 }
 
@@ -2499,11 +2487,7 @@ function choose_sblock_typ(typ) {
     case 4 :
       return "Ground";
     default:
-      throw {
-        RE_EXN_ID: "Failure",
-        _1: "Shouldn't reach here",
-        Error: new Error()
-      };
+      return Pervasives.failwith("Shouldn't reach here");
   }
 }
 
@@ -3014,11 +2998,7 @@ function choose_block_pattern(blockw, blockh, cbx, cby, prob) {
         tl: /* [] */0
       };
     default:
-      throw {
-        RE_EXN_ID: "Failure",
-        _1: "Shouldn't reach here",
-        Error: new Error()
-      };
+      return Pervasives.failwith("Shouldn't reach here");
   }
 }
 
@@ -3281,17 +3261,7 @@ let loadCount = {
 function load(param) {
   let canvas_id = "canvas";
   let el = document.getElementById(canvas_id);
-  let canvas;
-  if (el !== null) {
-    canvas = el;
-  } else {
-    console.log("cant find canvas " + canvas_id);
-    throw {
-      RE_EXN_ID: "Failure",
-      _1: "fail",
-      Error: new Error()
-    };
-  }
+  let canvas = el !== null ? el : (console.log("cant find canvas " + canvas_id), Pervasives.failwith("fail"));
   let context = canvas.getContext("2d");
   document.addEventListener("keydown", keydown, true);
   document.addEventListener("keyup", keyup, true);
diff --git a/tests/tests/src/mt.js b/tests/tests/src/mt.js
index fd42b6837b..efffe653b6 100644
--- a/tests/tests/src/mt.js
+++ b/tests/tests/src/mt.js
@@ -5,6 +5,7 @@ let Path = require("path");
 let Assert = require("assert");
 let Process = require("process");
 let Belt_List = require("rescript/lib/js/belt_List.js");
+let Js_promise = require("rescript/lib/js/js_promise.js");
 
 function assert_fail(msg) {
   Assert.fail(undefined, undefined, msg, "");
@@ -221,10 +222,10 @@ function old_from_promise_suites_donotuse(name, suites) {
     if (is_mocha()) {
       describe(name, () => Belt_List.forEach(suites, param => {
         let code = param[1];
-        it(param[0], () => code.then(x => {
+        it(param[0], () => Js_promise.then_(x => {
           handleCode(x);
           return val_unit;
-        }));
+        }, code));
       }));
     } else {
       console.log("promise suites");
diff --git a/tests/tests/src/reactDOMRe.js b/tests/tests/src/reactDOMRe.js
index dee8919f57..c63357a109 100644
--- a/tests/tests/src/reactDOMRe.js
+++ b/tests/tests/src/reactDOMRe.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let React = require("react");
+let Js_array = require("rescript/lib/js/js_array.js");
 let ReactDom = require("react-dom");
 
 function renderToElementWithClassName(reactElement, className) {
@@ -81,10 +82,10 @@ function hydrateToElementWithId(reactElement, id) {
 let Ref = {};
 
 function createElementVariadic(domClassName, props, children) {
-  let variadicArguments = [
+  let variadicArguments = Js_array.concat(children, [
     domClassName,
     props
-  ].concat(children);
+  ]);
   return React.createElement.apply(null, variadicArguments);
 }
 
diff --git a/tests/tests/src/reasonReact.js b/tests/tests/src/reasonReact.js
index afbce1d035..361212c8ed 100644
--- a/tests/tests/src/reasonReact.js
+++ b/tests/tests/src/reasonReact.js
@@ -2,12 +2,13 @@
 'use strict';
 
 let React = require("react");
+let Js_array = require("rescript/lib/js/js_array.js");
 
 function createDomElement(s, props, children) {
-  let vararg = [
+  let vararg = Js_array.concat(children, [
     s,
     props
-  ].concat(children);
+  ]);
   return React.createElement.apply(null, vararg);
 }
 
