Check generic signatures

[jodastephen]

Ensure that the generics used are correct. This is specifically focussed on extends/super.

For example, the Chrono static comparators should perhaps use extends.

[jodastephen]

I've examined the generics on the temporal classes twice now. It isn't possible to enhance their generics without making a terrible mess. Because Java doesn't have the Self-type generic, or the notional of parameter self-type generic where the class is final, and because LocalDate extends ChronoLocalDate, it is more or less impossible to go further than we have. This is unfortunate, but there you go.

The call remains open to check ? extends and ? super.

[jodastephen]

TemporalUnit <R extends Temporal> long between(R dateTime1, R dateTime2); has no effect on callers. It doesn't do what I'd like it to do. Needs to be ungenerified.

[RogerRiggs]

It should insist that the parameters are of the same/compatible types.
What is it not doing?

[jodastephen]

This compiles, rather than being a compile error:

 Instant i = ...
 ZonedDateTime z = ...
 between(i, z)

[RichardWarburton]

It only insists that they have a common supertype that subclasses temporal
I think.

[RogerRiggs]

It makes sense to remove the generics, they are more useful in the case where the return type is related to the parameters.

[RogerRiggs]

The generics should be removed from Chronology.getAvailableChronologies(). The raw types are just as useful.

[jodastephen]

I don't think we should have raw types in API signatures. I would have thought there was a JDK/Oracle policy against it.

[ijuma]

It would be very odd for a brand new API to have raw types in API signatures in my opinion.

[RichardWarburton]

Quite a few people compile with warnings switched on for raw types, this
would generate a lot of warnings for me. Perhaps a simple ? wildcard would
be a better solution if you're leaving generics in.

[jodastephen]

Remove some pointless generics - http://hg.openjdk.java.net/threeten/threeten/jdk/rev/e5a10d4e6149

[jodastephen]

Chronology returns raw types for ChronoLocalDate which needs fixing.

[RogerRiggs]

Raw types fixed with http://hg.openjdk.java.net/threeten/threeten/jdk/rev/bf46149114e4

[RogerRiggs]

Nothing more to do on this.