rustc: Remove &str indexing from the language.

Being able to index into the bytes of a string encourages
poor UTF-8 hygiene. To get a view of `&[u8]` from either
a `String` or `&str` slice, use the `as_bytes()` method.

Closes rust-lang#12710.

[breaking-change]

src/libcollections/str.rs

@@ -1569,8 +1569,8 @@ mod tests {
  let n2: uint = v.len();
  assert_eq!(n1, n2);
  while i < n1 {
- let a: u8 = s1.as_slice()[i];
- let b: u8 = s2.as_slice()[i];
+ let a: u8 = s1.as_bytes()[i];
+ let b: u8 = s2.as_bytes()[i];
  debug!("{}", a);
  debug!("{}", b);
  assert_eq!(a, b);

src/libcollections/string.rs

@@ -222,7 +222,7 @@ impl String {
  return None
  }
 
- let byte = self.as_slice()[len - 1];
+ let byte = self.as_bytes()[len - 1];
  self.vec.set_len(len - 1);
  Some(byte)
  }

src/libcore/str.rs

@@ -1743,7 +1743,7 @@ impl<'a> StrSlice<'a> for &'a str {
  fn lines_any(&self) -> AnyLines<'a> {
  self.lines().map(|line| {
  let l = line.len();
- if l > 0 && line[l - 1] == '\r' as u8 { line.slice(0, l - 1) }
+ if l > 0 && line.as_bytes()[l - 1] == '\r' as u8 { line.slice(0, l - 1) }
  else { line }
  })
  }
@@ -1867,26 +1867,26 @@ impl<'a> StrSlice<'a> for &'a str {
  fn is_char_boundary(&self, index: uint) -> bool {
  if index == self.len() { return true; }
  if index > self.len() { return false; }
- let b = self[index];
+ let b = self.as_bytes()[index];
  return b < 128u8 || b >= 192u8;
  }
 
  #[inline]
  fn char_range_at(&self, i: uint) -> CharRange {
- if self[i] < 128u8 {
- return CharRange {ch: self[i] as char, next: i + 1 };
+ if self.as_bytes()[i] < 128u8 {
+ return CharRange {ch: self.as_bytes()[i] as char, next: i + 1 };
  }
 
  // Multibyte case is a fn to allow char_range_at to inline cleanly
  fn multibyte_char_range_at(s: &str, i: uint) -> CharRange {
- let mut val = s[i] as u32;
+ let mut val = s.as_bytes()[i] as u32;
  let w = UTF8_CHAR_WIDTH[val as uint] as uint;
  assert!((w != 0));
 
  val = utf8_first_byte!(val, w);
- val = utf8_acc_cont_byte!(val, s[i + 1]);
- if w > 2 { val = utf8_acc_cont_byte!(val, s[i + 2]); }
- if w > 3 { val = utf8_acc_cont_byte!(val, s[i + 3]); }
+ val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 1]);
+ if w > 2 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 2]); }
+ if w > 3 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 3]); }
 
  return CharRange {ch: unsafe { mem::transmute(val) }, next: i + w};
  }
@@ -1899,23 +1899,25 @@ impl<'a> StrSlice<'a> for &'a str {
  let mut prev = start;
 
  prev = prev.saturating_sub(1);
- if self[prev] < 128 { return CharRange{ch: self[prev] as char, next: prev} }
+ if self.as_bytes()[prev] < 128 {
+ return CharRange{ch: self.as_bytes()[prev] as char, next: prev}
+ }
 
  // Multibyte case is a fn to allow char_range_at_reverse to inline cleanly
  fn multibyte_char_range_at_reverse(s: &str, mut i: uint) -> CharRange {
  // while there is a previous byte == 10......
- while i > 0 && s[i] & 192u8 == TAG_CONT_U8 {
+ while i > 0 && s.as_bytes()[i] & 192u8 == TAG_CONT_U8 {
  i -= 1u;
  }
 