@@ -97,10 +98,10 @@ function wrapJsForReason(reactClass, props, children) {
       ref: extra$1,
       key: extra
     });
-    let varargs = [
+    let varargs = Js_array.concat(children, [
       reactClass,
       props$1
-    ].concat(children);
+    ]);
     return React.createElement.apply(null, varargs);
   };
   return {
diff --git a/tests/tests/src/reasonReactRouter.js b/tests/tests/src/reasonReactRouter.js
index 2df6d93fd1..767a4b64a3 100644
--- a/tests/tests/src/reasonReactRouter.js
+++ b/tests/tests/src/reasonReactRouter.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let React = require("react");
+let Js_string = require("rescript/lib/js/js_string.js");
 let Primitive_option = require("rescript/lib/js/primitive_option.js");
 
 function safeMakeEvent(eventName) {
@@ -24,10 +25,10 @@ function path() {
     case "/" :
       return /* [] */0;
     default:
-      let raw$1 = raw.slice(1);
+      let raw$1 = Js_string.sliceToEnd(1, raw);
       let match = raw$1[raw$1.length - 1 | 0];
-      let raw$2 = match === "/" ? raw$1.slice(0, -1) : raw$1;
-      let a = raw$2.split("/");
+      let raw$2 = match === "/" ? Js_string.slice(0, -1, raw$1) : raw$1;
+      let a = Js_string.split("/", raw$2);
       let _i = a.length - 1 | 0;
       let _res = /* [] */0;
       while (true) {
@@ -57,7 +58,7 @@ function hash() {
     case "#" :
       return "";
     default:
-      return raw.slice(1);
+      return Js_string.sliceToEnd(1, raw);
   }
 }
 
@@ -72,7 +73,7 @@ function search() {
     case "?" :
       return "";
     default:
-      return raw.slice(1);
+      return Js_string.sliceToEnd(1, raw);
   }
 }
 
diff --git a/tests/tests/src/set_gen.js b/tests/tests/src/set_gen.js
index 3becff0e2e..83031c9875 100644
--- a/tests/tests/src/set_gen.js
+++ b/tests/tests/src/set_gen.js
@@ -317,11 +317,7 @@ function internal_bal(l, v, r) {
 
 function remove_min_elt(x) {
   if (typeof x !== "object") {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Set.remove_min_elt",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("Set.remove_min_elt");
   }
   let l = x._0;
   if (typeof l !== "object") {
diff --git a/tests/tests/src/string_set.js b/tests/tests/src/string_set.js
index cc6a15abcf..63c209aee1 100644
--- a/tests/tests/src/string_set.js
+++ b/tests/tests/src/string_set.js
@@ -241,7 +241,7 @@ function find(x, _tree) {
 
 function of_list(l) {
   if (!l) {
-    return "Empty";
+    return Set_gen.empty;
   }
   let match = l.tl;
   let x0 = l.hd;
@@ -272,7 +272,7 @@ function of_list(l) {
 }
 
 function of_array(l) {
-  return Belt_Array.reduceReverse(l, "Empty", (acc, x) => add(x, acc));
+  return Belt_Array.reduceReverse(l, Set_gen.empty, (acc, x) => add(x, acc));
 }
 
 function invariant(t) {
@@ -280,7 +280,7 @@ function invariant(t) {
   return Set_gen.is_ordered(compare_elt, t);
 }
 
-let empty = "Empty";
+let empty = Set_gen.empty;
 
 let is_empty = Set_gen.is_empty;
 
diff --git a/tests/tests/src/test_list.js b/tests/tests/src/test_list.js
index 3d027ed08f..7b3a88a18f 100644
--- a/tests/tests/src/test_list.js
+++ b/tests/tests/src/test_list.js
@@ -24,51 +24,37 @@ function length(l) {
 function hd(x) {
   if (x) {
     return x.hd;
+  } else {
+    return Pervasives.failwith("hd");
   }
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "hd",
-    Error: new Error()
-  };
 }
 
