diff --git a/CHANGELOG.md b/CHANGELOG.md
index 200f135ac4..8ec1477e07 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -54,6 +54,8 @@
 - Provide additional context in error message when `unit` is expected. https://github.com/rescript-lang/rescript-compiler/pull/7045
 - Improve error message when passing an object where a record is expected. https://github.com/rescript-lang/rescript-compiler/pull/7101
 - Improve code generation or pattern matching of untagged variants. https://github.com/rescript-lang/rescript-compiler/pull/7128
+- Improve negation handling in combination with and/or to simplify generated code (especially coming out of pattern matching). https://github.com/rescript-lang/rescript-compiler/pull/7138
+
 
 #### :house: Internal
 
diff --git a/compiler/core/js_exp_make.ml b/compiler/core/js_exp_make.ml
index 884bdfed7d..7b99ae9e21 100644
--- a/compiler/core/js_exp_make.ml
+++ b/compiler/core/js_exp_make.ml
@@ -665,6 +665,36 @@ let bin ?comment (op : J.binop) (e0 : t) (e1 : t) : t =
 let string_of_expression = ref (fun _ -> "")
 let debug = false
 
+(**
+  [push_negation e] attempts to simplify a negated expression by pushing the negation
+  deeper into the expression tree. Returns [Some simplified] if simplification is possible,
+  [None] otherwise.
+
+  Simplification rules:
+  - [!(not e)] -> [e]
+  - [!true] -> [false]
+  - [!false] -> [true]
+  - [!(a === b)] -> [a !== b]
+  - [!(a !== b)] -> [a === b]
+  - [!(a && b)] -> [!a || !b]  (De Morgan's law)
+  - [!(a || b)] -> [!a && !b]  (De Morgan's law)
+*)
+let rec push_negation (e : t) : t option =
+  match e.expression_desc with
+  | Js_not e -> Some e
+  | Bool b -> Some (bool (not b))
+  | Bin (EqEqEq, a, b) -> Some {e with expression_desc = Bin (NotEqEq, a, b)}
+  | Bin (NotEqEq, a, b) -> Some {e with expression_desc = Bin (EqEqEq, a, b)}
+  | Bin (And, a, b) -> (
+    match (push_negation a, push_negation b) with
+    | Some a_, Some b_ -> Some {e with expression_desc = Bin (Or, a_, b_)}
+    | _ -> None)
+  | Bin (Or, a, b) -> (
+    match (push_negation a, push_negation b) with
+    | Some a_, Some b_ -> Some {e with expression_desc = Bin (And, a_, b_)}
+    | _ -> None)
+  | _ -> None
+
 (**
   [simplify_and e1 e2] attempts to simplify the boolean AND expression [e1 && e2].
   Returns [Some simplified] if simplification is possible, [None] otherwise.
@@ -681,7 +711,16 @@ let debug = false
 
   Type check optimizations:
   - [(typeof x === "boolean") && (x === true/false)] -> [x === true/false]
-  - [(typeof x === "string" || Array.isArray(x)) && (x === boolean/null/undefined)] -> [false]
+  - [(typeof x ==="boolean" | "string" | "number") && (x === boolean/null/undefined)] -> [false]
+  - [(Array.isArray(x)) && (x === boolean/null/undefined)] -> [false]
+
+  - [(typeof x === "boolean") && (x !== true/false)] -> unchanged
+  - [(typeof x === "boolean" | "string" | "number") && (x !== boolean/null/undefined)] -> [typeof x === ...]
+  - [(Array.isArray(x)) && (x !== boolean/null/undefined)] -> [Array.isArray(x)]
+
+  Equality optimizations:
+  - [e && e] -> [e]
+  - [(x === boolean/null/undefined) && (x === boolean/null/undefined)] -> [false] (when not equal)
 
