Revise use of conversion traits

This commit revises `path` and `os_str` to use blanket impls for `From`
on reference types. This both cuts down on the number of required impls,
and means that you can pass through e.g. `T: AsRef<OsStr>` to
`PathBuf::from` without an intermediate call to `as_ref`.

It also makes a FIXME note for later generalizing the blanket impls for
`AsRef` and `AsMut` to use `Deref`/`DerefMut`, once it is possible to do
so.

1 files changed, 3 insertions, 17 deletions

diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index 5851c6e2998..24844ad0961 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -113,23 +113,9 @@ impl From<String> for OsString {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> From<&'a String> for OsString {
-    fn from(s: &'a String) -> OsString {
-        OsString { inner: Buf::from_str(s) }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> From<&'a str> for OsString {
-    fn from(s: &'a str) -> OsString {
-        OsString { inner: Buf::from_str(s) }
-    }
-}
-
-#[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> From<&'a OsStr> for OsString {
-    fn from(s: &'a OsStr) -> OsString {
-        OsString { inner: s.inner.to_owned() }
+impl<'a, T: ?Sized + AsRef<OsStr>> From<&'a T> for OsString {
+    fn from(s: &'a T) -> OsString {
+        s.as_ref().to_os_string()
     }
 }