 function tl(x) {
   if (x) {
     return x.tl;
+  } else {
+    return Pervasives.failwith("tl");
   }
-  throw {
-    RE_EXN_ID: "Failure",
-    _1: "tl",
-    Error: new Error()
-  };
 }
 
 function nth(l, n) {
   if (n < 0) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.nth",
-      Error: new Error()
-    };
+    return Pervasives.invalid_arg("List.nth");
   }
   let _l = l;
   let _n = n;
   while (true) {
     let n$1 = _n;
     let l$1 = _l;
-    if (l$1) {
-      if (n$1 === 0) {
-        return l$1.hd;
-      }
-      _n = n$1 - 1 | 0;
-      _l = l$1.tl;
-      continue;
+    if (!l$1) {
+      return Pervasives.failwith("nth");
     }
-    throw {
-      RE_EXN_ID: "Failure",
-      _1: "nth",
-      Error: new Error()
-    };
+    if (n$1 === 0) {
+      return l$1.hd;
+    }
+    _n = n$1 - 1 | 0;
+    _l = l$1.tl;
+    continue;
   };
 }
 
@@ -194,27 +180,20 @@ function fold_right(f, l, accu) {
 }
 
 function map2(f, l1, l2) {
-  if (l1) {
+  if (!l1) {
     if (l2) {
-      let r = f(l1.hd, l2.hd);
-      return {
-        hd: r,
-        tl: map2(f, l1.tl, l2.tl)
-      };
+      return Pervasives.invalid_arg("List.map2");
+    } else {
+      return /* [] */0;
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.map2",
-      Error: new Error()
-    };
   }
   if (!l2) {
-    return /* [] */0;
+    return Pervasives.invalid_arg("List.map2");
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "List.map2",
-    Error: new Error()
+  let r = f(l1.hd, l2.hd);
+  return {
+    hd: r,
+    tl: map2(f, l1.tl, l2.tl)
   };
 }
 
@@ -226,30 +205,23 @@ function rev_map2(f, l1, l2) {
     let l2$1 = _l2;
     let l1$1 = _l1;
     let accu = _accu;
-    if (l1$1) {
+    if (!l1$1) {
       if (l2$1) {
-        _l2 = l2$1.tl;
-        _l1 = l1$1.tl;
-        _accu = {
-          hd: f(l1$1.hd, l2$1.hd),
-          tl: accu
-        };
-        continue;
+        return Pervasives.invalid_arg("List.rev_map2");
+      } else {
+        return accu;
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.rev_map2",
-        Error: new Error()
-      };
     }
-    if (l2$1) {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.rev_map2",
-        Error: new Error()
-      };
+    if (!l2$1) {
+      return Pervasives.invalid_arg("List.rev_map2");
     }
-    return accu;
+    _l2 = l2$1.tl;
+    _l1 = l1$1.tl;
+    _accu = {
+      hd: f(l1$1.hd, l2$1.hd),
+      tl: accu
+    };
+    continue;
   };
 }
 
@@ -257,27 +229,20 @@ function iter2(f, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (l1) {
+    if (!l1) {
       if (l2) {
-        f(l1.hd, l2.hd);
-        _l2 = l2.tl;
-        _l1 = l1.tl;
-        continue;
+        return Pervasives.invalid_arg("List.iter2");
+      } else {
+        return;
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.iter2",
-        Error: new Error()
-      };
     }
     if (!l2) {
-      return;
+      return Pervasives.invalid_arg("List.iter2");
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.iter2",
-      Error: new Error()
-    };
+    f(l1.hd, l2.hd);
+    _l2 = l2.tl;
+    _l1 = l1.tl;
+    continue;
   };
 }
 
