Auto merge of #50807 - kennytm:rollup, r=kennytm

Rollup of 17 pull requests

Successful merges:

 - #50170 (Implement From for more types on Cow)
 - #50638 (Don't unconditionally set CLOEXEC twice on every fd we open on Linux)
 - #50656 (Fix `fn main() -> impl Trait` for non-`Termination` trait)
 - #50669 (rustdoc: deprecate `#![doc(passes, plugins, no_default_passes)]`)
 - #50726 (read2: Use inner function instead of closure)
 - #50728 (Fix rustdoc panic with `impl Trait` in type parameters)
 - #50736 (env: remove unwrap in examples in favor of try op)
 - #50740 (Remove LazyBTreeMap.)
 - #50752 (Add missing error codes in libsyntax-ext asm)
 - #50779 (Make mutable_noalias and arg_align_attributes be tracked)
 - #50787 (Fix run-make wasm tests)
 - #50788 (Fix an ICE when casting a nonexistent const)
 - #50789 (Ensure libraries built in stage0 have unique metadata)
 - #50793 (tidy: Add a check for empty UI test files)
 - #50797 (fix a typo in signed-integer::from_str_radix())
 - #50808 (Stabilize num::NonZeroU*)
 - #50809 (GitHub: Stop treating Cargo.lock as a generated file.)

Failed merges:

3 files changed, 15 insertions, 1 deletions

diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index bb78c14b905..f7dd9d4f010 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -102,7 +102,6 @@
 #![feature(lang_items)]
 #![feature(libc)]
 #![feature(needs_allocator)]
-#![feature(nonzero)]
 #![feature(optin_builtin_traits)]
 #![feature(pattern)]
 #![feature(pin)]
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index da9afdd2ca3..449e3152d8f 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -2240,6 +2240,14 @@ impl<'a> From<String> for Cow<'a, str> {
     }
 }
 
+#[stable(feature = "cow_from_string_ref", since = "1.28.0")]
+impl<'a> From<&'a String> for Cow<'a, str> {
+    #[inline]
+    fn from(s: &'a String) -> Cow<'a, str> {
+        Cow::Borrowed(s.as_str())
+    }
+}
+
 #[stable(feature = "cow_str_from_iter", since = "1.12.0")]
 impl<'a> FromIterator<char> for Cow<'a, str> {
     fn from_iter<I: IntoIterator<Item = char>>(it: I) -> Cow<'a, str> {
diff --git a/src/liballoc/vec.rs b/src/liballoc/vec.rs
index 690cbcb559b..d30f8cd0fca 100644
--- a/src/liballoc/vec.rs
+++ b/src/liballoc/vec.rs
@@ -2286,6 +2286,13 @@ impl<'a, T: Clone> From<Vec<T>> for Cow<'a, [T]> {
     }
 }
 
+#[stable(feature = "cow_from_vec_ref", since = "1.28.0")]
+impl<'a, T: Clone> From<&'a Vec<T>> for Cow<'a, [T]> {
+    fn from(v: &'a Vec<T>) -> Cow<'a, [T]> {
+        Cow::Borrowed(v.as_slice())
+    }
+}
+
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<'a, T> FromIterator<T> for Cow<'a, [T]> where T: Clone {
     fn from_iter<I: IntoIterator<Item = T>>(it: I) -> Cow<'a, [T]> {