diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 0db4fb3890100..3d5ae7f7faba8 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -103,7 +103,6 @@
 //! More documentation can be found in each respective module below, and you can
 //! also check out the `src/bootstrap/README.md` file for more information.
 
-#![feature(core_intrinsics)]
 #![feature(drain_filter)]
 
 use std::cell::{Cell, RefCell};
diff --git a/src/libcore/cmp.rs b/src/libcore/cmp.rs
index e41a7afd3e223..604be7d5f68d0 100644
--- a/src/libcore/cmp.rs
+++ b/src/libcore/cmp.rs
@@ -361,6 +361,7 @@ impl Ordering {
     /// assert!(data == b);
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn reverse(self) -> Ordering {
         match self {
@@ -398,6 +399,7 @@ impl Ordering {
     /// assert_eq!(result, Ordering::Less);
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "ordering_chaining", since = "1.17.0")]
     pub fn then(self, other: Ordering) -> Ordering {
         match self {
@@ -435,6 +437,7 @@ impl Ordering {
     /// assert_eq!(result, Ordering::Less);
     /// ```
     #[inline]
+    #[must_use]
     #[stable(feature = "ordering_chaining", since = "1.17.0")]
     pub fn then_with<F: FnOnce() -> Ordering>(self, f: F) -> Ordering {
         match self {
@@ -576,6 +579,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// assert_eq!(10.cmp(&5), Ordering::Greater);
     /// assert_eq!(5.cmp(&5), Ordering::Equal);
     /// ```
+    #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     fn cmp(&self, other: &Self) -> Ordering;
 
@@ -591,6 +595,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// ```
     #[stable(feature = "ord_max_min", since = "1.21.0")]
     #[inline]
+    #[must_use]
     fn max(self, other: Self) -> Self
     where
         Self: Sized,
@@ -610,6 +615,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// ```
     #[stable(feature = "ord_max_min", since = "1.21.0")]
     #[inline]
+    #[must_use]
     fn min(self, other: Self) -> Self
     where
         Self: Sized,
@@ -635,6 +641,7 @@ pub trait Ord: Eq + PartialOrd<Self> {
     /// assert!(0.clamp(-2, 1) == 0);
     /// assert!(2.clamp(-2, 1) == 1);
     /// ```
+    #[must_use]
     #[unstable(feature = "clamp", issue = "44095")]
     fn clamp(self, min: Self, max: Self) -> Self
     where
@@ -915,6 +922,7 @@ pub macro PartialOrd($item:item) {
 /// assert_eq!(2, cmp::min(2, 2));
 /// ```
 #[inline]
+#[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn min<T: Ord>(v1: T, v2: T) -> T {
     v1.min(v2)
@@ -935,6 +943,7 @@ pub fn min<T: Ord>(v1: T, v2: T) -> T {
 /// assert_eq!(cmp::min_by(-2, 2, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), -2);
 /// ```
 #[inline]
+#[must_use]
 #[unstable(feature = "cmp_min_max_by", issue = "64460")]
 pub fn min_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
     match compare(&v1, &v2) {
@@ -958,6 +967,7 @@ pub fn min_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
 /// assert_eq!(cmp::min_by_key(-2, 2, |x: &i32| x.abs()), -2);
 /// ```
 #[inline]
+#[must_use]
 #[unstable(feature = "cmp_min_max_by", issue = "64460")]
 pub fn min_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
     min_by(v1, v2, |v1, v2| f(v1).cmp(&f(v2)))
@@ -978,6 +988,7 @@ pub fn min_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
 /// assert_eq!(2, cmp::max(2, 2));
 /// ```
 #[inline]
+#[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub fn max<T: Ord>(v1: T, v2: T) -> T {
     v1.max(v2)
@@ -998,6 +1009,7 @@ pub fn max<T: Ord>(v1: T, v2: T) -> T {
 /// assert_eq!(cmp::max_by(-2, 2, |x: &i32, y: &i32| x.abs().cmp(&y.abs())), 2);
 /// ```
 #[inline]
+#[must_use]
 #[unstable(feature = "cmp_min_max_by", issue = "64460")]
 pub fn max_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
     match compare(&v1, &v2) {
@@ -1021,6 +1033,7 @@ pub fn max_by<T, F: FnOnce(&T, &T) -> Ordering>(v1: T, v2: T, compare: F) -> T {
 /// assert_eq!(cmp::max_by_key(-2, 2, |x: &i32| x.abs()), 2);
 /// ```
 #[inline]
+#[must_use]
 #[unstable(feature = "cmp_min_max_by", issue = "64460")]
 pub fn max_by_key<T, F: FnMut(&T) -> K, K: Ord>(v1: T, v2: T, mut f: F) -> T {
     max_by(v1, v2, |v1, v2| f(v1).cmp(&f(v2)))
diff --git a/src/libcore/option.rs b/src/libcore/option.rs
index e35c91206b8d4..9b32442371c37 100644
--- a/src/libcore/option.rs
+++ b/src/libcore/option.rs
@@ -317,7 +317,7 @@ impl<T> Option<T> {
     // Getting to contained values
     /////////////////////////////////////////////////////////////////////////
 
-    /// Unwraps an option, yielding the content of a [`Some`].
+    /// Returns the contained [`Some`] value, consuming the `self` value.
     ///
     /// # Panics
     ///
@@ -348,17 +348,22 @@ impl<T> Option<T> {
         }
     }
 
-    /// Moves the value `v` out of the `Option<T>` if it is [`Some(v)`].
+    /// Returns the contained [`Some`] value, consuming the `self` value.
     ///
-    /// In general, because this function may panic, its use is discouraged.
+    /// Because this function may panic, its use is generally discouraged.
     /// Instead, prefer to use pattern matching and handle the [`None`]
-    /// case explicitly.
+    /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
+    /// [`unwrap_or_default`].
+    ///
+    /// [`unwrap_or`]: #method.unwrap_or
+    /// [`unwrap_or_else`]: #method.unwrap_or_else
+    /// [`unwrap_or_default`]: #method.unwrap_or_default
     ///
     /// # Panics
     ///
     /// Panics if the self value equals [`None`].
     ///
-    /// [`Some(v)`]: #variant.Some
+    /// [`Some`]: #variant.Some
     /// [`None`]: #variant.None
     ///
     /// # Examples
@@ -382,12 +387,13 @@ impl<T> Option<T> {
         }
     }
 
-    /// Returns the contained value or a default.
+    /// Returns the contained [`Some`] value or a provided default.
     ///
     /// Arguments passed to `unwrap_or` are eagerly evaluated; if you are passing
     /// the result of a function call, it is recommended to use [`unwrap_or_else`],
     /// which is lazily evaluated.
     ///
+    /// [`Some`]: #variant.Some
     /// [`unwrap_or_else`]: #method.unwrap_or_else
     ///
     /// # Examples
@@ -405,7 +411,7 @@ impl<T> Option<T> {
         }
     }
 
