diff --git a/src/comp/metadata/tydecode.rs b/src/comp/metadata/tydecode.rs
index f6d467840137..3d4c727c9c02 100644
--- a/src/comp/metadata/tydecode.rs
+++ b/src/comp/metadata/tydecode.rs
@@ -80,21 +80,21 @@ fn parse_constrs(@pstate st, str_def sd) -> (@ty::constr_def)[] {
 }
 
 fn parse_path(@pstate st, str_def sd) -> ast::path {
-    let vec[ast::ident] idents = [];
+    let ast::ident[] idents = ~[];
     fn is_last(char c) -> bool {
         ret (c == '(' || c == ':');
     }
-    idents += [parse_ident_(st, sd, is_last)];
+    idents += ~[parse_ident_(st, sd, is_last)];
     while (true) {
         alt (peek(st) as char) {
             case (':') { next(st); next(st); }
             case (?c) {
                 if (c == '(') {
                     ret respan(rec(lo=0u, hi=0u),
-                               rec(idents=idents, types=[]));
+                               rec(idents=idents, types=~[]));
                 }
                 else {
-                    idents += [parse_ident_(st, sd, is_last)];
+                    idents += ~[parse_ident_(st, sd, is_last)];
                 }
             }
         }
diff --git a/src/comp/middle/resolve.rs b/src/comp/middle/resolve.rs
index ba45497caabd..2bd533dd1634 100644
--- a/src/comp/middle/resolve.rs
+++ b/src/comp/middle/resolve.rs
@@ -18,6 +18,7 @@ import syntax::ast::respan;
 import middle::ty::constr_table;
 import syntax::visit;
 import visit::vt;
+import std::ivec;
 import std::map::hashmap;
 import std::list;
 import std::list::list;
@@ -554,9 +555,9 @@ fn mk_unresolved_msg(&ident id, &str kind) -> str {
 }
 
 // Lookup helpers
-fn lookup_path_strict(&env e, &scopes sc, &span sp, vec[ident] idents,
+fn lookup_path_strict(&env e, &scopes sc, &span sp, &ident[] idents,
                       namespace ns) -> option::t[def] {
-    auto n_idents = vec::len(idents);
+    auto n_idents = ivec::len(idents);
     auto headns = if (n_idents == 1u) { ns } else { ns_module };
     auto dcur = lookup_in_scope_strict(e, sc, sp, idents.(0), headns);
     auto i = 1u;
diff --git a/src/comp/middle/tstate/auxiliary.rs b/src/comp/middle/tstate/auxiliary.rs
index 07e4513626ad..85157850c5fc 100644
--- a/src/comp/middle/tstate/auxiliary.rs
+++ b/src/comp/middle/tstate/auxiliary.rs
@@ -641,7 +641,7 @@ fn substitute_arg(&ty::ctxt cx, &(@expr)[] actuals, @constr_arg a) ->
 }
 
