Auto merge of #72262 - Dylan-DPC:rollup-x56q1jj, r=Dylan-DPC

Rollup of 7 pull requests

Successful merges:

 - #71625 (Improve the documentation for ManuallyDrop to resolve conflicting usage of terminology)
 - #71919 (Update transitive dependency to work towards removing syn <1.0 dep)
 - #72166 (Simpler slice `Iterator` methods)
 - #72216 (Remove `lang_items\(\).*\.unwrap\(\)`)
 - #72230 (Updated documentation of Prefix::VerbatimDisk)
 - #72234 (Implement Default for proc_macro::TokenStream)
 - #72258 (Fix typo Arbintrary to Arbitrary)

Failed merges:

r? @ghost

16 files changed, 218 insertions, 115 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 490b7fc9857..d6357823a37 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -438,7 +438,7 @@ dependencies = [
  "proc-macro2 1.0.3",
  "quote 1.0.2",
  "syn 1.0.11",
- "synstructure 0.12.1",
+ "synstructure",
 ]
 
 [[package]]
@@ -937,13 +937,13 @@ checksum = "a0afaad2b26fa326569eb264b1363e8ae3357618c43982b3f285f0774ce76b69"
 
 [[package]]
 name = "derive-new"
-version = "0.5.6"
+version = "0.5.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "6ca414e896ae072546f4d789f452daaecf60ddee4c9df5dc6d5936d769e3d87c"
+checksum = "71f31892cd5c62e414316f2963c5689242c43d8e7bbcaaeca97e5e28c95d91d9"
 dependencies = [
- "proc-macro2 0.4.30",
- "quote 0.6.12",
- "syn 0.15.35",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.11",
 ]
 
 [[package]]
@@ -1144,14 +1144,14 @@ dependencies = [
 
 [[package]]
 name = "failure_derive"
-version = "0.1.5"
+version = "0.1.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ea1063915fd7ef4309e222a5a07cf9c319fb9c7836b1f89b85458672dbb127e1"
+checksum = "aa4da3c766cd7a0db8242e326e9e4e081edd567072893ed320008189715366a4"
 dependencies = [
- "proc-macro2 0.4.30",
- "quote 0.6.12",
- "syn 0.15.35",
- "synstructure 0.10.2",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.11",
+ "synstructure",
 ]
 
 [[package]]
@@ -1404,32 +1404,20 @@ dependencies = [
 
 [[package]]
 name = "handlebars"
-version = "2.0.1"
+version = "3.0.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "df044dd42cdb7e32f28557b661406fc0f2494be75199779998810dbc35030e0d"
+checksum = "ba758d094d31274eb49d15da6f326b96bf3185239a6359bf684f3d5321148900"
 dependencies = [
- "hashbrown 0.5.0",
- "lazy_static 1.4.0",
  "log",
  "pest",
  "pest_derive",
  "quick-error",
- "regex",
  "serde",
  "serde_json",
 ]
 
 [[package]]
 name = "hashbrown"
-version = "0.5.0"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e1de41fb8dba9714efd92241565cdff73f78508c95697dd56787d3cba27e2353"
-dependencies = [
- "serde",
-]
-
-[[package]]
-name = "hashbrown"
 version = "0.6.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3cd9867f119b19fecb08cd5c326ad4488d7a1da4bf75b4d95d71db742525aaab"
@@ -2054,9 +2042,9 @@ dependencies = [
 
 [[package]]
 name = "mdbook"
-version = "0.3.5"
+version = "0.3.7"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "031bdd9d4893c983e2f69ebc4b59070feee8276a584c4aabdcb351235ea28016"
+checksum = "e7ec525f7ebccc2dd935c263717250cd37f9a4b264a77c5dbc950ea2734d8159"
 dependencies = [
  "ammonia",
  "chrono",
@@ -2556,15 +2544,15 @@ dependencies = [
 
 [[package]]
 name = "pest_generator"
-version = "2.1.0"
+version = "2.1.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "63120576c4efd69615b5537d3d052257328a4ca82876771d6944424ccfd9f646"
+checksum = "99b8db626e31e5b81787b9783425769681b347011cc59471e33ea46d2ea0cf55"
 dependencies = [
  "pest",
  "pest_meta",
- "proc-macro2 0.4.30",
- "quote 0.6.12",
- "syn 0.15.35",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.11",
 ]
 