@@ -286,27 +251,20 @@ function fold_left2(f, _accu, _l1, _l2) {
     let l2 = _l2;
     let l1 = _l1;
     let accu = _accu;
-    if (l1) {
+    if (!l1) {
       if (l2) {
-        _l2 = l2.tl;
-        _l1 = l1.tl;
-        _accu = f(accu, l1.hd, l2.hd);
-        continue;
+        return Pervasives.invalid_arg("List.fold_left2");
+      } else {
+        return accu;
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.fold_left2",
-        Error: new Error()
-      };
     }
-    if (l2) {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.fold_left2",
-        Error: new Error()
-      };
+    if (!l2) {
+      return Pervasives.invalid_arg("List.fold_left2");
     }
-    return accu;
+    _l2 = l2.tl;
+    _l1 = l1.tl;
+    _accu = f(accu, l1.hd, l2.hd);
+    continue;
   };
 }
 
@@ -314,21 +272,14 @@ function fold_right2(f, l1, l2, accu) {
   if (l1) {
     if (l2) {
       return f(l1.hd, l2.hd, fold_right2(f, l1.tl, l2.tl, accu));
+    } else {
+      return Pervasives.invalid_arg("List.fold_right2");
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.fold_right2",
-      Error: new Error()
-    };
-  }
-  if (l2) {
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.fold_right2",
-      Error: new Error()
-    };
+  } else if (l2) {
+    return Pervasives.invalid_arg("List.fold_right2");
+  } else {
+    return accu;
   }
-  return accu;
 }
 
 function for_all(p, _x) {
@@ -363,29 +314,22 @@ function for_all2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (l1) {
+    if (!l1) {
       if (l2) {
-        if (!p(l1.hd, l2.hd)) {
-          return false;
-        }
-        _l2 = l2.tl;
-        _l1 = l1.tl;
-        continue;
+        return Pervasives.invalid_arg("List.for_all2");
+      } else {
+        return true;
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.for_all2",
-        Error: new Error()
-      };
     }
     if (!l2) {
-      return true;
+      return Pervasives.invalid_arg("List.for_all2");
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.for_all2",
-      Error: new Error()
-    };
+    if (!p(l1.hd, l2.hd)) {
+      return false;
+    }
+    _l2 = l2.tl;
+    _l1 = l1.tl;
+    continue;
   };
 }
 
@@ -393,29 +337,22 @@ function exists2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (l1) {
+    if (!l1) {
       if (l2) {
-        if (p(l1.hd, l2.hd)) {
-          return true;
-        }
-        _l2 = l2.tl;
-        _l1 = l1.tl;
-        continue;
+        return Pervasives.invalid_arg("List.exists2");
+      } else {
+        return false;
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "List.exists2",
-        Error: new Error()
-      };
     }
     if (!l2) {
-      return false;
+      return Pervasives.invalid_arg("List.exists2");
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.exists2",
-      Error: new Error()
-    };
+    if (p(l1.hd, l2.hd)) {
+      return true;
+    }
+    _l2 = l2.tl;
+    _l1 = l1.tl;
+    continue;
   };
 }
 
@@ -651,21 +588,14 @@ function combine(l1, l2) {
         ],
         tl: combine(l1.tl, l2.tl)
       };
+    } else {
+      return Pervasives.invalid_arg("List.combine");
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "List.combine",
-      Error: new Error()
-    };
-  }
-  if (!l2) {
+  } else if (l2) {
+    return Pervasives.invalid_arg("List.combine");
+  } else {
     return /* [] */0;
   }
-  throw {
-    RE_EXN_ID: "Invalid_argument",
-    _1: "List.combine",
-    Error: new Error()
-  };
 }
 
 function merge(cmp, l1, l2) {
diff --git a/tests/tests/src/test_set.js b/tests/tests/src/test_set.js
index fbfe093bc8..65f096c409 100644
--- a/tests/tests/src/test_set.js
+++ b/tests/tests/src/test_set.js
@@ -2,6 +2,7 @@
 'use strict';
 
 let Belt_List = require("rescript/lib/js/belt_List.js");
+let Pervasives = require("rescript/lib/js/pervasives.js");
 
