Bizarre stack overflow

programming flash
1

Given the following in the document class:

private function onAddedToStage(e:Event):void{
    var userInfo:SomeClass = makeUserInfo("John", "Doe");
}
    
private function makeUserInfo(firstName:String, lastName:String, thirdly:Boolean=false):SomeClass{
    var info:SomeClass = new SomeClass();
    return info;
}

I get the following error:

verify TestJustUserInfoInstantiation/makeUserInfo()
                        stack:
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] ~ 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  0:getlocal0
                        stack: TestJustUserInfoInstantiation
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] ~ 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  1:pushscope
                        stack:
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] TestJustUserInfoInstantiation 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  2:findpropstrict SomeClass
                        stack: global
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] TestJustUserInfoInstantiation 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  4:constructprop 3 0
                        stack: SomeClass
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] TestJustUserInfoInstantiation 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  7:coerce SomeClass
                        stack: SomeClass
                        scope: [global Object$ flash.events::EventDispatcher$ flash.display::DisplayObject$ flash.display::InteractiveObject$ flash.display::DisplayObjectContainer$ flash.display::Sprite$ TestJustUserInfoInstantiation$] TestJustUserInfoInstantiation 
                         locals: TestJustUserInfoInstantiation String? String? Boolean * 
  9:dup
VerifyError: Error #1023: Stack overflow occurred.

    at TestJustUserInfoInstantiation/onAddedToStage()

If I take out the third argument to the function, I don’t get the error.
If I set a property on info before returning it…

private function makeUserInfo(firstName:String, lastName:String, thirdly:Boolean=false):SomeClass{
    var info:SomeClass = new SomeClass();
[COLOR=#ff0000]    info.aProp = 7;[/COLOR]
    return info;
}

… I don’t get the error. I know the code as I have it here doesn’t make a lot of sense, but I’ve just stripped it down to isolate the issue.
Can anyone explain what’s going on?