diff --git a/src/libcore/comm.rs b/src/libcore/comm.rs
index 177ecdca9a2d..5dfafb85bbd9 100644
--- a/src/libcore/comm.rs
+++ b/src/libcore/comm.rs
@@ -420,17 +420,17 @@ fn test_select2_stress() {
         };
     }
 
-    let mut as = 0;
+    let mut as_ = 0;
     let mut bs = 0;
     for iter::repeat(msgs * times * 2u) {
         match select2(po_a, po_b) {
-          either::Left(~"a") => as += 1,
+          either::Left(~"a") => as_ += 1,
           either::Right(~"b") => bs += 1,
           _ => fail ~"test_select_2_stress failed"
         }
     }
 
-    assert as == 400;
+    assert as_ == 400;
     assert bs == 400;
 }
 
diff --git a/src/libcore/vec.rs b/src/libcore/vec.rs
index 2ae6a7b2780c..746544a6afda 100644
--- a/src/libcore/vec.rs
+++ b/src/libcore/vec.rs
@@ -1029,15 +1029,15 @@ pure fn rposition_between<T>(v: &[T], start: uint, end: uint,
  * Convert a vector of pairs into a pair of vectors, by reference. As unzip().
  */
 pure fn unzip_slice<T: Copy, U: Copy>(v: &[(T, U)]) -> (~[T], ~[U]) {
-    let mut as = ~[], bs = ~[];
+    let mut as_ = ~[], bs = ~[];
     for each(v) |p| {
         let (a, b) = p;
         unchecked {
-            vec::push(as, a);
+            vec::push(as_, a);
             vec::push(bs, b);
         }
     }
-    return (as, bs);
+    return (as_, bs);
 }
 
 /**
diff --git a/src/rustc/middle/trans/type_use.rs b/src/rustc/middle/trans/type_use.rs
index 4c6b936172f5..09b53d2fccfa 100644
--- a/src/rustc/middle/trans/type_use.rs
+++ b/src/rustc/middle/trans/type_use.rs
@@ -116,17 +116,17 @@ fn type_uses_for(ccx: @crate_ctxt, fn_id: def_id, n_tps: uint)
     uses
 }
 
-fn type_needs(cx: ctx, use: uint, ty: ty::t) {
+fn type_needs(cx: ctx, use_: uint, ty: ty::t) {
     // Optimization -- don't descend type if all params already have this use
     for vec::each_mut(cx.uses) |u| {
-        if *u & use != use {
-            type_needs_inner(cx, use, ty, @Nil);
+        if *u & use_ != use_ {
+            type_needs_inner(cx, use_, ty, @Nil);
             return;
         }
     }
 }
 
-fn type_needs_inner(cx: ctx, use: uint, ty: ty::t,
+fn type_needs_inner(cx: ctx, use_: uint, ty: ty::t,
                     enums_seen: @List<def_id>) {
     do ty::maybe_walk_ty(ty) |ty| {
         if ty::type_has_params(ty) {
@@ -145,14 +145,14 @@ fn type_needs_inner(cx: ctx, use: uint, ty: ty::t,
                     for vec::each(*ty::enum_variants(cx.ccx.tcx, did)) |v| {
                         for vec::each(v.args) |aty| {
                             let t = ty::subst(cx.ccx.tcx, &substs, aty);
-                            type_needs_inner(cx, use, t, seen);
+                            type_needs_inner(cx, use_, t, seen);
                         }
                     }
                 }
                 false
               }
               ty::ty_param(p) => {
-                cx.uses[p.idx] |= use;
+                cx.uses[p.idx] |= use_;
                 false
               }
               _ => true
@@ -161,8 +161,8 @@ fn type_needs_inner(cx: ctx, use: uint, ty: ty::t,
     }
 }
 
-fn node_type_needs(cx: ctx, use: uint, id: node_id) {
-    type_needs(cx, use, ty::node_id_to_type(cx.ccx.tcx, id));
+fn node_type_needs(cx: ctx, use_: uint, id: node_id) {
+    type_needs(cx, use_, ty::node_id_to_type(cx.ccx.tcx, id));
 }
 
 fn mark_for_expr(cx: ctx, e: @expr) {
diff --git a/src/rustc/middle/typeck/infer/combine.rs b/src/rustc/middle/typeck/infer/combine.rs
index 2bfabd807a25..7cc9f26b1fdb 100644
--- a/src/rustc/middle/typeck/infer/combine.rs
+++ b/src/rustc/middle/typeck/infer/combine.rs
@@ -59,9 +59,9 @@ trait combine {
     fn mts(a: ty::mt, b: ty::mt) -> cres<ty::mt>;
     fn contratys(a: ty::t, b: ty::t) -> cres<ty::t>;
     fn tys(a: ty::t, b: ty::t) -> cres<ty::t>;
-    fn tps(as: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]>;
+    fn tps(as_: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]>;
     fn self_tys(a: Option<ty::t>, b: Option<ty::t>) -> cres<Option<ty::t>>;
-    fn substs(did: ast::def_id, as: &ty::substs,
+    fn substs(did: ast::def_id, as_: &ty::substs,
               bs: &ty::substs) -> cres<ty::substs>;
     fn fns(a: &ty::FnTy, b: &ty::FnTy) -> cres<ty::FnTy>;
     fn fn_sigs(a: &ty::FnSig, b: &ty::FnSig) -> cres<ty::FnSig>;
@@ -212,20 +212,20 @@ fn super_substs<C:combine>(
 }
 
 fn super_tps<C:combine>(
-    self: &C, as: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
+    self: &C, as_: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
 
     // Note: type parameters are always treated as *invariant*
     // (otherwise the type system would be unsound).  In the
     // future we could allow type parameters to declare a
     // variance.
 
