Rollup merge of #22727 - alexcrichton:prep-env, r=aturon

 This commit moves `std::env` away from the `std::old_io` error type as well as
the `std::old_path` module. Methods returning an error now return `io::Error`
and methods consuming or returning paths use `std::path` instead of
`std::old_path`. This commit does not yet mark these APIs as `#[stable]`.

This commit also migrates `std::old_io::TempDir` to `std::fs::TempDir` with
essentially the exact same API. This type was added to interoperate with the new
path API and has its own `tempdir` feature.

Finally, this commit reverts the deprecation of `std::os` APIs returning the old
path API types. This deprecation can come back once the entire `std::old_path`
module is deprecated.

[breaking-change]

2 files changed, 1632 insertions, 0 deletions

diff --git a/src/libstd/fs/mod.rs b/src/libstd/fs/mod.rs
new file mode 100644
index 00000000000..aa211758621
--- /dev/null
+++ b/src/libstd/fs/mod.rs
@@ -0,0 +1,1507 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+//! Filesystem manipulation operations
+//!
+//! This module contains basic methods to manipulate the contents of the local
+//! filesystem. All methods in this module represent cross-platform filesystem
+//! operations. Extra platform-specific functionality can be found in the
+//! extension traits of `std::os::$platform`.
+
+#![unstable(feature = "fs")]
+
+use core::prelude::*;
+
+use io::{self, Error, ErrorKind, SeekFrom, Seek, Read, Write};
+use path::{AsPath, Path, PathBuf};
+use sys::fs2 as fs_imp;
+use sys_common::{AsInnerMut, FromInner, AsInner};
+use vec::Vec;
+
+pub use self::tempdir::TempDir;
+
+mod tempdir;
+
+/// A reference to an open file on the filesystem.
+///
+/// An instance of a `File` can be read and/or written depending on what options
+/// it was opened with. Files also implement `Seek` to alter the logical cursor
+/// that the file contains internally.
+///
+/// # Example
+///
+/// ```no_run
+/// use std::io::prelude::*;
+/// use std::fs::File;
+///
+/// # fn foo() -> std::io::Result<()> {
+/// let mut f = try!(File::create("foo.txt"));
+/// try!(f.write_all(b"Hello, world!"));
+///
+/// let mut f = try!(File::open("foo.txt"));
+/// let mut s = String::new();
+/// try!(f.read_to_string(&mut s));
+/// assert_eq!(s, "Hello, world!");
+/// # Ok(())
+/// # }
+/// ```
+pub struct File {
+    inner: fs_imp::File,
+    path: PathBuf,
+}
+
+/// Metadata information about a file.
+///
+/// This structure is returned from the `metadata` function or method and
+/// represents known metadata about a file such as its permissions, size,
+/// modification times, etc.
+pub struct Metadata(fs_imp::FileAttr);
+
+/// Iterator over the entries in a directory.
+///
+/// This iterator is returned from the `read_dir` function of this module and
+/// will yield instances of `io::Result<DirEntry>`. Through a `DirEntry`
+/// information like the entry's path and possibly other metadata can be
+/// learned.
+pub struct ReadDir(fs_imp::ReadDir);
+
+/// Entries returned by the `ReadDir` iterator.
+///
+/// An instance of `DirEntry` represents an entry inside of a directory on the
+/// filesystem. Each entry can be inspected via methods to learn about the full
+/// path or possibly other metadata through per-platform extension traits.
+pub struct DirEntry(fs_imp::DirEntry);
+
+/// An iterator that recursively walks over the contents of a directory.
+pub struct WalkDir {
+    cur: Option<ReadDir>,
+    stack: Vec<io::Result<ReadDir>>,
+}
+
+/// Options and flags which can be used to configure how a file is opened.
+///
+/// This builder exposes the ability to configure how a `File` is opened and
+/// what operations are permitted on the open file. The `File::open` and
+/// `File::create` methods are aliases for commonly used options using this
+/// builder.
+#[derive(Clone)]
+pub struct OpenOptions(fs_imp::OpenOptions);
+
+/// Representation of the various permissions on a file.
+///
+/// This module only currently provides one bit of information, `readonly`,
+/// which is exposed on all currently supported platforms. Unix-specific
+/// functionality, such as mode bits, is available through the
+/// `os::unix::PermissionsExt` trait.
+#[derive(Clone, PartialEq, Eq, Debug)]
+pub struct Permissions(fs_imp::FilePermissions);
+
+impl File {
+    /// Attempts to open a file in read-only mode.
+    ///
+    /// See the `OpenOptions::open` method for more details.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error if `path` does not already exist.
+    /// Other errors may also be returned according to `OpenOptions::open`.
+    pub fn open<P: AsPath + ?Sized>(path: &P) -> io::Result<File> {
+        OpenOptions::new().read(true).open(path)
+    }
+
+    /// Open a file in write-only mode.
+    ///
+    /// This function will create a file if it does not exist,
+    /// and will truncate it if it does.
+    ///
+    /// See the `OpenOptions::open` function for more details.
+    pub fn create<P: AsPath + ?Sized>(path: &P) -> io::Result<File> {
+        OpenOptions::new().write(true).create(true).truncate(true).open(path)
+    }
+
+    /// Returns the original path that was used to open this file.
+    pub fn path(&self) -> Option<&Path> {
+        Some(&self.path)
+    }
+
+    /// Attempt to sync all OS-internal metadata to disk.
+    ///
+    /// This function will attempt to ensure that all in-core data reaches the
+    /// filesystem before returning.
+    pub fn sync_all(&self) -> io::Result<()> {
+        self.inner.fsync()
+    }
+
+    /// This function is similar to `sync_all`, except that it may not
+    /// synchronize file metadata to the filesystem.
+    ///
+    /// This is intended for use cases that must synchronize content, but don't
+    /// need the metadata on disk. The goal of this method is to reduce disk
+    /// operations.
+    ///
+    /// Note that some platforms may simply implement this in terms of
+    /// `sync_all`.
+    pub fn sync_data(&self) -> io::Result<()> {
+        self.inner.datasync()
+    }
+
+    /// Truncates or extends the underlying file, updating the size of
+    /// this file to become `size`.
+    ///
+    /// If the `size` is less than the current file's size, then the file will
+    /// be shrunk. If it is greater than the current file's size, then the file
+    /// will be extended to `size` and have all of the intermediate data filled
+    /// in with 0s.
+    pub fn set_len(&self, size: u64) -> io::Result<()> {
+        self.inner.truncate(size)
+    }
+
+    /// Queries information about the underlying file.
+    pub fn metadata(&self) -> io::Result<Metadata> {
+        self.inner.file_attr().map(Metadata)
+    }
+}
+
+impl AsInner<fs_imp::File> for File {
+    fn as_inner(&self) -> &fs_imp::File { &self.inner }
+}
+impl Read for File {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+}
+impl Write for File {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner.write(buf)
+    }
+    fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
+}
+impl Seek for File {
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        self.inner.seek(pos)
+    }
+}
+impl<'a> Read for &'a File {
+    fn read(&mut self, buf: &mut [u8]) -> io::Result<usize> {
+        self.inner.read(buf)
+    }
+}
+impl<'a> Write for &'a File {
+    fn write(&mut self, buf: &[u8]) -> io::Result<usize> {
+        self.inner.write(buf)
+    }
+    fn flush(&mut self) -> io::Result<()> { self.inner.flush() }
+}
+impl<'a> Seek for &'a File {
+    fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
+        self.inner.seek(pos)
+    }
+}
+
+impl OpenOptions {
+    /// Creates a blank net set of options ready for configuration.
