diff --git a/src/compiletest/procsrv.rs b/src/compiletest/procsrv.rs
index 90f88ea9d7a4bcd9ae2e1864895fb8e532509df8..39076b700298bdf3149298249086c8fd71173d79 100644
--- a/src/compiletest/procsrv.rs
+++ b/src/compiletest/procsrv.rs
@@ -104,7 +104,7 @@ fn readclose(fd: c_int) -> ~str {
     let mut buf = ~"";
     while !reader.eof() {
         let bytes = reader.read_bytes(4096u);
-        str::push_str(buf, str::from_bytes(bytes));
+        str::push_str(&mut buf, str::from_bytes(bytes));
     }
     os::fclose(file);
     return buf;
diff --git a/src/libcore/char.rs b/src/libcore/char.rs
index aa9a558edc79260796d1770a3011edf58214e695..d7e553073bf02665b29dbbc76982f4e82fa1080a 100644
--- a/src/libcore/char.rs
+++ b/src/libcore/char.rs
@@ -141,9 +141,9 @@ fn escape_unicode(c: char) -> ~str {
                     else { ('U', 8u) });
     assert str::len(s) <= pad;
     let mut out = ~"\\";
-    str::push_str(out, str::from_char(c));
-    for uint::range(str::len(s), pad) |_i| { str::push_str(out, ~"0"); }
-    str::push_str(out, s);
+    str::push_str(&mut out, str::from_char(c));
+    for uint::range(str::len(s), pad) |_i| { str::push_str(&mut out, ~"0"); }
+    str::push_str(&mut out, s);
     move out
 }
 
diff --git a/src/libcore/extfmt.rs b/src/libcore/extfmt.rs
index 244fc637aa2a2c2ab40979dcb21a1ce6a032df67..624cb97dbca34214b150bd974b4335b0003c96a8 100644
--- a/src/libcore/extfmt.rs
+++ b/src/libcore/extfmt.rs
@@ -293,9 +293,9 @@ enum Ty { TyDefault, TyBits, TyHexUpper, TyHexLower, TyOctal, }
         let mut s : ~str = int_to_str_prec(i, radix, prec);
         if 0 <= i {
             if have_flag(cv.flags, flag_sign_always) {
-                unsafe { str::unshift_char(s, '+') };
+                unsafe { str::unshift_char(&mut s, '+') };
             } else if have_flag(cv.flags, flag_space_for_sign) {
-                unsafe { str::unshift_char(s, ' ') };
+                unsafe { str::unshift_char(&mut s, ' ') };
             }
         }
         return unsafe { pad(cv, s, PadSigned) };
@@ -463,13 +463,13 @@ fn pad(cv: Conv, &s: ~str, mode: PadMode) -> ~str {
         // instead.
 
         if signed && zero_padding && str::len(s) > 0u {
-            let head = str::shift_char(s);
+            let head = str::shift_char(&mut s);
             if head == '+' || head == '-' || head == ' ' {
                 let headstr = str::from_chars(vec::from_elem(1u, head));
                 return headstr + padstr + s;
             }
             else {
-                str::unshift_char(s, head);
+                str::unshift_char(&mut s, head);
             }
         }
         return padstr + s;
@@ -500,9 +500,9 @@ enum Ty { TyDefault, TyBits, TyHexUpper, TyHexLower, TyOctal, }
         let mut s : ~str = int_to_str_prec(i, radix, prec);
         if 0 <= i {
             if have_flag(cv.flags, flag_sign_always) {
-                unsafe { str::unshift_char(s, '+') };
+                unsafe { str::unshift_char(&mut s, '+') };
             } else if have_flag(cv.flags, flag_space_for_sign) {
-                unsafe { str::unshift_char(s, ' ') };
+                unsafe { str::unshift_char(&mut s, ' ') };
             }
         }
         return unsafe { pad(cv, s, PadSigned) };
@@ -670,13 +670,13 @@ fn pad(cv: Conv, &s: ~str, mode: PadMode) -> ~str {
         // instead.
 
         if signed && zero_padding && str::len(s) > 0u {
-            let head = str::shift_char(s);
+            let head = str::shift_char(&mut s);
             if head == '+' || head == '-' || head == ' ' {
                 let headstr = str::from_chars(vec::from_elem(1u, head));
                 return headstr + padstr + s;
             }
             else {
-                str::unshift_char(s, head);
+                str::unshift_char(&mut s, head);
             }
         }
         return padstr + s;
diff --git a/src/libcore/str.rs b/src/libcore/str.rs
index 35c2fde36b4b1fd60bca7c048a414f2ebc25ad95..e9a72ef2ba064678ac1e9ed3d83d4b81ec99b5f4 100644
--- a/src/libcore/str.rs
+++ b/src/libcore/str.rs
@@ -7,9 +7,13 @@
  * some heavy-duty uses, try std::rope.