-    if vec::same_length(as, bs) {
-        iter_vec2(as, bs, |a, b| {
+    if vec::same_length(as_, bs) {
+        iter_vec2(as_, bs, |a, b| {
             eq_tys(self, a, b)
-        }).then(|| Ok(as.to_vec()) )
+        }).then(|| Ok(as_.to_vec()) )
     } else {
         Err(ty::terr_ty_param_size(
-            expected_found(self, as.len(), bs.len())))
+            expected_found(self, as_.len(), bs.len())))
     }
 }
 
@@ -383,9 +383,9 @@ fn super_tys<C:combine>(
       (ty::ty_int(_), _) |
       (ty::ty_uint(_), _) |
       (ty::ty_float(_), _) => {
-        let as = ty::get(a).struct;
+        let as_ = ty::get(a).struct;
         let bs = ty::get(b).struct;
-        if as == bs {
+        if as_ == bs {
             Ok(a)
         } else {
             Err(ty::terr_sorts(expected_found(self, a, b)))
@@ -471,23 +471,23 @@ fn super_tys<C:combine>(
         }
       }
 
-      (ty::ty_rec(as), ty::ty_rec(bs)) => {
-        if vec::same_length(as, bs) {
-            map_vec2(as, bs, |a,b| {
+      (ty::ty_rec(as_), ty::ty_rec(bs)) => {
+        if vec::same_length(as_, bs) {
+            map_vec2(as_, bs, |a,b| {
                 self.flds(a, b)
             }).chain(|flds| Ok(ty::mk_rec(tcx, flds)) )
         } else {
-            Err(ty::terr_record_size(expected_found(self, as.len(),
+            Err(ty::terr_record_size(expected_found(self, as_.len(),
                                                     bs.len())))
         }
       }
 
-      (ty::ty_tup(as), ty::ty_tup(bs)) => {
-        if vec::same_length(as, bs) {
-            map_vec2(as, bs, |a, b| self.tys(a, b) )
+      (ty::ty_tup(as_), ty::ty_tup(bs)) => {
+        if vec::same_length(as_, bs) {
+            map_vec2(as_, bs, |a, b| self.tys(a, b) )
                 .chain(|ts| Ok(ty::mk_tup(tcx, ts)) )
         } else {
-            Err(ty::terr_tuple_size(expected_found(self, as.len(), bs.len())))
+            Err(ty::terr_tuple_size(expected_found(self, as_.len(), bs.len())))
         }
       }
 
diff --git a/src/rustc/middle/typeck/infer/glb.rs b/src/rustc/middle/typeck/infer/glb.rs
index b69d85d9fe46..a8676a63b889 100644
--- a/src/rustc/middle/typeck/infer/glb.rs
+++ b/src/rustc/middle/typeck/infer/glb.rs
@@ -160,13 +160,13 @@ impl Glb: combine {
     }
 
     fn substs(did: ast::def_id,
-              as: &ty::substs,
+              as_: &ty::substs,
               bs: &ty::substs) -> cres<ty::substs> {
-        super_substs(&self, did, as, bs)
+        super_substs(&self, did, as_, bs)
     }
 
-    fn tps(as: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
-        super_tps(&self, as, bs)
+    fn tps(as_: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
+        super_tps(&self, as_, bs)
     }
 
     fn self_tys(a: Option<ty::t>, b: Option<ty::t>) -> cres<Option<ty::t>> {
diff --git a/src/rustc/middle/typeck/infer/lub.rs b/src/rustc/middle/typeck/infer/lub.rs
index 0c2f9ca6b132..093da5caec87 100644
--- a/src/rustc/middle/typeck/infer/lub.rs
+++ b/src/rustc/middle/typeck/infer/lub.rs
@@ -139,13 +139,13 @@ impl Lub: combine {
     }
 
     fn substs(did: ast::def_id,
-              as: &ty::substs,
+              as_: &ty::substs,
               bs: &ty::substs) -> cres<ty::substs> {
-        super_substs(&self, did, as, bs)
+        super_substs(&self, did, as_, bs)
     }
 
-    fn tps(as: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
-        super_tps(&self, as, bs)
+    fn tps(as_: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
+        super_tps(&self, as_, bs)
     }
 
     fn self_tys(a: Option<ty::t>, b: Option<ty::t>) -> cres<Option<ty::t>> {
diff --git a/src/rustc/middle/typeck/infer/sub.rs b/src/rustc/middle/typeck/infer/sub.rs
index 8c83f03838ab..1e16ad8b8d53 100644
--- a/src/rustc/middle/typeck/infer/sub.rs
+++ b/src/rustc/middle/typeck/infer/sub.rs
@@ -193,13 +193,13 @@ impl Sub: combine {
     }
 
     fn substs(did: ast::def_id,
-              as: &ty::substs,
+              as_: &ty::substs,
               bs: &ty::substs) -> cres<ty::substs> {
-        super_substs(&self, did, as, bs)
+        super_substs(&self, did, as_, bs)
     }
 
-    fn tps(as: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
-        super_tps(&self, as, bs)
+    fn tps(as_: &[ty::t], bs: &[ty::t]) -> cres<~[ty::t]> {
+        super_tps(&self, as_, bs)
     }
 
     fn self_tys(a: Option<ty::t>, b: Option<ty::t>) -> cres<Option<ty::t>> {