-    /// Returns the contained value or computes it from a closure.
+    /// Returns the contained [`Some`] value or computes it from a closure.
     ///
     /// # Examples
     ///
@@ -986,7 +992,7 @@ impl<T: Clone> Option<&mut T> {
 }
 
 impl<T: fmt::Debug> Option<T> {
-    /// Unwraps an option, expecting [`None`] and returning nothing.
+    /// Consumes `self` while expecting [`None`] and returning nothing.
     ///
     /// # Panics
     ///
@@ -1029,7 +1035,7 @@ impl<T: fmt::Debug> Option<T> {
         }
     }
 
-    /// Unwraps an option, expecting [`None`] and returning nothing.
+    /// Consumes `self` while expecting [`None`] and returning nothing.
     ///
     /// # Panics
     ///
@@ -1074,7 +1080,7 @@ impl<T: fmt::Debug> Option<T> {
 }
 
 impl<T: Default> Option<T> {
-    /// Returns the contained value or a default
+    /// Returns the contained [`Some`] value or a default
     ///
     /// Consumes the `self` argument then, if [`Some`], returns the contained
     /// value, otherwise if [`None`], returns the [default value] for that
diff --git a/src/libcore/result.rs b/src/libcore/result.rs
index 809d4bace8e84..0bc29e1bc662c 100644
--- a/src/libcore/result.rs
+++ b/src/libcore/result.rs
@@ -798,8 +798,7 @@ impl<T, E> Result<T, E> {
         }
     }
 
-    /// Unwraps a result, yielding the content of an [`Ok`].
-    /// Else, it returns `optb`.
+    /// Returns the contained [`Ok`] value or a provided default.
     ///
     /// Arguments passed to `unwrap_or` are eagerly evaluated; if you are passing
     /// the result of a function call, it is recommended to use [`unwrap_or_else`],
@@ -814,27 +813,25 @@ impl<T, E> Result<T, E> {
     /// Basic usage:
     ///
     /// ```
-    /// let optb = 2;
+    /// let default = 2;
     /// let x: Result<u32, &str> = Ok(9);
-    /// assert_eq!(x.unwrap_or(optb), 9);
+    /// assert_eq!(x.unwrap_or(default), 9);
     ///
     /// let x: Result<u32, &str> = Err("error");
-    /// assert_eq!(x.unwrap_or(optb), optb);
+    /// assert_eq!(x.unwrap_or(default), default);
     /// ```
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
-    pub fn unwrap_or(self, optb: T) -> T {
+    pub fn unwrap_or(self, default: T) -> T {
         match self {
             Ok(t) => t,
-            Err(_) => optb,
+            Err(_) => default,
         }
     }
 
-    /// Unwraps a result, yielding the content of an [`Ok`].
-    /// If the value is an [`Err`] then it calls `op` with its value.
+    /// Returns the contained [`Ok`] value or computes it from a closure.
     ///
     /// [`Ok`]: enum.Result.html#variant.Ok
-    /// [`Err`]: enum.Result.html#variant.Err
     ///
     /// # Examples
     ///
@@ -937,7 +934,44 @@ impl<T: Clone, E> Result<&mut T, E> {
 }
 
 impl<T, E: fmt::Debug> Result<T, E> {
-    /// Unwraps a result, yielding the content of an [`Ok`].
+    /// Returns the contained [`Ok`] value, consuming the `self` value.
+    ///
+    /// # Panics
+    ///
+    /// Panics if the value is an [`Err`], with a panic message including the
+    /// passed message, and the content of the [`Err`].
+    ///
+    /// [`Ok`]: enum.Result.html#variant.Ok
+    /// [`Err`]: enum.Result.html#variant.Err
+    ///
+    /// # Examples
+    ///
+    /// Basic usage:
+    ///
+    /// ```{.should_panic}
+    /// let x: Result<u32, &str> = Err("emergency failure");
+    /// x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
+    /// ```
+    #[inline]
+    #[track_caller]
+    #[stable(feature = "result_expect", since = "1.4.0")]
+    pub fn expect(self, msg: &str) -> T {
+        match self {
+            Ok(t) => t,
+            Err(e) => unwrap_failed(msg, &e),
+        }
+    }
+
+    /// Returns the contained [`Ok`] value, consuming the `self` value.
+    ///
+    /// Because this function may panic, its use is generally discouraged.
+    /// Instead, prefer to use pattern matching and handle the [`Err`]
+    /// case explicitly, or call [`unwrap_or`], [`unwrap_or_else`], or
+    /// [`unwrap_or_default`].
+    ///
+    /// [`unwrap_or`]: #method.unwrap_or
+    /// [`unwrap_or_else`]: #method.unwrap_or_else
+    /// [`unwrap_or_default`]: #method.unwrap_or_default
     ///
     /// # Panics
     ///
@@ -969,13 +1003,15 @@ impl<T, E: fmt::Debug> Result<T, E> {
             Err(e) => unwrap_failed("called `Result::unwrap()` on an `Err` value", &e),
         }
     }
+}
 
-    /// Unwraps a result, yielding the content of an [`Ok`].
+impl<T: fmt::Debug, E> Result<T, E> {
+    /// Returns the contained [`Err`] value, consuming the `self` value.
     ///
     /// # Panics
     ///
-    /// Panics if the value is an [`Err`], with a panic message including the
-    /// passed message, and the content of the [`Err`].
+    /// Panics if the value is an [`Ok`], with a panic message including the
+    /// passed message, and the content of the [`Ok`].
     ///
     /// [`Ok`]: enum.Result.html#variant.Ok
     /// [`Err`]: enum.Result.html#variant.Err
@@ -985,22 +1021,20 @@ impl<T, E: fmt::Debug> Result<T, E> {
     /// Basic usage:
     ///
     /// ```{.should_panic}
-    /// let x: Result<u32, &str> = Err("emergency failure");
-    /// x.expect("Testing expect"); // panics with `Testing expect: emergency failure`
+    /// let x: Result<u32, &str> = Ok(10);
+    /// x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
     /// ```
     #[inline]
     #[track_caller]
-    #[stable(feature = "result_expect", since = "1.4.0")]
-    pub fn expect(self, msg: &str) -> T {
+    #[stable(feature = "result_expect_err", since = "1.17.0")]
+    pub fn expect_err(self, msg: &str) -> E {
         match self {
-            Ok(t) => t,
-            Err(e) => unwrap_failed(msg, &e),
+            Ok(t) => unwrap_failed(msg, &t),
+            Err(e) => e,
         }
     }
-}
 
