diff --git a/RELEASES.md b/RELEASES.md
index 39cef1e2a57..26dd5a5c7f6 100644
--- a/RELEASES.md
+++ b/RELEASES.md
@@ -1,3 +1,209 @@
+Version 1.26.0 (2018-05-10)
+==========================
+
+Language
+--------
+- [Closures now implement `Copy` and/or `Clone` if all captured variables
+  implement either or both traits.][49299]
+- [The inclusive range syntax e.g. `for x in 0..=10` is now stable.][47813]
+- [Stablise `'_`. The underscore lifetime can be used anywhere where a
+  lifetime can be elided.][49458]
+- [`impl Trait` is now stable allowing you to have abstract types in returns
+   or in function parameters.][49255] e.g. `fn foo() -> impl Iterator<Item=u8>` or
+  `fn open(path: impl AsRef<Path>)`.
+- [Pattern matching will now automatically apply dereferences.][49394]
+- [128-bit integers in the form of `u128` and `i128` are now stable.][49101]
+- [`main` can now return `Result<(), E: Debug>`][49162] in addition to `()`.
+- [A lot of operations are now available in a const context.][46882] E.g. You
+  can now index into constant arrays, reference and dereference into constants,
+  and use Tuple struct constructors.
+- [Fixed entry slice patterns are now stable.][48516] e.g.
+  ```rust
+  let points = [1, 2, 3, 4];
+  match points {
+      [1, 2, 3, 4] => println!("All points were sequential."),
+      _ => println!("Not all points were sequential."),
+  }
+  ```
+
+
+Compiler
+--------
+- [LLD is now used as the default linker for `wasm32-unknown-unknown`.][48125]
+- [Fixed exponential projection complexity on nested types.][48296]
+  This can provide up to a ~12% reduction in compile times for certain crates.
+- [Added the `--remap-path-prefix` option to rustc.][48359] Allowing you
+  to remap path prefixes outputted by the compiler.
+- [Added `powerpc-unknown-netbsd` target.][48281]
+
+Libraries
+---------
+- [Implemented `From<u16> for usize` & `From<{u8, i16}> for isize`.][49305]
+- [Added hexadecimal formatting for integers with fmt::Debug][48978]
+  e.g. `assert!(format!("{:02x?}", b"Foo\0") == "[46, 6f, 6f, 00]")`
+- [Implemented `Default, Hash` for `cmp::Reverse`.][48628]
+- [Optimized `str::repeat` being 8x faster in large cases.][48657]
+- [`ascii::escape_default` is now available in libcore.][48735]
+- [Trailing commas are now supported in std and core macros.][48056]
+- [Implemented `Copy, Clone` for `cmp::Reverse`][47379]
+- [Implemented `Clone` for `char::{ToLowercase, ToUppercase}`.][48629]
+
+Stabilized APIs
+---------------
+- [`*const T::add`]
+- [`*const T::copy_to_nonoverlapping`]
+- [`*const T::copy_to`]
+- [`*const T::read_unaligned`]
+- [`*const T::read_volatile`]
+- [`*const T::read`]
+- [`*const T::sub`]
+- [`*const T::wrapping_add`]
+- [`*const T::wrapping_sub`]
+- [`*mut T::add`]
+- [`*mut T::copy_to_nonoverlapping`]
+- [`*mut T::copy_to`]
+- [`*mut T::read_unaligned`]
+- [`*mut T::read_volatile`]
+- [`*mut T::read`]
+- [`*mut T::replace`]
+- [`*mut T::sub`]
+- [`*mut T::swap`]
+- [`*mut T::wrapping_add`]
+- [`*mut T::wrapping_sub`]
+- [`*mut T::write_bytes`]
+- [`*mut T::write_unaligned`]
+- [`*mut T::write_volatile`]
+- [`*mut T::write`]
+- [`Box::leak`]
+- [`FromUtf8Error::as_bytes`]
+- [`LocalKey::try_with`]
+- [`Option::cloned`]
+- [`btree_map::Entry::and_modify`]
+- [`fs::read_to_string`]
+- [`fs::read`]
+- [`fs::write`]
+- [`hash_map::Entry::and_modify`]
+- [`iter::FusedIterator`]
+- [`ops::RangeInclusive`]
+- [`ops::RangeToInclusive`]
+- [`process::id`]
+- [`slice::rotate_left`]
+- [`slice::rotate_right`]
+- [`String::retain`]
+
+
+Cargo
+-----
+- [Cargo will now output path to custom commands when `-v` is
+  passed with `--list`][cargo/5041]
+- [The Cargo binary version is now the same as the Rust version][cargo/5083]
+- [`Cargo.lock` files are now included in published crates.][cargo/5093]
+
+Misc
+----
+- [The second edition of "The Rust Programming Language" book is now recommended
+  over the first.][48404]
+
+Compatibility Notes
+-------------------
+
+- [aliasing a `Fn` trait as `dyn` no longer works.][48481] E.g. the following
+  syntax is now invalid.
+  ```
+  use std::ops::Fn as dyn;
+  fn g(_: Box<dyn(std::fmt::Debug)>) {}
+  ```
+- [The result of dereferences are no longer promoted to `'static`.][47408]
+  e.g.
+  ```rust
+  fn main() {
+      const PAIR: &(i32, i32) = &(0, 1);
+      let _reversed_pair: &'static _ = &(PAIR.1, PAIR.0); // Doesn't work
+  }
+  ```
+- [Deprecate `AsciiExt` trait in favor of inherent methods.][49109]
+- [`".e0"` will now no longer parse as `0.0` and will instead cause
+  an error.][48235]
+- [Removed hoedown from rustdoc.][48274]
+- [Bounds on higher-kinded lifetimes a hard error.][48326]
+
+[46882]: https://github.com/rust-lang/rust/pull/46882
+[47379]: https://github.com/rust-lang/rust/pull/47379
+[47408]: https://github.com/rust-lang/rust/pull/47408
+[47813]: https://github.com/rust-lang/rust/pull/47813
+[48056]: https://github.com/rust-lang/rust/pull/48056
+[48125]: https://github.com/rust-lang/rust/pull/48125
+[48166]: https://github.com/rust-lang/rust/pull/48166
+[48235]: https://github.com/rust-lang/rust/pull/48235
