Auto merge of #42130 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 6 pull requests

- Successful merges: #41892, #42062, #42091, #42093, #42098, #42127
- Failed merges:

7 files changed, 44 insertions, 26 deletions

diff --git a/src/libstd/collections/hash/table.rs b/src/libstd/collections/hash/table.rs
index a15269cc87c..50c721db849 100644
--- a/src/libstd/collections/hash/table.rs
+++ b/src/libstd/collections/hash/table.rs
@@ -12,9 +12,8 @@ use alloc::heap::{allocate, deallocate};
 
 use cmp;
 use hash::{BuildHasher, Hash, Hasher};
-use intrinsics::needs_drop;
 use marker;
-use mem::{align_of, size_of};
+use mem::{align_of, size_of, needs_drop};
 use mem;
 use ops::{Deref, DerefMut};
 use ptr::{self, Unique, Shared};
diff --git a/src/libstd/env.rs b/src/libstd/env.rs
index cba4cf25be4..27b40793ff6 100644
--- a/src/libstd/env.rs
+++ b/src/libstd/env.rs
@@ -13,6 +13,13 @@
 //! This module contains functions to inspect various aspects such as
 //! environment variables, process arguments, the current directory, and various
 //! other important directories.
+//!
+//! There are several functions and structs in this module that have a
+//! counterpart ending in `os`. Those ending in `os` will return an [`OsString`]
+//! and those without will be returning a [`String`].
+//!
+//! [`OsString`]: ../../std/ffi/struct.OsString.html
+//! [`String`]: ../string/struct.String.html
 
 #![stable(feature = "env", since = "1.0.0")]
 
@@ -74,7 +81,8 @@ pub fn set_current_dir<P: AsRef<Path>>(path: P) -> io::Result<()> {
 
 /// An iterator over a snapshot of the environment variables of this process.
 ///
-/// This structure is created through the [`std::env::vars`] function.
+/// This structure is created by the [`std::env::vars`] function. See its
+/// documentation for more.
 ///
 /// [`std::env::vars`]: fn.vars.html
 #[stable(feature = "env", since = "1.0.0")]
@@ -82,7 +90,8 @@ pub struct Vars { inner: VarsOs }
 
 /// An iterator over a snapshot of the environment variables of this process.
 ///
-/// This structure is created through the [`std::env::vars_os`] function.
+/// This structure is created by the [`std::env::vars_os`] function. See
+/// its documentation for more.
 ///
 /// [`std::env::vars_os`]: fn.vars_os.html
 #[stable(feature = "env", since = "1.0.0")]
@@ -176,12 +185,10 @@ impl fmt::Debug for VarsOs {
 
 /// Fetches the environment variable `key` from the current process.
 ///
-/// The returned result is [`Ok(s)`] if the environment variable is present and is
-/// valid unicode. If the environment variable is not present, or it is not
-/// valid unicode, then [`VarError`] will be returned.
+/// # Errors
 ///
-/// [`Ok(s)`]: ../result/enum.Result.html#variant.Ok
-/// [`VarError`]: enum.VarError.html
+/// * Environment variable is not present
+/// * Environment variable is not valid unicode
 ///
 /// # Examples
 ///
@@ -233,7 +240,8 @@ fn _var_os(key: &OsStr) -> Option<OsString> {
     })
 }
 
-/// Possible errors from the [`env::var`] function.
+/// The error type for operations interacting with environment variables.
+/// Possibly returned from the [`env::var`] function.
 ///
 /// [`env::var`]: fn.var.html
 #[derive(Debug, PartialEq, Eq, Clone)]
@@ -356,10 +364,13 @@ fn _remove_var(k: &OsStr) {
     })
 }
 
-/// An iterator over `PathBuf` instances for parsing an environment variable
-/// according to platform-specific conventions.
+/// An iterator that splits an environment variable into paths according to
+/// platform-specific conventions.
 ///
-/// This structure is returned from `std::env::split_paths`.
+/// This structure is created by the [`std::env::split_paths`] function See its
+/// documentation for more.
+///
+/// [`std::env::split_paths`]: fn.split_paths.html
 #[stable(feature = "env", since = "1.0.0")]
 pub struct SplitPaths<'a> { inner: os_imp::SplitPaths<'a> }
 
@@ -402,8 +413,10 @@ impl<'a> fmt::Debug for SplitPaths<'a> {
     }
 }
 
-/// Error type returned from `std::env::join_paths` when paths fail to be
-/// joined.
+/// The error type for operations on the `PATH` variable. Possibly returned from
+/// the [`env::join_paths`] function.
+///
+/// [`env::join_paths`]: fn.join_paths.html
 #[derive(Debug)]
 #[stable(feature = "env", since = "1.0.0")]
 pub struct JoinPathsError {
@@ -413,7 +426,7 @@ pub struct JoinPathsError {
 /// Joins a collection of [`Path`]s appropriately for the `PATH`
 /// environment variable.
 ///
-/// Returns an [`OsString`] on success.
+/// # Errors
 ///
 /// Returns an [`Err`][err] (containing an error message) if one of the input
 /// [`Path`]s contains an invalid character for constructing the `PATH`
@@ -493,12 +506,16 @@ pub fn home_dir() -> Option<PathBuf> {
 