-impl<T: fmt::Debug, E> Result<T, E> {
-    /// Unwraps a result, yielding the content of an [`Err`].
+    /// Returns the contained [`Err`] value, consuming the `self` value.
     ///
     /// # Panics
     ///
@@ -1031,38 +1065,10 @@ impl<T: fmt::Debug, E> Result<T, E> {
             Err(e) => e,
         }
     }
-
-    /// Unwraps a result, yielding the content of an [`Err`].
-    ///
-    /// # Panics
-    ///
-    /// Panics if the value is an [`Ok`], with a panic message including the
-    /// passed message, and the content of the [`Ok`].
-    ///
-    /// [`Ok`]: enum.Result.html#variant.Ok
-    /// [`Err`]: enum.Result.html#variant.Err
-    ///
-    /// # Examples
-    ///
-    /// Basic usage:
-    ///
-    /// ```{.should_panic}
-    /// let x: Result<u32, &str> = Ok(10);
-    /// x.expect_err("Testing expect_err"); // panics with `Testing expect_err: 10`
-    /// ```
-    #[inline]
-    #[track_caller]
-    #[stable(feature = "result_expect_err", since = "1.17.0")]
-    pub fn expect_err(self, msg: &str) -> E {
-        match self {
-            Ok(t) => unwrap_failed(msg, &t),
-            Err(e) => e,
-        }
-    }
 }
 
 impl<T: Default, E> Result<T, E> {
-    /// Returns the contained value or a default
+    /// Returns the contained [`Ok`] value or a default
     ///
     /// Consumes the `self` argument then, if [`Ok`], returns the contained
     /// value, otherwise if [`Err`], returns the default value for that
@@ -1101,7 +1107,7 @@ impl<T: Default, E> Result<T, E> {
 
 #[unstable(feature = "unwrap_infallible", reason = "newly added", issue = "61695")]
 impl<T, E: Into<!>> Result<T, E> {
-    /// Unwraps a result that can never be an [`Err`], yielding the content of the [`Ok`].
+    /// Returns the contained [`Ok`] value, but never panics.
     ///
     /// Unlike [`unwrap`], this method is known to never panic on the
     /// result types it is implemented for. Therefore, it can be used
diff --git a/src/librustc/ich/hcx.rs b/src/librustc/ich/hcx.rs
index aade4c3f74c54..76e4b5f01b775 100644
--- a/src/librustc/ich/hcx.rs
+++ b/src/librustc/ich/hcx.rs
@@ -249,6 +249,12 @@ impl<'a> rustc_span::HashStableContext for StableHashingContext<'a> {
         self.hash_spans
     }
 
+    #[inline]
+    fn hash_def_id(&mut self, def_id: DefId, hasher: &mut StableHasher) {
+        let hcx = self;
+        hcx.def_path_hash(def_id).hash_stable(hcx, hasher);
+    }
+
     fn byte_pos_to_line_and_col(
         &mut self,
         byte: BytePos,
diff --git a/src/librustc/ich/impls_hir.rs b/src/librustc/ich/impls_hir.rs
index 0155861549773..625d8a4670f22 100644
--- a/src/librustc/ich/impls_hir.rs
+++ b/src/librustc/ich/impls_hir.rs
@@ -11,12 +11,6 @@ use smallvec::SmallVec;
 use std::mem;
 
 impl<'ctx> rustc_hir::HashStableContext for StableHashingContext<'ctx> {
-    #[inline]
-    fn hash_def_id(&mut self, def_id: DefId, hasher: &mut StableHasher) {
-        let hcx = self;
-        hcx.def_path_hash(def_id).hash_stable(hcx, hasher);
-    }
-
     #[inline]
     fn hash_hir_id(&mut self, hir_id: hir::HirId, hasher: &mut StableHasher) {
         let hcx = self;
diff --git a/src/librustc/lib.rs b/src/librustc/lib.rs
index 2f77792f7a198..ceac68704d2b0 100644
--- a/src/librustc/lib.rs
+++ b/src/librustc/lib.rs
@@ -27,7 +27,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(arbitrary_self_types)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
@@ -39,21 +38,15 @@
 #![feature(marker_trait_attr)]
 #![feature(extern_types)]
 #![feature(nll)]
-#![feature(optin_builtin_traits)]
 #![feature(option_expect_none)]
 #![feature(range_is_empty)]
 #![feature(specialization)]
-#![feature(unboxed_closures)]
-#![feature(thread_local)]
-#![feature(trace_macros)]
 #![feature(trusted_len)]
 #![feature(vec_remove_item)]
 #![feature(stmt_expr_attributes)]
-#![feature(integer_atomics)]
 #![feature(test)]
 #![feature(in_band_lifetimes)]
 #![feature(crate_visibility_modifier)]
-#![feature(log_syntax)]
 #![feature(associated_type_bounds)]
 #![feature(rustc_attrs)]
 #![feature(hash_raw_entry)]
diff --git a/src/librustc/query/mod.rs b/src/librustc/query/mod.rs
index d1bccb961c48b..7cb1f3aa0e851 100644
--- a/src/librustc/query/mod.rs
+++ b/src/librustc/query/mod.rs
@@ -323,7 +323,7 @@ rustc_queries! {
         query associated_item(_: DefId) -> ty::AssocItem {}
 
         /// Collects the associated items defined on a trait or impl.
-        query associated_items(key: DefId) -> ty::AssocItemsIterator<'tcx> {
+        query associated_items(key: DefId) -> &'tcx [ty::AssocItem] {
             desc { |tcx| "collecting associated items of {}", tcx.def_path_str(key) }
         }
 
diff --git a/src/librustc/traits/mod.rs b/src/librustc/traits/mod.rs
index 50068b89687ba..9e6e6047b35d2 100644
--- a/src/librustc/traits/mod.rs
+++ b/src/librustc/traits/mod.rs
@@ -539,6 +539,7 @@ fn vtable_methods<'tcx>(
     tcx.arena.alloc_from_iter(supertraits(tcx, trait_ref).flat_map(move |trait_ref| {
         let trait_methods = tcx
             .associated_items(trait_ref.def_id())
+            .iter()
             .filter(|item| item.kind == ty::AssocKind::Method);
 