+[48274]: https://github.com/rust-lang/rust/pull/48274
+[48281]: https://github.com/rust-lang/rust/pull/48281
+[48296]: https://github.com/rust-lang/rust/pull/48296
+[48326]: https://github.com/rust-lang/rust/pull/48326
+[48359]: https://github.com/rust-lang/rust/pull/48359
+[48404]: https://github.com/rust-lang/rust/pull/48404
+[48481]: https://github.com/rust-lang/rust/pull/48481
+[48516]: https://github.com/rust-lang/rust/pull/48516
+[48628]: https://github.com/rust-lang/rust/pull/48628
+[48629]: https://github.com/rust-lang/rust/pull/48629
+[48657]: https://github.com/rust-lang/rust/pull/48657
+[48735]: https://github.com/rust-lang/rust/pull/48735
+[48978]: https://github.com/rust-lang/rust/pull/48978
+[49101]: https://github.com/rust-lang/rust/pull/49101
+[49109]: https://github.com/rust-lang/rust/pull/49109
+[49121]: https://github.com/rust-lang/rust/pull/49121
+[49162]: https://github.com/rust-lang/rust/pull/49162
+[49184]: https://github.com/rust-lang/rust/pull/49184
+[49234]: https://github.com/rust-lang/rust/pull/49234
+[49255]: https://github.com/rust-lang/rust/pull/49255
+[49299]: https://github.com/rust-lang/rust/pull/49299
+[49305]: https://github.com/rust-lang/rust/pull/49305
+[49394]: https://github.com/rust-lang/rust/pull/49394
+[49458]: https://github.com/rust-lang/rust/pull/49458
+[`*const T::add`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.add
+[`*const T::copy_to_nonoverlapping`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.copy_to_nonoverlapping
+[`*const T::copy_to`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.copy_to
+[`*const T::read_unaligned`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read_unaligned
+[`*const T::read_volatile`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read_volatile
+[`*const T::read`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read
+[`*const T::sub`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.sub
+[`*const T::wrapping_add`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_add
+[`*const T::wrapping_sub`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_sub
+[`*mut T::add`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.add-1
+[`*mut T::copy_to_nonoverlapping`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.copy_to_nonoverlapping-1
+[`*mut T::copy_to`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.copy_to-1
+[`*mut T::read_unaligned`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read_unaligned-1
+[`*mut T::read_volatile`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read_volatile-1
+[`*mut T::read`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.read-1
+[`*mut T::replace`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.replace
+[`*mut T::sub`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.sub-1
+[`*mut T::swap`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.swap
+[`*mut T::wrapping_add`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_add-1
+[`*mut T::wrapping_sub`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.wrapping_sub-1
+[`*mut T::write_bytes`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.write_bytes
+[`*mut T::write_unaligned`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.write_unaligned
+[`*mut T::write_volatile`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.write_volatile
+[`*mut T::write`]: https://doc.rust-lang.org/std/primitive.pointer.html#method.write
+[`Box::leak`]: https://doc.rust-lang.org/std/boxed/struct.Box.html#method.leak
+[`FromUtf8Error::as_bytes`]: https://doc.rust-lang.org/std/string/struct.FromUtf8Error.html#method.as_bytes
+[`LocalKey::try_with`]: https://doc.rust-lang.org/std/thread/struct.LocalKey.html#method.try_with
+[`Option::cloned`]: https://doc.rust-lang.org/std/option/enum.Option.html#method.cloned
+[`btree_map::Entry::and_modify`]: https://doc.rust-lang.org/std/collections/btree_map/enum.Entry.html#method.and_modify
+[`fs::read_to_string`]: https://doc.rust-lang.org/std/fs/fn.read_to_string.html
+[`fs::read`]: https://doc.rust-lang.org/std/fs/fn.read.html
+[`fs::write`]: https://doc.rust-lang.org/std/fs/fn.write.html
+[`hash_map::Entry::and_modify`]: https://doc.rust-lang.org/std/collections/hash_map/enum.Entry.html#method.and_modify
+[`iter::FusedIterator`]: https://doc.rust-lang.org/std/iter/trait.FusedIterator.html
+[`ops::RangeInclusive`]: https://doc.rust-lang.org/std/ops/struct.RangeInclusive.html
+[`ops::RangeToInclusive`]: https://doc.rust-lang.org/std/ops/struct.RangeToInclusive.html
+[`process::id`]: https://doc.rust-lang.org/std/process/fn.id.html
+[`slice::rotate_left`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate_left
+[`slice::rotate_right`]: https://doc.rust-lang.org/std/primitive.slice.html#method.rotate_right
+[`String::retain`]: https://doc.rust-lang.org/std/string/struct.String.html#method.retain
+[cargo/5041]: https://github.com/rust-lang/cargo/pull/5041
+[cargo/5083]: https://github.com/rust-lang/cargo/pull/5083
+[cargo/5093]: https://github.com/rust-lang/cargo/pull/5093
+
+
 Version 1.25.0 (2018-03-29)
 ==========================
 