 fn path_to_ident(&ty::ctxt cx, &path p) -> ident {
-    alt (std::vec::last(p.node.idents)) {
+    alt (ivec::last(p.node.idents)) {
         case (none) { cx.sess.span_fatal(p.span, "Malformed path"); }
         case (some(?i)) { ret i; }
     }
diff --git a/src/comp/middle/tstate/bitvectors.rs b/src/comp/middle/tstate/bitvectors.rs
index 6b3aa169201d..b48489a2d40f 100644
--- a/src/comp/middle/tstate/bitvectors.rs
+++ b/src/comp/middle/tstate/bitvectors.rs
@@ -230,7 +230,7 @@ fn kill_poststate(&fn_ctxt fcx, node_id id, &constr_ c) -> bool {
 fn clear_in_poststate_expr(&fn_ctxt fcx, &@expr e, &poststate t) {
     alt (e.node) {
         case (expr_path(?p)) {
-            alt (std::vec::last(p.node.idents)) {
+            alt (ivec::last(p.node.idents)) {
                 case (some(?i)) {
                     alt (local_node_id_to_def(fcx, e.id)) {
                         case (some(def_local(?d_id))) {
diff --git a/src/comp/middle/typeck.rs b/src/comp/middle/typeck.rs
index ec4a9f042e82..0a964750aacc 100644
--- a/src/comp/middle/typeck.rs
+++ b/src/comp/middle/typeck.rs
@@ -157,7 +157,7 @@ fn instantiate_path(&@fn_ctxt fcx, &ast::path pth, &ty_param_count_and_ty tpt,
                             ty_param_count);
     auto ty_param_vars = bind_result._0;
     auto ty_substs_opt;
-    auto ty_substs_len = vec::len[@ast::ty](pth.node.types);
+    auto ty_substs_len = ivec::len[@ast::ty](pth.node.types);
     if (ty_substs_len > 0u) {
         let ty::t[] ty_substs = ~[];
         auto i = 0u;
@@ -258,7 +258,7 @@ fn ast_ty_to_ty(&ty::ctxt tcx, &ty_getter getter, &@ast::ty ast_ty) -> ty::t {
         ret rec(ty=ast_ty_to_ty(tcx, getter, mt.ty), mut=mt.mut);
     }
     fn instantiate(&ty::ctxt tcx, &span sp, &ty_getter getter,
-                   &ast::def_id id, &vec[@ast::ty] args) -> ty::t {
+                   &ast::def_id id, &(@ast::ty)[] args) -> ty::t {
         // TODO: maybe record cname chains so we can do
         // "foo = int" like OCaml?
 
@@ -346,9 +346,8 @@ fn ast_ty_to_ty(&ty::ctxt tcx, &ty_getter getter, &@ast::ty ast_ty) -> ty::t {
         case (ast::ty_path(?path, ?id)) {
             alt (tcx.def_map.find(id)) {
                 case (some(ast::def_ty(?id))) {
-                    typ =
-                        instantiate(tcx, ast_ty.span, getter, id,
-                                    path.node.types);
+                    typ = instantiate(tcx, ast_ty.span, getter, id,
+                                      path.node.types);
                 }
                 case (some(ast::def_native_ty(?id))) { typ = getter(id)._1; }
                 case (some(ast::def_ty_arg(?id))) {
@@ -1696,7 +1695,7 @@ fn check_expr(&@fn_ctxt fcx, &@ast::expr expr) {
             // The definition doesn't take type parameters. If the programmer
             // supplied some, that's an error.
 
-            if (vec::len[@ast::ty](pth.node.types) > 0u) {
+            if (ivec::len[@ast::ty](pth.node.types) > 0u) {
                 fcx.ccx.tcx.sess.span_fatal(expr.span,
                                           "this kind of value does not \
                                            take type parameters");
diff --git a/src/comp/syntax/ast.rs b/src/comp/syntax/ast.rs
index 4a4b3db4785d..c072d675ac6a 100644
--- a/src/comp/syntax/ast.rs
+++ b/src/comp/syntax/ast.rs
@@ -1,4 +1,6 @@
+// The Rust abstract syntax tree.
 
+import std::ivec;
 import std::option;
 import std::str;
 import std::vec;
@@ -15,11 +17,11 @@ type fn_ident = option::t[ident];
 // FIXME: with typestate constraint, could say
 // idents and types are the same length, and are
 // non-empty
-type path_ = rec(vec[ident] idents, vec[@ty] types);
+type path_ = rec(ident[] idents, (@ty)[] types);
 
 type path = spanned[path_];
 
-fn path_name(&path p) -> str { ret str::connect(p.node.idents, "::"); }
+fn path_name(&path p) -> str { ret str::connect_ivec(p.node.idents, "::"); }
 
 type crate_num = int;
 type node_id = int;
@@ -632,11 +634,11 @@ fn ternary_to_if(&@expr e) -> @ast::expr {
 