 [[package]]
@@ -2784,9 +2772,9 @@ checksum = "6ddd112cca70a4d30883b2d21568a1d376ff8be4758649f64f973c6845128ad3"
 
 [[package]]
 name = "quick-error"
-version = "1.2.2"
+version = "1.2.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9274b940887ce9addde99c4eee6b5c44cc494b182b97e73dc8ffdcb3397fd3f0"
+checksum = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
 
 [[package]]
 name = "quine-mc_cluskey"
@@ -3448,7 +3436,7 @@ dependencies = [
  "proc-macro2 1.0.3",
  "quote 1.0.2",
  "syn 1.0.11",
- "synstructure 0.12.1",
+ "synstructure",
 ]
 
 [[package]]
@@ -4058,7 +4046,7 @@ dependencies = [
  "proc-macro2 1.0.3",
  "quote 1.0.2",
  "syn 1.0.11",
- "synstructure 0.12.1",
+ "synstructure",
 ]
 
 [[package]]
@@ -4629,13 +4617,13 @@ dependencies = [
 
 [[package]]
 name = "serde_derive"
-version = "1.0.81"
+version = "1.0.106"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "477b13b646f5b5b56fc95bedfc3b550d12141ce84f466f6c44b9a17589923885"
+checksum = "9e549e3abf4fb8621bd1609f11dfc9f5e50320802273b12f3811a67e6716ea6c"
 dependencies = [
- "proc-macro2 0.4.30",
- "quote 0.6.12",
- "syn 0.15.35",
+ "proc-macro2 1.0.3",
+ "quote 1.0.2",
+ "syn 1.0.11",
 ]
 
 [[package]]
@@ -4799,7 +4787,7 @@ dependencies = [
  "core",
  "dlmalloc",
  "fortanix-sgx-abi",
- "hashbrown 0.6.2",
+ "hashbrown",
  "hermit-abi",
  "libc",
  "panic_abort",
@@ -4933,18 +4921,6 @@ dependencies = [
 
 [[package]]
 name = "synstructure"
-version = "0.10.2"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "02353edf96d6e4dc81aea2d8490a7e9db177bf8acb0e951c24940bf866cb313f"
-dependencies = [
- "proc-macro2 0.4.30",
- "quote 0.6.12",
- "syn 0.15.35",
- "unicode-xid 0.1.0",
-]
-
-[[package]]
-name = "synstructure"
 version = "0.12.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "3f085a5855930c0441ca1288cf044ea4aecf4f43a91668abdb870b4ba546a203"
diff --git a/src/libcore/iter/traits/iterator.rs b/src/libcore/iter/traits/iterator.rs
index 34ca79154b6..447db405c02 100644
--- a/src/libcore/iter/traits/iterator.rs
+++ b/src/libcore/iter/traits/iterator.rs
@@ -333,7 +333,7 @@ pub trait Iterator {
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn nth(&mut self, mut n: usize) -> Option<Self::Item> {
-        for x in self {
+        while let Some(x) = self.next() {
             if n == 0 {
                 return Some(x);
             }
diff --git a/src/libcore/mem/manually_drop.rs b/src/libcore/mem/manually_drop.rs
index 9e5c2b10d0d..17863dd38af 100644
--- a/src/libcore/mem/manually_drop.rs
+++ b/src/libcore/mem/manually_drop.rs
@@ -7,14 +7,14 @@ use crate::ptr;
 ///
 /// `ManuallyDrop<T>` is subject to the same layout optimizations as `T`.
 /// As a consequence, it has *no effect* on the assumptions that the compiler makes
-/// about all values being initialized at their type.  In particular, initializing
-/// a `ManuallyDrop<&mut T>` with [`mem::zeroed`] is undefined behavior.
+/// about its contents. For example, initializing a `ManuallyDrop<&mut T>`
+/// with [`mem::zeroed`] is undefined behavior.
 /// If you need to handle uninitialized data, use [`MaybeUninit<T>`] instead.
 ///
 /// # Examples
 ///
-/// This wrapper helps with explicitly documenting the drop order dependencies between fields of
-/// the type:
+/// This wrapper can be used to enforce a particular drop order on fields, regardless
+/// of how they are defined in the struct:
 ///
 /// ```rust
 /// use std::mem::ManuallyDrop;
@@ -43,8 +43,18 @@ use crate::ptr;
 /// }
 /// ```
 ///
+/// However, care should be taken when using this pattern as it can lead to *leak amplification*.
+/// In this example, if the `Drop` implementation for `Peach` were to panic, the `banana` field
+/// would also be leaked.
+///
+/// In contrast, the automatically-generated compiler drop implementation would have ensured
+/// that all fields are dropped even in the presence of panics. This is especially important when
+/// working with [pinned] data, where reusing the memory without calling the destructor could lead
+/// to Undefined Behaviour.
+///
 /// [`mem::zeroed`]: fn.zeroed.html
 /// [`MaybeUninit<T>`]: union.MaybeUninit.html
+/// [pinned]: ../pin/index.html
 #[stable(feature = "manually_drop", since = "1.20.0")]
 #[lang = "manually_drop"]
 #[derive(Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash)]
@@ -113,19 +123,28 @@ impl<T> ManuallyDrop<T> {
 }
 