   Note: The function preserves the semantics of the original expression while
   attempting to reduce it to a simpler form. If no simplification is possible,
@@ -691,7 +730,6 @@ let rec simplify_and (e1 : t) (e2 : t) : t option =
   if debug then
     Printf.eprintf "simplify_and %s %s\n" (!string_of_expression e1)
       (!string_of_expression e2);
-
   match (e1.expression_desc, e2.expression_desc) with
   | Bool false, _ -> Some false_
   | _, Bool false -> Some false_
@@ -700,39 +738,21 @@ let rec simplify_and (e1 : t) (e2 : t) : t option =
   | Bin (And, a, b), _ -> (
     let ao = simplify_and a e2 in
     let bo = simplify_and b e2 in
-    if ao = None && bo = None then None
-    else
-      let a_ =
-        match ao with
-        | None -> a
-        | Some a_ -> a_
-      in
-      let b_ =
-        match bo with
-        | None -> b
-        | Some b_ -> b_
-      in
+    match (ao, bo) with
+    | None, _ | _, None -> None
+    | Some a_, Some b_ -> (
       match simplify_and a_ b_ with
       | None -> Some {expression_desc = Bin (And, a_, b_); comment = None}
-      | Some e -> Some e)
+      | Some e -> Some e))
   | Bin (Or, a, b), _ -> (
     let ao = simplify_and a e2 in
     let bo = simplify_and b e2 in
-    if ao = None && bo = None then None
-    else
-      let a_ =
-        match ao with
-        | None -> a
-        | Some a_ -> a_
-      in
-      let b_ =
-        match bo with
-        | None -> b
-        | Some b_ -> b_
-      in
+    match (ao, bo) with
+    | None, _ | _, None -> None
+    | Some a_, Some b_ -> (
       match simplify_or a_ b_ with
       | None -> Some {expression_desc = Bin (Or, a_, b_); comment = None}
-      | Some e -> Some e)
+      | Some e -> Some e))
   | ( Bin
         ( ((EqEqEq | NotEqEq) as op1),
           {expression_desc = Var i1},
@@ -760,15 +780,8 @@ let rec simplify_and (e1 : t) (e2 : t) : t option =
     Some {expression_desc = b; comment = None}
   | ( Bin
         ( EqEqEq,
-          {
-            expression_desc =
-              ( Typeof {expression_desc = Var ia}
-              | Call
-                  ( {expression_desc = Str {txt = "Array.isArray"}},
-                    [{expression_desc = Var ia}],
-                    _ ) );
-          },
-          {expression_desc = Str {txt = "boolean" | "string"}} ),
+          {expression_desc = Typeof {expression_desc = Var ia}},
+          {expression_desc = Str {txt = "boolean" | "string" | "number"}} ),
       Bin
         ( EqEqEq,
           {expression_desc = Var ib},
@@ -779,17 +792,91 @@ let rec simplify_and (e1 : t) (e2 : t) : t option =
           {expression_desc = Bool _ | Null | Undefined _} ),
       Bin
         ( EqEqEq,
-          {
-            expression_desc =
-              ( Typeof {expression_desc = Var ia}
-              | Call
-                  ( {expression_desc = Str {txt = "Array.isArray"}},
-                    [{expression_desc = Var ia}],
-                    _ ) );
-          },
-          {expression_desc = Str {txt = "boolean" | "string"}} ) )
+          {expression_desc = Typeof {expression_desc = Var ia}},
+          {expression_desc = Str {txt = "boolean" | "string" | "number"}} ) )
+    when Js_op_util.same_vident ia ib ->
+    (* Note: case boolean / Bool _ is handled above *)
+    Some false_
+  | ( Call
+        ( {expression_desc = Str {txt = "Array.isArray"}},
+          [{expression_desc = Var ia}],
+          _ ),
+      Bin
+        ( EqEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ) )
+  | ( Bin
+        ( EqEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ),
+      Call
+        ( {expression_desc = Str {txt = "Array.isArray"}},
+          [{expression_desc = Var ia}],
+          _ ) )
+    when Js_op_util.same_vident ia ib ->
+    Some false_
+  | ( Bin
+        ( EqEqEq,
+          {expression_desc = Typeof {expression_desc = Var ia}},
+          {expression_desc = Str {txt = "boolean"}} ),
+      Bin (NotEqEq, {expression_desc = Var ib}, {expression_desc = Bool _}) )
+  | ( Bin (NotEqEq, {expression_desc = Var ib}, {expression_desc = Bool _}),
+      Bin
+        ( EqEqEq,
+          {expression_desc = Typeof {expression_desc = Var ia}},
+          {expression_desc = Str {txt = "boolean"}} ) )
+    when Js_op_util.same_vident ia ib ->
+    None
+  | ( (Bin
+         ( EqEqEq,
+           {expression_desc = Typeof {expression_desc = Var ia}},
+           {expression_desc = Str {txt = "boolean" | "string" | "number"}} ) as
+       typeof),
+      Bin
+        ( NotEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ) )
+  | ( Bin
+        ( NotEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ),
+      (Bin
+         ( EqEqEq,
+           {expression_desc = Typeof {expression_desc = Var ia}},
+           {expression_desc = Str {txt = "boolean" | "string" | "number"}} ) as
+       typeof) )
     when Js_op_util.same_vident ia ib ->
     (* Note: case boolean / Bool _ is handled above *)
+    Some {expression_desc = typeof; comment = None}
+  | ( (Call
+         ( {expression_desc = Str {txt = "Array.isArray"}},
+           [{expression_desc = Var ia}],
+           _ ) as is_array),
+      Bin
+        ( NotEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ) )
+  | ( Bin
+        ( NotEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ),
+      (Call
+         ( {expression_desc = Str {txt = "Array.isArray"}},
+           [{expression_desc = Var ia}],
+           _ ) as is_array) )
+    when Js_op_util.same_vident ia ib ->
+    Some {expression_desc = is_array; comment = None}
+  | x, y when x = y -> Some e1
+  | ( Bin
+        ( EqEqEq,
+          {expression_desc = Var ia},
+          {expression_desc = Bool _ | Null | Undefined _} ),
+      Bin
+        ( EqEqEq,
+          {expression_desc = Var ib},
+          {expression_desc = Bool _ | Null | Undefined _} ) )
+    when Js_op_util.same_vident ia ib ->
+    (* Note: case x = y is handled above *)
     Some false_
   | _ -> None
 