 function Make(Ord) {
   let height = x => {
@@ -31,26 +32,18 @@ function Make(Ord) {
     hr = typeof r !== "object" ? 0 : r._3;
     if (hl > (hr + 2 | 0)) {
       if (typeof l !== "object") {
-        throw {
-          RE_EXN_ID: "Invalid_argument",
-          _1: "Set.bal",
-          Error: new Error()
-        };
+        return Pervasives.invalid_arg("Set.bal");
       }
       let lr = l._2;
       let lv = l._1;
       let ll = l._0;
       if (height(ll) >= height(lr)) {
         return create(ll, lv, create(lr, v, r));
-      }
-      if (typeof lr === "object") {
+      } else if (typeof lr !== "object") {
+        return Pervasives.invalid_arg("Set.bal");
+      } else {
         return create(create(ll, lv, lr._0), lr._1, create(lr._2, v, r));
       }
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Set.bal",
-        Error: new Error()
-      };
     }
     if (hr <= (hl + 2 | 0)) {
       return {
@@ -62,26 +55,18 @@ function Make(Ord) {
       };
     }
     if (typeof r !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Set.bal",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Set.bal");
     }
     let rr = r._2;
     let rv = r._1;
     let rl = r._0;
     if (height(rr) >= height(rl)) {
       return create(create(l, v, rl), rv, rr);
-    }
-    if (typeof rl === "object") {
+    } else if (typeof rl !== "object") {
+      return Pervasives.invalid_arg("Set.bal");
+    } else {
       return create(create(l, v, rl._0), rl._1, create(rl._2, rv, rr));
     }
-    throw {
-      RE_EXN_ID: "Invalid_argument",
-      _1: "Set.bal",
-      Error: new Error()
-    };
   };
   let add = (x, x_) => {
     if (typeof x_ !== "object") {
@@ -179,11 +164,7 @@ function Make(Ord) {
   };
   let remove_min_elt = x => {
     if (typeof x !== "object") {
-      throw {
-        RE_EXN_ID: "Invalid_argument",
-        _1: "Set.remove_min_elt",
-        Error: new Error()
-      };
+      return Pervasives.invalid_arg("Set.remove_min_elt");
     }
     let l = x._0;
     if (typeof l !== "object") {
diff --git a/tests/tests/src/ticker.js b/tests/tests/src/ticker.js
index d073ec425a..b60ae4edd5 100644
--- a/tests/tests/src/ticker.js
+++ b/tests/tests/src/ticker.js
@@ -155,35 +155,13 @@ function compute_update_sequences(all_tickers) {
     let l$1 = Belt_List.sort(l, (lhs, rhs) => {
       let x = lhs.rank;
       if (typeof x !== "object") {
-        if (x === "Uninitialized") {
-          throw {
-            RE_EXN_ID: "Failure",
-            _1: "All nodes should be ranked",
-            Error: new Error()
-          };
-        }
-        throw {
-          RE_EXN_ID: "Failure",
-          _1: "All nodes should be ranked",
-          Error: new Error()
-        };
+        return Pervasives.failwith("All nodes should be ranked");
+      }
+      let y = rhs.rank;
+      if (typeof y !== "object") {
+        return Pervasives.failwith("All nodes should be ranked");
       } else {
-        let y = rhs.rank;
-        if (typeof y === "object") {
-          return Primitive_int.compare(x._0, y._0);
-        }
-        if (y === "Uninitialized") {
-          throw {
-            RE_EXN_ID: "Failure",
-            _1: "All nodes should be ranked",
-            Error: new Error()
-          };
-        }
-        throw {
-          RE_EXN_ID: "Failure",
-          _1: "All nodes should be ranked",
-          Error: new Error()
-        };
+        return Primitive_int.compare(x._0, y._0);
       }
     });
     return Belt_MapString.set(map, k, l$1);
@@ -198,12 +176,9 @@ function process_quote(ticker_map, new_ticker, new_value) {
       if (ticker.ticker_name === new_ticker) {
         ticker.value = new_value;
         return;
+      } else {
+        return Pervasives.failwith("Only single Market ticker should be udpated upon a new quote");
       }
-      throw {
-        RE_EXN_ID: "Failure",
-        _1: "Only single Market ticker should be udpated upon a new quote",
-        Error: new Error()
-      };
     }
     let match$1 = match._0;
     let match$2 = match$1.lhs.value;
@@ -234,162 +209,96 @@ function process_input_line(ticker_map, all_tickers, line) {