  */
 
+#[warn(deprecated_mode)];
+#[warn(deprecated_pattern)];
+
 use cmp::{Eq, Ord};
 use libc::size_t;
 use io::WriterUtil;
+use to_str::ToStr;
 
 export
    // Creating a string
@@ -154,7 +158,7 @@
 }
 
 /// Appends a character at the end of a string
-fn push_char(&s: ~str, ch: char) {
+fn push_char(s: &const ~str, ch: char) {
     unsafe {
         let code = ch as uint;
         let nb = if code < max_one_b { 1u }
@@ -163,11 +167,11 @@ fn push_char(&s: ~str, ch: char) {
         else if code < max_four_b { 4u }
         else if code < max_five_b { 5u }
         else { 6u };
-        let len = len(s);
+        let len = len(*s);
         let new_len = len + nb;
         reserve_at_least(s, new_len);
         let off = len;
-        do as_buf(s) |buf, _len| {
+        do as_buf(*s) |buf, _len| {
             let buf: *mut u8 = ::cast::reinterpret_cast(&buf);
             if nb == 1u {
                 *ptr::mut_offset(buf, off) =
@@ -227,7 +231,7 @@ fn push_char(&s: ~str, ch: char) {
 /// Convert a char to a string
 pure fn from_char(ch: char) -> ~str {
     let mut buf = ~"";
-    unsafe { push_char(buf, ch); }
+    unsafe { push_char(&mut buf, ch); }
     move buf
 }
 
@@ -235,9 +239,9 @@ fn push_char(&s: ~str, ch: char) {
 pure fn from_chars(chs: &[char]) -> ~str {
     let mut buf = ~"";
     unsafe {
-        reserve(buf, chs.len());
+        reserve(&mut buf, chs.len());
         for vec::each(chs) |ch| {
-            push_char(buf, *ch);
+            push_char(&mut buf, *ch);
         }
     }
     move buf
@@ -245,12 +249,12 @@ fn push_char(&s: ~str, ch: char) {
 
 /// Appends a string slice to the back of a string, without overallocating
 #[inline(always)]
-fn push_str_no_overallocate(&lhs: ~str, rhs: &str) {
+fn push_str_no_overallocate(lhs: &const ~str, rhs: &str) {
     unsafe {
         let llen = lhs.len();
         let rlen = rhs.len();
         reserve(lhs, llen + rlen);
-        do as_buf(lhs) |lbuf, _llen| {
+        do as_buf(*lhs) |lbuf, _llen| {
             do as_buf(rhs) |rbuf, _rlen| {
                 let dst = ptr::offset(lbuf, llen);
                 let dst = ::cast::transmute_mut_unsafe(dst);
@@ -262,12 +266,12 @@ fn push_str_no_overallocate(&lhs: ~str, rhs: &str) {
 }
 /// Appends a string slice to the back of a string
 #[inline(always)]
-fn push_str(&lhs: ~str, rhs: &str) {
+fn push_str(lhs: &const ~str, rhs: &str) {
     unsafe {
         let llen = lhs.len();
         let rlen = rhs.len();
         reserve_at_least(lhs, llen + rlen);
-        do as_buf(lhs) |lbuf, _llen| {
+        do as_buf(*lhs) |lbuf, _llen| {
             do as_buf(rhs) |rbuf, _rlen| {
                 let dst = ptr::offset(lbuf, llen);
                 let dst = ::cast::transmute_mut_unsafe(dst);
@@ -283,7 +287,7 @@ fn push_str(&lhs: ~str, rhs: &str) {
 pure fn append(+lhs: ~str, rhs: &str) -> ~str {
     let mut v <- lhs;
     unsafe {
-        push_str_no_overallocate(v, rhs);
+        push_str_no_overallocate(&mut v, rhs);
     }
     move v
 }
@@ -293,7 +297,7 @@ fn push_str(&lhs: ~str, rhs: &str) {
 pure fn concat(v: &[~str]) -> ~str {
     let mut s: ~str = ~"";
     for vec::each(v) |ss| {
-        unsafe { push_str(s, *ss) };
+        unsafe { push_str(&mut s, *ss) };
     }
     move s
 }
@@ -302,8 +306,8 @@ fn push_str(&lhs: ~str, rhs: &str) {
 pure fn connect(v: &[~str], sep: &str) -> ~str {
     let mut s = ~"", first = true;
     for vec::each(v) |ss| {
-        if first { first = false; } else { unsafe { push_str(s, sep); } }
-        unsafe { push_str(s, *ss) };
+        if first { first = false; } else { unsafe { push_str(&mut s, sep); } }
+        unsafe { push_str(&mut s, *ss) };
     }
     move s
 }
@@ -319,10 +323,10 @@ fn push_str(&lhs: ~str, rhs: &str) {
  *
  * If the string does not contain any characters
  */
-fn pop_char(&s: ~str) -> char {
-    let end = len(s);
+fn pop_char(s: &const ~str) -> char {
+    let end = len(*s);
     assert end > 0u;
-    let {ch, prev} = char_range_at_reverse(s, end);
+    let {ch, prev} = char_range_at_reverse(*s, end);
     unsafe { raw::set_len(s, prev); }
     return ch;
 }
@@ -334,9 +338,9 @@ fn pop_char(&s: ~str) -> char {
  *
  * If the string does not contain any characters
  */
-fn shift_char(&s: ~str) -> char {
-    let {ch, next} = char_range_at(s, 0u);
-    s = unsafe { raw::slice_bytes(s, next, len(s)) };
+fn shift_char(s: &mut ~str) -> char {
+    let {ch, next} = char_range_at(*s, 0u);
+    *s = unsafe { raw::slice_bytes(*s, next, len(*s)) };
     return ch;
 }
 
@@ -357,7 +361,9 @@ fn view_shift_char(s: &a/str) -> (char, &a/str) {
 }
 
 /// Prepend a char to a string
-fn unshift_char(&s: ~str, ch: char) { s = from_char(ch) + s; }
+fn unshift_char(s: &mut ~str, ch: char) {
+    *s = from_char(ch) + *s;
+}
 
 /**
  * Returns a string with leading `chars_to_trim` removed.