@@ -802,6 +889,16 @@ let rec simplify_and (e1 : t) (e2 : t) : t option =
   - [e || true] -> [true]
   - [false || e] -> [e]
   - [e || false] -> [e]
+
+  Algebraic transformation strategy:
+  When basic rules don't apply, attempts to leverage [simplify_and] by:
+  1. Using the equivalence: [e1 || e2 ≡ !(!(e1) && !(e2))]
+  2. Applying [push_negation] to get [!(e1)] and [!(e2)]
+  3. Using [simplify_and] on these negated terms
+  4. If successful, applying [push_negation] again to get the final result
+
+  This transformation allows reuse of [simplify_and]'s more extensive optimizations
+  in the context of OR expressions.
 *)
 and simplify_or (e1 : t) (e2 : t) : t option =
   if debug then
@@ -813,7 +910,13 @@ and simplify_or (e1 : t) (e2 : t) : t option =
   | _, Bool true -> Some true_
   | Bool false, _ -> Some e2
   | _, Bool false -> Some e1
-  | _ -> None
+  | _ -> (
+    match (push_negation e1, push_negation e2) with
+    | Some e1_, Some e2_ -> (
+      match simplify_and e1_ e2_ with
+      | Some e -> push_negation e
+      | None -> None)
+    | _ -> None)
 
 let and_ ?comment (e1 : t) (e2 : t) : t =
   match (e1.expression_desc, e2.expression_desc) with
@@ -874,6 +977,7 @@ let rec econd ?comment (pred : t) (ifso : t) (ifnot : t) : t =
   | (Number _ | Array _ | Caml_block _), _, _ when no_side_effect pred ->
     ifso (* a block can not be false in OCAML, CF - relies on flow inference*)
   | Bool true, _, _ -> ifso
+  | _, Bool true, Bool false -> pred
   | _, Cond (pred1, ifso1, ifnot1), _
     when Js_analyzer.eq_expression ifnot1 ifnot ->
     (* {[
diff --git a/lib/es6/Belt_Result.js b/lib/es6/Belt_Result.js
index 54b73dcfa8..b83195146a 100644
--- a/lib/es6/Belt_Result.js
+++ b/lib/es6/Belt_Result.js
@@ -53,11 +53,7 @@ function getWithDefault(opt, $$default) {
 }
 
 function isOk(x) {
-  if (x.TAG === "Ok") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Ok";
 }
 
