Merging master

55 files changed, 700 insertions, 363 deletions

diff --git a/src/libcore/alloc.rs b/src/libcore/alloc.rs
index 66a3094d77d..f49e226a5cb 100644
--- a/src/libcore/alloc.rs
+++ b/src/libcore/alloc.rs
@@ -425,7 +425,7 @@ impl fmt::Display for CannotReallocInPlace {
 /// The `GlobalAlloc` trait is an `unsafe` trait for a number of reasons, and
 /// implementors must ensure that they adhere to these contracts:
 ///
-/// * It's undefined behavior if global allocators unwind.  This restriction may
+/// * It's undefined behavior if global allocators unwind. This restriction may
 ///   be lifted in the future, but currently a panic from any of these
 ///   functions may lead to memory unsafety.
 ///
diff --git a/src/libcore/any.rs b/src/libcore/any.rs
index 2afd9e0c072..01ab523a4c3 100644
--- a/src/libcore/any.rs
+++ b/src/libcore/any.rs
@@ -18,7 +18,7 @@
 //!
 //! Consider a situation where we want to log out a value passed to a function.
 //! We know the value we're working on implements Debug, but we don't know its
-//! concrete type.  We want to give special treatment to certain types: in this
+//! concrete type. We want to give special treatment to certain types: in this
 //! case printing out the length of String values prior to their value.
 //! We don't know the concrete type of our value at compile time, so we need to
 //! use runtime reflection instead.
@@ -31,8 +31,8 @@
 //! fn log<T: Any + Debug>(value: &T) {
 //!     let value_any = value as &dyn Any;
 //!
-//!     // try to convert our value to a String.  If successful, we want to
-//!     // output the String's length as well as its value.  If not, it's a
+//!     // Try to convert our value to a `String`. If successful, we want to
+//!     // output the String`'s length as well as its value. If not, it's a
 //!     // different type: just print it out unadorned.
 //!     match value_any.downcast_ref::<String>() {
 //!         Some(as_string) => {
diff --git a/src/libcore/cell.rs b/src/libcore/cell.rs
index d57ca13a334..8383d305518 100644
--- a/src/libcore/cell.rs
+++ b/src/libcore/cell.rs
@@ -130,7 +130,7 @@
 //!
 //! This is simply a special - but common - case of the previous: hiding mutability for operations
 //! that appear to be immutable. The `clone` method is expected to not change the source value, and
-//! is declared to take `&self`, not `&mut self`. Therefore any mutation that happens in the
+//! is declared to take `&self`, not `&mut self`. Therefore, any mutation that happens in the
 //! `clone` method must use cell types. For example, `Rc<T>` maintains its reference counts within a
 //! `Cell<T>`.
 //!
@@ -1133,7 +1133,7 @@ impl<'b, T: ?Sized> Ref<'b, T> {
     /// The `RefCell` is already immutably borrowed, so this cannot fail.
     ///
     /// This is an associated function that needs to be used as
-    /// `Ref::clone(...)`.  A `Clone` implementation or a method would interfere
+    /// `Ref::clone(...)`. A `Clone` implementation or a method would interfere
     /// with the widespread use of `r.borrow().clone()` to clone the contents of
     /// a `RefCell`.
     #[stable(feature = "cell_extras", since = "1.15.0")]
@@ -1145,7 +1145,7 @@ impl<'b, T: ?Sized> Ref<'b, T> {
         }
     }
 
-    /// Make a new `Ref` for a component of the borrowed data.
+    /// Makes a new `Ref` for a component of the borrowed data.
     ///
     /// The `RefCell` is already immutably borrowed, so this cannot fail.
     ///
@@ -1174,7 +1174,7 @@ impl<'b, T: ?Sized> Ref<'b, T> {
         }
     }
 
-    /// Split a `Ref` into multiple `Ref`s for different components of the
+    /// Splits a `Ref` into multiple `Ref`s for different components of the
     /// borrowed data.
     ///
     /// The `RefCell` is already immutably borrowed, so this cannot fail.
@@ -1217,13 +1217,13 @@ impl<T: ?Sized + fmt::Display> fmt::Display for Ref<'_, T> {
 }
 
 impl<'b, T: ?Sized> RefMut<'b, T> {
-    /// Make a new `RefMut` for a component of the borrowed data, e.g., an enum
+    /// Makes a new `RefMut` for a component of the borrowed data, e.g., an enum
     /// variant.
     ///
     /// The `RefCell` is already mutably borrowed, so this cannot fail.
     ///
     /// This is an associated function that needs to be used as
-    /// `RefMut::map(...)`.  A method would interfere with methods of the same
+    /// `RefMut::map(...)`. A method would interfere with methods of the same
     /// name on the contents of a `RefCell` used through `Deref`.
     ///
     /// # Examples
@@ -1253,7 +1253,7 @@ impl<'b, T: ?Sized> RefMut<'b, T> {
         }
     }
 
-    /// Split a `RefMut` into multiple `RefMut`s for different components of the
+    /// Splits a `RefMut` into multiple `RefMut`s for different components of the
     /// borrowed data.
     ///
     /// The underlying `RefCell` will remain mutably borrowed until both
@@ -1416,7 +1416,7 @@ impl<T: ?Sized + fmt::Display> fmt::Display for RefMut<'_, T> {
 /// co-exist with it. A `&mut T` must always be unique.
 ///
 /// Note that while mutating or mutably aliasing the contents of an `&UnsafeCell<T>` is
-/// okay (provided you enforce the invariants some other way), it is still undefined behavior
+/// ok (provided you enforce the invariants some other way), it is still undefined behavior
 /// to have multiple `&mut UnsafeCell<T>` aliases.
 ///
 /// # Examples
diff --git a/src/libcore/char/decode.rs b/src/libcore/char/decode.rs
index 510c46cdca0..133c9169df8 100644
--- a/src/libcore/char/decode.rs
+++ b/src/libcore/char/decode.rs
@@ -20,7 +20,7 @@ pub struct DecodeUtf16Error {
     code: u16,
 }
 
-/// Create an iterator over the UTF-16 encoded code points in `iter`,
+/// Creates an iterator over the UTF-16 encoded code points in `iter`,
 /// returning unpaired surrogates as `Err`s.
 ///
 /// # Examples
diff --git a/src/libcore/char/methods.rs b/src/libcore/char/methods.rs
index fbc9a4a6b8e..122e5f3affd 100644
--- a/src/libcore/char/methods.rs
+++ b/src/libcore/char/methods.rs
@@ -189,10 +189,8 @@ impl char {
     /// An extended version of `escape_debug` that optionally permits escaping
     /// Extended Grapheme codepoints. This allows us to format characters like
     /// nonspacing marks better when they're at the start of a string.
-    #[doc(hidden)]
-    #[unstable(feature = "str_internals", issue = "0")]
     #[inline]
-    pub fn escape_debug_ext(self, escape_grapheme_extended: bool) -> EscapeDebug {
+    pub(crate) fn escape_debug_ext(self, escape_grapheme_extended: bool) -> EscapeDebug {
         let init_state = match self {
             '\t' => EscapeDefaultState::Backslash('t'),
             '\r' => EscapeDefaultState::Backslash('r'),
@@ -524,7 +522,7 @@ impl char {
         }
     }
 
-    /// Returns true if this `char` is an alphabetic code point, and false if not.
+    /// Returns `true` if this `char` is an alphabetic code point, and false if not.
     ///
     /// # Examples
     ///
@@ -548,7 +546,7 @@ impl char {
         }
     }
 
-    /// Returns true if this `char` satisfies the 'XID_Start' Unicode property, and false
+    /// Returns `true` if this `char` satisfies the 'XID_Start' Unicode property, and false
     /// otherwise.
     ///
     /// 'XID_Start' is a Unicode Derived Property specified in
@@ -562,7 +560,7 @@ impl char {
         derived_property::XID_Start(self)
     }
 
-    /// Returns true if this `char` satisfies the 'XID_Continue' Unicode property, and false
+    /// Returns `true` if this `char` satisfies the 'XID_Continue' Unicode property, and false
     /// otherwise.
     ///
     /// 'XID_Continue' is a Unicode Derived Property specified in
@@ -576,7 +574,7 @@ impl char {
         derived_property::XID_Continue(self)
     }
 
-    /// Returns true if this `char` is lowercase, and false otherwise.
+    /// Returns `true` if this `char` is lowercase.
     ///
     /// 'Lowercase' is defined according to the terms of the Unicode Derived Core
     /// Property `Lowercase`.
@@ -604,7 +602,7 @@ impl char {
         }
     }
 
-    /// Returns true if this `char` is uppercase, and false otherwise.
+    /// Returns `true` if this `char` is uppercase.
     ///
     /// 'Uppercase' is defined according to the terms of the Unicode Derived Core
     /// Property `Uppercase`.
@@ -632,7 +630,7 @@ impl char {
         }
     }
 
-    /// Returns true if this `char` is whitespace, and false otherwise.
+    /// Returns `true` if this `char` is whitespace.
     ///
     /// 'Whitespace' is defined according to the terms of the Unicode Derived Core
     /// Property `White_Space`.
@@ -659,7 +657,7 @@ impl char {
         }
     }
 
-    /// Returns true if this `char` is alphanumeric, and false otherwise.
+    /// Returns `true` if this `char` is alphanumeric.
     ///
     /// 'Alphanumeric'-ness is defined in terms of the Unicode General Categories
     /// 'Nd', 'Nl', 'No' and the Derived Core Property 'Alphabetic'.
@@ -684,7 +682,7 @@ impl char {
         self.is_alphabetic() || self.is_numeric()
     }
 
-    /// Returns true if this `char` is a control code point, and false otherwise.
+    /// Returns `true` if this `char` is a control code point.
     ///
     /// 'Control code point' is defined in terms of the Unicode General
     /// Category `Cc`.
@@ -704,7 +702,7 @@ impl char {
         general_category::Cc(self)
     }
 
-    /// Returns true if this `char` is an extended grapheme character, and false otherwise.
+    /// Returns `true` if this `char` is an extended grapheme character.
     ///
     /// 'Extended grapheme character' is defined in terms of the Unicode Shaping and Rendering
     /// Category `Grapheme_Extend`.
@@ -713,7 +711,7 @@ impl char {
         derived_property::Grapheme_Extend(self)
     }
 
-    /// Returns true if this `char` is numeric, and false otherwise.
+    /// Returns `true` if this `char` is numeric.
     ///
     /// 'Numeric'-ness is defined in terms of the Unicode General Categories
     /// 'Nd', 'Nl', 'No'.
diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs
index d43a5c1032c..81fcdeee12d 100644
--- a/src/libcore/cmp.rs
+++ b/src/libcore/cmp.rs
@@ -26,7 +26,7 @@ use self::Ordering::*;
 /// relations](http://en.wikipedia.org/wiki/Partial_equivalence_relation).
 ///
 /// This trait allows for partial equality, for types that do not have a full
-/// equivalence relation.  For example, in floating point numbers `NaN != NaN`,
+/// equivalence relation. For example, in floating point numbers `NaN != NaN`,
 /// so floating point types implement `PartialEq` but not `Eq`.
 ///
 /// Formally, the equality must be (for all `a`, `b` and `c`):
diff --git a/src/libcore/convert.rs b/src/libcore/convert.rs
index 203be541e49..4a7c6e15a4d 100644
--- a/src/libcore/convert.rs
+++ b/src/libcore/convert.rs
@@ -17,7 +17,10 @@
 //! [`TryFrom<T>`][`TryFrom`] rather than [`Into<U>`][`Into`] or [`TryInto<U>`][`TryInto`],
 //! as [`From`] and [`TryFrom`] provide greater flexibility and offer
 //! equivalent [`Into`] or [`TryInto`] implementations for free, thanks to a
-//! blanket implementation in the standard library.
+//! blanket implementation in the standard library.  However, there are some cases
+//! where this is not possible, such as creating conversions into a type defined
+//! outside your library, so implementing [`Into`] instead of [`From`] is
+//! sometimes necessary.
 //!
 //! # Generic Implementations
 //!
@@ -217,7 +220,7 @@ pub trait AsMut<T: ?Sized> {
 ///
 /// There is one exception to implementing `Into`, and it's kind of esoteric.
 /// If the destination type is not part of the current crate, and it uses a
-/// generic variable, then you can't implement `From` directly.  For example,
+/// generic variable, then you can't implement `From` directly. For example,
 /// take this crate:
 ///
 /// ```compile_fail
diff --git a/src/libcore/default.rs b/src/libcore/default.rs
index 0e47c2fd0b5..5ad05b38247 100644
--- a/src/libcore/default.rs
+++ b/src/libcore/default.rs
@@ -54,7 +54,7 @@
 ///
 /// ## How can I implement `Default`?
 ///
-/// Provide an implementation for the `default()` method that returns the value of
+/// Provides an implementation for the `default()` method that returns the value of
 /// your type that should be the default:
 ///
 /// ```
diff --git a/src/libcore/ffi.rs b/src/libcore/ffi.rs
index 644380c69f2..d88793f2801 100644
--- a/src/libcore/ffi.rs
+++ b/src/libcore/ffi.rs
@@ -184,7 +184,7 @@ impl<'a> VaList<'a> {
         va_arg(self)
     }
 
-    /// Copy the `va_list` at the current location.
+    /// Copies the `va_list` at the current location.
     #[unstable(feature = "c_variadic",
                reason = "the `c_variadic` feature has not been properly tested on \
                          all supported platforms",
@@ -213,7 +213,7 @@ extern "rust-intrinsic" {
     /// `va_copy`.
     fn va_end(ap: &mut VaList);
 