diff --git a/src/liballoc/lib.rs b/src/liballoc/lib.rs
index da4b76a4d52..bb78c14b905 100644
--- a/src/liballoc/lib.rs
+++ b/src/liballoc/lib.rs
@@ -125,6 +125,7 @@
 #![feature(inclusive_range_methods)]
 #![cfg_attr(stage0, feature(generic_param_attrs))]
 #![feature(rustc_const_unstable)]
+#![feature(const_vec_new)]
 
 #![cfg_attr(not(test), feature(fn_traits, i128))]
 #![cfg_attr(test, feature(test))]
diff --git a/src/liballoc/raw_vec.rs b/src/liballoc/raw_vec.rs
index eb25ae17511..4d73d3aa07e 100644
--- a/src/liballoc/raw_vec.rs
+++ b/src/liballoc/raw_vec.rs
@@ -748,7 +748,7 @@ mod tests {
 
     #[test]
     fn allocator_param() {
-        use allocator::{Alloc, AllocErr};
+        use alloc::AllocErr;
 
         // Writing a test of integration between third-party
         // allocators and RawVec is a little tricky because the RawVec
diff --git a/src/liballoc/str.rs b/src/liballoc/str.rs
index 0cbe65db53c..9e693c89be9 100644
--- a/src/liballoc/str.rs
+++ b/src/liballoc/str.rs
@@ -207,7 +207,8 @@ impl str {
     /// let s = "this is old";
     /// assert_eq!(s, s.replace("cookie monster", "little lamb"));
     /// ```
-    #[must_use]
+    #[must_use = "this returns the replaced string as a new allocation, \
+                  without modifying the original"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
     pub fn replace<'a, P: Pattern<'a>>(&'a self, from: P, to: &str) -> String {
@@ -247,7 +248,8 @@ impl str {
     /// let s = "this is old";
     /// assert_eq!(s, s.replacen("cookie monster", "little lamb", 10));
     /// ```
-    #[must_use]
+    #[must_use = "this returns the replaced string as a new allocation, \
+                  without modifying the original"]
     #[stable(feature = "str_replacen", since = "1.16.0")]
     pub fn replacen<'a, P: Pattern<'a>>(&'a self, pat: P, to: &str, count: usize) -> String {
         // Hope to reduce the times of re-allocation
diff --git a/src/liballoc/string.rs b/src/liballoc/string.rs
index 2f84d5f7f86..da9afdd2ca3 100644
--- a/src/liballoc/string.rs
+++ b/src/liballoc/string.rs
@@ -380,7 +380,8 @@ impl String {
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn new() -> String {
+    #[rustc_const_unstable(feature = "const_string_new")]
+    pub const fn new() -> String {
         String { vec: Vec::new() }
     }
 
diff --git a/src/libcore/fmt/builders.rs b/src/libcore/fmt/builders.rs
index a1f4c6995da..e8ea2e743da 100644
--- a/src/libcore/fmt/builders.rs
+++ b/src/libcore/fmt/builders.rs
@@ -84,7 +84,7 @@ impl<'a> fmt::Write for PadAdapter<'a> {
 /// // prints "Foo { bar: 10, baz: "Hello World" }"
 /// println!("{:?}", Foo { bar: 10, baz: "Hello World".to_string() });
 /// ```
-#[must_use]
+#[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugStruct<'a, 'b: 'a> {
@@ -181,7 +181,7 @@ impl<'a, 'b: 'a> DebugStruct<'a, 'b> {
 /// // prints "Foo(10, "Hello World")"
 /// println!("{:?}", Foo(10, "Hello World".to_string()));
 /// ```
-#[must_use]
+#[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugTuple<'a, 'b: 'a> {
@@ -319,7 +319,7 @@ impl<'a, 'b: 'a> DebugInner<'a, 'b> {
 /// // prints "{10, 11}"
 /// println!("{:?}", Foo(vec![10, 11]));
 /// ```
-#[must_use]
+#[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugSet<'a, 'b: 'a> {
@@ -390,7 +390,7 @@ impl<'a, 'b: 'a> DebugSet<'a, 'b> {
 /// // prints "[10, 11]"
 /// println!("{:?}", Foo(vec![10, 11]));
 /// ```
-#[must_use]
+#[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugList<'a, 'b: 'a> {
@@ -461,7 +461,7 @@ impl<'a, 'b: 'a> DebugList<'a, 'b> {
 /// // prints "{"A": 10, "B": 11}"
 /// println!("{:?}", Foo(vec![("A".to_string(), 10), ("B".to_string(), 11)]));
 /// ```
-#[must_use]
+#[must_use = "must eventually call `finish()` on Debug builders"]
 #[allow(missing_debug_implementations)]
 #[stable(feature = "debug_builders", since = "1.2.0")]
 pub struct DebugMap<'a, 'b: 'a> {
diff --git a/src/libcore/mem.rs b/src/libcore/mem.rs
index 6cbe26afae9..20445def634 100644
--- a/src/libcore/mem.rs
+++ b/src/libcore/mem.rs
@@ -959,8 +959,9 @@ impl<T> ManuallyDrop<T> {
     /// ManuallyDrop::new(Box::new(()));
     /// ```
     #[stable(feature = "manually_drop", since = "1.20.0")]
+    #[rustc_const_unstable(feature = "const_manually_drop_new")]
     #[inline]
-    pub fn new(value: T) -> ManuallyDrop<T> {
+    pub const fn new(value: T) -> ManuallyDrop<T> {
         ManuallyDrop { value: value }
     }
 
