diff --git a/CHANGELOG.md b/CHANGELOG.md
index afe24e625b..12fbd58f77 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -17,6 +17,7 @@
 - Editor: Fix issue where pipe completions would not trigger with generic type arguments. https://github.com/rescript-lang/rescript/pull/7231
 - Fix leftover assert false in code for `null != undefined`. https://github.com/rescript-lang/rescript/pull/7232
 - Editor: Fix issue where completions would not show up inside of object bodies. https://github.com/rescript-lang/rescript/pull/7230
+- Fix issue with pattern matching empty list which interferes with boolean optimisations. https://github.com/rescript-lang/rescript/pull/7237
 
 #### :house: Internal
 
diff --git a/compiler/ml/matching.ml b/compiler/ml/matching.ml
index 2cd1a25db0..03161b8c53 100644
--- a/compiler/ml/matching.ml
+++ b/compiler/ml/matching.ml
@@ -2245,7 +2245,8 @@ let combine_constructor sw_names loc arg ex_pat cstr partial ctx def
           let arg =
             if Datarepr.constructor_has_optional_shape cstr then
               Lprim (Pis_not_none, [arg], loc)
-            else arg
+            else
+              Lprim (Pjscomp Cneq, [arg; Lconst (Const_base (Const_int 0))], loc)
           in
           Lifthenelse (arg, act2, act1)
         | 2, 0, [(i1, act1); (_, act2)], []
diff --git a/lib/es6/Belt_List.js b/lib/es6/Belt_List.js
index 22455cc2e0..f7cf86aa06 100644
--- a/lib/es6/Belt_List.js
+++ b/lib/es6/Belt_List.js
@@ -5,14 +5,14 @@ import * as Belt_SortArray from "./Belt_SortArray.js";
 import * as Primitive_option from "./Primitive_option.js";
 
 function head(x) {
-  if (x) {
+  if (x !== 0) {
     return Primitive_option.some(x.hd);
   }
   
 }
 
 function headExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.hd;
   }
   throw {
@@ -22,14 +22,14 @@ function headExn(x) {
 }
 
 function tail(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   
 }
 
 function tailExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   throw {
@@ -54,7 +54,7 @@ function get(x, n) {
     while (true) {
       let n$1 = _n;
       let x$1 = _x;
-      if (!x$1) {
+      if (x$1 === 0) {
         return;
       }
       if (n$1 === 0) {
@@ -79,7 +79,7 @@ function getExn(x, n) {
   while (true) {
     let n$1 = _n;
     let x$1 = _x;
-    if (x$1) {
+    if (x$1 !== 0) {
       if (n$1 === 0) {
         return x$1.hd;
       }
@@ -99,7 +99,7 @@ function partitionAux(p, _cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let t = cell.tl;
@@ -126,7 +126,7 @@ function splitAux(_cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let match = cell.hd;
@@ -151,7 +151,7 @@ function copyAuxCont(_cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return prec;
     }
     let next = {
@@ -169,7 +169,7 @@ function copyAuxWitFilter(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -194,7 +194,7 @@ function copyAuxWithFilterIndex(f, _cellX, _prec, _i) {
     let i = _i;
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -220,7 +220,7 @@ function copyAuxWitFilterMap(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -244,7 +244,7 @@ function removeAssocAuxWithMap(_cellX, x, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -268,7 +268,7 @@ function setAssocAuxWithMap(_cellX, x, k, _prec, eq) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -298,7 +298,7 @@ function copyAuxWithMap(_cellX, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -317,10 +317,10 @@ function zipAux(_cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -343,10 +343,10 @@ function copyAuxWithMap2(f, _cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -366,7 +366,7 @@ function copyAuxWithMapI(f, _i, _cellX, _prec) {
     let prec = _prec;
     let cellX = _cellX;
     let i = _i;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -389,7 +389,7 @@ function takeAux(_n, _cell, _prec) {
     if (n === 0) {
       return true;
     }
-    if (!cell) {
+    if (cell === 0) {
       return false;
     }
     let cell$1 = {
@@ -412,7 +412,7 @@ function splitAtAux(_n, _cell, _prec) {
     if (n === 0) {
       return cell;
     }
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let cell$1 = {
@@ -434,7 +434,7 @@ function take(lst, n) {
   if (n === 0) {
     return /* [] */0;
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -460,7 +460,7 @@ function drop(lst, n) {
       if (n$1 === 0) {
         return l;
       }
-      if (!l) {
+      if (l === 0) {
         return;
       }
       _n = n$1 - 1 | 0;
@@ -480,7 +480,7 @@ function splitAt(lst, n) {
       lst
     ];
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -498,7 +498,7 @@ function splitAt(lst, n) {
 }
 
 function concat(xs, ys) {
-  if (!xs) {
+  if (xs === 0) {
     return ys;
   }
   let cell = {
@@ -510,7 +510,7 @@ function concat(xs, ys) {
 }
 
 function map(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -522,10 +522,10 @@ function map(xs, f) {
 }
 
 function zipBy(l1, l2, f) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -537,7 +537,7 @@ function zipBy(l1, l2, f) {
 }
 
 function mapWithIndex(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -598,7 +598,7 @@ function length(xs) {
   while (true) {
     let acc = _acc;
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return acc;
     }
     _acc = acc + 1 | 0;
@@ -611,7 +611,7 @@ function fillAux(arr, _i, _x) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     arr[i] = x.hd;
@@ -656,7 +656,7 @@ function reverseConcat(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -676,7 +676,7 @@ function flattenAux(_prec, _xs) {
   while (true) {
     let xs = _xs;
     let prec = _prec;
-    if (xs) {
+    if (xs !== 0) {
       _xs = xs.tl;
       _prec = copyAuxCont(xs.hd, prec);
       continue;
@@ -689,11 +689,11 @@ function flattenAux(_prec, _xs) {
 function flatten(_xs) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let match = xs.hd;
-    if (match) {
+    if (match !== 0) {
       let cell = {
         hd: match.hd,
         tl: /* [] */0
@@ -728,7 +728,7 @@ function mapReverse(l, f) {
   while (true) {
     let xs = _xs;
     let accu = _accu;
-    if (!xs) {
+    if (xs === 0) {
       return accu;
     }
     _xs = xs.tl;
@@ -743,7 +743,7 @@ function mapReverse(l, f) {
 function forEach(_xs, f) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd);
@@ -758,7 +758,7 @@ function forEachWithIndex(l, f) {
   while (true) {
     let i = _i;
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(i, xs.hd);
@@ -772,7 +772,7 @@ function reduce(_l, _accu, f) {
   while (true) {
     let accu = _accu;
     let l = _l;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _accu = f(accu, l.hd);
@@ -782,7 +782,7 @@ function reduce(_l, _accu, f) {
 }
 
 function reduceReverseUnsafe(l, accu, f) {
-  if (l) {
+  if (l !== 0) {
     return f(reduceReverseUnsafe(l.tl, accu, f), l.hd);
   } else {
     return accu;
@@ -806,7 +806,7 @@ function reduceWithIndex(l, acc, f) {
     let i = _i;
     let acc$1 = _acc;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return acc$1;
     }
     _i = i + 1 | 0;
@@ -824,10 +824,10 @@ function mapReverse2(l1, l2, f) {
     let accu = _accu;
     let l2$1 = _l2;
     let l1$1 = _l1;
-    if (!l1$1) {
+    if (l1$1 === 0) {
       return accu;
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return accu;
     }
     _accu = {
@@ -844,10 +844,10 @@ function forEach2(_l1, _l2, f) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return;
     }
     f(l1.hd, l2.hd);
@@ -862,10 +862,10 @@ function reduce2(_l1, _l2, _accu, f) {
     let accu = _accu;
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return accu;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return accu;
     }
     _accu = f(accu, l1.hd, l2.hd);
@@ -876,7 +876,7 @@ function reduce2(_l1, _l2, _accu, f) {
 }
 
 function reduceReverse2Unsafe(l1, l2, accu, f) {
-  if (l1 && l2) {
+  if (l1 !== 0 && l2 !== 0) {
     return f(reduceReverse2Unsafe(l1.tl, l2.tl, accu, f), l1.hd, l2.hd);
   } else {
     return accu;
@@ -895,7 +895,7 @@ function reduceReverse2(l1, l2, acc, f) {
 function every(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return true;
     }
     if (!p(xs.hd)) {
@@ -909,7 +909,7 @@ function every(_xs, p) {
 function some(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (p(xs.hd)) {
@@ -924,10 +924,10 @@ function every2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return true;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return true;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -943,14 +943,14 @@ function cmpByLength(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     _l2 = l2.tl;
@@ -963,14 +963,14 @@ function cmp(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     let c = p(l1.hd, l2.hd);
@@ -987,10 +987,10 @@ function eq(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      return !l2;
+    if (l1 === 0) {
+      return l2 === 0;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -1006,10 +1006,10 @@ function some2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return false;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (p(l1.hd, l2.hd)) {
@@ -1024,7 +1024,7 @@ function some2(_l1, _l2, p) {
 function has(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd, x)) {
@@ -1038,7 +1038,7 @@ function has(_xs, x, eq) {
 function getAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let match = xs.hd;
@@ -1053,7 +1053,7 @@ function getAssoc(_xs, x, eq) {
 function hasAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd[0], x)) {
@@ -1065,7 +1065,7 @@ function hasAssoc(_xs, x, eq) {
 }
 
 function removeAssoc(xs, x, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let l = xs.tl;
@@ -1086,7 +1086,7 @@ function removeAssoc(xs, x, eq) {
 }
 
 function setAssoc(xs, x, k, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return {
       hd: [
         x,
@@ -1133,7 +1133,7 @@ function sort(xs, cmp) {
 function getBy(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let x = xs.hd;
@@ -1148,7 +1148,7 @@ function getBy(_xs, p) {
 function keep(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1172,7 +1172,7 @@ function keepWithIndex(xs, p) {
   while (true) {
     let i = _i;
     let xs$1 = _xs;
-    if (!xs$1) {
+    if (xs$1 === 0) {
       return /* [] */0;
     }
     let t = xs$1.tl;
@@ -1194,7 +1194,7 @@ function keepWithIndex(xs, p) {
 function keepMap(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1213,7 +1213,7 @@ function keepMap(_xs, p) {
 }
 
 function partition(l, p) {
-  if (!l) {
+  if (l === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1244,7 +1244,7 @@ function partition(l, p) {
 }
 
 function unzip(xs) {
-  if (!xs) {
+  if (xs === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1267,10 +1267,10 @@ function unzip(xs) {
 }
 
 function zip(l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
diff --git a/lib/es6/Belt_internalAVLset.js b/lib/es6/Belt_internalAVLset.js
index bcc1ca58f8..c96f412eb4 100644
--- a/lib/es6/Belt_internalAVLset.js
+++ b/lib/es6/Belt_internalAVLset.js
@@ -589,10 +589,10 @@ function cmp(s1, s2, cmp$1) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return 0;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return 0;
       }
       let h2 = e2.hd;
diff --git a/lib/es6/Belt_internalAVLtree.js b/lib/es6/Belt_internalAVLtree.js
index c5454dafda..0745420221 100644
--- a/lib/es6/Belt_internalAVLtree.js
+++ b/lib/es6/Belt_internalAVLtree.js
@@ -749,10 +749,10 @@ function cmp(s1, s2, kcmp, vcmp) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return 0;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return 0;
       }
       let h2 = e2.hd;
@@ -785,10 +785,10 @@ function eq(s1, s2, kcmp, veq) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return true;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return true;
       }
       let h2 = e2.hd;
diff --git a/lib/es6/Belt_internalMapInt.js b/lib/es6/Belt_internalMapInt.js
index 698255f843..292662c21a 100644
--- a/lib/es6/Belt_internalMapInt.js
+++ b/lib/es6/Belt_internalMapInt.js
@@ -211,10 +211,10 @@ function compareAux(_e1, _e2, vcmp) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
@@ -249,10 +249,10 @@ function eqAux(_e1, _e2, eq) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return true;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return true;
     }
     let h2 = e2.hd;
diff --git a/lib/es6/Belt_internalMapString.js b/lib/es6/Belt_internalMapString.js
index 9083d62782..a156d6bc44 100644
--- a/lib/es6/Belt_internalMapString.js
+++ b/lib/es6/Belt_internalMapString.js
@@ -211,10 +211,10 @@ function compareAux(_e1, _e2, vcmp) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
@@ -249,10 +249,10 @@ function eqAux(_e1, _e2, eq) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return true;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return true;
     }
     let h2 = e2.hd;
diff --git a/lib/es6/Belt_internalSetInt.js b/lib/es6/Belt_internalSetInt.js
index d3cf1d8a5e..53d46e6d7e 100644
--- a/lib/es6/Belt_internalSetInt.js
+++ b/lib/es6/Belt_internalSetInt.js
@@ -22,10 +22,10 @@ function compareAux(_e1, _e2) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
diff --git a/lib/es6/Belt_internalSetString.js b/lib/es6/Belt_internalSetString.js
index 0fa49af7c1..75c0c3e8da 100644
--- a/lib/es6/Belt_internalSetString.js
+++ b/lib/es6/Belt_internalSetString.js
@@ -22,10 +22,10 @@ function compareAux(_e1, _e2) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
diff --git a/lib/es6/Js_dict.js b/lib/es6/Js_dict.js
index 4c1c6bcd65..3e56207162 100644
--- a/lib/es6/Js_dict.js
+++ b/lib/es6/Js_dict.js
@@ -42,7 +42,7 @@ function fromList(entries) {
   let _x = entries;
   while (true) {
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return dict;
     }
     let match = x.hd;
diff --git a/lib/es6/List.js b/lib/es6/List.js
index 06760467a5..2b0f6cd7d2 100644
--- a/lib/es6/List.js
+++ b/lib/es6/List.js
@@ -5,14 +5,14 @@ import * as Primitive_int from "./Primitive_int.js";
 import * as Primitive_option from "./Primitive_option.js";
 
 function head(x) {
-  if (x) {
+  if (x !== 0) {
     return Primitive_option.some(x.hd);
   }
   
