[ nice-Bugs-1672222 ] Abstract interfaces and covariant return types

Bugs item #1672222, was opened at 2007-03-02 06:45
Message generated for change (Comment added) made by drmaciver
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Category: None
Group: None
Status: Open
Resolution: None
Priority: 5
Private: No
Submitted By: David R. MacIver (drmaciver)
Assigned to: Nobody/Anonymous (nobody)
Summary: Abstract interfaces and covariant return types

Initial Comment:
Code:

package test;
import nice.functional;

class Test implements Foo 
{
    Test[] children;
}

more(Test t) = generator(t.children);

abstract interface Foo 
{
}

<Foo T> () -> T more(T t); 

Compiler error:

Incorrect return type:
Found   : ()->test.Test
Expected: ()->T

This appears not to always fail. For example if I replace the implementation with 

more(Test t) = () => t;

The code compiles fine.

I've not been able to narrow down exactly what circumstances it fails in.

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>Comment By: David R. MacIver (drmaciver)
Date: 2007-03-02 06:56

Message:
Logged In: YES 
user_id=1681313
Originator: YES

As pointed out by arjanb in #nice, if you replace 'implements Foo' with
'finally implements Foo', this starts working. I still think it's a bug
though. :-)

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