@@ -666,7 +672,7 @@ fn view_shift_char(s: &a/str) -> (char, &a/str) {
         let l = len(s);
         let mut cp = copy s;
         if l > 0u && s[l - 1u] == '\r' as u8 {
-            unsafe { raw::set_len(cp, l - 1u); }
+            unsafe { raw::set_len(&mut cp, l - 1u); }
         }
         move cp
     })
@@ -707,8 +713,12 @@ fn view_shift_char(s: &a/str) -> (char, &a/str) {
 pure fn replace(s: &str, from: &str, to: &str) -> ~str {
     let mut result = ~"", first = true;
     do iter_between_matches(s, from) |start, end| {
-        if first { first = false; } else { unsafe {push_str(result, to); }}
-        unsafe { push_str(result, raw::slice_bytes(s, start, end)); }
+        if first {
+            first = false;
+        } else {
+            unsafe { push_str(&mut result, to); }
+        }
+        unsafe { push_str(&mut result, raw::slice_bytes(s, start, end)); }
     }
     move result
 }
@@ -950,9 +960,9 @@ impl @str : Ord {
 pure fn map(ss: &str, ff: fn(char) -> char) -> ~str {
     let mut result = ~"";
     unsafe {
-        reserve(result, len(ss));
+        reserve(&mut result, len(ss));
         for chars_each(ss) |cc| {
-            str::push_char(result, ff(cc));
+            str::push_char(&mut result, ff(cc));
         }
     }
     move result
@@ -1638,8 +1648,8 @@ fn is_alphanumeric(s: &str) -> bool {
 pure fn from_utf16(v: &[u16]) -> ~str {
     let mut buf = ~"";
     unsafe {
-        reserve(buf, vec::len(v));
-        utf16_chars(v, |ch| push_char(buf, ch));
+        reserve(&mut buf, vec::len(v));
+        utf16_chars(v, |ch| push_char(&mut buf, ch));
     }
     move buf
 }
@@ -1890,9 +1900,9 @@ fn is_alphanumeric(s: &str) -> bool {
  * let i = str::as_bytes("Hello World") { |bytes| vec::len(bytes) };
  * ~~~
  */
-pure fn as_bytes<T>(s: ~str, f: fn(~[u8]) -> T) -> T {
+pure fn as_bytes<T>(s: &const ~str, f: fn(~[u8]) -> T) -> T {
     unsafe {
-        let v: *~[u8] = ::cast::reinterpret_cast(&ptr::addr_of(s));
+        let v: *~[u8] = cast::transmute(copy s);
         f(*v)
     }
 }
@@ -1971,9 +1981,9 @@ fn is_alphanumeric(s: &str) -> bool {
  * * s - A string
  * * n - The number of bytes to reserve space for
  */
-fn reserve(&s: ~str, n: uint) {
+fn reserve(s: &const ~str, n: uint) {
     unsafe {
-        let v: *mut ~[u8] = ::cast::reinterpret_cast(&ptr::addr_of(s));
+        let v: *mut ~[u8] = cast::transmute(copy s);
         vec::reserve(*v, n + 1);
     }
 }
@@ -1998,7 +2008,7 @@ fn reserve(&s: ~str, n: uint) {
  * * s - A string
  * * n - The number of bytes to reserve space for
  */
-fn reserve_at_least(&s: ~str, n: uint) {
+fn reserve_at_least(s: &const ~str, n: uint) {
     reserve(s, uint::next_power_of_two(n + 1u) - 1u)
 }
 
@@ -2006,7 +2016,7 @@ fn reserve_at_least(&s: ~str, n: uint) {
  * Returns the number of single-byte characters the string can hold without
  * reallocating
  */
-pure fn capacity(&&s: ~str) -> uint {
+pure fn capacity(s: &const ~str) -> uint {
     do as_bytes(s) |buf| {
         let vcap = vec::capacity(buf);
         assert vcap > 0u;
@@ -2018,9 +2028,9 @@ fn reserve_at_least(&s: ~str, n: uint) {
 pure fn escape_default(s: &str) -> ~str {
     let mut out: ~str = ~"";
     unsafe {
-        reserve_at_least(out, str::len(s));
+        reserve_at_least(&mut out, str::len(s));
         for chars_each(s) |c| {
-            push_str(out, char::escape_default(c));
+            push_str(&mut out, char::escape_default(c));
         }
     }
     move out
@@ -2030,9 +2040,9 @@ fn reserve_at_least(&s: ~str, n: uint) {
 pure fn escape_unicode(s: &str) -> ~str {
     let mut out: ~str = ~"";
     unsafe {
-        reserve_at_least(out, str::len(s));
+        reserve_at_least(&mut out, str::len(s));
         for chars_each(s) |c| {
-            push_str(out, char::escape_unicode(c));
+            push_str(&mut out, char::escape_unicode(c));
         }
     }
     move out
@@ -2159,9 +2169,9 @@ unsafe fn view_bytes(s: &str, begin: uint, end: uint) -> &str {
     }
 
     /// Appends a byte to a string. (Not UTF-8 safe).
-    unsafe fn push_byte(&s: ~str, b: u8) {
+    unsafe fn push_byte(s: &const ~str, b: u8) {
         reserve_at_least(s, s.len() + 1);
-        do as_buf(s) |buf, len| {
+        do as_buf(*s) |buf, len| {
             let buf: *mut u8 = ::cast::reinterpret_cast(&buf);
             *ptr::mut_offset(buf, len) = b;
         }
@@ -2169,14 +2179,14 @@ unsafe fn push_byte(&s: ~str, b: u8) {
     }
 
     /// Appends a vector of bytes to a string. (Not UTF-8 safe).
-    unsafe fn push_bytes(&s: ~str, bytes: ~[u8]) {
+    unsafe fn push_bytes(s: &const ~str, bytes: &[u8]) {
         reserve_at_least(s, s.len() + bytes.len());
         for vec::each(bytes) |byte| { push_byte(s, *byte); }
     }
 
     /// Removes the last byte from a string and returns it. (Not UTF-8 safe).
-    unsafe fn pop_byte(&s: ~str) -> u8 {
-        let len = len(s);
+    unsafe fn pop_byte(s: &const ~str) -> u8 {
+        let len = len(*s);
         assert (len > 0u);
         let b = s[len - 1u];
         unsafe { set_len(s, len - 1u) };
@@ -2184,17 +2194,18 @@ unsafe fn pop_byte(&s: ~str) -> u8 {
     }
 
     /// Removes the first byte from a string and returns it. (Not UTF-8 safe).