diff --git a/src/libcore/num/f32.rs b/src/libcore/num/f32.rs
index 8d5f6f601da..672119eba7f 100644
--- a/src/libcore/num/f32.rs
+++ b/src/libcore/num/f32.rs
@@ -128,10 +128,18 @@ pub mod consts {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const LOG2_E: f32 = 1.44269504088896340735992468100189214_f32;
 
+    /// log<sub>2</sub>(10)
+    #[unstable(feature = "extra_log_consts", issue = "50540")]
+    pub const LOG2_10: f32 = 3.32192809488736234787031942948939018_f32;
+
     /// log<sub>10</sub>(e)
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const LOG10_E: f32 = 0.434294481903251827651128918916605082_f32;
 
+    /// log<sub>10</sub>(2)
+    #[unstable(feature = "extra_log_consts", issue = "50540")]
+    pub const LOG10_2: f32 = 0.301029995663981195213738894724493027_f32;
+
     /// ln(2)
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const LN_2: f32 = 0.693147180559945309417232121458176568_f32;
diff --git a/src/libcore/num/f64.rs b/src/libcore/num/f64.rs
index 08b869734d4..220b23a1e6a 100644
--- a/src/libcore/num/f64.rs
+++ b/src/libcore/num/f64.rs
@@ -124,10 +124,18 @@ pub mod consts {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const E: f64 = 2.71828182845904523536028747135266250_f64;
 
+    /// log<sub>2</sub>(10)
+    #[unstable(feature = "extra_log_consts", issue = "50540")]
+    pub const LOG2_10: f64 = 3.32192809488736234787031942948939018_f64;
+
     /// log<sub>2</sub>(e)
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const LOG2_E: f64 = 1.44269504088896340735992468100189214_f64;
 
+    /// log<sub>10</sub>(2)
+    #[unstable(feature = "extra_log_consts", issue = "50540")]
+    pub const LOG10_2: f64 = 0.301029995663981195213738894724493027_f64;
+
     /// log<sub>10</sub>(e)
     #[stable(feature = "rust1", since = "1.0.0")]
     pub const LOG10_E: f64 = 0.434294481903251827651128918916605082_f64;
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index c152d4979b9..e0cc669d035 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -251,7 +251,7 @@ use ops;
 /// [`Ok`]: enum.Result.html#variant.Ok
 /// [`Err`]: enum.Result.html#variant.Err
 #[derive(Clone, Copy, PartialEq, PartialOrd, Eq, Ord, Debug, Hash)]
-#[must_use]
+#[must_use = "this `Result` may be an `Err` variant, which should be handled"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub enum Result<T, E> {
     /// Contains the success value
diff --git a/src/libcore/tests/num/flt2dec/random.rs b/src/libcore/tests/num/flt2dec/random.rs
index 315ac4d7d99..a1928657dab 100644
--- a/src/libcore/tests/num/flt2dec/random.rs
+++ b/src/libcore/tests/num/flt2dec/random.rs
@@ -11,7 +11,6 @@
 #![cfg(not(target_arch = "wasm32"))]
 
 use std::i16;
-use std::mem;
 use std::str;
 