+    ///
+    /// All options are initially set to `false`.
+    pub fn new() -> OpenOptions {
+        OpenOptions(fs_imp::OpenOptions::new())
+    }
+
+    /// Set the option for read access.
+    ///
+    /// This option, when true, will indicate that the file should be
+    /// `read`-able if opened.
+    pub fn read(&mut self, read: bool) -> &mut OpenOptions {
+        self.0.read(read); self
+    }
+
+    /// Set the option for write access.
+    ///
+    /// This option, when true, will indicate that the file should be
+    /// `write`-able if opened.
+    pub fn write(&mut self, write: bool) -> &mut OpenOptions {
+        self.0.write(write); self
+    }
+
+    /// Set the option for the append mode.
+    ///
+    /// This option, when true, means that writes will append to a file instead
+    /// of overwriting previous contents.
+    pub fn append(&mut self, append: bool) -> &mut OpenOptions {
+        self.0.append(append); self
+    }
+
+    /// Set the option for truncating a previous file.
+    ///
+    /// If a file is successfully opened with this option set it will truncate
+    /// the file to 0 length if it already exists.
+    pub fn truncate(&mut self, truncate: bool) -> &mut OpenOptions {
+        self.0.truncate(truncate); self
+    }
+
+    /// Set the option for creating a new file.
+    ///
+    /// This option indicates whether a new file will be created if the file
+    /// does not yet already exist.
+    pub fn create(&mut self, create: bool) -> &mut OpenOptions {
+        self.0.create(create); self
+    }
+
+    /// Open a file at `path` with the options specified by `self`.
+    ///
+    /// # Errors
+    ///
+    /// This function will return an error under a number of different
+    /// circumstances, to include but not limited to:
+    ///
+    /// * Opening a file that does not exist with read access.
+    /// * Attempting to open a file with access that the user lacks
+    ///   permissions for
+    /// * Filesystem-level errors (full disk, etc)
+    pub fn open<P: AsPath + ?Sized>(&self, path: &P) -> io::Result<File> {
+        let path = path.as_path();
+        let inner = try!(fs_imp::File::open(path, &self.0));
+
+        // On *BSD systems, we can open a directory as a file and read from
+        // it: fd=open("/tmp", O_RDONLY); read(fd, buf, N); due to an old
+        // tradition before the introduction of opendir(3).  We explicitly
+        // reject it because there are few use cases.
+        if cfg!(not(any(target_os = "linux", target_os = "android"))) &&
+           try!(inner.file_attr()).is_dir() {
+            Err(Error::new(ErrorKind::InvalidInput, "is a directory", None))
+        } else {
+            Ok(File { path: path.to_path_buf(), inner: inner })
+        }
+    }
+}
+impl AsInnerMut<fs_imp::OpenOptions> for OpenOptions {
+    fn as_inner_mut(&mut self) -> &mut fs_imp::OpenOptions { &mut self.0 }
+}
+
+impl Metadata {
+    /// Returns whether this metadata is for a directory.
+    pub fn is_dir(&self) -> bool { self.0.is_dir() }
+
+    /// Returns whether this metadata is for a regular file.
+    pub fn is_file(&self) -> bool { self.0.is_file() }
+
+    /// Returns the size of the file, in bytes, this metadata is for.
+    pub fn len(&self) -> u64 { self.0.size() }
+
+    /// Returns the permissions of the file this metadata is for.
+    pub fn permissions(&self) -> Permissions {
+        Permissions(self.0.perm())
+    }
+
+    /// Returns the most recent access time for a file.
+    ///
+    /// The return value is in milliseconds since the epoch.
+    pub fn accessed(&self) -> u64 { self.0.accessed() }
+
+    /// Returns the most recent modification time for a file.
+    ///
+    /// The return value is in milliseconds since the epoch.
+    pub fn modified(&self) -> u64 { self.0.modified() }
+}
+
+impl Permissions {
+    /// Returns whether these permissions describe a readonly file.
+    pub fn readonly(&self) -> bool { self.0.readonly() }
+
+    /// Modify the readonly flag for this set of permissions.
+    ///
+    /// This operation does **not** modify the filesystem. To modify the
+    /// filesystem use the `fs::set_permissions` function.
+    pub fn set_readonly(&mut self, readonly: bool) {
+        self.0.set_readonly(readonly)
+    }
+}
+
+impl FromInner<fs_imp::FilePermissions> for Permissions {
+    fn from_inner(f: fs_imp::FilePermissions) -> Permissions {
+        Permissions(f)
+    }
+}
+
+impl Iterator for ReadDir {
+    type Item = io::Result<DirEntry>;
+
+    fn next(&mut self) -> Option<io::Result<DirEntry>> {
+        self.0.next().map(|entry| entry.map(DirEntry))
+    }
+}
+
+impl DirEntry {
+    /// Returns the full path to the file that this entry represents.
+    ///
+    /// The full path is created by joining the original path to `read_dir` or
+    /// `walk_dir` with the filename of this entry.
+    pub fn path(&self) -> PathBuf { self.0.path() }
+}
+
+/// Remove a file from the underlying filesystem.
+///
+/// # Example
+///
+/// ```rust,no_run
+/// use std::fs;
+///
+/// fs::remove_file("/some/file/path.txt");
+/// ```
+///
+/// Note that, just because an unlink call was successful, it is not
+/// guaranteed that a file is immediately deleted (e.g. depending on
+/// platform, other open file descriptors may prevent immediate removal).
+///
+/// # Errors
+///
+/// This function will return an error if `path` points to a directory, if the
+/// user lacks permissions to remove the file, or if some other filesystem-level
+/// error occurs.
+pub fn remove_file<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+    let path = path.as_path();
+    let e = match fs_imp::unlink(path) {
+        Ok(()) => return Ok(()),
+        Err(e) => e,
+    };
+    if !cfg!(windows) { return Err(e) }
+
+    // On unix, a readonly file can be successfully removed. On windows,
+    // however, it cannot. To keep the two platforms in line with
+    // respect to their behavior, catch this case on windows, attempt to
+    // change it to read-write, and then remove the file.
+    if e.kind() != ErrorKind::PermissionDenied { return Err(e) }
+
+    let attr = match metadata(path) { Ok(a) => a, Err(..) => return Err(e) };
+    let mut perms = attr.permissions();
+    if !perms.readonly() { return Err(e) }
+    perms.set_readonly(false);
+
+    if set_permissions(path, perms).is_err() { return Err(e) }
+    if fs_imp::unlink(path).is_ok() { return Ok(()) }
+
+    // Oops, try to put things back the way we found it
+    let _ = set_permissions(path, attr.permissions());
+    Err(e)
+}
+
+/// Given a path, query the file system to get information about a file,
+/// directory, etc.
+///
+/// This function will traverse soft links to query information about the
+/// destination file.
+///
+/// # Example
+///
+/// ```rust,no_run
+/// # fn foo() -> std::io::Result<()> {
+/// use std::fs;
+///
+/// let attr = try!(fs::metadata("/some/file/path.txt"));
+/// // inspect attr ...