 impl<T: ?Sized> ManuallyDrop<T> {
-    /// Manually drops the contained value.
+    /// Manually drops the contained value. This is exactly equivalent to calling
+    /// [`ptr::drop_in_place`] with a pointer to the contained value. As such, unless
+    /// the contained value is a packed struct, the destructor will be called in-place
+    /// without moving the value, and thus can be used to safely drop [pinned] data.
     ///
     /// If you have ownership of the value, you can use [`ManuallyDrop::into_inner`] instead.
     ///
     /// # Safety
     ///
-    /// This function runs the destructor of the contained value and thus the wrapped value
-    /// now represents uninitialized data. It is up to the user of this method to ensure the
-    /// uninitialized data is not actually used.
-    /// In particular, this function can only be called at most once
-    /// for a given instance of `ManuallyDrop<T>`.
+    /// This function runs the destructor of the contained value. Other than changes made by
+    /// the destructor itself, the memory is left unchanged, and so as far as the compiler is
+    /// concerned still holds a bit-pattern which is valid for the type `T`.
+    ///
+    /// However, this "zombie" value should not be exposed to safe code, and this function
+    /// should not be called more than once. To use a value after it's been dropped, or drop
+    /// a value multiple times, can cause Undefined Behavior (depending on what `drop` does).
+    /// This is normally prevented by the type system, but users of `ManuallyDrop` must
+    /// uphold those guarantees without assistance from the compiler.
     ///
     /// [`ManuallyDrop::into_inner`]: #method.into_inner
+    /// [`ptr::drop_in_place`]: ../ptr/fn.drop_in_place.html
+    /// [pinned]: ../pin/index.html
     #[stable(feature = "manually_drop", since = "1.20.0")]
     #[inline]
     pub unsafe fn drop(slot: &mut ManuallyDrop<T>) {
diff --git a/src/libcore/ptr/mod.rs b/src/libcore/ptr/mod.rs
index 58f779106f7..ecc70adda41 100644
--- a/src/libcore/ptr/mod.rs
+++ b/src/libcore/ptr/mod.rs
@@ -110,11 +110,17 @@ mod mut_ptr;
 ///   as the compiler doesn't need to prove that it's sound to elide the
 ///   copy.
 ///
+/// * It can be used to drop [pinned] data when `T` is not `repr(packed)`
+///   (pinned data must not be moved before it is dropped).
+///
 /// Unaligned values cannot be dropped in place, they must be copied to an aligned
-/// location first using [`ptr::read_unaligned`].
+/// location first using [`ptr::read_unaligned`]. For packed structs, this move is
+/// done automatically by the compiler. This means the fields of packed structs
+/// are not dropped in-place.
 ///
 /// [`ptr::read`]: ../ptr/fn.read.html
 /// [`ptr::read_unaligned`]: ../ptr/fn.read_unaligned.html
+/// [pinned]: ../pin/index.html
 ///
 /// # Safety
 ///
diff --git a/src/libcore/slice/mod.rs b/src/libcore/slice/mod.rs
index f74c6862006..3386f83ec81 100644
--- a/src/libcore/slice/mod.rs
+++ b/src/libcore/slice/mod.rs
@@ -3179,6 +3179,7 @@ macro_rules! is_empty {
         $self.ptr.as_ptr() as *const T == $self.end
     };
 }
+
 // To get rid of some bounds checks (see `position`), we compute the length in a somewhat
 // unexpected way. (Tested by `codegen/slice-position-bounds-check`.)
 macro_rules! len {
@@ -3347,40 +3348,127 @@ macro_rules! iterator {
                 self.next_back()
             }
 