 use core::num::flt2dec::MAX_SIG_DIGITS;
@@ -75,8 +74,7 @@ pub fn f32_random_equivalence_test<F, G>(f: F, g: G, k: usize, n: usize)
     let mut rng: XorShiftRng = Rand::rand(&mut rand::thread_rng());
     let f32_range = Range::new(0x0000_0001u32, 0x7f80_0000);
     iterate("f32_random_equivalence_test", k, n, f, g, |_| {
-        let i: u32 = f32_range.ind_sample(&mut rng);
-        let x: f32 = unsafe {mem::transmute(i)};
+        let x = f32::from_bits(f32_range.ind_sample(&mut rng));
         decode_finite(x)
     });
 }
@@ -87,8 +85,7 @@ pub fn f64_random_equivalence_test<F, G>(f: F, g: G, k: usize, n: usize)
     let mut rng: XorShiftRng = Rand::rand(&mut rand::thread_rng());
     let f64_range = Range::new(0x0000_0000_0000_0001u64, 0x7ff0_0000_0000_0000);
     iterate("f64_random_equivalence_test", k, n, f, g, |_| {
-        let i: u64 = f64_range.ind_sample(&mut rng);
-        let x: f64 = unsafe {mem::transmute(i)};
+        let x = f64::from_bits(f64_range.ind_sample(&mut rng));
         decode_finite(x)
     });
 }
@@ -105,7 +102,8 @@ pub fn f32_exhaustive_equivalence_test<F, G>(f: F, g: G, k: usize)
     // iterate from 0x0000_0001 to 0x7f7f_ffff, i.e. all finite ranges
     let (npassed, nignored) = iterate("f32_exhaustive_equivalence_test",
                                       k, 0x7f7f_ffff, f, g, |i: usize| {
-        let x: f32 = unsafe {mem::transmute(i as u32 + 1)};
+
+        let x = f32::from_bits(i as u32 + 1);
         decode_finite(x)
     });
     assert_eq!((npassed, nignored), (2121451881, 17643158));
diff --git a/src/libstd/primitive_docs.rs b/src/libstd/primitive_docs.rs
index 919d9648297..437d7d74cae 100644
--- a/src/libstd/primitive_docs.rs
+++ b/src/libstd/primitive_docs.rs
@@ -116,6 +116,8 @@ mod prim_bool { }
 ///
 /// # `!` and generics
 ///
+/// ## Infallible errors
+///
 /// The main place you'll see `!` used explicitly is in generic code. Consider the [`FromStr`]
 /// trait:
 ///
@@ -144,9 +146,60 @@ mod prim_bool { }
 /// [`Ok`] variant. This illustrates another behaviour of `!` - it can be used to "delete" certain
 /// enum variants from generic types like `Result`.
 ///
+/// ## Infinite loops
+///
+/// While [`Result<T, !>`] is very useful for removing errors, `!` can also be used to remove
+/// successes as well. If we think of [`Result<T, !>`] as "if this function returns, it has not
+/// errored," we get a very intuitive idea of [`Result<!, E>`] as well: if the function returns, it
+/// *has* errored.
+///
+/// For example, consider the case of a simple web server, which can be simplified to:
+///
+/// ```ignore (hypothetical-example)
+/// loop {
+///     let (client, request) = get_request().expect("disconnected");
+///     let response = request.process();
+///     response.send(client);
+/// }
+/// ```
+///
+/// Currently, this isn't ideal, because we simply panic whenever we fail to get a new connection.
+/// Instead, we'd like to keep track of this error, like this:
+///
+/// ```ignore (hypothetical-example)
+/// loop {
+///     match get_request() {
+///         Err(err) => break err,
+///         Ok((client, request)) => {
+///             let response = request.process();
+///             response.send(client);
+///         },
+///     }
+/// }
+/// ```
+///
+/// Now, when the server disconnects, we exit the loop with an error instead of panicking. While it
+/// might be intuitive to simply return the error, we might want to wrap it in a [`Result<!, E>`]
+/// instead:
