Simplify JSON.Decode implementation (#7304)

* Simplify JSON.Decode implementation

* CHANGELOG

Author: cknitt

CHANGELOG.md

@@ -38,7 +38,8 @@
 
 - Remove ignore in res_scanner.ml . https://github.com/rescript-lang/rescript/pull/7280
 - Use the new stdlib modules in the analysis tests. https://github.com/rescript-lang/rescript/pull/7295
-- Build with OCaml 5.3.0. https://github.com/rescript-lang/rescript-compiler/pull/7294
+- Build with OCaml 5.3.0. https://github.com/rescript-lang/rescript/pull/7294
+- Simplify JSON.Decode implementation. https://github.com/rescript-lang/rescript/pull/7304
 
 # 12.0.0-alpha.8
 

lib/es6/Stdlib_JSON.js

@@ -69,7 +69,7 @@ function float(json) {
 }
 
 function object(json) {
-  if (typeof json === "object" && !Array.isArray(json) && json !== null) {
+  if (typeof json === "object" && json !== null && !Array.isArray(json)) {
     return json;
   }
 

lib/js/Stdlib_JSON.js

@@ -69,7 +69,7 @@ function float(json) {
 }
 
 function object(json) {
-  if (typeof json === "object" && !Array.isArray(json) && json !== null) {
+  if (typeof json === "object" && json !== null && !Array.isArray(json)) {
     return json;
   }
 

runtime/Stdlib_JSON.res

@@ -80,22 +80,39 @@ module Encode = {
 }
 
 module Decode = {
-  let bool = (json: t) =>
-    Stdlib_Type.typeof(json) === #boolean ? Some((Obj.magic(json): bool)) : None
-  let null = (json: t) => Obj.magic(json) === Stdlib_Null.null ? Some(Stdlib_Null.null) : None
-  let string = (json: t) =>
-    Stdlib_Type.typeof(json) === #string ? Some((Obj.magic(json): string)) : None
-  let float = (json: t) =>
-    Stdlib_Type.typeof(json) === #number ? Some((Obj.magic(json): float)) : None
-  let object = (json: t) =>
-    if (
-      Stdlib_Type.typeof(json) === #object &&
-      !Stdlib_Array.isArray(json) &&
-      !(Obj.magic(json) === Stdlib_Null.null)
-    ) {
-      Some((Obj.magic(json): dict<t>))
-    } else {
-      None
+  let bool = json =>
+    switch json {
+    | Boolean(b) => Some(b)
+    | _ => None
+    }
+
+  let null = json =>
+    switch json {
+    | Null => Some(Stdlib_Null.null)
+    | _ => None
+    }
+
+  let string = json =>
+    switch json {
+    | String(s) => Some(s)
+    | _ => None
+    }
+
+  let float = json =>
+    switch json {
+    | Number(f) => Some(f)
+    | _ => None
+    }
+
+  let object = json =>
+    switch json {
+    | Object(o) => Some(o)
+    | _ => None
+    }
+
+  let array = (json: t) =>
+    switch json {
+    | Array(a) => Some(a)
+    | _ => None
     }
-  let array = (json: t) => Stdlib_Array.isArray(json) ? Some((Obj.magic(json): array<t>)) : None
 }