+/// # Ok(())
+/// # }
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the user lacks the requisite
+/// permissions to perform a `metadata` call on the given `path` or if there
+/// is no entry in the filesystem at the provided path.
+pub fn metadata<P: AsPath + ?Sized>(path: &P) -> io::Result<Metadata> {
+    fs_imp::stat(path.as_path()).map(Metadata)
+}
+
+/// Rename a file or directory to a new name.
+///
+/// # Example
+///
+/// ```rust,no_run
+/// use std::fs;
+///
+/// fs::rename("foo", "bar");
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the provided `from` doesn't exist, if
+/// the process lacks permissions to view the contents, if `from` and `to`
+/// reside on separate filesystems, or if some other intermittent I/O error
+/// occurs.
+pub fn rename<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
+                                                      -> io::Result<()> {
+    fs_imp::rename(from.as_path(), to.as_path())
+}
+
+/// Copies the contents of one file to another. This function will also
+/// copy the permission bits of the original file to the destination file.
+///
+/// This function will **overwrite** the contents of `to`.
+///
+/// Note that if `from` and `to` both point to the same file, then the file
+/// will likely get truncated by this operation.
+///
+/// # Example
+///
+/// ```rust
+/// use std::fs;
+///
+/// fs::copy("foo.txt", "bar.txt");
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error in the following situations, but is not
+/// limited to just these cases:
+///
+/// * The `from` path is not a file
+/// * The `from` file does not exist
+/// * The current process does not have the permission rights to access
+///   `from` or write `to`
+pub fn copy<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
+                                                    -> io::Result<u64> {
+    let from = from.as_path();
+    if !from.is_file() {
+        return Err(Error::new(ErrorKind::MismatchedFileTypeForOperation,
+                              "the source path is not an existing file",
+                              None))
+    }
+
+    let mut reader = try!(File::open(from));
+    let mut writer = try!(File::create(to));
+    let perm = try!(reader.metadata()).permissions();
+
+    let ret = try!(io::copy(&mut reader, &mut writer));
+    try!(set_permissions(to, perm));
+    Ok(ret)
+}
+
+/// Creates a new hard link on the filesystem.
+///
+/// The `dst` path will be a link pointing to the `src` path. Note that systems
+/// often require these two paths to both be located on the same filesystem.
+pub fn hard_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
+                                                         -> io::Result<()> {
+    fs_imp::link(src.as_path(), dst.as_path())
+}
+
+/// Creates a new soft link on the filesystem.
+///
+/// The `dst` path will be a soft link pointing to the `src` path.
+pub fn soft_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
+                                                         -> io::Result<()> {
+    fs_imp::symlink(src.as_path(), dst.as_path())
+}
+
+/// Reads a soft link, returning the file that the link points to.
+///
+/// # Errors
+///
+/// This function will return an error on failure. Failure conditions include
+/// reading a file that does not exist or reading a file that is not a soft
+/// link.
+pub fn read_link<P: AsPath + ?Sized>(path: &P) -> io::Result<PathBuf> {
+    fs_imp::readlink(path.as_path())
+}
+
+/// Create a new, empty directory at the provided path
+///
+/// # Example
+///
+/// ```rust
+/// use std::fs;
+///
+/// fs::create_dir("/some/dir");
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the user lacks permissions to make a
+/// new directory at the provided `path`, or if the directory already exists.
+pub fn create_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+    fs_imp::mkdir(path.as_path())
+}
+
+/// Recursively create a directory and all of its parent components if they
+/// are missing.
+///
+/// # Errors
+///
+/// This function will fail if any directory in the path specified by `path`
+/// does not already exist and it could not be created otherwise. The specific
+/// error conditions for when a directory is being created (after it is
+/// determined to not exist) are outlined by `fs::create_dir`.
+pub fn create_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+    let path = path.as_path();
+    if path.is_dir() { return Ok(()) }
+    match path.parent() {
+        Some(p) if p != path => try!(create_dir_all(p)),
+        _ => {}
+    }
+    create_dir(path)
+}
+
+/// Remove an existing, empty directory
+///
+/// # Example
+///
+/// ```rust
+/// use std::fs;
+///
+/// fs::remove_dir("/some/dir");
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the user lacks permissions to remove
+/// the directory at the provided `path`, or if the directory isn't empty.
+pub fn remove_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+    fs_imp::rmdir(path.as_path())
+}
+
+/// Removes a directory at this path, after removing all its contents. Use
+/// carefully!
+///
+/// This function does **not** follow soft links and it will simply remove the
+/// soft link itself.
+///
+/// # Errors
+///
+/// See `file::remove_file` and `fs::remove_dir`
+pub fn remove_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+    let path = path.as_path();
+    for child in try!(read_dir(path)) {
+        let child = try!(child).path();
+        let stat = try!(lstat(&*child));
+        if stat.is_dir() {
+            try!(remove_dir_all(&*child));
+        } else {
+            try!(remove_file(&*child));
+        }
+    }
+    return remove_dir(path);
+
+    #[cfg(unix)]
+    fn lstat(path: &Path) -> io::Result<fs_imp::FileAttr> { fs_imp::lstat(path) }
+    #[cfg(windows)]
+    fn lstat(path: &Path) -> io::Result<fs_imp::FileAttr> { fs_imp::stat(path) }
+}
+
+/// Returns an iterator over the entries within a directory.
+///
+/// The iterator will yield instances of `io::Result<DirEntry>`. New errors may
+/// be encountered after an iterator is initially constructed.
+///
+/// # Example
+///
+/// ```rust
+/// use std::io;
+/// use std::fs::{self, PathExt, DirEntry};
+/// use std::path::Path;
+///
+/// // one possible implementation of fs::walk_dir only visiting files
+/// fn visit_dirs(dir: &Path, cb: &mut FnMut(DirEntry)) -> io::Result<()> {
+///     if dir.is_dir() {
+///         for entry in try!(fs::read_dir(dir)) {
+///             let entry = try!(entry);
+///             if entry.path().is_dir() {
+///                 try!(visit_dirs(&entry.path(), cb));
+///             } else {
+///                 cb(entry);
+///             }
+///         }
+///     }
+///     Ok(())
+/// }
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the provided `path` doesn't exist, if
+/// the process lacks permissions to view the contents or if the `path` points
+/// at a non-directory file
+pub fn read_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<ReadDir> {
+    fs_imp::readdir(path.as_path()).map(ReadDir)
+}
+
+/// Returns an iterator that will recursively walk the directory structure
+/// rooted at `path`.
+///
+/// The path given will not be iterated over, and this will perform iteration in
+/// some top-down order.  The contents of unreadable subdirectories are ignored.
+///
+/// The iterator will yield instances of `io::Result<DirEntry>`. New errors may
+/// be encountered after an iterator is initially constructed.