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile.
+            #[inline]
+            fn for_each<F>(mut self, mut f: F)
+            where
+                Self: Sized,
+                F: FnMut(Self::Item),
+            {
+                while let Some(x) = self.next() {
+                    f(x);
+                }
+            }
+
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile.
+            #[inline]
+            fn all<F>(&mut self, mut f: F) -> bool
+            where
+                Self: Sized,
+                F: FnMut(Self::Item) -> bool,
+            {
+                while let Some(x) = self.next() {
+                    if !f(x) {
+                        return false;
+                    }
+                }
+                true
+            }
+
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile.
+            #[inline]
+            fn any<F>(&mut self, mut f: F) -> bool
+            where
+                Self: Sized,
+                F: FnMut(Self::Item) -> bool,
+            {
+                while let Some(x) = self.next() {
+                    if f(x) {
+                        return true;
+                    }
+                }
+                false
+            }
+
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile.
+            #[inline]
+            fn find<P>(&mut self, mut predicate: P) -> Option<Self::Item>
+            where
+                Self: Sized,
+                P: FnMut(&Self::Item) -> bool,
+            {
+                while let Some(x) = self.next() {
+                    if predicate(&x) {
+                        return Some(x);
+                    }
+                }
+                None
+            }
+
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile.
+            #[inline]
+            fn find_map<B, F>(&mut self, mut f: F) -> Option<B>
+            where
+                Self: Sized,
+                F: FnMut(Self::Item) -> Option<B>,
+            {
+                while let Some(x) = self.next() {
+                    if let Some(y) = f(x) {
+                        return Some(y);
+                    }
+                }
+                None
+            }
+
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile. Also, the `assume` avoids a bounds check.
             #[inline]
             #[rustc_inherit_overflow_checks]
             fn position<P>(&mut self, mut predicate: P) -> Option<usize> where
                 Self: Sized,
                 P: FnMut(Self::Item) -> bool,
             {
-                // The addition might panic on overflow.
                 let n = len!(self);
-                self.try_fold(0, move |i, x| {
-                    if predicate(x) { Err(i) }
-                    else { Ok(i + 1) }
-                }).err()
-                    .map(|i| {
+                let mut i = 0;
+                while let Some(x) = self.next() {
+                    if predicate(x) {
                         unsafe { assume(i < n) };
-                        i
-                    })
+                        return Some(i);
+                    }
+                    i += 1;
+                }
+                None
             }
 
+            // We override the default implementation, which uses `try_fold`,
+            // because this simple implementation generates less LLVM IR and is
+            // faster to compile. Also, the `assume` avoids a bounds check.
             #[inline]
             fn rposition<P>(&mut self, mut predicate: P) -> Option<usize> where
                 P: FnMut(Self::Item) -> bool,
                 Self: Sized + ExactSizeIterator + DoubleEndedIterator
             {
-                // No need for an overflow check here, because `ExactSizeIterator`
                 let n = len!(self);
-                self.try_rfold(n, move |i, x| {
-                    let i = i - 1;
-                    if predicate(x) { Err(i) }
-                    else { Ok(i) }
-                }).err()
-                    .map(|i| {
+                let mut i = n;
+                while let Some(x) = self.next_back() {
+                    i -= 1;
+                    if predicate(x) {
                         unsafe { assume(i < n) };
-                        i
-                    })
+                        return Some(i);
+                    }
+                }
+                None
             }
 
