fix: preserve error subtype through serialize

cjs/deserialize.js

@@ -65,7 +65,7 @@ const deserializer = ($, _) => {
       }
       case ERROR: {
         const {name, message} = value;
-        return as(guard(name, message), index);
+        return as(typeof env[name] === 'function' ? guard(name, message) : new Error(message), index);
       }
       case BIGINT:
         return as(BigInt(value), index);

cjs/serialize.js

@@ -34,8 +34,8 @@ const typeOf = value => {
   if (asString.includes('Array'))
     return [ARRAY, asString];
 
-  if (asString.includes('Error'))
-    return [ERROR, asString];
+  if (value instanceof Error)
+    return [ERROR, value.name];
 
   return [OBJECT, asString];
 };

esm/deserialize.js

@@ -67,7 +67,7 @@ const deserializer = ($, _) => {
       }
       case ERROR: {
         const {name, message} = value;
-        return as(guard(name, message), index);
+        return as(typeof env[name] === 'function' ? guard(name, message) : new Error(message), index);
       }
       case BIGINT:
         return as(BigInt(value), index);

esm/serialize.js

@@ -36,8 +36,8 @@ const typeOf = value => {
   if (asString.includes('Array'))
     return [ARRAY, asString];
 
-  if (asString.includes('Error'))
-    return [ERROR, asString];
+  if (value instanceof Error)
+    return [ERROR, value.name];
 
   return [OBJECT, asString];
 };

test/index.js

@@ -168,4 +168,27 @@ const invalidViaJSON = parse(stringify(invalidDate));
 assert(invalidViaJSON instanceof Date, true);
 assert(Number.isNaN(invalidViaJSON.getTime()), true);
 
+// error subtypes must round-trip to their own constructor like native structuredClone
+for (const Class of [Error, EvalError, RangeError, ReferenceError, SyntaxError, TypeError, URIError]) {
+  const errorViaRecord = deserialize(serialize(new Class('boom')));
+  assert(errorViaRecord instanceof Class, true, `${Class.name} must clone as ${Class.name}`);
+  assert(errorViaRecord.name, Class.name);
+  assert(errorViaRecord.message, 'boom');
+}
+
+// a custom-named error (name is not a global constructor) must serialize its real name,
+// then revive as a plain Error, exactly like native structuredClone does
+{
+  const custom = new Error('boom');
+  custom.name = 'CustomBunError';
+  // serialize must preserve the actual name, not fall back to 'Error'
+  assert(serialize(custom)[0][1].name, 'CustomBunError', 'serialize must preserve the custom error name');
+  const viaRecord = deserialize(serialize(custom));
+  const native = globalThis.structuredClone(custom);
+  assert(viaRecord instanceof Error, true, 'custom error must revive as Error');
+  assert(viaRecord.constructor, native.constructor, 'custom error must match native constructor');
+  assert(viaRecord.message, native.message);
+  assert(viaRecord.name, native.name);
+}
+
 require('./eval.js');