diff --git a/src/comp/middle/alias.rs b/src/comp/middle/alias.rs
index d5cecec7e6f..8ad3a4ca934 100644
--- a/src/comp/middle/alias.rs
+++ b/src/comp/middle/alias.rs
@@ -324,7 +324,7 @@ fn check_ret_ref(cx: ctx, sc: scope, mut: bool, expr: @ast::expr) {
     let mut_field = mut_field(root.ds);
     alt path_def(cx, root.ex) {
       none. { bad = some("temporary"); }
-      some(ast::def_local(did)) | some(ast::def_binding(did)) |
+      some(ast::def_local(did, _)) | some(ast::def_binding(did)) |
       some(ast::def_arg(did, _)) {
         let cur_node = did.node;
         while true {
@@ -590,7 +590,7 @@ fn ty_can_unsafely_include(cx: ctx, needle: ty::t, haystack: ty::t, mut: bool)
 
 fn def_is_local(d: ast::def, objfields_count: bool) -> bool {
     ret alt d {
-          ast::def_local(_) | ast::def_arg(_, _) | ast::def_binding(_) |
+          ast::def_local(_, _) | ast::def_arg(_, _) | ast::def_binding(_) |
           ast::def_upvar(_, _, _) {
             true
           }
diff --git a/src/comp/middle/mut.rs b/src/comp/middle/mut.rs
index 11c56456ebf..641d72af16d 100644
--- a/src/comp/middle/mut.rs
+++ b/src/comp/middle/mut.rs
@@ -245,6 +245,7 @@ fn is_immutable_def(def: def) -> option::t<str> {
         if !mut { some("upvar") } else { is_immutable_def(*inner) }
       }
       def_binding(_) { some("binding") }
+      def_local(_, let_ref.) { some("by-reference binding") }
       _ { none }
     }
 }
diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index 587ad4541ce..b8f10a8f3e7 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -608,7 +608,7 @@ fn scope_closes(sc: scope) -> option::t<bool> {
 
 fn def_is_local(d: def) -> bool {
     ret alt d {
-          ast::def_arg(_, _) | ast::def_local(_) | ast::def_binding(_) |
+          ast::def_arg(_, _) | ast::def_local(_, _) | ast::def_binding(_) |
           ast::def_upvar(_, _, _) {
             true
           }
@@ -797,10 +797,12 @@ fn lookup_in_block(name: ident, b: ast::blk_, pos: uint, loc_pos: uint,
                     let j = vec::len(locs);
                     while j > 0u {
                         j -= 1u;
-                        let (_, loc) = locs[j];
+                        let (style, loc) = locs[j];
                         if ns == ns_value && (i < pos || j < loc_pos) {
                             alt lookup_in_pat(name, loc.node.pat) {
-                              some(did) { ret some(ast::def_local(did)); }
+                              some(did) {
+                                ret some(ast::def_local(did, style));
+                              }
                               _ { }
                             }
                         }
@@ -1154,7 +1156,7 @@ fn ns_for_def(d: def) -> namespace {
           ast::def_native_mod(_) { ns_module }
           ast::def_const(_) { ns_value }
           ast::def_arg(_, _) { ns_value }
-          ast::def_local(_) { ns_value }
+          ast::def_local(_, _) { ns_value }
           ast::def_upvar(_, _, _) { ns_value }
           ast::def_variant(_, _) { ns_value }
           ast::def_ty(_) { ns_type }
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index a456608776e..c341a2a8ee7 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -2871,7 +2871,7 @@ fn trans_local_var(cx: @block_ctxt, def: ast::def) -> lval_result {
         assert (cx.fcx.llargs.contains_key(did.node));
         ret lval_mem(cx, cx.fcx.llargs.get(did.node));
       }
-      ast::def_local(did) {
+      ast::def_local(did, _) {
         assert (cx.fcx.lllocals.contains_key(did.node));
         ret lval_mem(cx, cx.fcx.lllocals.get(did.node));
       }
@@ -4399,7 +4399,7 @@ fn trans_ret(cx: @block_ctxt, e: option::t<@ast::expr>) -> result {
             let is_local = alt x.node {
               ast::expr_path(p) {
                 alt bcx_tcx(bcx).def_map.get(x.id) {
-                  ast::def_local(_) { true }
+                  ast::def_local(_, _) { true }
                   _ { false }
                 }
               }
diff --git a/src/comp/middle/tstate/auxiliary.rs b/src/comp/middle/tstate/auxiliary.rs
index 39312e17ca1..99d3252a2dc 100644
--- a/src/comp/middle/tstate/auxiliary.rs
+++ b/src/comp/middle/tstate/auxiliary.rs
@@ -575,8 +575,8 @@ fn expr_to_constr_arg(tcx: ty::ctxt, e: @expr) -> @constr_arg_use {
     alt e.node {
       expr_path(p) {
         alt tcx.def_map.find(e.id) {
-          some(def_local(id)) | some(def_arg(id, _)) | some(def_binding(id)) |
-          some(def_upvar(id, _, _)) {
+          some(def_local(id, _)) | some(def_arg(id, _)) |
+          some(def_binding(id)) | some(def_upvar(id, _, _)) {
             ret @respan(p.span,
                         carg_ident({ident: p.node.idents[0], node: id.node}));
           }
@@ -790,7 +790,8 @@ tag if_ty { if_check; plain_if; }
 fn local_node_id_to_def_id_strict(fcx: fn_ctxt, sp: span, i: node_id) ->
    def_id {
     alt local_node_id_to_def(fcx, i) {
-      some(def_local(id)) | some(def_arg(id, _)) | some(def_upvar(id, _, _)) {
+      some(def_local(id, _)) | some(def_arg(id, _)) |
+      some(def_upvar(id, _, _)) {
         ret id;
       }
       some(_) {
@@ -813,7 +814,7 @@ fn local_node_id_to_def(fcx: fn_ctxt, i: node_id) -> option::t<def> {
 