+///
+/// ```ignore (hypothetical-example)
+/// fn server_loop() -> Result<!, ConnectionError> {
+///     loop {
+///         let (client, request) = get_request()?;
+///         let response = request.process();
+///         response.send(client);
+///     }
+/// }
+/// ```
+///
+/// Now, we can use `?` instead of `match`, and the return type makes a lot more sense: if the loop
+/// ever stops, it means that an error occurred. We don't even have to wrap the loop in an `Ok`
+/// because `!` coerces to `Result<!, ConnectionError>` automatically.
+///
 /// [`String::from_str`]: str/trait.FromStr.html#tymethod.from_str
 /// [`Result<String, !>`]: result/enum.Result.html
 /// [`Result<T, !>`]: result/enum.Result.html
+/// [`Result<!, E>`]: result/enum.Result.html
 /// [`Ok`]: result/enum.Result.html#variant.Ok
 /// [`String`]: string/struct.String.html
 /// [`Err`]: result/enum.Result.html#variant.Err
diff --git a/src/libstd/sync/mutex.rs b/src/libstd/sync/mutex.rs
index 3b4904c98e8..f3503b0b3a6 100644
--- a/src/libstd/sync/mutex.rs
+++ b/src/libstd/sync/mutex.rs
@@ -150,7 +150,7 @@ unsafe impl<T: ?Sized + Send> Sync for Mutex<T> { }
 /// [`lock`]: struct.Mutex.html#method.lock
 /// [`try_lock`]: struct.Mutex.html#method.try_lock
 /// [`Mutex`]: struct.Mutex.html
-#[must_use]
+#[must_use = "if unused the Mutex will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct MutexGuard<'a, T: ?Sized + 'a> {
     // funny underscores due to how Deref/DerefMut currently work (they
diff --git a/src/libstd/sync/rwlock.rs b/src/libstd/sync/rwlock.rs
index f7fdedc0d21..e3db60cff84 100644
--- a/src/libstd/sync/rwlock.rs
+++ b/src/libstd/sync/rwlock.rs
@@ -94,7 +94,7 @@ unsafe impl<T: ?Sized + Send + Sync> Sync for RwLock<T> {}
 /// [`read`]: struct.RwLock.html#method.read
 /// [`try_read`]: struct.RwLock.html#method.try_read
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockReadGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,
@@ -115,7 +115,7 @@ unsafe impl<'a, T: ?Sized + Sync> Sync for RwLockReadGuard<'a, T> {}
 /// [`write`]: struct.RwLock.html#method.write
 /// [`try_write`]: struct.RwLock.html#method.try_write
 /// [`RwLock`]: struct.RwLock.html
-#[must_use]
+#[must_use = "if unused the RwLock will immediately unlock"]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct RwLockWriteGuard<'a, T: ?Sized + 'a> {
     __lock: &'a RwLock<T>,
diff --git a/src/libstd/sys_common/remutex.rs b/src/libstd/sys_common/remutex.rs
index ce43ec6d9ab..022056f8a8a 100644
--- a/src/libstd/sys_common/remutex.rs
+++ b/src/libstd/sys_common/remutex.rs
@@ -41,7 +41,7 @@ unsafe impl<T: Send> Sync for ReentrantMutex<T> {}
 /// because implementation of the trait would violate Rust’s reference aliasing
 /// rules. Use interior mutability (usually `RefCell`) in order to mutate the
 /// guarded data.
-#[must_use]
+#[must_use = "if unused the ReentrantMutex will immediately unlock"]
 pub struct ReentrantMutexGuard<'a, T: 'a> {
     // funny underscores due to how Deref currently works (it disregards field
     // privacy).
diff --git a/src/libsyntax/parse/mod.rs b/src/libsyntax/parse/mod.rs
index f252020bc31..f26a6a53074 100644
--- a/src/libsyntax/parse/mod.rs
+++ b/src/libsyntax/parse/mod.rs
@@ -419,13 +419,24 @@ pub fn lit_token(lit: token::Lit, suf: Option<Symbol>, diag: Option<(Span, &Hand
         token::Integer(s) => (false, integer_lit(&s.as_str(), suf, diag)),
         token::Float(s) => (false, float_lit(&s.as_str(), suf, diag)),
 
