diff --git a/src/comp/back/link.rs b/src/comp/back/link.rs
index 0e4f957b5ba..1b12c318163 100644
--- a/src/comp/back/link.rs
+++ b/src/comp/back/link.rs
@@ -490,8 +490,7 @@ fn mangle_internal_name_by_type_only(ccx: &@crate_ctxt, t: ty::t, name: &istr)
 
 fn mangle_internal_name_by_path_and_seq(ccx: &@crate_ctxt, path: &[istr],
                                         flav: &istr) -> istr {
-    ret mangle(path +
-               istr::from_estrs([ccx.names.next(istr::to_estr(flav))]));
+    ret mangle(path + [ccx.names.next(flav)]);
 }
 
 fn mangle_internal_name_by_path(_ccx: &@crate_ctxt, path: &[istr]) -> istr {
@@ -499,7 +498,7 @@ fn mangle_internal_name_by_path(_ccx: &@crate_ctxt, path: &[istr]) -> istr {
 }
 
 fn mangle_internal_name_by_seq(ccx: &@crate_ctxt, flav: &istr) -> istr {
-    ret istr::from_estr(ccx.names.next(istr::to_estr(flav)));
+    ret ccx.names.next(flav);
 }
 //
 // Local Variables:
diff --git a/src/comp/middle/shape.rs b/src/comp/middle/shape.rs
index 8a1201b4d83..d84105656d2 100644
--- a/src/comp/middle/shape.rs
+++ b/src/comp/middle/shape.rs
@@ -248,7 +248,7 @@ fn s_float(_tcx: &ty_ctxt) -> u8 {
 }
 
 fn mk_ctxt(llmod: ModuleRef) -> ctxt {
-    let llshapetablesty = trans_common::T_named_struct("shapes");
+    let llshapetablesty = trans_common::T_named_struct(~"shapes");
     let llshapetables = istr::as_buf(~"shapes", { |buf|
         lib::llvm::llvm::LLVMAddGlobal(llmod, llshapetablesty, buf)
     });
diff --git a/src/comp/middle/trans.rs b/src/comp/middle/trans.rs
index 200fd042416..a5fb80433bd 100644
--- a/src/comp/middle/trans.rs
+++ b/src/comp/middle/trans.rs
@@ -2492,7 +2492,7 @@ fn trans_lit_istr(cx: &@block_ctxt, s: str) -> result {
     let llvecptr = alloc_res.llptr;
     let llfirsteltptr = alloc_res.llfirsteltptr;
 
-    let llcstr = C_cstr(bcx_ccx(cx), s);
+    let llcstr = C_cstr(bcx_ccx(cx), istr::from_estr(s));
 
     // FIXME: We need to avoid this memmove
     bcx = call_memmove(bcx, llfirsteltptr, llcstr, C_uint(veclen)).bcx;
@@ -2523,16 +2523,16 @@ fn trans_crate_lit(cx: &@crate_ctxt, lit: &ast::lit) -> ValueRef {
         }
         ret C_integral(t, i as uint, s);
       }
-      ast::lit_float(fs) { ret C_float(fs); }
+      ast::lit_float(fs) { ret C_float(istr::from_estr(fs)); }
       ast::lit_mach_float(tm, s) {
         let t = T_float();
         alt tm { ast::ty_f32. { t = T_f32(); } ast::ty_f64. { t = T_f64(); } }
-        ret C_floating(s, t);
+        ret C_floating(istr::from_estr(s), t);
       }
       ast::lit_char(c) { ret C_integral(T_char(), c as uint, False); }
       ast::lit_bool(b) { ret C_bool(b); }
       ast::lit_nil. { ret C_nil(); }
-      ast::lit_str(s, ast::sk_rc.) { ret C_str(cx, s); }
+      ast::lit_str(s, ast::sk_rc.) { ret C_str(cx, istr::from_estr(s)); }
       ast::lit_str(s, ast::sk_unique.) {
         cx.sess.span_unimpl(lit.span, "unique string in this context");
       }
@@ -4317,7 +4317,8 @@ fn trans_expr_out(cx: &@block_ctxt, e: &@ast::expr, output: out_method) ->
         let ccx = bcx_ccx(cx);
         let llfnty: TypeRef =
             type_of_fn_from_ty(ccx, e.span, node_id_type(ccx, e.id), 0u);
-        let sub_cx = extend_path(cx.fcx.lcx, ccx.names.next("anon"));
+        let sub_cx = extend_path(cx.fcx.lcx,
+                                 istr::to_estr(ccx.names.next(~"anon")));
         let s = mangle_internal_name_by_path(ccx,
                                              istr::from_estrs(sub_cx.path));
         let llfn = decl_internal_fastcall_fn(ccx.llmod,
@@ -4632,7 +4633,7 @@ fn trans_fail_expr(cx: &@block_ctxt, sp_opt: &option::t<span>,
 