-    /// Copy the current location of arglist `src` to the arglist `dst`.
+    /// Copies the current location of arglist `src` to the arglist `dst`.
     #[cfg(any(all(not(target_arch = "aarch64"), not(target_arch = "powerpc"),
                   not(target_arch = "x86_64")),
               windows))]
diff --git a/src/libcore/fmt/mod.rs b/src/libcore/fmt/mod.rs
index 530b2f52c0d..2ce58c803b8 100644
--- a/src/libcore/fmt/mod.rs
+++ b/src/libcore/fmt/mod.rs
@@ -483,12 +483,12 @@ impl Display for Arguments<'_> {
 /// implementations, such as [`debug_struct`][debug_struct].
 ///
 /// `Debug` implementations using either `derive` or the debug builder API
-/// on [`Formatter`] support pretty printing using the alternate flag: `{:#?}`.
+/// on [`Formatter`] support pretty-printing using the alternate flag: `{:#?}`.
 ///
 /// [debug_struct]: ../../std/fmt/struct.Formatter.html#method.debug_struct
 /// [`Formatter`]: ../../std/fmt/struct.Formatter.html
 ///
-/// Pretty printing with `#?`:
+/// Pretty-printing with `#?`:
 ///
 /// ```
 /// #[derive(Debug)]
diff --git a/src/libcore/future/future.rs b/src/libcore/future/future.rs
index 459e8a927e7..02457e00054 100644
--- a/src/libcore/future/future.rs
+++ b/src/libcore/future/future.rs
@@ -61,7 +61,7 @@ pub trait Future {
     /// progress, meaning that each time the current task is woken up, it should
     /// actively re-`poll` pending futures that it still has an interest in.
     ///
-    /// The `poll` function is not called repeatedly in a tight loop-- instead,
+    /// The `poll` function is not called repeatedly in a tight loop -- instead,
     /// it should only be called when the future indicates that it is ready to
     /// make progress (by calling `wake()`). If you're familiar with the
     /// `poll(2)` or `select(2)` syscalls on Unix it's worth noting that futures
diff --git a/src/libcore/hash/sip.rs b/src/libcore/hash/sip.rs
index 18f09f4c5dd..235c79307ab 100644
--- a/src/libcore/hash/sip.rs
+++ b/src/libcore/hash/sip.rs
@@ -10,7 +10,7 @@ use mem;
 /// An implementation of SipHash 1-3.
 ///
 /// This is currently the default hashing function used by standard library
-/// (eg. `collections::HashMap` uses it by default).
+/// (e.g., `collections::HashMap` uses it by default).
 ///
 /// See: <https://131002.net/siphash>
 #[unstable(feature = "hashmap_internals", issue = "0")]
@@ -90,7 +90,7 @@ macro_rules! compress {
     });
 }
 
-/// Load an integer of the desired type from a byte stream, in LE order. Uses
+/// Loads an integer of the desired type from a byte stream, in LE order. Uses
 /// `copy_nonoverlapping` to let the compiler generate the most efficient way
 /// to load it from a possibly unaligned address.
 ///
@@ -107,7 +107,7 @@ macro_rules! load_int_le {
     });
 }
 
-/// Load an u64 using up to 7 bytes of a byte slice.
+/// Loads an u64 using up to 7 bytes of a byte slice.
 ///
 /// Unsafe because: unchecked indexing at start..start+len
 #[inline]
diff --git a/src/libcore/hint.rs b/src/libcore/hint.rs
index ad5a2071a73..89de5c1bc8a 100644
--- a/src/libcore/hint.rs
+++ b/src/libcore/hint.rs
@@ -34,7 +34,7 @@ use intrinsics;
 ///     use std::hint::unreachable_unchecked;
 ///
 ///     // `b.saturating_add(1)` is always positive (not zero),
-///     // hence `checked_div` will never return None.
+///     // hence `checked_div` will never return `None`.
 ///     // Therefore, the else branch is unreachable.
 ///     a.checked_div(b.saturating_add(1))
 ///         .unwrap_or_else(|| unsafe { unreachable_unchecked() })
diff --git a/src/libcore/internal_macros.rs b/src/libcore/internal_macros.rs
index d12800f7124..9f0f6fd49fb 100644
--- a/src/libcore/internal_macros.rs
+++ b/src/libcore/internal_macros.rs
@@ -75,3 +75,47 @@ macro_rules! forward_ref_op_assign {
         }
     }
 }
+
+/// Create a zero-size type similar to a closure type, but named.
+#[unstable(feature = "std_internals", issue = "0")]
+macro_rules! impl_fn_for_zst {
+    ($(
+        $( #[$attr: meta] )*
+        // FIXME: when libcore is in the 2018 edition, use `?` repetition in
+        // $( <$( $li : lifetime ),+> )?
+        struct $Name: ident impl$( <$( $lifetime : lifetime ),+> )* Fn =
+            |$( $arg: ident: $ArgTy: ty ),*| -> $ReturnTy: ty
+            $body: block;
+    )+) => {
+        $(
+            $( #[$attr] )*
+            struct $Name;
+
+            impl $( <$( $lifetime ),+> )* Fn<($( $ArgTy, )*)> for $Name {
+                #[inline]
+                extern "rust-call" fn call(&self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
+                    $body
+                }
+            }
+
+            impl $( <$( $lifetime ),+> )* FnMut<($( $ArgTy, )*)> for $Name {
+                #[inline]
+                extern "rust-call" fn call_mut(
+                    &mut self,
+                    ($( $arg, )*): ($( $ArgTy, )*)
+                ) -> $ReturnTy {
+                    Fn::call(&*self, ($( $arg, )*))
+                }
+            }
+
+            impl $( <$( $lifetime ),+> )* FnOnce<($( $ArgTy, )*)> for $Name {
+                type Output = $ReturnTy;
+
+                #[inline]
+                extern "rust-call" fn call_once(self, ($( $arg, )*): ($( $ArgTy, )*)) -> $ReturnTy {
+                    Fn::call(&self, ($( $arg, )*))
+                }
+            }
+        )+
+    }
+}
diff --git a/src/libcore/intrinsics.rs b/src/libcore/intrinsics.rs
index e927ed40d7f..f6de7566be9 100644
--- a/src/libcore/intrinsics.rs
+++ b/src/libcore/intrinsics.rs
@@ -1,6 +1,6 @@
-//! rustc compiler intrinsics.
+//! Compiler intrinsics.
 //!
-//! The corresponding definitions are in librustc_codegen_llvm/intrinsic.rs.
+//! The corresponding definitions are in `librustc_codegen_llvm/intrinsic.rs`.
 //!
 //! # Volatiles
 //!
@@ -315,35 +315,35 @@ extern "rust-intrinsic" {
     /// [`AtomicBool::swap`](../../std/sync/atomic/struct.AtomicBool.html#method.swap).
     pub fn atomic_xchg_relaxed<T>(dst: *mut T, src: T) -> T;
 
-    /// Add to the current value, returning the previous value.
+    /// Adds to the current value, returning the previous value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `fetch_add` method by passing
     /// [`Ordering::SeqCst`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `order`. For example,
     /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
     pub fn atomic_xadd<T>(dst: *mut T, src: T) -> T;
-    /// Add to the current value, returning the previous value.
+    /// Adds to the current value, returning the previous value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `fetch_add` method by passing
     /// [`Ordering::Acquire`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `order`. For example,
     /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
     pub fn atomic_xadd_acq<T>(dst: *mut T, src: T) -> T;
-    /// Add to the current value, returning the previous value.
+    /// Adds to the current value, returning the previous value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `fetch_add` method by passing
     /// [`Ordering::Release`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `order`. For example,
     /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
     pub fn atomic_xadd_rel<T>(dst: *mut T, src: T) -> T;
-    /// Add to the current value, returning the previous value.
+    /// Adds to the current value, returning the previous value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `fetch_add` method by passing
     /// [`Ordering::AcqRel`](../../std/sync/atomic/enum.Ordering.html)
     /// as the `order`. For example,
     /// [`AtomicIsize::fetch_add`](../../std/sync/atomic/struct.AtomicIsize.html#method.fetch_add).
     pub fn atomic_xadd_acqrel<T>(dst: *mut T, src: T) -> T;
-    /// Add to the current value, returning the previous value.
+    /// Adds to the current value, returning the previous value.
     /// The stabilized version of this intrinsic is available on the
     /// `std::sync::atomic` types via the `fetch_add` method by passing
     /// [`Ordering::Relaxed`](../../std/sync/atomic/enum.Ordering.html)
@@ -556,7 +556,7 @@ extern "rust-intrinsic" {
     pub fn atomic_umax_relaxed<T>(dst: *mut T, src: T) -> T;
 
     /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
-    /// if supported; otherwise, it is a noop.
+    /// if supported; otherwise, it is a no-op.
     /// Prefetches have no effect on the behavior of the program but can change its performance
     /// characteristics.
     ///
@@ -564,7 +564,7 @@ extern "rust-intrinsic" {
     /// ranging from (0) - no locality, to (3) - extremely local keep in cache
     pub fn prefetch_read_data<T>(data: *const T, locality: i32);
     /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
-    /// if supported; otherwise, it is a noop.
+    /// if supported; otherwise, it is a no-op.
     /// Prefetches have no effect on the behavior of the program but can change its performance
     /// characteristics.
     ///
@@ -572,7 +572,7 @@ extern "rust-intrinsic" {
     /// ranging from (0) - no locality, to (3) - extremely local keep in cache
     pub fn prefetch_write_data<T>(data: *const T, locality: i32);
     /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
-    /// if supported; otherwise, it is a noop.
+    /// if supported; otherwise, it is a no-op.
     /// Prefetches have no effect on the behavior of the program but can change its performance
     /// characteristics.
     ///
@@ -580,7 +580,7 @@ extern "rust-intrinsic" {
     /// ranging from (0) - no locality, to (3) - extremely local keep in cache
     pub fn prefetch_read_instruction<T>(data: *const T, locality: i32);
     /// The `prefetch` intrinsic is a hint to the code generator to insert a prefetch instruction
-    /// if supported; otherwise, it is a noop.
+    /// if supported; otherwise, it is a no-op.
     /// Prefetches have no effect on the behavior of the program but can change its performance
     /// characteristics.
     ///
@@ -697,7 +697,7 @@ extern "rust-intrinsic" {
     /// Creates a value initialized to zero.
     ///
     /// `init` is unsafe because it returns a zeroed-out datum,
-    /// which is unsafe unless T is `Copy`.  Also, even if T is
+    /// which is unsafe unless `T` is `Copy`. Also, even if T is
     /// `Copy`, an all-zero value may not correspond to any legitimate
     /// state for the type in question.
     pub fn init<T>() -> T;
@@ -857,7 +857,7 @@ extern "rust-intrinsic" {
     ///
     /// // The no-copy, unsafe way, still using transmute, but not UB.
     /// // This is equivalent to the original, but safer, and reuses the
-    /// // same Vec internals. Therefore the new inner type must have the
+    /// // same `Vec` internals. Therefore, the new inner type must have the
     /// // exact same size, and the same alignment, as the old type.
     /// // The same caveats exist for this method as transmute, for
     /// // the original inner type (`&i32`) to the converted inner type
@@ -875,8 +875,8 @@ extern "rust-intrinsic" {
     /// ```
     /// use std::{slice, mem};
     ///
-    /// // There are multiple ways to do this; and there are multiple problems
-    /// // with the following, transmute, way.
+    /// // There are multiple ways to do this, and there are multiple problems
+    /// // with the following (transmute) way.
     /// fn split_at_mut_transmute<T>(slice: &mut [T], mid: usize)
     ///                              -> (&mut [T], &mut [T]) {
     ///     let len = slice.len();
@@ -988,7 +988,7 @@ extern "rust-intrinsic" {
     ///   beginning at `dst` with the same size.
     ///
     /// Like [`read`], `copy_nonoverlapping` creates a bitwise copy of `T`, regardless of
-    /// whether `T` is [`Copy`].  If `T` is not [`Copy`], using *both* the values
+    /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using *both* the values
     /// in the region beginning at `*src` and the region beginning at `*dst` can
     /// [violate memory safety][read-ownership].
     ///
@@ -1055,7 +1055,7 @@ extern "rust-intrinsic" {
     /// [`copy_nonoverlapping`] can be used instead.
     ///
     /// `copy` is semantically equivalent to C's [`memmove`], but with the argument
-    /// order swapped.  Copying takes place as if the bytes were copied from `src`
+    /// order swapped. Copying takes place as if the bytes were copied from `src`
     /// to a temporary array and then copied from the array to `dst`.
     ///
     /// [`copy_nonoverlapping`]: ./fn.copy_nonoverlapping.html
@@ -1072,7 +1072,7 @@ extern "rust-intrinsic" {
     /// * Both `src` and `dst` must be properly aligned.
     ///
     /// Like [`read`], `copy` creates a bitwise copy of `T`, regardless of
-    /// whether `T` is [`Copy`].  If `T` is not [`Copy`], using both the values
+    /// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the values
     /// in the region beginning at `*src` and the region beginning at `*dst` can
     /// [violate memory safety][read-ownership].
     ///
@@ -1200,19 +1200,19 @@ extern "rust-intrinsic" {
     /// unless size is equal to zero.
     pub fn volatile_set_memory<T>(dst: *mut T, val: u8, count: usize);
 
-    /// Perform a volatile load from the `src` pointer.
+    /// Performs a volatile load from the `src` pointer.
     /// The stabilized version of this intrinsic is
     /// [`std::ptr::read_volatile`](../../std/ptr/fn.read_volatile.html).
     pub fn volatile_load<T>(src: *const T) -> T;
-    /// Perform a volatile store to the `dst` pointer.
+    /// Performs a volatile store to the `dst` pointer.
     /// The stabilized version of this intrinsic is
     /// [`std::ptr::write_volatile`](../../std/ptr/fn.write_volatile.html).
     pub fn volatile_store<T>(dst: *mut T, val: T);
 
-    /// Perform a volatile load from the `src` pointer
+    /// Performs a volatile load from the `src` pointer
     /// The pointer is not required to be aligned.
     pub fn unaligned_volatile_load<T>(src: *const T) -> T;
-    /// Perform a volatile store to the `dst` pointer.
+    /// Performs a volatile store to the `dst` pointer.
     /// The pointer is not required to be aligned.
     pub fn unaligned_volatile_store<T>(dst: *mut T, val: T);
 
diff --git a/src/libcore/iter/range.rs b/src/libcore/iter/range.rs
index 66c09a0ddd0..a3e9cfa9493 100644
--- a/src/libcore/iter/range.rs
+++ b/src/libcore/iter/range.rs
@@ -20,19 +20,19 @@ pub trait Step: Clone + PartialOrd + Sized {
     /// without overflow.
     fn steps_between(start: &Self, end: &Self) -> Option<usize>;
 
-    /// Replaces this step with `1`, returning itself
+    /// Replaces this step with `1`, returning itself.
     fn replace_one(&mut self) -> Self;
 
-    /// Replaces this step with `0`, returning itself
+    /// Replaces this step with `0`, returning itself.
     fn replace_zero(&mut self) -> Self;
 
-    /// Adds one to this step, returning the result
+    /// Adds one to this step, returning the result.
     fn add_one(&self) -> Self;
 
-    /// Subtracts one to this step, returning the result
+    /// Subtracts one to this step, returning the result.
     fn sub_one(&self) -> Self;
 
-    /// Add an usize, returning None on overflow
+    /// Adds a `usize`, returning `None` on overflow.
     fn add_usize(&self, n: usize) -> Option<Self>;
 }
 
diff --git a/src/libcore/iter/sources.rs b/src/libcore/iter/sources.rs
index 2b741e66170..6f45f082d6a 100644
--- a/src/libcore/iter/sources.rs
+++ b/src/libcore/iter/sources.rs
@@ -504,10 +504,8 @@ pub fn once_with<A, F: FnOnce() -> A>(gen: F) -> OnceWith<F> {
 /// [`FusedIterator`]: trait.FusedIterator.html
 /// [`Iterator::size_hint`]: trait.Iterator.html#method.size_hint
 ///
-/// The closure can use its its captures and environment
-/// to track state across iterations.
-/// Depending on how the iterator is used,
-/// this may require specifying the `move` keyword on the closure.
+/// The closure can use captures and its environment to track state across iterations. Depending on
+/// how the iterator is used, this may require specifying the `move` keyword on the closure.
 ///
 /// # Examples
 ///
diff --git a/src/libcore/iter/traits/exact_size.rs b/src/libcore/iter/traits/exact_size.rs
index 3bfba29e219..d6eab40213e 100644
--- a/src/libcore/iter/traits/exact_size.rs
+++ b/src/libcore/iter/traits/exact_size.rs
@@ -104,7 +104,7 @@ pub trait ExactSizeIterator: Iterator {
         lower
     }
 
