Mystery of class '[object Object]' resolved.

UndefinedObject >> subclass:... sent the symbol object
to the ClassBuilder, unlike Class which asString-ed it.

So `nil subclass: #Object` misbehaved.

js/Kernel-Objects.deploy.js

@@ -3371,11 +3371,11 @@ smalltalk.addMethod(
 "_subclass_instanceVariableNames_package_",
 smalltalk.method({
 selector: "subclass:instanceVariableNames:package:",
-fn: function (aString, aString2, aString3) {
-    var self = this;
-    var $1;
-    $1 = smalltalk.send(smalltalk.send(smalltalk.ClassBuilder || ClassBuilder, "_new", []), "_superclass_subclass_instanceVariableNames_package_", [self, aString, aString2, aString3]);
-    return $1;
+fn: function (aString,aString2,aString3){
+var self=this;
+var $1;
+$1=smalltalk.send(smalltalk.send((smalltalk.ClassBuilder || ClassBuilder),"_new",[]),"_superclass_subclass_instanceVariableNames_package_",[self,smalltalk.send(aString,"_asString",[]),aString2,aString3]);
+return $1;
 }
 }),
 smalltalk.UndefinedObject);

js/Kernel-Objects.js

@@ -4638,15 +4638,15 @@ smalltalk.addMethod(
 smalltalk.method({
 selector: "subclass:instanceVariableNames:package:",
 category: 'class creation',
-fn: function (aString, aString2, aString3) {
-    var self = this;
-    var $1;
-    $1 = smalltalk.send(smalltalk.send(smalltalk.ClassBuilder || ClassBuilder, "_new", []), "_superclass_subclass_instanceVariableNames_package_", [self, aString, aString2, aString3]);
-    return $1;
+fn: function (aString,aString2,aString3){
+var self=this;
+var $1;
+$1=smalltalk.send(smalltalk.send((smalltalk.ClassBuilder || ClassBuilder),"_new",[]),"_superclass_subclass_instanceVariableNames_package_",[self,smalltalk.send(aString,"_asString",[]),aString2,aString3]);
+return $1;
 },
 args: ["aString", "aString2", "aString3"],
-source: "subclass: aString instanceVariableNames: aString2 package: aString3\x0a\x09^ClassBuilder new\x0a\x09    superclass: self subclass: aString instanceVariableNames: aString2 package: aString3",
-messageSends: ["superclass:subclass:instanceVariableNames:package:", "new"],
+source: "subclass: aString instanceVariableNames: aString2 package: aString3\x0a\x09^ClassBuilder new\x0a\x09    superclass: self subclass: aString asString instanceVariableNames: aString2 package: aString3",
+messageSends: ["superclass:subclass:instanceVariableNames:package:", "asString", "new"],
 referencedClasses: ["ClassBuilder"]
 }),
 smalltalk.UndefinedObject);

st/Kernel-Objects.st

@@ -1595,7 +1595,7 @@ subclass: aString instanceVariableNames: aString2 category: aString3
 
 subclass: aString instanceVariableNames: aString2 package: aString3
 	^ClassBuilder new
-	    superclass: self subclass: aString instanceVariableNames: aString2 package: aString3
+	    superclass: self subclass: aString asString instanceVariableNames: aString2 package: aString3
 ! !
 
 !UndefinedObject methodsFor: 'converting'!