+pub fn walk_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<WalkDir> {
+    let start = try!(read_dir(path));
+    Ok(WalkDir { cur: Some(start), stack: Vec::new() })
+}
+
+impl Iterator for WalkDir {
+    type Item = io::Result<DirEntry>;
+
+    fn next(&mut self) -> Option<io::Result<DirEntry>> {
+        loop {
+            if let Some(ref mut cur) = self.cur {
+                match cur.next() {
+                    Some(Err(e)) => return Some(Err(e)),
+                    Some(Ok(next)) => {
+                        let path = next.path();
+                        if path.is_dir() {
+                            self.stack.push(read_dir(&*path));
+                        }
+                        return Some(Ok(next))
+                    }
+                    None => {}
+                }
+            }
+            self.cur = None;
+            match self.stack.pop() {
+                Some(Err(e)) => return Some(Err(e)),
+                Some(Ok(next)) => self.cur = Some(next),
+                None => return None,
+            }
+        }
+    }
+}
+
+/// Utility methods for paths.
+pub trait PathExt {
+    /// Get information on the file, directory, etc at this path.
+    ///
+    /// Consult the `fs::stat` documentation for more info.
+    ///
+    /// This call preserves identical runtime/error semantics with `file::stat`.
+    fn metadata(&self) -> io::Result<Metadata>;
+
+    /// Boolean value indicator whether the underlying file exists on the local
+    /// filesystem. Returns false in exactly the cases where `fs::stat` fails.
+    fn exists(&self) -> bool;
+
+    /// Whether the underlying implementation (be it a file path, or something
+    /// else) points at a "regular file" on the FS. Will return false for paths
+    /// to non-existent locations or directories or other non-regular files
+    /// (named pipes, etc). Follows links when making this determination.
+    fn is_file(&self) -> bool;
+
+    /// Whether the underlying implementation (be it a file path, or something
+    /// else) is pointing at a directory in the underlying FS. Will return
+    /// false for paths to non-existent locations or if the item is not a
+    /// directory (eg files, named pipes, etc). Follows links when making this
+    /// determination.
+    fn is_dir(&self) -> bool;
+}
+
+impl PathExt for Path {
+    fn metadata(&self) -> io::Result<Metadata> { metadata(self) }
+
+    fn exists(&self) -> bool { metadata(self).is_ok() }
+
+    fn is_file(&self) -> bool {
+        metadata(self).map(|s| s.is_file()).unwrap_or(false)
+    }
+    fn is_dir(&self) -> bool {
+        metadata(self).map(|s| s.is_dir()).unwrap_or(false)
+    }
+}
+
+/// Changes the timestamps for a file's last modification and access time.
+///
+/// The file at the path specified will have its last access time set to
+/// `atime` and its modification time set to `mtime`. The times specified should
+/// be in milliseconds.
+pub fn set_file_times<P: AsPath + ?Sized>(path: &P, accessed: u64,
+                                          modified: u64) -> io::Result<()> {
+    fs_imp::utimes(path.as_path(), accessed, modified)
+}
+
+/// Changes the permissions found on a file or a directory.
+///
+/// # Example
+///
+/// ```
+/// # fn foo() -> std::io::Result<()> {
+/// use std::fs;
+///
+/// let mut perms = try!(fs::metadata("foo.txt")).permissions();
+/// perms.set_readonly(true);
+/// try!(fs::set_permissions("foo.txt", perms));
+/// # Ok(())
+/// # }
+/// ```
+///
+/// # Errors
+///
+/// This function will return an error if the provided `path` doesn't exist, if
+/// the process lacks permissions to change the attributes of the file, or if
+/// some other I/O error is encountered.
+pub fn set_permissions<P: AsPath + ?Sized>(path: &P, perm: Permissions)
+                                           -> io::Result<()> {
+    fs_imp::set_perm(path.as_path(), perm.0)
+}
+
+#[cfg(test)]
+mod tests {
+    #![allow(deprecated)] //rand
+
+    use prelude::v1::*;
+    use io::prelude::*;
+
+    use fs::{self, File, OpenOptions};
+    use io::{ErrorKind, SeekFrom};
+    use path::PathBuf;
+    use path::Path as Path2;
+    use os;
+    use rand::{self, StdRng, Rng};
+    use str;
+
+    macro_rules! check { ($e:expr) => (
+        match $e {
+            Ok(t) => t,
+            Err(e) => panic!("{} failed with: {}", stringify!($e), e),
+        }
+    ) }
+
+    macro_rules! error { ($e:expr, $s:expr) => (
+        match $e {
+            Ok(_) => panic!("Unexpected success. Should've been: {:?}", $s),
+            Err(ref err) => assert!(err.to_string().contains($s.as_slice()),
+                                    format!("`{}` did not contain `{}`", err, $s))
+        }
+    ) }
+
+    pub struct TempDir(PathBuf);
+
+    impl TempDir {
+        fn join(&self, path: &str) -> PathBuf {
+            let TempDir(ref p) = *self;
+            p.join(path)
+        }
+
+        fn path<'a>(&'a self) -> &'a Path2 {
+            let TempDir(ref p) = *self;
+            p
+        }
+    }
+
+    impl Drop for TempDir {
+        fn drop(&mut self) {
+            // Gee, seeing how we're testing the fs module I sure hope that we
+            // at least implement this correctly!
+            let TempDir(ref p) = *self;
+            check!(fs::remove_dir_all(p));
+        }
+    }
+
+    pub fn tmpdir() -> TempDir {
+        let s = os::tmpdir();
+        let p = Path2::new(s.as_str().unwrap());
+        let ret = p.join(&format!("rust-{}", rand::random::<u32>()));
+        check!(fs::create_dir(&ret));
+        TempDir(ret)
+    }
+
+    #[test]
+    fn file_test_io_smoke_test() {
+        let message = "it's alright. have a good time";
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_rt_io_file_test.txt");
+        {
+            let mut write_stream = check!(File::create(filename));
+            check!(write_stream.write(message.as_bytes()));
+        }
+        {
+            let mut read_stream = check!(File::open(filename));
+            let mut read_buf = [0; 1028];
+            let read_str = match check!(read_stream.read(&mut read_buf)) {
+                -1|0 => panic!("shouldn't happen"),
+                n => str::from_utf8(&read_buf[..n]).unwrap().to_string()
+            };
+            assert_eq!(read_str.as_slice(), message);
+        }
+        check!(fs::remove_file(filename));
+    }
+
+    #[test]
+    fn invalid_path_raises() {
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_that_does_not_exist.txt");
+        let result = File::open(filename);
+
+        if cfg!(unix) {
+            error!(result, "o such file or directory");
+        }
+        // error!(result, "couldn't open path as file");
+        // error!(result, format!("path={}; mode=open; access=read", filename.display()));
+    }
+
+    #[test]
+    fn file_test_iounlinking_invalid_path_should_raise_condition() {
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_another_file_that_does_not_exist.txt");
+
+        let result = fs::remove_file(filename);
+