- let mut val = s[i] as u32;
+ let mut val = s.as_bytes()[i] as u32;
  let w = UTF8_CHAR_WIDTH[val as uint] as uint;
  assert!((w != 0));
 
  val = utf8_first_byte!(val, w);
- val = utf8_acc_cont_byte!(val, s[i + 1]);
- if w > 2 { val = utf8_acc_cont_byte!(val, s[i + 2]); }
- if w > 3 { val = utf8_acc_cont_byte!(val, s[i + 3]); }
+ val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 1]);
+ if w > 2 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 2]); }
+ if w > 3 { val = utf8_acc_cont_byte!(val, s.as_bytes()[i + 3]); }
 
  return CharRange {ch: unsafe { mem::transmute(val) }, next: i};
  }

src/libgetopts/lib.rs

@@ -370,7 +370,7 @@ impl Matches {
 }
 
 fn is_arg(arg: &str) -> bool {
- arg.len() > 1 && arg[0] == '-' as u8
+ arg.len() > 1 && arg.as_bytes()[0] == '-' as u8
 }
 
 fn find_opt(opts: &[Opt], nm: Name) -> Option<uint> {
@@ -553,7 +553,7 @@ pub fn getopts(args: &[String], optgrps: &[OptGroup]) -> Result {
  } else {
  let mut names;
  let mut i_arg = None;
- if cur.as_slice()[1] == '-' as u8 {
+ if cur.as_bytes()[1] == '-' as u8 {
  let tail = cur.as_slice().slice(2, curlen);
  let tail_eq: Vec<&str> = tail.split('=').collect();
  if tail_eq.len() <= 1 {

src/librustc/back/link.rs

@@ -657,8 +657,8 @@ pub fn sanitize(s: &str) -> String {
 
  // Underscore-qualify anything that didn't start as an ident.
  if result.len() > 0u &&
- result.as_slice()[0] != '_' as u8 &&
- ! char::is_XID_start(result.as_slice()[0] as char) {
+ result.as_bytes()[0] != '_' as u8 &&
+ ! char::is_XID_start(result.as_bytes()[0] as char) {
  return format!("_{}", result.as_slice());
  }
 
@@ -737,9 +737,9 @@ pub fn mangle_exported_name(ccx: &CrateContext, path: PathElems,
  let extra2 = id % EXTRA_CHARS.len();
  let id = id / EXTRA_CHARS.len();
  let extra3 = id % EXTRA_CHARS.len();
- hash.push_char(EXTRA_CHARS[extra1] as char);
- hash.push_char(EXTRA_CHARS[extra2] as char);
- hash.push_char(EXTRA_CHARS[extra3] as char);
+ hash.push_char(EXTRA_CHARS.as_bytes()[extra1] as char);
+ hash.push_char(EXTRA_CHARS.as_bytes()[extra2] as char);
+ hash.push_char(EXTRA_CHARS.as_bytes()[extra3] as char);
 
  exported_name(path,
  hash.as_slice(),

src/librustc/metadata/decoder.rs

@@ -181,7 +181,7 @@ fn item_sized(item: ebml::Doc) -> ast::Sized {
 fn item_method_sort(item: ebml::Doc) -> char {
  let mut ret = 'r';
  reader::tagged_docs(item, tag_item_trait_method_sort, |doc| {
- ret = doc.as_str_slice()[0] as char;
+ ret = doc.as_str_slice().as_bytes()[0] as char;
  false
  });
  ret
@@ -757,13 +757,13 @@ fn get_explicit_self(item: ebml::Doc) -> ast::ExplicitSelf_ {
  let explicit_self_doc = reader::get_doc(item, tag_item_trait_method_explicit_self);
  let string = explicit_self_doc.as_str_slice();
 