 // Path stringification
 fn path_to_str(&ast::path pth) -> str {
-    auto result = str::connect(pth.node.idents, "::");
-    if (vec::len[@ast::ty](pth.node.types) > 0u) {
+    auto result = str::connect_ivec(pth.node.idents, "::");
+    if (ivec::len[@ast::ty](pth.node.types) > 0u) {
         fn f(&@ast::ty t) -> str { ret print::pprust::ty_to_str(*t); }
         result += "[";
-        result += str::connect(vec::map(f, pth.node.types), ",");
+        result += str::connect_ivec(ivec::map(f, pth.node.types), ",");
         result += "]";
     }
     ret result;
diff --git a/src/comp/syntax/ext/base.rs b/src/comp/syntax/ext/base.rs
index a0ba306edfa5..766dd9f3f288 100644
--- a/src/comp/syntax/ext/base.rs
+++ b/src/comp/syntax/ext/base.rs
@@ -1,3 +1,4 @@
+import std::ivec;
 import std::vec;
 import std::option;
 import std::map::hashmap;
@@ -71,8 +72,8 @@ fn expr_to_str(&ext_ctxt cx, @ast::expr expr, str error) -> str {
 fn expr_to_ident(&ext_ctxt cx, @ast::expr expr, str error) -> ast::ident {
     alt(expr.node) {
         case (ast::expr_path(?p)) {
-            if (vec::len(p.node.types) > 0u 
-                || vec::len(p.node.idents) != 1u) {
+            if (ivec::len(p.node.types) > 0u 
+                    || ivec::len(p.node.idents) != 1u) {
                 cx.span_fatal(expr.span, error);
             } else {
                 ret p.node.idents.(0);
diff --git a/src/comp/syntax/ext/fmt.rs b/src/comp/syntax/ext/fmt.rs
index 1ea2d6943744..c7e2787d502e 100644
--- a/src/comp/syntax/ext/fmt.rs
+++ b/src/comp/syntax/ext/fmt.rs
@@ -60,10 +60,9 @@ fn pieces_to_expr(&ext_ctxt cx, span sp, vec[piece] pieces,
         auto binexpr = ast::expr_binary(ast::add, lhs, rhs);
         ret @rec(id=cx.next_id(), node=binexpr, span=sp);
     }
-    fn make_path_expr(&ext_ctxt cx, span sp, vec[ast::ident] idents)
+    fn make_path_expr(&ext_ctxt cx, span sp, &ast::ident[] idents)
        -> @ast::expr {
-        let vec[@ast::ty] types = [];
-        auto path = rec(idents=idents, types=types);
+        auto path = rec(idents=idents, types=~[]);
         auto sp_path = rec(node=path, span=sp);
         auto pathexpr = ast::expr_path(sp_path);
         ret @rec(id=cx.next_id(), node=pathexpr, span=sp);
@@ -73,7 +72,7 @@ fn pieces_to_expr(&ext_ctxt cx, span sp, vec[piece] pieces,
         auto vecexpr = ast::expr_vec(exprs, ast::imm, ast::sk_rc);
         ret @rec(id=cx.next_id(), node=vecexpr, span=sp);
     }
-    fn make_call(&ext_ctxt cx, span sp, vec[ast::ident] fn_path,
+    fn make_call(&ext_ctxt cx, span sp, &ast::ident[] fn_path,
                  vec[@ast::expr] args) -> @ast::expr {
         auto pathexpr = make_path_expr(cx, sp, fn_path);
         auto callexpr = ast::expr_call(pathexpr, args);
@@ -92,11 +91,11 @@ fn pieces_to_expr(&ext_ctxt cx, span sp, vec[piece] pieces,
         auto recexpr = ast::expr_rec(astfields, option::none[@ast::expr]);
         ret @rec(id=cx.next_id(), node=recexpr, span=sp);
     }
-    fn make_path_vec(str ident) -> vec[str] {
+    fn make_path_vec(str ident) -> str[] {
         // FIXME: #fmt can't currently be used from within std
         // because we're explicitly referencing the 'std' crate here
 