 fn trans_fail(cx: &@block_ctxt, sp_opt: &option::t<span>, fail_str: &str) ->
    result {
-    let V_fail_str = C_cstr(bcx_ccx(cx), fail_str);
+    let V_fail_str = C_cstr(bcx_ccx(cx), istr::from_estr(fail_str));
     ret trans_fail_value(cx, sp_opt, V_fail_str);
 }
 
@@ -4643,10 +4644,10 @@ fn trans_fail_value(cx: &@block_ctxt, sp_opt: &option::t<span>,
     alt sp_opt {
       some(sp) {
         let loc = bcx_ccx(cx).sess.lookup_pos(sp.lo);
-        V_filename = C_cstr(bcx_ccx(cx), loc.filename);
+        V_filename = C_cstr(bcx_ccx(cx), istr::from_estr(loc.filename));
         V_line = loc.line as int;
       }
-      none. { V_filename = C_cstr(bcx_ccx(cx), "<runtime>"); V_line = 0; }
+      none. { V_filename = C_cstr(bcx_ccx(cx), ~"<runtime>"); V_line = 0; }
     }
     let V_str = bld::PointerCast(cx, V_fail_str, T_ptr(T_i8()));
     V_filename = bld::PointerCast(cx, V_filename, T_ptr(T_i8()));
@@ -4924,12 +4925,12 @@ fn trans_stmt(cx: &@block_ctxt, s: &ast::stmt) -> result {
 // next three functions instead.
 fn new_block_ctxt(cx: &@fn_ctxt, parent: &block_parent, kind: block_kind,
                   name: &str) -> @block_ctxt {
-    let s = "";
+    let s = ~"";
     if cx.lcx.ccx.sess.get_opts().save_temps ||
            cx.lcx.ccx.sess.get_opts().debuginfo {
-        s = cx.lcx.ccx.names.next(name);
+        s = cx.lcx.ccx.names.next(istr::from_estr(name));
     }
-    let llbb: BasicBlockRef = istr::as_buf(istr::from_estr(s), { |buf|
+    let llbb: BasicBlockRef = istr::as_buf(s, { |buf|
         llvm::LLVMAppendBasicBlock(cx.llfn, buf)
     });
     ret @{llbb: llbb,
@@ -6325,7 +6326,7 @@ fn create_module_map(ccx: &@crate_ctxt) -> ValueRef {
                          lib::llvm::LLVMInternalLinkage as llvm::Linkage);
     let elts: [ValueRef] = [];
     for each item: @{key: istr, val: ValueRef} in ccx.module_data.items() {
-        let elt = C_struct([p2i(C_cstr(ccx, istr::to_estr(item.key))),
+        let elt = C_struct([p2i(C_cstr(ccx, item.key)),
                             p2i(item.val)]);
         elts += [elt];
     }
@@ -6370,7 +6371,8 @@ fn create_crate_map(ccx: &@crate_ctxt) -> ValueRef {
 
