Stabilize std::path

This commit stabilizes essentially all of the new `std::path` API. The
API itself is changed in a couple of ways (which brings it in closer
alignment with the RFC):

* `.` components are now normalized away, unless they appear at the
  start of a path. This in turn effects the semantics of e.g. asking for
  the file name of `foo/` or `foo/.`, both of which yield `Some("foo")`
  now. This semantics is what the original RFC specified, and is also
  desirable given early experience rolling out the new API.

* The `parent` function now succeeds if, and only if, the path has at
  least one non-root/prefix component. This change affects `pop` as
  well.

* The `Prefix` component now involves a separate `PrefixComponent`
  struct, to better allow for keeping both parsed and unparsed prefix data.

In addition, the `old_path` module is now deprecated.

Closes #23264

[breaking-change]

1 files changed, 3 insertions, 2 deletions

diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index b2ef04a5d63..c90ddb3096a 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -18,6 +18,7 @@
 
 use prelude::v1::*;
 
+use iter::IntoIterator;
 use error::Error;
 use ffi::{OsString, AsOsStr};
 use fmt;
@@ -338,9 +339,9 @@ pub struct JoinPathsError {
 /// ```
 #[stable(feature = "env", since = "1.0.0")]
 pub fn join_paths<I, T>(paths: I) -> Result<OsString, JoinPathsError>
-    where I: Iterator<Item=T>, T: AsOsStr
+    where I: IntoIterator<Item=T>, T: AsOsStr
 {
-    os_imp::join_paths(paths).map_err(|e| {
+    os_imp::join_paths(paths.into_iter()).map_err(|e| {
         JoinPathsError { inner: e }
     })
 }