diff --git a/src/compiletest/compiletest.rc b/src/compiletest/compiletest.rc
index 6db926b29e3..7f691cc1995 100644
--- a/src/compiletest/compiletest.rc
+++ b/src/compiletest/compiletest.rc
@@ -12,7 +12,6 @@
 
 #[allow(vecs_implicitly_copyable)];
 #[allow(non_camel_case_types)];
-#[allow(deprecated_mode)];
 #[allow(deprecated_pattern)];
 
 extern mod std(vers = "0.7-pre");
diff --git a/src/libcore/comm.rs b/src/libcore/comm.rs
index 140eb41fdf3..b1f60ec4690 100644
--- a/src/libcore/comm.rs
+++ b/src/libcore/comm.rs
@@ -13,7 +13,6 @@ Message passing
 */
 
 use cast::{transmute, transmute_mut};
-use cast;
 use either::{Either, Left, Right};
 use kinds::Owned;
 use option::{Option, Some, None};
@@ -150,7 +149,7 @@ impl<T: Owned> GenericChan<T> for Chan<T> {
     #[inline(always)]
     fn send(&self, x: T) {
         unsafe {
-            let mut self_endp = transmute_mut(&self.endp);
+            let self_endp = transmute_mut(&self.endp);
             let endp = replace(self_endp, None);
             *self_endp = Some(streamp::client::data(endp.unwrap(), x))
         }
@@ -161,7 +160,7 @@ impl<T: Owned> GenericSmartChan<T> for Chan<T> {
     #[inline(always)]
     fn try_send(&self, x: T) -> bool {
         unsafe {
-            let mut self_endp = transmute_mut(&self.endp);
+            let self_endp = transmute_mut(&self.endp);
             let endp = replace(self_endp, None);
             match streamp::client::try_data(endp.unwrap(), x) {
                 Some(next) => {
@@ -178,7 +177,7 @@ impl<T: Owned> GenericPort<T> for Port<T> {
     #[inline(always)]
     fn recv(&self) -> T {
         unsafe {
-            let mut self_endp = transmute_mut(&self.endp);
+            let self_endp = transmute_mut(&self.endp);
             let endp = replace(self_endp, None);
             let streamp::data(x, endp) = recv(endp.unwrap());
             *self_endp = Some(endp);
@@ -189,7 +188,7 @@ impl<T: Owned> GenericPort<T> for Port<T> {
     #[inline(always)]
     fn try_recv(&self) -> Option<T> {
         unsafe {
-            let mut self_endp = transmute_mut(&self.endp);
+            let self_endp = transmute_mut(&self.endp);
             let endp = replace(self_endp, None);
             match try_recv(endp.unwrap()) {
                 Some(streamp::data(x, endp)) => {
@@ -206,7 +205,7 @@ impl<T: Owned> Peekable<T> for Port<T> {
     #[inline(always)]
     fn peek(&self) -> bool {
         unsafe {
-            let mut self_endp = transmute_mut(&self.endp);
+            let self_endp = transmute_mut(&self.endp);
             let mut endp = replace(self_endp, None);
             let peek = match endp {
                 Some(ref mut endp) => peek(endp),
@@ -220,12 +219,10 @@ impl<T: Owned> Peekable<T> for Port<T> {
 
 impl<T: Owned> Selectable for Port<T> {
     fn header(&mut self) -> *mut PacketHeader {
-        unsafe {
             match self.endp {
                 Some(ref mut endp) => endp.header(),
                 None => fail!(~"peeking empty stream")
             }
-        }
     }
 }
 
@@ -259,7 +256,7 @@ pub impl<T: Owned> PortSet<T> {
 impl<T:Owned> GenericPort<T> for PortSet<T> {
     fn try_recv(&self) -> Option<T> {
         unsafe {
-            let mut self_ports = transmute_mut(&self.ports);
+            let self_ports = transmute_mut(&self.ports);
             let mut result = None;
             // we have to swap the ports array so we aren't borrowing
             // aliasable mutable memory.
@@ -351,7 +348,7 @@ pub mod oneshot {
     pub fn init<T: Owned>() -> (client::Oneshot<T>, server::Oneshot<T>) {
         pub use core::pipes::HasBuffer;
 
