Aladdin - Scala Bugtracking
[#294] project: compiler priority: low category: missing feature
submitter assigned to status date submitted
Burak Matthias won't fix 2004-02-06 10:38:57.0
subject typeinference in comprehensions
code 
import scala.collection.immutable.ListMap ;

object test {
        for( val y <- ListMap.Empty[int,int] ) {
          Console.println( y );
        }
}
what happened 
testMap.scala:6: missing parameter type
        for( val y <- ListMap.Empty[int,int] ) {
                 ^
testMap.scala:6: type mismatch;
 found   : () => 
 required: (scala.Int,scala.Int) => scala.Unit
        for( val y <- ListMap.Empty[int,int] ) {
                                               ^
two errors foun
what expected silent run, type inference finding out the right type of y.
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Changes of this bug report
Burak  edited on  2004-02-06 11:01:56.0
[change to 'missing feature'] Matthias just told me that this way you get the wrong foreach method, and it will be fixed once the Iterable trait is updated with the right foreach method is checked in.
Burak  edited on  2004-04-07 15:13:04.0
I see that Map.foreach expects (A,B) => Unit, which is the source of confusion. There is simply no way to make an iteration through key-value pairs using the for-comprehension syntax.

My assumption was that Map.foreach takes Pair[A,B] => Unit, and type inference was not clever enough. I change this one to "won't fix" though.