             $($extra)*
diff --git a/src/libproc_macro/lib.rs b/src/libproc_macro/lib.rs
index 31bc61263ab..b6544341fa9 100644
--- a/src/libproc_macro/lib.rs
+++ b/src/libproc_macro/lib.rs
@@ -158,6 +158,13 @@ impl fmt::Debug for TokenStream {
     }
 }
 
+#[stable(feature = "proc_macro_token_stream_default", since = "1.45.0")]
+impl Default for TokenStream {
+    fn default() -> Self {
+        TokenStream::new()
+    }
+}
+
 #[unstable(feature = "proc_macro_quote", issue = "54722")]
 pub use quote::{quote, quote_span};
 
diff --git a/src/librustc_error_codes/error_codes/E0307.md b/src/librustc_error_codes/error_codes/E0307.md
index 52707b93acc..0d29d56ea1a 100644
--- a/src/librustc_error_codes/error_codes/E0307.md
+++ b/src/librustc_error_codes/error_codes/E0307.md
@@ -64,7 +64,7 @@ impl Trait for Foo {
 }
 ```
 
-The nightly feature [Arbintrary self types][AST] extends the accepted
+The nightly feature [Arbitrary self types][AST] extends the accepted
 set of receiver types to also include any type that can dereference to
 `Self`:
 
diff --git a/src/librustc_mir/monomorphize/mod.rs b/src/librustc_mir/monomorphize/mod.rs
index 98a3d9584f5..28edd87a3ad 100644
--- a/src/librustc_mir/monomorphize/mod.rs
+++ b/src/librustc_mir/monomorphize/mod.rs
@@ -2,6 +2,8 @@ use rustc_middle::traits;
 use rustc_middle::ty::adjustment::CustomCoerceUnsized;
 use rustc_middle::ty::{self, Ty, TyCtxt};
 
+use rustc_hir::lang_items::CoerceUnsizedTraitLangItem;
+
 pub mod collector;
 pub mod partitioning;
 
@@ -10,7 +12,7 @@ pub fn custom_coerce_unsize_info<'tcx>(
     source_ty: Ty<'tcx>,
     target_ty: Ty<'tcx>,
 ) -> CustomCoerceUnsized {
-    let def_id = tcx.lang_items().coerce_unsized_trait().unwrap();
+    let def_id = tcx.require_lang_item(CoerceUnsizedTraitLangItem, None);
 
     let trait_ref = ty::Binder::bind(ty::TraitRef {
         def_id,
diff --git a/src/librustc_mir_build/hair/pattern/const_to_pat.rs b/src/librustc_mir_build/hair/pattern/const_to_pat.rs
index d3129751586..28ec2ca13d5 100644
--- a/src/librustc_mir_build/hair/pattern/const_to_pat.rs
+++ b/src/librustc_mir_build/hair/pattern/const_to_pat.rs
@@ -141,7 +141,8 @@ impl<'a, 'tcx> ConstToPat<'a, 'tcx> {
                 // code at the moment, because types like `for <'a> fn(&'a ())` do
                 // not *yet* implement `PartialEq`. So for now we leave this here.
                 let ty_is_partial_eq: bool = {
-                    let partial_eq_trait_id = self.tcx().require_lang_item(EqTraitLangItem, None);
+                    let partial_eq_trait_id =
+                        self.tcx().require_lang_item(EqTraitLangItem, Some(self.span));
                     let obligation: PredicateObligation<'_> = predicate_for_trait_def(
                         self.tcx(),
                         self.param_env,
diff --git a/src/librustc_trait_selection/traits/structural_match.rs b/src/librustc_trait_selection/traits/structural_match.rs
index 8007290f35d..eb63505b69b 100644
--- a/src/librustc_trait_selection/traits/structural_match.rs
+++ b/src/librustc_trait_selection/traits/structural_match.rs
@@ -4,6 +4,7 @@ use crate::traits::{self, ConstPatternStructural, TraitEngine};
 
 use rustc_data_structures::fx::FxHashSet;
 use rustc_hir as hir;
+use rustc_hir::lang_items::{StructuralPeqTraitLangItem, StructuralTeqTraitLangItem};
 use rustc_middle::ty::{self, AdtDef, Ty, TyCtxt, TypeFoldable, TypeVisitor};
 use rustc_span::Span;
 
@@ -69,7 +70,7 @@ pub fn type_marked_structural(
     let mut fulfillment_cx = traits::FulfillmentContext::new();
     let cause = ObligationCause::new(span, id, ConstPatternStructural);
     // require `#[derive(PartialEq)]`