 function isError(x) {
diff --git a/lib/es6/Result.js b/lib/es6/Result.js
index bda5bad6c7..5b5023054f 100644
--- a/lib/es6/Result.js
+++ b/lib/es6/Result.js
@@ -47,11 +47,7 @@ function getOr(opt, $$default) {
 }
 
 function isOk(x) {
-  if (x.TAG === "Ok") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Ok";
 }
 
 function isError(x) {
diff --git a/lib/js/Belt_Result.js b/lib/js/Belt_Result.js
index e221ef9d71..0aba2f6f5c 100644
--- a/lib/js/Belt_Result.js
+++ b/lib/js/Belt_Result.js
@@ -53,11 +53,7 @@ function getWithDefault(opt, $$default) {
 }
 
 function isOk(x) {
-  if (x.TAG === "Ok") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Ok";
 }
 
 function isError(x) {
diff --git a/lib/js/Result.js b/lib/js/Result.js
index d29b38e588..b0c9638920 100644
--- a/lib/js/Result.js
+++ b/lib/js/Result.js
@@ -47,11 +47,7 @@ function getOr(opt, $$default) {
 }
 
 function isOk(x) {
-  if (x.TAG === "Ok") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Ok";
 }
 
 function isError(x) {
diff --git a/scripts/test.js b/scripts/test.js
index f9f10465f0..8a88795650 100644
--- a/scripts/test.js
+++ b/scripts/test.js
@@ -60,7 +60,12 @@ async function runTests() {
   }
 
   if (mochaTest) {
-    cp.execSync(rescript_exe, {
+    cp.execSync(`${rescript_exe} clean`, {
+      cwd: path.join(__dirname, "..", "tests/tests"),
+      stdio: [0, 1, 2],
+    });
+
+    cp.execSync(`${rescript_exe} build`, {
       cwd: path.join(__dirname, "..", "tests/tests"),
       stdio: [0, 1, 2],
     });
diff --git a/tests/tests/src/UntaggedVariants.mjs b/tests/tests/src/UntaggedVariants.mjs
index f1755ab616..6043df57ac 100644
--- a/tests/tests/src/UntaggedVariants.mjs
+++ b/tests/tests/src/UntaggedVariants.mjs
@@ -386,9 +386,9 @@ function check$1(s) {
       return;
     }
     let match = s[0];
-    if (match === undefined || match === null || match === true) {
+    if (match === true) {
       let match$1 = s[1];
-      if (match$1 === undefined || match$1 === null || match$1 === false) {
+      if (match$1 === false) {
         let match$2 = s[2];
         if (match$2 === undefined || match$2 === null || match$2 === false || match$2 === true) {
           console.log("Nope...");
diff --git a/tests/tests/src/and_or_simplify.mjs b/tests/tests/src/and_or_simplify.mjs
index 9f12c3b8b3..968359e1b8 100644
--- a/tests/tests/src/and_or_simplify.mjs
+++ b/tests/tests/src/and_or_simplify.mjs
@@ -2,15 +2,11 @@
 
 
 function check_null_eq_typeof(x) {
-  if (typeof x !== "boolean" || x !== null) {
-    return 4;
-  } else {
-    return 3;
-  }
+  return 4;
 }
 
 function check_null_neq_typeof(x) {
-  if (typeof x !== "boolean" || x === null) {
+  if (typeof x !== "boolean") {
     return 4;
   } else {
     return 3;
@@ -18,15 +14,11 @@ function check_null_neq_typeof(x) {
 }
 
 function check_undefined_eq_typeof(x) {
-  if (typeof x !== "boolean" || x !== undefined) {
-    return 4;
-  } else {
-    return 3;
-  }
+  return 4;
 }
 
 function check_undefined_neq_typeof(x) {
-  if (typeof x !== "boolean" || x === undefined) {
+  if (typeof x !== "boolean") {
     return 4;
   } else {
     return 3;
diff --git a/tests/tests/src/and_or_simplify.res b/tests/tests/src/and_or_simplify.res
index 2b4520cb4f..fde19c7337 100644
--- a/tests/tests/src/and_or_simplify.res
+++ b/tests/tests/src/and_or_simplify.res
@@ -1,5 +1,5 @@
 @unboxed
-type t = | @as(null) Null | @as(undefined) Undefined | B(bool) //| S(string)
+type t = | @as(null) Null | @as(undefined) Undefined | B(bool) | S(string) | I(int)
 