 fn local_node_id_to_def_id(fcx: fn_ctxt, i: node_id) -> option::t<def_id> {
     alt local_node_id_to_def(fcx, i) {
-      some(def_local(id)) | some(def_arg(id, _)) | some(def_binding(id)) |
+      some(def_local(id, _)) | some(def_arg(id, _)) | some(def_binding(id)) |
       some(def_upvar(id, _, _)) {
         some(id)
       }
diff --git a/src/comp/middle/tstate/bitvectors.rs b/src/comp/middle/tstate/bitvectors.rs
index 0d9e558b1f7..bfc698f7311 100644
--- a/src/comp/middle/tstate/bitvectors.rs
+++ b/src/comp/middle/tstate/bitvectors.rs
@@ -184,7 +184,7 @@ fn clear_in_poststate_expr(fcx: fn_ctxt, e: @expr, t: poststate) {
         alt vec::last(p.node.idents) {
           some(i) {
             alt local_node_id_to_def(fcx, e.id) {
-              some(def_local(d_id)) {
+              some(def_local(d_id, _)) {
                 clear_in_poststate_(bit_num(fcx, ninit(d_id.node, i)), t);
               }
               some(_) {/* ignore args (for now...) */ }
diff --git a/src/comp/middle/tstate/pre_post_conditions.rs b/src/comp/middle/tstate/pre_post_conditions.rs
index 8cb28cfaca4..d7697d47668 100644
--- a/src/comp/middle/tstate/pre_post_conditions.rs
+++ b/src/comp/middle/tstate/pre_post_conditions.rs
@@ -197,7 +197,7 @@ fn gen_if_local(fcx: fn_ctxt, lhs: @expr, rhs: @expr, larger_id: node_id,
     alt node_id_to_def(fcx.ccx, new_var) {
       some(d) {
         alt d {
-          def_local(d_id) {
+          def_local(d_id, _) {
             find_pre_post_expr(fcx, rhs);
             let p = expr_pp(fcx.ccx, rhs);
             set_pre_and_post(fcx.ccx, larger_id, p.precondition,
@@ -235,7 +235,7 @@ fn handle_update(fcx: fn_ctxt, parent: @expr, lhs: @expr, rhs: @expr,
             // pure and assign_op require the lhs to be init'd
             let df = node_id_to_def_strict(fcx.ccx.tcx, lhs.id);
             alt df {
-              def_local(d_id) {
+              def_local(d_id, _) {
                 let i =
                     bit_num(fcx,
                             ninit(d_id.node, path_to_ident(fcx.ccx.tcx, p)));
@@ -281,7 +281,7 @@ fn handle_var(fcx: fn_ctxt, rslt: pre_and_post, id: node_id, name: ident) {
 