-    /// Returns whether the iterator is empty.
+    /// Returns `true` if the iterator is empty.
     ///
     /// This method has a default implementation using `self.len()`, so you
     /// don't need to implement it yourself.
diff --git a/src/libcore/iter/traits/iterator.rs b/src/libcore/iter/traits/iterator.rs
index 9dfa83f473b..861e9c3157a 100644
--- a/src/libcore/iter/traits/iterator.rs
+++ b/src/libcore/iter/traits/iterator.rs
@@ -120,7 +120,7 @@ pub trait Iterator {
     /// // ... and then None once it's over.
     /// assert_eq!(None, iter.next());
     ///
-    /// // More calls may or may not return None. Here, they always will.
+    /// // More calls may or may not return `None`. Here, they always will.
     /// assert_eq!(None, iter.next());
     /// assert_eq!(None, iter.next());
     /// ```
@@ -564,9 +564,9 @@ pub trait Iterator {
     /// Calls a closure on each element of an iterator.
     ///
     /// This is equivalent to using a [`for`] loop on the iterator, although
-    /// `break` and `continue` are not possible from a closure.  It's generally
+    /// `break` and `continue` are not possible from a closure. It's generally
     /// more idiomatic to use a `for` loop, but `for_each` may be more legible
-    /// when processing items at the end of longer iterator chains.  In some
+    /// when processing items at the end of longer iterator chains. In some
     /// cases `for_each` may also be faster than a loop, because it will use
     /// internal iteration on adaptors like `Chain`.
     ///
@@ -952,8 +952,7 @@ pub trait Iterator {
     /// ```
     ///
     /// The `3` is no longer there, because it was consumed in order to see if
-    /// the iteration should stop, but wasn't placed back into the iterator or
-    /// some similar thing.
+    /// the iteration should stop, but wasn't placed back into the iterator.
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn take_while<P>(self, predicate: P) -> TakeWhile<Self, P> where
@@ -1216,7 +1215,7 @@ pub trait Iterator {
     /// assert_eq!(iter.next(), Some(4));
     /// assert_eq!(iter.next(), None);
     ///
-    /// // it will always return None after the first time.
+    /// // it will always return `None` after the first time.
     /// assert_eq!(iter.next(), None);
     /// assert_eq!(iter.next(), None);
     /// assert_eq!(iter.next(), None);
@@ -1516,7 +1515,7 @@ pub trait Iterator {
     /// is propagated back to the caller immediately (short-circuiting).
     ///
     /// The initial value is the value the accumulator will have on the first
-    /// call.  If applying the closure succeeded against every element of the
+    /// call. If applying the closure succeeded against every element of the
     /// iterator, `try_fold()` returns the final accumulator as success.
     ///
     /// Folding is useful whenever you have a collection of something, and want
@@ -1529,10 +1528,10 @@ pub trait Iterator {
     /// do something better than the default `for` loop implementation.
     ///
     /// In particular, try to have this call `try_fold()` on the internal parts
-    /// from which this iterator is composed.  If multiple calls are needed,
+    /// from which this iterator is composed. If multiple calls are needed,
     /// the `?` operator may be convenient for chaining the accumulator value
     /// along, but beware any invariants that need to be upheld before those
-    /// early returns.  This is a `&mut self` method, so iteration needs to be
+    /// early returns. This is a `&mut self` method, so iteration needs to be
     /// resumable after hitting an error here.
     ///
     /// # Examples
diff --git a/src/libcore/lib.rs b/src/libcore/lib.rs
index 7180a813a3e..419980225c3 100644
--- a/src/libcore/lib.rs
+++ b/src/libcore/lib.rs
@@ -24,7 +24,7 @@
 //!   often generated by LLVM. Additionally, this library can make explicit
 //!   calls to these functions. Their signatures are the same as found in C.
 //!   These functions are often provided by the system libc, but can also be
-//!   provided by the [rlibc crate](https://crates.io/crates/rlibc).
+//!   provided by the [compiler-builtins crate](https://crates.io/crates/compiler_builtins).
 //!
 //! * `rust_begin_panic` - This function takes four arguments, a
 //!   `fmt::Arguments`, a `&'static str`, and two `u32`'s. These four arguments
@@ -51,9 +51,7 @@
 #![cfg(not(test))]
 
 #![stable(feature = "core", since = "1.6.0")]
-#![doc(html_logo_url = "https://www.rust-lang.org/logos/rust-logo-128x128-blk-v2.png",
-       html_favicon_url = "https://doc.rust-lang.org/favicon.ico",
-       html_root_url = "https://doc.rust-lang.org/nightly/",
+#![doc(html_root_url = "https://doc.rust-lang.org/nightly/",
        html_playground_url = "https://play.rust-lang.org/",
        issue_tracker_base_url = "https://github.com/rust-lang/rust/issues/",
        test(no_crate_inject, attr(deny(warnings))),
@@ -97,6 +95,7 @@
 #![feature(simd_ffi)]
 #![feature(specialization)]
 #![feature(staged_api)]
+#![feature(std_internals)]
 #![feature(stmt_expr_attributes)]
 #![feature(unboxed_closures)]
 #![feature(unsized_locals)]
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs
index 12b7adb8a9d..2eb506cedd4 100644
--- a/src/libcore/macros.rs
+++ b/src/libcore/macros.rs
@@ -1,6 +1,7 @@
-/// Entry point of thread panic, for details, see std::macros
+/// Entry point of thread panic. For details, see `std::macros`.
 #[macro_export]
-#[allow_internal_unstable]
+#[cfg_attr(not(stage0), allow_internal_unstable(core_panic, __rust_unstable_column))]
+#[cfg_attr(stage0, allow_internal_unstable)]
 #[stable(feature = "core", since = "1.6.0")]
 macro_rules! panic {
     () => (
@@ -409,7 +410,8 @@ macro_rules! write {
 /// ```
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
-#[allow_internal_unstable]
+#[cfg_attr(stage0, allow_internal_unstable)]
+#[cfg_attr(not(stage0), allow_internal_unstable(format_args_nl))]
 macro_rules! writeln {
     ($dst:expr) => (
         write!($dst, "\n")
@@ -432,7 +434,7 @@ macro_rules! writeln {
 /// * Iterators that dynamically terminate.
 ///
 /// If the determination that the code is unreachable proves incorrect, the
-/// program immediately terminates with a [`panic!`].  The function [`unreachable_unchecked`],
+/// program immediately terminates with a [`panic!`]. The function [`unreachable_unchecked`],
 /// which belongs to the [`std::hint`] module, informs the compiler to
 /// optimize the code out of the release version entirely.
 ///
@@ -493,7 +495,7 @@ macro_rules! unreachable {
 /// A standardized placeholder for marking unfinished code.
 ///
 /// This can be useful if you are prototyping and are just looking to have your
-/// code typecheck, or if you're implementing a trait that requires multiple
+/// code type-check, or if you're implementing a trait that requires multiple
 /// methods, and you're only planning on using one of them.
 ///
 /// # Panics
@@ -555,12 +557,12 @@ macro_rules! unimplemented {
 #[macro_export]
 #[unstable(feature = "maybe_uninit", issue = "53491")]
 macro_rules! uninitialized_array {
-    // This `into_inner` is safe because an array of `MaybeUninit` does not
+    // This `into_initialized` is safe because an array of `MaybeUninit` does not
     // require initialization.
     // FIXME(#49147): Could be replaced by an array initializer, once those can
     // be any const expression.
     ($t:ty; $size:expr) => (unsafe {
-        MaybeUninit::<[MaybeUninit<$t>; $size]>::uninitialized().into_inner()
+        MaybeUninit::<[MaybeUninit<$t>; $size]>::uninitialized().into_initialized()
     });
 }
 
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 8b6d9d882b5..2a493e88fe8 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -15,6 +15,7 @@ use ptr;
 use ops::{Deref, DerefMut};
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[doc(inline)]
 pub use intrinsics::transmute;
 
 /// Takes ownership and "forgets" about the value **without running its destructor**.
@@ -294,7 +295,7 @@ pub const fn size_of<T>() -> usize {
 /// Returns the size of the pointed-to value in bytes.
 ///
 /// This is usually the same as `size_of::<T>()`. However, when `T` *has* no
-/// statically known size, e.g., a slice [`[T]`][slice] or a [trait object],
+/// statically-known size, e.g., a slice [`[T]`][slice] or a [trait object],
 /// then `size_of_val` can be used to get the dynamically-known size.
 ///
 /// [slice]: ../../std/primitive.slice.html
@@ -402,7 +403,7 @@ pub fn align_of_val<T: ?Sized>(val: &T) -> usize {
     unsafe { intrinsics::min_align_of_val(val) }
 }
 
-/// Returns whether dropping values of type `T` matters.
+/// Returns `true` if dropping values of type `T` matters.
 ///
 /// This is purely an optimization hint, and may be implemented conservatively:
 /// it may return `true` for types that don't actually need to be dropped.
@@ -957,7 +958,7 @@ impl<T> ManuallyDrop<T> {
         ManuallyDrop { value }
     }
 
-    /// Extract the value from the `ManuallyDrop` container.
+    /// Extracts the value from the `ManuallyDrop` container.
     ///
     /// This allows the value to be dropped again.
     ///
@@ -1034,7 +1035,46 @@ impl<T: ?Sized> DerefMut for ManuallyDrop<T> {
     }
 }
 
-/// A newtype to construct uninitialized instances of `T`
+/// A newtype to construct uninitialized instances of `T`.
+///
+/// The compiler, in general, assumes that variables are properly initialized
+/// at their respective type. For example, a variable of reference type must
+/// be aligned and non-NULL. This is an invariant that must *always* be upheld,
+/// even in unsafe code. As a consequence, zero-initializing a variable of reference
+/// type causes instantaneous undefined behavior, no matter whether that reference
+/// ever gets used to access memory:
+///
+/// ```rust,no_run
+/// use std::mem;
+///
+/// let x: &i32 = unsafe { mem::zeroed() }; // undefined behavior!
+/// ```
+///
+/// This is exploited by the compiler for various optimizations, such as eliding
+/// run-time checks and optimizing `enum` layout.
+///
+/// Not initializing memory at all (instead of zero--initializing it) causes the same
+/// issue: after all, the initial value of the variable might just happen to be
+/// one that violates the invariant.
+///
+/// `MaybeUninit` serves to enable unsafe code to deal with uninitialized data:
+/// it is a signal to the compiler indicating that the data here might *not*
+/// be initialized:
+///
+/// ```rust
+/// #![feature(maybe_uninit)]
+/// use std::mem::MaybeUninit;
+///
+/// // Create an explicitly uninitialized reference.
+/// let mut x = MaybeUninit::<&i32>::uninitialized();
+/// // Set it to a valid value.
+/// x.set(&0);
+/// // Extract the initialized data -- this is only allowed *after* properly
+/// // initializing `x`!
+/// let x = unsafe { x.into_initialized() };
+/// ```
+///
+/// The compiler then knows to not optimize this code.
 #[allow(missing_debug_implementations)]
 #[unstable(feature = "maybe_uninit", issue = "53491")]
 // NOTE after stabilizing `MaybeUninit` proceed to deprecate `mem::{uninitialized,zeroed}`
@@ -1054,7 +1094,7 @@ impl<T> MaybeUninit<T> {
         MaybeUninit { value: ManuallyDrop::new(val) }
     }
 
-    /// Create a new `MaybeUninit` in an uninitialized state.
+    /// Creates a new `MaybeUninit` in an uninitialized state.
     ///
     /// Note that dropping a `MaybeUninit` will never call `T`'s drop code.
     /// It is your responsibility to make sure `T` gets dropped if it got initialized.
@@ -1064,8 +1104,8 @@ impl<T> MaybeUninit<T> {
         MaybeUninit { uninit: () }
     }
 
-    /// Create a new `MaybeUninit` in an uninitialized state, with the memory being
-    /// filled with `0` bytes.  It depends on `T` whether that already makes for
+    /// Creates a new `MaybeUninit` in an uninitialized state, with the memory being
+    /// filled with `0` bytes. It depends on `T` whether that already makes for
     /// proper initialization. For example, `MaybeUninit<usize>::zeroed()` is initialized,
     /// but `MaybeUninit<&'static i32>::zeroed()` is not because references must not
     /// be null.
@@ -1082,16 +1122,19 @@ impl<T> MaybeUninit<T> {
         u
     }
 
-    /// Set the value of the `MaybeUninit`. This overwrites any previous value without dropping it.
+    /// Sets the value of the `MaybeUninit`. This overwrites any previous value without dropping it.
+    /// For your convenience, this also returns a mutable reference to the (now safely initialized)
+    /// contents of `self`.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
-    pub fn set(&mut self, val: T) {
+    pub fn set(&mut self, val: T) -> &mut T {
         unsafe {
             self.value = ManuallyDrop::new(val);
+            self.get_mut()
         }
     }
 
-    /// Extract the value from the `MaybeUninit` container.  This is a great way
+    /// Extracts the value from the `MaybeUninit` container. This is a great way
     /// to ensure that the data will get dropped, because the resulting `T` is
     /// subject to the usual drop handling.
     ///
@@ -1101,12 +1144,20 @@ impl<T> MaybeUninit<T> {
     /// state, otherwise this will immediately cause undefined behavior.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
-    pub unsafe fn into_inner(self) -> T {
+    pub unsafe fn into_initialized(self) -> T {
         intrinsics::panic_if_uninhabited::<T>();
         ManuallyDrop::into_inner(self.value)
     }
 
-    /// Get a reference to the contained value.
+    /// Deprecated alternative to `into_initialized`. Will never get stabilized.
+    /// Exists only to transition stdsimd to `into_initialized`.
+    #[inline(always)]
+    #[allow(unused)]
+    pub(crate) unsafe fn into_inner(self) -> T {
+        self.into_initialized()
+    }
+
+    /// Gets a reference to the contained value.
     ///
     /// # Unsafety
     ///
@@ -1118,7 +1169,7 @@ impl<T> MaybeUninit<T> {
         &*self.value
     }
 
-    /// Get a mutable reference to the contained value.
+    /// Gets a mutable reference to the contained value.
     ///
     /// # Unsafety
     ///
@@ -1133,30 +1184,30 @@ impl<T> MaybeUninit<T> {
         &mut *self.value
     }
 