     };
   };
   let tokens = split("|", line);
-  if (tokens) {
-    switch (tokens.hd) {
-      case "Q" :
-        let match = tokens.tl;
-        if (match) {
-          let match$1 = match.tl;
-          if (match$1) {
-            if (match$1.tl) {
-              throw {
-                RE_EXN_ID: "Failure",
-                _1: "Invalid input line",
-                Error: new Error()
-              };
-            }
-            let ticker_map$1 = ticker_map !== undefined ? Primitive_option.valFromOption(ticker_map) : compute_update_sequences(all_tickers);
-            let value = Belt_Option.getExn(Belt_Float.fromString(match$1.hd));
-            process_quote(ticker_map$1, match.hd, value);
+  if (!tokens) {
+    return Pervasives.failwith("Invalid input line");
+  }
+  switch (tokens.hd) {
+    case "Q" :
+      let match = tokens.tl;
+      if (!match) {
+        return Pervasives.failwith("Invalid input line");
+      }
+      let match$1 = match.tl;
+      if (!match$1) {
+        return Pervasives.failwith("Invalid input line");
+      }
+      if (match$1.tl) {
+        return Pervasives.failwith("Invalid input line");
+      }
+      let ticker_map$1 = ticker_map !== undefined ? Primitive_option.valFromOption(ticker_map) : compute_update_sequences(all_tickers);
+      let value = Belt_Option.getExn(Belt_Float.fromString(match$1.hd));
+      process_quote(ticker_map$1, match.hd, value);
+      return [
+        all_tickers,
+        Primitive_option.some(ticker_map$1)
+      ];
+    case "R" :
+      let match$2 = tokens.tl;
+      if (!match$2) {
+        return Pervasives.failwith("Invalid input line");
+      }
+      let match$3 = match$2.tl;
+      if (!match$3) {
+        return Pervasives.failwith("Invalid input line");
+      }
+      let ticker_name = match$2.hd;
+      switch (match$3.hd) {
+        case "+" :
+          let match$4 = match$3.tl;
+          if (!match$4) {
+            return Pervasives.failwith("Invalid input line");
+          }
+          let match$5 = match$4.tl;
+          if (match$5 && !match$5.tl) {
             return [
-              all_tickers,
-              Primitive_option.some(ticker_map$1)
+              {
+                hd: make_binary_op(ticker_name, match$4.hd, match$5.hd, "PLUS"),
+                tl: all_tickers
+              },
+              ticker_map
             ];
+          } else {
+            return Pervasives.failwith("Invalid input line");
           }
-          throw {
-            RE_EXN_ID: "Failure",
-            _1: "Invalid input line",
-            Error: new Error()
-          };
-        }
-        throw {
-          RE_EXN_ID: "Failure",
-          _1: "Invalid input line",
-          Error: new Error()
-        };
-      case "R" :
-        let match$2 = tokens.tl;
-        if (match$2) {
-          let match$3 = match$2.tl;
-          if (match$3) {
-            let ticker_name = match$2.hd;
-            switch (match$3.hd) {
-              case "+" :
-                let match$4 = match$3.tl;
-                if (match$4) {
-                  let match$5 = match$4.tl;
-                  if (match$5) {
-                    if (match$5.tl) {
-                      throw {
-                        RE_EXN_ID: "Failure",
-                        _1: "Invalid input line",
-                        Error: new Error()
-                      };
-                    }
-                    return [
-                      {
-                        hd: make_binary_op(ticker_name, match$4.hd, match$5.hd, "PLUS"),
-                        tl: all_tickers
-                      },
-                      ticker_map
-                    ];
-                  }
-                  throw {
-                    RE_EXN_ID: "Failure",
-                    _1: "Invalid input line",
-                    Error: new Error()
-                  };
-                }
-                throw {
-                  RE_EXN_ID: "Failure",
-                  _1: "Invalid input line",
-                  Error: new Error()
-                };
