with getter in superclass and setter in sublcass, warning: "Setter type 'T' must be assignable to getter type 'T'"

[DartBot]

This issue was originally filed by [email protected]

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STEPS TO REPRODUCE
Code like this exhibits the problem:

interface Foo<T> {
// ...
T get val();
void set val(T value);
}

class Base<T> {
// ...
T get val() {
_validate();
return _value;
}
T _value;
bool _valid;
}

class Sub<T> extends Base<T> implements Foo<T> {
void set val(T value) {
_invalidate();
_value = value;
_valid = true;
}
// T get val() => super.val
}

EXPECTED OUTPUT? OBSERVED OUTPUT?
No warning is expected, but warning appears

PRODUCT VERSION? OPERATING SYSTEM?
Dart Editor build 7552 on OS X Lion.

ADDITIONAL INFORMATION.
Adding a getter in the subclass removes the warning (see the commented-out line in Sub<T> above).
Quoting Gilad: "Looks like a bug related to typechecking generics to me. "

[sethladd]

I believe this is a VM issue, as the reporter is using the editor.

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Added Area-VM, Triaged labels.

[iposva-google]

Removed Area-VM label.
Added Area-Editor label.

[danrubel]

Set owner to @scheglov.

[scheglov]

https://chromiumcodereview.appspot.com/10383251

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Added Started label.

[scheglov]

https://code.google.com/p/dart/source/detail?r=7763

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Added Fixed label.