 }
 
 function headExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.hd;
   }
   throw {
@@ -22,14 +22,14 @@ function headExn(x) {
 }
 
 function tail(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   
 }
 
 function tailExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   throw {
@@ -54,7 +54,7 @@ function get(x, n) {
     while (true) {
       let n$1 = _n;
       let x$1 = _x;
-      if (!x$1) {
+      if (x$1 === 0) {
         return;
       }
       if (n$1 === 0) {
@@ -79,7 +79,7 @@ function getExn(x, n) {
   while (true) {
     let n$1 = _n;
     let x$1 = _x;
-    if (x$1) {
+    if (x$1 !== 0) {
       if (n$1 === 0) {
         return x$1.hd;
       }
@@ -99,7 +99,7 @@ function partitionAux(p, _cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let t = cell.tl;
@@ -126,7 +126,7 @@ function splitAux(_cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let match = cell.hd;
@@ -151,7 +151,7 @@ function copyAuxCont(_cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return prec;
     }
     let next = {
@@ -169,7 +169,7 @@ function copyAuxWitFilter(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -194,7 +194,7 @@ function copyAuxWithFilterIndex(f, _cellX, _prec, _i) {
     let i = _i;
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -220,7 +220,7 @@ function copyAuxWitFilterMap(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -244,7 +244,7 @@ function removeAssocAuxWithMap(_cellX, x, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -268,7 +268,7 @@ function setAssocAuxWithMap(_cellX, x, k, _prec, eq) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -298,7 +298,7 @@ function copyAuxWithMap(_cellX, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -317,10 +317,10 @@ function zipAux(_cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -343,10 +343,10 @@ function copyAuxWithMap2(f, _cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -366,7 +366,7 @@ function copyAuxWithMapI(f, _i, _cellX, _prec) {
     let prec = _prec;
     let cellX = _cellX;
     let i = _i;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -389,7 +389,7 @@ function takeAux(_n, _cell, _prec) {
     if (n === 0) {
       return true;
     }
-    if (!cell) {
+    if (cell === 0) {
       return false;
     }
     let cell$1 = {
@@ -412,7 +412,7 @@ function splitAtAux(_n, _cell, _prec) {
     if (n === 0) {
       return cell;
     }
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let cell$1 = {
@@ -434,7 +434,7 @@ function take(lst, n) {
   if (n === 0) {
     return /* [] */0;
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -460,7 +460,7 @@ function drop(lst, n) {
       if (n$1 === 0) {
         return l;
       }
-      if (!l) {
+      if (l === 0) {
         return;
       }
       _n = n$1 - 1 | 0;
@@ -480,7 +480,7 @@ function splitAt(lst, n) {
       lst
     ];
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -498,7 +498,7 @@ function splitAt(lst, n) {
 }
 
 function concat(xs, ys) {
-  if (!xs) {
+  if (xs === 0) {
     return ys;
   }
   let cell = {
@@ -510,7 +510,7 @@ function concat(xs, ys) {
 }
 
 function map(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -522,10 +522,10 @@ function map(xs, f) {
 }
 
 function zipBy(l1, l2, f) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -537,7 +537,7 @@ function zipBy(l1, l2, f) {
 }
 
 function mapWithIndex(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -598,7 +598,7 @@ function length(xs) {
   while (true) {
     let acc = _acc;
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return acc;
     }
     _acc = acc + 1 | 0;
@@ -611,7 +611,7 @@ function fillAux(arr, _i, _x) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     arr[i] = x.hd;
@@ -656,7 +656,7 @@ function reverseConcat(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -676,7 +676,7 @@ function flatAux(_prec, _xs) {
   while (true) {
     let xs = _xs;
     let prec = _prec;
-    if (xs) {
+    if (xs !== 0) {
       _xs = xs.tl;
       _prec = copyAuxCont(xs.hd, prec);
       continue;
@@ -689,11 +689,11 @@ function flatAux(_prec, _xs) {
 function flat(_xs) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let match = xs.hd;
-    if (match) {
+    if (match !== 0) {
       let cell = {
         hd: match.hd,
         tl: /* [] */0
@@ -728,7 +728,7 @@ function mapReverse(l, f) {
   while (true) {
     let xs = _xs;
     let accu = _accu;
-    if (!xs) {
+    if (xs === 0) {
       return accu;
     }
     _xs = xs.tl;
@@ -743,7 +743,7 @@ function mapReverse(l, f) {
 function forEach(_xs, f) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd);
@@ -758,7 +758,7 @@ function forEachWithIndex(l, f) {
   while (true) {
     let i = _i;
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd, i);
@@ -772,7 +772,7 @@ function reduce(_l, _accu, f) {
   while (true) {
     let accu = _accu;
     let l = _l;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _accu = f(accu, l.hd);
@@ -782,7 +782,7 @@ function reduce(_l, _accu, f) {
 }
 
 function reduceReverseUnsafe(l, accu, f) {
-  if (l) {
+  if (l !== 0) {
     return f(reduceReverseUnsafe(l.tl, accu, f), l.hd);
   } else {
     return accu;
@@ -811,7 +811,7 @@ function reduceWithIndex(l, acc, f) {
     let i = _i;
     let acc$1 = _acc;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return acc$1;
     }
     _i = i + 1 | 0;
@@ -829,10 +829,10 @@ function mapReverse2(l1, l2, f) {
     let accu = _accu;
     let l2$1 = _l2;
     let l1$1 = _l1;
-    if (!l1$1) {
+    if (l1$1 === 0) {
       return accu;
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return accu;
     }
     _accu = {
@@ -849,10 +849,10 @@ function forEach2(_l1, _l2, f) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return;
     }
     f(l1.hd, l2.hd);
@@ -867,10 +867,10 @@ function reduce2(_l1, _l2, _accu, f) {
     let accu = _accu;
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return accu;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return accu;
     }
     _accu = f(accu, l1.hd, l2.hd);
@@ -881,7 +881,7 @@ function reduce2(_l1, _l2, _accu, f) {
 }
 
 function reduceReverse2Unsafe(l1, l2, accu, f) {
-  if (l1 && l2) {
+  if (l1 !== 0 && l2 !== 0) {
     return f(reduceReverse2Unsafe(l1.tl, l2.tl, accu, f), l1.hd, l2.hd);
   } else {
     return accu;
@@ -907,7 +907,7 @@ function reduceReverse2(l1, l2, acc, f) {
 function every(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return true;
     }
     if (!p(xs.hd)) {
@@ -921,7 +921,7 @@ function every(_xs, p) {
 function some(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (p(xs.hd)) {
@@ -936,10 +936,10 @@ function every2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return true;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return true;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -955,14 +955,14 @@ function compareLength(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     _l2 = l2.tl;
@@ -975,14 +975,14 @@ function compare(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     let c = p(l1.hd, l2.hd);
@@ -999,10 +999,10 @@ function equal(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      return !l2;
+    if (l1 === 0) {
+      return l2 === 0;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -1018,10 +1018,10 @@ function some2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return false;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (p(l1.hd, l2.hd)) {
@@ -1036,7 +1036,7 @@ function some2(_l1, _l2, p) {
 function has(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd, x)) {
@@ -1050,7 +1050,7 @@ function has(_xs, x, eq) {
 function getAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let match = xs.hd;
@@ -1065,7 +1065,7 @@ function getAssoc(_xs, x, eq) {
 function hasAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd[0], x)) {
@@ -1077,7 +1077,7 @@ function hasAssoc(_xs, x, eq) {
 }
 
 function removeAssoc(xs, x, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let l = xs.tl;
@@ -1098,7 +1098,7 @@ function removeAssoc(xs, x, eq) {
 }
 
 function setAssoc(xs, x, k, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return {
       hd: [
         x,
@@ -1145,7 +1145,7 @@ function sort(xs, cmp) {
 function find(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let x = xs.hd;
@@ -1160,7 +1160,7 @@ function find(_xs, p) {
 function filter(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1184,7 +1184,7 @@ function filterWithIndex(xs, p) {
   while (true) {
     let i = _i;
     let xs$1 = _xs;
-    if (!xs$1) {
+    if (xs$1 === 0) {
       return /* [] */0;
     }
     let t = xs$1.tl;
@@ -1206,7 +1206,7 @@ function filterWithIndex(xs, p) {
 function filterMap(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1225,7 +1225,7 @@ function filterMap(_xs, p) {
 }
 
 function partition(l, p) {
-  if (!l) {
+  if (l === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1256,7 +1256,7 @@ function partition(l, p) {
 }
 
 function unzip(xs) {
-  if (!xs) {
+  if (xs === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1279,10 +1279,10 @@ function unzip(xs) {
 }
 
 function zip(l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
diff --git a/lib/es6/Pervasives.js b/lib/es6/Pervasives.js
index 5c493d7ea9..65fe437b38 100644
--- a/lib/es6/Pervasives.js
+++ b/lib/es6/Pervasives.js
@@ -107,7 +107,7 @@ function int_of_string_opt(s) {
 }
 
 function $at(l1, l2) {
-  if (l1) {
+  if (l1 !== 0) {
     return {
       hd: l1.hd,
       tl: $at(l1.tl, l2)
diff --git a/lib/js/Belt_List.js b/lib/js/Belt_List.js
index 2d9f0e17ec..0dd1ac9145 100644
--- a/lib/js/Belt_List.js
+++ b/lib/js/Belt_List.js
@@ -5,14 +5,14 @@ let Belt_SortArray = require("./Belt_SortArray.js");
 let Primitive_option = require("./Primitive_option.js");
 
 function head(x) {
-  if (x) {
+  if (x !== 0) {
     return Primitive_option.some(x.hd);
   }
   
 }
 
 function headExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.hd;
   }
   throw {
@@ -22,14 +22,14 @@ function headExn(x) {
 }
 
 function tail(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   
 }
 
 function tailExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   throw {
@@ -54,7 +54,7 @@ function get(x, n) {
     while (true) {
       let n$1 = _n;
       let x$1 = _x;
-      if (!x$1) {
+      if (x$1 === 0) {
         return;
       }
       if (n$1 === 0) {
@@ -79,7 +79,7 @@ function getExn(x, n) {
   while (true) {
     let n$1 = _n;
     let x$1 = _x;
-    if (x$1) {
+    if (x$1 !== 0) {
       if (n$1 === 0) {
         return x$1.hd;
       }
@@ -99,7 +99,7 @@ function partitionAux(p, _cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let t = cell.tl;
@@ -126,7 +126,7 @@ function splitAux(_cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let match = cell.hd;
@@ -151,7 +151,7 @@ function copyAuxCont(_cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return prec;
     }
     let next = {
@@ -169,7 +169,7 @@ function copyAuxWitFilter(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -194,7 +194,7 @@ function copyAuxWithFilterIndex(f, _cellX, _prec, _i) {
     let i = _i;
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -220,7 +220,7 @@ function copyAuxWitFilterMap(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -244,7 +244,7 @@ function removeAssocAuxWithMap(_cellX, x, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -268,7 +268,7 @@ function setAssocAuxWithMap(_cellX, x, k, _prec, eq) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -298,7 +298,7 @@ function copyAuxWithMap(_cellX, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -317,10 +317,10 @@ function zipAux(_cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -343,10 +343,10 @@ function copyAuxWithMap2(f, _cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -366,7 +366,7 @@ function copyAuxWithMapI(f, _i, _cellX, _prec) {
     let prec = _prec;
     let cellX = _cellX;
     let i = _i;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -389,7 +389,7 @@ function takeAux(_n, _cell, _prec) {
     if (n === 0) {
       return true;
     }
-    if (!cell) {
+    if (cell === 0) {
       return false;
     }
     let cell$1 = {
@@ -412,7 +412,7 @@ function splitAtAux(_n, _cell, _prec) {
     if (n === 0) {
       return cell;
     }
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let cell$1 = {
@@ -434,7 +434,7 @@ function take(lst, n) {
   if (n === 0) {
     return /* [] */0;
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -460,7 +460,7 @@ function drop(lst, n) {
       if (n$1 === 0) {
         return l;
       }
-      if (!l) {
+      if (l === 0) {
         return;
       }
       _n = n$1 - 1 | 0;
@@ -480,7 +480,7 @@ function splitAt(lst, n) {
       lst
     ];
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -498,7 +498,7 @@ function splitAt(lst, n) {
 }
 
