Auto merge of #42856 - Mark-Simulacrum:rollup, r=Mark-Simulacrum

Rollup of 8 pull requests

- Successful merges: #42777, #42783, #42787, #42821, #42822, #42825, #42829, #42833
- Failed merges:

8 files changed, 57 insertions, 19 deletions

diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index e75401f6ce0..1eebf67ad04 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -942,6 +942,13 @@ impl<'b, T: ?Sized> Ref<'b, T> {
 #[unstable(feature = "coerce_unsized", issue = "27732")]
 impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Ref<'b, U>> for Ref<'b, T> {}
 
+#[stable(feature = "std_guard_impls", since = "1.20")]
+impl<'a, T: ?Sized + fmt::Display> fmt::Display for Ref<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.value.fmt(f)
+    }
+}
+
 impl<'b, T: ?Sized> RefMut<'b, T> {
     /// Make a new `RefMut` for a component of the borrowed data, e.g. an enum
     /// variant.
@@ -1034,6 +1041,13 @@ impl<'b, T: ?Sized> DerefMut for RefMut<'b, T> {
 #[unstable(feature = "coerce_unsized", issue = "27732")]
 impl<'b, T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<RefMut<'b, U>> for RefMut<'b, T> {}
 
+#[stable(feature = "std_guard_impls", since = "1.20")]
+impl<'a, T: ?Sized + fmt::Display> fmt::Display for RefMut<'a, T> {
+    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+        self.value.fmt(f)
+    }
+}
+
 /// The core primitive for interior mutability in Rust.
 ///
 /// `UnsafeCell<T>` is a type that wraps some `T` and indicates unsafe interior operations on the
diff --git a/src/libcore/iter/mod.rs b/src/libcore/iter/mod.rs
index c91fd16391a..d6a9be4437d 100644
--- a/src/libcore/iter/mod.rs
+++ b/src/libcore/iter/mod.rs
@@ -211,7 +211,7 @@
 //! There's one more subtle bit here: the standard library contains an
 //! interesting implementation of [`IntoIterator`]:
 //!
-//! ```ignore
+//! ```ignore (only-for-syntax-highlight)
 //! impl<I: Iterator> IntoIterator for I
 //! ```
 //!
diff --git a/src/libcore/marker.rs b/src/libcore/marker.rs
index 3bed425943f..e8fd729b638 100644
--- a/src/libcore/marker.rs
+++ b/src/libcore/marker.rs
@@ -434,7 +434,7 @@ macro_rules! impls{
 /// example, here is a struct `Slice` that has two pointers of type `*const T`,
 /// presumably pointing into an array somewhere:
 ///
-/// ```ignore
+/// ```compile_fail,E0392
 /// struct Slice<'a, T> {
 ///     start: *const T,
 ///     end: *const T,
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 509b396f211..bba42752f50 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -328,11 +328,18 @@ pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
 ///
 /// Here's an example of how a collection might make use of needs_drop:
 ///
-/// ```ignore
+/// ```
 /// #![feature(needs_drop)]
 /// use std::{mem, ptr};
 ///
-/// pub struct MyCollection<T> { /* ... */ }
+/// pub struct MyCollection<T> {
+/// #   data: [T; 1],
+///     /* ... */
+/// }
+/// # impl<T> MyCollection<T> {
+/// #   fn iter_mut(&mut self) -> &mut [T] { &mut self.data }
+/// #   fn free_buffer(&mut self) {}
+/// # }
 ///
 /// impl<T> Drop for MyCollection<T> {
 ///     fn drop(&mut self) {
@@ -575,7 +582,7 @@ pub fn swap<T>(x: &mut T, y: &mut T) {
 /// `replace` allows consumption of a struct field by replacing it with another value.
 /// Without `replace` you can run into issues like these:
 ///
-/// ```ignore
+/// ```compile_fail,E0507
 /// struct Buffer<T> { buf: Vec<T> }
 ///
 /// impl<T> Buffer<T> {
@@ -645,7 +652,7 @@ pub fn replace<T>(dest: &mut T, mut src: T) -> T {
 ///
 /// Borrows are based on lexical scope, so this produces an error:
 ///
-/// ```ignore
+/// ```compile_fail,E0502
 /// let mut v = vec![1, 2, 3];
 /// let x = &v[0];
 ///
diff --git a/src/libcore/ops/place.rs b/src/libcore/ops/place.rs
index 996a741c96f..19da887cbbf 100644
--- a/src/libcore/ops/place.rs
+++ b/src/libcore/ops/place.rs
@@ -38,7 +38,13 @@ pub trait Place<Data: ?Sized> {
 ///
