std: Remove ?Sized bounds from many I/O functions

It is a frequent pattern among I/O functions to take `P: AsPath + ?Sized` or
`AsOsStr` instead of `AsPath`. Most of these functions do not need to take
ownership of their argument, but for libraries in general it's much more
ergonomic to not deal with `?Sized` at all and simply require an argument `P`
instead of `&P`.

This change is aimed at removing unsightly `?Sized` bounds while retaining the
same level of usability as before. All affected functions now take ownership of
their arguments instead of taking them by reference, but due to the forwarding
implementations of `AsOsStr` and `AsPath` all code should continue to work as it
did before.

This is strictly speaking a breaking change due to the signatures of these
functions changing, but normal idiomatic usage of these APIs should not break in
practice.

[breaking-change]

1 files changed, 20 insertions, 24 deletions

diff --git a/src/libstd/fs/mod.rs b/src/libstd/fs/mod.rs
index ac1f5993aa1..d072d1f102b 100644
--- a/src/libstd/fs/mod.rs
+++ b/src/libstd/fs/mod.rs
@@ -124,7 +124,7 @@ impl File {
     /// This function will return an error if `path` does not already exist.
     /// Other errors may also be returned according to `OpenOptions::open`.
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn open<P: AsPath + ?Sized>(path: &P) -> io::Result<File> {
+    pub fn open<P: AsPath>(path: P) -> io::Result<File> {
         OpenOptions::new().read(true).open(path)
     }
 
@@ -135,7 +135,7 @@ impl File {
     ///
     /// See the `OpenOptions::open` function for more details.
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn create<P: AsPath + ?Sized>(path: &P) -> io::Result<File> {
+    pub fn create<P: AsPath>(path: P) -> io::Result<File> {
         OpenOptions::new().write(true).create(true).truncate(true).open(path)
     }
 
@@ -297,7 +297,7 @@ impl OpenOptions {
     ///   permissions for
     /// * Filesystem-level errors (full disk, etc)
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn open<P: AsPath + ?Sized>(&self, path: &P) -> io::Result<File> {
+    pub fn open<P: AsPath>(&self, path: P) -> io::Result<File> {
         let path = path.as_path();
         let inner = try!(fs_imp::File::open(path, &self.0));
         Ok(File { path: path.to_path_buf(), inner: inner })
@@ -410,7 +410,7 @@ impl DirEntry {
 /// user lacks permissions to remove the file, or if some other filesystem-level
 /// error occurs.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn remove_file<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+pub fn remove_file<P: AsPath>(path: P) -> io::Result<()> {
     fs_imp::unlink(path.as_path())
 }
 
@@ -438,7 +438,7 @@ pub fn remove_file<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
 /// permissions to perform a `metadata` call on the given `path` or if there
 /// is no entry in the filesystem at the provided path.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn metadata<P: AsPath + ?Sized>(path: &P) -> io::Result<Metadata> {
+pub fn metadata<P: AsPath>(path: P) -> io::Result<Metadata> {
     fs_imp::stat(path.as_path()).map(Metadata)
 }
 
@@ -459,8 +459,7 @@ pub fn metadata<P: AsPath + ?Sized>(path: &P) -> io::Result<Metadata> {
 /// reside on separate filesystems, or if some other intermittent I/O error
 /// occurs.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn rename<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
-                                                      -> io::Result<()> {
+pub fn rename<P: AsPath, Q: AsPath>(from: P, to: Q) -> io::Result<()> {
     fs_imp::rename(from.as_path(), to.as_path())
 }
 
@@ -490,9 +489,9 @@ pub fn rename<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
 /// * The current process does not have the permission rights to access
 ///   `from` or write `to`
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn copy<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
-                                                    -> io::Result<u64> {
+pub fn copy<P: AsPath, Q: AsPath>(from: P, to: Q) -> io::Result<u64> {
     let from = from.as_path();
+    let to = to.as_path();
     if !from.is_file() {
         return Err(Error::new(ErrorKind::MismatchedFileTypeForOperation,
                               "the source path is not an existing file",
@@ -513,8 +512,7 @@ pub fn copy<P: AsPath + ?Sized, Q: AsPath + ?Sized>(from: &P, to: &Q)
 /// 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.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn hard_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
-                                                         -> io::Result<()> {
+pub fn hard_link<P: AsPath, Q: AsPath>(src: P, dst: Q) -> io::Result<()> {
     fs_imp::link(src.as_path(), dst.as_path())
 }
 