 fn write_metadata(cx: &@crate_ctxt, crate: &@ast::crate) {
     if !cx.sess.get_opts().library { ret; }
-    let llmeta = C_postr(metadata::encoder::encode_metadata(cx, crate));
+    let llmeta = C_postr(
+        istr::from_estr(metadata::encoder::encode_metadata(cx, crate)));
     let llconst = trans_common::C_struct([llmeta]);
     let llglobal = istr::as_buf(~"rust_metadata", { |buf|
         llvm::LLVMAddGlobal(cx.llmod, val_ty(llconst), buf)
diff --git a/src/comp/middle/trans_common.rs b/src/comp/middle/trans_common.rs
index f193f1e5623..e4c842bdf4f 100644
--- a/src/comp/middle/trans_common.rs
+++ b/src/comp/middle/trans_common.rs
@@ -63,8 +63,8 @@ import trans::type_of_fn_full;
 import trans::drop_ty;
 
 obj namegen(mutable i: int) {
-    fn next(prefix: str) -> str {
-        i += 1; ret prefix + istr::to_estr(int::str(i));
+    fn next(prefix: &istr) -> istr {
+        i += 1; ret prefix + int::str(i);
     }
 }
 
@@ -438,13 +438,15 @@ fn rslt(bcx: @block_ctxt, val: ValueRef) -> result {
     ret {bcx: bcx, val: val};
 }
 
-fn ty_str(tn: type_names, t: TypeRef) -> str {
-    ret istr::to_estr(lib::llvm::type_to_str(tn, t));
+fn ty_str(tn: type_names, t: TypeRef) -> istr {
+    ret lib::llvm::type_to_str(tn, t);
 }
 
 fn val_ty(v: ValueRef) -> TypeRef { ret llvm::LLVMTypeOf(v); }
 
-fn val_str(tn: type_names, v: ValueRef) -> str { ret ty_str(tn, val_ty(v)); }
+fn val_str(tn: type_names, v: ValueRef) -> istr {
+    ret ty_str(tn, val_ty(v));
+}
 
 // Returns the nth element of the given LLVM structure type.
 fn struct_elt(llstructty: TypeRef, n: uint) -> TypeRef {
@@ -551,9 +553,9 @@ fn T_struct(elts: &[TypeRef]) -> TypeRef {
                              False);
 }
 
-fn T_named_struct(name: &str) -> TypeRef {
+fn T_named_struct(name: &istr) -> TypeRef {
     let c = llvm::LLVMGetGlobalContext();
-    ret istr::as_buf(istr::from_estr(name), { |buf|
+    ret istr::as_buf(name, { |buf|
         llvm::LLVMStructCreateNamed(c, buf)
     });
 }
@@ -570,14 +572,14 @@ fn T_empty_struct() -> TypeRef { ret T_struct([]); }
 // existing objects, use ccx.rust_object_type.  Calling
 // T_rust_object() again will return a different one.
 fn T_rust_object() -> TypeRef {
-    let t = T_named_struct("rust_object");
+    let t = T_named_struct(~"rust_object");
     let e = T_ptr(T_empty_struct());
     set_struct_body(t, [e, e]);
     ret t;
 }
 
 fn T_task() -> TypeRef {
-    let t = T_named_struct("task");
+    let t = T_named_struct(~"task");
 
      // Refcount
      // Delegate pointer
@@ -633,7 +635,7 @@ fn T_copy_glue_fn(cx: &crate_ctxt) -> TypeRef {
 }
 
 fn T_tydesc(taskptr_type: TypeRef) -> TypeRef {
-    let tydesc = T_named_struct("tydesc");
+    let tydesc = T_named_struct(~"tydesc");
     let tydescpp = T_ptr(T_ptr(tydesc));
     let pvoid = T_ptr(T_i8());
     let glue_fn_ty =
@@ -817,14 +819,14 @@ fn C_integral(t: TypeRef, u: uint, sign_extend: Bool) -> ValueRef {
     ret llvm::LLVMRustConstSmallInt(t, u, sign_extend);
 }
 