+        if cfg!(unix) {
+            error!(result, "o such file or directory");
+        }
+        // error!(result, "couldn't unlink path");
+        // error!(result, format!("path={}", filename.display()));
+    }
+
+    #[test]
+    fn file_test_io_non_positional_read() {
+        let message: &str = "ten-four";
+        let mut read_mem = [0; 8];
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_rt_io_file_test_positional.txt");
+        {
+            let mut rw_stream = check!(File::create(filename));
+            check!(rw_stream.write(message.as_bytes()));
+        }
+        {
+            let mut read_stream = check!(File::open(filename));
+            {
+                let read_buf = &mut read_mem[0..4];
+                check!(read_stream.read(read_buf));
+            }
+            {
+                let read_buf = &mut read_mem[4..8];
+                check!(read_stream.read(read_buf));
+            }
+        }
+        check!(fs::remove_file(filename));
+        let read_str = str::from_utf8(&read_mem).unwrap();
+        assert_eq!(read_str, message);
+    }
+
+    #[test]
+    fn file_test_io_seek_and_tell_smoke_test() {
+        let message = "ten-four";
+        let mut read_mem = [0; 4];
+        let set_cursor = 4 as u64;
+        let mut tell_pos_pre_read;
+        let mut tell_pos_post_read;
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_rt_io_file_test_seeking.txt");
+        {
+            let mut rw_stream = check!(File::create(filename));
+            check!(rw_stream.write(message.as_bytes()));
+        }
+        {
+            let mut read_stream = check!(File::open(filename));
+            check!(read_stream.seek(SeekFrom::Start(set_cursor)));
+            tell_pos_pre_read = check!(read_stream.seek(SeekFrom::Current(0)));
+            check!(read_stream.read(&mut read_mem));
+            tell_pos_post_read = check!(read_stream.seek(SeekFrom::Current(0)));
+        }
+        check!(fs::remove_file(filename));
+        let read_str = str::from_utf8(&read_mem).unwrap();
+        assert_eq!(read_str, &message[4..8]);
+        assert_eq!(tell_pos_pre_read, set_cursor);
+        assert_eq!(tell_pos_post_read, message.len() as u64);
+    }
+
+    #[test]
+    fn file_test_io_seek_and_write() {
+        let initial_msg =   "food-is-yummy";
+        let overwrite_msg =    "-the-bar!!";
+        let final_msg =     "foo-the-bar!!";
+        let seek_idx = 3;
+        let mut read_mem = [0; 13];
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_rt_io_file_test_seek_and_write.txt");
+        {
+            let mut rw_stream = check!(File::create(filename));
+            check!(rw_stream.write(initial_msg.as_bytes()));
+            check!(rw_stream.seek(SeekFrom::Start(seek_idx)));
+            check!(rw_stream.write(overwrite_msg.as_bytes()));
+        }
+        {
+            let mut read_stream = check!(File::open(filename));
+            check!(read_stream.read(&mut read_mem));
+        }
+        check!(fs::remove_file(filename));
+        let read_str = str::from_utf8(&read_mem).unwrap();
+        assert!(read_str == final_msg);
+    }
+
+    #[test]
+    fn file_test_io_seek_shakedown() {
+        //                   01234567890123
+        let initial_msg =   "qwer-asdf-zxcv";
+        let chunk_one: &str = "qwer";
+        let chunk_two: &str = "asdf";
+        let chunk_three: &str = "zxcv";
+        let mut read_mem = [0; 4];
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_rt_io_file_test_seek_shakedown.txt");
+        {
+            let mut rw_stream = check!(File::create(filename));
+            check!(rw_stream.write(initial_msg.as_bytes()));
+        }
+        {
+            let mut read_stream = check!(File::open(filename));
+
+            check!(read_stream.seek(SeekFrom::End(-4)));
+            check!(read_stream.read(&mut read_mem));
+            assert_eq!(str::from_utf8(&read_mem).unwrap(), chunk_three);
+
+            check!(read_stream.seek(SeekFrom::Current(-9)));
+            check!(read_stream.read(&mut read_mem));
+            assert_eq!(str::from_utf8(&read_mem).unwrap(), chunk_two);
+
+            check!(read_stream.seek(SeekFrom::Start(0)));
+            check!(read_stream.read(&mut read_mem));
+            assert_eq!(str::from_utf8(&read_mem).unwrap(), chunk_one);
+        }
+        check!(fs::remove_file(filename));
+    }
+
+    #[test]
+    fn file_test_stat_is_correct_on_is_file() {
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_stat_correct_on_is_file.txt");
+        {
+            let mut opts = OpenOptions::new();
+            let mut fs = check!(opts.read(true).write(true)
+                                    .create(true).open(filename));
+            let msg = "hw";
+            fs.write(msg.as_bytes()).unwrap();
+
+            let fstat_res = check!(fs.metadata());
+            assert!(fstat_res.is_file());
+        }
+        let stat_res_fn = check!(fs::metadata(filename));
+        assert!(stat_res_fn.is_file());
+        let stat_res_meth = check!(filename.metadata());
+        assert!(stat_res_meth.is_file());
+        check!(fs::remove_file(filename));
+    }
+
+    #[test]
+    fn file_test_stat_is_correct_on_is_dir() {
+        let tmpdir = tmpdir();
+        let filename = &tmpdir.join("file_stat_correct_on_is_dir");
+        check!(fs::create_dir(filename));
+        let stat_res_fn = check!(fs::metadata(filename));
+        assert!(stat_res_fn.is_dir());
+        let stat_res_meth = check!(filename.metadata());
+        assert!(stat_res_meth.is_dir());
+        check!(fs::remove_dir(filename));
+    }
+
+    #[test]
+    fn file_test_fileinfo_false_when_checking_is_file_on_a_directory() {
+        let tmpdir = tmpdir();
+        let dir = &tmpdir.join("fileinfo_false_on_dir");
+        check!(fs::create_dir(dir));
+        assert!(dir.is_file() == false);
+        check!(fs::remove_dir(dir));
+    }
+
+    #[test]
+    fn file_test_fileinfo_check_exists_before_and_after_file_creation() {
+        let tmpdir = tmpdir();
+        let file = &tmpdir.join("fileinfo_check_exists_b_and_a.txt");
+        check!(check!(File::create(file)).write(b"foo"));
+        assert!(file.exists());
+        check!(fs::remove_file(file));
+        assert!(!file.exists());
+    }
+
+    #[test]
+    fn file_test_directoryinfo_check_exists_before_and_after_mkdir() {
+        let tmpdir = tmpdir();
+        let dir = &tmpdir.join("before_and_after_dir");
+        assert!(!dir.exists());
+        check!(fs::create_dir(dir));
+        assert!(dir.exists());
+        assert!(dir.is_dir());
+        check!(fs::remove_dir(dir));
+        assert!(!dir.exists());
+    }
+
+    #[test]
+    fn file_test_directoryinfo_readdir() {
+        let tmpdir = tmpdir();
+        let dir = &tmpdir.join("di_readdir");
+        check!(fs::create_dir(dir));
+        let prefix = "foo";
+        for n in range(0, 3) {
+            let f = dir.join(&format!("{}.txt", n));
+            let mut w = check!(File::create(&f));
+            let msg_str = format!("{}{}", prefix, n.to_string());