 function concat(xs, ys) {
-  if (!xs) {
+  if (xs === 0) {
     return ys;
   }
   let cell = {
@@ -510,7 +510,7 @@ function concat(xs, ys) {
 }
 
 function map(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -522,10 +522,10 @@ function map(xs, f) {
 }
 
 function zipBy(l1, l2, f) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -537,7 +537,7 @@ function zipBy(l1, l2, f) {
 }
 
 function mapWithIndex(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -598,7 +598,7 @@ function length(xs) {
   while (true) {
     let acc = _acc;
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return acc;
     }
     _acc = acc + 1 | 0;
@@ -611,7 +611,7 @@ function fillAux(arr, _i, _x) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     arr[i] = x.hd;
@@ -656,7 +656,7 @@ function reverseConcat(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -676,7 +676,7 @@ function flattenAux(_prec, _xs) {
   while (true) {
     let xs = _xs;
     let prec = _prec;
-    if (xs) {
+    if (xs !== 0) {
       _xs = xs.tl;
       _prec = copyAuxCont(xs.hd, prec);
       continue;
@@ -689,11 +689,11 @@ function flattenAux(_prec, _xs) {
 function flatten(_xs) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let match = xs.hd;
-    if (match) {
+    if (match !== 0) {
       let cell = {
         hd: match.hd,
         tl: /* [] */0
@@ -728,7 +728,7 @@ function mapReverse(l, f) {
   while (true) {
     let xs = _xs;
     let accu = _accu;
-    if (!xs) {
+    if (xs === 0) {
       return accu;
     }
     _xs = xs.tl;
@@ -743,7 +743,7 @@ function mapReverse(l, f) {
 function forEach(_xs, f) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd);
@@ -758,7 +758,7 @@ function forEachWithIndex(l, f) {
   while (true) {
     let i = _i;
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(i, xs.hd);
@@ -772,7 +772,7 @@ function reduce(_l, _accu, f) {
   while (true) {
     let accu = _accu;
     let l = _l;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _accu = f(accu, l.hd);
@@ -782,7 +782,7 @@ function reduce(_l, _accu, f) {
 }
 
 function reduceReverseUnsafe(l, accu, f) {
-  if (l) {
+  if (l !== 0) {
     return f(reduceReverseUnsafe(l.tl, accu, f), l.hd);
   } else {
     return accu;
@@ -806,7 +806,7 @@ function reduceWithIndex(l, acc, f) {
     let i = _i;
     let acc$1 = _acc;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return acc$1;
     }
     _i = i + 1 | 0;
@@ -824,10 +824,10 @@ function mapReverse2(l1, l2, f) {
     let accu = _accu;
     let l2$1 = _l2;
     let l1$1 = _l1;
-    if (!l1$1) {
+    if (l1$1 === 0) {
       return accu;
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return accu;
     }
     _accu = {
@@ -844,10 +844,10 @@ function forEach2(_l1, _l2, f) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return;
     }
     f(l1.hd, l2.hd);
@@ -862,10 +862,10 @@ function reduce2(_l1, _l2, _accu, f) {
     let accu = _accu;
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return accu;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return accu;
     }
     _accu = f(accu, l1.hd, l2.hd);
@@ -876,7 +876,7 @@ function reduce2(_l1, _l2, _accu, f) {
 }
 
 function reduceReverse2Unsafe(l1, l2, accu, f) {
-  if (l1 && l2) {
+  if (l1 !== 0 && l2 !== 0) {
     return f(reduceReverse2Unsafe(l1.tl, l2.tl, accu, f), l1.hd, l2.hd);
   } else {
     return accu;
@@ -895,7 +895,7 @@ function reduceReverse2(l1, l2, acc, f) {
 function every(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return true;
     }
     if (!p(xs.hd)) {
@@ -909,7 +909,7 @@ function every(_xs, p) {
 function some(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (p(xs.hd)) {
@@ -924,10 +924,10 @@ function every2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return true;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return true;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -943,14 +943,14 @@ function cmpByLength(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     _l2 = l2.tl;
@@ -963,14 +963,14 @@ function cmp(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     let c = p(l1.hd, l2.hd);
@@ -987,10 +987,10 @@ function eq(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      return !l2;
+    if (l1 === 0) {
+      return l2 === 0;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -1006,10 +1006,10 @@ function some2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return false;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (p(l1.hd, l2.hd)) {
@@ -1024,7 +1024,7 @@ function some2(_l1, _l2, p) {
 function has(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd, x)) {
@@ -1038,7 +1038,7 @@ function has(_xs, x, eq) {
 function getAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let match = xs.hd;
@@ -1053,7 +1053,7 @@ function getAssoc(_xs, x, eq) {
 function hasAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd[0], x)) {
@@ -1065,7 +1065,7 @@ function hasAssoc(_xs, x, eq) {
 }
 
 function removeAssoc(xs, x, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let l = xs.tl;
@@ -1086,7 +1086,7 @@ function removeAssoc(xs, x, eq) {
 }
 
 function setAssoc(xs, x, k, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return {
       hd: [
         x,
@@ -1133,7 +1133,7 @@ function sort(xs, cmp) {
 function getBy(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let x = xs.hd;
@@ -1148,7 +1148,7 @@ function getBy(_xs, p) {
 function keep(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1172,7 +1172,7 @@ function keepWithIndex(xs, p) {
   while (true) {
     let i = _i;
     let xs$1 = _xs;
-    if (!xs$1) {
+    if (xs$1 === 0) {
       return /* [] */0;
     }
     let t = xs$1.tl;
@@ -1194,7 +1194,7 @@ function keepWithIndex(xs, p) {
 function keepMap(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1213,7 +1213,7 @@ function keepMap(_xs, p) {
 }
 
 function partition(l, p) {
-  if (!l) {
+  if (l === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1244,7 +1244,7 @@ function partition(l, p) {
 }
 
 function unzip(xs) {
-  if (!xs) {
+  if (xs === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1267,10 +1267,10 @@ function unzip(xs) {
 }
 
 function zip(l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
diff --git a/lib/js/Belt_internalAVLset.js b/lib/js/Belt_internalAVLset.js
index 6e17ca2e5f..ccffdcd473 100644
--- a/lib/js/Belt_internalAVLset.js
+++ b/lib/js/Belt_internalAVLset.js
@@ -589,10 +589,10 @@ function cmp(s1, s2, cmp$1) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return 0;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return 0;
       }
       let h2 = e2.hd;
diff --git a/lib/js/Belt_internalAVLtree.js b/lib/js/Belt_internalAVLtree.js
index 278f2a4141..b0b3d3f3e5 100644
--- a/lib/js/Belt_internalAVLtree.js
+++ b/lib/js/Belt_internalAVLtree.js
@@ -749,10 +749,10 @@ function cmp(s1, s2, kcmp, vcmp) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return 0;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return 0;
       }
       let h2 = e2.hd;
@@ -785,10 +785,10 @@ function eq(s1, s2, kcmp, veq) {
     while (true) {
       let e2 = _e2;
       let e1 = _e1;
-      if (!e1) {
+      if (e1 === 0) {
         return true;
       }
-      if (!e2) {
+      if (e2 === 0) {
         return true;
       }
       let h2 = e2.hd;
diff --git a/lib/js/Belt_internalMapInt.js b/lib/js/Belt_internalMapInt.js
index 2bf62458d1..ed9658e9bb 100644
--- a/lib/js/Belt_internalMapInt.js
+++ b/lib/js/Belt_internalMapInt.js
@@ -211,10 +211,10 @@ function compareAux(_e1, _e2, vcmp) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
@@ -249,10 +249,10 @@ function eqAux(_e1, _e2, eq) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return true;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return true;
     }
     let h2 = e2.hd;
diff --git a/lib/js/Belt_internalMapString.js b/lib/js/Belt_internalMapString.js
index 6d75fd58be..e648ebefd7 100644
--- a/lib/js/Belt_internalMapString.js
+++ b/lib/js/Belt_internalMapString.js
@@ -211,10 +211,10 @@ function compareAux(_e1, _e2, vcmp) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
@@ -249,10 +249,10 @@ function eqAux(_e1, _e2, eq) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return true;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return true;
     }
     let h2 = e2.hd;
diff --git a/lib/js/Belt_internalSetInt.js b/lib/js/Belt_internalSetInt.js
index b6812e6e55..093dca6bd1 100644
--- a/lib/js/Belt_internalSetInt.js
+++ b/lib/js/Belt_internalSetInt.js
@@ -22,10 +22,10 @@ function compareAux(_e1, _e2) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
diff --git a/lib/js/Belt_internalSetString.js b/lib/js/Belt_internalSetString.js
index ec5c44986f..d08cce4212 100644
--- a/lib/js/Belt_internalSetString.js
+++ b/lib/js/Belt_internalSetString.js
@@ -22,10 +22,10 @@ function compareAux(_e1, _e2) {
   while (true) {
     let e2 = _e2;
     let e1 = _e1;
-    if (!e1) {
+    if (e1 === 0) {
       return 0;
     }
-    if (!e2) {
+    if (e2 === 0) {
       return 0;
     }
     let h2 = e2.hd;
diff --git a/lib/js/Js_dict.js b/lib/js/Js_dict.js
index 5b434b5b41..d696550db9 100644
--- a/lib/js/Js_dict.js
+++ b/lib/js/Js_dict.js
@@ -42,7 +42,7 @@ function fromList(entries) {
   let _x = entries;
   while (true) {
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return dict;
     }
     let match = x.hd;
diff --git a/lib/js/List.js b/lib/js/List.js
index 8e8cd35fbc..b11ab0d3ff 100644
--- a/lib/js/List.js
+++ b/lib/js/List.js
@@ -5,14 +5,14 @@ let Primitive_int = require("./Primitive_int.js");
 let Primitive_option = require("./Primitive_option.js");
 
 function head(x) {
-  if (x) {
+  if (x !== 0) {
     return Primitive_option.some(x.hd);
   }
   
 }
 
 function headExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.hd;
   }
   throw {
@@ -22,14 +22,14 @@ function headExn(x) {
 }
 
 function tail(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   
 }
 
 function tailExn(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   }
   throw {
@@ -54,7 +54,7 @@ function get(x, n) {
     while (true) {
       let n$1 = _n;
       let x$1 = _x;
-      if (!x$1) {
+      if (x$1 === 0) {
         return;
       }
       if (n$1 === 0) {
@@ -79,7 +79,7 @@ function getExn(x, n) {
   while (true) {
     let n$1 = _n;
     let x$1 = _x;
-    if (x$1) {
+    if (x$1 !== 0) {
       if (n$1 === 0) {
         return x$1.hd;
       }
@@ -99,7 +99,7 @@ function partitionAux(p, _cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let t = cell.tl;
@@ -126,7 +126,7 @@ function splitAux(_cell, _precX, _precY) {
     let precY = _precY;
     let precX = _precX;
     let cell = _cell;
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let match = cell.hd;
@@ -151,7 +151,7 @@ function copyAuxCont(_cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return prec;
     }
     let next = {
@@ -169,7 +169,7 @@ function copyAuxWitFilter(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -194,7 +194,7 @@ function copyAuxWithFilterIndex(f, _cellX, _prec, _i) {
     let i = _i;
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -220,7 +220,7 @@ function copyAuxWitFilterMap(f, _cellX, _prec) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let t = cellX.tl;
@@ -244,7 +244,7 @@ function removeAssocAuxWithMap(_cellX, x, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -268,7 +268,7 @@ function setAssocAuxWithMap(_cellX, x, k, _prec, eq) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return false;
     }
     let t = cellX.tl;
@@ -298,7 +298,7 @@ function copyAuxWithMap(_cellX, _prec, f) {
   while (true) {
     let prec = _prec;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -317,10 +317,10 @@ function zipAux(_cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -343,10 +343,10 @@ function copyAuxWithMap2(f, _cellX, _cellY, _prec) {
     let prec = _prec;
     let cellY = _cellY;
     let cellX = _cellX;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
-    if (!cellY) {
+    if (cellY === 0) {
       return;
     }
     let next = {
@@ -366,7 +366,7 @@ function copyAuxWithMapI(f, _i, _cellX, _prec) {
     let prec = _prec;
     let cellX = _cellX;
     let i = _i;
-    if (!cellX) {
+    if (cellX === 0) {
       return;
     }
     let next = {
@@ -389,7 +389,7 @@ function takeAux(_n, _cell, _prec) {
     if (n === 0) {
       return true;
     }
-    if (!cell) {
+    if (cell === 0) {
       return false;
     }
     let cell$1 = {
@@ -412,7 +412,7 @@ function splitAtAux(_n, _cell, _prec) {
     if (n === 0) {
       return cell;
     }
-    if (!cell) {
+    if (cell === 0) {
       return;
     }
     let cell$1 = {
@@ -434,7 +434,7 @@ function take(lst, n) {
   if (n === 0) {
     return /* [] */0;
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -460,7 +460,7 @@ function drop(lst, n) {
       if (n$1 === 0) {
         return l;
       }
-      if (!l) {
+      if (l === 0) {
         return;
       }
       _n = n$1 - 1 | 0;
@@ -480,7 +480,7 @@ function splitAt(lst, n) {
       lst
     ];
   }
-  if (!lst) {
+  if (lst === 0) {
     return;
   }
   let cell = {
@@ -498,7 +498,7 @@ function splitAt(lst, n) {
 }
 
