[GROOVY-4546] Several bugs with @Category

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.7.5, 1.8-beta-2
• Fix Version/s: 1.7.6, 1.8-beta-3
• Assignee: Paul King
• Reporter: Paul King
• Created: 30/Nov/10 23:02
• Updated: 07/Apr/15 19:06
• Resolved: 01/Dec/10 05:52

Description

In the following code:

@Category(Integer)
class MyOps {
  def multiplesUpTo4() { [this * 2, this * 3, this * 4] }
  def multiplesUpTo(num) {
    (2..num).collect{ i -> this * i }
  }
  def alsoMultiplesUpTo(num) {
    def ans = (2..num).collect{ i -> this * i }
    ans
  }
//  def twice() { 
//    def (twice, thrice, quad) = multiplesUpTo4()
//    twice
//  }
}

use(MyOps) {
  println 21.multiplesUpTo4()       // => [42, 63, 84]
  println 21.multiplesUpTo(6)       // => [42, 63, 84, 105, 126]
//  println 21.alsoMultiplesUpTo(6) // (A)
//  println 21.twice()              // (B)
}

If the line marked (A) is uncommented, then it fails at runtime with

groovy.lang.MissingPropertyException: No such property: i for class: java.lang.Integer

Looking at the transformed code for alsoMultiplesUpTo as per the AST browser, it is easy to see why we get that error:

java.lang.Object ans = (2.. num).collect({ java.lang.Object i -> $this * $this.i })

Meanwhile the code for the nearly identical earlier method multiplesUpTo is as expected:

(2.. num).collect({ java.lang.Object i -> $this * i })

If the "twice" method is uncommented, then we get a ClassCastException at compile time.
Also, if you create the category long hand (i.e. not using the AST transform) both problems go away.