 let check_null_eq_typeof = x =>
   switch x {
diff --git a/tests/tests/src/bdd.mjs b/tests/tests/src/bdd.mjs
index 7f9dfe1b01..dd2b767d28 100644
--- a/tests/tests/src/bdd.mjs
+++ b/tests/tests/src/bdd.mjs
@@ -7,11 +7,7 @@ function $$eval(_bdd, vars) {
   while (true) {
     let bdd = _bdd;
     if (typeof bdd !== "object") {
-      if (bdd === "One") {
-        return true;
-      } else {
-        return false;
-      }
+      return bdd === "One";
     }
     if (Primitive_array.get(vars, bdd._1)) {
       _bdd = bdd._3;
@@ -366,11 +362,7 @@ function random_vars(n) {
 
 function bool_equal(a, b) {
   if (a) {
-    if (b) {
-      return true;
-    } else {
-      return false;
-    }
+    return b;
   } else if (b) {
     return false;
   } else {
diff --git a/tests/tests/src/caml_compare_test.mjs b/tests/tests/src/caml_compare_test.mjs
index 073733b27f..d5e03d0573 100644
--- a/tests/tests/src/caml_compare_test.mjs
+++ b/tests/tests/src/caml_compare_test.mjs
@@ -10,7 +10,7 @@ try {
   function_equal_test = Primitive_object.equal(x => x + 1 | 0, x => x + 2 | 0);
 } catch (raw_exn) {
   let exn = Primitive_exceptions.internalToException(raw_exn);
-  function_equal_test = exn.RE_EXN_ID === "Invalid_argument" && exn._1 === "equal: functional value" ? true : false;
+  function_equal_test = exn.RE_EXN_ID === "Invalid_argument" ? exn._1 === "equal: functional value" : false;
 }
 
 let suites = {
diff --git a/tests/tests/src/core/Core_JsonTests.mjs b/tests/tests/src/core/Core_JsonTests.mjs
index 0ddd7e6628..1f4ff3bfc5 100644
--- a/tests/tests/src/core/Core_JsonTests.mjs
+++ b/tests/tests/src/core/Core_JsonTests.mjs
@@ -17,7 +17,7 @@ function decodeJsonTest() {
           decodedCorrectly = false;
         } else {
           let match$3 = match$1[1];
-          decodedCorrectly = match$3 === null || !(typeof match$3 === "boolean" && !match$3) ? false : true;
+          decodedCorrectly = match$3 === null ? false : typeof match$3 === "boolean" && !match$3;
         }
       } else {
         decodedCorrectly = false;
diff --git a/tests/tests/src/core/Core_NullableTests.mjs b/tests/tests/src/core/Core_NullableTests.mjs
index 072aa64f28..c97c71a499 100644
--- a/tests/tests/src/core/Core_NullableTests.mjs
+++ b/tests/tests/src/core/Core_NullableTests.mjs
@@ -7,7 +7,7 @@ function shouldHandleNullableValues() {
   let tUndefined = undefined;
   let tValue = "hello";
   let tmp;
-  tmp = (tNull === null || tNull === undefined) && tNull === null ? true : false;
+  tmp = tNull === null || tNull === undefined ? tNull === null : false;
   Test.run([
     [
       "Core_NullableTests.res",
@@ -18,7 +18,7 @@ function shouldHandleNullableValues() {
     "Should handle null"
   ], tmp, (prim0, prim1) => prim0 === prim1, true);
   let tmp$1;
-  tmp$1 = (tUndefined === null || tUndefined === undefined) && tUndefined !== null ? true : false;
+  tmp$1 = (tUndefined === null || tUndefined === undefined) && tUndefined !== null;
   Test.run([
     [
       "Core_NullableTests.res",
@@ -29,7 +29,7 @@ function shouldHandleNullableValues() {
     "Should handle undefined"
   ], tmp$1, (prim0, prim1) => prim0 === prim1, true);
   let tmp$2;
-  tmp$2 = tValue === null || tValue === undefined || tValue !== "hello" ? false : true;
+  tmp$2 = tValue === null || tValue === undefined ? false : tValue === "hello";
   Test.run([
     [
       "Core_NullableTests.res",
diff --git a/tests/tests/src/core/Core_PromiseTest.mjs b/tests/tests/src/core/Core_PromiseTest.mjs
index f054f6895c..c3b23fa1ff 100644
--- a/tests/tests/src/core/Core_PromiseTest.mjs
+++ b/tests/tests/src/core/Core_PromiseTest.mjs
@@ -171,7 +171,7 @@ function testExnThrow() {
       Error: new Error()
     };
   }), e => {
-    let isTestErr = e.RE_EXN_ID === TestError && e._1 === "Thrown exn" ? true : false;
+    let isTestErr = e.RE_EXN_ID === TestError ? e._1 === "Thrown exn" : false;
     Test.run([
       [
         "Core_PromiseTest.res",
diff --git a/tests/tests/src/gpr496_test.mjs b/tests/tests/src/gpr496_test.mjs
index 99190d9362..06a2d01662 100644
--- a/tests/tests/src/gpr496_test.mjs
+++ b/tests/tests/src/gpr496_test.mjs
@@ -67,7 +67,7 @@ function ff(x, y) {
   return Primitive_bool.min(x, y());
 }
 