 fn handle_var_def(fcx: fn_ctxt, rslt: pre_and_post, def: def, name: ident) {
     alt def {
-      def_local(d_id) | def_arg(d_id, _) {
+      def_local(d_id, _) | def_arg(d_id, _) {
         use_var(fcx, d_id.node);
         let i = bit_num(fcx, ninit(d_id.node, name));
         require_and_preserve(i, rslt);
diff --git a/src/comp/middle/tstate/states.rs b/src/comp/middle/tstate/states.rs
index 620592fd378..fd227d3042f 100644
--- a/src/comp/middle/tstate/states.rs
+++ b/src/comp/middle/tstate/states.rs
@@ -232,7 +232,7 @@ fn gen_if_local(fcx: fn_ctxt, p: poststate, e: @expr) -> bool {
     alt e.node {
       expr_path(pth) {
         alt fcx.ccx.tcx.def_map.find(e.id) {
-          some(def_local(loc)) {
+          some(def_local(loc, _)) {
             ret set_in_poststate_ident(fcx, loc.node,
                                        path_to_ident(fcx.ccx.tcx, pth), p);
           }
diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs
index 84400b8c03a..eeea7d4358f 100644
--- a/src/comp/middle/ty.rs
+++ b/src/comp/middle/ty.rs
@@ -2559,7 +2559,7 @@ fn def_has_ty_params(def: ast::def) -> bool {
       ast::def_mod(_) { ret false; }
       ast::def_const(_) { ret false; }
       ast::def_arg(_, _) { ret false; }
-      ast::def_local(_) { ret false; }
+      ast::def_local(_, _) { ret false; }
       ast::def_upvar(_, _, _) { ret false; }
       ast::def_variant(_, _) { ret true; }
       ast::def_ty(_) { ret false; }
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index 0e2ace6291b..226d012bf78 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -92,7 +92,7 @@ fn ty_param_kinds_and_ty_for_def(fcx: @fn_ctxt, sp: span, defn: ast::def) ->
         let typ = ty::mk_var(fcx.ccx.tcx, lookup_local(fcx, sp, id.node));
         ret {kinds: no_kinds, ty: typ};
       }
-      ast::def_local(id) {
+      ast::def_local(id, _) {
         assert (fcx.locals.contains_key(id.node));
         let typ = ty::mk_var(fcx.ccx.tcx, lookup_local(fcx, sp, id.node));
         ret {kinds: no_kinds, ty: typ};
diff --git a/src/comp/syntax/ast.rs b/src/comp/syntax/ast.rs
index 5e6269a9a8f..7f64b8de699 100644
--- a/src/comp/syntax/ast.rs
+++ b/src/comp/syntax/ast.rs
@@ -32,7 +32,7 @@ tag def {
     def_native_mod(def_id);
     def_const(def_id);
     def_arg(def_id, mode);
-    def_local(def_id);
+    def_local(def_id, let_style);
     def_variant(def_id, /* tag */def_id);
 
     /* variant */
diff --git a/src/comp/syntax/ast_util.rs b/src/comp/syntax/ast_util.rs
index b6c4eb9a929..17c8ac2cef1 100644
--- a/src/comp/syntax/ast_util.rs
+++ b/src/comp/syntax/ast_util.rs
@@ -30,7 +30,7 @@ fn def_id_of_def(d: def) -> def_id {
       def_native_mod(id) { ret id; }
       def_const(id) { ret id; }
       def_arg(id, _) { ret id; }
-      def_local(id) { ret id; }
+      def_local(id, _) { ret id; }
       def_variant(_, id) { ret id; }
       def_ty(id) { ret id; }
       def_ty_arg(_, _) { fail; }