-    let structural_peq_def_id = infcx.tcx.lang_items().structural_peq_trait().unwrap();
+    let structural_peq_def_id = infcx.tcx.require_lang_item(StructuralPeqTraitLangItem, Some(span));
     fulfillment_cx.register_bound(
         infcx,
         ty::ParamEnv::empty(),
@@ -80,7 +81,7 @@ pub fn type_marked_structural(
     // for now, require `#[derive(Eq)]`. (Doing so is a hack to work around
     // the type `for<'a> fn(&'a ())` failing to implement `Eq` itself.)
     let cause = ObligationCause::new(span, id, ConstPatternStructural);
-    let structural_teq_def_id = infcx.tcx.lang_items().structural_teq_trait().unwrap();
+    let structural_teq_def_id = infcx.tcx.require_lang_item(StructuralTeqTraitLangItem, Some(span));
     fulfillment_cx.register_bound(
         infcx,
         ty::ParamEnv::empty(),
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index 035e5880dc5..87a6f119acb 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -6,7 +6,7 @@ use crate::astconv::AstConv;
 use crate::middle::region;
 use rustc_hir as hir;
 use rustc_hir::def_id::DefId;
-use rustc_hir::lang_items;
+use rustc_hir::lang_items::{FutureTraitLangItem, GeneratorTraitLangItem};
 use rustc_infer::infer::type_variable::{TypeVariableOrigin, TypeVariableOriginKind};
 use rustc_infer::infer::LateBoundRegionConversionTime;
 use rustc_infer::infer::{InferOk, InferResult};
@@ -245,7 +245,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         let trait_ref = projection.to_poly_trait_ref(tcx);
 
         let is_fn = tcx.fn_trait_kind_from_lang_item(trait_ref.def_id()).is_some();
-        let gen_trait = tcx.require_lang_item(lang_items::GeneratorTraitLangItem, cause_span);
+        let gen_trait = tcx.require_lang_item(GeneratorTraitLangItem, cause_span);
         let is_gen = gen_trait == trait_ref.def_id();
         if !is_fn && !is_gen {
             debug!("deduce_sig_from_projection: not fn or generator");
@@ -678,7 +678,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // Check that this is a projection from the `Future` trait.
         let trait_ref = predicate.projection_ty.trait_ref(self.tcx);
-        let future_trait = self.tcx.lang_items().future_trait().unwrap();
+        let future_trait = self.tcx.require_lang_item(FutureTraitLangItem, Some(cause_span));
         if trait_ref.def_id != future_trait {
             debug!("deduce_future_output_from_projection: not a future");
             return None;
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs
index 64de94ea58c..9694ce9450c 100644
--- a/src/librustc_typeck/check/demand.rs
+++ b/src/librustc_typeck/check/demand.rs
@@ -7,7 +7,7 @@ use rustc_trait_selection::traits::{self, ObligationCause};
 use rustc_ast::util::parser::PREC_POSTFIX;
 use rustc_errors::{Applicability, DiagnosticBuilder};
 use rustc_hir as hir;
-use rustc_hir::lang_items::DerefTraitLangItem;
+use rustc_hir::lang_items::{CloneTraitLangItem, DerefTraitLangItem};
 use rustc_hir::{is_range_literal, Node};
 use rustc_middle::ty::adjustment::AllowTwoPhase;
 use rustc_middle::ty::{self, AssocItem, Ty, TypeAndMut};
@@ -456,8 +456,8 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 };
                 if self.can_coerce(ref_ty, expected) {
                     let mut sugg_sp = sp;
-                    if let hir::ExprKind::MethodCall(segment, _sp, args) = &expr.kind {
-                        let clone_trait = self.tcx.lang_items().clone_trait().unwrap();
+                    if let hir::ExprKind::MethodCall(ref segment, sp, ref args) = expr.kind {
+                        let clone_trait = self.tcx.require_lang_item(CloneTraitLangItem, Some(sp));