-        ret ["std", "extfmt", "rt", ident];
+        ret ~["std", "extfmt", "rt", ident];
     }
     fn make_rt_path_expr(&ext_ctxt cx, span sp, str ident) ->
        @ast::expr {
diff --git a/src/comp/syntax/ext/simplext.rs b/src/comp/syntax/ext/simplext.rs
index e214524f0b79..53b37da6c277 100644
--- a/src/comp/syntax/ext/simplext.rs
+++ b/src/comp/syntax/ext/simplext.rs
@@ -1,6 +1,7 @@
 use std;
 
 import codemap::span;
+import std::ivec;
 import std::vec;
 import std::option;
 import vec::map;
@@ -50,7 +51,7 @@ fn subst_ident(&ext_ctxt cx, &vec[@ast::expr] args,
 fn subst_path(&ext_ctxt cx, &vec[@ast::expr] args, 
               @vec[ident] param_names, &path_ p, ast_fold fld) -> path_ {
     // Don't substitute into qualified names.
-    if (len(p.types) > 0u || len(p.idents) != 1u) { ret p; }
+    if (ivec::len(p.types) > 0u || ivec::len(p.idents) != 1u) { ret p; }
     alt (position(p.idents.(0), *param_names)) {
         case (some[uint](?idx)) {
             alt (args.(idx).node) {
@@ -75,7 +76,8 @@ fn subst_expr(&ext_ctxt cx, &vec[@ast::expr] args, @vec[ident] param_names,
     ret alt(e) {
         case (expr_path(?p)){
             // Don't substitute into qualified names.
-            if (len(p.node.types) > 0u || len(p.node.idents) != 1u) { e }
+            if (ivec::len(p.node.types) > 0u ||
+                    ivec::len(p.node.idents) != 1u) { e }
             alt (position(p.node.idents.(0), *param_names)) {
                 case (some[uint](?idx)) {
                     args.(idx).node
diff --git a/src/comp/syntax/fold.rs b/src/comp/syntax/fold.rs
index c53665cf71c5..e8f2c1f4dcdf 100644
--- a/src/comp/syntax/fold.rs
+++ b/src/comp/syntax/fold.rs
@@ -1,6 +1,7 @@
 import syntax::codemap::span;
 import ast::*;
 
+import std::ivec;
 import std::vec;
 import std::option;
 import vec::map;
@@ -486,8 +487,8 @@ fn noop_fold_ident(&ident i, ast_fold fld) -> ident {
 }
 
 fn noop_fold_path(&path_ p, ast_fold fld) -> path_ {
-    ret rec(idents=map(fld.fold_ident, p.idents),
-            types=map(fld.fold_ty, p.types));
+    ret rec(idents=ivec::map(fld.fold_ident, p.idents),
+            types=ivec::map(fld.fold_ty, p.types));
 }
 
 fn noop_fold_local(&local_ l, ast_fold fld) -> local_ {
diff --git a/src/comp/syntax/parse/parser.rs b/src/comp/syntax/parse/parser.rs
index 209ddcc7ff61..7c071638dbae 100644
--- a/src/comp/syntax/parse/parser.rs
+++ b/src/comp/syntax/parse/parser.rs
@@ -1,5 +1,6 @@
 
 import std::io;
+import std::ivec;
 import std::vec;
 import std::str;
 import std::option;
@@ -409,13 +410,18 @@ fn parse_ty_postfix(@ast::ty orig_t, &parser p) -> @ast::ty {
             // This is explicit type parameter instantiation.
             auto seq = parse_seq_to_end(token::RBRACKET, some(token::COMMA),
                                         parse_ty, p);
+
+            // FIXME: Remove this vec->ivec conversion.
+            auto seq_ivec = ~[];
+            for (@ast::ty typ in seq) { seq_ivec += ~[typ]; }
+
             alt (orig_t.node) {
                 case (ast::ty_path(?pth, ?ann)) {
                     auto hi = p.get_hi_pos();
                     ret @spanned(lo, hi,
                                  ast::ty_path(spanned(lo, hi,
                                               rec(idents=pth.node.idents,
-                                                  types=seq)),
+                                                  types=seq_ivec)),
                                               ann));
                 }
                 case (_) {
@@ -637,12 +643,12 @@ fn is_ident(token::token t) -> bool {
 fn parse_path(&parser p) -> ast::path {
     auto lo = p.get_lo_pos();
     auto hi = lo;
-    let vec[ast::ident] ids = [];
+    let ast::ident[] ids = ~[];
     while (true) {
         alt (p.peek()) {
             case (token::IDENT(?i, _)) {
                 hi = p.get_hi_pos();
-                ids += [p.get_str(i)];
+                ids += ~[p.get_str(i)];
                 p.bump();
                 if (p.peek() == token::MOD_SEP) { p.bump(); } else { break; }
             }
@@ -650,7 +656,7 @@ fn parse_path(&parser p) -> ast::path {
         }
     }
     hi = p.get_hi_pos();
-    ret spanned(lo, hi, rec(idents=ids, types=[]));
+    ret spanned(lo, hi, rec(idents=ids, types=~[]));
 }
 