-        let mut buffer = ~::core::pipes::Buffer {
+        let buffer = ~::core::pipes::Buffer {
             header: ::core::pipes::BufferHeader(),
             data: __Buffer {
                 Oneshot: ::core::pipes::mk_packet::<Oneshot<T>>()
diff --git a/src/libcore/core.rc b/src/libcore/core.rc
index dcb61d47341..d029fbc07f6 100644
--- a/src/libcore/core.rc
+++ b/src/libcore/core.rc
@@ -61,7 +61,6 @@ they contained the following prologue:
 #[no_core];
 
 #[deny(non_camel_case_types)];
-#[allow(deprecated_mutable_fields)];
 
 // Make core testable by not duplicating lang items. See #2912
 #[cfg(test)] extern mod realcore(name = "core", vers = "0.7-pre");
diff --git a/src/libcore/pipes.rs b/src/libcore/pipes.rs
index fe9c78198bb..9b664b334ba 100644
--- a/src/libcore/pipes.rs
+++ b/src/libcore/pipes.rs
@@ -348,7 +348,7 @@ pub fn send<T,Tbuffer>(mut p: SendPacketBuffered<T,Tbuffer>,
                        payload: T)
                        -> bool {
     let header = p.header();
-    let mut p_ = p.unwrap();
+    let p_ = p.unwrap();
     let p = unsafe { &mut *p_ };
     assert!(ptr::to_unsafe_ptr(&(p.header)) == header);
     assert!(p.payload.is_none());
@@ -405,10 +405,8 @@ a message, or `Some(T)` if a message was received.
 */
 pub fn try_recv<T:Owned,Tbuffer:Owned>(mut p: RecvPacketBuffered<T, Tbuffer>)
                                        -> Option<T> {
-    let mut p_ = p.unwrap();
-    let mut p = unsafe {
-        &mut *p_
-    };
+    let p_ = p.unwrap();
+    let p = unsafe { &mut *p_ };
 
     do (|| {
         try_recv_(p)
diff --git a/src/libcore/reflect.rs b/src/libcore/reflect.rs
index 47de360f589..30f60dce041 100644
--- a/src/libcore/reflect.rs
+++ b/src/libcore/reflect.rs
@@ -409,7 +409,6 @@ impl<V:TyVisitor + MovePtr> TyVisitor for MovePtrAdaptor<V> {
                                 disr_val: int,
                                 n_fields: uint,
                                 name: &str) -> bool {
-        self.inner.push_ptr(); // NOTE remove after next snapshot
         if ! self.inner.visit_enter_enum_variant(variant, disr_val,
                                                  n_fields, name) {
             return false;
@@ -433,7 +432,6 @@ impl<V:TyVisitor + MovePtr> TyVisitor for MovePtrAdaptor<V> {
                                                  n_fields, name) {
             return false;
         }
-        self.inner.pop_ptr(); // NOTE remove after next snapshot
         true
     }
 
diff --git a/src/libcore/rt/uv/net.rs b/src/libcore/rt/uv/net.rs
index 04b9008b067..068d6db2a43 100644
--- a/src/libcore/rt/uv/net.rs
+++ b/src/libcore/rt/uv/net.rs
@@ -152,8 +152,7 @@ pub impl StreamWatcher {
         extern fn close_cb(handle: *uvll::uv_stream_t) {
             let mut stream_watcher: StreamWatcher = NativeHandle::from_native_handle(handle);
             {
-                let mut data = get_watcher_data(&mut stream_watcher);
-                data.close_cb.swap_unwrap()();
+                get_watcher_data(&mut stream_watcher).close_cb.swap_unwrap()();
             }
             drop_watcher_data(&mut stream_watcher);
             unsafe { free_handle(handle as *c_void) }
@@ -214,8 +213,7 @@ pub impl TcpWatcher {
             assert!(get_watcher_data(self).connect_cb.is_none());
             get_watcher_data(self).connect_cb = Some(cb);
 