-eq("File \"gpr496_test.res\", line 40, characters 12-19", true < false ? true : false, false);
+eq("File \"gpr496_test.res\", line 40, characters 12-19", true < false, false);
 
 Mt.from_pair_suites("Gpr496_test", suites.contents);
 
diff --git a/tests/tests/src/gpr_1698_test.mjs b/tests/tests/src/gpr_1698_test.mjs
index 947fa0a4f2..2da2cd456d 100644
--- a/tests/tests/src/gpr_1698_test.mjs
+++ b/tests/tests/src/gpr_1698_test.mjs
@@ -6,11 +6,7 @@ function is_number(_expr) {
     let expr = _expr;
     switch (expr.TAG) {
       case "Val" :
-        if (expr._0.TAG === "Natural") {
-          return true;
-        } else {
-          return false;
-        }
+        return expr._0.TAG === "Natural";
       case "Neg" :
         _expr = expr._0;
         continue;
diff --git a/tests/tests/src/gpr_4924_test.mjs b/tests/tests/src/gpr_4924_test.mjs
index 26cbb2f36e..fc3b42303d 100644
--- a/tests/tests/src/gpr_4924_test.mjs
+++ b/tests/tests/src/gpr_4924_test.mjs
@@ -19,8 +19,8 @@ function u(b) {
 }
 
 function u1(b) {
-  if (typeof b !== "object" && b === "A") {
-    return true;
+  if (typeof b !== "object") {
+    return b === "A";
   } else {
     return false;
   }
@@ -65,8 +65,8 @@ function u5(b) {
 }
 
 function u6(b) {
-  if (typeof b !== "object" && b === "A") {
-    return true;
+  if (typeof b !== "object") {
+    return b === "A";
   } else {
     return false;
   }
diff --git a/tests/tests/src/inline_map2_test.mjs b/tests/tests/src/inline_map2_test.mjs
index a31d35a05b..a7bc3535e2 100644
--- a/tests/tests/src/inline_map2_test.mjs
+++ b/tests/tests/src/inline_map2_test.mjs
@@ -81,13 +81,7 @@ function Make(Ord) {
       return create(create(l, x, d, rl._0), rl._1, rl._2, create(rl._3, rv, rd, rr));
     }
   };
-  let is_empty = x => {
-    if (typeof x !== "object") {
-      return true;
-    } else {
-      return false;
-    }
-  };
+  let is_empty = x => typeof x !== "object";
   let add = (x, data, x_) => {
     if (typeof x_ !== "object") {
       return {
@@ -523,11 +517,7 @@ function Make(Ord) {
       let e2 = _e2;
       let e1 = _e1;
       if (typeof e1 !== "object") {
-        if (typeof e2 !== "object") {
-          return true;
-        } else {
-          return false;
-        }
+        return typeof e2 !== "object";
       }
       if (typeof e2 !== "object") {
         return false;
@@ -688,11 +678,7 @@ function bal(l, x, d, r) {
 }
 