 function concat(xs, ys) {
-  if (!xs) {
+  if (xs === 0) {
     return ys;
   }
   let cell = {
@@ -510,7 +510,7 @@ function concat(xs, ys) {
 }
 
 function map(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -522,10 +522,10 @@ function map(xs, f) {
 }
 
 function zipBy(l1, l2, f) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -537,7 +537,7 @@ function zipBy(l1, l2, f) {
 }
 
 function mapWithIndex(xs, f) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let cell = {
@@ -598,7 +598,7 @@ function length(xs) {
   while (true) {
     let acc = _acc;
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return acc;
     }
     _acc = acc + 1 | 0;
@@ -611,7 +611,7 @@ function fillAux(arr, _i, _x) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     arr[i] = x.hd;
@@ -656,7 +656,7 @@ function reverseConcat(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -676,7 +676,7 @@ function flatAux(_prec, _xs) {
   while (true) {
     let xs = _xs;
     let prec = _prec;
-    if (xs) {
+    if (xs !== 0) {
       _xs = xs.tl;
       _prec = copyAuxCont(xs.hd, prec);
       continue;
@@ -689,11 +689,11 @@ function flatAux(_prec, _xs) {
 function flat(_xs) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let match = xs.hd;
-    if (match) {
+    if (match !== 0) {
       let cell = {
         hd: match.hd,
         tl: /* [] */0
@@ -728,7 +728,7 @@ function mapReverse(l, f) {
   while (true) {
     let xs = _xs;
     let accu = _accu;
-    if (!xs) {
+    if (xs === 0) {
       return accu;
     }
     _xs = xs.tl;
@@ -743,7 +743,7 @@ function mapReverse(l, f) {
 function forEach(_xs, f) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd);
@@ -758,7 +758,7 @@ function forEachWithIndex(l, f) {
   while (true) {
     let i = _i;
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     f(xs.hd, i);
@@ -772,7 +772,7 @@ function reduce(_l, _accu, f) {
   while (true) {
     let accu = _accu;
     let l = _l;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _accu = f(accu, l.hd);
@@ -782,7 +782,7 @@ function reduce(_l, _accu, f) {
 }
 
 function reduceReverseUnsafe(l, accu, f) {
-  if (l) {
+  if (l !== 0) {
     return f(reduceReverseUnsafe(l.tl, accu, f), l.hd);
   } else {
     return accu;
@@ -811,7 +811,7 @@ function reduceWithIndex(l, acc, f) {
     let i = _i;
     let acc$1 = _acc;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return acc$1;
     }
     _i = i + 1 | 0;
@@ -829,10 +829,10 @@ function mapReverse2(l1, l2, f) {
     let accu = _accu;
     let l2$1 = _l2;
     let l1$1 = _l1;
-    if (!l1$1) {
+    if (l1$1 === 0) {
       return accu;
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return accu;
     }
     _accu = {
@@ -849,10 +849,10 @@ function forEach2(_l1, _l2, f) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return;
     }
     f(l1.hd, l2.hd);
@@ -867,10 +867,10 @@ function reduce2(_l1, _l2, _accu, f) {
     let accu = _accu;
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return accu;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return accu;
     }
     _accu = f(accu, l1.hd, l2.hd);
@@ -881,7 +881,7 @@ function reduce2(_l1, _l2, _accu, f) {
 }
 
 function reduceReverse2Unsafe(l1, l2, accu, f) {
-  if (l1 && l2) {
+  if (l1 !== 0 && l2 !== 0) {
     return f(reduceReverse2Unsafe(l1.tl, l2.tl, accu, f), l1.hd, l2.hd);
   } else {
     return accu;
@@ -907,7 +907,7 @@ function reduceReverse2(l1, l2, acc, f) {
 function every(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return true;
     }
     if (!p(xs.hd)) {
@@ -921,7 +921,7 @@ function every(_xs, p) {
 function some(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (p(xs.hd)) {
@@ -936,10 +936,10 @@ function every2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return true;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return true;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -955,14 +955,14 @@ function compareLength(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     _l2 = l2.tl;
@@ -975,14 +975,14 @@ function compare(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     let c = p(l1.hd, l2.hd);
@@ -999,10 +999,10 @@ function equal(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      return !l2;
+    if (l1 === 0) {
+      return l2 === 0;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (!p(l1.hd, l2.hd)) {
@@ -1018,10 +1018,10 @@ function some2(_l1, _l2, p) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return false;
     }
-    if (!l2) {
+    if (l2 === 0) {
       return false;
     }
     if (p(l1.hd, l2.hd)) {
@@ -1036,7 +1036,7 @@ function some2(_l1, _l2, p) {
 function has(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd, x)) {
@@ -1050,7 +1050,7 @@ function has(_xs, x, eq) {
 function getAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let match = xs.hd;
@@ -1065,7 +1065,7 @@ function getAssoc(_xs, x, eq) {
 function hasAssoc(_xs, x, eq) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return false;
     }
     if (eq(xs.hd[0], x)) {
@@ -1077,7 +1077,7 @@ function hasAssoc(_xs, x, eq) {
 }
 
 function removeAssoc(xs, x, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return /* [] */0;
   }
   let l = xs.tl;
@@ -1098,7 +1098,7 @@ function removeAssoc(xs, x, eq) {
 }
 
 function setAssoc(xs, x, k, eq) {
-  if (!xs) {
+  if (xs === 0) {
     return {
       hd: [
         x,
@@ -1145,7 +1145,7 @@ function sort(xs, cmp) {
 function find(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return;
     }
     let x = xs.hd;
@@ -1160,7 +1160,7 @@ function find(_xs, p) {
 function filter(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1184,7 +1184,7 @@ function filterWithIndex(xs, p) {
   while (true) {
     let i = _i;
     let xs$1 = _xs;
-    if (!xs$1) {
+    if (xs$1 === 0) {
       return /* [] */0;
     }
     let t = xs$1.tl;
@@ -1206,7 +1206,7 @@ function filterWithIndex(xs, p) {
 function filterMap(_xs, p) {
   while (true) {
     let xs = _xs;
-    if (!xs) {
+    if (xs === 0) {
       return /* [] */0;
     }
     let t = xs.tl;
@@ -1225,7 +1225,7 @@ function filterMap(_xs, p) {
 }
 
 function partition(l, p) {
-  if (!l) {
+  if (l === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1256,7 +1256,7 @@ function partition(l, p) {
 }
 
 function unzip(xs) {
-  if (!xs) {
+  if (xs === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -1279,10 +1279,10 @@ function unzip(xs) {
 }
 
 function zip(l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return /* [] */0;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return /* [] */0;
   }
   let cell = {
diff --git a/lib/js/Pervasives.js b/lib/js/Pervasives.js
index 35d21521a1..bc1fb820b4 100644
--- a/lib/js/Pervasives.js
+++ b/lib/js/Pervasives.js
@@ -107,7 +107,7 @@ function int_of_string_opt(s) {
 }
 
 function $at(l1, l2) {
-  if (l1) {
+  if (l1 !== 0) {
     return {
       hd: l1.hd,
       tl: $at(l1.tl, l2)
diff --git a/tests/docstring_tests/DocTest.res.mjs b/tests/docstring_tests/DocTest.res.mjs
index 399c0b537c..aa63b8065b 100644
--- a/tests/docstring_tests/DocTest.res.mjs
+++ b/tests/docstring_tests/DocTest.res.mjs
@@ -73,7 +73,7 @@ function getExamples(param) {
     while (true) {
       let acc = _acc;
       let items = _items;
-      if (!items) {
+      if (items === 0) {
         return acc;
       }
       let match = items.hd;
@@ -158,7 +158,7 @@ function getCodeBlocks(example) {
     while (true) {
       let acc = _acc;
       let lines = _lines;
-      if (!lines) {
+      if (lines === 0) {
         return Pervasives.panic("Failed to find end of code block for " + example.kind + ": " + example.id);
       }
       let hd = lines.hd;
@@ -177,7 +177,7 @@ function getCodeBlocks(example) {
     while (true) {
       let acc = _acc;
       let lines = _lines;
-      if (!lines) {
+      if (lines === 0) {
         return acc;
       }
       let rest = lines.tl;
diff --git a/tests/tests/src/bdd.mjs b/tests/tests/src/bdd.mjs
index ea08036d64..63e0a8bcdb 100644
--- a/tests/tests/src/bdd.mjs
+++ b/tests/tests/src/bdd.mjs
@@ -57,7 +57,7 @@ function resize(newSize) {
   let copyBucket = _bucket => {
     while (true) {
       let bucket = _bucket;
-      if (!bucket) {
+      if (bucket === 0) {
         return;
       }
       let n = bucket.hd;
@@ -135,7 +135,7 @@ function mkNode(low, v, high) {
   let _b = bucket;
   while (true) {
     let b = _b;
-    if (b) {
+    if (b !== 0) {
       let n = b.hd;
       if (typeof n !== "object") {
         if (n === "One") {
diff --git a/tests/tests/src/exception_raise_test.mjs b/tests/tests/src/exception_raise_test.mjs
index 571bbff0e5..4f1f9dd08f 100644
--- a/tests/tests/src/exception_raise_test.mjs
+++ b/tests/tests/src/exception_raise_test.mjs
@@ -38,15 +38,15 @@ function appf(g, x) {
       }
     }
     let match = exn._1;
-    if (!match) {
+    if (match === 0) {
       return 4;
     }
     let match$1 = match.tl;
-    if (!match$1) {
+    if (match$1 === 0) {
       return 4;
     }
     let match$2 = match$1.tl;
-    if (match$2) {
+    if (match$2 !== 0) {
       return match$2.hd;
     } else {
       return 4;
diff --git a/tests/tests/src/ext_array_test.mjs b/tests/tests/src/ext_array_test.mjs
index 0ca8a94fe9..ec0dac2c80 100644
--- a/tests/tests/src/ext_array_test.mjs
+++ b/tests/tests/src/ext_array_test.mjs
@@ -33,7 +33,7 @@ function reverse(a) {
 }
 
 function reverse_of_list(x) {
-  if (!x) {
+  if (x === 0) {
     return [];
   }
   let len = Belt_List.length(x);
@@ -43,7 +43,7 @@ function reverse_of_list(x) {
   while (true) {
     let x$1 = _x;
     let i = _i;
-    if (!x$1) {
+    if (x$1 === 0) {
       return a;
     }
     a[(len - i | 0) - 2 | 0] = x$1.hd;
@@ -146,7 +146,7 @@ function to_list_map_acc(f, a, acc) {
 }
 
 function of_list_map(f, a) {
-  if (!a) {
+  if (a === 0) {
     return [];
   }
   let tl = a.tl;
@@ -158,7 +158,7 @@ function of_list_map(f, a) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return arr;
     }
     arr[i] = f(x.hd);
diff --git a/tests/tests/src/gpr_1150.mjs b/tests/tests/src/gpr_1150.mjs
index 6485e77f1c..1d2b06f9f1 100644
--- a/tests/tests/src/gpr_1150.mjs
+++ b/tests/tests/src/gpr_1150.mjs
@@ -2,17 +2,17 @@
 