-    /// Get a pointer to the contained value. Reading from this pointer will be undefined
-    /// behavior unless the `MaybeUninit` is initialized.
+    /// Gets a pointer to the contained value. Reading from this pointer or turning it
+    /// into a reference will be undefined behavior unless the `MaybeUninit` is initialized.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
     pub fn as_ptr(&self) -> *const T {
         unsafe { &*self.value as *const T }
     }
 
-    /// Get a mutable pointer to the contained value. Reading from this pointer will be undefined
-    /// behavior unless the `MaybeUninit` is initialized.
+    /// Get sa mutable pointer to the contained value. Reading from this pointer or turning it
+    /// into a reference will be undefined behavior unless the `MaybeUninit` is initialized.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
     pub fn as_mut_ptr(&mut self) -> *mut T {
         unsafe { &mut *self.value as *mut T }
     }
 
-    /// Get a pointer to the first element of the array.
+    /// Gets a pointer to the first element of the array.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
     pub fn first_ptr(this: &[MaybeUninit<T>]) -> *const T {
         this as *const [MaybeUninit<T>] as *const T
     }
 
-    /// Get a mutable pointer to the first element of the array.
+    /// Gets a mutable pointer to the first element of the array.
     #[unstable(feature = "maybe_uninit", issue = "53491")]
     #[inline(always)]
     pub fn first_ptr_mut(this: &mut [MaybeUninit<T>]) -> *mut T {
diff --git a/src/libcore/num/dec2flt/algorithm.rs b/src/libcore/num/dec2flt/algorithm.rs
index d56fa9662a9..3b57bb7544b 100644
--- a/src/libcore/num/dec2flt/algorithm.rs
+++ b/src/libcore/num/dec2flt/algorithm.rs
@@ -61,7 +61,7 @@ mod fpu_precision {
         unsafe { asm!("fldcw $0" :: "m" (cw) :: "volatile") }
     }
 
-    /// Set the precision field of the FPU to `T` and return a `FPUControlWord`
+    /// Sets the precision field of the FPU to `T` and returns a `FPUControlWord`.
     pub fn set_precision<T>() -> FPUControlWord {
         let cw = 0u16;
 
diff --git a/src/libcore/num/dec2flt/mod.rs b/src/libcore/num/dec2flt/mod.rs
index 14a912872be..47ea5aa5ff0 100644
--- a/src/libcore/num/dec2flt/mod.rs
+++ b/src/libcore/num/dec2flt/mod.rs
@@ -37,7 +37,7 @@
 //!
 //! In addition, there are numerous helper functions that are used in the paper but not available
 //! in Rust (or at least in core). Our version is additionally complicated by the need to handle
-//! overflow and underflow and the desire to handle subnormal numbers.  Bellerophon and
+//! overflow and underflow and the desire to handle subnormal numbers. Bellerophon and
 //! Algorithm R have trouble with overflow, subnormals, and underflow. We conservatively switch to
 //! Algorithm M (with the modifications described in section 8 of the paper) well before the
 //! inputs get into the critical region.
@@ -54,7 +54,7 @@
 //! operations as well, if you want 0.5 ULP accuracy you need to do *everything* in full precision
 //! and round *exactly once, at the end*, by considering all truncated bits at once.
 //!
-//! FIXME Although some code duplication is necessary, perhaps parts of the code could be shuffled
+//! FIXME: Although some code duplication is necessary, perhaps parts of the code could be shuffled
 //! around such that less code is duplicated. Large parts of the algorithms are independent of the
 //! float type to output, or only needs access to a few constants, which could be passed in as
 //! parameters.
@@ -148,7 +148,7 @@ macro_rules! from_str_float_impl {
             /// # Return value
             ///
             /// `Err(ParseFloatError)` if the string did not represent a valid
-            /// number.  Otherwise, `Ok(n)` where `n` is the floating-point
+            /// number. Otherwise, `Ok(n)` where `n` is the floating-point
             /// number represented by `src`.
             #[inline]
             fn from_str(src: &str) -> Result<Self, ParseFloatError> {
@@ -209,7 +209,7 @@ fn pfe_invalid() -> ParseFloatError {
     ParseFloatError { kind: FloatErrorKind::Invalid }
 }
 
-/// Split decimal string into sign and the rest, without inspecting or validating the rest.
+/// Splits a decimal string into sign and the rest, without inspecting or validating the rest.
 fn extract_sign(s: &str) -> (Sign, &str) {
     match s.as_bytes()[0] {
         b'+' => (Sign::Positive, &s[1..]),
@@ -219,7 +219,7 @@ fn extract_sign(s: &str) -> (Sign, &str) {
     }
 }
 
-/// Convert a decimal string into a floating point number.
+/// Converts a decimal string into a floating point number.
 fn dec2flt<T: RawFloat>(s: &str) -> Result<T, ParseFloatError> {
     if s.is_empty() {
         return Err(pfe_empty())
diff --git a/src/libcore/num/dec2flt/num.rs b/src/libcore/num/dec2flt/num.rs
index b76c58cc66e..12671318571 100644
--- a/src/libcore/num/dec2flt/num.rs
+++ b/src/libcore/num/dec2flt/num.rs
@@ -27,7 +27,7 @@ pub fn compare_with_half_ulp(f: &Big, ones_place: usize) -> Ordering {
     Equal
 }
 
-/// Convert an ASCII string containing only decimal digits to a `u64`.
+/// Converts an ASCII string containing only decimal digits to a `u64`.
 ///
 /// Does not perform checks for overflow or invalid characters, so if the caller is not careful,
 /// the result is bogus and can panic (though it won't be `unsafe`). Additionally, empty strings
@@ -44,7 +44,7 @@ pub fn from_str_unchecked<'a, T>(bytes: T) -> u64 where T : IntoIterator<Item=&'
     result
 }
 
-/// Convert a string of ASCII digits into a bignum.
+/// Converts a string of ASCII digits into a bignum.
 ///
 /// Like `from_str_unchecked`, this function relies on the parser to weed out non-digits.
 pub fn digits_to_big(integral: &[u8], fractional: &[u8]) -> Big {
@@ -69,7 +69,7 @@ pub fn to_u64(x: &Big) -> u64 {
 }
 
 
-/// Extract a range of bits.
+/// Extracts a range of bits.
 
 /// Index 0 is the least significant bit and the range is half-open as usual.
 /// Panics if asked to extract more bits than fit into the return type.
diff --git a/src/libcore/num/dec2flt/parse.rs b/src/libcore/num/dec2flt/parse.rs
index 9e075e43303..933f8c1d3f7 100644
--- a/src/libcore/num/dec2flt/parse.rs
+++ b/src/libcore/num/dec2flt/parse.rs
@@ -42,7 +42,7 @@ pub enum ParseResult<'a> {
     Invalid,
 }
 
-/// Check if the input string is a valid floating point number and if so, locate the integral
+/// Checks if the input string is a valid floating point number and if so, locate the integral
 /// part, the fractional part, and the exponent in it. Does not handle signs.
 pub fn parse_decimal(s: &str) -> ParseResult {
     if s.is_empty() {
diff --git a/src/libcore/num/dec2flt/rawfp.rs b/src/libcore/num/dec2flt/rawfp.rs
index 6976bd1a0ee..b65f539b29c 100644
--- a/src/libcore/num/dec2flt/rawfp.rs
+++ b/src/libcore/num/dec2flt/rawfp.rs
@@ -59,10 +59,10 @@ pub trait RawFloat
     /// Type used by `to_bits` and `from_bits`.
     type Bits: Add<Output = Self::Bits> + From<u8> + TryFrom<u64>;
 
-    /// Raw transmutation to integer.
+    /// Performs a raw transmutation to an integer.
     fn to_bits(self) -> Self::Bits;
 
-    /// Raw transmutation from integer.
+    /// Performs a raw transmutation from an integer.
     fn from_bits(v: Self::Bits) -> Self;
 
     /// Returns the category that this number falls into.
@@ -71,14 +71,14 @@ pub trait RawFloat
     /// Returns the mantissa, exponent and sign as integers.
     fn integer_decode(self) -> (u64, i16, i8);
 
-    /// Decode the float.
+    /// Decodes the float.
     fn unpack(self) -> Unpacked;
 
-    /// Cast from a small integer that can be represented exactly.  Panic if the integer can't be
+    /// Casts from a small integer that can be represented exactly. Panic if the integer can't be
     /// represented, the other code in this module makes sure to never let that happen.
     fn from_int(x: u64) -> Self;
 
-    /// Get the value 10<sup>e</sup> from a pre-computed table.
+    /// Gets the value 10<sup>e</sup> from a pre-computed table.
     /// Panics for `e >= CEIL_LOG5_OF_MAX_SIG`.
     fn short_fast_pow10(e: usize) -> Self;
 
@@ -240,7 +240,7 @@ impl RawFloat for f64 {
     fn from_bits(v: Self::Bits) -> Self { Self::from_bits(v) }
 }
 
-/// Convert an Fp to the closest machine float type.
+/// Converts an `Fp` to the closest machine float type.
 /// Does not handle subnormal results.
 pub fn fp_to_float<T: RawFloat>(x: Fp) -> T {
     let x = x.normalize();
@@ -319,7 +319,7 @@ pub fn big_to_fp(f: &Big) -> Fp {
     }
 }
 
-/// Find the largest floating point number strictly smaller than the argument.
+/// Finds the largest floating point number strictly smaller than the argument.
 /// Does not handle subnormals, zero, or exponent underflow.
 pub fn prev_float<T: RawFloat>(x: T) -> T {
     match x.classify() {
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 68da79135d3..dc0580764ac 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -144,7 +144,7 @@ pub mod consts {
 #[lang = "f32"]
 #[cfg(not(test))]
 impl f32 {
-    /// Returns `true` if this value is `NaN` and false otherwise.
+    /// Returns `true` if this value is `NaN`.
     ///
     /// ```
     /// use std::f32;
@@ -169,8 +169,8 @@ impl f32 {
         f32::from_bits(self.to_bits() & 0x7fff_ffff)
     }
 
-    /// Returns `true` if this value is positive infinity or negative infinity and
-    /// false otherwise.
+    /// Returns `true` if this value is positive infinity or negative infinity, and
+    /// `false` otherwise.
     ///
     /// ```
     /// use std::f32;
@@ -272,7 +272,7 @@ impl f32 {
         }
     }
 
-    /// Returns `true` if and only if `self` has a positive sign, including `+0.0`, `NaN`s with
+    /// Returns `true` if `self` has a positive sign, including `+0.0`, `NaN`s with
     /// positive sign bit and positive infinity.
     ///
     /// ```
@@ -288,7 +288,7 @@ impl f32 {
         !self.is_sign_negative()
     }
 
-    /// Returns `true` if and only if `self` has a negative sign, including `-0.0`, `NaN`s with
+    /// Returns `true` if `self` has a negative sign, including `-0.0`, `NaN`s with
     /// negative sign bit and negative infinity.
     ///
     /// ```
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index b6773915481..c3677f8c8fa 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -144,7 +144,7 @@ pub mod consts {
 #[lang = "f64"]
 #[cfg(not(test))]
 impl f64 {
-    /// Returns `true` if this value is `NaN` and false otherwise.
+    /// Returns `true` if this value is `NaN`.
     ///
     /// ```
     /// use std::f64;
@@ -169,8 +169,8 @@ impl f64 {
         f64::from_bits(self.to_bits() & 0x7fff_ffff_ffff_ffff)
     }
 
-    /// Returns `true` if this value is positive infinity or negative infinity and
-    /// false otherwise.
+    /// Returns `true` if this value is positive infinity or negative infinity, and
+    /// `false` otherwise.
     ///
     /// ```
     /// use std::f64;
@@ -272,7 +272,7 @@ impl f64 {
         }
     }
 
-    /// Returns `true` if and only if `self` has a positive sign, including `+0.0`, `NaN`s with
+    /// Returns `true` if `self` has a positive sign, including `+0.0`, `NaN`s with
     /// positive sign bit and positive infinity.
     ///
     /// ```
@@ -296,7 +296,7 @@ impl f64 {
         self.is_sign_positive()
     }
 
-    /// Returns `true` if and only if `self` has a negative sign, including `-0.0`, `NaN`s with
+    /// Returns `true` if `self` has a negative sign, including `-0.0`, `NaN`s with
     /// negative sign bit and negative infinity.
     ///
     /// ```
diff --git a/src/libcore/num/mod.rs b/src/libcore/num/mod.rs
index f80f8392827..6fb67ea9c9a 100644
--- a/src/libcore/num/mod.rs
+++ b/src/libcore/num/mod.rs
@@ -52,7 +52,7 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
             }
 
             impl $Ty {
-                /// Create a non-zero without checking the value.
+                /// Creates a non-zero without checking the value.
                 ///
                 /// # Safety
                 ///
@@ -63,7 +63,7 @@ assert_eq!(size_of::<Option<core::num::", stringify!($Ty), ">>(), size_of::<", s
                     $Ty(n)
                 }
 
-                /// Create a non-zero if the given value is not zero.
+                /// Creates a non-zero if the given value is not zero.
                 #[$stability]
                 #[inline]
                 pub fn new(n: $Int) -> Option<Self> {
@@ -882,17 +882,38 @@ $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[cfg(stage0)]
             pub fn saturating_add(self, rhs: Self) -> Self {
-                #[cfg(stage0)]
                 match self.checked_add(rhs) {
                     Some(x) => x,
                     None if rhs >= 0 => Self::max_value(),
                     None => Self::min_value(),
                 }
-                #[cfg(not(stage0))]
-                {
-                    intrinsics::saturating_add(self, rhs)
-                }
+            }
+
+        }
+
+        doc_comment! {
+            concat!("Saturating integer addition. Computes `self + rhs`, saturating at the numeric
+bounds instead of overflowing.
+
+# Examples
+
+Basic usage:
+
+```
+", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_add(1), 101);
+assert_eq!(", stringify!($SelfT), "::max_value().saturating_add(100), ", stringify!($SelfT),
+"::max_value());",
+$EndFeature, "
+```"),
+
+            #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_const_unstable(feature = "const_saturating_int_methods")]
+            #[inline]
+            #[cfg(not(stage0))]
+            pub const fn saturating_add(self, rhs: Self) -> Self {
+                intrinsics::saturating_add(self, rhs)
             }
         }
 
@@ -912,17 +933,36 @@ $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[cfg(stage0)]
             pub fn saturating_sub(self, rhs: Self) -> Self {
-                #[cfg(stage0)]
                 match self.checked_sub(rhs) {
                     Some(x) => x,
                     None if rhs >= 0 => Self::min_value(),
                     None => Self::max_value(),
                 }
-                #[cfg(not(stage0))]
-                {
-                    intrinsics::saturating_sub(self, rhs)
-                }
+            }
+        }
+
+        doc_comment! {
+            concat!("Saturating integer subtraction. Computes `self - rhs`, saturating at the
+numeric bounds instead of overflowing.
+
+# Examples
+
+Basic usage:
+
+```
+", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_sub(127), -27);
+assert_eq!(", stringify!($SelfT), "::min_value().saturating_sub(100), ", stringify!($SelfT),
+"::min_value());",
+$EndFeature, "
+```"),
+            #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_const_unstable(feature = "const_saturating_int_methods")]
+            #[inline]
+            #[cfg(not(stage0))]
+            pub const fn saturating_sub(self, rhs: Self) -> Self {
+                intrinsics::saturating_sub(self, rhs)
             }
         }
 