         // Now list each method's DefId and InternalSubsts (for within its trait).
diff --git a/src/librustc/traits/object_safety.rs b/src/librustc/traits/object_safety.rs
index d0dbfe73c91d5..3c886ce7f3eb7 100644
--- a/src/librustc/traits/object_safety.rs
+++ b/src/librustc/traits/object_safety.rs
@@ -212,6 +212,7 @@ fn object_safety_violations_for_trait(
     // Check methods for violations.
     let mut violations: Vec<_> = tcx
         .associated_items(trait_def_id)
+        .iter()
         .filter(|item| item.kind == ty::AssocKind::Method)
         .filter_map(|item| {
             object_safety_violation_for_method(tcx, trait_def_id, &item)
@@ -277,6 +278,7 @@ fn object_safety_violations_for_trait(
 
     violations.extend(
         tcx.associated_items(trait_def_id)
+            .iter()
             .filter(|item| item.kind == ty::AssocKind::Const)
             .map(|item| ObjectSafetyViolation::AssocConst(item.ident.name, item.ident.span)),
     );
@@ -632,7 +634,9 @@ fn object_ty_for_trait<'tcx>(
 
     let mut associated_types = traits::supertraits(tcx, ty::Binder::dummy(trait_ref))
         .flat_map(|super_trait_ref| {
-            tcx.associated_items(super_trait_ref.def_id()).map(move |item| (super_trait_ref, item))
+            tcx.associated_items(super_trait_ref.def_id())
+                .iter()
+                .map(move |item| (super_trait_ref, item))
         })
         .filter(|(_, item)| item.kind == ty::AssocKind::Type)
         .collect::<Vec<_>>();
diff --git a/src/librustc/traits/project.rs b/src/librustc/traits/project.rs
index fffcf66075f93..8ea990d1e937e 100644
--- a/src/librustc/traits/project.rs
+++ b/src/librustc/traits/project.rs
@@ -1436,7 +1436,7 @@ fn assoc_ty_def(
         {
             return specialization_graph::NodeItem {
                 node: specialization_graph::Node::Impl(impl_def_id),
-                item,
+                item: *item,
             };
         }
     }
diff --git a/src/librustc/traits/types/specialization_graph.rs b/src/librustc/traits/types/specialization_graph.rs
index 3086850db6d9c..36a84369d4a3a 100644
--- a/src/librustc/traits/types/specialization_graph.rs
+++ b/src/librustc/traits/types/specialization_graph.rs
@@ -81,7 +81,7 @@ impl<'tcx> Node {
     }
 
     /// Iterate over the items defined directly by the given (impl or trait) node.
-    pub fn items(&self, tcx: TyCtxt<'tcx>) -> ty::AssocItemsIterator<'tcx> {
+    pub fn items(&self, tcx: TyCtxt<'tcx>) -> &'tcx [ty::AssocItem] {
         tcx.associated_items(self.def_id())
     }
 
@@ -98,8 +98,10 @@ impl<'tcx> Node {
     ) -> Option<ty::AssocItem> {
         use crate::ty::AssocKind::*;
 
-        tcx.associated_items(self.def_id()).find(move |impl_item| {
-            match (trait_item_kind, impl_item.kind) {
+        tcx.associated_items(self.def_id())
+            .iter()
+            .find(move |impl_item| {
+                match (trait_item_kind, impl_item.kind) {
                 | (Const, Const)
                 | (Method, Method)
                 | (Type, Type)
@@ -112,7 +114,8 @@ impl<'tcx> Node {
                 | (OpaqueTy, _)
                 => false,
             }
-        })
+            })
+            .copied()
     }
 
     pub fn def_id(&self) -> DefId {
diff --git a/src/librustc/traits/wf.rs b/src/librustc/traits/wf.rs
index 9fa3c87477951..c44d45e75807e 100644
--- a/src/librustc/traits/wf.rs
+++ b/src/librustc/traits/wf.rs
@@ -166,7 +166,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
         let extend_cause_with_original_assoc_item_obligation =
             |cause: &mut traits::ObligationCause<'_>,
              pred: &ty::Predicate<'_>,
-             trait_assoc_items: ty::AssocItemsIterator<'_>| {
+             trait_assoc_items: &[ty::AssocItem]| {
                 let trait_item = tcx
                     .hir()
                     .as_local_hir_id(trait_ref.def_id)
@@ -283,6 +283,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                         ) = (&proj.skip_binder().self_ty().kind, item.map(|i| &i.kind))
                         {
                             if let Some((impl_item, trait_assoc_item)) = trait_assoc_items
+                                .iter()
                                 .filter(|i| i.def_id == *item_def_id)
                                 .next()
                                 .and_then(|trait_assoc_item| {
@@ -325,7 +326,7 @@ impl<'a, 'tcx> WfPredicates<'a, 'tcx> {
                 extend_cause_with_original_assoc_item_obligation(
                     &mut cause,
                     &pred,
-                    trait_assoc_items.clone(),
+                    trait_assoc_items,
                 );
                 traits::Obligation::new(cause, param_env, pred)
             });
diff --git a/src/librustc/ty/adjustment.rs b/src/librustc/ty/adjustment.rs
index db034d1618cea..f4006a1cd40c1 100644
--- a/src/librustc/ty/adjustment.rs
+++ b/src/librustc/ty/adjustment.rs
@@ -122,6 +122,7 @@ impl<'tcx> OverloadedDeref<'tcx> {
         };
         let method_def_id = tcx
             .associated_items(trait_def_id.unwrap())
+            .iter()
             .find(|m| m.kind == ty::AssocKind::Method)
             .unwrap()
             .def_id;
diff --git a/src/librustc/ty/instance.rs b/src/librustc/ty/instance.rs
index 51a18f8eae274..c7f19513f666e 100644
--- a/src/librustc/ty/instance.rs
+++ b/src/librustc/ty/instance.rs
@@ -376,6 +376,7 @@ impl<'tcx> Instance<'tcx> {
         let fn_once = tcx.lang_items().fn_once_trait().unwrap();
         let call_once = tcx
             .associated_items(fn_once)
+            .iter()
             .find(|it| it.kind == ty::AssocKind::Method)
             .unwrap()
             .def_id;
diff --git a/src/librustc/ty/mod.rs b/src/librustc/ty/mod.rs
index 2538322431ec9..0118fc4c8ac84 100644
--- a/src/librustc/ty/mod.rs
+++ b/src/librustc/ty/mod.rs
@@ -2705,14 +2705,14 @@ impl<'tcx> TyCtxt<'tcx> {
             .for_each(|&body_id| f(self.hir().body_owner_def_id(body_id)));
     }
 
-    pub fn provided_trait_methods(self, id: DefId) -> Vec<AssocItem> {
+    pub fn provided_trait_methods(self, id: DefId) -> impl Iterator<Item = &'tcx AssocItem> {
         self.associated_items(id)
+            .iter()
             .filter(|item| item.kind == AssocKind::Method && item.defaultness.has_value())
-            .collect()
     }
 
     pub fn trait_relevant_for_never(self, did: DefId) -> bool {
-        self.associated_items(did).any(|item| item.relevant_for_never())
+        self.associated_items(did).iter().any(|item| item.relevant_for_never())
     }
 
     pub fn opt_item_name(self, def_id: DefId) -> Option<Ident> {
@@ -2974,25 +2974,6 @@ impl<'tcx> TyCtxt<'tcx> {
     }
 }
 