-            let mut connect_watcher = ConnectRequest::new();
-            let connect_handle = connect_watcher.native_handle();
+            let connect_handle = ConnectRequest::new().native_handle();
             match address {
                 Ipv4(*) => {
                     do ip4_as_uv_ip4(address) |addr| {
diff --git a/src/libcore/rt/uvio.rs b/src/libcore/rt/uvio.rs
index ab8aea2b63c..62a165b6d77 100644
--- a/src/libcore/rt/uvio.rs
+++ b/src/libcore/rt/uvio.rs
@@ -46,8 +46,7 @@ impl Drop for UvEventLoop {
         let self = unsafe {
             transmute::<&UvEventLoop, &mut UvEventLoop>(self)
         };
-        let mut uv_loop = self.uvio.uv_loop();
-        uv_loop.close();
+        self.uvio.uv_loop().close();
     }
 }
 
@@ -189,9 +188,8 @@ impl TcpListener for UvTcpListener {
                 let maybe_stream = if status.is_none() {
                     let mut server_stream_watcher = server_stream_watcher;
                     let mut loop_ = loop_from_watcher(&server_stream_watcher);
-                    let mut client_tcp_watcher = TcpWatcher::new(&mut loop_);
-                    let client_tcp_watcher = client_tcp_watcher.as_stream();
-                    // XXX: Need's to be surfaced in interface
+                    let client_tcp_watcher = TcpWatcher::new(&mut loop_).as_stream();
+                    // XXX: Needs to be surfaced in interface
                     server_stream_watcher.accept(client_tcp_watcher);
                     Some(~UvStream::new(client_tcp_watcher))
                 } else {
diff --git a/src/libcore/task/spawn.rs b/src/libcore/task/spawn.rs
index 846d4a34950..327b7a988aa 100644
--- a/src/libcore/task/spawn.rs
+++ b/src/libcore/task/spawn.rs
@@ -472,7 +472,7 @@ fn gen_child_taskgroup(linked: bool, supervised: bool)
         /*##################################################################*
          * Step 1. Get spawner's taskgroup info.
          *##################################################################*/
-        let mut spawner_group: @@mut TCB =
+        let spawner_group: @@mut TCB =
             match local_get(OldHandle(spawner), taskgroup_key!()) {
                 None => {
                     // Main task, doing first spawn ever. Lazily initialise
diff --git a/src/librustc/middle/borrowck/mod.rs b/src/librustc/middle/borrowck/mod.rs
index 75acc2d9511..a6105534077 100644
--- a/src/librustc/middle/borrowck/mod.rs
+++ b/src/librustc/middle/borrowck/mod.rs
@@ -10,7 +10,6 @@
 
 /*! See doc.rs for a thorough explanation of the borrow checker */
 
-use core;
 use core::prelude::*;
 
 use mc = middle::mem_categorization;
@@ -22,6 +21,7 @@ use middle::dataflow::DataFlowOperator;
 use util::common::stmt_set;
 use util::ppaux::{note_and_explain_region, Repr};
 
+use core;
 use core::hashmap::{HashSet, HashMap};
 use core::io;
 use core::result::{Result};
diff --git a/src/librustc/middle/mem_categorization.rs b/src/librustc/middle/mem_categorization.rs
index 7675efa76f4..436905f9a53 100644
--- a/src/librustc/middle/mem_categorization.rs
+++ b/src/librustc/middle/mem_categorization.rs
@@ -571,8 +571,6 @@ pub impl mem_categorization_ctxt {
         }
     }
 