 
 function f(children) {
-  if (!children) {
+  if (children === 0) {
     return [];
   }
   let children$1 = children.tl;
   let a0 = children.hd;
-  if (!children$1) {
+  if (children$1 === 0) {
     return [a0];
   }
   let children$2 = children$1.tl;
   let a1 = children$1.hd;
-  if (!children$2) {
+  if (children$2 === 0) {
     return [
       a0,
       a1
@@ -20,7 +20,7 @@ function f(children) {
   }
   let children$3 = children$2.tl;
   let a2 = children$2.hd;
-  if (!children$3) {
+  if (children$3 === 0) {
     return [
       a0,
       a1,
@@ -29,7 +29,7 @@ function f(children) {
   }
   let children$4 = children$3.tl;
   let a3 = children$3.hd;
-  if (!children$4) {
+  if (children$4 === 0) {
     return [
       a0,
       a1,
@@ -39,7 +39,7 @@ function f(children) {
   }
   let children$5 = children$4.tl;
   let a4 = children$4.hd;
-  if (!children$5) {
+  if (children$5 === 0) {
     return [
       a0,
       a1,
@@ -50,7 +50,7 @@ function f(children) {
   }
   let children$6 = children$5.tl;
   let a5 = children$5.hd;
-  if (!children$6) {
+  if (children$6 === 0) {
     return [
       a0,
       a1,
@@ -62,7 +62,7 @@ function f(children) {
   }
   let children$7 = children$6.tl;
   let a6 = children$6.hd;
-  if (!children$7) {
+  if (children$7 === 0) {
     return [
       a0,
       a1,
@@ -75,7 +75,7 @@ function f(children) {
   }
   let children$8 = children$7.tl;
   let a7 = children$7.hd;
-  if (!children$8) {
+  if (children$8 === 0) {
     return [
       a0,
       a1,
@@ -89,7 +89,7 @@ function f(children) {
   }
   let children$9 = children$8.tl;
   let a8 = children$8.hd;
-  if (!children$9) {
+  if (children$9 === 0) {
     return [
       a0,
       a1,
@@ -104,7 +104,7 @@ function f(children) {
   }
   let children$10 = children$9.tl;
   let a9 = children$9.hd;
-  if (!children$10) {
+  if (children$10 === 0) {
     return [
       a0,
       a1,
@@ -120,7 +120,7 @@ function f(children) {
   }
   let children$11 = children$10.tl;
   let a10 = children$10.hd;
-  if (!children$11) {
+  if (children$11 === 0) {
     return [
       a0,
       a1,
@@ -137,7 +137,7 @@ function f(children) {
   }
   let children$12 = children$11.tl;
   let a11 = children$11.hd;
-  if (!children$12) {
+  if (children$12 === 0) {
     return [
       a0,
       a1,
@@ -155,7 +155,7 @@ function f(children) {
   }
   let children$13 = children$12.tl;
   let a12 = children$12.hd;
-  if (!children$13) {
+  if (children$13 === 0) {
     return [
       a0,
       a1,
@@ -174,7 +174,7 @@ function f(children) {
   }
   let children$14 = children$13.tl;
   let a13 = children$13.hd;
-  if (!children$14) {
+  if (children$14 === 0) {
     return [
       a0,
       a1,
@@ -194,7 +194,7 @@ function f(children) {
   }
   let children$15 = children$14.tl;
   let a14 = children$14.hd;
-  if (!children$15) {
+  if (children$15 === 0) {
     return [
       a0,
       a1,
@@ -213,7 +213,7 @@ function f(children) {
       a14
     ];
   }
-  if (children$15.tl) {
+  if (children$15.tl !== 0) {
     throw {
       RE_EXN_ID: "Assert_failure",
       _1: [
diff --git a/tests/tests/src/gpr_4632.mjs b/tests/tests/src/gpr_4632.mjs
index 66dfe24aac..c581a7090e 100644
--- a/tests/tests/src/gpr_4632.mjs
+++ b/tests/tests/src/gpr_4632.mjs
@@ -1,7 +1,7 @@
 // Generated by ReScript, PLEASE EDIT WITH CARE
 
 
-let T0_myList = {
+let myList = {
   hd: 1,
   tl: {
     hd: 2,
@@ -9,29 +9,77 @@ let T0_myList = {
   }
 };
 
-let T0_tail = {
-  hd: 2,
-  tl: /* [] */0
-};
+let T0;
 
-let T0 = {
-  myList: T0_myList,
-  head: 1,
-  tail: T0_tail
-};
+if (myList !== 0) {
+  T0 = {
+    myList: myList,
+    head: 1,
+    tail: {
+      hd: 2,
+      tl: /* [] */0
+    }
+  };
+} else {
+  throw {
+    RE_EXN_ID: "Match_failure",
+    _1: [
+      "gpr_4632.res",
+      6,
+      6
+    ],
+    Error: new Error()
+  };
+}
 
-throw {
-  RE_EXN_ID: "Match_failure",
-  _1: [
-    "gpr_4632.res",
-    12,
-    6
+let myList$1 = {
+  hd: [
+    1,
+    2,
+    3
   ],
-  Error: new Error()
+  tl: /* [] */0
 };
 
+let T1;
+
+if (myList$1 !== 0) {
+  if (/* [] */0 !== 0) {
+    T1 = {
+      myList: myList$1,
+      h0: [
+        1,
+        2,
+        3
+      ],
+      h1: /* [] */(0).hd,
+      h2: /* [] */(0).tl
+    };
+  } else {
+    throw {
+      RE_EXN_ID: "Match_failure",
+      _1: [
+        "gpr_4632.res",
+        12,
+        6
+      ],
+      Error: new Error()
+    };
+  }
+} else {
+  throw {
+    RE_EXN_ID: "Match_failure",
+    _1: [
+      "gpr_4632.res",
+      12,
+      6
+    ],
+    Error: new Error()
+  };
+}
+
 export {
   T0,
   T1,
 }
-/* T1 Not a pure module */
+/* T0 Not a pure module */
diff --git a/tests/tests/src/gpr_4639_test.mjs b/tests/tests/src/gpr_4639_test.mjs
index 6e281fb365..87774032ab 100644
--- a/tests/tests/src/gpr_4639_test.mjs
+++ b/tests/tests/src/gpr_4639_test.mjs
@@ -2,12 +2,12 @@
 
 
 function x(url) {
-  if (!url) {
+  if (url === 0) {
     return "start";
   }
   switch (url.hd) {
     case "login" :
-      if (url.tl) {
+      if (url.tl !== 0) {
         return "start";
       } else {
         return "login";
diff --git a/tests/tests/src/mario_game.mjs b/tests/tests/src/mario_game.mjs
index 3f460365a9..6086b07dfe 100644
--- a/tests/tests/src/mario_game.mjs
+++ b/tests/tests/src/mario_game.mjs
@@ -2098,7 +2098,7 @@ function check_collisions(collid, all_collids, state) {
   while (true) {
     let acc = _acc;
     let cs = _cs;
-    if (!cs) {
+    if (cs === 0) {
       return acc;
     }
     let h = cs.hd;
@@ -2421,7 +2421,7 @@ let Director = {
 function mem_loc(checkloc, _loclist) {
   while (true) {
     let loclist = _loclist;
-    if (!loclist) {
+    if (loclist === 0) {
       return false;
     }
     if (Primitive_object.equal(checkloc, loclist.hd[1])) {
@@ -2433,7 +2433,7 @@ function mem_loc(checkloc, _loclist) {
 }
 
 function convert_list(lst) {
-  if (!lst) {
+  if (lst === 0) {
     return /* [] */0;
   }
   let h = lst.hd;
@@ -2485,7 +2485,7 @@ function choose_sblock_typ(typ) {
 function avoid_overlap(_lst, currentLst) {
   while (true) {
     let lst = _lst;
-    if (!lst) {
+    if (lst === 0) {
       return /* [] */0;
     }
     let t = lst.tl;
@@ -2504,7 +2504,7 @@ function avoid_overlap(_lst, currentLst) {
 function trim_edges(_lst, blockw, blockh) {
   while (true) {
     let lst = _lst;
-    if (!lst) {
+    if (lst === 0) {
       return /* [] */0;
     }
     let t = lst.tl;
@@ -2545,7 +2545,7 @@ function generate_coins(_block_coord) {
   while (true) {
     let block_coord = _block_coord;
     let place_coin = int(2);
-    if (!block_coord) {
+    if (block_coord === 0) {
       return /* [] */0;
     }
     let t = block_coord.tl;
@@ -3037,7 +3037,7 @@ function generate_block_enemies(_block_coord) {
     let block_coord = _block_coord;
     let place_enemy = int(20);
     let enemy_typ = int(3);
-    if (!block_coord) {
+    if (block_coord === 0) {
       return /* [] */0;
     }
     let t = block_coord.tl;
@@ -3149,7 +3149,7 @@ function generate_ground(blockw, blockh, _inc, _acc) {
 }
 
 function convert_to_block_obj(lst, context) {
-  if (!lst) {
+  if (lst === 0) {
     return /* [] */0;
   }
   let h = lst.hd;
@@ -3165,7 +3165,7 @@ function convert_to_block_obj(lst, context) {
 }
 
 function convert_to_enemy_obj(lst, context) {
-  if (!lst) {
+  if (lst === 0) {
     return /* [] */0;
   }
   let h = lst.hd;
@@ -3181,7 +3181,7 @@ function convert_to_enemy_obj(lst, context) {
 }
 
 function convert_to_coin_obj(lst, context) {
-  if (!lst) {
+  if (lst === 0) {
     return /* [] */0;
   }
   let ob = spawn({
diff --git a/tests/tests/src/mt.mjs b/tests/tests/src/mt.mjs
index 1534dbe473..a10fd640a5 100644
--- a/tests/tests/src/mt.mjs
+++ b/tests/tests/src/mt.mjs
@@ -12,11 +12,11 @@ function assert_fail(msg) {
 
 function is_mocha() {
   let match = Belt_List.fromArray(Process.argv);
-  if (!match) {
+  if (match === 0) {
     return false;
   }
   let match$1 = match.tl;
-  if (!match$1) {
+  if (match$1 === 0) {
     return false;
   }
   let exec = Path.basename(match$1.hd);
@@ -217,7 +217,7 @@ let from_promise_suites = (function from_promise_suites(name, suites) {
 
 function old_from_promise_suites_donotuse(name, suites) {
   let match = Belt_List.fromArray(Process.argv);
-  if (match) {
+  if (match !== 0) {
     if (is_mocha()) {
       describe(name, () => Belt_List.forEach(suites, param => {
         let code = param[1];
diff --git a/tests/tests/src/nested_pattern_match_test.mjs b/tests/tests/src/nested_pattern_match_test.mjs
index 5fe0182b48..d15dc8b6d9 100644
--- a/tests/tests/src/nested_pattern_match_test.mjs
+++ b/tests/tests/src/nested_pattern_match_test.mjs
@@ -2,27 +2,27 @@
 
 
 function f_list(x) {
-  if (!x) {
+  if (x === 0) {
     return 0;
   }
   let match = x.tl;
-  if (!match) {
+  if (match === 0) {
     return 0;
   }
   let match$1 = match.tl;
-  if (!match$1) {
+  if (match$1 === 0) {
     return 0;
   }
   let match$2 = match$1.tl;
-  if (!match$2) {
+  if (match$2 === 0) {
     return 0;
   }
   let match$3 = match$2.tl;
-  if (!match$3) {
+  if (match$3 === 0) {
     return 0;
   }
   let match$4 = match$3.tl;
-  if (match$4) {
+  if (match$4 !== 0) {
     return ((((x.hd + match.hd | 0) + match$1.hd | 0) + match$2.hd | 0) + match$3.hd | 0) + match$4.hd | 0;
   } else {
     return 0;
@@ -49,21 +49,21 @@ function f_opion(x) {
       return 0;
     }
     let match$1 = x.lo;
-    if (!match$1) {
+    if (match$1 === 0) {
       return 0;
     }
     if (match$1.hd !== undefined) {
       return 0;
     }
     let match$2 = match$1.tl;
-    if (!match$2) {
+    if (match$2 === 0) {
       return 0;
     }
     if (match$2.hd !== undefined) {
       return 0;
     }
     let match$3 = match$2.tl;
-    if (!match$3) {
+    if (match$3 === 0) {
       return 0;
     }
     let match$4 = match$3.hd;
@@ -74,7 +74,7 @@ function f_opion(x) {
       return 0;
     }
     let match$5 = match$3.tl;
-    if (!match$5) {
+    if (match$5 === 0) {
       return 0;
     }
     let match$6 = match$5.hd;
@@ -85,28 +85,28 @@ function f_opion(x) {
       return 0;
     }
     let match$7 = match$5.tl;
-    if (match$7 && match$7.hd !== undefined) {
+    if (match$7 !== 0 && match$7.hd !== undefined) {
       return 2;
     } else {
       return 0;
     }
   }
   let match$8 = x.lo;
-  if (!match$8) {
+  if (match$8 === 0) {
     return 0;
   }
   if (match$8.hd !== undefined) {
     return 0;
   }
   let match$9 = match$8.tl;
-  if (!match$9) {
+  if (match$9 === 0) {
     return 0;
   }
   if (match$9.hd !== undefined) {
     return 0;
   }
   let match$10 = match$9.tl;
-  if (!match$10) {
+  if (match$10 === 0) {
     return 0;
   }
   let match$11 = match$10.hd;
@@ -117,7 +117,7 @@ function f_opion(x) {
     return 0;
   }
   let match$12 = match$10.tl;
-  if (!match$12) {
+  if (match$12 === 0) {
     return 0;
   }
   let match$13 = match$12.hd;
@@ -128,7 +128,7 @@ function f_opion(x) {
     return 0;
   }
   let match$14 = match$12.tl;
-  if (match$14 && match$14.hd !== undefined) {
+  if (match$14 !== 0 && match$14.hd !== undefined) {
     return 3;
   } else {
     return 0;
diff --git a/tests/tests/src/ocaml_compat/Ocaml_Array.mjs b/tests/tests/src/ocaml_compat/Ocaml_Array.mjs
index 7fb5f35aa4..6109a9cd14 100644
--- a/tests/tests/src/ocaml_compat/Ocaml_Array.mjs
+++ b/tests/tests/src/ocaml_compat/Ocaml_Array.mjs
@@ -157,7 +157,7 @@ function list_length(_accu, _param) {
   while (true) {
     let param = _param;
     let accu = _accu;
-    if (!param) {
+    if (param === 0) {
       return accu;
     }
     _param = param.tl;
@@ -167,7 +167,7 @@ function list_length(_accu, _param) {
 }
 
