complete default methods for traits

[lkuper]

Implement the first two parts of this proposal (the third part, dealing with instance coherence, is orthogonal).

[lkuper]

fc9c4c3 is the beginning of support for default methods in traits.

[lkuper]

Default methods get through typeck as of 293f371.

[lkuper]

Per IRC discussions, it seems that a big part of the remaining work (possibly the big part) is monomorphization. This is now @msullivan's bug, since I'm back at school and, alas, unlikely to work on it any time soon, and he's better equipped to deal with it than I am. :)

[catamorphism]

One specific thing that's not finished is that default methods don't work cross-crate.

[burg]

Default methods are important for Servo (layout, display list). I will deliver a Free Beverage to whomever fixes this (two beverages if documentation written!).

[nikomatsakis]

It would be very useful to have a "compiler_context" trait or some such that looks kind of like:

trait compiler_context {
    fn tcx() -> ty::ctxt;

    fn ty_to_str(t: ty::t) -> ~str { ty_to_str(self.tcx(), t) }
    fn expr_to_str(expr: @ast::expr) -> ~str { fmt!("expr(%?: %s)", expr.id, expr_to_str(expr, self.tcx().sess.intr()) }
    ...
}

[nikomatsakis]

This is basically blocked and/or possibly a subpart of #3446

[nikomatsakis]

Deferring to 0.5

[catamorphism]

I think this is done; file more specific bugs if necessary.

[lkuper]

Huzzah!

[catamorphism]

@lkuper I spoke a bit too soon, but still, there will be separate more specific bugs for any remaining issues :-)

[graydon]

Re-opening and promoting to metabug. Sub-bugs include: #4099 #4396 #4102 #4103 #4377 #4350 #3694

No idea how much work there is to do here, but it needs to work. We've been stumbling over the absence of this feature in library work all year, keep deferring fixing due to "higher priority" work.

[msullivan]

About to file pull request that fixes #4099, #4350.

[catamorphism]

@msullivan - where does this stand for 0.7?

[brson]

Bumping from 0.7

[msullivan]

@catamorphism - They are a lot more solid than they used to be, and could /maybe/ be taken out from behind the flag. Still a bunch of known problems, though.

[msullivan]

This is basically done and working. Couple minor problems, but they are solidly usable.

[lkuper]

Serious round of applause for @msullivan and everyone else who's been working on this over the last year.