 function is_empty(x) {
-  if (typeof x !== "object") {
-    return true;
-  } else {
-    return false;
-  }
+  return typeof x !== "object";
 }
 
 function add(x, data, x_) {
@@ -1154,11 +1140,7 @@ function equal(cmp, m1, m2) {
     let e2 = _e2;
     let e1 = _e1;
     if (typeof e1 !== "object") {
-      if (typeof e2 !== "object") {
-        return true;
-      } else {
-        return false;
-      }
+      return typeof e2 !== "object";
     }
     if (typeof e2 !== "object") {
       return false;
@@ -1350,11 +1332,7 @@ function bal$1(l, x, d, r) {
 }
 
 function is_empty$1(x) {
-  if (typeof x !== "object") {
-    return true;
-  } else {
-    return false;
-  }
+  return typeof x !== "object";
 }
 
 function add$1(x, data, x_) {
@@ -1816,11 +1794,7 @@ function equal$1(cmp, m1, m2) {
     let e2 = _e2;
     let e1 = _e1;
     if (typeof e1 !== "object") {
-      if (typeof e2 !== "object") {
-        return true;
-      } else {
-        return false;
-      }
+      return typeof e2 !== "object";
     }
     if (typeof e2 !== "object") {
       return false;
diff --git a/tests/tests/src/js_bool_test.mjs b/tests/tests/src/js_bool_test.mjs
index bb87a4f7f0..32e6c57c7a 100644
--- a/tests/tests/src/js_bool_test.mjs
+++ b/tests/tests/src/js_bool_test.mjs
@@ -3,27 +3,15 @@
 import * as Mt from "./mt.mjs";
 
 function f(x) {
-  if (x) {
-    return true;
-  } else {
-    return false;
-  }
+  return x;
 }
 
 function f2(x) {
-  if (x) {
-    return true;
-  } else {
-    return false;
-  }
+  return x;
 }
 
 function f4(x) {
-  if (x) {
-    return true;
-  } else {
-    return false;
-  }
+  return x;
 }
 
 let u = 1;
diff --git a/tests/tests/src/mario_game.mjs b/tests/tests/src/mario_game.mjs
index d89d8cc315..3f460365a9 100644
--- a/tests/tests/src/mario_game.mjs
+++ b/tests/tests/src/mario_game.mjs
@@ -928,19 +928,11 @@ function get_obj(x) {
 }
 
 function is_player(x) {
-  if (x.TAG === "Player") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Player";
 }
 
 function is_enemy(x) {
-  if (x.TAG === "Enemy") {
-    return true;
-  } else {
-    return false;
-  }
+  return x.TAG === "Enemy";
 }
 
 function equals(col1, col2) {
@@ -1262,7 +1254,7 @@ function col_bypass(c1, c2) {
       ctypes = c2.TAG === "Enemy" ? c1._2.invuln > 0 : false;
       break;
     case "Enemy" :
-      ctypes = c2.TAG === "Item" ? true : false;
+      ctypes = c2.TAG === "Item";
       break;
     case "Item" :
       switch (c2.TAG) {
diff --git a/tests/tests/src/option_repr_test.mjs b/tests/tests/src/option_repr_test.mjs
index d67be245ef..9f4d0e742b 100644
--- a/tests/tests/src/option_repr_test.mjs
+++ b/tests/tests/src/option_repr_test.mjs
@@ -221,9 +221,9 @@ b("File \"option_repr_test.res\", line 127, characters 3-10", Belt_List.every(xs
 let xs_1$1 = {
   hd: neqx(undefined, null),
   tl: {
-    hd: Primitive_object.equal(Primitive_option.some(undefined), Primitive_option.some(undefined)) && Primitive_object.equal(Primitive_option.some(undefined), Primitive_option.some(undefined)),
+    hd: Primitive_object.equal(Primitive_option.some(undefined), Primitive_option.some(undefined)),
     tl: {
-      hd: Primitive_object.equal(Primitive_option.some(Primitive_option.some(undefined)), Primitive_option.some(Primitive_option.some(undefined))) && Primitive_object.equal(Primitive_option.some(Primitive_option.some(undefined)), Primitive_option.some(Primitive_option.some(undefined))),
+      hd: Primitive_object.equal(Primitive_option.some(Primitive_option.some(undefined)), Primitive_option.some(Primitive_option.some(undefined))),
       tl: {
         hd: Primitive_object.notequal(Primitive_option.some(Primitive_option.some(Primitive_option.some(undefined))), Primitive_option.some(Primitive_option.some(undefined))) && Primitive_object.notequal(Primitive_option.some(Primitive_option.some(undefined)), Primitive_option.some(Primitive_option.some(Primitive_option.some(undefined)))),
         tl: /* [] */0
diff --git a/tests/tests/src/rbset.mjs b/tests/tests/src/rbset.mjs
index 37a65f5e37..258ef6c4e1 100644
--- a/tests/tests/src/rbset.mjs
+++ b/tests/tests/src/rbset.mjs
@@ -22,11 +22,7 @@ function blackify(x) {
 }
 