 function of_list(param) {
-  if (!param) {
+  if (param === 0) {
     return [];
   }
   let hd = param.hd;
@@ -178,7 +178,7 @@ function of_list(param) {
   while (true) {
     let param$1 = _param;
     let i = _i;
-    if (!param$1) {
+    if (param$1 === 0) {
       return a;
     }
     a[i] = param$1.hd;
diff --git a/tests/tests/src/ocaml_compat/Ocaml_List.mjs b/tests/tests/src/ocaml_compat/Ocaml_List.mjs
index 64703b8cd5..582cca5c84 100644
--- a/tests/tests/src/ocaml_compat/Ocaml_List.mjs
+++ b/tests/tests/src/ocaml_compat/Ocaml_List.mjs
@@ -9,7 +9,7 @@ function length(l) {
   while (true) {
     let param = _param;
     let len = _len;
-    if (!param) {
+    if (param === 0) {
       return len;
     }
     _param = param.tl;
@@ -26,7 +26,7 @@ function cons(a, l) {
 }
 
 function hd(param) {
-  if (param) {
+  if (param !== 0) {
     return param.hd;
   } else {
     return Pervasives.failwith("hd");
@@ -34,7 +34,7 @@ function hd(param) {
 }
 
 function tl(param) {
-  if (param) {
+  if (param !== 0) {
     return param.tl;
   } else {
     return Pervasives.failwith("tl");
@@ -50,7 +50,7 @@ function nth(l, n) {
   while (true) {
     let n$1 = _n;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return Pervasives.failwith("nth");
     }
     if (n$1 === 0) {
@@ -71,7 +71,7 @@ function nth_opt(l, n) {
   while (true) {
     let n$1 = _n;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return;
     }
     if (n$1 === 0) {
@@ -87,7 +87,7 @@ function rev_append(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -141,7 +141,7 @@ function init(len, f) {
 }
 
 function flatten(param) {
-  if (param) {
+  if (param !== 0) {
     return Pervasives.$at(param.hd, flatten(param.tl));
   } else {
     return /* [] */0;
@@ -149,7 +149,7 @@ function flatten(param) {
 }
 
 function map(f, param) {
-  if (!param) {
+  if (param === 0) {
     return /* [] */0;
   }
   let r = f(param.hd);
@@ -160,7 +160,7 @@ function map(f, param) {
 }
 
 function mapi(i, f, param) {
-  if (!param) {
+  if (param === 0) {
     return /* [] */0;
   }
   let r = f(i, param.hd);
@@ -180,7 +180,7 @@ function rev_map(f, l) {
   while (true) {
     let param = _param;
     let accu = _accu;
-    if (!param) {
+    if (param === 0) {
       return accu;
     }
     _param = param.tl;
@@ -195,7 +195,7 @@ function rev_map(f, l) {
 function iter(f, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return;
     }
     f(param.hd);
@@ -210,7 +210,7 @@ function iteri(f, l) {
   while (true) {
     let param = _param;
     let i = _i;
-    if (!param) {
+    if (param === 0) {
       return;
     }
     f(i, param.hd);
@@ -224,7 +224,7 @@ function fold_left(f, _accu, _l) {
   while (true) {
     let l = _l;
     let accu = _accu;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _l = l.tl;
@@ -234,7 +234,7 @@ function fold_left(f, _accu, _l) {
 }
 
 function fold_right(f, l, accu) {
-  if (l) {
+  if (l !== 0) {
     return f(l.hd, fold_right(f, l.tl, accu));
   } else {
     return accu;
@@ -242,14 +242,14 @@ function fold_right(f, l, accu) {
 }
 
 function map2(f, l1, l2) {
-  if (!l1) {
-    if (l2) {
+  if (l1 === 0) {
+    if (l2 !== 0) {
       return Pervasives.invalid_arg("List.map2");
     } else {
       return /* [] */0;
     }
   }
-  if (!l2) {
+  if (l2 === 0) {
     return Pervasives.invalid_arg("List.map2");
   }
   let r = f(l1.hd, l2.hd);
@@ -267,14 +267,14 @@ function rev_map2(f, l1, l2) {
     let l2$1 = _l2;
     let l1$1 = _l1;
     let accu = _accu;
-    if (!l1$1) {
-      if (l2$1) {
+    if (l1$1 === 0) {
+      if (l2$1 !== 0) {
         return Pervasives.invalid_arg("List.rev_map2");
       } else {
         return accu;
       }
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return Pervasives.invalid_arg("List.rev_map2");
     }
     _l2 = l2$1.tl;
@@ -291,14 +291,14 @@ function iter2(f, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.iter2");
       } else {
         return;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.iter2");
     }
     f(l1.hd, l2.hd);
@@ -313,14 +313,14 @@ function fold_left2(f, _accu, _l1, _l2) {
     let l2 = _l2;
     let l1 = _l1;
     let accu = _accu;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.fold_left2");
       } else {
         return accu;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.fold_left2");
     }
     _l2 = l2.tl;
@@ -331,13 +331,13 @@ function fold_left2(f, _accu, _l1, _l2) {
 }
 
 function fold_right2(f, l1, l2, accu) {
-  if (l1) {
-    if (l2) {
+  if (l1 !== 0) {
+    if (l2 !== 0) {
       return f(l1.hd, l2.hd, fold_right2(f, l1.tl, l2.tl, accu));
     } else {
       return Pervasives.invalid_arg("List.fold_right2");
     }
-  } else if (l2) {
+  } else if (l2 !== 0) {
     return Pervasives.invalid_arg("List.fold_right2");
   } else {
     return accu;
@@ -347,7 +347,7 @@ function fold_right2(f, l1, l2, accu) {
 function for_all(p, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return true;
     }
     if (!p(param.hd)) {
@@ -361,7 +361,7 @@ function for_all(p, _param) {
 function exists(p, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return false;
     }
     if (p(param.hd)) {
@@ -376,14 +376,14 @@ function for_all2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.for_all2");
       } else {
         return true;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.for_all2");
     }
     if (!p(l1.hd, l2.hd)) {
@@ -399,14 +399,14 @@ function exists2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.exists2");
       } else {
         return false;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.exists2");
     }
     if (p(l1.hd, l2.hd)) {
@@ -421,7 +421,7 @@ function exists2(p, _l1, _l2) {
 function mem(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return false;
     }
     if (param.hd === x) {
@@ -435,7 +435,7 @@ function mem(x, _param) {
 function memq(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return false;
     }
     if (param.hd === x) {
@@ -449,7 +449,7 @@ function memq(x, _param) {
 function assoc(x, _param) {
   while (true) {
     let param = _param;
-    if (param) {
+    if (param !== 0) {
       let match = param.hd;
       if (match[0] === x) {
         return match[1];
@@ -467,7 +467,7 @@ function assoc(x, _param) {
 function assoc_opt(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return;
     }
     let match = param.hd;
@@ -482,7 +482,7 @@ function assoc_opt(x, _param) {
 function assq(x, _param) {
   while (true) {
     let param = _param;
-    if (param) {
+    if (param !== 0) {
       let match = param.hd;
       if (match[0] === x) {
         return match[1];
@@ -500,7 +500,7 @@ function assq(x, _param) {
 function assq_opt(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return;
     }
     let match = param.hd;
@@ -515,7 +515,7 @@ function assq_opt(x, _param) {
 function mem_assoc(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return false;
     }
     if (param.hd[0] === x) {
@@ -529,7 +529,7 @@ function mem_assoc(x, _param) {
 function mem_assq(x, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return false;
     }
     if (param.hd[0] === x) {
@@ -541,7 +541,7 @@ function mem_assq(x, _param) {
 }
 
 function remove_assoc(x, param) {
-  if (!param) {
+  if (param === 0) {
     return /* [] */0;
   }
   let l = param.tl;
@@ -557,7 +557,7 @@ function remove_assoc(x, param) {
 }
 
 function remove_assq(x, param) {
-  if (!param) {
+  if (param === 0) {
     return /* [] */0;
   }
   let l = param.tl;
@@ -575,7 +575,7 @@ function remove_assq(x, param) {
 function find(p, _param) {
   while (true) {
     let param = _param;
-    if (param) {
+    if (param !== 0) {
       let x = param.hd;
       if (p(x)) {
         return x;
@@ -593,7 +593,7 @@ function find(p, _param) {
 function find_opt(p, _param) {
   while (true) {
     let param = _param;
-    if (!param) {
+    if (param === 0) {
       return;
     }
     let x = param.hd;
@@ -611,7 +611,7 @@ function find_all(p, l) {
   while (true) {
     let param = _param;
     let accu = _accu;
-    if (!param) {
+    if (param === 0) {
       return rev_append(accu, /* [] */0);
     }
     let l$1 = param.tl;
@@ -637,7 +637,7 @@ function partition(p, l) {
     let param = _param;
     let no = _no;
     let yes = _yes;
-    if (!param) {
+    if (param === 0) {
       return [
         rev_append(yes, /* [] */0),
         rev_append(no, /* [] */0)
@@ -663,7 +663,7 @@ function partition(p, l) {
 }
 
 function split(param) {
-  if (!param) {
+  if (param === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -684,8 +684,8 @@ function split(param) {
 }
 
 function combine(l1, l2) {
-  if (l1) {
-    if (l2) {
+  if (l1 !== 0) {
+    if (l2 !== 0) {
       return {
         hd: [
           l1.hd,
@@ -696,7 +696,7 @@ function combine(l1, l2) {
     } else {
       return Pervasives.invalid_arg("List.combine");
     }
-  } else if (l2) {
+  } else if (l2 !== 0) {
     return Pervasives.invalid_arg("List.combine");
   } else {
     return /* [] */0;
@@ -704,10 +704,10 @@ function combine(l1, l2) {
 }
 
 function merge(cmp, l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return l2;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return l1;
   }
   let h2 = l2.hd;
@@ -732,7 +732,7 @@ function chop(_k, _l) {
     if (k === 0) {
       return l;
     }
-    if (l) {
+    if (l !== 0) {
       _l = l.tl;
       _k = k - 1 | 0;
       continue;
@@ -752,11 +752,11 @@ function chop(_k, _l) {
 function stable_sort(cmp, l) {
   let sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -835,9 +835,9 @@ function stable_sort(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         if (cmp(x1$1, x2$1) <= 0) {
@@ -872,10 +872,10 @@ function stable_sort(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let h2 = l2$1.hd;
@@ -898,11 +898,11 @@ function stable_sort(cmp, l) {
   };
   let rev_sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -981,9 +981,9 @@ function stable_sort(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         if (cmp(x1$1, x2$1) > 0) {
@@ -1018,10 +1018,10 @@ function stable_sort(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let h2 = l2$1.hd;
@@ -1053,11 +1053,11 @@ function stable_sort(cmp, l) {
 function sort_uniq(cmp, l) {
   let sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -1203,9 +1203,9 @@ function sort_uniq(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         let c$6 = cmp(x1$1, x2$1);
@@ -1246,10 +1246,10 @@ function sort_uniq(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let t2 = l2$1.tl;
@@ -1284,11 +1284,11 @@ function sort_uniq(cmp, l) {
   };
   let rev_sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -1434,9 +1434,9 @@ function sort_uniq(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         let c$6 = cmp(x1$1, x2$1);
@@ -1477,10 +1477,10 @@ function sort_uniq(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let t2 = l2$1.tl;
@@ -1525,14 +1525,14 @@ function compare_lengths(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return -1;
       } else {
         return 0;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return 1;
     }
     _l2 = l2.tl;
@@ -1545,7 +1545,7 @@ function compare_length_with(_l, _n) {
   while (true) {
     let n = _n;
     let l = _l;
-    if (!l) {
+    if (l === 0) {
       if (n === 0) {
         return 0;
       } else if (n > 0) {
diff --git a/tests/tests/src/polymorphism_test.mjs b/tests/tests/src/polymorphism_test.mjs
index 8acb18b56a..ba38b2d850 100644
--- a/tests/tests/src/polymorphism_test.mjs
+++ b/tests/tests/src/polymorphism_test.mjs
@@ -2,7 +2,7 @@
 
 
 function map(f, x) {
-  if (!x) {
+  if (x === 0) {
     return /* [] */0;
   }
   let r = f(x.hd);
diff --git a/tests/tests/src/reasonReactRouter.mjs b/tests/tests/src/reasonReactRouter.mjs
index 92c3a7013b..1e22e6d9b2 100644
--- a/tests/tests/src/reasonReactRouter.mjs
+++ b/tests/tests/src/reasonReactRouter.mjs
@@ -107,10 +107,10 @@ function urlNotEqual(a, b) {
     while (true) {
       let bList = _bList;
       let aList = _aList;
-      if (!aList) {
-        return bList;
+      if (aList === 0) {
+        return bList !== 0;
       }
-      if (!bList) {
+      if (bList === 0) {
         return true;
       }
       if (aList.hd !== bList.hd) {
diff --git a/tests/tests/src/set_gen.mjs b/tests/tests/src/set_gen.mjs
index c295c5829d..19fb820753 100644
--- a/tests/tests/src/set_gen.mjs
+++ b/tests/tests/src/set_gen.mjs
@@ -438,7 +438,7 @@ function of_sorted_list(l) {
           l
         ];
       case 1 :
-        if (l) {
+        if (l !== 0) {
           return [
             {
               TAG: "Node",
@@ -452,9 +452,9 @@ function of_sorted_list(l) {
         }
         break;
       case 2 :
-        if (l) {
+        if (l !== 0) {
           let match = l.tl;
-          if (match) {
+          if (match !== 0) {
             return [
               {
                 TAG: "Node",
@@ -476,11 +476,11 @@ function of_sorted_list(l) {
         }
         break;
       case 3 :
-        if (l) {
+        if (l !== 0) {
           let match$1 = l.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let match$2 = match$1.tl;
-            if (match$2) {
+            if (match$2 !== 0) {
               return [
                 {
                   TAG: "Node",
@@ -513,7 +513,7 @@ function of_sorted_list(l) {
     let nl = n / 2 | 0;
     let match$3 = sub(nl, l);
     let l$1 = match$3[1];
-    if (l$1) {
+    if (l$1 !== 0) {
       let match$4 = sub((n - nl | 0) - 1 | 0, l$1.tl);
       return [
         create(match$3[0], l$1.hd, match$4[0]),
diff --git a/tests/tests/src/string_set.mjs b/tests/tests/src/string_set.mjs
index e5ba524aef..c6d5a321c3 100644
--- a/tests/tests/src/string_set.mjs
+++ b/tests/tests/src/string_set.mjs
@@ -239,28 +239,28 @@ function find(x, _tree) {
 }
 
