Aladdin - Scala Bugtracking
[#587] project: compiler priority: medium category: bug
submitter assigned to status date submitted
Stephane Martin noise 2006-05-05 18:00:41.0
subject Type mismatch error
code 
object test {

  case class Foo(name: String)
  case class Bar(xs: List[Foo])

  val xs = List(Bar(List(Foo("a"), Foo("b"))))
  //for (val Bar(hd :: tl) <- xs) yield Bar(hd :: tl) // OK
  for (val Bar(hd @ Foo(name) :: tl) <- xs) yield Bar(hd :: tl)
}
what happened 
test.scala:8 error: type mismatch;
 found   : scala.::[test.this.Foo]
 required: test.this.Foo
  for (val Bar(hd @ Foo(name) :: tl) <- xs) yield Bar(hd :: tl)
                                                         ^
one error found
what expected compiles with no error
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Changes of this bug report
Martin  edited on  2006-05-05 19:35:58.0
You need to write (hd @ Foo(name)), otherwise hd will scope over the whole pattern that follows. I have not tried this out, though, so you should still verify that it's OK.