- let explicit_self_kind = string[0];
+ let explicit_self_kind = string.as_bytes()[0];
  match explicit_self_kind as char {
  's' => ast::SelfStatic,
  'v' => ast::SelfValue,
  '~' => ast::SelfUniq,
  // FIXME(#4846) expl. region
- '&' => ast::SelfRegion(None, get_mutability(string[1])),
+ '&' => ast::SelfRegion(None, get_mutability(string.as_bytes()[1])),
  _ => fail!("unknown self type code: `{}`", explicit_self_kind as char)
  }
 }

src/librustc/middle/dead.rs

@@ -399,7 +399,7 @@ struct DeadVisitor<'a> {
 impl<'a> DeadVisitor<'a> {
  fn should_warn_about_field(&mut self, node: &ast::StructField_) -> bool {
  let (is_named, has_leading_underscore) = match node.ident() {
- Some(ref ident) => (true, token::get_ident(*ident).get()[0] == ('_' as u8)),
+ Some(ref ident) => (true, token::get_ident(*ident).get().as_bytes()[0] == ('_' as u8)),
  _ => (false, false)
  };
  let field_type = ty::node_id_to_type(self.tcx, node.id);

src/librustc/middle/liveness.rs

@@ -1511,7 +1511,7 @@ impl<'a> Liveness<'a> {
 
  fn should_warn(&self, var: Variable) -> Option<String> {
  let name = self.ir.variable_name(var);
- if name.len() == 0 || name.as_slice()[0] == ('_' as u8) {
+ if name.len() == 0 || name.as_bytes()[0] == ('_' as u8) {
  None
  } else {
  Some(name)

src/librustc/middle/mem_categorization.rs

@@ -126,7 +126,6 @@ pub enum FieldName {
 #[deriving(Clone, PartialEq, Eq, Hash)]
 pub enum ElementKind {
  VecElement,
- StrElement,
  OtherElement,
 }
 
@@ -794,7 +793,7 @@ impl<'t,TYPER:Typer> MemCategorizationContext<'t,TYPER> {
  //! - `derefs`: the deref number to be used for
  //! the implicit index deref, if any (see above)
 
- let element_ty = match ty::index(base_cmt.ty) {
+ let element_ty = match ty::array_element_ty(base_cmt.ty) {
  Some(ref mt) => mt.ty,
  None => {
  self.tcx().sess.span_bug(
@@ -1137,9 +1136,6 @@ impl<'t,TYPER:Typer> MemCategorizationContext<'t,TYPER> {
  cat_interior(_, InteriorElement(VecElement)) => {
  "vec content".to_string()
  }
- cat_interior(_, InteriorElement(StrElement)) => {
- "str content".to_string()
- }
  cat_interior(_, InteriorElement(OtherElement)) => {
  "indexed content".to_string()
  }
@@ -1320,7 +1316,6 @@ fn element_kind(t: ty::t) -> ElementKind {
  ty::ty_rptr(_, ty::mt{ty:ty, ..}) |
  ty::ty_uniq(ty) => match ty::get(ty).sty {
  ty::ty_vec(_, None) => VecElement,
- ty::ty_str => StrElement,
  _ => OtherElement
  },
  ty::ty_vec(..) => VecElement,

src/librustc/middle/ty.rs

@@ -2551,6 +2551,21 @@ pub fn deref(t: t, explicit: bool) -> Option<mt> {
 
 // Returns the type of t[i]
 pub fn index(t: t) -> Option<mt> {
+ match get(t).sty {
+ ty_vec(mt, Some(_)) => Some(mt),
+ ty_ptr(mt{ty: t, ..}) | ty_rptr(_, mt{ty: t, ..}) |
+ ty_box(t) | ty_uniq(t) => match get(t).sty {
+ ty_vec(mt, None) => Some(mt),
+ _ => None,
+ },
+ _ => None
+ }
+}
+
+// Returns the type of elements contained within an 'array-like' type.
+// This is exactly the same as the above, except it supports strings,
+// which can't actually be indexed.
+pub fn array_element_ty(t: t) -> Option<mt> {
  match get(t).sty {
  ty_vec(mt, Some(_)) => Some(mt),
  ty_ptr(mt{ty: t, ..}) | ty_rptr(_, mt{ty: t, ..}) |

src/libstd/io/fs.rs

@@ -1206,8 +1206,8 @@ mod test {
  let mut cur = [0u8, .. 2];
  for f in files {
  let stem = f.filestem_str().unwrap();
- let root = stem[0] - ('0' as u8);
- let name = stem[1] - ('0' as u8);
+ let root = stem.as_bytes()[0] - ('0' as u8);
+ let name = stem.as_bytes()[1] - ('0' as u8);
  assert!(cur[root as uint] < name);
  cur[root as uint] = name;
  }

