make int implement Comparable<int>?

[sigmundch]

I'm not sure what's the right fix for this. I want to use:

SplayTreeMap<int, X>

but I get an error in checked mode that 'int' is not a 'Comparable<int>' (currently SplayTreeMap expects 'K extends Comparable<K>')

I can work around this easily by using 'num' as the type of my keys, but I think there is something here that should be fixed. Either we want to make
'int' implements 'Compatable<int>', or relax the type constraint in SplayTreeMap, for instance to expect a K extends Comparable, but not necessarily Comparable<K>?

[jmesserly]

This seems like a bug in subtype tests? A class that implements Comparable<num> should be Comparable<int>.

Uh, even stranger, Comparable seems to be non-generic:
https://code.google.com/p/dart/source/browse/branches/bleeding_edge/dart/lib/core/comparable.dart?r=13806

[sigmundch]

true, maybe it's a bug in subtype tests?

Note: seems like you had a link to a very old revision, it was added this past week:

https://code.google.com/p/dart/source/browse/branches/bleeding_edge/dart/sdk/lib/core/comparable.dart

CC'ng Gilad to get his opinion.

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cc @gbracha.

[jmesserly]

I was confusing assignment compatibility with subtype tests.
It is strange that int does not implement Comparable<int>, however.

[lrhn]

It is a problem.
We can "solve" this by doing
 class int extends num implements Comparable<int>, Comparable<num>
but it will still break for other publicly visible classes that are comparable to a superclass of themselves.

[lrhn]

The problem is "solved" by changing the typing requirement on SplayTreeMap.
It now accepts any class, and takes a comparator as argument. If the comparator is omitted, it defaults to Comparable.compare, which means that the type must implement compareTo.

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Added Fixed label.