Scala REPL tab-complete is lying to me?

Question

With Scala 2.8.1, SBT 0.7.4, WebDriver HTMLUnit 2.6. In the SBT console REPL ...

 scala> e.findElement[tab]

findElement                     findElementById                 findElementByLinkText           findElementByPartialLinkText
findElementByTagName            findElementByXPath              findElements                    findElementsById
findElementsByLinkText          findElementsByPartialLinkText   findElementsByTagName           findElementsByXPath

scala> e.findElementByXPath[tab]

def findElementByXPath(String): org.openqa.selenium.WebElement

scala> e.findElementByXPath("/td[0]")
<console>:12: error: value findElementByXPath is not a member of org.openqa.selenium.WebElement
       e.findElementByXPath("/td[0]")
         ^

( [tab] s are added by me for the purpose of illustrating tab completion)

So, the REPL tells me that findElementByXPath(String):WebElement exists on e , but when I invoke it, it's not found. What gives?

Answer 1

Note that org.openqa.selenium.WebElement doesn't have these methods, but classes implementing it like org.openqa.selenium.htmlunit.HtmlUnitWebElement do.

My best guess is that tab-completion shows all public (or protected; see Daniel's answer) methods of e 's class , but the type of the variable is org.openqa.selenium.WebElement , so these methods can't actually be called.

Answer 2

See here:

scala> class X {
     |   def m1 = 1
     |   protected def m2 = 2
     |   private def m3 = 3
     | }
defined class X

scala> class Y extends X {
     |   def m4 = 4
     | }
defined class Y

scala> val x: X = new Y
x: X = Y@12524b0

scala> x.

asInstanceOf   equals         getClass       hashCode       isInstanceOf   m1             m2             m4
notify         notifyAll      toString       wait

So, m2 shows up even though you can't use it because it is protected, and m4 shows up even though you can't use it (without casting or matching) because x 's type is X , and m4 is of class Y (the actual class , not type , of x ).

Next question: is this intentional? Well, not really, but there are things of higher priority to fix. Patches are welcome, of course. :-)