-    unsafe fn shift_byte(&s: ~str) -> u8 {
-        let len = len(s);
+    unsafe fn shift_byte(s: &mut ~str) -> u8 {
+        let len = len(*s);
         assert (len > 0u);
         let b = s[0];
-        s = unsafe { raw::slice_bytes(s, 1u, len) };
+        *s = unsafe { raw::slice_bytes(*s, 1u, len) };
         return b;
     }
 
     /// Sets the length of the string and adds the null terminator
-    unsafe fn set_len(&v: ~str, new_len: uint) {
-        let repr: *vec::raw::VecRepr = ::cast::reinterpret_cast(&v);
+    unsafe fn set_len(v: &const ~str, new_len: uint) {
+        let v: **vec::raw::VecRepr = cast::transmute(copy v);
+        let repr: *vec::raw::VecRepr = *v;
         (*repr).unboxed.fill = new_len + 1u;
         let null = ptr::mut_offset(ptr::mut_addr_of((*repr).unboxed.data),
                                    new_len);
@@ -2457,7 +2468,7 @@ fn test_rfind_char() {
     #[test]
     fn test_pop_char() {
         let mut data = ~"ประเทศไทย中华";
-        let cc = pop_char(data);
+        let cc = pop_char(&mut data);
         assert ~"ประเทศไทย中" == data;
         assert '华' == cc;
     }
@@ -2465,7 +2476,7 @@ fn test_pop_char() {
     #[test]
     fn test_pop_char_2() {
         let mut data2 = ~"华";
-        let cc2 = pop_char(data2);
+        let cc2 = pop_char(&mut data2);
         assert ~"" == data2;
         assert '华' == cc2;
     }
@@ -2475,12 +2486,12 @@ fn test_pop_char_2() {
     #[ignore(cfg(windows))]
     fn test_pop_char_fail() {
         let mut data = ~"";
-        let _cc3 = pop_char(data);
+        let _cc3 = pop_char(&mut data);
     }
 
     #[test]
     fn test_split_char() {
-        fn t(s: ~str, c: char, u: ~[~str]) {
+        fn t(s: &str, c: char, u: &[~str]) {
             log(debug, ~"split_byte: " + s);
             let v = split_char(s, c);
             debug!("split_byte to: %?", v);
@@ -2509,7 +2520,7 @@ fn test_split_char_2() {
 
     #[test]
     fn test_splitn_char() {
-        fn t(s: ~str, c: char, n: uint, u: ~[~str]) {
+        fn t(s: &str, c: char, n: uint, u: &[~str]) {
             log(debug, ~"splitn_byte: " + s);
             let v = splitn_char(s, c, n);
             debug!("split_byte to: %?", v);
@@ -2560,9 +2571,10 @@ fn test_splitn_char_3() {
 
     #[test]
     fn test_split_str() {
-        fn t(s: ~str, sep: &a/str, i: int, k: ~str) {
+        fn t(s: &str, sep: &a/str, i: int, k: &str) {
+            fn borrow(x: &a/str) -> &a/str { x }
             let v = split_str(s, sep);
-            assert v[i] == k;
+            assert borrow(v[i]) == k;
         }
 
         t(~"--1233345--", ~"12345", 0, ~"--1233345--");
@@ -2689,8 +2701,8 @@ fn test_find_str_between() {
 
     #[test]
     fn test_substr() {
-        fn t(a: ~str, b: ~str, start: int) {
-            assert substr(a, start as uint, len(b)) == b;
+        fn t(a: &str, b: &str, start: int) {
+            assert substr(a, start as uint, len(b)) == b.to_str();
         }
         t(~"hello", ~"llo", 2);
         t(~"hello", ~"el", 1);
@@ -2699,7 +2711,9 @@ fn t(a: ~str, b: ~str, start: int) {
 
     #[test]
     fn test_concat() {
-        fn t(v: ~[~str], s: ~str) { assert concat(v) == s; }
+        fn t(v: &[~str], s: &str) {
+            assert concat(v) == s.to_str();
+        }
         t(~[~"you", ~"know", ~"I'm", ~"no", ~"good"], ~"youknowI'mnogood");
         let v: ~[~str] = ~[];
         t(v, ~"");
@@ -2708,8 +2722,8 @@ fn test_concat() {
 
     #[test]
     fn test_connect() {
-        fn t(v: ~[~str], sep: ~str, s: ~str) {
-            assert connect(v, sep) == s;
+        fn t(v: &[~str], sep: &str, s: &str) {
+            assert connect(v, sep) == s.to_str();
         }
         t(~[~"you", ~"know", ~"I'm", ~"no", ~"good"],
           ~" ", ~"you know I'm no good");
@@ -2746,13 +2760,13 @@ fn test_unsafe_slice() {
             fn a_million_letter_a() -> ~str {
                 let mut i = 0;
                 let mut rs = ~"";
-                while i < 100000 { push_str(rs, ~"aaaaaaaaaa"); i += 1; }
+                while i < 100000 { push_str(&mut rs, ~"aaaaaaaaaa"); i += 1; }
                 return rs;
             }
             fn half_a_million_letter_a() -> ~str {
                 let mut i = 0;
                 let mut rs = ~"";
-                while i < 100000 { push_str(rs, ~"aaaaa"); i += 1; }
+                while i < 100000 { push_str(&mut rs, ~"aaaaa"); i += 1; }
                 return rs;
             }
             assert half_a_million_letter_a() ==
@@ -2856,13 +2870,16 @@ fn test_slice() {
         fn a_million_letter_X() -> ~str {
             let mut i = 0;
             let mut rs = ~"";
-            while i < 100000 { push_str(rs, ~"华华华华华华华华华华"); i += 1; }
+            while i < 100000 {
+                push_str(&mut rs, ~"华华华华华华华华华华");
+                i += 1;
+            }
             return rs;
         }
         fn half_a_million_letter_X() -> ~str {
             let mut i = 0;
             let mut rs = ~"";
-            while i < 100000 { push_str(rs, ~"华华华华华"); i += 1; }
+            while i < 100000 { push_str(&mut rs, ~"华华华华华"); i += 1; }
             return rs;
         }
         assert half_a_million_letter_X() ==
@@ -2975,7 +2992,7 @@ fn test_is_ascii() {
     #[test]
     fn test_shift_byte() {
