Fix building of all rustc components with -g.

[jdm]

Similarly, building non-rustc with -g should also not ICE now. The output is also kind of useful in gdb if you're careful and don't use any macros/syntax extensions in your code.

r? @TJC

[catamorphism]

Destructors implicitly return ty_nil -- can you just make that the result type for dtors and avoid the need to turn the return type into an option in the debuginfo code?

[catamorphism]

r+ if you change that -- unless there's a reason to do it this way!

[jdm]

The problem is that the return type data also contains stuff like spans which I would have to synthesize somehow.

[catamorphism]

Ah, usually the solution to the span issue is to use ast_util::dummy_spanned. Is there other info you don't know how to synthesize?

[TJC]

Hi, I get emailed about this issue all the time, because someone mentioned me (@TJC) at some point, by mistake.
Is there any way to get me off the notification list for this issue?
Thanks.

[jdm]

Whoops. Try changing the "Watching thread" pulldown under the comment box?

[TJC]

Thanks, I must have missed that when I looked the last few times >.<
ta

[catamorphism]

I noticed there's a function in ast_util that does exactly what's needed here for the dtor help. I'm going to go ahead and make the change in my tree and merge it. Thanks @jdm !

[catamorphism]

Merged in 17ea548 - thanks!