syntax: modernise attribute handling in syntax::attr.

This does a number of things, but especially dramatically reduce the
number of allocations performed for operations involving attributes/
meta items:

- Converts ast::meta_item & ast::attribute and other associated enums
  to CamelCase.
- Converts several standalone functions in syntax::attr into methods,
  defined on two traits AttrMetaMethods & AttributeMethods. The former
  is common to both MetaItem and Attribute since the latter is a thin
  wrapper around the former.
- Deletes functions that are unnecessary due to iterators.
- Converts other standalone functions to use iterators and the generic
  AttrMetaMethods rather than allocating a lot of new vectors (e.g. the
  old code would have to allocate a new vector to use functions that
  operated on &[meta_item] on &[attribute].)
- Moves the core algorithm of the #[cfg] matching to syntax::attr,
  similar to find_inline_attr and find_linkage_metas.

This doesn't have much of an effect on the speed of #[cfg] stripping,
despite hugely reducing the number of allocations performed; presumably
most of the time is spent in the ast folder rather than doing attribute
checks.

Also fixes the Eq instance of MetaItem_ to correctly ignore spaces, so
that `rustc --cfg 'foo(bar)'` now works.

1 files changed, 3 insertions, 3 deletions

diff --git a/src/libsyntax/parse/comments.rs b/src/libsyntax/parse/comments.rs
index 83af5bade3a..6daeb1b3e1e 100644
--- a/src/libsyntax/parse/comments.rs
+++ b/src/libsyntax/parse/comments.rs
@@ -44,12 +44,12 @@ pub fn is_doc_comment(s: &str) -> bool {
     s.starts_with("/*!")
 }
 
-pub fn doc_comment_style(comment: &str) -> ast::attr_style {
+pub fn doc_comment_style(comment: &str) -> ast::AttrStyle {
     assert!(is_doc_comment(comment));
     if comment.starts_with("//!") || comment.starts_with("/*!") {
-        ast::attr_inner
+        ast::AttrInner
     } else {
-        ast::attr_outer
+        ast::AttrOuter
     }
 }