-        token::Str_(s) => {
-            let s = Symbol::intern(&str_lit(&s.as_str(), diag));
-            (true, Some(LitKind::Str(s, ast::StrStyle::Cooked)))
+        token::Str_(mut sym) => {
+            // If there are no characters requiring special treatment we can
+            // reuse the symbol from the Token. Otherwise, we must generate a
+            // new symbol because the string in the LitKind is different to the
+            // string in the Token.
+            let s = &sym.as_str();
+            if s.as_bytes().iter().any(|&c| c == b'\\' || c == b'\r') {
+                sym = Symbol::intern(&str_lit(s, diag));
+            }
+            (true, Some(LitKind::Str(sym, ast::StrStyle::Cooked)))
         }
-        token::StrRaw(s, n) => {
-            let s = Symbol::intern(&raw_str_lit(&s.as_str()));
-            (true, Some(LitKind::Str(s, ast::StrStyle::Raw(n))))
+        token::StrRaw(mut sym, n) => {
+            // Ditto.
+            let s = &sym.as_str();
+            if s.contains('\r') {
+                sym = Symbol::intern(&raw_str_lit(s));
+            }
+            (true, Some(LitKind::Str(sym, ast::StrStyle::Raw(n))))
         }
         token::ByteStr(i) => {
             (true, Some(LitKind::ByteStr(byte_str_lit(&i.as_str()))))
diff --git a/src/stdsimd b/src/stdsimd
index 1ea18a5cb43..2f86c75a247 160000
--- a/src/stdsimd
+++ b/src/stdsimd
@@ -1 +1 @@
-Subproject commit 1ea18a5cb431e24aa838b652ac305acc5e394d6b
+Subproject commit 2f86c75a2479cf051b92fc98273daaf7f151e7a1
diff --git a/src/test/run-pass/vec-const-new.rs b/src/test/run-pass/collections-const-new.rs
similarity index 77%
rename from src/test/run-pass/vec-const-new.rs
rename to src/test/run-pass/collections-const-new.rs
index 62e2a36d7cc..4003c2ec4f7 100644
--- a/src/test/run-pass/vec-const-new.rs
+++ b/src/test/run-pass/collections-const-new.rs
@@ -8,10 +8,15 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
-// Test that Vec::new() can be used for constants
+// Test several functions can be used for constants
+// 1. Vec::new()
+// 2. String::new()
 