@@ -2753,16 +2793,34 @@ assert_eq!(200u8.saturating_add(127), 255);", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[cfg(stage0)]
             pub fn saturating_add(self, rhs: Self) -> Self {
-                #[cfg(stage0)]
                 match self.checked_add(rhs) {
                     Some(x) => x,
                     None => Self::max_value(),
                 }
-                #[cfg(not(stage0))]
-                {
-                    intrinsics::saturating_add(self, rhs)
-                }
+            }
+        }
+
+        doc_comment! {
+            concat!("Saturating integer addition. Computes `self + rhs`, saturating at
+the numeric bounds instead of overflowing.
+
+# Examples
+
+Basic usage:
+
+```
+", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_add(1), 101);
+assert_eq!(200u8.saturating_add(127), 255);", $EndFeature, "
+```"),
+
+            #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_const_unstable(feature = "const_saturating_int_methods")]
+            #[inline]
+            #[cfg(not(stage0))]
+            pub const fn saturating_add(self, rhs: Self) -> Self {
+                intrinsics::saturating_add(self, rhs)
             }
         }
 
@@ -2780,16 +2838,33 @@ assert_eq!(13", stringify!($SelfT), ".saturating_sub(127), 0);", $EndFeature, "
 ```"),
             #[stable(feature = "rust1", since = "1.0.0")]
             #[inline]
+            #[cfg(stage0)]
             pub fn saturating_sub(self, rhs: Self) -> Self {
-                #[cfg(stage0)]
                 match self.checked_sub(rhs) {
                     Some(x) => x,
                     None => Self::min_value(),
                 }
-                #[cfg(not(stage0))]
-                {
-                    intrinsics::saturating_sub(self, rhs)
-                }
+            }
+        }
+
+        doc_comment! {
+            concat!("Saturating integer subtraction. Computes `self - rhs`, saturating
+at the numeric bounds instead of overflowing.
+
+# Examples
+
+Basic usage:
+
+```
+", $Feature, "assert_eq!(100", stringify!($SelfT), ".saturating_sub(27), 73);
+assert_eq!(13", stringify!($SelfT), ".saturating_sub(127), 0);", $EndFeature, "
+```"),
+            #[stable(feature = "rust1", since = "1.0.0")]
+            #[rustc_const_unstable(feature = "const_saturating_int_methods")]
+            #[inline]
+            #[cfg(not(stage0))]
+            pub const fn saturating_sub(self, rhs: Self) -> Self {
+                intrinsics::saturating_sub(self, rhs)
             }
         }
 
diff --git a/src/libcore/ops/arith.rs b/src/libcore/ops/arith.rs
index 7d8bf18d33a..0252edee231 100644
--- a/src/libcore/ops/arith.rs
+++ b/src/libcore/ops/arith.rs
@@ -49,7 +49,7 @@
 /// }
 ///
 /// // Notice that the implementation uses the associated type `Output`.
-/// impl<T: Add<Output=T>> Add for Point<T> {
+/// impl<T: Add<Output = T>> Add for Point<T> {
 ///     type Output = Point<T>;
 ///
 ///     fn add(self, other: Point<T>) -> Point<T> {
@@ -157,7 +157,7 @@ add_impl! { usize u8 u16 u32 u64 u128 isize i8 i16 i32 i64 i128 f32 f64 }
 /// }
 ///
 /// // Notice that the implementation uses the associated type `Output`.
-/// impl<T: Sub<Output=T>> Sub for Point<T> {
+/// impl<T: Sub<Output = T>> Sub for Point<T> {
 ///     type Output = Point<T>;
 ///
 ///     fn sub(self, other: Point<T>) -> Point<T> {
@@ -518,7 +518,7 @@ pub trait Rem<RHS=Self> {
 
 macro_rules! rem_impl_integer {
     ($($t:ty)*) => ($(
-        /// This operation satisfies `n % d == n - (n / d) * d`.  The
+        /// This operation satisfies `n % d == n - (n / d) * d`. The
         /// result has the same sign as the left operand.
         #[stable(feature = "rust1", since = "1.0.0")]
         impl Rem for $t {
diff --git a/src/libcore/ops/function.rs b/src/libcore/ops/function.rs
index 3a1d765f7b8..c69f5fd9896 100644
--- a/src/libcore/ops/function.rs
+++ b/src/libcore/ops/function.rs
@@ -62,7 +62,7 @@
     label="expected an `Fn<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use]
+#[must_use = "closures are lazy and do nothing unless called"]
 pub trait Fn<Args> : FnMut<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -141,7 +141,7 @@ pub trait Fn<Args> : FnMut<Args> {
     label="expected an `FnMut<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use]
+#[must_use = "closures are lazy and do nothing unless called"]
 pub trait FnMut<Args> : FnOnce<Args> {
     /// Performs the call operation.
     #[unstable(feature = "fn_traits", issue = "29625")]
@@ -220,7 +220,7 @@ pub trait FnMut<Args> : FnOnce<Args> {
     label="expected an `FnOnce<{Args}>` closure, found `{Self}`",
 )]
 #[fundamental] // so that regex can rely that `&str: !FnMut`
-#[must_use]
+#[must_use = "closures are lazy and do nothing unless called"]
 pub trait FnOnce<Args> {
     /// The returned type after the call operator is used.
     #[stable(feature = "fn_once_output", since = "1.12.0")]
diff --git a/src/libcore/ops/range.rs b/src/libcore/ops/range.rs
index 815a4cfeed8..b3dd5d20299 100644
--- a/src/libcore/ops/range.rs
+++ b/src/libcore/ops/range.rs
@@ -52,7 +52,7 @@ impl fmt::Debug for RangeFull {
 /// (`start..end`).
 ///
 /// The `Range` `start..end` contains all values with `x >= start` and
-/// `x < end`.  It is empty unless `start < end`.
+/// `x < end`. It is empty unless `start < end`.
 ///
 /// # Examples
 ///
@@ -297,7 +297,7 @@ impl<Idx: PartialOrd<Idx>> RangeTo<Idx> {
 /// A range bounded inclusively below and above (`start..=end`).
 ///
 /// The `RangeInclusive` `start..=end` contains all values with `x >= start`
-/// and `x <= end`.  It is empty unless `start <= end`.
+/// and `x <= end`. It is empty unless `start <= end`.
 ///
 /// This iterator is [fused], but the specific values of `start` and `end` after
 /// iteration has finished are **unspecified** other than that [`.is_empty()`]
diff --git a/src/libcore/ops/try.rs b/src/libcore/ops/try.rs
index 380bd12131c..9fa2c81954e 100644
--- a/src/libcore/ops/try.rs
+++ b/src/libcore/ops/try.rs
@@ -1,7 +1,7 @@
 /// A trait for customizing the behavior of the `?` operator.
 ///
 /// A type implementing `Try` is one that has a canonical way to view it
-/// in terms of a success/failure dichotomy.  This trait allows both
+/// in terms of a success/failure dichotomy. This trait allows both
 /// extracting those success or failure values from an existing instance and
 /// creating a new instance from a success or failure value.
 #[unstable(feature = "try_trait", issue = "42327")]
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index 0e54397db02..76ef36ac309 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -214,7 +214,7 @@ impl<T> Option<T> {
     ///
     /// # Examples
     ///
-    /// Convert an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, preserving the original.
+    /// Converts an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, preserving the original.
     /// The [`map`] method takes the `self` argument by value, consuming the original,
     /// so this technique uses `as_ref` to first take an `Option` to a reference
     /// to the value inside the original.
@@ -395,7 +395,7 @@ impl<T> Option<T> {
     ///
     /// # Examples
     ///
-    /// Convert an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, consuming the original:
+    /// Converts an `Option<`[`String`]`>` into an `Option<`[`usize`]`>`, consuming the original:
     ///
     /// [`String`]: ../../std/string/struct.String.html
     /// [`usize`]: ../../std/primitive.usize.html
@@ -963,7 +963,7 @@ impl<T: Default> Option<T> {
     ///
     /// # Examples
     ///
-    /// Convert a string to an integer, turning poorly-formed strings
+    /// Converts a string to an integer, turning poorly-formed strings
     /// into 0 (the default value for integers). [`parse`] converts
     /// a string to any other type that implements [`FromStr`], returning
     /// [`None`] on error.
diff --git a/src/libcore/pin.rs b/src/libcore/pin.rs
index 56a32c928fb..ee9098d73ee 100644
--- a/src/libcore/pin.rs
+++ b/src/libcore/pin.rs
@@ -199,7 +199,7 @@ impl<P: Deref> Pin<P> {
         Pin { pointer }
     }
 
-    /// Get a pinned shared reference from this pinned pointer.
+    /// Gets a pinned shared reference from this pinned pointer.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
     pub fn as_ref(self: &Pin<P>) -> Pin<&P::Target> {
@@ -208,7 +208,7 @@ impl<P: Deref> Pin<P> {
 }
 
 impl<P: DerefMut> Pin<P> {
-    /// Get a pinned mutable reference from this pinned pointer.
+    /// Gets a pinned mutable reference from this pinned pointer.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
     pub fn as_mut(self: &mut Pin<P>) -> Pin<&mut P::Target> {
@@ -247,7 +247,7 @@ impl<'a, T: ?Sized> Pin<&'a T> {
         Pin::new_unchecked(new_pointer)
     }
 
-    /// Get a shared reference out of a pin.
+    /// Gets a shared reference out of a pin.
     ///
     /// Note: `Pin` also implements `Deref` to the target, which can be used
     /// to access the inner value. However, `Deref` only provides a reference
@@ -262,14 +262,14 @@ impl<'a, T: ?Sized> Pin<&'a T> {
 }
 
 impl<'a, T: ?Sized> Pin<&'a mut T> {
-    /// Convert this `Pin<&mut T>` into a `Pin<&T>` with the same lifetime.
+    /// Converts this `Pin<&mut T>` into a `Pin<&T>` with the same lifetime.
     #[stable(feature = "pin", since = "1.33.0")]
     #[inline(always)]
     pub fn into_ref(self: Pin<&'a mut T>) -> Pin<&'a T> {
         Pin { pointer: self.pointer }
     }
 
-    /// Get a mutable reference to the data inside of this `Pin`.
+    /// Gets a mutable reference to the data inside of this `Pin`.
     ///
     /// This requires that the data inside this `Pin` is `Unpin`.
     ///
@@ -286,7 +286,7 @@ impl<'a, T: ?Sized> Pin<&'a mut T> {
         self.pointer
     }
 
-    /// Get a mutable reference to the data inside of this `Pin`.
+    /// Gets a mutable reference to the data inside of this `Pin`.
     ///
     /// # Safety
     ///
diff --git a/src/libcore/ptr.rs b/src/libcore/ptr.rs
index 02eef07afd7..866c8d0896b 100644
--- a/src/libcore/ptr.rs
+++ b/src/libcore/ptr.rs
@@ -12,7 +12,7 @@
 //! to access only a single value, in which case the documentation omits the size
 //! and implicitly assumes it to be `size_of::<T>()` bytes.
 //!
-//! The precise rules for validity are not determined yet.  The guarantees that are
+//! The precise rules for validity are not determined yet. The guarantees that are
 //! provided at this point are very minimal:
 //!
 //! * A [null] pointer is *never* valid, not even for accesses of [size zero][zst].
@@ -104,7 +104,7 @@ pub use intrinsics::write_bytes;
 ///
 /// * `to_drop` must be [valid] for reads.
 ///
-/// * `to_drop` must be properly aligned.  See the example below for how to drop
+/// * `to_drop` must be properly aligned. See the example below for how to drop
 ///   an unaligned pointer.
 ///
 /// Additionally, if `T` is not [`Copy`], using the pointed-to value after
@@ -135,7 +135,7 @@ pub use intrinsics::write_bytes;
 /// unsafe {
 ///     // Get a raw pointer to the last element in `v`.
 ///     let ptr = &mut v[1] as *mut _;
-///     // Shorten `v` to prevent the last item from being dropped.  We do that first,
+///     // Shorten `v` to prevent the last item from being dropped. We do that first,
 ///     // to prevent issues if the `drop_in_place` below panics.
 ///     v.set_len(1);
 ///     // Without a call `drop_in_place`, the last item would never be dropped,
@@ -531,7 +531,7 @@ pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
 ///
 /// `read` creates a bitwise copy of `T`, regardless of whether `T` is [`Copy`].
 /// If `T` is not [`Copy`], using both the returned value and the value at
-/// `*src` can violate memory safety.  Note that assigning to `*src` counts as a
+/// `*src` can violate memory safety. Note that assigning to `*src` counts as a
 /// use because it will attempt to drop the value at `*src`.
 ///
 /// [`write`] can be used to overwrite data without causing it to be dropped.
@@ -573,7 +573,7 @@ pub unsafe fn replace<T>(dst: *mut T, mut src: T) -> T {
 pub unsafe fn read<T>(src: *const T) -> T {
     let mut tmp = MaybeUninit::<T>::uninitialized();
     copy_nonoverlapping(src, tmp.as_mut_ptr(), 1);
-    tmp.into_inner()
+    tmp.into_initialized()
 }
 
 /// Reads the value from `src` without moving it. This leaves the
@@ -588,7 +588,7 @@ pub unsafe fn read<T>(src: *const T) -> T {
 /// * `src` must be [valid] for reads.
 ///
 /// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
-/// whether `T` is [`Copy`].  If `T` is not [`Copy`], using both the returned
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
 /// value and the value at `*src` can [violate memory safety][read-ownership].
 ///
 /// Note that even if `T` has size `0`, the pointer must be non-NULL.
@@ -642,7 +642,7 @@ pub unsafe fn read_unaligned<T>(src: *const T) -> T {
     copy_nonoverlapping(src as *const u8,
                         tmp.as_mut_ptr() as *mut u8,
                         mem::size_of::<T>());
-    tmp.into_inner()
+    tmp.into_initialized()
 }
 
 /// Overwrites a memory location with the given value without reading or
@@ -825,7 +825,7 @@ pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
 ///
 /// The compiler shouldn't change the relative order or number of volatile
 /// memory operations. However, volatile memory operations on zero-sized types
-/// (e.g., if a zero-sized type is passed to `read_volatile`) are no-ops
+/// (e.g., if a zero-sized type is passed to `read_volatile`) are noops
 /// and may be ignored.
 ///
 /// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
@@ -839,7 +839,7 @@ pub unsafe fn write_unaligned<T>(dst: *mut T, src: T) {
 /// * `src` must be properly aligned.