                         if let ([arg], Some(true), sym::clone) = (
                             &args[..],
                             self.tables.borrow().type_dependent_def_id(expr.hir_id).map(|did| {
@@ -635,7 +635,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ if sp == expr.span && !is_macro => {
                 // Check for `Deref` implementations by constructing a predicate to
                 // prove: `<T as Deref>::Output == U`
-                let deref_trait = self.tcx.require_lang_item(DerefTraitLangItem, Some(expr.span));
+                let deref_trait = self.tcx.require_lang_item(DerefTraitLangItem, Some(sp));
                 let item_def_id = self
                     .tcx
                     .associated_items(deref_trait)
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 226c187e3cf..6bf836015d2 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -100,7 +100,9 @@ use rustc_hir::def::{CtorOf, DefKind, Res};
 use rustc_hir::def_id::{CrateNum, DefId, DefIdMap, DefIdSet, LocalDefId, LOCAL_CRATE};
 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
 use rustc_hir::itemlikevisit::ItemLikeVisitor;
-use rustc_hir::lang_items;
+use rustc_hir::lang_items::{
+    FutureTraitLangItem, PinTypeLangItem, SizedTraitLangItem, VaListTypeLangItem,
+};
 use rustc_hir::{ExprKind, GenericArg, HirIdMap, Item, ItemKind, Node, PatKind, QPath};
 use rustc_index::bit_set::BitSet;
 use rustc_index::vec::Idx;
@@ -1335,10 +1337,8 @@ fn check_fn<'a, 'tcx>(
     // C-variadic fns also have a `VaList` input that's not listed in `fn_sig`
     // (as it's created inside the body itself, not passed in from outside).
     let maybe_va_list = if fn_sig.c_variadic {
-        let va_list_did = tcx.require_lang_item(
-            lang_items::VaListTypeLangItem,
-            Some(body.params.last().unwrap().span),
-        );
+        let va_list_did =
+            tcx.require_lang_item(VaListTypeLangItem, Some(body.params.last().unwrap().span));
         let region = tcx.mk_region(ty::ReScope(region::Scope {
             id: body.value.hir_id.local_id,
             data: region::ScopeData::CallSite,
@@ -3296,7 +3296,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         code: traits::ObligationCauseCode<'tcx>,
     ) {
         if !ty.references_error() {
-            let lang_item = self.tcx.require_lang_item(lang_items::SizedTraitLangItem, None);
+            let lang_item = self.tcx.require_lang_item(SizedTraitLangItem, None);
             self.require_type_meets(ty, span, code, lang_item);
         }
     }
@@ -5135,7 +5135,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
             _ => {}
         }
         let boxed_found = self.tcx.mk_box(found);
-        let new_found = self.tcx.mk_lang_item(boxed_found, lang_items::PinTypeLangItem).unwrap();
+        let new_found = self.tcx.mk_lang_item(boxed_found, PinTypeLangItem).unwrap();
         if let (true, Ok(snippet)) = (
             self.can_coerce(new_found, expected),
             self.sess().source_map().span_to_snippet(expr.span),
@@ -5292,7 +5292,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let sp = expr.span;
                 // Check for `Future` implementations by constructing a predicate to
                 // prove: `<T as Future>::Output == U`
-                let future_trait = self.tcx.lang_items().future_trait().unwrap();
+                let future_trait = self.tcx.require_lang_item(FutureTraitLangItem, Some(sp));
                 let item_def_id = self
                     .tcx
                     .associated_items(future_trait)