+            let msg = msg_str.as_bytes();
+            check!(w.write(msg));
+        }
+        let files = check!(fs::read_dir(dir));
+        let mut mem = [0u8; 4];
+        for f in files {
+            let f = f.unwrap().path();
+            {
+                let n = f.file_stem().unwrap();
+                check!(check!(File::open(&f)).read(&mut mem));
+                let read_str = str::from_utf8(&mem).unwrap();
+                let expected = format!("{}{}", prefix, n.to_str().unwrap());
+                assert_eq!(expected.as_slice(), read_str);
+            }
+            check!(fs::remove_file(&f));
+        }
+        check!(fs::remove_dir(dir));
+    }
+
+    #[test]
+    fn file_test_walk_dir() {
+        let tmpdir = tmpdir();
+        let dir = &tmpdir.join("walk_dir");
+        check!(fs::create_dir(dir));
+
+        let dir1 = &dir.join("01/02/03");
+        check!(fs::create_dir_all(dir1));
+        check!(File::create(&dir1.join("04")));
+
+        let dir2 = &dir.join("11/12/13");
+        check!(fs::create_dir_all(dir2));
+        check!(File::create(&dir2.join("14")));
+
+        let files = check!(fs::walk_dir(dir));
+        let mut cur = [0u8; 2];
+        for f in files {
+            let f = f.unwrap().path();
+            let stem = f.file_stem().unwrap().to_str().unwrap();
+            let root = stem.as_bytes()[0] - b'0';
+            let name = stem.as_bytes()[1] - b'0';
+            assert!(cur[root as usize] < name);
+            cur[root as usize] = name;
+        }
+
+        check!(fs::remove_dir_all(dir));
+    }
+
+    #[test]
+    fn mkdir_path_already_exists_error() {
+        let tmpdir = tmpdir();
+        let dir = &tmpdir.join("mkdir_error_twice");
+        check!(fs::create_dir(dir));
+        let e = fs::create_dir(dir).err().unwrap();
+        assert_eq!(e.kind(), ErrorKind::PathAlreadyExists);
+    }
+
+    #[test]
+    fn recursive_mkdir() {
+        let tmpdir = tmpdir();
+        let dir = tmpdir.join("d1/d2");
+        check!(fs::create_dir_all(&dir));
+        assert!(dir.is_dir())
+    }
+
+    #[test]
+    fn recursive_mkdir_failure() {
+        let tmpdir = tmpdir();
+        let dir = tmpdir.join("d1");
+        let file = dir.join("f1");
+
+        check!(fs::create_dir_all(&dir));
+        check!(File::create(&file));
+
+        let result = fs::create_dir_all(&file);
+
+        assert!(result.is_err());
+        // error!(result, "couldn't recursively mkdir");
+        // error!(result, "couldn't create directory");
+        // error!(result, "mode=0700");
+        // error!(result, format!("path={}", file.display()));
+    }
+
+    #[test]
+    fn recursive_mkdir_slash() {
+        check!(fs::create_dir_all(&Path2::new("/")));
+    }
+
+    // FIXME(#12795) depends on lstat to work on windows
+    #[cfg(not(windows))]
+    #[test]
+    fn recursive_rmdir() {
+        let tmpdir = tmpdir();
+        let d1 = tmpdir.join("d1");
+        let dt = d1.join("t");
+        let dtt = dt.join("t");
+        let d2 = tmpdir.join("d2");
+        let canary = d2.join("do_not_delete");
+        check!(fs::create_dir_all(&dtt));
+        check!(fs::create_dir_all(&d2));
+        check!(check!(File::create(&canary)).write(b"foo"));
+        check!(fs::soft_link(&d2, &dt.join("d2")));
+        check!(fs::remove_dir_all(&d1));
+
+        assert!(!d1.is_dir());
+        assert!(canary.exists());
+    }
+
+    #[test]
+    fn unicode_path_is_dir() {
+        assert!(Path2::new(".").is_dir());
+        assert!(!Path2::new("test/stdtest/fs.rs").is_dir());
+
+        let tmpdir = tmpdir();
+
+        let mut dirpath = tmpdir.path().to_path_buf();
+        dirpath.push(&format!("test-가一ー你好"));
+        check!(fs::create_dir(&dirpath));
+        assert!(dirpath.is_dir());
+
+        let mut filepath = dirpath;
+        filepath.push("unicode-file-\u{ac00}\u{4e00}\u{30fc}\u{4f60}\u{597d}.rs");
+        check!(File::create(&filepath)); // ignore return; touch only
+        assert!(!filepath.is_dir());
+        assert!(filepath.exists());
+    }
+
+    #[test]
+    fn unicode_path_exists() {
+        assert!(Path2::new(".").exists());
+        assert!(!Path2::new("test/nonexistent-bogus-path").exists());
+
+        let tmpdir = tmpdir();
+        let unicode = tmpdir.path();
+        let unicode = unicode.join(&format!("test-각丁ー再见"));
+        check!(fs::create_dir(&unicode));
+        assert!(unicode.exists());
+        assert!(!Path2::new("test/unicode-bogus-path-각丁ー再见").exists());
+    }
+
+    #[test]
+    fn copy_file_does_not_exist() {
+        let from = Path2::new("test/nonexistent-bogus-path");
+        let to = Path2::new("test/other-bogus-path");
+
+        match fs::copy(&from, &to) {
+            Ok(..) => panic!(),
+            Err(..) => {
+                assert!(!from.exists());
+                assert!(!to.exists());
+            }
+        }
+    }
+
+    #[test]
+    fn copy_file_ok() {
+        let tmpdir = tmpdir();
+        let input = tmpdir.join("in.txt");
+        let out = tmpdir.join("out.txt");
+
+        check!(check!(File::create(&input)).write(b"hello"));
+        check!(fs::copy(&input, &out));
+        let mut v = Vec::new();
+        check!(check!(File::open(&out)).read_to_end(&mut v));
+        assert_eq!(v.as_slice(), b"hello");
+
+        assert_eq!(check!(input.metadata()).permissions(),
+                   check!(out.metadata()).permissions());
+    }
+
+    #[test]
+    fn copy_file_dst_dir() {
+        let tmpdir = tmpdir();
+        let out = tmpdir.join("out");
+
+        check!(File::create(&out));
+        match fs::copy(&*out, tmpdir.path()) {
+            Ok(..) => panic!(), Err(..) => {}
+        }
+    }
+
+    #[test]
+    fn copy_file_dst_exists() {
+        let tmpdir = tmpdir();
+        let input = tmpdir.join("in");
+        let output = tmpdir.join("out");
+
+        check!(check!(File::create(&input)).write("foo".as_bytes()));
+        check!(check!(File::create(&output)).write("bar".as_bytes()));
+        check!(fs::copy(&input, &output));
+
+        let mut v = Vec::new();
+        check!(check!(File::open(&output)).read_to_end(&mut v));
+        assert_eq!(v, b"foo".to_vec());
+    }
+
+    #[test]
+    fn copy_file_src_dir() {
+        let tmpdir = tmpdir();
+        let out = tmpdir.join("out");
+
+        match fs::copy(tmpdir.path(), &out) {
+            Ok(..) => panic!(), Err(..) => {}
+        }
+        assert!(!out.exists());
+    }
+
+    #[test]
+    fn copy_file_preserves_perm_bits() {
+        let tmpdir = tmpdir();
+        let input = tmpdir.join("in.txt");
+        let out = tmpdir.join("out.txt");
+
+        let attr = check!(check!(File::create(&input)).metadata());
+        let mut p = attr.permissions();
+        p.set_readonly(true);
+        check!(fs::set_permissions(&input, p));
+        check!(fs::copy(&input, &out));
+        assert!(check!(out.metadata()).permissions().readonly());
+    }
+
+    #[cfg(not(windows))] // FIXME(#10264) operation not permitted?