 function of_list(l) {
-  if (!l) {
+  if (l === 0) {
     return Set_gen.empty;
   }
   let match = l.tl;
   let x0 = l.hd;
-  if (!match) {
+  if (match === 0) {
     return Set_gen.singleton(x0);
   }
   let match$1 = match.tl;
   let x1 = match.hd;
-  if (!match$1) {
+  if (match$1 === 0) {
     return add(x1, Set_gen.singleton(x0));
   }
   let match$2 = match$1.tl;
   let x2 = match$1.hd;
-  if (!match$2) {
+  if (match$2 === 0) {
     return add(x2, add(x1, Set_gen.singleton(x0)));
   }
   let match$3 = match$2.tl;
   let x3 = match$2.hd;
-  if (match$3) {
-    if (match$3.tl) {
+  if (match$3 !== 0) {
+    if (match$3.tl !== 0) {
       return Set_gen.of_sorted_list(Belt_List.sort(l, compare_elt));
     } else {
       return add(match$3.hd, add(x3, add(x2, add(x1, Set_gen.singleton(x0)))));
diff --git a/tests/tests/src/test_ari.mjs b/tests/tests/src/test_ari.mjs
index a016c7a1c8..a36e53d1df 100644
--- a/tests/tests/src/test_ari.mjs
+++ b/tests/tests/src/test_ari.mjs
@@ -32,7 +32,7 @@ function length_aux(_len, _x) {
   while (true) {
     let x = _x;
     let len = _len;
-    if (!x) {
+    if (x === 0) {
       return len;
     }
     _x = x.tl;
diff --git a/tests/tests/src/test_bool_equal.mjs b/tests/tests/src/test_bool_equal.mjs
index d7e5c90a32..3bb876441f 100644
--- a/tests/tests/src/test_bool_equal.mjs
+++ b/tests/tests/src/test_bool_equal.mjs
@@ -98,7 +98,7 @@ function f4(x) {
 }
 
 function f5(x) {
-  if (x) {
+  if (x !== 0) {
     return 2;
   } else {
     return 1;
diff --git a/tests/tests/src/test_list.mjs b/tests/tests/src/test_list.mjs
index 524ef92d6e..ef5979b0a7 100644
--- a/tests/tests/src/test_list.mjs
+++ b/tests/tests/src/test_list.mjs
@@ -7,7 +7,7 @@ function length_aux(_len, _x) {
   while (true) {
     let x = _x;
     let len = _len;
-    if (!x) {
+    if (x === 0) {
       return len;
     }
     _x = x.tl;
@@ -21,7 +21,7 @@ function length(l) {
 }
 
 function hd(x) {
-  if (x) {
+  if (x !== 0) {
     return x.hd;
   } else {
     return Pervasives.failwith("hd");
@@ -29,7 +29,7 @@ function hd(x) {
 }
 
 function tl(x) {
-  if (x) {
+  if (x !== 0) {
     return x.tl;
   } else {
     return Pervasives.failwith("tl");
@@ -45,7 +45,7 @@ function nth(l, n) {
   while (true) {
     let n$1 = _n;
     let l$1 = _l;
-    if (!l$1) {
+    if (l$1 === 0) {
       return Pervasives.failwith("nth");
     }
     if (n$1 === 0) {
@@ -61,7 +61,7 @@ function rev_append(_l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
+    if (l1 === 0) {
       return l2;
     }
     _l2 = {
@@ -78,7 +78,7 @@ function rev(l) {
 }
 
 function flatten(x) {
-  if (x) {
+  if (x !== 0) {
     return Pervasives.$at(x.hd, flatten(x.tl));
   } else {
     return /* [] */0;
@@ -86,7 +86,7 @@ function flatten(x) {
 }
 
 function map(f, x) {
-  if (!x) {
+  if (x === 0) {
     return /* [] */0;
   }
   let r = f(x.hd);
@@ -97,7 +97,7 @@ function map(f, x) {
 }
 
 function mapi(i, f, x) {
-  if (!x) {
+  if (x === 0) {
     return /* [] */0;
   }
   let r = f(i, x.hd);
@@ -117,7 +117,7 @@ function rev_map(f, l) {
   while (true) {
     let x = _x;
     let accu = _accu;
-    if (!x) {
+    if (x === 0) {
       return accu;
     }
     _x = x.tl;
@@ -132,7 +132,7 @@ function rev_map(f, l) {
 function iter(f, _x) {
   while (true) {
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     f(x.hd);
@@ -147,7 +147,7 @@ function iteri(f, l) {
   while (true) {
     let x = _x;
     let i = _i;
-    if (!x) {
+    if (x === 0) {
       return;
     }
     f(i, x.hd);
@@ -161,7 +161,7 @@ function fold_left(f, _accu, _l) {
   while (true) {
     let l = _l;
     let accu = _accu;
-    if (!l) {
+    if (l === 0) {
       return accu;
     }
     _l = l.tl;
@@ -171,7 +171,7 @@ function fold_left(f, _accu, _l) {
 }
 
 function fold_right(f, l, accu) {
-  if (l) {
+  if (l !== 0) {
     return f(l.hd, fold_right(f, l.tl, accu));
   } else {
     return accu;
@@ -179,14 +179,14 @@ function fold_right(f, l, accu) {
 }
 
 function map2(f, l1, l2) {
-  if (!l1) {
-    if (l2) {
+  if (l1 === 0) {
+    if (l2 !== 0) {
       return Pervasives.invalid_arg("List.map2");
     } else {
       return /* [] */0;
     }
   }
-  if (!l2) {
+  if (l2 === 0) {
     return Pervasives.invalid_arg("List.map2");
   }
   let r = f(l1.hd, l2.hd);
@@ -204,14 +204,14 @@ function rev_map2(f, l1, l2) {
     let l2$1 = _l2;
     let l1$1 = _l1;
     let accu = _accu;
-    if (!l1$1) {
-      if (l2$1) {
+    if (l1$1 === 0) {
+      if (l2$1 !== 0) {
         return Pervasives.invalid_arg("List.rev_map2");
       } else {
         return accu;
       }
     }
-    if (!l2$1) {
+    if (l2$1 === 0) {
       return Pervasives.invalid_arg("List.rev_map2");
     }
     _l2 = l2$1.tl;
@@ -228,14 +228,14 @@ function iter2(f, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.iter2");
       } else {
         return;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.iter2");
     }
     f(l1.hd, l2.hd);
@@ -250,14 +250,14 @@ function fold_left2(f, _accu, _l1, _l2) {
     let l2 = _l2;
     let l1 = _l1;
     let accu = _accu;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.fold_left2");
       } else {
         return accu;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.fold_left2");
     }
     _l2 = l2.tl;
@@ -268,13 +268,13 @@ function fold_left2(f, _accu, _l1, _l2) {
 }
 
 function fold_right2(f, l1, l2, accu) {
-  if (l1) {
-    if (l2) {
+  if (l1 !== 0) {
+    if (l2 !== 0) {
       return f(l1.hd, l2.hd, fold_right2(f, l1.tl, l2.tl, accu));
     } else {
       return Pervasives.invalid_arg("List.fold_right2");
     }
-  } else if (l2) {
+  } else if (l2 !== 0) {
     return Pervasives.invalid_arg("List.fold_right2");
   } else {
     return accu;
@@ -284,7 +284,7 @@ function fold_right2(f, l1, l2, accu) {
 function for_all(p, _x) {
   while (true) {
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return true;
     }
     if (!p(x.hd)) {
@@ -298,7 +298,7 @@ function for_all(p, _x) {
 function exists(p, _x) {
   while (true) {
     let x = _x;
-    if (!x) {
+    if (x === 0) {
       return false;
     }
     if (p(x.hd)) {
@@ -313,14 +313,14 @@ function for_all2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.for_all2");
       } else {
         return true;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.for_all2");
     }
     if (!p(l1.hd, l2.hd)) {
@@ -336,14 +336,14 @@ function exists2(p, _l1, _l2) {
   while (true) {
     let l2 = _l2;
     let l1 = _l1;
-    if (!l1) {
-      if (l2) {
+    if (l1 === 0) {
+      if (l2 !== 0) {
         return Pervasives.invalid_arg("List.exists2");
       } else {
         return false;
       }
     }
-    if (!l2) {
+    if (l2 === 0) {
       return Pervasives.invalid_arg("List.exists2");
     }
     if (p(l1.hd, l2.hd)) {
@@ -358,7 +358,7 @@ function exists2(p, _l1, _l2) {
 function mem(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (!x_) {
+    if (x_ === 0) {
       return false;
     }
     if (x_.hd === x) {
@@ -372,7 +372,7 @@ function mem(x, _x_) {
 function memq(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (!x_) {
+    if (x_ === 0) {
       return false;
     }
     if (x_.hd === x) {
@@ -386,7 +386,7 @@ function memq(x, _x_) {
 function assoc(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (x_) {
+    if (x_ !== 0) {
       let match = x_.hd;
       if (match[0] === x) {
         return match[1];
@@ -404,7 +404,7 @@ function assoc(x, _x_) {
 function assq(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (x_) {
+    if (x_ !== 0) {
       let match = x_.hd;
       if (match[0] === x) {
         return match[1];
@@ -422,7 +422,7 @@ function assq(x, _x_) {
 function mem_assoc(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (!x_) {
+    if (x_ === 0) {
       return false;
     }
     if (x_.hd[0] === x) {
@@ -436,7 +436,7 @@ function mem_assoc(x, _x_) {
 function mem_assq(x, _x_) {
   while (true) {
     let x_ = _x_;
-    if (!x_) {
+    if (x_ === 0) {
       return false;
     }
     if (x_.hd[0] === x) {
@@ -448,7 +448,7 @@ function mem_assq(x, _x_) {
 }
 
 function remove_assoc(x, x_) {
-  if (!x_) {
+  if (x_ === 0) {
     return /* [] */0;
   }
   let l = x_.tl;
@@ -464,7 +464,7 @@ function remove_assoc(x, x_) {
 }
 
 function remove_assq(x, x_) {
-  if (!x_) {
+  if (x_ === 0) {
     return /* [] */0;
   }
   let l = x_.tl;
@@ -482,7 +482,7 @@ function remove_assq(x, x_) {
 function find(p, _x) {
   while (true) {
     let x = _x;
-    if (x) {
+    if (x !== 0) {
       let x$1 = x.hd;
       if (p(x$1)) {
         return x$1;
@@ -504,7 +504,7 @@ function find_all(p) {
     while (true) {
       let x = _x;
       let accu = _accu;
-      if (!x) {
+      if (x === 0) {
         return rev_append(accu, /* [] */0);
       }
       let l = x.tl;
@@ -531,7 +531,7 @@ function partition(p, l) {
     let x = _x;
     let no = _no;
     let yes = _yes;
-    if (!x) {
+    if (x === 0) {
       return [
         rev_append(yes, /* [] */0),
         rev_append(no, /* [] */0)
@@ -557,7 +557,7 @@ function partition(p, l) {
 }
 
 function split(x) {
-  if (!x) {
+  if (x === 0) {
     return [
       /* [] */0,
       /* [] */0
@@ -578,8 +578,8 @@ function split(x) {
 }
 
 function combine(l1, l2) {
-  if (l1) {
-    if (l2) {
+  if (l1 !== 0) {
+    if (l2 !== 0) {
       return {
         hd: [
           l1.hd,
@@ -590,7 +590,7 @@ function combine(l1, l2) {
     } else {
       return Pervasives.invalid_arg("List.combine");
     }
-  } else if (l2) {
+  } else if (l2 !== 0) {
     return Pervasives.invalid_arg("List.combine");
   } else {
     return /* [] */0;
@@ -598,10 +598,10 @@ function combine(l1, l2) {
 }
 
 function merge(cmp, l1, l2) {
-  if (!l1) {
+  if (l1 === 0) {
     return l2;
   }
-  if (!l2) {
+  if (l2 === 0) {
     return l1;
   }
   let h2 = l2.hd;
@@ -626,7 +626,7 @@ function chop(_k, _l) {
     if (k === 0) {
       return l;
     }
-    if (l) {
+    if (l !== 0) {
       _l = l.tl;
       _k = k - 1 | 0;
       continue;
@@ -646,11 +646,11 @@ function chop(_k, _l) {
 function stable_sort(cmp, l) {
   let sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -729,9 +729,9 @@ function stable_sort(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         if (cmp(x1$1, x2$1) <= 0) {
@@ -766,10 +766,10 @@ function stable_sort(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let h2 = l2$1.hd;
@@ -792,11 +792,11 @@ function stable_sort(cmp, l) {
   };
   let rev_sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -875,9 +875,9 @@ function stable_sort(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         if (cmp(x1$1, x2$1) > 0) {
@@ -912,10 +912,10 @@ function stable_sort(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let h2 = l2$1.hd;
@@ -947,11 +947,11 @@ function stable_sort(cmp, l) {
 function sort_uniq(cmp, l) {
   let sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -1097,9 +1097,9 @@ function sort_uniq(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         let c$6 = cmp(x1$1, x2$1);
@@ -1140,10 +1140,10 @@ function sort_uniq(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let t2 = l2$1.tl;
@@ -1178,11 +1178,11 @@ function sort_uniq(cmp, l) {
   };
   let rev_sort = (n, l) => {
     if (n !== 2) {
-      if (n === 3 && l) {
+      if (n === 3 && l !== 0) {
         let match = l.tl;
-        if (match) {
+        if (match !== 0) {
           let match$1 = match.tl;
-          if (match$1) {
+          if (match$1 !== 0) {
             let x3 = match$1.hd;
             let x2 = match.hd;
             let x1 = l.hd;
@@ -1328,9 +1328,9 @@ function sort_uniq(cmp, l) {
         
