| [#930] | project: compiler | priority: low | category: feature | |
|---|---|---|---|---|
| submitter | assigned to | status | date submitted | |
| Sean | Martin | fixed | 2007-02-01 10:24:43.0 | |
| subject | run-time type of null not matching? | |||
| code |
package test;
object Test {
def main(args : Array[String]) : Unit = {
val x : Null = null;
Console.println(x match {
case that : Null if that eq null => true;
case _ => false;
});
}
}
|
|||
| what happened | Program runs, prints "false" |
|||
| what expected | Should print true. | |||
| [back to overview] | ||||
| Burak edited on 2007-02-01 16:01:47.0 |
|
for the record, behavior is according to spec.
Martin says the pattern is redundant, and asks me to detect this, but in fact it is not: it has a guard. So I mark this as "feature". |
| Burak edited on 2007-02-01 16:02:15.0 |
| Martin edited on 2007-02-01 17:10:14.0 |
| I claim it is redundant: x: Null is never true. Adding a guard does not change this. |
| Burak edited on 2007-02-01 17:24:31.0 |
| would it not be better to flag it as an ill-typed pattern, outlawing it all together? The "redundancy" you mention depends on the type of the pattern. There is no precedence for doing anything to patterns that are of some special type (whereas for all types, if static type coincides with type to be tested, then the type test is omitted and we just emit a null check). |
| Martin edited on 2007-02-03 10:52:21.0 |
| Martin edited on 2007-03-05 23:56:04.0 |
Program is now rejected statically with:
bug930.scala:7: error: this type cannot be used in a type pattern
case that : Null if that eq null => true;
^
|