 ///
 /// Like [`read`], `read_unaligned` creates a bitwise copy of `T`, regardless of
-/// whether `T` is [`Copy`].  If `T` is not [`Copy`], using both the returned
+/// whether `T` is [`Copy`]. If `T` is not [`Copy`], using both the returned
 /// value and the value at `*src` can [violate memory safety][read-ownership].
 /// However, storing non-[`Copy`] types in volatile memory is almost certainly
 /// incorrect.
@@ -903,7 +903,7 @@ pub unsafe fn read_volatile<T>(src: *const T) -> T {
 ///
 /// The compiler shouldn't change the relative order or number of volatile
 /// memory operations. However, volatile memory operations on zero-sized types
-/// (e.g., if a zero-sized type is passed to `write_volatile`) are no-ops
+/// (e.g., if a zero-sized type is passed to `write_volatile`) are noops
 /// and may be ignored.
 ///
 /// [c11]: http://www.open-std.org/jtc1/sc22/wg14/www/docs/n1570.pdf
@@ -1093,7 +1093,7 @@ impl<T: ?Sized> *const T {
     /// unless `x` and `y` point into the same allocated object.
     ///
     /// Always use `.offset(count)` instead when possible, because `offset`
-    /// allows the compiler to optimize better.  If you need to cross object
+    /// allows the compiler to optimize better. If you need to cross object
     /// boundaries, cast the pointer to an integer and do the arithmetic there.
     ///
     /// # Examples
@@ -1712,7 +1712,7 @@ impl<T: ?Sized> *mut T {
     /// unless `x` and `y` point into the same allocated object.
     ///
     /// Always use `.offset(count)` instead when possible, because `offset`
-    /// allows the compiler to optimize better.  If you need to cross object
+    /// allows the compiler to optimize better. If you need to cross object
     /// boundaries, cast the pointer to an integer and do the arithmetic there.
     ///
     /// # Examples
@@ -2473,7 +2473,7 @@ impl<T: ?Sized> PartialEq for *mut T {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: ?Sized> Eq for *mut T {}
 
-/// Compare raw pointers for equality.
+/// Compares raw pointers for equality.
 ///
 /// This is the same as using the `==` operator, but less generic:
 /// the arguments have to be `*const T` raw pointers,
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index 1ebf0714e23..92d29f6ee8a 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -896,7 +896,7 @@ impl<T: Default, E> Result<T, E> {
     ///
     /// # Examples
     ///
-    /// Convert a string to an integer, turning poorly-formed strings
+    /// Converts a string to an integer, turning poorly-formed strings
     /// into 0 (the default value for integers). [`parse`] converts
     /// a string to any other type that implements [`FromStr`], returning an
     /// [`Err`] on error.
diff --git a/src/libcore/slice/memchr.rs b/src/libcore/slice/memchr.rs
index 312838a170c..cbba546b8da 100644
--- a/src/libcore/slice/memchr.rs
+++ b/src/libcore/slice/memchr.rs
@@ -11,7 +11,7 @@ const HI_U64: u64 = 0x8080808080808080;
 const LO_USIZE: usize = LO_U64 as usize;
 const HI_USIZE: usize = HI_U64 as usize;
 
-/// Returns whether `x` contains any zero byte.
+/// Returns `true` if `x` contains any zero byte.
 ///
 /// From *Matters Computational*, J. Arndt:
 ///
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index d062da0c247..acca9748372 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -1197,7 +1197,7 @@ impl<T> [T] {
 
     /// Returns an iterator over subslices separated by elements that match
     /// `pred` limited to returning at most `n` items. This starts at the end of
-    /// the slice and works backwards.  The matched element is not contained in
+    /// the slice and works backwards. The matched element is not contained in
     /// the subslices.
     ///
     /// The last element returned, if any, will contain the remainder of the
@@ -3145,7 +3145,7 @@ unsafe impl<T: Sync> Sync for Iter<'_, T> {}
 unsafe impl<T: Sync> Send for Iter<'_, T> {}
 
 impl<'a, T> Iter<'a, T> {
-    /// View the underlying data as a subslice of the original data.
+    /// Views the underlying data as a subslice of the original data.
     ///
     /// This has the same lifetime as the original slice, and so the
     /// iterator can continue to be used while this exists.
@@ -3247,7 +3247,7 @@ unsafe impl<T: Sync> Sync for IterMut<'_, T> {}
 unsafe impl<T: Send> Send for IterMut<'_, T> {}
 
 impl<'a, T> IterMut<'a, T> {
-    /// View the underlying data as a subslice of the original data.
+    /// Views the underlying data as a subslice of the original data.
     ///
     /// To avoid creating `&mut` references that alias, this is forced
     /// to consume the iterator.
@@ -4123,7 +4123,7 @@ pub struct ChunksExact<'a, T:'a> {
 }
 
 impl<'a, T> ChunksExact<'a, T> {
-    /// Return the remainder of the original slice that is not going to be
+    /// Returns the remainder of the original slice that is not going to be
     /// returned by the iterator. The returned slice has at most `chunk_size-1`
     /// elements.
     #[stable(feature = "chunks_exact", since = "1.31.0")]
@@ -4247,7 +4247,7 @@ pub struct ChunksExactMut<'a, T:'a> {
 }
 
 impl<'a, T> ChunksExactMut<'a, T> {
-    /// Return the remainder of the original slice that is not going to be
+    /// Returns the remainder of the original slice that is not going to be
     /// returned by the iterator. The returned slice has at most `chunk_size-1`
     /// elements.
     #[stable(feature = "chunks_exact", since = "1.31.0")]
@@ -4619,7 +4619,7 @@ pub struct RChunksExact<'a, T:'a> {
 }
 
 impl<'a, T> RChunksExact<'a, T> {
-    /// Return the remainder of the original slice that is not going to be
+    /// Returns the remainder of the original slice that is not going to be
     /// returned by the iterator. The returned slice has at most `chunk_size-1`
     /// elements.
     #[stable(feature = "rchunks", since = "1.31.0")]
@@ -4744,7 +4744,7 @@ pub struct RChunksExactMut<'a, T:'a> {
 }
 
 impl<'a, T> RChunksExactMut<'a, T> {
-    /// Return the remainder of the original slice that is not going to be
+    /// Returns the remainder of the original slice that is not going to be
     /// returned by the iterator. The returned slice has at most `chunk_size-1`
     /// elements.
     #[stable(feature = "rchunks", since = "1.31.0")]
diff --git a/src/libcore/slice/rotate.rs b/src/libcore/slice/rotate.rs
index 52677713f5a..9b35b51349a 100644
--- a/src/libcore/slice/rotate.rs
+++ b/src/libcore/slice/rotate.rs
@@ -26,7 +26,7 @@ impl<T> RawArray<T> {
 }
 
 /// Rotates the range `[mid-left, mid+right)` such that the element at `mid`
-/// becomes the first element.  Equivalently, rotates the range `left`
+/// becomes the first element. Equivalently, rotates the range `left`
 /// elements to the left or `right` elements to the right.
 ///
 /// # Safety
@@ -36,10 +36,10 @@ impl<T> RawArray<T> {
 /// # Algorithm
 ///
 /// For longer rotations, swap the left-most `delta = min(left, right)`
-/// elements with the right-most `delta` elements.  LLVM vectorizes this,
+/// elements with the right-most `delta` elements. LLVM vectorizes this,
 /// which is profitable as we only reach this step for a "large enough"
-/// rotation.  Doing this puts `delta` elements on the larger side into the
-/// correct position, leaving a smaller rotate problem.  Demonstration:
+/// rotation. Doing this puts `delta` elements on the larger side into the
+/// correct position, leaving a smaller rotate problem. Demonstration:
 ///
 /// ```text
 /// [ 6 7 8 9 10 11 12 13 . 1 2 3 4 5 ]
diff --git a/src/libcore/str/mod.rs b/src/libcore/str/mod.rs
index 130142103a9..363eae04f03 100644
--- a/src/libcore/str/mod.rs
+++ b/src/libcore/str/mod.rs
@@ -1,6 +1,6 @@
-//! String manipulation
+//! String manipulation.
 //!
-//! For more details, see std::str
+//! For more details, see the `std::str` module.
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
@@ -8,10 +8,13 @@ use self::pattern::Pattern;
 use self::pattern::{Searcher, ReverseSearcher, DoubleEndedSearcher};
 
 use char;
-use fmt;
+use fmt::{self, Write};
 use iter::{Map, Cloned, FusedIterator, TrustedLen, TrustedRandomAccess, Filter};
+use iter::{Flatten, FlatMap, Chain};
 use slice::{self, SliceIndex, Split as SliceSplit};
 use mem;
+use ops::Try;
+use option;
 
 pub mod pattern;
 
@@ -226,7 +229,7 @@ impl Utf8Error {
     #[stable(feature = "utf8_error", since = "1.5.0")]
     pub fn valid_up_to(&self) -> usize { self.valid_up_to }
 
-    /// Provide more information about the failure:
+    /// Provides more information about the failure:
     ///
     /// * `None`: the end of the input was reached unexpectedly.
     ///   `self.valid_up_to()` is 1 to 3 bytes from the end of the input.
@@ -612,7 +615,7 @@ impl<'a> DoubleEndedIterator for Chars<'a> {
 impl FusedIterator for Chars<'_> {}
 
 impl<'a> Chars<'a> {
-    /// View the underlying data as a subslice of the original data.
+    /// Views the underlying data as a subslice of the original data.
     ///
     /// This has the same lifetime as the original slice, and so the
     /// iterator can continue to be used while this exists.
@@ -702,7 +705,7 @@ impl<'a> DoubleEndedIterator for CharIndices<'a> {
 impl FusedIterator for CharIndices<'_> {}
 
 impl<'a> CharIndices<'a> {
-    /// View the underlying data as a subslice of the original data.
+    /// Views the underlying data as a subslice of the original data.
     ///
     /// This has the same lifetime as the original slice, and so the
     /// iterator can continue to be used while this exists.
@@ -1345,33 +1348,14 @@ impl FusedIterator for Lines<'_> {}
 #[allow(deprecated)]
 pub struct LinesAny<'a>(Lines<'a>);
 
-/// A nameable, cloneable fn type
-#[derive(Clone)]
-struct LinesAnyMap;
-
-impl<'a> Fn<(&'a str,)> for LinesAnyMap {
-    #[inline]
-    extern "rust-call" fn call(&self, (line,): (&'a str,)) -> &'a str {
+impl_fn_for_zst! {
+    /// A nameable, cloneable fn type
+    #[derive(Clone)]
+    struct LinesAnyMap impl<'a> Fn = |line: &'a str| -> &'a str {
         let l = line.len();
         if l > 0 && line.as_bytes()[l - 1] == b'\r' { &line[0 .. l - 1] }
         else { line }
-    }
-}
-
-impl<'a> FnMut<(&'a str,)> for LinesAnyMap {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, (line,): (&'a str,)) -> &'a str {
-        Fn::call(&*self, (line,))
-    }
-}
-
-impl<'a> FnOnce<(&'a str,)> for LinesAnyMap {
-    type Output = &'a str;
-
-    #[inline]
-    extern "rust-call" fn call_once(self, (line,): (&'a str,)) -> &'a str {
-        Fn::call(&self, (line,))
-    }
+    };
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -1579,9 +1563,9 @@ mod traits {
 
     /// Implements ordering of strings.
     ///
-    /// Strings are ordered  lexicographically by their byte values.  This orders Unicode code
-    /// points based on their positions in the code charts.  This is not necessarily the same as
-    /// "alphabetical" order, which varies by language and locale.  Sorting strings according to
+    /// Strings are ordered  lexicographically by their byte values. This orders Unicode code
+    /// points based on their positions in the code charts. This is not necessarily the same as
+    /// "alphabetical" order, which varies by language and locale. Sorting strings according to
     /// culturally-accepted standards requires locale-specific data that is outside the scope of
     /// the `str` type.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -1607,9 +1591,9 @@ mod traits {
 
     /// Implements comparison operations on strings.
     ///
-    /// Strings are compared lexicographically by their byte values.  This compares Unicode code
-    /// points based on their positions in the code charts.  This is not necessarily the same as
-    /// "alphabetical" order, which varies by language and locale.  Comparing strings according to
+    /// Strings are compared lexicographically by their byte values. This compares Unicode code
+    /// points based on their positions in the code charts. This is not necessarily the same as
+    /// "alphabetical" order, which varies by language and locale. Comparing strings according to
     /// culturally-accepted standards requires locale-specific data that is outside the scope of
     /// the `str` type.
     #[stable(feature = "rust1", since = "1.0.0")]
@@ -2643,7 +2627,7 @@ impl str {
         Bytes(self.as_bytes().iter().cloned())
     }
 
-    /// Split a string slice by whitespace.
+    /// Splits a string slice by whitespace.
     ///
     /// The iterator returned will return string slices that are sub-slices of
     /// the original string slice, separated by any amount of whitespace.
@@ -2686,7 +2670,7 @@ impl str {
         SplitWhitespace { inner: self.split(IsWhitespace).filter(IsNotEmpty) }
     }
 
-    /// Split a string slice by ASCII whitespace.
+    /// Splits a string slice by ASCII whitespace.
     ///
     /// The iterator returned will return string slices that are sub-slices of
     /// the original string slice, separated by any amount of ASCII whitespace.
@@ -2727,7 +2711,7 @@ impl str {
         let inner = self
             .as_bytes()
             .split(IsAsciiWhitespace)
-            .filter(IsNotEmpty)
+            .filter(BytesIsNotEmpty)
             .map(UnsafeBytesToStr);
         SplitAsciiWhitespace { inner }
     }
@@ -2961,8 +2945,8 @@ impl str {
     /// An iterator over substrings of this string slice, separated by
     /// characters matched by a pattern.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that determines the
-    /// split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// # Iterator behavior
     ///
@@ -3078,8 +3062,8 @@ impl str {
     /// An iterator over substrings of the given string slice, separated by
