auto merge of #6798 : alexcrichton/rust/doc-lints, r=pcwalton

These commits perform a variety of actions:

1. The linting of missing documentation has been consolidated under one `missing_doc` attribute, and many more things are linted about.
2. A test was added for linting missing documentation, which revealed a large number of corner cases in both linting and the `missing_doc` lint pass. Some notable edge cases:
  * When compiling with `--test`, all `missing_doc` warnings are suppressed
  * If any parent of the current item has `#[doc(hidden)]`, then the `missing_doc` warning is suppressed
3. Both the std and extra libraries were modified to `#[deny(missing_doc)]` by default.

I believe that the libraries are getting to the point where they're fairly well documented, and they should definitely stay that way. If developing a particular new module, it's easy enough to add `#[allow(missing_doc)]` at the top, but those should definitely be flags for removal in favor of actual documentation.

I added as much documentation as I could throughout std/extra, although I avoided trying to document things that I knew nothing about. I can't say that this lint pass will vouch for the quality of the documentation of std/extra, but it will certainly make sure that there's at least some describing words.

That being said, I may have a different opinion, so I don't mind amending these commits to turn off the lint by default for std/extra if people think otherwise.

1 files changed, 2 insertions, 0 deletions

diff --git a/src/libstd/cell.rs b/src/libstd/cell.rs
index b80d3ae68f8..f6d4e966db9 100644
--- a/src/libstd/cell.rs
+++ b/src/libstd/cell.rs
@@ -23,6 +23,7 @@ Similar to a mutable option type, but friendlier.
 
 #[mutable]
 #[deriving(Clone, DeepClone, Eq)]
+#[allow(missing_doc)]
 pub struct Cell<T> {
     priv value: Option<T>
 }
@@ -32,6 +33,7 @@ pub fn Cell<T>(value: T) -> Cell<T> {
     Cell { value: Some(value) }
 }
 
+/// Creates a new empty cell with no value inside.
 pub fn empty_cell<T>() -> Cell<T> {
     Cell { value: None }
 }