 function is_empty(x) {
-  if (typeof x !== "object") {
-    return true;
-  } else {
-    return false;
-  }
+  return typeof x !== "object";
 }
 
 function mem(x, _x_) {
diff --git a/tests/tests/src/reasonReactRouter.mjs b/tests/tests/src/reasonReactRouter.mjs
index aae73dc38a..92c3a7013b 100644
--- a/tests/tests/src/reasonReactRouter.mjs
+++ b/tests/tests/src/reasonReactRouter.mjs
@@ -108,11 +108,7 @@ function urlNotEqual(a, b) {
       let bList = _bList;
       let aList = _aList;
       if (!aList) {
-        if (bList) {
-          return true;
-        } else {
-          return false;
-        }
+        return bList;
       }
       if (!bList) {
         return true;
diff --git a/tests/tests/src/set_gen.mjs b/tests/tests/src/set_gen.mjs
index d6ced61c31..c295c5829d 100644
--- a/tests/tests/src/set_gen.mjs
+++ b/tests/tests/src/set_gen.mjs
@@ -67,11 +67,7 @@ function max_elt(_x) {
 }
 
 function is_empty(x) {
-  if (typeof x !== "object") {
-    return true;
-  } else {
-    return false;
-  }
+  return typeof x !== "object";
 }
 
 function cardinal_aux(_acc, _x) {
diff --git a/tests/tests/src/test_bool_equal.mjs b/tests/tests/src/test_bool_equal.mjs
index ad966edbb9..6d0bc4e9d6 100644
--- a/tests/tests/src/test_bool_equal.mjs
+++ b/tests/tests/src/test_bool_equal.mjs
@@ -3,11 +3,7 @@
 
 function bool_equal(x, y) {
   if (x) {
-    if (y) {
-      return true;
-    } else {
-      return false;
-    }
+    return y;
   } else if (y) {
     return false;
   } else {
diff --git a/tests/tests/src/test_set.mjs b/tests/tests/src/test_set.mjs
index 00e9215886..73fdff0f7c 100644
--- a/tests/tests/src/test_set.mjs
+++ b/tests/tests/src/test_set.mjs
@@ -224,13 +224,7 @@ function Make(Ord) {
       match$1[2]
     ];
   };
-  let is_empty = x => {
-    if (typeof x !== "object") {
-      return true;
-    } else {
-      return false;
-    }
-  };
+  let is_empty = x => typeof x !== "object";
   let mem = (x, _x_) => {
     while (true) {
       let x_ = _x_;
diff --git a/tests/tests/src/variantsMatching.mjs b/tests/tests/src/variantsMatching.mjs
index 498102609f..913305dc65 100644
--- a/tests/tests/src/variantsMatching.mjs
+++ b/tests/tests/src/variantsMatching.mjs
@@ -96,11 +96,7 @@ function third(l) {
     return false;
   }
   let match$1 = match.tl;
-  if (match$1 && !(match$1.hd !== 3 || match$1.tl)) {
-    return true;
-  } else {
-    return false;
-  }
+  return match$1 && !(match$1.hd !== 3 || match$1.tl);
 }
 
 function third2(l) {
@@ -125,11 +121,7 @@ function third2(l) {
     return false;
   }
   let tmp = match$1._1;
-  if (typeof tmp !== "object") {
-    return true;
-  } else {
-    return false;
-  }
+  return typeof tmp !== "object";
 }
 
 function foo(x) {