-    /// The `field_id` parameter is the ID of the enclosing expression or
-    /// pattern. It is used to determine which variant of an enum is in use.
     fn cat_field<N:ast_node>(&self,
                              node: N,
                              base_cmt: cmt,
diff --git a/src/librustc/middle/resolve.rs b/src/librustc/middle/resolve.rs
index 9d75fa644a3..515ebc0e8db 100644
--- a/src/librustc/middle/resolve.rs
+++ b/src/librustc/middle/resolve.rs
@@ -60,7 +60,7 @@ use syntax::ast_util::{def_id_of_def, local_def};
 use syntax::ast_util::{path_to_ident, walk_pat, trait_method_to_ty_method};
 use syntax::ast_util::{Privacy, Public, Private};
 use syntax::ast_util::{variant_visibility_to_privacy, visibility_to_privacy};
-use syntax::attr::{attr_metas, contains_name, attrs_contains_name};
+use syntax::attr::{attr_metas, contains_name};
 use syntax::parse::token::ident_interner;
 use syntax::parse::token::special_idents;
 use syntax::print::pprust::path_to_str;
diff --git a/src/librustc/middle/typeck/infer/region_inference.rs b/src/librustc/middle/typeck/infer/region_inference.rs
index 73c120ad35d..11a7aafe1cd 100644
--- a/src/librustc/middle/typeck/infer/region_inference.rs
+++ b/src/librustc/middle/typeck/infer/region_inference.rs
@@ -544,12 +544,12 @@ use middle::typeck::infer::cres;
 use util::common::indenter;
 use util::ppaux::note_and_explain_region;
 
+use core;
 use core::cell::{Cell, empty_cell};
 use core::hashmap::{HashMap, HashSet};
 use core::to_bytes;
 use core::uint;
 use core::vec;
-use core;
 use syntax::codemap::span;
 use syntax::ast;
 
diff --git a/src/libstd/ebml.rs b/src/libstd/ebml.rs
index a57a16fb87d..98618e4928b 100644
--- a/src/libstd/ebml.rs
+++ b/src/libstd/ebml.rs
@@ -634,13 +634,6 @@ pub mod writer {
     use core::vec;
 
     // ebml writing
-    #[cfg(stage0)]
-    pub struct Encoder {
-        writer: @io::Writer,
-        priv mut size_positions: ~[uint],
-    }
-
-    #[cfg(not(stage0))]
     pub struct Encoder {
         writer: @io::Writer,
         priv size_positions: ~[uint],
diff --git a/src/libstd/fileinput.rs b/src/libstd/fileinput.rs
index 2c5cbc1cbf9..4e205b50014 100644
--- a/src/libstd/fileinput.rs
+++ b/src/libstd/fileinput.rs
@@ -94,8 +94,6 @@ total line count).
     }
 */
 
-#[allow(deprecated_mutable_fields)];
-
 use core::io::ReaderUtil;
 
 /**
@@ -212,8 +210,8 @@ impl FileInput {
     pub fn next_file(&self) -> bool {
         // No more files
 
-        // Compiler whines about "illegal borrow unless pure" for
-        // files.is_empty()
+        // unsafe block can be removed after the next snapshot
+        // (next one after 2013-05-03)
         if unsafe { self.fi.files.is_empty() } {
             self.fi.current_reader = None;
             return false;
@@ -337,7 +335,8 @@ impl io::Reader for FileInput {
     fn eof(&self) -> bool {
         // we've run out of files, and current_reader is either None or eof.
 