     /// characters matched by a pattern and yielded in reverse order.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that determines the
-    /// split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// # Iterator behavior
     ///
@@ -3128,8 +3112,8 @@ impl str {
     /// An iterator over substrings of the given string slice, separated by
     /// characters matched by a pattern.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that determines the
-    /// split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// Equivalent to [`split`], except that the trailing substring
     /// is skipped if empty.
@@ -3175,8 +3159,8 @@ impl str {
     /// An iterator over substrings of `self`, separated by characters
     /// matched by a pattern and yielded in reverse order.
     ///
-    /// The pattern can be a simple `&str`, [`char`], or a closure that
-    /// determines the split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     /// Additional libraries might provide more complex patterns like
     /// regular expressions.
     ///
@@ -3222,8 +3206,8 @@ impl str {
     /// If `n` substrings are returned, the last substring (the `n`th substring)
     /// will contain the remainder of the string.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that determines the
-    /// split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// # Iterator behavior
     ///
@@ -3275,8 +3259,8 @@ impl str {
     /// If `n` substrings are returned, the last substring (the `n`th substring)
     /// will contain the remainder of the string.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that
-    /// determines the split.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// # Iterator behavior
     ///
@@ -3319,8 +3303,8 @@ impl str {
     /// An iterator over the disjoint matches of a pattern within the given string
     /// slice.
     ///
-    /// The pattern can be a `&str`, [`char`], or a closure that
-    /// determines if a character matches.
+    /// The pattern can be any type that implements the Pattern trait. Notable
+    /// examples are `&str`, [`char`], and closures that determines the split.
     ///
     /// # Iterator behavior
     ///
@@ -3504,7 +3488,7 @@ impl str {
     ///
     /// A string is a sequence of bytes. `start` in this context means the first
     /// position of that byte string; for a left-to-right language like English or
-    /// Russian, this will be left side; and for right-to-left languages like
+    /// Russian, this will be left side, and for right-to-left languages like
     /// like Arabic or Hebrew, this will be the right side.
     ///
     /// # Examples
@@ -3541,7 +3525,7 @@ impl str {
     ///
     /// A string is a sequence of bytes. `end` in this context means the last
     /// position of that byte string; for a left-to-right language like English or
-    /// Russian, this will be right side; and for right-to-left languages like
+    /// Russian, this will be right side, and for right-to-left languages like
     /// like Arabic or Hebrew, this will be the left side.
     ///
     /// # Examples
@@ -3787,7 +3771,7 @@ impl str {
     ///
     /// A string is a sequence of bytes. `start` in this context means the first
     /// position of that byte string; for a left-to-right language like English or
-    /// Russian, this will be left side; and for right-to-left languages like
+    /// Russian, this will be left side, and for right-to-left languages like
     /// like Arabic or Hebrew, this will be the right side.
     ///
     /// # Examples
@@ -3819,7 +3803,7 @@ impl str {
     ///
     /// A string is a sequence of bytes. `end` in this context means the last
     /// position of that byte string; for a left-to-right language like English or
-    /// Russian, this will be right side; and for right-to-left languages like
+    /// Russian, this will be right side, and for right-to-left languages like
     /// like Arabic or Hebrew, this will be the left side.
     ///
     /// # Examples
@@ -3964,6 +3948,146 @@ impl str {
         let me = unsafe { self.as_bytes_mut() };
         me.make_ascii_lowercase()
     }
+
+    /// Return an iterator that escapes each char in `s` with [`char::escape_debug`].
+    ///
+    /// Note: only extended grapheme codepoints that begin the string will be
+    /// escaped.
+    ///
+    /// [`char::escape_debug`]: ../std/primitive.char.html#method.escape_debug
+    ///
+    /// # Examples
+    ///
+    /// As an iterator:
+    ///
+    /// ```
+    /// for c in "❤\n!".escape_debug() {
+    ///     print!("{}", c);
+    /// }
+    /// println!();
+    /// ```
+    ///
+    /// Using `println!` directly:
+    ///
+    /// ```
+    /// println!("{}", "❤\n!".escape_debug());
+    /// ```
+    ///
+    ///
+    /// Both are equivalent to:
+    ///
+    /// ```
+    /// println!("❤\\n!");
+    /// ```
+    ///
+    /// Using `to_string`:
+    ///
+    /// ```
+    /// assert_eq!("❤\n!".escape_debug().to_string(), "❤\\n!");
+    /// ```
+    #[stable(feature = "str_escape", since = "1.34.0")]
+    pub fn escape_debug(&self) -> EscapeDebug {
+        let mut chars = self.chars();
+        EscapeDebug {
+            inner: chars.next()
+                .map(|first| first.escape_debug_ext(true))
+                .into_iter()
+                .flatten()
+                .chain(chars.flat_map(CharEscapeDebugContinue))
+        }
+    }
+
+    /// Return an iterator that escapes each char in `s` with [`char::escape_default`].
+    ///
+    /// [`char::escape_default`]: ../std/primitive.char.html#method.escape_default
+    ///
+    /// # Examples
+    ///
+    /// As an iterator:
+    ///
+    /// ```
+    /// for c in "❤\n!".escape_default() {
+    ///     print!("{}", c);
+    /// }
+    /// println!();
+    /// ```
+    ///
+    /// Using `println!` directly:
+    ///
+    /// ```
+    /// println!("{}", "❤\n!".escape_default());
+    /// ```
+    ///
+    ///
+    /// Both are equivalent to:
+    ///
+    /// ```
+    /// println!("\\u{{2764}}\n!");
+    /// ```
+    ///
+    /// Using `to_string`:
+    ///
+    /// ```
+    /// assert_eq!("❤\n!".escape_default().to_string(), "\\u{2764}\\n!");
+    /// ```
+    #[stable(feature = "str_escape", since = "1.34.0")]
+    pub fn escape_default(&self) -> EscapeDefault {
+        EscapeDefault { inner: self.chars().flat_map(CharEscapeDefault) }
+    }
+
+    /// Return an iterator that escapes each char in `s` with [`char::escape_unicode`].
+    ///
+    /// [`char::escape_unicode`]: ../std/primitive.char.html#method.escape_unicode
+    ///
+    /// # Examples
+    ///
+    /// As an iterator:
+    ///
+    /// ```
+    /// for c in "❤\n!".escape_unicode() {
+    ///     print!("{}", c);
+    /// }
+    /// println!();
+    /// ```
+    ///
+    /// Using `println!` directly:
+    ///
+    /// ```
+    /// println!("{}", "❤\n!".escape_unicode());
+    /// ```
+    ///
+    ///
+    /// Both are equivalent to:
+    ///
+    /// ```
+    /// println!("\\u{{2764}}\\u{{a}}\\u{{21}}");
+    /// ```
+    ///
+    /// Using `to_string`:
+    ///
+    /// ```
+    /// assert_eq!("❤\n!".escape_unicode().to_string(), "\\u{2764}\\u{a}\\u{21}");
+    /// ```
+    #[stable(feature = "str_escape", since = "1.34.0")]
+    pub fn escape_unicode(&self) -> EscapeUnicode {
+        EscapeUnicode { inner: self.chars().flat_map(CharEscapeUnicode) }
+    }
+}
+
+impl_fn_for_zst! {
+    #[derive(Clone)]
+    struct CharEscapeDebugContinue impl Fn = |c: char| -> char::EscapeDebug {
+        c.escape_debug_ext(false)
+    };
+
+    #[derive(Clone)]
+    struct CharEscapeUnicode impl Fn = |c: char| -> char::EscapeUnicode {
+        c.escape_unicode()
+    };
+    #[derive(Clone)]
+    struct CharEscapeDefault impl Fn = |c: char| -> char::EscapeDefault {
+        c.escape_default()
+    };
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
@@ -4011,102 +4135,36 @@ pub struct SplitWhitespace<'a> {
 #[stable(feature = "split_ascii_whitespace", since = "1.34.0")]
 #[derive(Clone, Debug)]
 pub struct SplitAsciiWhitespace<'a> {
-    inner: Map<Filter<SliceSplit<'a, u8, IsAsciiWhitespace>, IsNotEmpty>, UnsafeBytesToStr>,
-}
-
-#[derive(Clone)]
-struct IsWhitespace;
-
-impl FnOnce<(char, )> for IsWhitespace {
-    type Output = bool;
-
-    #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (char, )) -> bool {
-        self.call_mut(arg)
-    }
-}
-
-impl FnMut<(char, )> for IsWhitespace {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (char, )) -> bool {
-        arg.0.is_whitespace()
-    }
-}
-
-#[derive(Clone)]
-struct IsAsciiWhitespace;
-
-impl<'a> FnOnce<(&'a u8, )> for IsAsciiWhitespace {
-    type Output = bool;
-
-    #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (&u8, )) -> bool {
-        self.call_mut(arg)
-    }
+    inner: Map<Filter<SliceSplit<'a, u8, IsAsciiWhitespace>, BytesIsNotEmpty>, UnsafeBytesToStr>,
 }
 
-impl<'a> FnMut<(&'a u8, )> for IsAsciiWhitespace {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (&u8, )) -> bool {
-        arg.0.is_ascii_whitespace()
-    }
-}
-
-#[derive(Clone)]
-struct IsNotEmpty;
-
-impl<'a, 'b> FnOnce<(&'a &'b str, )> for IsNotEmpty {
-    type Output = bool;
-
-    #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (&'a &'b str, )) -> bool {
-        self.call_mut(arg)
-    }
-}
-
-impl<'a, 'b> FnMut<(&'a &'b str, )> for IsNotEmpty {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (&'a &'b str, )) -> bool {
-        !arg.0.is_empty()
-    }
-}
-
-impl<'a, 'b> FnOnce<(&'a &'b [u8], )> for IsNotEmpty {
-    type Output = bool;
-
-    #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (&'a &'b [u8], )) -> bool {
-        self.call_mut(arg)
-    }
-}
-
-impl<'a, 'b> FnMut<(&'a &'b [u8], )> for IsNotEmpty {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (&'a &'b [u8], )) -> bool {
-        !arg.0.is_empty()
-    }
-}
+impl_fn_for_zst! {
+    #[derive(Clone)]
+    struct IsWhitespace impl Fn = |c: char| -> bool {
+        c.is_whitespace()
+    };
 
-#[derive(Clone)]
-struct UnsafeBytesToStr;
+    #[derive(Clone)]
+    struct IsAsciiWhitespace impl Fn = |byte: &u8| -> bool {
+        byte.is_ascii_whitespace()
+    };
 
-impl<'a> FnOnce<(&'a [u8], )> for UnsafeBytesToStr {
-    type Output = &'a str;
+    #[derive(Clone)]
+    struct IsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b str| -> bool {
+        !s.is_empty()
+    };
 
-    #[inline]
-    extern "rust-call" fn call_once(mut self, arg: (&'a [u8], )) -> &'a str {
-        self.call_mut(arg)
-    }
-}
+    #[derive(Clone)]
+    struct BytesIsNotEmpty impl<'a, 'b> Fn = |s: &'a &'b [u8]| -> bool {
+        !s.is_empty()
+    };
 
-impl<'a> FnMut<(&'a [u8], )> for UnsafeBytesToStr {
-    #[inline]
-    extern "rust-call" fn call_mut(&mut self, arg: (&'a [u8], )) -> &'a str {
-        unsafe { from_utf8_unchecked(arg.0) }
-    }
+    #[derive(Clone)]
+    struct UnsafeBytesToStr impl<'a> Fn = |bytes: &'a [u8]| -> &'a str {
+        unsafe { from_utf8_unchecked(bytes) }
+    };
 }
 
-
 #[stable(feature = "split_whitespace", since = "1.1.0")]
 impl<'a> Iterator for SplitWhitespace<'a> {
     type Item = &'a str;
@@ -4216,3 +4274,74 @@ impl<'a> Iterator for EncodeUtf16<'a> {
 
 #[stable(feature = "fused", since = "1.26.0")]
 impl FusedIterator for EncodeUtf16<'_> {}
+
+/// The return type of [`str::escape_debug`].
+///
+/// [`str::escape_debug`]: ../../std/primitive.str.html#method.escape_debug
+#[stable(feature = "str_escape", since = "1.34.0")]
+#[derive(Clone, Debug)]
+pub struct EscapeDebug<'a> {
+    inner: Chain<
+        Flatten<option::IntoIter<char::EscapeDebug>>,
+        FlatMap<Chars<'a>, char::EscapeDebug, CharEscapeDebugContinue>
+    >,
+}
+
+/// The return type of [`str::escape_default`].
+///
+/// [`str::escape_default`]: ../../std/primitive.str.html#method.escape_default
+#[stable(feature = "str_escape", since = "1.34.0")]
+#[derive(Clone, Debug)]
+pub struct EscapeDefault<'a> {
+    inner: FlatMap<Chars<'a>, char::EscapeDefault, CharEscapeDefault>,
+}
+
+/// The return type of [`str::escape_unicode`].
+///
+/// [`str::escape_unicode`]: ../../std/primitive.str.html#method.escape_unicode
+#[stable(feature = "str_escape", since = "1.34.0")]
+#[derive(Clone, Debug)]
+pub struct EscapeUnicode<'a> {
+    inner: FlatMap<Chars<'a>, char::EscapeUnicode, CharEscapeUnicode>,
+}
+
+macro_rules! escape_types_impls {
+    ($( $Name: ident ),+) => {$(
+        #[stable(feature = "str_escape", since = "1.34.0")]
+        impl<'a> fmt::Display for $Name<'a> {
+            fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+                self.clone().try_for_each(|c| f.write_char(c))
+            }
+        }
+
+        #[stable(feature = "str_escape", since = "1.34.0")]
+        impl<'a> Iterator for $Name<'a> {
+            type Item = char;
+
+            #[inline]
+            fn next(&mut self) -> Option<char> { self.inner.next() }
+
+            #[inline]
+            fn size_hint(&self) -> (usize, Option<usize>) { self.inner.size_hint() }
+
+            #[inline]
+            fn try_fold<Acc, Fold, R>(&mut self, init: Acc, fold: Fold) -> R where
+                Self: Sized, Fold: FnMut(Acc, Self::Item) -> R, R: Try<Ok=Acc>
+            {
+                self.inner.try_fold(init, fold)
+            }
+
+            #[inline]
+            fn fold<Acc, Fold>(self, init: Acc, fold: Fold) -> Acc
+                where Fold: FnMut(Acc, Self::Item) -> Acc,
+            {
+                self.inner.fold(init, fold)
+            }
+        }
+
+        #[stable(feature = "str_escape", since = "1.34.0")]
+        impl<'a> FusedIterator for $Name<'a> {}
+    )+}
+}
+
+escape_types_impls!(EscapeDebug, EscapeDefault, EscapeUnicode);
diff --git a/src/libcore/str/pattern.rs b/src/libcore/str/pattern.rs
index 55a7ba181e5..2571780ad0b 100644