 fn parse_path_and_ty_param_substs(&parser p) -> ast::path {
@@ -659,8 +665,13 @@ fn parse_path_and_ty_param_substs(&parser p) -> ast::path {
     if (p.peek() == token::LBRACKET) {
         auto seq = parse_seq(token::LBRACKET, token::RBRACKET,
                              some(token::COMMA), parse_ty, p);
+
+        // FIXME: Remove this vec->ivec conversion.
+        auto seq_ivec = ~[];
+        for (@ast::ty typ in seq.node) { seq_ivec += ~[typ]; }
+
         auto hi = p.get_hi_pos();
-        path = spanned(lo, hi, rec(idents=path.node.idents, types=seq.node));
+        path = spanned(lo, hi, rec(idents=path.node.idents, types=seq_ivec));
     }
     ret path;
 }
@@ -954,7 +965,7 @@ fn parse_syntax_ext(&parser p) -> @ast::expr {
 
 fn parse_syntax_ext_naked(&parser p, uint lo) -> @ast::expr {
     auto pth = parse_path(p);
-    if (vec::len(pth.node.idents) == 0u) {
+    if (ivec::len(pth.node.idents) == 0u) {
         p.fatal("expected a syntax expander name");
     }
     auto es = parse_seq(token::LPAREN, token::RPAREN,
@@ -974,7 +985,7 @@ fn parse_syntax_ext_naked(&parser p, uint lo) -> @ast::expr {
 fn expand_syntax_ext(&parser p, span sp, &ast::path path,
                      vec[@ast::expr] args, option::t[str] body) ->
    ast::expr_ {
-    assert (vec::len(path.node.idents) > 0u);
+    assert (ivec::len(path.node.idents) > 0u);
     auto extname = path.node.idents.(0);
     alt (p.get_syntax_expanders().find(extname)) {
         case (none) { p.fatal("unknown syntax expander: '" + extname + "'"); }
diff --git a/src/comp/syntax/print/pprust.rs b/src/comp/syntax/print/pprust.rs
index c3557a9573b0..43a2ee6035d9 100644
--- a/src/comp/syntax/print/pprust.rs
+++ b/src/comp/syntax/print/pprust.rs
@@ -1,9 +1,10 @@
 
-import std::uint;
+import std::ivec;
 import std::int;
-import std::vec;
-import std::str;
 import std::io;
+import std::str;
+import std::uint;
+import std::vec;
 import std::option;
 import parse::lexer;
 import syntax::codemap::codemap;
@@ -206,6 +207,17 @@ fn commasep[IN](&ps s, breaks b, vec[IN] elts, fn(&ps, &IN)  op) {
     end(s);
 }
 
+fn commasep_ivec[IN](&ps s, breaks b, &IN[] elts, fn(&ps, &IN)  op) {
+    box(s, 0u, b);
+    auto first = true;
+    for (IN elt in elts) {
+        if (first) { first = false; } else { word_space(s, ","); }
+        op(s, elt);
+    }
+    end(s);
+}
+
+
 fn commasep_cmnt[IN](&ps s, breaks b, vec[IN] elts, fn(&ps, &IN)  op,
                      fn(&IN) -> codemap::span  get_span) {
     box(s, 0u, b);
@@ -1013,9 +1025,9 @@ fn print_path(&ps s, &ast::path path) {
         if (first) { first = false; } else { word(s.s, "::"); }
         word(s.s, id);
     }
-    if (vec::len(path.node.types) > 0u) {
+    if (ivec::len(path.node.types) > 0u) {
         word(s.s, "[");
-        commasep(s, inconsistent, path.node.types, print_boxed_type);
+        commasep_ivec(s, inconsistent, path.node.types, print_boxed_type);
         word(s.s, "]");
     }
 }