         let mut s = ~"ABC";
-        let b = unsafe { raw::shift_byte(s) };
+        let b = unsafe { raw::shift_byte(&mut s) };
         assert (s == ~"BC");
         assert (b == 65u8);
     }
@@ -2983,7 +3000,7 @@ fn test_shift_byte() {
     #[test]
     fn test_pop_byte() {
         let mut s = ~"ABC";
-        let b = unsafe { raw::pop_byte(s) };
+        let b = unsafe { raw::pop_byte(&mut s) };
         assert (s == ~"AB");
         assert (b == 67u8);
     }
@@ -3045,7 +3062,7 @@ fn test_from_buf() {
     #[should_fail]
     fn test_as_bytes_fail() {
         // Don't double free
-        as_bytes::<()>(~"", |_bytes| fail );
+        as_bytes::<()>(&~"", |_bytes| fail );
     }
 
     #[test]
diff --git a/src/libcore/to_str.rs b/src/libcore/to_str.rs
index a9e7bd74b2838bde88316b520df53434a7a856b5..f279945a161080c9c1670579536392ffb80aec2c 100644
--- a/src/libcore/to_str.rs
+++ b/src/libcore/to_str.rs
@@ -83,10 +83,10 @@ fn to_str() -> ~str {
         let mut acc = ~"[", first = true;
         for vec::each(self) |elt| {
             if first { first = false; }
-            else { str::push_str(acc, ~", "); }
-            str::push_str(acc, elt.to_str());
+            else { str::push_str(&mut acc, ~", "); }
+            str::push_str(&mut acc, elt.to_str());
         }
-        str::push_char(acc, ']');
+        str::push_char(&mut acc, ']');
         move acc
     }
 }
diff --git a/src/libstd/base64.rs b/src/libstd/base64.rs
index d01aaab6723ea8f434cbdc5961f20a0b201aa729..402b4241cb3ca9c209cfb03e8d2828666a149182 100644
--- a/src/libstd/base64.rs
+++ b/src/libstd/base64.rs
@@ -14,7 +14,7 @@ fn to_base64() -> ~str {
 
         let len = self.len();
         let mut s = ~"";
-        str::reserve(s, ((len + 3u) / 4u) * 3u);
+        str::reserve(&mut s, ((len + 3u) / 4u) * 3u);
 
         let mut i = 0u;
 
@@ -24,10 +24,10 @@ fn to_base64() -> ~str {
                     (self[i + 2u] as uint);
 
             // This 24-bit number gets separated into four 6-bit numbers.
-            str::push_char(s, chars[(n >> 18u) & 63u]);
-            str::push_char(s, chars[(n >> 12u) & 63u]);
-            str::push_char(s, chars[(n >> 6u) & 63u]);
-            str::push_char(s, chars[n & 63u]);
+            str::push_char(&mut s, chars[(n >> 18u) & 63u]);
+            str::push_char(&mut s, chars[(n >> 12u) & 63u]);
+            str::push_char(&mut s, chars[(n >> 6u) & 63u]);
+            str::push_char(&mut s, chars[n & 63u]);
 
             i += 3u;
         }
@@ -38,17 +38,17 @@ fn to_base64() -> ~str {
           0 => (),
           1 => {
             let n = (self[i] as uint) << 16u;
-            str::push_char(s, chars[(n >> 18u) & 63u]);
-            str::push_char(s, chars[(n >> 12u) & 63u]);
-            str::push_char(s, '=');
-            str::push_char(s, '=');
+            str::push_char(&mut s, chars[(n >> 18u) & 63u]);
+            str::push_char(&mut s, chars[(n >> 12u) & 63u]);
+            str::push_char(&mut s, '=');
+            str::push_char(&mut s, '=');
           }
           2 => {
             let n = (self[i] as uint) << 16u | (self[i + 1u] as uint) << 8u;
-            str::push_char(s, chars[(n >> 18u) & 63u]);
-            str::push_char(s, chars[(n >> 12u) & 63u]);
-            str::push_char(s, chars[(n >> 6u) & 63u]);
-            str::push_char(s, '=');
+            str::push_char(&mut s, chars[(n >> 18u) & 63u]);
+            str::push_char(&mut s, chars[(n >> 12u) & 63u]);
+            str::push_char(&mut s, chars[(n >> 6u) & 63u]);
+            str::push_char(&mut s, '=');
           }
           _ => fail ~"Algebra is broken, please alert the math police"
         }
diff --git a/src/libstd/json.rs b/src/libstd/json.rs
index 4d458db482ba1ccab2d181c2c950be61ab8c1bee..6b80aa716a07739ad0fa466dc0f50fb42a162f15 100644
--- a/src/libstd/json.rs
+++ b/src/libstd/json.rs
@@ -92,7 +92,7 @@ fn to_writer(wr: io::Writer, j: Json) {
 fn to_writer_pretty(wr: io::Writer, j: Json, indent: uint) {
     fn spaces(n: uint) -> ~str {
         let mut ss = ~"";
-        for n.times { str::push_str(ss, " "); }
+        for n.times { str::push_str(&mut ss, " "); }
         return ss;
     }
 
@@ -428,14 +428,14 @@ fn parse_str() -> Result<@~str, Error> {
 
             if (escape) {
                 match self.ch {
-                  '"' => str::push_char(res, '"'),
-                  '\\' => str::push_char(res, '\\'),
-                  '/' => str::push_char(res, '/'),
-                  'b' => str::push_char(res, '\x08'),
-                  'f' => str::push_char(res, '\x0c'),
-                  'n' => str::push_char(res, '\n'),
-                  'r' => str::push_char(res, '\r'),
-                  't' => str::push_char(res, '\t'),
+                  '"' => str::push_char(&mut res, '"'),
+                  '\\' => str::push_char(&mut res, '\\'),
+                  '/' => str::push_char(&mut res, '/'),
+                  'b' => str::push_char(&mut res, '\x08'),
+                  'f' => str::push_char(&mut res, '\x0c'),
+                  'n' => str::push_char(&mut res, '\n'),
+                  'r' => str::push_char(&mut res, '\r'),
+                  't' => str::push_char(&mut res, '\t'),
                   'u' => {
                       // Parse \u1234.
