diff --git a/src/libcore/unstable/lang.rs b/src/libcore/unstable/lang.rs
index cf71b01aeaee..c5062f25ea54 100644
--- a/src/libcore/unstable/lang.rs
+++ b/src/libcore/unstable/lang.rs
@@ -53,7 +53,7 @@ pub fn fail_(expr: *c_char, file: *c_char, line: size_t) -> ! {
 
 #[lang="fail_bounds_check"]
 pub fn fail_bounds_check(file: *c_char, line: size_t,
-                                index: size_t, len: size_t) {
+                         index: size_t, len: size_t) {
     let msg = fmt!("index out of bounds: the len is %d but the index is %d",
                     len as int, index as int);
     do str::as_buf(msg) |p, _len| {
@@ -61,12 +61,10 @@ pub fn fail_bounds_check(file: *c_char, line: size_t,
     }
 }
 
-pub fn fail_borrowed() {
+pub fn fail_borrowed(file: *c_char, line: size_t) {
     let msg = "borrowed";
     do str::as_buf(msg) |msg_p, _| {
-        do str::as_buf("???") |file_p, _| {
-            fail_(msg_p as *c_char, file_p as *c_char, 0);
-        }
+        fail_(msg_p as *c_char, file, line);
     }
 }
 
@@ -160,12 +158,27 @@ pub unsafe fn return_to_mut(a: *u8) {
     }
 }
 
+#[cfg(stage0)]
 #[lang="check_not_borrowed"]
 #[inline(always)]
 pub unsafe fn check_not_borrowed(a: *u8) {
     let a: *mut BoxRepr = transmute(a);
     if ((*a).header.ref_count & FROZEN_BIT) != 0 {
-        fail_borrowed();
+        do str::as_buf("XXX") |file_p, _| {
+            fail_borrowed(file_p as *c_char, 0);
+        }
+    }
+}
+
+#[cfg(not(stage0))]
+#[lang="check_not_borrowed"]
+#[inline(always)]
+pub unsafe fn check_not_borrowed(a: *u8,
+                                 file: *c_char,
+                                 line: size_t) {
+    let a: *mut BoxRepr = transmute(a);
+    if ((*a).header.ref_count & FROZEN_BIT) != 0 {
+        fail_borrowed(file, line);
     }
 }
 
diff --git a/src/librustc/middle/borrowck/gather_loans/mod.rs b/src/librustc/middle/borrowck/gather_loans/mod.rs
index ecdf260bffff..7ac6dfd3ec38 100644
--- a/src/librustc/middle/borrowck/gather_loans/mod.rs
+++ b/src/librustc/middle/borrowck/gather_loans/mod.rs
@@ -26,7 +26,6 @@ use middle::ty;
 use util::common::indenter;
 use util::ppaux::{Repr};
 
-use core::hashmap::HashSet;
 use syntax::ast::{m_const, m_imm, m_mutbl};
 use syntax::ast;
 use syntax::ast_util::id_range;
diff --git a/src/librustc/middle/trans/datum.rs b/src/librustc/middle/trans/datum.rs
index 705d443b1155..03c81cad50e1 100644
--- a/src/librustc/middle/trans/datum.rs
+++ b/src/librustc/middle/trans/datum.rs
@@ -105,6 +105,7 @@ use util::ppaux::ty_to_str;
 use core::container::Set; // XXX: this should not be necessary
 use core::to_bytes;
 use syntax::ast;
+use syntax::codemap::span;
 use syntax::parse::token::special_idents;
 
 #[deriving(Eq)]
@@ -556,17 +557,24 @@ pub impl Datum {
         }
     }
 
-    fn perform_write_guard(&self, bcx: block) -> block {
+    fn perform_write_guard(&self, bcx: block, span: span) -> block {
         // Create scratch space, but do not root it.
         let llval = match self.mode {
             ByValue => self.val,
             ByRef => Load(bcx, self.val),
         };
 