-#[derive(Copy, Clone, HashStable)]
-pub struct AssocItemsIterator<'tcx> {
-    pub items: &'tcx [AssocItem],
-}
-
-impl<'tcx> Iterator for AssocItemsIterator<'tcx> {
-    type Item = AssocItem;
-
-    #[inline]
-    fn next(&mut self) -> Option<AssocItem> {
-        if let Some((first, rest)) = self.items.split_first() {
-            self.items = rest;
-            Some(*first)
-        } else {
-            None
-        }
-    }
-}
-
 #[derive(Clone, HashStable)]
 pub struct AdtSizedConstraint<'tcx>(pub &'tcx [Ty<'tcx>]);
 
diff --git a/src/librustc/ty/sty.rs b/src/librustc/ty/sty.rs
index 4c5bc3debde54..0718853b1df59 100644
--- a/src/librustc/ty/sty.rs
+++ b/src/librustc/ty/sty.rs
@@ -1066,6 +1066,7 @@ impl<'tcx> ProjectionTy<'tcx> {
     ) -> ProjectionTy<'tcx> {
         let item_def_id = tcx
             .associated_items(trait_ref.def_id)
+            .iter()
             .find(|item| {
                 item.kind == ty::AssocKind::Type
                     && tcx.hygienic_eq(item_name, item.ident, trait_ref.def_id)
diff --git a/src/librustc/ty/util.rs b/src/librustc/ty/util.rs
index 4dfff85d53147..5d5fa4090c800 100644
--- a/src/librustc/ty/util.rs
+++ b/src/librustc/ty/util.rs
@@ -355,7 +355,7 @@ impl<'tcx> TyCtxt<'tcx> {
         let mut dtor_did = None;
         let ty = self.type_of(adt_did);
         self.for_each_relevant_impl(drop_trait, ty, |impl_did| {
-            if let Some(item) = self.associated_items(impl_did).next() {
+            if let Some(item) = self.associated_items(impl_did).first() {
                 if validate(self, impl_did).is_ok() {
                     dtor_did = Some(item.def_id);
                 }
diff --git a/src/librustc_ast_pretty/pprust.rs b/src/librustc_ast_pretty/pprust.rs
index d9077d1606f3a..78bf149f0e01a 100644
--- a/src/librustc_ast_pretty/pprust.rs
+++ b/src/librustc_ast_pretty/pprust.rs
@@ -1074,12 +1074,15 @@ impl<'a> State<'a> {
     fn print_associated_type(
         &mut self,
         ident: ast::Ident,
+        generics: &ast::Generics,
         bounds: &ast::GenericBounds,
         ty: Option<&ast::Ty>,
     ) {
         self.word_space("type");
         self.print_ident(ident);
+        self.print_generic_params(&generics.params);
         self.print_type_bounds(":", bounds);
+        self.print_where_clause(&generics.where_clause);
         if let Some(ty) = ty {
             self.s.space();
             self.word_space("=");
@@ -1474,7 +1477,7 @@ impl<'a> State<'a> {
                 self.print_fn_full(sig, item.ident, &item.generics, &item.vis, body, &item.attrs);
             }
             ast::AssocItemKind::TyAlias(bounds, ty) => {
-                self.print_associated_type(item.ident, bounds, ty.as_deref());
+                self.print_associated_type(item.ident, &item.generics, bounds, ty.as_deref());
             }
             ast::AssocItemKind::Macro(mac) => {
                 self.print_mac(mac);
diff --git a/src/librustc_codegen_llvm/debuginfo/create_scope_map.rs b/src/librustc_codegen_llvm/debuginfo/create_scope_map.rs
index eba05ed5d7787..cdb9657e1ff3c 100644
--- a/src/librustc_codegen_llvm/debuginfo/create_scope_map.rs
+++ b/src/librustc_codegen_llvm/debuginfo/create_scope_map.rs
@@ -66,14 +66,8 @@ fn make_mir_scope(
     if !has_variables.contains(scope) {
         // Do not create a DIScope if there are no variables
         // defined in this MIR Scope, to avoid debuginfo bloat.
-
-        // However, we don't skip creating a nested scope if
-        // our parent is the root, because we might want to
-        // put arguments in the root and not have shadowing.
-        if parent_scope.scope_metadata.unwrap() != fn_metadata {
-            debug_context.scopes[scope] = parent_scope;
-            return;
-        }
+        debug_context.scopes[scope] = parent_scope;
+        return;
     }
 
     let loc = span_start(cx, scope_data.span);
diff --git a/src/librustc_codegen_llvm/debuginfo/mod.rs b/src/librustc_codegen_llvm/debuginfo/mod.rs
index c4a52a73e25d9..c1a7bb5087824 100644
--- a/src/librustc_codegen_llvm/debuginfo/mod.rs
+++ b/src/librustc_codegen_llvm/debuginfo/mod.rs
@@ -5,7 +5,6 @@ use rustc_codegen_ssa::mir::debuginfo::VariableKind::*;
 
 use self::metadata::{file_metadata, type_metadata, TypeMap};
 use self::namespace::mangled_name_of_instance;
-use self::source_loc::InternalDebugLocation::{self, UnknownLocation};
 use self::type_names::compute_debuginfo_type_name;
 use self::utils::{create_DIArray, is_node_local_to_unit, span_start, DIB};
 
@@ -38,7 +37,7 @@ use std::ffi::CString;
 use rustc::ty::layout::{self, HasTyCtxt, LayoutOf, Size};
 use rustc_codegen_ssa::traits::*;
 use rustc_span::symbol::Symbol;
-use rustc_span::{self, BytePos, Pos, Span};
+use rustc_span::{self, BytePos, Span};
 use smallvec::SmallVec;
 use syntax::ast;
 
@@ -52,7 +51,6 @@ mod utils;
 pub use self::create_scope_map::compute_mir_scopes;
 pub use self::metadata::create_global_var_metadata;
 pub use self::metadata::extend_scope_to_file;
-pub use self::source_loc::set_source_location;
 
 #[allow(non_upper_case_globals)]
 const DW_TAG_auto_variable: c_uint = 0x100;
@@ -148,7 +146,6 @@ impl DebugInfoBuilderMethods for Builder<'a, 'll, 'tcx> {
     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
     fn dbg_var_addr(
         &mut self,
-        dbg_context: &FunctionDebugContext<&'ll DIScope>,
         dbg_var: &'ll DIVariable,
         scope_metadata: &'ll DIScope,
         variable_alloca: Self::Value,
@@ -156,12 +153,11 @@ impl DebugInfoBuilderMethods for Builder<'a, 'll, 'tcx> {
         indirect_offsets: &[Size],
         span: Span,
     ) {
-        assert!(!dbg_context.source_locations_enabled);
         let cx = self.cx();
 
