Auto merge of #52486 - kennytm:rollup, r=kennytm

Rollup of 13 pull requests

Successful merges:

 - #51628 (use checked write in `LineWriter` example)
 - #52116 (Handle array manually in str case conversion methods)
 - #52218 (Amend option.take examples)
 - #52418 (Do not use desugared ident when suggesting adding a type)
 - #52439 (Revert some changes from #51917 to fix custom libdir)
 - #52455 (Fix doc comment: use `?` instead of `.unwrap()`)
 - #52458 (rustc: Fix a suggestion for the `proc_macro` feature)
 - #52464 (Allow clippy to be installed with make install)
 - #52472 (rustc: Enable `use_extern_macros` in 2018 edition)
 - #52477 (Clarify short-circuiting behvaior of Iterator::zip.)
 - #52480 (Cleanup #24958)
 - #52487 (Don't build twice the sanitizers on Linux)
 - #52510 (rustdoc: remove FIXME about macro redirects)

Failed merges:

r? @ghost

3 files changed, 10 insertions, 3 deletions

diff --git a/src/libcore/iter/iterator.rs b/src/libcore/iter/iterator.rs
index c0681619bf8..afc273d265b 100644
--- a/src/libcore/iter/iterator.rs
+++ b/src/libcore/iter/iterator.rs
@@ -384,7 +384,9 @@ pub trait Iterator {
     ///
     /// In other words, it zips two iterators together, into a single one.
     ///
-    /// If either iterator returns [`None`], [`next`] will return [`None`].
+    /// If either iterator returns [`None`], [`next`] from the zipped iterator
+    /// will return [`None`]. If the first iterator returns [`None`], `zip` will
+    /// short-circuit and `next` will not be called on the second iterator.
     ///
     /// # Examples
     ///
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index f3e823670aa..9f9dbd0777a 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -833,12 +833,14 @@ impl<T> Option<T> {
     ///
     /// ```
     /// let mut x = Some(2);
-    /// x.take();
+    /// let y = x.take();
     /// assert_eq!(x, None);
+    /// assert_eq!(y, Some(2));
     ///
     /// let mut x: Option<u32> = None;
-    /// x.take();
+    /// let y = x.take();
     /// assert_eq!(x, None);
+    /// assert_eq!(y, None);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
diff --git a/src/libcore/unicode/mod.rs b/src/libcore/unicode/mod.rs
index b6b033adc04..e5cda880f88 100644
--- a/src/libcore/unicode/mod.rs
+++ b/src/libcore/unicode/mod.rs
@@ -20,6 +20,9 @@ pub(crate) mod version;
 pub mod derived_property {
     pub use unicode::tables::derived_property::{Case_Ignorable, Cased};
 }
+pub mod conversions {
+    pub use unicode::tables::conversions::{to_lower, to_upper};
+}
 
 // For use in libsyntax
 pub mod property {