diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index ec51e8e691b..d700611ac4a 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -560,6 +560,25 @@ fn T_opaque_vec_ptr() -> TypeRef {
     ret T_ptr(T_vec(T_int()));
 }
 
+// Interior vector.
+//
+// TODO: Support user-defined vector sizes.
+fn T_ivec(TypeRef t) -> TypeRef {
+    ret T_struct([T_int(),          // Length ("fill")
+                  T_int(),          // Alloc (if zero, it's heapified)
+                  T_array(t, 16u)   // Body elements
+                  ]);
+}
+
+// Interior vector on the heap. Cast to this when the allocated length (second
+// element of T_ivec above) is zero.
+fn T_ivec_heap(TypeRef t) -> TypeRef {
+    ret T_struct([T_int(),          // Length ("fill")
+                  T_int(),          // Alloc (zero in this case)
+                  T_ptr(T_struct([T_int(),              // Real alloc
+                                  T_array(t, 0u)]))]);  // Body elements
+}
+
 fn T_str() -> TypeRef {
     ret T_vec(T_i8());
 }
@@ -834,6 +853,7 @@ fn type_of_inner(&@crate_ctxt cx, &span sp, &ty::t t) -> TypeRef {
         }
         case (ty::ty_char) { llty = T_char(); }
         case (ty::ty_str) { llty = T_ptr(T_str()); }
+        case (ty::ty_istr) { llty = T_ivec(T_i8()); }
         case (ty::ty_tag(_, _)) {
             if (ty::type_has_dynamic_size(cx.tcx, t)) {
                 llty = T_opaque_tag(cx.tn);
@@ -848,6 +868,9 @@ fn type_of_inner(&@crate_ctxt cx, &span sp, &ty::t t) -> TypeRef {
         case (ty::ty_vec(?mt)) {
             llty = T_ptr(T_vec(type_of_inner(cx, sp, mt.ty)));
         }
+        case (ty::ty_ivec(?mt)) {
+            llty = T_ivec(type_of_inner(cx, sp, mt.ty));
+        }
         case (ty::ty_ptr(?mt)) {
             llty = T_ptr(type_of_inner(cx, sp, mt.ty));
         }
diff --git a/src/comp/middle/ty.rs b/src/comp/middle/ty.rs
index ea2058d0785..e8a3cbbb5f0 100644
--- a/src/comp/middle/ty.rs
+++ b/src/comp/middle/ty.rs
@@ -295,6 +295,20 @@ fn mk_raw_ty(&ctxt cx, &sty st, &option::t[str] cname) -> raw_t {
     }
 
     alt (st) {
+        case (ty_nil) { /* no-op */ }
+        case (ty_bot) { /* no-op */ }
+        case (ty_bool) { /* no-op */ }
+        case (ty_int) { /* no-op */ }
+        case (ty_float) { /* no-op */ }
+        case (ty_uint) { /* no-op */ }
+        case (ty_machine(_)) { /* no-op */ }
+        case (ty_char) { /* no-op */ }
+        case (ty_str) { /* no-op */ }
+        case (ty_istr) { /* no-op */ }
+        case (ty_task) { /* no-op */ }
+        case (ty_type) { /* no-op */ }
+        case (ty_native) { /* no-op */ }
+
         case (ty_param(_)) {
             has_params = true;
         }
@@ -312,6 +326,10 @@ fn mk_raw_ty(&ctxt cx, &sty st, &option::t[str] cname) -> raw_t {
             derive_flags_mt(cx, has_params, has_vars, m);
         }
 
+        case (ty_ivec(?m)) {
+            derive_flags_mt(cx, has_params, has_vars, m);
+        }
+
         case (ty_port(?tt)) {
             derive_flags_t(cx, has_params, has_vars, tt);
         }
@@ -346,7 +364,6 @@ fn mk_raw_ty(&ctxt cx, &sty st, &option::t[str] cname) -> raw_t {
                                  m.output);
             }
         }
-        case (_) { }
     }
 
     ret rec(struct=st, cname=cname, hash=h,
@@ -581,6 +598,7 @@ fn fold_ty(&ctxt cx, fold_mode fld, t ty_0) -> t {
         case (ty_machine(_))    { /* no-op */ }
         case (ty_char)          { /* no-op */ }
         case (ty_str)           { /* no-op */ }
+        case (ty_istr)          { /* no-op */ }
         case (ty_type)          { /* no-op */ }
         case (ty_native)        { /* no-op */ }
         case (ty_task)          { /* no-op */ }
@@ -596,6 +614,10 @@ fn fold_ty(&ctxt cx, fold_mode fld, t ty_0) -> t {
             ty = copy_cname(cx, mk_vec(cx, rec(ty=fold_ty(cx, fld, tm.ty),
                                                           mut=tm.mut)), ty);
         }
+        case (ty_ivec(?tm)) {
+            ty = copy_cname(cx, mk_ivec(cx, rec(ty=fold_ty(cx, fld, tm.ty),
+                                                           mut=tm.mut)), ty);
+        }
         case (ty_port(?subty)) {
             ty = copy_cname(cx, mk_port(cx, fold_ty(cx, fld, subty)), ty);
         }