Rebasing and review changes

src/librustc/middle/cstore.rs

@@ -65,6 +65,18 @@ pub struct CrateSource {
     pub rmeta: Option<(PathBuf, PathKind)>,
 }
 
+#[derive(RustcEncodable, RustcDecodable, Copy, Clone, Ord, PartialOrd, Eq, PartialEq, Debug)]
+pub enum DepKind {
+    /// A dependency that is only used for its macros.
+    MacrosOnly,
+    /// A dependency that is always injected into the dependency list and so
+    /// doesn't need to be linked to an rlib, e.g. the injected allocator.
+    Implicit,
+    /// A dependency that is required by an rlib version of this crate.
+    /// Ordinary `extern crate`s result in `Explicit` dependencies.
+    Explicit,
+}
+
 #[derive(PartialEq, Clone, Debug)]
 pub enum LibSource {
     Some(PathBuf),