-        // compiler whines about illegal borrows for files.is_empty()
+        // unsafe block can be removed after the next snapshot
+        // (next one after 2013-05-03)
         (unsafe { self.fi.files.is_empty() }) &&
             match self.fi.current_reader { None => true, Some(r) => r.eof() }
 
@@ -380,8 +379,7 @@ Fails when attempting to read from a file that can't be opened.
 */
 #[cfg(stage0)]
 pub fn input(f: &fn(&str) -> bool) {
-    let mut i = FileInput::from_args();
-    i.each_line(f);
+    FileInput::from_args().each_line(f);
 }
 /**
 Iterate directly over the command line arguments (no arguments implies
@@ -404,8 +402,7 @@ Fails when attempting to read from a file that can't be opened.
 */
 #[cfg(stage0)]
 pub fn input_state(f: &fn(&str, FileInputState) -> bool) {
-    let mut i = FileInput::from_args();
-    i.each_line_state(f);
+    FileInput::from_args().each_line_state(f);
 }
 /**
 Iterate directly over the command line arguments (no arguments
@@ -427,8 +424,7 @@ Fails when attempting to read from a file that can't be opened.
 */
 #[cfg(stage0)]
 pub fn input_vec(files: ~[Option<Path>], f: &fn(&str) -> bool) {
-    let mut i = FileInput::from_vec(files);
-    i.each_line(f);
+    FileInput::from_vec(files).each_line(f);
 }
 /**
 Iterate over a vector of files (an empty vector implies just `stdin`).
@@ -450,8 +446,7 @@ Fails when attempting to read from a file that can't be opened.
 #[cfg(stage0)]
 pub fn input_vec_state(files: ~[Option<Path>],
                        f: &fn(&str, FileInputState) -> bool) {
-    let mut i = FileInput::from_vec(files);
-    i.each_line_state(f);
+    FileInput::from_vec(files).each_line_state(f);
 }
 /**
 Iterate over a vector of files (an empty vector implies just `stdin`)
diff --git a/src/libstd/future.rs b/src/libstd/future.rs
index ac23ea1a6e2..9906be13cb9 100644
--- a/src/libstd/future.rs
+++ b/src/libstd/future.rs
@@ -29,17 +29,12 @@ use core::task;
 use core::util::replace;
 
 #[doc = "The future type"]
-#[cfg(stage0)]
-pub struct Future<A> {
-    priv mut state: FutureState<A>,
-}
-
-#[doc = "The future type"]
-#[cfg(not(stage0))]
 pub struct Future<A> {
     priv state: FutureState<A>,
 }
 
+// n.b. It should be possible to get rid of this.
+// Add a test, though -- tjc
 // FIXME(#2829) -- futures should not be copyable, because they close
 // over ~fn's that have pipes and so forth within!
 #[unsafe_destructor]
@@ -62,37 +57,6 @@ pub impl<A:Copy> Future<A> {
 }
 
 pub impl<A> Future<A> {
-    #[cfg(stage0)]
-    fn get_ref<'a>(&'a self) -> &'a A {
-        /*!
-        * Executes the future's closure and then returns a borrowed
-        * pointer to the result.  The borrowed pointer lasts as long as
-        * the future.
-        */
-        unsafe {
-            {
-                match self.state {
-                    Forced(ref mut v) => { return cast::transmute(v); }
-                    Evaluating => fail!(~"Recursive forcing of future!"),
-                    Pending(_) => {}
-                }
-            }
-            {
-                let state = replace(&mut self.state, Evaluating);
-                match state {
-                    Forced(_) | Evaluating => fail!(~"Logic error."),
-                    Pending(f) => {
-                        self.state = Forced(f());
-                        cast::transmute(self.get_ref())
-                    }
-                }
-            }
-        }
-    }
-
-    #[cfg(stage1)]
-    #[cfg(stage2)]
-    #[cfg(stage3)]
     fn get_ref<'a>(&'a mut self) -> &'a A {
         /*!
         * Executes the future's closure and then returns a borrowed
diff --git a/src/libstd/json.rs b/src/libstd/json.rs
index c815c9dd480..2acbcf5c7ec 100644
--- a/src/libstd/json.rs
+++ b/src/libstd/json.rs
@@ -220,13 +220,6 @@ impl serialize::Encoder for Encoder {
     }
 }
 
