auto merge of #17197 : nikomatsakis/rust/issue-5527-trait-reform-revisited, r=pcwalton

This patch does not make many functional changes, but does a lot of restructuring towards the goals of #5527. This is the biggest patch, basically, that should enable most of the other patches in a relatively straightforward way.

Major changes:

- Do not track impls through trans, instead recompute as needed.
- Isolate trait matching code into its own module, carefully structure to distinguish various phases (selection vs confirmation vs fulfillment)
- Consider where clauses in their more general form
- Integrate checking of builtin bounds into the  trait matching process, rather than doing it separately in kind.rs (important for opt-in builtin bounds)

What is not included:

- Where clauses are still not generalized. This should be a straightforward follow-up patch.
- Caching. I did not include much caching. I have plans for various kinds of caching we can do. Should be straightforward. Preliminary perf measurements suggested that this branch keeps compilation times roughly what they are.
- Method resolution. The initial algorithm I proposed for #5527 does not work as well as I hoped. I have a revised plan which is much more similar to what we do today.
- Deref vs deref-mut. The initial fix I had worked great for autoderef, but not for explicit deref. 
- Permitting blanket impls to overlap with specific impls. Initial plan to consider all nested obligations before considering an impl to match caused many compilation errors. We have a revised plan but it is not implemented here, should be a relatively straightforward extension.

2 files changed, 11 insertions, 11 deletions

diff --git a/src/libsync/comm/mod.rs b/src/libsync/comm/mod.rs
index c8b86c47c90..9177fa4a6b4 100644
--- a/src/libsync/comm/mod.rs
+++ b/src/libsync/comm/mod.rs
@@ -379,7 +379,7 @@ pub struct Receiver<T> {
     inner: UnsafeCell<Flavor<T>>,
     receives: Cell<uint>,
     // can't share in an arc
-    marker: marker::NoSync,
+    _marker: marker::NoSync,
 }
 
 /// An iterator over messages on a receiver, this iterator will block
@@ -397,7 +397,7 @@ pub struct Sender<T> {
     inner: UnsafeCell<Flavor<T>>,
     sends: Cell<uint>,
     // can't share in an arc
-    marker: marker::NoSync,
+    _marker: marker::NoSync,
 }
 
 /// The sending-half of Rust's synchronous channel type. This half can only be
@@ -406,7 +406,7 @@ pub struct Sender<T> {
 pub struct SyncSender<T> {
     inner: Arc<UnsafeCell<sync::Packet<T>>>,
     // can't share in an arc
-    marker: marker::NoSync,
+    _marker: marker::NoSync,
 }
 
 /// This enumeration is the list of the possible reasons that try_recv could not
@@ -543,7 +543,7 @@ impl<T: Send> Sender<T> {
         Sender {
             inner: UnsafeCell::new(inner),
             sends: Cell::new(0),
-            marker: marker::NoSync,
+            _marker: marker::NoSync,
         }
     }
 
@@ -719,7 +719,7 @@ impl<T: Send> Drop for Sender<T> {
 
 impl<T: Send> SyncSender<T> {
     fn new(inner: Arc<UnsafeCell<sync::Packet<T>>>) -> SyncSender<T> {
-        SyncSender { inner: inner, marker: marker::NoSync }
+        SyncSender { inner: inner, _marker: marker::NoSync }
     }
 
     /// Sends a value on this synchronous channel.
@@ -807,7 +807,7 @@ impl<T: Send> Drop for SyncSender<T> {
 
 impl<T: Send> Receiver<T> {
     fn new(inner: Flavor<T>) -> Receiver<T> {
-        Receiver { inner: UnsafeCell::new(inner), receives: Cell::new(0), marker: marker::NoSync }
+        Receiver { inner: UnsafeCell::new(inner), receives: Cell::new(0), _marker: marker::NoSync }
     }
 
     /// Blocks waiting for a value on this receiver
diff --git a/src/libsync/deque.rs b/src/libsync/deque.rs
index e70a730dc3a..521a7d0bd73 100644
--- a/src/libsync/deque.rs
+++ b/src/libsync/deque.rs
@@ -87,7 +87,7 @@ struct Deque<T> {
 /// There may only be one worker per deque.
 pub struct Worker<T> {
     deque: Arc<Deque<T>>,
-    noshare: marker::NoSync,
+    _noshare: marker::NoSync,
 }
 
 /// The stealing half of the work-stealing deque. Stealers have access to the
@@ -95,7 +95,7 @@ pub struct Worker<T> {
 /// `steal` method.
 pub struct Stealer<T> {
     deque: Arc<Deque<T>>,
-    noshare: marker::NoSync,
+    _noshare: marker::NoSync,
 }
 
 /// When stealing some data, this is an enumeration of the possible outcomes.
@@ -153,8 +153,8 @@ impl<T: Send> BufferPool<T> {
     pub fn deque(&self) -> (Worker<T>, Stealer<T>) {
         let a = Arc::new(Deque::new(self.clone()));
         let b = a.clone();
-        (Worker { deque: a, noshare: marker::NoSync },
-         Stealer { deque: b, noshare: marker::NoSync })
+        (Worker { deque: a, _noshare: marker::NoSync },
+         Stealer { deque: b, _noshare: marker::NoSync })
     }
 
     fn alloc(&mut self, bits: uint) -> Box<Buffer<T>> {
@@ -217,7 +217,7 @@ impl<T: Send> Stealer<T> {
 
 impl<T: Send> Clone for Stealer<T> {
     fn clone(&self) -> Stealer<T> {
-        Stealer { deque: self.deque.clone(), noshare: marker::NoSync }
+        Stealer { deque: self.deque.clone(), _noshare: marker::NoSync }
     }
 }