-              case "-" :
-                let match$6 = match$3.tl;
-                if (match$6) {
-                  let match$7 = match$6.tl;
-                  if (match$7) {
-                    if (match$7.tl) {
-                      throw {
-                        RE_EXN_ID: "Failure",
-                        _1: "Invalid input line",
-                        Error: new Error()
-                      };
-                    }
-                    return [
-                      {
-                        hd: make_binary_op(ticker_name, match$6.hd, match$7.hd, "MINUS"),
-                        tl: all_tickers
-                      },
-                      ticker_map
-                    ];
-                  }
-                  throw {
-                    RE_EXN_ID: "Failure",
-                    _1: "Invalid input line",
-                    Error: new Error()
-                  };
-                }
-                throw {
-                  RE_EXN_ID: "Failure",
-                  _1: "Invalid input line",
-                  Error: new Error()
-                };
-              case "S" :
-                if (match$3.tl) {
-                  throw {
-                    RE_EXN_ID: "Failure",
-                    _1: "Invalid input line",
-                    Error: new Error()
-                  };
-                }
-                return [
-                  {
-                    hd: {
-                      value: undefined,
-                      rank: "Uninitialized",
-                      ticker_name: ticker_name,
-                      type_: "Market"
-                    },
-                    tl: all_tickers
-                  },
-                  ticker_map
-                ];
-              default:
-                throw {
-                  RE_EXN_ID: "Failure",
-                  _1: "Invalid input line",
-                  Error: new Error()
-                };
-            }
+        case "-" :
+          let match$6 = match$3.tl;
+          if (!match$6) {
+            return Pervasives.failwith("Invalid input line");
+          }
+          let match$7 = match$6.tl;
+          if (match$7 && !match$7.tl) {
+            return [
+              {
+                hd: make_binary_op(ticker_name, match$6.hd, match$7.hd, "MINUS"),
+                tl: all_tickers
+              },
+              ticker_map
+            ];
           } else {
-            throw {
-              RE_EXN_ID: "Failure",
-              _1: "Invalid input line",
-              Error: new Error()
-            };
+            return Pervasives.failwith("Invalid input line");
           }
-        } else {
-          throw {
-            RE_EXN_ID: "Failure",
-            _1: "Invalid input line",
-            Error: new Error()
-          };
-        }
-      default:
-        throw {
-          RE_EXN_ID: "Failure",
-          _1: "Invalid input line",
-          Error: new Error()
-        };
-    }
-  } else {
-    throw {
-      RE_EXN_ID: "Failure",
-      _1: "Invalid input line",
-      Error: new Error()
-    };
+        case "S" :
+          if (match$3.tl) {
+            return Pervasives.failwith("Invalid input line");
+          } else {
+            return [
+              {
+                hd: {
+                  value: undefined,
+                  rank: "Uninitialized",
+                  ticker_name: ticker_name,
+                  type_: "Market"
+                },
+                tl: all_tickers
+              },
+              ticker_map
+            ];
+          }
+        default:
+          return Pervasives.failwith("Invalid input line");
+      }
+    default:
+      return Pervasives.failwith("Invalid input line");
   }
 }
 
diff --git a/tests/tests_esmodule/rescript.json b/tests/tests_esmodule/rescript.json
index 7434c44b96..c7dfdd6f05 100644
--- a/tests/tests_esmodule/rescript.json
+++ b/tests/tests_esmodule/rescript.json
@@ -12,7 +12,6 @@
     "suffix": ".mjs"
   },
   "bsc-flags": [
-    "-bs-cross-module-opt",
     "-w -3-6-26-27-29-30-32..40-44-45-52-60-9-106+104",
     "-warn-error A"
   ]