-#[cfg(stage0)]
-pub struct PrettyEncoder {
-    priv wr: @io::Writer,
-    priv mut indent: uint,
-}
-
-#[cfg(not(stage0))]
 pub struct PrettyEncoder {
     priv wr: @io::Writer,
     priv indent: uint,
@@ -845,12 +838,6 @@ pub fn from_str(s: &str) -> Result<Json, Error> {
     }
 }
 
-#[cfg(stage0)]
-pub struct Decoder {
-    priv mut stack: ~[Json],
-}
-
-#[cfg(not(stage0))]
 pub struct Decoder {
     priv stack: ~[Json],
 }
diff --git a/src/libstd/net_tcp.rs b/src/libstd/net_tcp.rs
index 7e47106977f..20e1a272910 100644
--- a/src/libstd/net_tcp.rs
+++ b/src/libstd/net_tcp.rs
@@ -972,19 +972,17 @@ impl io::Reader for TcpSocketBuf {
 /// Implementation of `io::Reader` trait for a buffered `net::tcp::TcpSocket`
 impl io::Writer for TcpSocketBuf {
     pub fn write(&self, data: &[u8]) {
-        unsafe {
-            let socket_data_ptr: *TcpSocketData =
-                &(*((*(self.data)).sock).socket_data);
-            let w_result = write_common_impl(socket_data_ptr,
-                                             vec::slice(data,
-                                                        0,
-                                                        data.len()).to_vec());
-            if w_result.is_err() {
-                let err_data = w_result.get_err();
-                debug!(
-                    "ERROR sock_buf as io::writer.writer err: %? %?",
-                         err_data.err_name, err_data.err_msg);
-            }
+        let socket_data_ptr: *TcpSocketData =
+            &(*((*(self.data)).sock).socket_data);
+        let w_result = write_common_impl(socket_data_ptr,
+                                         vec::slice(data,
+                                                    0,
+                                                    data.len()).to_vec());
+        if w_result.is_err() {
+            let err_data = w_result.get_err();
+            debug!(
+                "ERROR sock_buf as io::writer.writer err: %? %?",
+                err_data.err_name, err_data.err_msg);
         }
     }
     fn seek(&self, dist: int, seek: io::SeekStyle) {
diff --git a/src/libstd/num/bigint.rs b/src/libstd/num/bigint.rs
index e64e97adfa3..7b39b200079 100644
--- a/src/libstd/num/bigint.rs
+++ b/src/libstd/num/bigint.rs
@@ -16,8 +16,6 @@ A BigUint is represented as an array of BigDigits.
 A BigInt is a combination of BigUint and Sign.
 */
 
-#[deny(deprecated_mutable_fields)];
-
 use core::cmp::{Eq, Ord, TotalEq, TotalOrd, Ordering, Less, Equal, Greater};
 use core::num::{IntConvertible, Zero, One, ToStrRadix, FromStrRadix};
 
diff --git a/src/libstd/std.rc b/src/libstd/std.rc
index 70bd5ceef98..915aab59a71 100644
--- a/src/libstd/std.rc
+++ b/src/libstd/std.rc
@@ -28,9 +28,6 @@ not required in or otherwise suitable for the core library.
 
 #[deny(non_camel_case_types)];
 
-// Allow mutable fields only in stage0.
-#[warn(deprecated_mutable_fields)];
-
 pub mod uv_ll;
 
 // General io and system-services modules
diff --git a/src/libstd/test.rs b/src/libstd/test.rs
index c320bcea77c..bb90b783444 100644
--- a/src/libstd/test.rs
+++ b/src/libstd/test.rs
@@ -410,9 +410,10 @@ type MonitorMsg = (TestDesc, TestResult);
 fn run_tests(opts: &TestOpts,
              tests: ~[TestDescAndFn],
              callback: @fn(e: TestEvent)) {
-    let mut filtered_tests = filter_tests(opts, tests);
 
