Aladdin - Scala Bugtracking
[#451] project: compiler priority: medium category: bug
submitter assigned to status date submitted
Iulian Burak noise 2005-07-13 15:40:11.0
subject Parser does not accept "this" as value inside patterns
code 
class A {
  def matchme(t: Tree) = {
    val b = this;
    t match {
      case DefDef(b) => Console.println("Ok!");
//      case DocDef(this) => Console.println("Ok!");
      case _ => Console.println("not ok");
    }
  }
}

trait Tree;

case class DefDef(a: A) extends Tree;
case class DocDef(b: A) extends Tree;
what happened 
If I uncomment the second pattern, I get this:

this-match.scala:7: '.' expected but ')' found.
      case DocDef(this) => Console.println("Ok!");
                      ^
what expected No compiler error. The first pattern shows that it works fine with normal values, why should this be treated differently?
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Changes of this bug report
Iulian  edited on  2005-07-13 15:40:42.0
Added 
 tags
Iulian  edited on  2005-07-13 15:51:46.0
No bug, my example doesn't work. As Michel explained, the "b" inside the pattern is a new variable which shadows the previous definition. "b" gets the value of whatever is inside DefDef, even if that's not equal to `this'.
Burak  edited on  2005-07-13 16:57:45.0
In the pattern, try to write "A.this" instead of "this"!