| [#612] | project: specification | priority: low | category: missing feature | |
|---|---|---|---|---|
| submitter | assigned to | status | date submitted | |
| Sean | Martin | open | 2006-05-19 17:09:23.0 | |
| subject | requires only applies to this??? | |||
| code |
package test2;
abstract class Test {
type A <: Ax;
def foo(a : A) : Unit;
def ax : Ax;
abstract class Ax requires A {
foo(this);
}
foo(ax);
} |
|||
| what happened | The first call to foo (foo(this)) passes type checking, the second call to foo (foo(ax)) does not: type mismatch; found : Test.this.Ax required: Test.this.A test/src/test2 Test.scala |
|||
| what expected | I would exect that if Ax.this is a subtype of A, then any value of type Ax is also a subtype of A. | |||
| [back to overview] | ||||
| Martin edited on 2006-05-27 11:16:09.0 |
| `requires' currently does not affect subtyping, nor member access from outside an object. It is an open question whether it should. Compare also with bug 511. |
| Burak edited on 2006-05-28 22:29:15.0 |
| As I argued under Expressivity for free! `requires' is then more obviously a way of splitting a class into different parts, which is nice for modularity. |
| Burak edited on 2006-05-28 22:31:02.0 |
|
sorry, trying again: As I argued under [bug #511]every Ax is an A, so it would make sense to treat it Ax as a subtype of A. The spec does not say too much on 'requires', but I think we all agree that all instances of Ax are also instances of A, due to the `require'. By "extension, this is just another way of saying that they are in the subtyping relation.
> Expressivity for free! `requires' is then more obviously a way of splitting a class into different parts, which is nice for modularity. |
| Martin edited on 2006-08-20 18:42:22.0 |
| The spec says otherwise. It's open to review, though. |