                       let mut i = 0u;
@@ -464,7 +464,7 @@ fn parse_str() -> Result<@~str, Error> {
                             ~"invalid \\u escape (not four digits)");
                       }
 
-                      str::push_char(res, n as char);
+                      str::push_char(&mut res, n as char);
                   }
                   _ => return self.error(~"invalid escape")
                 }
@@ -476,7 +476,7 @@ fn parse_str() -> Result<@~str, Error> {
                     self.bump();
                     return Ok(@res);
                 }
-                str::push_char(res, self.ch);
+                str::push_char(&mut res, self.ch);
             }
         }
 
diff --git a/src/libstd/net_url.rs b/src/libstd/net_url.rs
index 22fe049d03b90da59f90b3604991cb8bc702414e..a824f5ab11740e4ba23b8aae55059d73e398385c 100644
--- a/src/libstd/net_url.rs
+++ b/src/libstd/net_url.rs
@@ -61,7 +61,7 @@ fn encode_inner(s: &str, full_url: bool) -> ~str {
               'a' .. 'z' |
               '0' .. '9' |
               '-' | '.' | '_' | '~' => {
-                str::push_char(out, ch);
+                str::push_char(&mut out, ch);
               }
               _ => {
                   if full_url {
@@ -72,7 +72,7 @@ fn encode_inner(s: &str, full_url: bool) -> ~str {
                       // sub-delims:
                       '!' | '$' | '&' | '"' | '(' | ')' | '*' |
                       '+' | ',' | ';' | '=' => {
-                        str::push_char(out, ch);
+                        str::push_char(&mut out, ch);
                       }
 
                       _ => out += #fmt("%%%X", ch as uint)
@@ -127,18 +127,18 @@ fn decode_inner(s: &str, full_url: bool) -> ~str {
                       // sub-delims:
                       '!' | '$' | '&' | '"' | '(' | ')' | '*' |
                       '+' | ',' | ';' | '=' => {
-                        str::push_char(out, '%');
-                        str::push_char(out, bytes[0u] as char);
-                        str::push_char(out, bytes[1u] as char);
+                        str::push_char(&mut out, '%');
+                        str::push_char(&mut out, bytes[0u] as char);
+                        str::push_char(&mut out, bytes[1u] as char);
                       }
 
-                      ch => str::push_char(out, ch)
+                      ch => str::push_char(&mut out, ch)
                     }
                 } else {
-                      str::push_char(out, ch);
+                      str::push_char(&mut out, ch);
                 }
               }
-              ch => str::push_char(out, ch)
+              ch => str::push_char(&mut out, ch)
             }
         }
 
@@ -170,9 +170,9 @@ fn encode_plus(s: &str) -> ~str {
             let ch = rdr.read_byte() as char;
             match ch {
               'A' .. 'Z' | 'a' .. 'z' | '0' .. '9' | '_' | '.' | '-' => {
-                str::push_char(out, ch);
+                str::push_char(&mut out, ch);
               }
-              ' ' => str::push_char(out, '+'),
+              ' ' => str::push_char(&mut out, '+'),
               _ => out += #fmt("%%%X", ch as uint)
             }
         }
@@ -195,7 +195,7 @@ fn encode_form_urlencoded(m: HashMap<~str, @DVec<@~str>>) -> ~str {
             if first {
                 first = false;
             } else {
-                str::push_char(out, '&');
+                str::push_char(&mut out, '&');
                 first = false;
             }
 
@@ -248,9 +248,9 @@ fn decode_form_urlencoded(s: ~[u8]) ->
                 };
 
                 if parsing_key {
-                    str::push_char(key, ch)
+                    str::push_char(&mut key, ch)
                 } else {
-                    str::push_char(value, ch)
+                    str::push_char(&mut value, ch)
                 }
               }
             }
diff --git a/src/libstd/sha1.rs b/src/libstd/sha1.rs
index 40c9589a651ecd1ad4e1921347972bf95d5678e9..a40db2c1f1fc2e9b573e65ed3f742e2ad97a0dc3 100644
--- a/src/libstd/sha1.rs
+++ b/src/libstd/sha1.rs
@@ -271,7 +271,10 @@ fn test() unsafe {
         fn a_million_letter_a() -> ~str {
             let mut i = 0;
             let mut rs = ~"";
-            while i < 100000 { str::push_str(rs, ~"aaaaaaaaaa"); i += 1; }
+            while i < 100000 {
+                str::push_str(&mut rs, ~"aaaaaaaaaa");
+                i += 1;
+            }
             return rs;
         }
         // Test messages from FIPS 180-1
diff --git a/src/libstd/time.rs b/src/libstd/time.rs
index 3dca5540b8296c9b0f925db47bd9b714fd721987..bc3f8162c4d8221b95874780396f0ffdd4a37eed 100644
--- a/src/libstd/time.rs
+++ b/src/libstd/time.rs
@@ -800,7 +800,7 @@ fn parse_type(ch: char, tm: &Tm) -> ~str {
         while !rdr.eof() {
             match rdr.read_char() {
                 '%' => buf += parse_type(rdr.read_char(), &tm),
-                ch => str::push_char(buf, ch)
+                ch => str::push_char(&mut buf, ch)
             }
         }
     }
diff --git a/src/libsyntax/diagnostic.rs b/src/libsyntax/diagnostic.rs
index cbe9097bd7dbb261993827a0c955cc29dadd92f6..5b72bf61fdeb53579bfc8885d567edf57f79a9f5 100644
--- a/src/libsyntax/diagnostic.rs
+++ b/src/libsyntax/diagnostic.rs
@@ -255,14 +255,14 @@ fn highlight_lines(cm: codemap::codemap, sp: span,
         // indent past |name:## | and the 0-offset column location
