| [#71] | project: compiler | priority: medium | category: bug | |
|---|---|---|---|---|
| submitter | assigned to | status | date submitted | |
| Burak | Martin | fixed | 2003-07-15 16:39:15.0 | |
| subject | implementing abstract Java methods | |||
| code |
// file 1 "gu/ga.scala" (it needs to under a package...)
package gu;
public abstract class ga1 {
/*public*/ abstract String foo(); // if you uncomment public, it works
public void mymain() {
System.out.println( foo() );
}
public ga1() {}
}
// ga2
object ga2 extends gu.ga1() {
// implementation of foo()
def foo():java.lang.String = "foo";
// my main inherited
def main( args:Array[String] ):Unit = {
mymain ();
}
} |
|||
| what happened | >javac gu/ga1.java >socos ga2.scala >java ga2 Exception in thread "main" java.lang.AbstractMethodError: gu.ga1.foo()Ljava/lang/String; at gu.ga1.mymain(ga1.java:8) at ga2$.main(ga2.scala) at ga2.main(ga2.scala) |
|||
| what expected | "foo" being printed. | |||
| [back to overview] | ||||
| Matthias edited on 2003-07-15 22:27:38.0 |
|
The expected behavior is a compile-time error! Method foo in gu.ga1 is protected; consequently, it will not be inherited to classes outside of the package gu. Therefore it is impossible to implement this abstract method in a subclass outside of the package gu. This is not Scala-specific; even in Java it will never be possible to implement foo in a class of the empty (top-level) package. In Scala, protected is regarded as private since Scala does not have a notion of a package-private access. That's why the compiler has to emit an error message: "ga2 should be declared abstract, it does not implement foo...". |
| Martin edited on 2003-07-16 14:17:04.0 |
| The problem was that the class reader did not enter private members into the scope of their parents. I fixed that now. |
| Martin edited on 2003-07-16 15:23:24.0 |