-        let loc = span_start(cx, span);
-
         // Convert the direct and indirect offsets to address ops.
+        // FIXME(eddyb) use `const`s instead of getting the values via FFI,
+        // the values should match the ones in the DWARF standard anyway.
         let op_deref = || unsafe { llvm::LLVMRustDIBuilderCreateOpDeref() };
         let op_plus_uconst = || unsafe { llvm::LLVMRustDIBuilderCreateOpPlusUconst() };
         let mut addr_ops = SmallVec::<[_; 8]>::new();
@@ -178,37 +174,32 @@ impl DebugInfoBuilderMethods for Builder<'a, 'll, 'tcx> {
             }
         }
 
-        // FIXME(eddyb) maybe this information could be extracted from `var`,
+        // FIXME(eddyb) maybe this information could be extracted from `dbg_var`,
         // to avoid having to pass it down in both places?
-        source_loc::set_debug_location(
-            self,
-            InternalDebugLocation::new(scope_metadata, loc.line, loc.col.to_usize()),
-        );
+        // NB: `var` doesn't seem to know about the column, so that's a limitation.
+        let dbg_loc = cx.create_debug_loc(scope_metadata, span);
         unsafe {
-            let debug_loc = llvm::LLVMGetCurrentDebugLocation(self.llbuilder);
             // FIXME(eddyb) replace `llvm.dbg.declare` with `llvm.dbg.addr`.
-            let instr = llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
+            llvm::LLVMRustDIBuilderInsertDeclareAtEnd(
                 DIB(cx),
                 variable_alloca,
                 dbg_var,
                 addr_ops.as_ptr(),
                 addr_ops.len() as c_uint,
-                debug_loc,
+                dbg_loc,
                 self.llbb(),
             );
-
-            llvm::LLVMSetInstDebugLocation(self.llbuilder, instr);
         }
-        source_loc::set_debug_location(self, UnknownLocation);
     }
 
-    fn set_source_location(
-        &mut self,
-        debug_context: &mut FunctionDebugContext<&'ll DIScope>,
-        scope: &'ll DIScope,
-        span: Span,
-    ) {
-        set_source_location(debug_context, &self, scope, span)
+    fn set_source_location(&mut self, scope: &'ll DIScope, span: Span) {
+        debug!("set_source_location: {}", self.sess().source_map().span_to_string(span));
+
+        let dbg_loc = self.cx().create_debug_loc(scope, span);
+
+        unsafe {
+            llvm::LLVMSetCurrentDebugLocation(self.llbuilder, dbg_loc);
+        }
     }
     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self) {
         gdb::insert_reference_to_gdb_debug_scripts_section_global(self)
@@ -342,7 +333,6 @@ impl DebugInfoMethods<'tcx> for CodegenCx<'ll, 'tcx> {
         };
         let mut fn_debug_context = FunctionDebugContext {
             scopes: IndexVec::from_elem(null_scope, &mir.source_scopes),
-            source_locations_enabled: false,
             defining_crate: def_id.krate,
         };
 
diff --git a/src/librustc_codegen_llvm/debuginfo/source_loc.rs b/src/librustc_codegen_llvm/debuginfo/source_loc.rs
index 6afaca44e0e96..1f871c7d207a4 100644
--- a/src/librustc_codegen_llvm/debuginfo/source_loc.rs
+++ b/src/librustc_codegen_llvm/debuginfo/source_loc.rs
@@ -1,79 +1,35 @@
-use self::InternalDebugLocation::*;
-
 use super::metadata::UNKNOWN_COLUMN_NUMBER;
 use super::utils::{debug_context, span_start};
-use rustc_codegen_ssa::mir::debuginfo::FunctionDebugContext;
 
-use crate::builder::Builder;
-use crate::llvm;
+use crate::common::CodegenCx;
 use crate::llvm::debuginfo::DIScope;
-use log::debug;
+use crate::llvm::{self, Value};
 use rustc_codegen_ssa::traits::*;
 
 use libc::c_uint;
 use rustc_span::{Pos, Span};
 
-/// Sets the current debug location at the beginning of the span.
-///
-/// Maps to a call to llvm::LLVMSetCurrentDebugLocation(...).
-pub fn set_source_location<D>(
-    debug_context: &FunctionDebugContext<D>,
-    bx: &Builder<'_, 'll, '_>,
-    scope: &'ll DIScope,
-    span: Span,
-) {
-    let dbg_loc = if debug_context.source_locations_enabled {
-        debug!("set_source_location: {}", bx.sess().source_map().span_to_string(span));
-        let loc = span_start(bx.cx(), span);
-        InternalDebugLocation::new(scope, loc.line, loc.col.to_usize())
-    } else {
-        UnknownLocation
-    };
-    set_debug_location(bx, dbg_loc);
-}
-
-#[derive(Copy, Clone, PartialEq)]
-pub enum InternalDebugLocation<'ll> {
-    KnownLocation { scope: &'ll DIScope, line: usize, col: usize },
-    UnknownLocation,
-}
-
-impl InternalDebugLocation<'ll> {
-    pub fn new(scope: &'ll DIScope, line: usize, col: usize) -> Self {
-        KnownLocation { scope, line, col }
-    }
-}
-
-pub fn set_debug_location(bx: &Builder<'_, 'll, '_>, debug_location: InternalDebugLocation<'ll>) {
-    let metadata_node = match debug_location {
-        KnownLocation { scope, line, col } => {
-            // For MSVC, set the column number to zero.
-            // Otherwise, emit it. This mimics clang behaviour.
-            // See discussion in https://github.com/rust-lang/rust/issues/42921
-            let col_used = if bx.sess().target.target.options.is_like_msvc {
-                UNKNOWN_COLUMN_NUMBER
-            } else {
-                col as c_uint
-            };
-            debug!("setting debug location to {} {}", line, col);
-
-            unsafe {
-                Some(llvm::LLVMRustDIBuilderCreateDebugLocation(
-                    debug_context(bx.cx()).llcontext,
-                    line as c_uint,
-                    col_used,
-                    scope,
-                    None,
-                ))
-            }
+impl CodegenCx<'ll, '_> {
+    pub fn create_debug_loc(&self, scope: &'ll DIScope, span: Span) -> &'ll Value {
+        let loc = span_start(self, span);
+
+        // For MSVC, set the column number to zero.
+        // Otherwise, emit it. This mimics clang behaviour.
+        // See discussion in https://github.com/rust-lang/rust/issues/42921
+        let col_used = if self.sess().target.target.options.is_like_msvc {
+            UNKNOWN_COLUMN_NUMBER
+        } else {
+            loc.col.to_usize() as c_uint
+        };
+
+        unsafe {
+            llvm::LLVMRustDIBuilderCreateDebugLocation(
+                debug_context(self).llcontext,
+                loc.line as c_uint,
+                col_used,
+                scope,
+                None,
+            )
         }
-        UnknownLocation => {
-            debug!("clearing debug location ");
-            None
-        }
-    };
-
-    unsafe {
-        llvm::LLVMSetCurrentDebugLocation(bx.llbuilder, metadata_node);
     }
 }
diff --git a/src/librustc_codegen_llvm/lib.rs b/src/librustc_codegen_llvm/lib.rs
index 8091a74854070..98a3e695fa079 100644
--- a/src/librustc_codegen_llvm/lib.rs
+++ b/src/librustc_codegen_llvm/lib.rs
@@ -6,18 +6,11 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(bool_to_option)]
-#![feature(box_patterns)]
-#![feature(box_syntax)]
 #![feature(const_cstr_unchecked)]
 #![feature(crate_visibility_modifier)]
 #![feature(extern_types)]
 #![feature(in_band_lifetimes)]
-#![feature(libc)]
 #![feature(nll)]
-#![feature(optin_builtin_traits)]
-#![feature(concat_idents)]
-#![feature(link_args)]
-#![feature(static_nobundle)]
 #![feature(trusted_len)]
 #![recursion_limit = "256"]
 