         let mut left = str::len(fm.name) + digits + lo.col + 3u;
         let mut s = ~"";
-        while left > 0u { str::push_char(s, ' '); left -= 1u; }
+        while left > 0u { str::push_char(&mut s, ' '); left -= 1u; }
 
         s += ~"^";
         let hi = codemap::lookup_char_pos(cm, sp.hi);
         if hi.col != lo.col {
             // the ^ already takes up one space
             let mut width = hi.col - lo.col - 1u;
-            while width > 0u { str::push_char(s, '~'); width -= 1u; }
+            while width > 0u { str::push_char(&mut s, '~'); width -= 1u; }
         }
         io::stderr().write_str(s + ~"\n");
     }
diff --git a/src/libsyntax/ext/qquote.rs b/src/libsyntax/ext/qquote.rs
index da37e44b58c63105601a07fd9d266edd86e10314..83899b58d662e18af45b86201a89bf37956456f5 100644
--- a/src/libsyntax/ext/qquote.rs
+++ b/src/libsyntax/ext/qquote.rs
@@ -236,11 +236,11 @@ fn finish<T: qq_helper>
             str2 += repl;
         }
         match copy state {
-          active => str::push_char(str2, ch),
+          active => str::push_char(&mut str2, ch),
           skip(1u) => state = blank,
           skip(sk) => state = skip (sk-1u),
-          blank if is_space(ch) => str::push_char(str2, ch),
-          blank => str::push_char(str2, ' ')
+          blank if is_space(ch) => str::push_char(&mut str2, ch),
+          blank => str::push_char(&mut str2, ' ')
         }
         i += 1u;
         if (j < g_len && i == cx.gather[j].hi) {
diff --git a/src/libsyntax/parse/comments.rs b/src/libsyntax/parse/comments.rs
index 214b9e3fbbd60c8a7fe836a888a1f85c01ec6084..7f1ec1093709fb66769be4a8c8210de5f62b7bb1 100644
--- a/src/libsyntax/parse/comments.rs
+++ b/src/libsyntax/parse/comments.rs
@@ -117,7 +117,7 @@ fn block_trim(lines: ~[~str], chars: ~str, max: Option<uint>) -> ~[~str] {
 fn read_to_eol(rdr: string_reader) -> ~str {
     let mut val = ~"";
     while rdr.curr != '\n' && !is_eof(rdr) {
-        str::push_char(val, rdr.curr);
+        str::push_char(&mut val, rdr.curr);
         bump(rdr);
     }
     if rdr.curr == '\n' { bump(rdr); }
@@ -242,7 +242,7 @@ fn read_block_comment(rdr: string_reader, code_to_the_left: bool,
             curr_line = ~"";
             bump(rdr);
         } else {
-            str::push_char(curr_line, rdr.curr);
+            str::push_char(&mut curr_line, rdr.curr);
             if rdr.curr == '/' && nextch(rdr) == '*' {
                 bump(rdr);
                 bump(rdr);
diff --git a/src/libsyntax/parse/lexer.rs b/src/libsyntax/parse/lexer.rs
index 2103af39bae71f0778347c400aad27b8aae75f49..c32aaa3d474ce605e1fb73d90ca8d5be878066c5 100644
--- a/src/libsyntax/parse/lexer.rs
+++ b/src/libsyntax/parse/lexer.rs
@@ -214,7 +214,7 @@ fn consume_any_line_comment(rdr: string_reader)
                 let start_chpos = rdr.chpos - 2u;
                 let mut acc = ~"//";
                 while rdr.curr != '\n' && !is_eof(rdr) {
-                    str::push_char(acc, rdr.curr);
+                    str::push_char(&mut acc, rdr.curr);
                     bump(rdr);
                 }
                 return Some({
@@ -253,7 +253,7 @@ fn consume_block_comment(rdr: string_reader)
         let start_chpos = rdr.chpos - 2u;
         let mut acc = ~"/*";
         while !(rdr.curr == '*' && nextch(rdr) == '/') && !is_eof(rdr) {
-            str::push_char(acc, rdr.curr);
+            str::push_char(&mut acc, rdr.curr);
             bump(rdr);
         }
         if is_eof(rdr) {
@@ -288,11 +288,11 @@ fn scan_exponent(rdr: string_reader) -> Option<~str> {
     let mut c = rdr.curr;
     let mut rslt = ~"";
     if c == 'e' || c == 'E' {
-        str::push_char(rslt, c);
+        str::push_char(&mut rslt, c);
         bump(rdr);
         c = rdr.curr;
         if c == '-' || c == '+' {
-            str::push_char(rslt, c);
+            str::push_char(&mut rslt, c);
             bump(rdr);
         }
         let exponent = scan_digits(rdr, 10u);
@@ -309,7 +309,7 @@ fn scan_digits(rdr: string_reader, radix: uint) -> ~str {
         if c == '_' { bump(rdr); loop; }
         match char::to_digit(c, radix) {
           Some(_) => {
-            str::push_char(rslt, c);
+            str::push_char(&mut rslt, c);
             bump(rdr);
           }
           _ => return rslt
@@ -447,7 +447,7 @@ fn next_token_inner(rdr: string_reader) -> token::token {
             || (c >= '0' && c <= '9')
             || c == '_'
             || (c > 'z' && char::is_XID_continue(c)) {
-            str::push_char(accum_str, c);
+            str::push_char(&mut accum_str, c);
             bump(rdr);
             c = rdr.curr;
         }
@@ -599,28 +599,31 @@ fn binop(rdr: string_reader, op: token::binop) -> token::token {
                 let escaped = rdr.curr;
                 bump(rdr);
                 match escaped {
-                  'n' => str::push_char(accum_str, '\n'),
-                  'r' => str::push_char(accum_str, '\r'),
-                  't' => str::push_char(accum_str, '\t'),
-                  '\\' => str::push_char(accum_str, '\\'),
-                  '\'' => str::push_char(accum_str, '\''),
-                  '"' => str::push_char(accum_str, '"'),
+                  'n' => str::push_char(&mut accum_str, '\n'),
+                  'r' => str::push_char(&mut accum_str, '\r'),
+                  't' => str::push_char(&mut accum_str, '\t'),