+        let loc = bcx.sess().parse_sess.cm.lookup_char_pos(span.lo);
+        let line = C_int(bcx.ccx(), loc.line as int);
+        let filename_cstr = C_cstr(bcx.ccx(), @/*bad*/copy loc.file.name);
+        let filename = PointerCast(bcx, filename_cstr, T_ptr(T_i8()));
+
         callee::trans_lang_call(
             bcx,
             bcx.tcx().lang_items.check_not_borrowed_fn(),
-            ~[ PointerCast(bcx, llval, T_ptr(T_i8())) ],
+            ~[PointerCast(bcx, llval, T_ptr(T_i8())),
+              filename,
+              line],
             expr::Ignore)
     }
 
@@ -621,6 +629,7 @@ pub impl Datum {
 
     fn try_deref(&self,
         bcx: block,            // block wherein to generate insn's
+        span: span,            // location where deref occurs
         expr_id: ast::node_id, // id of expr being deref'd
         derefs: uint,          // number of times deref'd already
         is_auto: bool)         // if true, only deref if auto-derefable
@@ -645,7 +654,7 @@ pub impl Datum {
         //
         // (Note: write-guarded values are always boxes)
         let bcx = if ccx.maps.write_guard_map.contains(&key) {
-            self.perform_write_guard(bcx)
+            self.perform_write_guard(bcx, span)
         } else { bcx };
 
         match ty::get(self.ty).sty {
@@ -759,7 +768,7 @@ pub impl Datum {
              expr: @ast::expr,  // the expression whose value is being deref'd
              derefs: uint)
           -> DatumBlock {
-        match self.try_deref(bcx, expr.id, derefs, false) {
+        match self.try_deref(bcx, expr.span, expr.id, derefs, false) {
             (Some(lvres), bcx) => DatumBlock { bcx: bcx, datum: lvres },
             (None, _) => {
                 bcx.ccx().sess.span_bug(
@@ -769,6 +778,7 @@ pub impl Datum {
     }
 
     fn autoderef(&self, bcx: block,
+                 span: span,
                  expr_id: ast::node_id,
                  max: uint)
               -> DatumBlock {
@@ -783,7 +793,7 @@ pub impl Datum {
         let mut bcx = bcx;
         while derefs < max {
             derefs += 1u;
-            match datum.try_deref(bcx, expr_id, derefs, true) {
+            match datum.try_deref(bcx, span, expr_id, derefs, true) {
                 (None, new_bcx) => { bcx = new_bcx; break }
                 (Some(datum_deref), new_bcx) => {
                     datum = datum_deref;
diff --git a/src/librustc/middle/trans/expr.rs b/src/librustc/middle/trans/expr.rs
index fa6f7802e7d5..bc44d7de9834 100644
--- a/src/librustc/middle/trans/expr.rs
+++ b/src/librustc/middle/trans/expr.rs
@@ -205,7 +205,7 @@ pub fn trans_to_datum(bcx: block, expr: @ast::expr) -> DatumBlock {
 
             if adj.autoderefs > 0 {
                 let DatumBlock { bcx: new_bcx, datum: new_datum } =
-                    datum.autoderef(bcx, expr.id, adj.autoderefs);
+                    datum.autoderef(bcx, expr.span, expr.id, adj.autoderefs);
                 datum = new_datum;
                 bcx = new_bcx;
             }
diff --git a/src/libsyntax/parse/parser.rs b/src/libsyntax/parse/parser.rs
index 1129e7b708ea..1ee651ede751 100644
--- a/src/libsyntax/parse/parser.rs
+++ b/src/libsyntax/parse/parser.rs
@@ -3723,7 +3723,7 @@ pub impl Parser {
                                first_item_attrs: ~[attribute])
                             -> foreign_mod {
         let ParsedItemsAndViewItems {
-            attrs_remaining: attrs_remaining,
+            attrs_remaining: _,
             view_items: view_items,
             items: _,
             foreign_items: foreign_items