src/libstd/path/windows.rs

@@ -242,14 +242,18 @@ impl GenericPathUnsafe for Path {
  fn is_vol_abs(path: &str, prefix: Option<PathPrefix>) -> bool {
  // assume prefix is Some(DiskPrefix)
  let rest = path.slice_from(prefix_len(prefix));
- !rest.is_empty() && rest[0].is_ascii() && is_sep(rest[0] as char)
+ !rest.is_empty() && rest.as_bytes()[0].is_ascii() && is_sep(rest.as_bytes()[0] as char)
  }
  fn shares_volume(me: &Path, path: &str) -> bool {
  // path is assumed to have a prefix of Some(DiskPrefix)
  let repr = me.repr.as_slice();
  match me.prefix {
- Some(DiskPrefix) => repr[0] == path[0].to_ascii().to_upper().to_byte(),
- Some(VerbatimDiskPrefix) => repr[4] == path[0].to_ascii().to_upper().to_byte(),
+ Some(DiskPrefix) => {
+ repr.as_bytes()[0] == path.as_bytes()[0].to_ascii().to_upper().to_byte()
+ }
+ Some(VerbatimDiskPrefix) => {
+ repr.as_bytes()[4] == path.as_bytes()[0].to_ascii().to_upper().to_byte()
+ }
  _ => false
  }
  }
@@ -279,7 +283,7 @@ impl GenericPathUnsafe for Path {
  // if me is "C:" we don't want to add a path separator
  match me.prefix {
  Some(DiskPrefix) if me.repr.len() == plen => (),
- _ if !(me.repr.len() > plen && me.repr.as_slice()[me.repr.len()-1] == SEP_BYTE) => {
+ _ if !(me.repr.len() > plen && me.repr.as_bytes()[me.repr.len()-1] == SEP_BYTE) => {
  s.push_char(SEP);
  }
  _ => ()
@@ -302,7 +306,7 @@ impl GenericPathUnsafe for Path {
  // absolute path, or cwd-relative and self is not same volume
  replace_path(self, path, prefix);
  }
- None if !path.is_empty() && is_sep_(self.prefix, path[0]) => {
+ None if !path.is_empty() && is_sep_(self.prefix, path.as_bytes()[0]) => {
  // volume-relative path
  if self.prefix.is_some() {
  // truncate self down to the prefix, then append
@@ -478,7 +482,7 @@ impl GenericPath for Path {
  match self.prefix {
  Some(DiskPrefix) => {
  let rest = self.repr.as_slice().slice_from(self.prefix_len());
- rest.len() > 0 && rest[0] == SEP_BYTE
+ rest.len() > 0 && rest.as_bytes()[0] == SEP_BYTE
  }
  Some(_) => true,
  None => false
@@ -638,11 +642,11 @@ impl Path {
  let s = match self.prefix {
  Some(_) => {
  let plen = self.prefix_len();
- if repr.len() > plen && repr[plen] == SEP_BYTE {
+ if repr.len() > plen && repr.as_bytes()[plen] == SEP_BYTE {
  repr.slice_from(plen+1)
  } else { repr.slice_from(plen) }
  }
- None if repr[0] == SEP_BYTE => repr.slice_from(1),
+ None if repr.as_bytes()[0] == SEP_BYTE => repr.slice_from(1),
  None => repr
  };
  let ret = s.split_terminator(SEP).map(Some);
@@ -665,14 +669,14 @@ impl Path {
  match (self.prefix, other.prefix) {
  (Some(DiskPrefix), Some(VerbatimDiskPrefix)) => {
  self.is_absolute() &&
- s_repr[0].to_ascii().eq_ignore_case(o_repr[4].to_ascii())
+ s_repr.as_bytes()[0].to_ascii().eq_ignore_case(o_repr.as_bytes()[4].to_ascii())
  }
  (Some(VerbatimDiskPrefix), Some(DiskPrefix)) => {
  other.is_absolute() &&
- s_repr[4].to_ascii().eq_ignore_case(o_repr[0].to_ascii())
+ s_repr.as_bytes()[4].to_ascii().eq_ignore_case(o_repr.as_bytes()[0].to_ascii())
  }
  (Some(VerbatimDiskPrefix), Some(VerbatimDiskPrefix)) => {
- s_repr[4].to_ascii().eq_ignore_case(o_repr[4].to_ascii())
+ s_repr.as_bytes()[4].to_ascii().eq_ignore_case(o_repr.as_bytes()[4].to_ascii())
  }
  (Some(UNCPrefix(_,_)), Some(VerbatimUNCPrefix(_,_))) => {
  s_repr.slice(2, self.prefix_len()) == o_repr.slice(8, other.prefix_len())
@@ -718,12 +722,12 @@ impl Path {
  let mut comps = comps;
  match (comps.is_some(),prefix) {
  (false, Some(DiskPrefix)) => {
- if s[0] >= 'a' as u8 && s[0] <= 'z' as u8 {
+ if s.as_bytes()[0] >= 'a' as u8 && s.as_bytes()[0] <= 'z' as u8 {
  comps = Some(vec![]);
  }
  }
  (false, Some(VerbatimDiskPrefix)) => {
- if s[4] >= 'a' as u8 && s[0] <= 'z' as u8 {
+ if s.as_bytes()[4] >= 'a' as u8 && s.as_bytes()[0] <= 'z' as u8 {
  comps = Some(vec![]);
  }
  }
@@ -778,12 +782,12 @@ impl Path {
  let mut s = String::with_capacity(n);
  match prefix {
  Some(DiskPrefix) => {
- s.push_char(prefix_[0].to_ascii().to_upper().to_char());
+ s.push_char(prefix_.as_bytes()[0].to_ascii().to_upper().to_char());
  s.push_char(':');
  }
  Some(VerbatimDiskPrefix) => {
  s.push_str(prefix_.slice_to(4));
- s.push_char(prefix_[4].to_ascii().to_upper().to_char());
+ s.push_char(prefix_.as_bytes()[4].to_ascii().to_upper().to_char());
  s.push_str(prefix_.slice_from(5));
  }
  Some(UNCPrefix(a,b)) => {
@@ -845,7 +849,7 @@ impl Path {
 
