In this commit I added a useful utility type, named Void, that encapsulates the
doable but annoying job of creating an uninhabited type. As well, a function on
that type, named absurd, was created which is useful for ignoring the result of
matching on that type. No unit tests were created because it is not possible to
create an instance of this type to test the usage of.
This type is useful because it is like NonCopyable in that it can be used to
create a type with special characteristics without special bloat. For instance,
instead of typing pub struct PhantomType { priv contents : () } for each void
type one may want to use one can simply type pub struct PhantomType (Void);.
This type make such special cases much easier to write.
At the moment this only includes type checking and there is no code generation support yet. I wanted to get the design reviewed first.
From discussion with @graydon at #5841, re-implemented as `#[simd]` attribute on structs.
Progressing towards #3499.
r? @ILyoan
This pulls all the logic for discovering the crate entry point into a new pass (out of resolve and typeck), then changes it so that main is only looked for at the crate level (`#[main]` can still be used anywhere).
I don't understand the special android logic here and worry that I may have broken it.
This "finishes" the generic deriving code (which I started in #5640), in the sense it supports everything that I can think of being useful. (Including lifetimes and type parameters on methods and traits, arguments and return values of (almost) any type, static methods.)
It closes#6149, but met with #6257, so the following doesn't work:
```rust
#[deriving(TotalEq)]
struct Foo<'self>(&'self int);
```
(It only fails for `TotalOrd`, `TotalEq` and `Clone`, since they are the only ones that call a method directly on sub-elements of the type, which means that the auto-deref interferes with the pointer.)
It also makes `Rand` (chooses a random variant, fills the fields with random values, including recursively for recursive types) and `ToStr` (`x.to_str()` is the same as `fmt!("%?", x)`) derivable, as well as converting IterBytes to the generic code (which made the code 2.5x shorter, more robust and added support for tuple structs).
({En,De}codable are trickier, so I'll convert them over later.)