 /// Returns the path of a temporary directory.
 ///
-/// On Unix, returns the value of the `TMPDIR` environment variable if it is
+/// # Unix
+///
+/// Returns the value of the `TMPDIR` environment variable if it is
 /// set, otherwise for non-Android it returns `/tmp`. If Android, since there
 /// is no global temporary folder (it is usually allocated per-app), it returns
 /// `/data/local/tmp`.
 ///
-/// On Windows, returns the value of, in order, the `TMP`, `TEMP`,
+/// # Windows
+///
+/// Returns the value of, in order, the `TMP`, `TEMP`,
 /// `USERPROFILE` environment variable if any are set and not the empty
 /// string. Otherwise, `temp_dir` returns the path of the Windows directory.
 /// This behavior is identical to that of [`GetTempPath`][msdn], which this
diff --git a/src/libstd/ffi/os_str.rs b/src/libstd/ffi/os_str.rs
index eaf0502a577..f497734e249 100644
--- a/src/libstd/ffi/os_str.rs
+++ b/src/libstd/ffi/os_str.rs
@@ -530,7 +530,7 @@ impl<'a> From<&'a OsStr> for Box<OsStr> {
 }
 
 #[stable(feature = "os_string_from_box", since = "1.18.0")]
-impl<'a> From<Box<OsStr>> for OsString {
+impl From<Box<OsStr>> for OsString {
     fn from(boxed: Box<OsStr>) -> OsString {
         boxed.into_os_string()
     }
diff --git a/src/libstd/lib.rs b/src/libstd/lib.rs
index a4c3b276efd..b0820d6f05a 100644
--- a/src/libstd/lib.rs
+++ b/src/libstd/lib.rs
@@ -281,6 +281,7 @@
 #![feature(linkage)]
 #![feature(macro_reexport)]
 #![feature(needs_panic_runtime)]
+#![feature(needs_drop)]
 #![feature(never_type)]
 #![feature(num_bits_bytes)]
 #![feature(old_wrapping)]
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index e7d8c3007f6..e128a4164d7 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -1342,7 +1342,7 @@ impl<'a> From<&'a Path> for Box<Path> {
 }
 
 #[stable(feature = "path_buf_from_box", since = "1.18.0")]
-impl<'a> From<Box<Path>> for PathBuf {
+impl From<Box<Path>> for PathBuf {
     fn from(boxed: Box<Path>) -> PathBuf {
         boxed.into_path_buf()
     }
diff --git a/src/libstd/sys/redox/fast_thread_local.rs b/src/libstd/sys/redox/fast_thread_local.rs
index f6414673dac..7dc61ce6654 100644
--- a/src/libstd/sys/redox/fast_thread_local.rs
+++ b/src/libstd/sys/redox/fast_thread_local.rs
@@ -12,9 +12,10 @@
 #![unstable(feature = "thread_local_internals", issue = "0")]
 
 use cell::{Cell, UnsafeCell};
-use intrinsics;
+use mem;
 use ptr;
 
+
 pub struct Key<T> {
     inner: UnsafeCell<Option<T>>,
 
@@ -37,7 +38,7 @@ impl<T> Key<T> {
 
     pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
         unsafe {
-            if intrinsics::needs_drop::<T>() && self.dtor_running.get() {
+            if mem::needs_drop::<T>() && self.dtor_running.get() {
                 return None
             }
             self.register_dtor();
@@ -46,7 +47,7 @@ impl<T> Key<T> {
     }
 
     unsafe fn register_dtor(&self) {
-        if !intrinsics::needs_drop::<T>() || self.dtor_registered.get() {
+        if !mem::needs_drop::<T>() || self.dtor_registered.get() {
             return
         }
 
diff --git a/src/libstd/sys/unix/fast_thread_local.rs b/src/libstd/sys/unix/fast_thread_local.rs
index 07d76a93dd1..6b3973de84c 100644
--- a/src/libstd/sys/unix/fast_thread_local.rs
+++ b/src/libstd/sys/unix/fast_thread_local.rs
@@ -13,7 +13,7 @@
 
 use cell::{Cell, UnsafeCell};
 use fmt;
-use intrinsics;
+use mem;
 use ptr;
 
 pub struct Key<T> {
@@ -44,7 +44,7 @@ impl<T> Key<T> {
 
     pub fn get(&'static self) -> Option<&'static UnsafeCell<Option<T>>> {
         unsafe {
-            if intrinsics::needs_drop::<T>() && self.dtor_running.get() {
+            if mem::needs_drop::<T>() && self.dtor_running.get() {
                 return None
             }
             self.register_dtor();
@@ -53,7 +53,7 @@ impl<T> Key<T> {
     }
 
     unsafe fn register_dtor(&self) {
-        if !intrinsics::needs_drop::<T>() || self.dtor_registered.get() {
+        if !mem::needs_drop::<T>() || self.dtor_registered.get() {
             return
         }