-fn C_float(s: &str) -> ValueRef {
-    ret istr::as_buf(istr::from_estr(s), { |buf|
+fn C_float(s: &istr) -> ValueRef {
+    ret istr::as_buf(s, { |buf|
         llvm::LLVMConstRealOfString(T_float(), buf)
     });
 }
 
-fn C_floating(s: &str, t: TypeRef) -> ValueRef {
-    ret istr::as_buf(istr::from_estr(s), { |buf|
+fn C_floating(s: &istr, t: TypeRef) -> ValueRef {
+    ret istr::as_buf(s, { |buf|
         llvm::LLVMConstRealOfString(t, buf)
     });
 }
@@ -850,11 +852,11 @@ fn C_u8(i: uint) -> ValueRef { ret C_integral(T_i8(), i, False); }
 
 // This is a 'c-like' raw string, which differs from
 // our boxed-and-length-annotated strings.
-fn C_cstr(cx: &@crate_ctxt, s: &str) -> ValueRef {
-    let sc = istr::as_buf(istr::from_estr(s), { |buf|
-        llvm::LLVMConstString(buf, str::byte_len(s), False)
+fn C_cstr(cx: &@crate_ctxt, s: &istr) -> ValueRef {
+    let sc = istr::as_buf(s, { |buf|
+        llvm::LLVMConstString(buf, istr::byte_len(s), False)
     });
-    let g = istr::as_buf(istr::from_estr(cx.names.next("str")), { |buf|
+    let g = istr::as_buf(cx.names.next(~"str"), { |buf|
         llvm::LLVMAddGlobal(cx.llmod, val_ty(sc), buf)
     });
     llvm::LLVMSetInitializer(g, sc);
@@ -865,19 +867,19 @@ fn C_cstr(cx: &@crate_ctxt, s: &str) -> ValueRef {
 
 
 // A rust boxed-and-length-annotated string.
-fn C_str(cx: &@crate_ctxt, s: &str) -> ValueRef {
+fn C_str(cx: &@crate_ctxt, s: &istr) -> ValueRef {
     let len =
-        str::byte_len(s); // 'alloc'
+        istr::byte_len(s); // 'alloc'
                           // 'fill'
                           // 'pad'
 
-    let cstr = istr::as_buf(istr::from_estr(s), { |buf|
+    let cstr = istr::as_buf(s, { |buf|
         llvm::LLVMConstString(buf, len, False)
     });
     let box =
         C_struct([C_int(abi::const_refcount as int), C_int(len + 1u as int),
                   C_int(len + 1u as int), C_int(0), cstr]);
-    let g = istr::as_buf(istr::from_estr(cx.names.next("str")), { |buf|
+    let g = istr::as_buf(cx.names.next(~"str"), { |buf|
         llvm::LLVMAddGlobal(cx.llmod, val_ty(box), buf)
     });
     llvm::LLVMSetInitializer(g, box);
@@ -887,9 +889,9 @@ fn C_str(cx: &@crate_ctxt, s: &str) -> ValueRef {
 }
 
 // Returns a Plain Old LLVM String:
-fn C_postr(s: &str) -> ValueRef {
-    ret istr::as_buf(istr::from_estr(s), { |buf|
-        llvm::LLVMConstString(buf, str::byte_len(s), False)
+fn C_postr(s: &istr) -> ValueRef {
+    ret istr::as_buf(s, { |buf|
+        llvm::LLVMConstString(buf, istr::byte_len(s), False)
     });
 }
 
@@ -922,8 +924,7 @@ fn C_bytes(bytes: &[u8]) -> ValueRef {
 
 fn C_shape(ccx: &@crate_ctxt, bytes: &[u8]) -> ValueRef {
     let llshape = C_bytes(bytes);
-    let llglobal = istr::as_buf(
-        istr::from_estr(ccx.names.next("shape")), { |buf|
+    let llglobal = istr::as_buf(ccx.names.next(~"shape"), { |buf|
         llvm::LLVMAddGlobal(ccx.llmod, val_ty(llshape), buf)
     });
     llvm::LLVMSetInitializer(llglobal, llshape);