 #![feature(const_vec_new)]
+#![feature(const_string_new)]
 
 const MY_VEC: Vec<usize> = Vec::new();
 
+const MY_STRING: String = String::new();
+
 pub fn main() {}
diff --git a/src/test/run-pass/issue-44333.rs b/src/test/run-pass/issue-44333.rs
new file mode 100644
index 00000000000..72731f41321
--- /dev/null
+++ b/src/test/run-pass/issue-44333.rs
@@ -0,0 +1,29 @@
+// Copyright 2018 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+type Func = fn(usize, usize) -> usize;
+
+fn foo(a: usize, b: usize) -> usize { a + b }
+fn bar(a: usize, b: usize) -> usize { a * b }
+fn test(x: usize) -> Func {
+    if x % 2 == 0 { foo }
+    else { bar }
+}
+
+const FOO: Func = foo;
+const BAR: Func = bar;
+
+fn main() {
+    match test(std::env::consts::ARCH.len()) {
+        FOO => println!("foo"),
+        BAR => println!("bar"),
+        _ => unreachable!(),
+    }
+}
diff --git a/src/tools/cargo b/src/tools/cargo
index af3f1cd29bc..9e53ac6e652 160000
--- a/src/tools/cargo
+++ b/src/tools/cargo
@@ -1 +1 @@
-Subproject commit af3f1cd29bc872b932a13083e531255aab233a7e
+Subproject commit 9e53ac6e6525da914cb05a85e5e8eff7b5dca81f
diff --git a/src/tools/rls b/src/tools/rls
index 1263f1ff25b..d2ade31a52a 160000
--- a/src/tools/rls
+++ b/src/tools/rls
@@ -1 +1 @@
-Subproject commit 1263f1ff25bb329b76f74715ad4a7ec0d1f71430
+Subproject commit d2ade31a52a417257742de72c5936a8a342a34b5