-    let filtered_descs = filtered_tests.map(|t| copy t.desc);
+    let filtered_tests = filter_tests(opts, tests);
+    let filtered_descs = filtered_tests.map(|t| t.desc);
+
     callback(TeFiltered(filtered_descs));
 
     let (filtered_tests, filtered_benchs) =
diff --git a/src/libsyntax/ext/expand.rs b/src/libsyntax/ext/expand.rs
index 5129fa6ebd2..0fe28dadbc7 100644
--- a/src/libsyntax/ext/expand.rs
+++ b/src/libsyntax/ext/expand.rs
@@ -27,7 +27,6 @@ pub fn expand_expr(extsbox: @mut SyntaxEnv,
                    fld: @ast_fold,
                    orig: @fn(&expr_, span, @ast_fold) -> (expr_, span))
                 -> (expr_, span) {
-    let mut cx = cx;
     match *e {
         // expr_mac should really be expr_ext or something; it's the
         // entry-point for all syntax extensions.
@@ -113,7 +112,6 @@ pub fn expand_mod_items(extsbox: @mut SyntaxEnv,
                         fld: @ast_fold,
                         orig: @fn(&ast::_mod, @ast_fold) -> ast::_mod)
                      -> ast::_mod {
-    let mut cx = cx;
 
     // Fold the contents first:
     let module_ = orig(module_, fld);
diff --git a/src/libsyntax/ext/pipes/mod.rs b/src/libsyntax/ext/pipes/mod.rs
index 85c578bc2ce..642f22e9736 100644
--- a/src/libsyntax/ext/pipes/mod.rs
+++ b/src/libsyntax/ext/pipes/mod.rs
@@ -74,7 +74,7 @@ pub fn expand_proto(cx: @ext_ctxt, _sp: span, id: ast::ident,
     let rdr = tt_rdr as @reader;
     let rust_parser = Parser(sess, cfg, rdr.dup());
 
-    let mut proto = rust_parser.parse_proto(cx.str_of(id));
+    let proto = rust_parser.parse_proto(cx.str_of(id));
 
     // check for errors
     visit(proto, cx);
diff --git a/src/libsyntax/ext/tt/macro_parser.rs b/src/libsyntax/ext/tt/macro_parser.rs
index 0c1e619985d..46b09aca8b2 100644
--- a/src/libsyntax/ext/tt/macro_parser.rs
+++ b/src/libsyntax/ext/tt/macro_parser.rs
@@ -247,8 +247,8 @@ pub fn parse(
         let TokenAndSpan {tok: tok, sp: sp} = rdr.peek();
 
         /* we append new items to this while we go */
-        while cur_eis.len() > 0u { /* for each Earley Item */
-            let mut ei = cur_eis.pop();
+        while !cur_eis.is_empty() { /* for each Earley Item */
+            let ei = cur_eis.pop();
 
             let idx = ei.idx;
             let len = ei.elts.len();
diff --git a/src/libsyntax/parse/comments.rs b/src/libsyntax/parse/comments.rs
index 4e29c3dcf18..acfd18c74de 100644
--- a/src/libsyntax/parse/comments.rs
+++ b/src/libsyntax/parse/comments.rs
@@ -202,15 +202,14 @@ fn all_whitespace(s: ~str, begin: uint, end: uint) -> bool {
 
 fn trim_whitespace_prefix_and_push_line(lines: &mut ~[~str],
                                         s: ~str, col: CharPos) {
-    let mut s1;
-    let len = str::len(s);
+    let len = s.len();
     // FIXME #3961: Doing bytewise comparison and slicing with CharPos
     let col = col.to_uint();
-    if all_whitespace(s, 0u, uint::min(len, col)) {
+    let s1 = if all_whitespace(s, 0, uint::min(len, col)) {
         if col < len {
-            s1 = str::slice(s, col, len).to_owned();
-        } else { s1 = ~""; }
-    } else { s1 = s; }
+            str::slice(s, col, len).to_owned()
+        } else {  ~"" }
+    } else { s };
     debug!("pushing line: %s", s1);
     lines.push(s1);
 }