@@ -522,8 +520,7 @@ pub fn hard_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
 ///
 /// The `dst` path will be a soft link pointing to the `src` path.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn soft_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
-                                                         -> io::Result<()> {
+pub fn soft_link<P: AsPath, Q: AsPath>(src: P, dst: Q) -> io::Result<()> {
     fs_imp::symlink(src.as_path(), dst.as_path())
 }
 
@@ -535,7 +532,7 @@ pub fn soft_link<P: AsPath + ?Sized, Q: AsPath + ?Sized>(src: &P, dst: &Q)
 /// reading a file that does not exist or reading a file that is not a soft
 /// link.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn read_link<P: AsPath + ?Sized>(path: &P) -> io::Result<PathBuf> {
+pub fn read_link<P: AsPath>(path: P) -> io::Result<PathBuf> {
     fs_imp::readlink(path.as_path())
 }
 
@@ -554,7 +551,7 @@ pub fn read_link<P: AsPath + ?Sized>(path: &P) -> io::Result<PathBuf> {
 /// 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.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn create_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+pub fn create_dir<P: AsPath>(path: P) -> io::Result<()> {
     fs_imp::mkdir(path.as_path())
 }
 
@@ -568,7 +565,7 @@ pub fn create_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
 /// error conditions for when a directory is being created (after it is
 /// determined to not exist) are outlined by `fs::create_dir`.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn create_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+pub fn create_dir_all<P: AsPath>(path: P) -> io::Result<()> {
     let path = path.as_path();
     if path.is_dir() { return Ok(()) }
     if let Some(p) = path.parent() { try!(create_dir_all(p)) }
@@ -590,7 +587,7 @@ pub fn create_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
 /// 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.
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn remove_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+pub fn remove_dir<P: AsPath>(path: P) -> io::Result<()> {
     fs_imp::rmdir(path.as_path())
 }
 
@@ -604,7 +601,7 @@ pub fn remove_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
 ///
 /// See `file::remove_file` and `fs::remove_dir`
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn remove_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
+pub fn remove_dir_all<P: AsPath>(path: P) -> io::Result<()> {
     let path = path.as_path();
     for child in try!(read_dir(path)) {
         let child = try!(child).path();
@@ -657,7 +654,7 @@ pub fn remove_dir_all<P: AsPath + ?Sized>(path: &P) -> io::Result<()> {
 /// the process lacks permissions to view the contents or if the `path` points
 /// at a non-directory file
 #[stable(feature = "rust1", since = "1.0.0")]
-pub fn read_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<ReadDir> {
+pub fn read_dir<P: AsPath>(path: P) -> io::Result<ReadDir> {
     fs_imp::readdir(path.as_path()).map(ReadDir)
 }
 
@@ -673,7 +670,7 @@ pub fn read_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<ReadDir> {
            reason = "the precise semantics and defaults for a recursive walk \
                      may change and this may end up accounting for files such \
                      as symlinks differently")]
-pub fn walk_dir<P: AsPath + ?Sized>(path: &P) -> io::Result<WalkDir> {
+pub fn walk_dir<P: AsPath>(path: P) -> io::Result<WalkDir> {
     let start = try!(read_dir(path));
     Ok(WalkDir { cur: Some(start), stack: Vec::new() })
 }
@@ -759,8 +756,8 @@ impl PathExt for Path {
            reason = "the argument type of u64 is not quite appropriate for \
                      this function and may change if the standard library \
                      gains a type to represent a moment in time")]
-pub fn set_file_times<P: AsPath + ?Sized>(path: &P, accessed: u64,
-                                          modified: u64) -> io::Result<()> {
+pub fn set_file_times<P: AsPath>(path: P, accessed: u64,
+                                 modified: u64) -> io::Result<()> {
     fs_imp::utimes(path.as_path(), accessed, modified)
 }
 
@@ -788,8 +785,7 @@ pub fn set_file_times<P: AsPath + ?Sized>(path: &P, accessed: u64,
            reason = "a more granual ability to set specific permissions may \
                      be exposed on the Permissions structure itself and this \
                      method may not always exist")]
-pub fn set_permissions<P: AsPath + ?Sized>(path: &P, perm: Permissions)
-                                           -> io::Result<()> {
+pub fn set_permissions<P: AsPath>(path: P, perm: Permissions) -> io::Result<()> {
     fs_imp::set_perm(path.as_path(), perm.0)
 }