diff --git a/src/librustc_typeck/coherence/builtin.rs b/src/librustc_typeck/coherence/builtin.rs
index c01c4d90c8e..efa3cd9955b 100644
--- a/src/librustc_typeck/coherence/builtin.rs
+++ b/src/librustc_typeck/coherence/builtin.rs
@@ -4,7 +4,9 @@
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def_id::{DefId, LocalDefId};
-use rustc_hir::lang_items::UnsizeTraitLangItem;
+use rustc_hir::lang_items::{
+    CoerceUnsizedTraitLangItem, DispatchFromDynTraitLangItem, UnsizeTraitLangItem,
+};
 use rustc_hir::ItemKind;
 use rustc_infer::infer;
 use rustc_infer::infer::outlives::env::OutlivesEnvironment;
@@ -145,11 +147,11 @@ fn visit_implementation_of_coerce_unsized(tcx: TyCtxt<'tcx>, impl_did: LocalDefI
 fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDefId) {
     debug!("visit_implementation_of_dispatch_from_dyn: impl_did={:?}", impl_did);
 
-    let dispatch_from_dyn_trait = tcx.lang_items().dispatch_from_dyn_trait().unwrap();
-
     let impl_hir_id = tcx.hir().as_local_hir_id(impl_did);
     let span = tcx.hir().span(impl_hir_id);
 
+    let dispatch_from_dyn_trait = tcx.require_lang_item(DispatchFromDynTraitLangItem, Some(span));
+
     let source = tcx.type_of(impl_did);
     assert!(!source.has_escaping_bound_vars());
     let target = {
@@ -314,22 +316,23 @@ fn visit_implementation_of_dispatch_from_dyn(tcx: TyCtxt<'_>, impl_did: LocalDef
 
 pub fn coerce_unsized_info(tcx: TyCtxt<'tcx>, impl_did: DefId) -> CoerceUnsizedInfo {
     debug!("compute_coerce_unsized_info(impl_did={:?})", impl_did);
-    let coerce_unsized_trait = tcx.lang_items().coerce_unsized_trait().unwrap();
+
+    // this provider should only get invoked for local def-ids
+    let impl_hir_id = tcx.hir().as_local_hir_id(impl_did.expect_local());
+    let span = tcx.hir().span(impl_hir_id);
+
+    let coerce_unsized_trait = tcx.require_lang_item(CoerceUnsizedTraitLangItem, Some(span));
 
     let unsize_trait = tcx.lang_items().require(UnsizeTraitLangItem).unwrap_or_else(|err| {
         tcx.sess.fatal(&format!("`CoerceUnsized` implementation {}", err));
     });
 
-    // this provider should only get invoked for local def-ids
-    let impl_hir_id = tcx.hir().as_local_hir_id(impl_did.expect_local());
-
     let source = tcx.type_of(impl_did);
     let trait_ref = tcx.impl_trait_ref(impl_did).unwrap();
     assert_eq!(trait_ref.def_id, coerce_unsized_trait);
     let target = trait_ref.substs.type_at(1);
     debug!("visit_implementation_of_coerce_unsized: {:?} -> {:?} (bound)", source, target);
 
-    let span = tcx.hir().span(impl_hir_id);
     let param_env = tcx.param_env(impl_did);
     assert!(!source.has_escaping_bound_vars());
 
diff --git a/src/libstd/path.rs b/src/libstd/path.rs
index 173d6d1cfa7..8516e80f3b8 100644
--- a/src/libstd/path.rs
+++ b/src/libstd/path.rs
@@ -157,10 +157,10 @@ pub enum Prefix<'a> {
         #[stable(feature = "rust1", since = "1.0.0")] &'a OsStr,
     ),
 
-    /// Verbatim disk prefix, e.g., `\\?\C:\`.
+    /// Verbatim disk prefix, e.g., `\\?\C:`.
     ///
     /// Verbatim disk prefixes consist of `\\?\` immediately followed by the
-    /// drive letter and `:\`.
+    /// drive letter and `:`.
     #[stable(feature = "rust1", since = "1.0.0")]
     VerbatimDisk(#[stable(feature = "rust1", since = "1.0.0")] u8),
 
diff --git a/src/tools/rustbook/Cargo.toml b/src/tools/rustbook/Cargo.toml
index e6e758dccdf..ff41197faa1 100644
--- a/src/tools/rustbook/Cargo.toml
+++ b/src/tools/rustbook/Cargo.toml
@@ -23,6 +23,6 @@ codespan-reporting = { version = "0.5", optional = true }
 rustc-workspace-hack = "1.0.0"
 
 [dependencies.mdbook]
-version = "0.3.0"
+version = "0.3.7"
 default-features = false
 features = ["search"]