+    #[test]
+    fn symlinks_work() {
+        let tmpdir = tmpdir();
+        let input = tmpdir.join("in.txt");
+        let out = tmpdir.join("out.txt");
+
+        check!(check!(File::create(&input)).write("foobar".as_bytes()));
+        check!(fs::soft_link(&input, &out));
+        // if cfg!(not(windows)) {
+        //     assert_eq!(check!(lstat(&out)).kind, FileType::Symlink);
+        //     assert_eq!(check!(out.lstat()).kind, FileType::Symlink);
+        // }
+        assert_eq!(check!(fs::metadata(&out)).len(),
+                   check!(fs::metadata(&input)).len());
+        let mut v = Vec::new();
+        check!(check!(File::open(&out)).read_to_end(&mut v));
+        assert_eq!(v, b"foobar".to_vec());
+    }
+
+    #[cfg(not(windows))] // apparently windows doesn't like symlinks
+    #[test]
+    fn symlink_noexist() {
+        let tmpdir = tmpdir();
+        // symlinks can point to things that don't exist
+        check!(fs::soft_link(&tmpdir.join("foo"), &tmpdir.join("bar")));
+        assert_eq!(check!(fs::read_link(&tmpdir.join("bar"))),
+                   tmpdir.join("foo"));
+    }
+
+    #[test]
+    fn readlink_not_symlink() {
+        let tmpdir = tmpdir();
+        match fs::read_link(tmpdir.path()) {
+            Ok(..) => panic!("wanted a failure"),
+            Err(..) => {}
+        }
+    }
+
+    #[test]
+    fn links_work() {
+        let tmpdir = tmpdir();
+        let input = tmpdir.join("in.txt");
+        let out = tmpdir.join("out.txt");
+
+        check!(check!(File::create(&input)).write("foobar".as_bytes()));
+        check!(fs::hard_link(&input, &out));
+        assert_eq!(check!(fs::metadata(&out)).len(),
+                   check!(fs::metadata(&input)).len());
+        assert_eq!(check!(fs::metadata(&out)).len(),
+                   check!(input.metadata()).len());
+        let mut v = Vec::new();
+        check!(check!(File::open(&out)).read_to_end(&mut v));
+        assert_eq!(v, b"foobar".to_vec());
+
+        // can't link to yourself
+        match fs::hard_link(&input, &input) {
+            Ok(..) => panic!("wanted a failure"),
+            Err(..) => {}
+        }
+        // can't link to something that doesn't exist
+        match fs::hard_link(&tmpdir.join("foo"), &tmpdir.join("bar")) {
+            Ok(..) => panic!("wanted a failure"),
+            Err(..) => {}
+        }
+    }
+
+    #[test]
+    fn chmod_works() {
+        let tmpdir = tmpdir();
+        let file = tmpdir.join("in.txt");
+
+        check!(File::create(&file));
+        let attr = check!(fs::metadata(&file));
+        assert!(!attr.permissions().readonly());
+        let mut p = attr.permissions();
+        p.set_readonly(true);
+        check!(fs::set_permissions(&file, p.clone()));
+        let attr = check!(fs::metadata(&file));
+        assert!(attr.permissions().readonly());
+
+        match fs::set_permissions(&tmpdir.join("foo"), p) {
+            Ok(..) => panic!("wanted a panic"),
+            Err(..) => {}
+        }
+    }
+
+    #[test]
+    fn sync_doesnt_kill_anything() {
+        let tmpdir = tmpdir();
+        let path = tmpdir.join("in.txt");
+
+        let mut file = check!(File::create(&path));
+        check!(file.sync_all());
+        check!(file.sync_data());
+        check!(file.write(b"foo"));
+        check!(file.sync_all());
+        check!(file.sync_data());
+    }
+
+    #[test]
+    fn truncate_works() {
+        let tmpdir = tmpdir();
+        let path = tmpdir.join("in.txt");
+
+        let mut file = check!(File::create(&path));
+        check!(file.write(b"foo"));
+        check!(file.sync_all());
+
+        // Do some simple things with truncation
+        assert_eq!(check!(file.metadata()).len(), 3);
+        check!(file.set_len(10));
+        assert_eq!(check!(file.metadata()).len(), 10);
+        check!(file.write(b"bar"));
+        check!(file.sync_all());
+        assert_eq!(check!(file.metadata()).len(), 10);
+
+        let mut v = Vec::new();
+        check!(check!(File::open(&path)).read_to_end(&mut v));
+        assert_eq!(v, b"foobar\0\0\0\0".to_vec());
+
+        // Truncate to a smaller length, don't seek, and then write something.
+        // Ensure that the intermediate zeroes are all filled in (we're seeked
+        // past the end of the file).
+        check!(file.set_len(2));
+        assert_eq!(check!(file.metadata()).len(), 2);
+        check!(file.write(b"wut"));
+        check!(file.sync_all());
+        assert_eq!(check!(file.metadata()).len(), 9);
+        let mut v = Vec::new();
+        check!(check!(File::open(&path)).read_to_end(&mut v));
+        assert_eq!(v, b"fo\0\0\0\0wut".to_vec());
+    }
+
+    #[test]
+    fn open_flavors() {
+        use fs::OpenOptions as OO;
+        fn c<T: Clone>(t: &T) -> T { t.clone() }
+
+        let tmpdir = tmpdir();
+
+        let mut r = OO::new(); r.read(true);
+        let mut w = OO::new(); w.write(true);
+        let mut rw = OO::new(); rw.write(true).read(true);
+
+        match r.open(&tmpdir.join("a")) {
+            Ok(..) => panic!(), Err(..) => {}
+        }
+
+        // Perform each one twice to make sure that it succeeds the second time
+        // (where the file exists)
+        check!(c(&w).create(true).open(&tmpdir.join("b")));
+        assert!(tmpdir.join("b").exists());
+        check!(c(&w).create(true).open(&tmpdir.join("b")));
+        check!(w.open(&tmpdir.join("b")));
+
+        check!(c(&rw).create(true).open(&tmpdir.join("c")));
+        assert!(tmpdir.join("c").exists());
+        check!(c(&rw).create(true).open(&tmpdir.join("c")));
+        check!(rw.open(&tmpdir.join("c")));
+
+        check!(c(&w).append(true).create(true).open(&tmpdir.join("d")));
+        assert!(tmpdir.join("d").exists());
+        check!(c(&w).append(true).create(true).open(&tmpdir.join("d")));
+        check!(c(&w).append(true).open(&tmpdir.join("d")));
+
+        check!(c(&rw).append(true).create(true).open(&tmpdir.join("e")));
+        assert!(tmpdir.join("e").exists());
+        check!(c(&rw).append(true).create(true).open(&tmpdir.join("e")));
+        check!(c(&rw).append(true).open(&tmpdir.join("e")));
+
+        check!(c(&w).truncate(true).create(true).open(&tmpdir.join("f")));
+        assert!(tmpdir.join("f").exists());
+        check!(c(&w).truncate(true).create(true).open(&tmpdir.join("f")));
+        check!(c(&w).truncate(true).open(&tmpdir.join("f")));
+
+        check!(c(&rw).truncate(true).create(true).open(&tmpdir.join("g")));
+        assert!(tmpdir.join("g").exists());
+        check!(c(&rw).truncate(true).create(true).open(&tmpdir.join("g")));
+        check!(c(&rw).truncate(true).open(&tmpdir.join("g")));
+
+        check!(check!(File::create(&tmpdir.join("h"))).write("foo".as_bytes()));