  fn has_nonsemantic_trailing_slash(&self) -> bool {
  is_verbatim(self) && self.repr.len() > self.prefix_len()+1 &&
- self.repr.as_slice()[self.repr.len()-1] == SEP_BYTE
+ self.repr.as_bytes()[self.repr.len()-1] == SEP_BYTE
  }
 
  fn update_normalized<S: Str>(&mut self, s: S) {
@@ -861,7 +865,7 @@ impl Path {
 /// but absolute within that volume.
 #[inline]
 pub fn is_vol_relative(path: &Path) -> bool {
- path.prefix.is_none() && is_sep_byte(&path.repr.as_slice()[0])
+ path.prefix.is_none() && is_sep_byte(&path.repr.as_bytes()[0])
 }
 
 /// Returns whether the path is considered "cwd-relative", which means a path
@@ -991,8 +995,8 @@ fn parse_prefix<'a>(mut path: &'a str) -> Option<PathPrefix> {
  } else {
  // \\?\path
  let idx = path.find('\\');
- if idx == Some(2) && path[1] == ':' as u8 {
- let c = path[0];
+ if idx == Some(2) && path.as_bytes()[1] == ':' as u8 {
+ let c = path.as_bytes()[0];
  if c.is_ascii() && ::char::is_alphabetic(c as char) {
  // \\?\C:\ path
  return Some(VerbatimDiskPrefix);
@@ -1014,9 +1018,9 @@ fn parse_prefix<'a>(mut path: &'a str) -> Option<PathPrefix> {
  }
  _ => ()
  }
- } else if path.len() > 1 && path[1] == ':' as u8 {
+ } else if path.len() > 1 && path.as_bytes()[1] == ':' as u8 {
  // C:
- let c = path[0];
+ let c = path.as_bytes()[0];
  if c.is_ascii() && ::char::is_alphabetic(c as char) {
  return Some(DiskPrefix);
  }