--- a/src/libcore/str/pattern.rs
+++ b/src/libcore/str/pattern.rs
@@ -1,7 +1,7 @@
 //! The string Pattern API.
 //!
-//! For more details, see the traits `Pattern`, `Searcher`,
-//! `ReverseSearcher` and `DoubleEndedSearcher`.
+//! For more details, see the traits [`Pattern`], [`Searcher`],
+//! [`ReverseSearcher`], and [`DoubleEndedSearcher`].
 
 #![unstable(feature = "pattern",
             reason = "API not fully fleshed out and ready to be stabilized",
@@ -117,7 +117,7 @@ pub unsafe trait Searcher<'a> {
     /// `[Reject(0, 1), Reject(1, 2), Match(2, 5), Reject(5, 8)]`
     fn next(&mut self) -> SearchStep;
 
-    /// Find the next `Match` result. See `next()`
+    /// Finds the next `Match` result. See `next()`
     ///
     /// Unlike next(), there is no guarantee that the returned ranges
     /// of this and next_reject will overlap. This will return (start_match, end_match),
@@ -134,7 +134,7 @@ pub unsafe trait Searcher<'a> {
         }
     }
 
-    /// Find the next `Reject` result. See `next()` and `next_match()`
+    /// Finds the next `Reject` result. See `next()` and `next_match()`
     ///
     /// Unlike next(), there is no guarantee that the returned ranges
     /// of this and next_match will overlap.
@@ -185,7 +185,7 @@ pub unsafe trait ReverseSearcher<'a>: Searcher<'a> {
     /// `[Reject(7, 8), Match(4, 7), Reject(1, 4), Reject(0, 1)]`
     fn next_back(&mut self) -> SearchStep;
 
-    /// Find the next `Match` result. See `next_back()`
+    /// Finds the next `Match` result. See `next_back()`
     #[inline]
     fn next_match_back(&mut self) -> Option<(usize, usize)>{
         loop {
@@ -197,7 +197,7 @@ pub unsafe trait ReverseSearcher<'a>: Searcher<'a> {
         }
     }
 
-    /// Find the next `Reject` result. See `next_back()`
+    /// Finds the next `Reject` result. See `next_back()`
     #[inline]
     fn next_reject_back(&mut self) -> Option<(usize, usize)>{
         loop {
diff --git a/src/libcore/task/poll.rs b/src/libcore/task/poll.rs
index 27b1139e15c..c811f96ace3 100644
--- a/src/libcore/task/poll.rs
+++ b/src/libcore/task/poll.rs
@@ -7,6 +7,7 @@ use result::Result;
 
 /// Indicates whether a value is available or if the current task has been
 /// scheduled to receive a wakeup instead.
+#[must_use = "this `Poll` may be a `Pending` variant, which should be handled"]
 #[derive(Copy, Clone, Debug, Eq, PartialEq, Ord, PartialOrd, Hash)]
 pub enum Poll<T> {
     /// Represents that a value is immediately ready.
@@ -21,7 +22,7 @@ pub enum Poll<T> {
 }
 
 impl<T> Poll<T> {
-    /// Change the ready value of this `Poll` with the closure provided
+    /// Changes the ready value of this `Poll` with the closure provided.
     pub fn map<U, F>(self, f: F) -> Poll<U>
         where F: FnOnce(T) -> U
     {
@@ -31,7 +32,7 @@ impl<T> Poll<T> {
         }
     }
 
-    /// Returns whether this is `Poll::Ready`
+    /// Returns `true` if this is `Poll::Ready`
     #[inline]
     pub fn is_ready(&self) -> bool {
         match *self {
@@ -40,7 +41,7 @@ impl<T> Poll<T> {
         }
     }
 
-    /// Returns whether this is `Poll::Pending`
+    /// Returns `true` if this is `Poll::Pending`
     #[inline]
     pub fn is_pending(&self) -> bool {
         !self.is_ready()
@@ -48,7 +49,7 @@ impl<T> Poll<T> {
 }
 
 impl<T, E> Poll<Result<T, E>> {
-    /// Change the success value of this `Poll` with the closure provided
+    /// Changes the success value of this `Poll` with the closure provided.
     pub fn map_ok<U, F>(self, f: F) -> Poll<Result<U, E>>
         where F: FnOnce(T) -> U
     {
@@ -59,7 +60,7 @@ impl<T, E> Poll<Result<T, E>> {
         }
     }
 
-    /// Change the error value of this `Poll` with the closure provided
+    /// Changes the error value of this `Poll` with the closure provided.
     pub fn map_err<U, F>(self, f: F) -> Poll<Result<T, U>>
         where F: FnOnce(E) -> U
     {
diff --git a/src/libcore/tests/cell.rs b/src/libcore/tests/cell.rs
index 56f295dff8e..73bdaab5861 100644
--- a/src/libcore/tests/cell.rs
+++ b/src/libcore/tests/cell.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 use core::cell::*;
 use core::default::Default;
 use std::mem::drop;
diff --git a/src/libcore/tests/fmt/mod.rs b/src/libcore/tests/fmt/mod.rs
index d86e21cf40b..b10b63fc484 100644
--- a/src/libcore/tests/fmt/mod.rs
+++ b/src/libcore/tests/fmt/mod.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 mod builders;
 mod float;
 mod num;
diff --git a/src/libcore/tests/hash/mod.rs b/src/libcore/tests/hash/mod.rs
index 135f4dfcac7..bf3039a7e51 100644
--- a/src/libcore/tests/hash/mod.rs
+++ b/src/libcore/tests/hash/mod.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 mod sip;
 
 use std::hash::{Hash, Hasher};
diff --git a/src/libcore/tests/iter.rs b/src/libcore/tests/iter.rs
index 0fa99745d90..51a6017de1b 100644
--- a/src/libcore/tests/iter.rs
+++ b/src/libcore/tests/iter.rs
@@ -190,6 +190,7 @@ fn test_iterator_step_by() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_iterator_step_by_nth() {
     let mut it = (0..16).step_by(5);
     assert_eq!(it.nth(0), Some(0));
@@ -208,6 +209,7 @@ fn test_iterator_step_by_nth() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_iterator_step_by_nth_overflow() {
     #[cfg(target_pointer_width = "8")]
     type Bigger = u16;
@@ -253,12 +255,14 @@ fn test_iterator_step_by_nth_overflow() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))]
 fn test_iterator_step_by_zero() {
     let mut it = (0..).step_by(0);
     it.next();
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_iterator_step_by_size_hint() {
     struct StubSizeHint(usize, Option<usize>);
     impl Iterator for StubSizeHint {
@@ -877,7 +881,7 @@ fn test_iterator_flat_map() {
     assert_eq!(i, ys.len());
 }
 
-/// Test `FlatMap::fold` with items already picked off the front and back,
+/// Tests `FlatMap::fold` with items already picked off the front and back,
 /// to make sure all parts of the `FlatMap` are folded correctly.
 #[test]
 fn test_iterator_flat_map_fold() {
@@ -915,7 +919,7 @@ fn test_iterator_flatten() {
     assert_eq!(i, ys.len());
 }
 
-/// Test `Flatten::fold` with items already picked off the front and back,
+/// Tests `Flatten::fold` with items already picked off the front and back,
 /// to make sure all parts of the `Flatten` are folded correctly.
 #[test]
 fn test_iterator_flatten_fold() {
@@ -1413,6 +1417,7 @@ fn test_rposition() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))]
 fn test_rposition_panic() {
     let v: [(Box<_>, Box<_>); 4] =
         [(box 0, box 0), (box 0, box 0),
@@ -1652,6 +1657,7 @@ fn test_range_inclusive_nth() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_range_step() {
     #![allow(deprecated)]
 
@@ -1675,6 +1681,7 @@ fn test_range_step() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_step_by_skip() {
     assert_eq!((0..640).step_by(128).skip(1).collect::<Vec<_>>(), [128, 256, 384, 512]);
     assert_eq!((0..=50).step_by(10).nth(3), Some(30));
@@ -1682,6 +1689,7 @@ fn test_step_by_skip() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_range_inclusive_step() {
     assert_eq!((0..=50).step_by(10).collect::<Vec<_>>(), [0, 10, 20, 30, 40, 50]);
     assert_eq!((0..=5).step_by(1).collect::<Vec<_>>(), [0, 1, 2, 3, 4, 5]);
diff --git a/src/libcore/tests/num/mod.rs b/src/libcore/tests/num/mod.rs
index a17c094679e..ab638e06cc1 100644
--- a/src/libcore/tests/num/mod.rs
+++ b/src/libcore/tests/num/mod.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 use core::convert::{TryFrom, TryInto};
 use core::cmp::PartialEq;
 use core::fmt::Debug;
diff --git a/src/libcore/tests/option.rs b/src/libcore/tests/option.rs
index b059b134868..1ba886ce037 100644
--- a/src/libcore/tests/option.rs
+++ b/src/libcore/tests/option.rs
@@ -69,6 +69,7 @@ fn test_option_dance() {
 }
 
 #[test] #[should_panic]
+#[cfg(not(miri))]
 fn test_option_too_much_dance() {
     struct A;
     let mut y = Some(A);
@@ -129,6 +130,7 @@ fn test_unwrap() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))]
 fn test_unwrap_panic1() {
     let x: Option<isize> = None;
     x.unwrap();
@@ -136,6 +138,7 @@ fn test_unwrap_panic1() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))]
 fn test_unwrap_panic2() {
     let x: Option<String> = None;
     x.unwrap();
diff --git a/src/libcore/tests/ptr.rs b/src/libcore/tests/ptr.rs
index 65c1a3e0254..57845590822 100644
--- a/src/libcore/tests/ptr.rs
+++ b/src/libcore/tests/ptr.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 use core::ptr::*;
 use core::cell::RefCell;
 
diff --git a/src/libcore/tests/result.rs b/src/libcore/tests/result.rs
index 1fab07526a0..7bfd396f68d 100644
--- a/src/libcore/tests/result.rs
+++ b/src/libcore/tests/result.rs
@@ -117,6 +117,7 @@ fn test_unwrap_or_else() {
 
 #[test]
 #[should_panic]
+#[cfg(not(miri))]
 pub fn test_unwrap_or_else_panic() {
     fn handler(msg: &'static str) -> isize {
         if msg == "I got this." {
@@ -138,6 +139,7 @@ pub fn test_expect_ok() {
 }
 #[test]
 #[should_panic(expected="Got expected error: \"All good\"")]
+#[cfg(not(miri))]
 pub fn test_expect_err() {
     let err: Result<isize, &'static str> = Err("All good");
     err.expect("Got expected error");
@@ -151,6 +153,7 @@ pub fn test_expect_err_err() {
 }
 #[test]
 #[should_panic(expected="Got expected ok: \"All good\"")]
+#[cfg(not(miri))]
 pub fn test_expect_err_ok() {
     let err: Result<&'static str, isize> = Ok("All good");
     err.expect_err("Got expected ok");
diff --git a/src/libcore/tests/slice.rs b/src/libcore/tests/slice.rs
index e210e83122c..04d646ea01d 100644
--- a/src/libcore/tests/slice.rs
+++ b/src/libcore/tests/slice.rs
@@ -782,6 +782,7 @@ mod slice_index {
     //  to be used in `should_panic`)
     #[test]
     #[should_panic(expected = "out of range")]
+    #[cfg(not(miri))]
     fn assert_range_eq_can_fail_by_panic() {
         assert_range_eq!([0, 1, 2], 0..5, [0, 1, 2]);
     }
@@ -791,6 +792,7 @@ mod slice_index {
     //  to be used in `should_panic`)
     #[test]
     #[should_panic(expected = "==")]
+    #[cfg(not(miri))]
     fn assert_range_eq_can_fail_by_inequality() {
         assert_range_eq!([0, 1, 2], 0..2, [0, 1, 2]);
     }
@@ -840,6 +842,7 @@ mod slice_index {
 
                 #[test]
                 #[should_panic(expected = $expect_msg)]
+                #[cfg(not(miri))]
                 fn index_fail() {
                     let v = $data;
                     let v: &[_] = &v;
@@ -848,6 +851,7 @@ mod slice_index {
 
                 #[test]
                 #[should_panic(expected = $expect_msg)]
+                #[cfg(not(miri))]
                 fn index_mut_fail() {
                     let mut v = $data;
                     let v: &mut [_] = &mut v;
@@ -1011,6 +1015,7 @@ fn test_rotate_right() {
 
 #[test]
 #[cfg(not(target_arch = "wasm32"))]
+#[cfg(not(miri))]
 fn sort_unstable() {
     use core::cmp::Ordering::{Equal, Greater, Less};
     use core::slice::heapsort;
@@ -1166,6 +1171,7 @@ pub mod memchr {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_align_to_simple() {
     let bytes = [1u8, 2, 3, 4, 5, 6, 7];
     let (prefix, aligned, suffix) = unsafe { bytes.align_to::<u16>() };
@@ -1181,6 +1187,7 @@ fn test_align_to_simple() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_align_to_zst() {
     let bytes = [1, 2, 3, 4, 5, 6, 7];
     let (prefix, aligned, suffix) = unsafe { bytes.align_to::<()>() };
@@ -1189,6 +1196,7 @@ fn test_align_to_zst() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_align_to_non_trivial() {
     #[repr(align(8))] struct U64(u64, u64);
     #[repr(align(8))] struct U64U64U32(u64, u64, u32);
@@ -1200,6 +1208,7 @@ fn test_align_to_non_trivial() {
 }
 
 #[test]
+#[cfg(not(miri))]
 fn test_align_to_empty_mid() {
     use core::mem;
 
@@ -1297,6 +1306,7 @@ fn test_copy_within() {
 
 #[test]
 #[should_panic(expected = "src is out of bounds")]
+#[cfg(not(miri))]
 fn test_copy_within_panics_src_too_long() {
     let mut bytes = *b"Hello, World!";
     // The length is only 13, so 14 is out of bounds.
@@ -1305,6 +1315,7 @@ fn test_copy_within_panics_src_too_long() {
 
 #[test]
 #[should_panic(expected = "dest is out of bounds")]
+#[cfg(not(miri))]
 fn test_copy_within_panics_dest_too_long() {
     let mut bytes = *b"Hello, World!";
     // The length is only 13, so a slice of length 4 starting at index 10 is out of bounds.
@@ -1312,6 +1323,7 @@ fn test_copy_within_panics_dest_too_long() {
 }
 #[test]
 #[should_panic(expected = "src end is before src start")]
+#[cfg(not(miri))]
 fn test_copy_within_panics_src_inverted() {
     let mut bytes = *b"Hello, World!";
     // 2 is greater than 1, so this range is invalid.
diff --git a/src/libcore/tests/time.rs b/src/libcore/tests/time.rs
index 6efd22572dc..d39bd06930a 100644
--- a/src/libcore/tests/time.rs
+++ b/src/libcore/tests/time.rs
@@ -1,3 +1,5 @@
+#![cfg(not(miri))]
+
 use core::time::Duration;
 
 #[test]
diff --git a/src/libcore/time.rs b/src/libcore/time.rs
index a751965dffa..ac7e11754aa 100644
--- a/src/libcore/time.rs
+++ b/src/libcore/time.rs
@@ -43,7 +43,7 @@ pub const NANOSECOND: Duration = Duration::from_nanos(1);
 /// timeouts.
 ///
 /// Each `Duration` is composed of a whole number of seconds and a fractional part
-/// represented in nanoseconds.  If the underlying system does not support
+/// represented in nanoseconds. If the underlying system does not support
 /// nanosecond-level precision, APIs binding a system timeout will typically round up
 /// the number of nanoseconds.
 ///
@@ -515,7 +515,7 @@ impl Duration {
         }
     }
 
-    /// Multiply `Duration` by `f64`.
+    /// Multiplies `Duration` by `f64`.
     ///
     /// # Panics
     /// This method will panic if result is not finite, negative or overflows `Duration`.