librustc: Make the compiler ignore purity.

For bootstrapping purposes, this commit does not remove all uses of
the keyword "pure" -- doing so would cause the compiler to no longer
bootstrap due to some syntax extensions ("deriving" in particular).
Instead, it makes the compiler ignore "pure". Post-snapshot, we can
remove "pure" from the language.

There are quite a few (~100) borrow check errors that were essentially
all the result of mutable fields or partial borrows of `@mut`. Per
discussions with Niko I think we want to allow partial borrows of
`@mut` but detect obvious footguns. We should also improve the error
message when `@mut` is erroneously reborrowed.

1 files changed, 7 insertions, 3 deletions

diff --git a/src/libsyntax/util/interner.rs b/src/libsyntax/util/interner.rs
index 7a5708049e9..47f49ebadaa 100644
--- a/src/libsyntax/util/interner.rs
+++ b/src/libsyntax/util/interner.rs
@@ -41,14 +41,18 @@ pub impl<T:Eq + IterBytes + Hash + Const + Copy> Interner<T> {
             None => (),
         }
 
-        let new_idx = self.vect.len();
+        let vect = &*self.vect;
+        let new_idx = vect.len();
         self.map.insert(val, new_idx);
         self.vect.push(val);
         new_idx
     }
 
     fn gensym(&self, val: T) -> uint {
-        let new_idx = self.vect.len();
+        let new_idx = {
+            let vect = &*self.vect;
+            vect.len()
+        };
         // leave out of .map to avoid colliding
         self.vect.push(val);
         new_idx
@@ -59,7 +63,7 @@ pub impl<T:Eq + IterBytes + Hash + Const + Copy> Interner<T> {
     // where we first check a pred and then rely on it, ceasing to fail is ok.
     pure fn get(&self, idx: uint) -> T { self.vect[idx] }
 
-    fn len(&self) -> uint { self.vect.len() }
+    fn len(&self) -> uint { let vect = &*self.vect; vect.len() }
 }
 
 #[test]