+                  '\\' => str::push_char(&mut accum_str, '\\'),
+                  '\'' => str::push_char(&mut accum_str, '\''),
+                  '"' => str::push_char(&mut accum_str, '"'),
                   '\n' => consume_whitespace(rdr),
                   'x' => {
-                    str::push_char(accum_str, scan_numeric_escape(rdr, 2u));
+                    str::push_char(&mut accum_str,
+                                   scan_numeric_escape(rdr, 2u));
                   }
                   'u' => {
-                    str::push_char(accum_str, scan_numeric_escape(rdr, 4u));
+                    str::push_char(&mut accum_str,
+                                   scan_numeric_escape(rdr, 4u));
                   }
                   'U' => {
-                    str::push_char(accum_str, scan_numeric_escape(rdr, 8u));
+                    str::push_char(&mut accum_str,
+                                   scan_numeric_escape(rdr, 8u));
                   }
                   c2 => {
                     rdr.fatal(fmt!("unknown string escape: %d", c2 as int));
                   }
                 }
               }
-              _ => str::push_char(accum_str, ch)
+              _ => str::push_char(&mut accum_str, ch)
             }
         }
         bump(rdr);
diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index 561e2ecd0b4b57f54d481f77b432ecc05097235e..e99e35b596cf76fd154ee3ab252f186c3adae703 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -2093,13 +2093,13 @@ fn fn_header_info_to_str(opt_sty: Option<ast::self_ty_>,
     match opt_purity {
       Some(ast::impure_fn) => { }
       Some(purity) => {
-        str::push_str(s, purity_to_str(purity));
-        str::push_char(s, ' ');
+        str::push_str(&mut s, purity_to_str(purity));
+        str::push_char(&mut s, ' ');
       }
       None => {}
     }
 
-    str::push_str(s, opt_proto_to_str(opt_p));
+    str::push_str(&mut s, opt_proto_to_str(opt_p));
 
     return s;
 }
diff --git a/src/rustc/back/link.rs b/src/rustc/back/link.rs
index 1cfb322e39c163b71f92a8a3816a8a819cb53c0d..c2d4925838e55485fb55c3625137150c167efca3 100644
--- a/src/rustc/back/link.rs
+++ b/src/rustc/back/link.rs
@@ -548,10 +548,10 @@ fn sanitize(s: ~str) -> ~str {
           'a' .. 'z'
           | 'A' .. 'Z'
           | '0' .. '9'
-          | '_' => str::push_char(result,c),
+          | '_' => str::push_char(&mut result, c),
           _ => {
             if c > 'z' && char::is_XID_continue(c) {
-                str::push_char(result,c);
+                str::push_char(&mut result, c);
             }
           }
         }
diff --git a/src/rustc/metadata/encoder.rs b/src/rustc/metadata/encoder.rs
index e0d33035022fce2e8bb7777cf5d00d44f51a5a34..67c85102cd6990e964ecc548a3757ebec49ee1dd 100644
--- a/src/rustc/metadata/encoder.rs
+++ b/src/rustc/metadata/encoder.rs
@@ -1175,7 +1175,7 @@ fn encode_metadata(parms: encode_parms, crate: @crate) -> ~[u8] {
     //
     //   vec::from_slice(metadata_encoding_version) +
 
-    (do str::as_bytes(~"rust\x00\x00\x00\x01") |bytes| {
+    (do str::as_bytes(&~"rust\x00\x00\x00\x01") |bytes| {
         vec::slice(bytes, 0, 8)
     }) + flate::deflate_bytes(wr.buf.check_out(|buf| buf))
 }
diff --git a/src/test/bench/shootout-fasta.rs b/src/test/bench/shootout-fasta.rs
index 7194b0fbb4bbd372aa5500da019bc5696f0312de..5813aa87750c777369ba833182a80d9c33635fdd 100644
--- a/src/test/bench/shootout-fasta.rs
+++ b/src/test/bench/shootout-fasta.rs
@@ -44,8 +44,8 @@ fn make_random_fasta(wr: io::Writer, id: ~str, desc: ~str, genelist: ~[aminoacid
     let rng = @{mut last: rand::Rng().next()};
     let mut op: ~str = ~"";
     for uint::range(0u, n as uint) |_i| {
-        str::push_char(op, select_random(myrandom_next(rng, 100u32),
-                                         genelist));
+        str::push_char(&mut op, select_random(myrandom_next(rng, 100u32),
+                                              genelist));
         if str::len(op) >= LINE_LENGTH() {
             wr.write_line(op);
             op = ~"";
@@ -59,7 +59,7 @@ fn make_repeat_fasta(wr: io::Writer, id: ~str, desc: ~str, s: ~str, n: int) unsa
     let mut op: ~str = ~"";
     let sl: uint = str::len(s);
     for uint::range(0u, n as uint) |i| {
-        str::raw::push_byte(op, s[i % sl]);
+        str::raw::push_byte(&mut op, s[i % sl]);
         if str::len(op) >= LINE_LENGTH() {
             wr.write_line(op);
             op = ~"";
diff --git a/src/test/run-pass/utf8_chars.rs b/src/test/run-pass/utf8_chars.rs
index aacf5a99cbe5edb65b16c1072ee9d7c113437af6..63210c0d8aa9f6adf52c618612113be4bc4438ac 100644
--- a/src/test/run-pass/utf8_chars.rs
+++ b/src/test/run-pass/utf8_chars.rs
@@ -18,12 +18,12 @@ fn main() {
     assert (!str::is_utf8(~[0xc0_u8, 0x10_u8]));
 
     let mut stack = ~"a×c€";
-    assert (str::pop_char(stack) == '€');
-    assert (str::pop_char(stack) == 'c');
-    str::push_char(stack, 'u');
+    assert (str::pop_char(&mut stack) == '€');
+    assert (str::pop_char(&mut stack) == 'c');
+    str::push_char(&mut stack, 'u');
     assert (stack == ~"a×u");
-    assert (str::shift_char(stack) == 'a');
-    assert (str::shift_char(stack) == '×');
-    str::unshift_char(stack, 'ß');
+    assert (str::shift_char(&mut stack) == 'a');
+    assert (str::shift_char(&mut stack) == '×');
+    str::unshift_char(&mut stack, 'ß');
     assert (stack == ~"ßu");
 }