+        check!(r.open(&tmpdir.join("h")));
+        {
+            let mut f = check!(r.open(&tmpdir.join("h")));
+            assert!(f.write("wut".as_bytes()).is_err());
+        }
+        assert_eq!(check!(fs::metadata(&tmpdir.join("h"))).len(), 3);
+        {
+            let mut f = check!(c(&w).append(true).open(&tmpdir.join("h")));
+            check!(f.write("bar".as_bytes()));
+        }
+        assert_eq!(check!(fs::metadata(&tmpdir.join("h"))).len(), 6);
+        {
+            let mut f = check!(c(&w).truncate(true).open(&tmpdir.join("h")));
+            check!(f.write("bar".as_bytes()));
+        }
+        assert_eq!(check!(fs::metadata(&tmpdir.join("h"))).len(), 3);
+    }
+
+    #[test]
+    fn utime() {
+        let tmpdir = tmpdir();
+        let path = tmpdir.join("a");
+        check!(File::create(&path));
+        // These numbers have to be bigger than the time in the day to account
+        // for timezones Windows in particular will fail in certain timezones
+        // with small enough values
+        check!(fs::set_file_times(&path, 100000, 200000));
+        assert_eq!(check!(path.metadata()).accessed(), 100000);
+        assert_eq!(check!(path.metadata()).modified(), 200000);
+    }
+
+    #[test]
+    fn utime_noexist() {
+        let tmpdir = tmpdir();
+
+        match fs::set_file_times(&tmpdir.join("a"), 100, 200) {
+            Ok(..) => panic!(),
+            Err(..) => {}
+        }
+    }
+
+    #[test]
+    fn binary_file() {
+        let mut bytes = [0; 1024];
+        StdRng::new().ok().unwrap().fill_bytes(&mut bytes);
+
+        let tmpdir = tmpdir();
+
+        check!(check!(File::create(&tmpdir.join("test"))).write(&bytes));
+        let mut v = Vec::new();
+        check!(check!(File::open(&tmpdir.join("test"))).read_to_end(&mut v));
+        assert!(v == bytes.as_slice());
+    }
+
+    #[test]
+    fn unlink_readonly() {
+        let tmpdir = tmpdir();
+        let path = tmpdir.join("file");
+        check!(File::create(&path));
+        let mut perm = check!(fs::metadata(&path)).permissions();
+        perm.set_readonly(true);
+        check!(fs::set_permissions(&path, perm));
+        check!(fs::remove_file(&path));
+    }
+}
diff --git a/src/libstd/fs/tempdir.rs b/src/libstd/fs/tempdir.rs
new file mode 100644
index 00000000000..79bdb35dd48
--- /dev/null
+++ b/src/libstd/fs/tempdir.rs
@@ -0,0 +1,125 @@
+// Copyright 2015 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#![unstable(feature = "tempdir", reason = "needs an RFC before stabilization")]
+
+use prelude::v1::*;
+
+use env;
+use io::{self, Error, ErrorKind};
+use fs;
+use path::{self, PathBuf, AsPath};
+use rand::{thread_rng, Rng};
+
+/// A wrapper for a path to temporary directory implementing automatic
+/// scope-based deletion.
+pub struct TempDir {
+    path: Option<PathBuf>,
+}
+
+// How many times should we (re)try finding an unused random name? It should be
+// enough that an attacker will run out of luck before we run out of patience.
+const NUM_RETRIES: u32 = 1 << 31;
+// How many characters should we include in a random file name? It needs to
+// be enough to dissuade an attacker from trying to preemptively create names
+// of that length, but not so huge that we unnecessarily drain the random number
+// generator of entropy.
+const NUM_RAND_CHARS: uint = 12;
+
+impl TempDir {
+    /// Attempts to make a temporary directory inside of `tmpdir` whose name
+    /// will have the prefix `prefix`. The directory will be automatically
+    /// deleted once the returned wrapper is destroyed.
+    ///
+    /// If no directory can be created, `Err` is returned.
+    #[allow(deprecated)] // rand usage
+    pub fn new_in<P: AsPath + ?Sized>(tmpdir: &P, prefix: &str)
+                                      -> io::Result<TempDir> {
+        let storage;
+        let mut tmpdir = tmpdir.as_path();
+        if !tmpdir.is_absolute() {
+            let cur_dir = try!(env::current_dir());
+            storage = cur_dir.join(tmpdir);
+            tmpdir = &storage;
+            // return TempDir::new_in(&cur_dir.join(tmpdir), prefix);
+        }
+
+        let mut rng = thread_rng();
+        for _ in 0..NUM_RETRIES {
+            let suffix: String = rng.gen_ascii_chars().take(NUM_RAND_CHARS).collect();
+            let leaf = if prefix.len() > 0 {
+                format!("{}.{}", prefix, suffix)
+            } else {
+                // If we're given an empty string for a prefix, then creating a
+                // directory starting with "." would lead to it being
+                // semi-invisible on some systems.
+                suffix
+            };
+            let path = tmpdir.join(&leaf);
+            match fs::create_dir(&path) {
+                Ok(_) => return Ok(TempDir { path: Some(path) }),
+                Err(ref e) if e.kind() == ErrorKind::PathAlreadyExists => {}
+                Err(e) => return Err(e)
+            }
+        }
+
+        Err(Error::new(ErrorKind::PathAlreadyExists,
+                       "too many temporary directories already exist",
+                       None))
+    }
+
+    /// Attempts to make a temporary directory inside of `env::temp_dir()` whose
+    /// name will have the prefix `prefix`. The directory will be automatically
+    /// deleted once the returned wrapper is destroyed.
+    ///
+    /// If no directory can be created, `Err` is returned.
+    #[allow(deprecated)]
+    pub fn new(prefix: &str) -> io::Result<TempDir> {
+        TempDir::new_in(&env::temp_dir(), prefix)
+    }
+
+    /// Unwrap the wrapped `std::path::Path` from the `TempDir` wrapper.
+    /// This discards the wrapper so that the automatic deletion of the
+    /// temporary directory is prevented.
+    pub fn into_path(mut self) -> PathBuf {
+        self.path.take().unwrap()
+    }
+
+    /// Access the wrapped `std::path::Path` to the temporary directory.
+    pub fn path(&self) -> &path::Path {
+        self.path.as_ref().unwrap()
+    }
+
+    /// Close and remove the temporary directory
+    ///
+    /// Although `TempDir` removes the directory on drop, in the destructor
+    /// any errors are ignored. To detect errors cleaning up the temporary
+    /// directory, call `close` instead.
+    pub fn close(mut self) -> io::Result<()> {
+        self.cleanup_dir()
+    }
+
+    fn cleanup_dir(&mut self) -> io::Result<()> {
+        match self.path {
+            Some(ref p) => fs::remove_dir_all(p),
+            None => Ok(())
+        }
+    }
+}
+
+impl Drop for TempDir {
+    fn drop(&mut self) {
+        let _ = self.cleanup_dir();
+    }
+}
+
+// the tests for this module need to change the path using change_dir,
+// and this doesn't play nicely with other tests so these unit tests are located
+// in src/test/run-pass/tempfile.rs