@@ -196,7 +189,7 @@ unsafe impl Sync for LlvmCodegenBackend {}
 
 impl LlvmCodegenBackend {
     pub fn new() -> Box<dyn CodegenBackend> {
-        box LlvmCodegenBackend(())
+        Box::new(LlvmCodegenBackend(()))
     }
 }
 
@@ -245,7 +238,7 @@ impl CodegenBackend for LlvmCodegenBackend {
     }
 
     fn metadata_loader(&self) -> Box<MetadataLoaderDyn> {
-        box metadata::LlvmMetadataLoader
+        Box::new(metadata::LlvmMetadataLoader)
     }
 
     fn provide(&self, providers: &mut ty::query::Providers<'_>) {
@@ -262,12 +255,12 @@ impl CodegenBackend for LlvmCodegenBackend {
         metadata: EncodedMetadata,
         need_metadata_module: bool,
     ) -> Box<dyn Any> {
-        box rustc_codegen_ssa::base::codegen_crate(
+        Box::new(rustc_codegen_ssa::base::codegen_crate(
             LlvmCodegenBackend(()),
             tcx,
             metadata,
             need_metadata_module,
-        )
+        ))
     }
 
     fn join_codegen(
diff --git a/src/librustc_codegen_llvm/llvm/ffi.rs b/src/librustc_codegen_llvm/llvm/ffi.rs
index 3f37f86676c98..146b7d3d76c5e 100644
--- a/src/librustc_codegen_llvm/llvm/ffi.rs
+++ b/src/librustc_codegen_llvm/llvm/ffi.rs
@@ -909,9 +909,7 @@ extern "C" {
     pub fn LLVMDisposeBuilder(Builder: &'a mut Builder<'a>);
 
     // Metadata
-    pub fn LLVMSetCurrentDebugLocation(Builder: &Builder<'a>, L: Option<&'a Value>);
-    pub fn LLVMGetCurrentDebugLocation(Builder: &Builder<'a>) -> &'a Value;
-    pub fn LLVMSetInstDebugLocation(Builder: &Builder<'a>, Inst: &'a Value);
+    pub fn LLVMSetCurrentDebugLocation(Builder: &Builder<'a>, L: &'a Value);
 
     // Terminators
     pub fn LLVMBuildRetVoid(B: &Builder<'a>) -> &'a Value;
diff --git a/src/librustc_codegen_llvm/metadata.rs b/src/librustc_codegen_llvm/metadata.rs
index abe34bb148ce5..0f30c2c020de7 100644
--- a/src/librustc_codegen_llvm/metadata.rs
+++ b/src/librustc_codegen_llvm/metadata.rs
@@ -22,10 +22,11 @@ impl MetadataLoader for LlvmMetadataLoader {
         // Use ArchiveRO for speed here, it's backed by LLVM and uses mmap
         // internally to read the file. We also avoid even using a memcpy by
         // just keeping the archive along while the metadata is in use.
-        let archive = ArchiveRO::open(filename).map(|ar| OwningRef::new(box ar)).map_err(|e| {
-            debug!("llvm didn't like `{}`: {}", filename.display(), e);
-            format!("failed to read rlib metadata in '{}': {}", filename.display(), e)
-        })?;
+        let archive =
+            ArchiveRO::open(filename).map(|ar| OwningRef::new(Box::new(ar))).map_err(|e| {
+                debug!("llvm didn't like `{}`: {}", filename.display(), e);
+                format!("failed to read rlib metadata in '{}': {}", filename.display(), e)
+            })?;
         let buf: OwningRef<_, [u8]> = archive.try_map(|ar| {
             ar.iter()
                 .filter_map(|s| s.ok())
@@ -44,9 +45,10 @@ impl MetadataLoader for LlvmMetadataLoader {
             let buf = path_to_c_string(filename);
             let mb = llvm::LLVMRustCreateMemoryBufferWithContentsOfFile(buf.as_ptr())
                 .ok_or_else(|| format!("error reading library: '{}'", filename.display()))?;
-            let of = ObjectFile::new(mb).map(|of| OwningRef::new(box of)).ok_or_else(|| {
-                format!("provided path not an object file: '{}'", filename.display())
-            })?;
+            let of =
+                ObjectFile::new(mb).map(|of| OwningRef::new(Box::new(of))).ok_or_else(|| {
+                    format!("provided path not an object file: '{}'", filename.display())
+                })?;
             let buf = of.try_map(|of| search_meta_section(of, target, filename))?;
             Ok(rustc_erase_owner!(buf))
         }
diff --git a/src/librustc_codegen_ssa/lib.rs b/src/librustc_codegen_ssa/lib.rs
index f39587122c56d..a2bb39b9e4019 100644
--- a/src/librustc_codegen_ssa/lib.rs
+++ b/src/librustc_codegen_ssa/lib.rs
@@ -1,10 +1,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
-#![feature(box_syntax)]
-#![feature(core_intrinsics)]
-#![feature(libc)]
-#![feature(stmt_expr_attributes)]
 #![feature(try_blocks)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
diff --git a/src/librustc_codegen_ssa/mir/debuginfo.rs b/src/librustc_codegen_ssa/mir/debuginfo.rs
index f66496d10fb16..976a656a29b19 100644
--- a/src/librustc_codegen_ssa/mir/debuginfo.rs
+++ b/src/librustc_codegen_ssa/mir/debuginfo.rs
@@ -14,7 +14,6 @@ use super::{FunctionCx, LocalRef};
 
 pub struct FunctionDebugContext<D> {
     pub scopes: IndexVec<mir::SourceScope, DebugScope<D>>,
-    pub source_locations_enabled: bool,
     pub defining_crate: CrateNum,
 }
 