       }
       
-    } else if (l) {
+    } else if (l !== 0) {
       let match$2 = l.tl;
-      if (match$2) {
+      if (match$2 !== 0) {
         let x2$1 = match$2.hd;
         let x1$1 = l.hd;
         let c$6 = cmp(x1$1, x2$1);
@@ -1371,10 +1371,10 @@ function sort_uniq(cmp, l) {
       let accu = _accu;
       let l2$1 = _l2;
       let l1 = _l1;
-      if (!l1) {
+      if (l1 === 0) {
         return rev_append(l2$1, accu);
       }
-      if (!l2$1) {
+      if (l2$1 === 0) {
         return rev_append(l1, accu);
       }
       let t2 = l2$1.tl;
@@ -1415,6 +1415,14 @@ function sort_uniq(cmp, l) {
   }
 }
 
+function isEmpty(x) {
+  return x === 0;
+}
+
+function isEmpty2(x) {
+  return x === /* [] */0;
+}
+
 let u = Belt_List.length;
 
 let append = Pervasives.$at;
@@ -1475,5 +1483,7 @@ export {
   sort,
   fast_sort,
   sort_uniq,
+  isEmpty,
+  isEmpty2,
 }
 /* No side effect */
diff --git a/tests/tests/src/test_list.res b/tests/tests/src/test_list.res
index 915566e571..44b9db0ac1 100644
--- a/tests/tests/src/test_list.res
+++ b/tests/tests/src/test_list.res
@@ -612,3 +612,11 @@ let sort_uniq = (cmp, l) => {
     sort(len, l)
   }
 }
+
+let isEmpty = x =>
+  switch x {
+  | list{} => true
+  | _ => false
+  }
+
+let isEmpty2 = x => x == list{} ? true : false
diff --git a/tests/tests/src/test_seq.mjs b/tests/tests/src/test_seq.mjs
index b436695590..574bfbfdd9 100644
--- a/tests/tests/src/test_seq.mjs
+++ b/tests/tests/src/test_seq.mjs
@@ -13,7 +13,7 @@ let Stop = /* @__PURE__ */Primitive_exceptions.create("Test_seq.Stop");
 function assoc3(x, _l) {
   while (true) {
     let l = _l;
-    if (l) {
+    if (l !== 0) {
       let match = l.hd;
       if (Primitive_object.equal(match[0], x)) {
         return match[1];
diff --git a/tests/tests/src/test_set.mjs b/tests/tests/src/test_set.mjs
index 73fdff0f7c..7be82024e1 100644
--- a/tests/tests/src/test_set.mjs
+++ b/tests/tests/src/test_set.mjs
@@ -554,7 +554,7 @@ function Make(Ord) {
             l
           ];
         case 1 :
-          if (l) {
+          if (l !== 0) {
             return [
               {
                 TAG: "Node",
@@ -568,9 +568,9 @@ function Make(Ord) {
           }
           break;
         case 2 :
-          if (l) {
+          if (l !== 0) {
             let match = l.tl;
-            if (match) {
+            if (match !== 0) {
               return [
                 {
                   TAG: "Node",
@@ -592,11 +592,11 @@ function Make(Ord) {
           }
           break;
         case 3 :
-          if (l) {
+          if (l !== 0) {
             let match$1 = l.tl;
-            if (match$1) {
+            if (match$1 !== 0) {
               let match$2 = match$1.tl;
-              if (match$2) {
+              if (match$2 !== 0) {
                 return [
                   {
                     TAG: "Node",
@@ -629,7 +629,7 @@ function Make(Ord) {
       let nl = n / 2 | 0;
       let match$3 = sub(nl, l);
       let l$1 = match$3[1];
-      if (l$1) {
+      if (l$1 !== 0) {
         let match$4 = sub((n - nl | 0) - 1 | 0, l$1.tl);
         return [
           create(match$3[0], l$1.hd, match$4[0]),
@@ -649,28 +649,28 @@ function Make(Ord) {
     return sub(Belt_List.length(l), l)[0];
   };
   let of_list = l => {
-    if (!l) {
+    if (l === 0) {
       return "Empty";
     }
     let match = l.tl;
     let x0 = l.hd;
-    if (!match) {
+    if (match === 0) {
       return singleton(x0);
     }
     let match$1 = match.tl;
     let x1 = match.hd;
-    if (!match$1) {
+    if (match$1 === 0) {
       return add(x1, singleton(x0));
     }
     let match$2 = match$1.tl;
     let x2 = match$1.hd;
-    if (!match$2) {
+    if (match$2 === 0) {
       return add(x2, add(x1, singleton(x0)));
     }
     let match$3 = match$2.tl;
     let x3 = match$2.hd;
-    if (match$3) {
-      if (match$3.tl) {
+    if (match$3 !== 0) {
+      if (match$3.tl !== 0) {
         return of_sorted_list(Belt_List.sort(l, Ord.compare));
       } else {
         return add(match$3.hd, add(x3, add(x2, add(x1, singleton(x0)))));
diff --git a/tests/tests/src/test_simple_tailcall.mjs b/tests/tests/src/test_simple_tailcall.mjs
index 48ae85ce9c..180ee03a16 100644
--- a/tests/tests/src/test_simple_tailcall.mjs
+++ b/tests/tests/src/test_simple_tailcall.mjs
@@ -8,7 +8,7 @@ function tailcall(x) {
 }
 
 function non_length(x) {
-  if (x) {
+  if (x !== 0) {
     return 1 + non_length(x.tl) | 0;
   } else {
     return 0;
@@ -19,11 +19,11 @@ function length(_acc, _x) {
   while (true) {
     let x = _x;
     let acc = _acc;
-    if (!x) {
+    if (x === 0) {
       return acc;
     }
     let tl = x.tl;
-    if (tl) {
+    if (tl !== 0) {
       return 1 + length(acc + 1 | 0, tl.tl) | 0;
     }
     _x = tl;
diff --git a/tests/tests/src/ticker.mjs b/tests/tests/src/ticker.mjs
index a4eca36b56..aa5dd34648 100644
--- a/tests/tests/src/ticker.mjs
+++ b/tests/tests/src/ticker.mjs
@@ -208,20 +208,20 @@ function process_input_line(ticker_map, all_tickers, line) {
     };
   };
   let tokens = split("|", line);
-  if (!tokens) {
+  if (tokens === 0) {
     return Pervasives.failwith("Invalid input line");
   }
   switch (tokens.hd) {
     case "Q" :
       let match = tokens.tl;
-      if (!match) {
+      if (match === 0) {
         return Pervasives.failwith("Invalid input line");
       }
       let match$1 = match.tl;
-      if (!match$1) {
+      if (match$1 === 0) {
         return Pervasives.failwith("Invalid input line");
       }
-      if (match$1.tl) {
+      if (match$1.tl !== 0) {
         return Pervasives.failwith("Invalid input line");
       }
       let ticker_map$1 = ticker_map !== undefined ? Primitive_option.valFromOption(ticker_map) : compute_update_sequences(all_tickers);
@@ -233,22 +233,22 @@ function process_input_line(ticker_map, all_tickers, line) {
       ];
     case "R" :
       let match$2 = tokens.tl;
-      if (!match$2) {
+      if (match$2 === 0) {
         return Pervasives.failwith("Invalid input line");
       }
       let match$3 = match$2.tl;
-      if (!match$3) {
+      if (match$3 === 0) {
         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) {
+          if (match$4 === 0) {
             return Pervasives.failwith("Invalid input line");
           }
           let match$5 = match$4.tl;
-          if (match$5 && !match$5.tl) {
+          if (match$5 !== 0 && match$5.tl === 0) {
             return [
               {
                 hd: make_binary_op(ticker_name, match$4.hd, match$5.hd, "PLUS"),
@@ -261,11 +261,11 @@ function process_input_line(ticker_map, all_tickers, line) {
           }
         case "-" :
           let match$6 = match$3.tl;
-          if (!match$6) {
+          if (match$6 === 0) {
             return Pervasives.failwith("Invalid input line");
           }
           let match$7 = match$6.tl;
-          if (match$7 && !match$7.tl) {
+          if (match$7 !== 0 && match$7.tl === 0) {
             return [
               {
                 hd: make_binary_op(ticker_name, match$6.hd, match$7.hd, "MINUS"),
@@ -277,7 +277,7 @@ function process_input_line(ticker_map, all_tickers, line) {
             return Pervasives.failwith("Invalid input line");
           }
         case "S" :
-          if (match$3.tl) {
+          if (match$3.tl !== 0) {
             return Pervasives.failwith("Invalid input line");
           } else {
             return [
@@ -306,7 +306,7 @@ function loop(_lines, _param) {
     let param = _param;
     let lines = _lines;
     let all_tickers = param[0];
-    if (!lines) {
+    if (lines === 0) {
       return print_all_composite(all_tickers);
     }
     _param = process_input_line(param[1], all_tickers, lines.hd);
diff --git a/tests/tests/src/topsort_test.mjs b/tests/tests/src/topsort_test.mjs
index 2dc512b66a..017e284e7c 100644
--- a/tests/tests/src/topsort_test.mjs
+++ b/tests/tests/src/topsort_test.mjs
@@ -73,7 +73,7 @@ function dfs1(_nodes, graph, _visited) {
   while (true) {
     let visited = _visited;
     let nodes = _nodes;
-    if (!nodes) {
+    if (nodes === 0) {
       return Belt_List.reverse(visited);
     }
     let xs = nodes.tl;
@@ -171,7 +171,7 @@ function dfs2(nodes, graph, visited) {
     while (true) {
       let visited = _visited;
       let nodes = _nodes;
-      if (!nodes) {
+      if (nodes === 0) {
         return visited;
       }
       let xs = nodes.tl;
@@ -539,13 +539,13 @@ try {
   let exit = 0;
   if (exn.RE_EXN_ID === Cycle) {
     let match = exn._1;
-    if (match && match.hd === "go") {
+    if (match !== 0 && match.hd === "go") {
       let match$1 = match.tl;
-      if (match$1 && match$1.hd === "washup") {
+      if (match$1 !== 0 && match$1.hd === "washup") {
         let match$2 = match$1.tl;
-        if (match$2 && match$2.hd === "eat") {
+        if (match$2 !== 0 && match$2.hd === "eat") {
           let match$3 = match$2.tl;
-          if (!(match$3 && !(match$3.hd !== "go" || match$3.tl))) {
+          if (match$3 === 0 || match$3.hd !== "go" || match$3.tl !== 0) {
             exit = 1;
           }
           
diff --git a/tests/tests/src/variantsMatching.mjs b/tests/tests/src/variantsMatching.mjs
index 4e367a3740..0ee83a8320 100644
--- a/tests/tests/src/variantsMatching.mjs
+++ b/tests/tests/src/variantsMatching.mjs
@@ -82,22 +82,22 @@ function showToJs(x) {
 }
 
 function third(l) {
-  if (!l) {
+  if (l === 0) {
     return false;
   }
   if (l.hd !== 1) {
     return false;
   }
   let match = l.tl;
-  if (!match) {
+  if (match === 0) {
     return false;
   }
   if (match.hd !== 2) {
     return false;
   }
   let match$1 = match.tl;
-  if (match$1 && match$1.hd === 3) {
-    return !match$1.tl;
+  if (match$1 !== 0 && match$1.hd === 3) {
+    return match$1.tl === 0;
   } else {
     return false;
   }