 /// `PLACE <- EXPR` effectively desugars into:
 ///
-/// ```rust,ignore
+/// ```
+/// # #![feature(placement_new_protocol, box_heap)]
+/// # use std::ops::{Placer, Place, InPlace};
+/// # #[allow(non_snake_case)]
+/// # fn main() {
+/// # let PLACE = std::boxed::HEAP;
+/// # let EXPR = 1;
 /// let p = PLACE;
 /// let mut place = Placer::make_place(p);
 /// let raw_place = Place::pointer(&mut place);
@@ -47,6 +53,7 @@ pub trait Place<Data: ?Sized> {
 ///     std::ptr::write(raw_place, value);
 ///     InPlace::finalize(place)
 /// }
+/// # ; }
 /// ```
 ///
 /// The type of `PLACE <- EXPR` is derived from the type of `PLACE`;
@@ -89,14 +96,21 @@ pub trait InPlace<Data: ?Sized>: Place<Data> {
 ///
 /// `box EXPR` effectively desugars into:
 ///
-/// ```rust,ignore
+/// ```
+/// # #![feature(placement_new_protocol)]
+/// # use std::ops::{BoxPlace, Place, Boxed};
+/// # #[allow(non_snake_case)]
+/// # fn main() {
+/// # let EXPR = 1;
 /// let mut place = BoxPlace::make_place();
 /// let raw_place = Place::pointer(&mut place);
 /// let value = EXPR;
+/// # let _: Box<_> =
 /// unsafe {
 ///     ::std::ptr::write(raw_place, value);
 ///     Boxed::finalize(place)
 /// }
+/// # ; }
 /// ```
 ///
 /// The type of `box EXPR` is supplied from its surrounding
diff --git a/src/libcore/ops/range.rs b/src/libcore/ops/range.rs
index 70c35df87dd..33258b7a875 100644
--- a/src/libcore/ops/range.rs
+++ b/src/libcore/ops/range.rs
@@ -26,7 +26,7 @@ use fmt;
 /// It does not have an `IntoIterator` implementation, so you can't use it in a
 /// `for` loop directly. This won't compile:
 ///
-/// ```ignore
+/// ```compile_fail,E0277
 /// for i in .. {
 ///    // ...
 /// }
@@ -184,7 +184,7 @@ impl<Idx: PartialOrd<Idx>> RangeFrom<Idx> {
 /// It does not have an `IntoIterator` implementation, so you can't use it in a
 /// `for` loop directly. This won't compile:
 ///
-/// ```ignore
+/// ```compile_fail,E0277
 /// for i in ..5 {
 ///     // ...
 /// }
@@ -313,7 +313,8 @@ impl<Idx: PartialOrd<Idx>> RangeInclusive<Idx> {
 /// It does not have an `IntoIterator` implementation, so you can't use it in a
 /// `for` loop directly. This won't compile:
 ///
-/// ```ignore
+/// ```compile_fail,E0277
+/// #![feature(inclusive_range_syntax)]
 /// for i in ...5 {
 ///     // ...
 /// }
diff --git a/src/libcore/panicking.rs b/src/libcore/panicking.rs
index 93ddfa72f63..60b7669f3b2 100644
--- a/src/libcore/panicking.rs
+++ b/src/libcore/panicking.rs
@@ -15,8 +15,10 @@
 //! useful an upstream crate must define panicking for libcore to use. The current
 //! interface for panicking is:
 //!
-//! ```ignore
-//! fn panic_impl(fmt: fmt::Arguments, &(&'static str, u32)) -> !;
+//! ```
+//! # use std::fmt;
+//! fn panic_impl(fmt: fmt::Arguments, file_line: &(&'static str, u32)) -> !
+//! # { loop {} }
 //! ```
 //!
 //! This definition allows for panicking with any general message, but it does not
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index f89f86e18a1..54ae9e0d628 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -408,11 +408,11 @@ impl<T: ?Sized> *const T {
     ///
     /// Basic usage:
     ///
-    /// ```ignore
-    /// let val: *const u8 = &10u8 as *const u8;
+    /// ```
+    /// let ptr: *const u8 = &10u8 as *const u8;
     ///
     /// unsafe {
-    ///     if let Some(val_back) = val.as_ref() {
+    ///     if let Some(val_back) = ptr.as_ref() {
     ///         println!("We got back the value: {}!", val_back);
     ///     }
     /// }
@@ -570,11 +570,11 @@ impl<T: ?Sized> *mut T {
     ///
     /// Basic usage:
     ///
-    /// ```ignore
-    /// let val: *mut u8 = &mut 10u8 as *mut u8;
+    /// ```
+    /// let ptr: *mut u8 = &mut 10u8 as *mut u8;
     ///
     /// unsafe {
-    ///     if let Some(val_back) = val.as_ref() {
+    ///     if let Some(val_back) = ptr.as_ref() {
     ///         println!("We got back the value: {}!", val_back);
     ///     }
     /// }