@@ -53,11 +52,10 @@ impl<D> DebugScope<D> {
 }
 
 impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
-    pub fn set_debug_loc(&mut self, bx: &mut Bx, source_info: mir::SourceInfo) {
+    pub fn set_debug_loc(&self, bx: &mut Bx, source_info: mir::SourceInfo) {
         let (scope, span) = self.debug_loc(source_info);
-        if let Some(debug_context) = &mut self.debug_context {
-            // FIXME(eddyb) get rid of this unwrap somehow.
-            bx.set_source_location(debug_context, scope.unwrap(), span);
+        if let Some(scope) = scope {
+            bx.set_source_location(scope, span);
         }
     }
 
@@ -210,11 +208,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             return;
         }
 
-        let debug_context = match &self.debug_context {
-            Some(debug_context) => debug_context,
-            None => return,
-        };
-
         // FIXME(eddyb) add debuginfo for unsized places too.
         let base = match local_ref {
             LocalRef::Place(place) => place,
@@ -264,7 +257,6 @@ impl<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>> FunctionCx<'a, 'tcx, Bx> {
             if let Some(scope) = scope {
                 if let Some(dbg_var) = var.dbg_var {
                     bx.dbg_var_addr(
-                        debug_context,
                         dbg_var,
                         scope,
                         base.llval,
diff --git a/src/librustc_codegen_ssa/mir/mod.rs b/src/librustc_codegen_ssa/mir/mod.rs
index 8a6284479c722..64ead19b35869 100644
--- a/src/librustc_codegen_ssa/mir/mod.rs
+++ b/src/librustc_codegen_ssa/mir/mod.rs
@@ -230,13 +230,6 @@ pub fn codegen_mir<'a, 'tcx, Bx: BuilderMethods<'a, 'tcx>>(
         bx.br(fx.blocks[mir::START_BLOCK]);
     }
 
-    // Up until here, IR instructions for this function have explicitly not been annotated with
-    // source code location, so we don't step into call setup code. From here on, source location
-    // emitting should be enabled.
-    if let Some(debug_context) = &mut fx.debug_context {
-        debug_context.source_locations_enabled = true;
-    }
-
     let rpo = traversal::reverse_postorder(&mir_body);
     let mut visited = BitSet::new_empty(mir_body.basic_blocks().len());
 
diff --git a/src/librustc_codegen_ssa/traits/debuginfo.rs b/src/librustc_codegen_ssa/traits/debuginfo.rs
index 22a4e96b9e4bf..3688ae51b3918 100644
--- a/src/librustc_codegen_ssa/traits/debuginfo.rs
+++ b/src/librustc_codegen_ssa/traits/debuginfo.rs
@@ -49,7 +49,6 @@ pub trait DebugInfoBuilderMethods: BackendTypes {
     // names (choose between `dbg`, `debug`, `debuginfo`, `debug_info` etc.).
     fn dbg_var_addr(
         &mut self,
-        dbg_context: &FunctionDebugContext<Self::DIScope>,
         dbg_var: Self::DIVariable,
         scope_metadata: Self::DIScope,
         variable_alloca: Self::Value,
@@ -58,12 +57,7 @@ pub trait DebugInfoBuilderMethods: BackendTypes {
         indirect_offsets: &[Size],
         span: Span,
     );
-    fn set_source_location(
-        &mut self,
-        debug_context: &mut FunctionDebugContext<Self::DIScope>,
-        scope: Self::DIScope,
-        span: Span,
-    );
+    fn set_source_location(&mut self, scope: Self::DIScope, span: Span);
     fn insert_reference_to_gdb_debug_scripts_section_global(&mut self);
     fn set_var_name(&mut self, value: Self::Value, name: &str);
 }
diff --git a/src/librustc_codegen_utils/lib.rs b/src/librustc_codegen_utils/lib.rs
index 6b802bf530e86..38906bbaef810 100644
--- a/src/librustc_codegen_utils/lib.rs
+++ b/src/librustc_codegen_utils/lib.rs
@@ -3,10 +3,6 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(arbitrary_self_types)]
-#![feature(box_patterns)]
-#![feature(box_syntax)]
-#![feature(core_intrinsics)]
 #![feature(never_type)]
 #![feature(nll)]
 #![feature(in_band_lifetimes)]
diff --git a/src/librustc_data_structures/lib.rs b/src/librustc_data_structures/lib.rs
index aaac7fb4460cd..13792a0c890c4 100644
--- a/src/librustc_data_structures/lib.rs
+++ b/src/librustc_data_structures/lib.rs
@@ -12,7 +12,6 @@
 #![feature(generators)]
 #![feature(generator_trait)]
 #![feature(fn_traits)]
-#![feature(unsize)]
 #![feature(specialization)]
 #![feature(optin_builtin_traits)]
 #![feature(nll)]
@@ -20,11 +19,9 @@
 #![feature(hash_raw_entry)]
 #![feature(stmt_expr_attributes)]
 #![feature(core_intrinsics)]
-#![feature(integer_atomics)]
 #![feature(test)]
 #![feature(associated_type_bounds)]
 #![feature(thread_id_value)]
-#![cfg_attr(unix, feature(libc))]
 #![allow(rustc::default_hash_types)]
 
 #[macro_use]
diff --git a/src/librustc_driver/lib.rs b/src/librustc_driver/lib.rs
index 019ff431bcb97..52c6399498534 100644
--- a/src/librustc_driver/lib.rs
+++ b/src/librustc_driver/lib.rs
@@ -5,12 +5,7 @@
 //! This API is completely unstable and subject to change.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(box_syntax)]
-#![cfg_attr(unix, feature(libc))]
 #![feature(nll)]
-#![feature(set_stdio)]
-#![feature(no_debug)]
-#![feature(integer_atomics)]
 #![recursion_limit = "256"]
 
 pub extern crate getopts;
diff --git a/src/librustc_error_codes/error_codes/E0277.md b/src/librustc_error_codes/error_codes/E0277.md
index 2034a5b988cbf..2e2cd5e01fb6a 100644
--- a/src/librustc_error_codes/error_codes/E0277.md
+++ b/src/librustc_error_codes/error_codes/E0277.md
@@ -1,5 +1,7 @@
 You tried to use a type which doesn't implement some trait in a place which
-expected that trait. Erroneous code example:
+expected that trait.
+
+Erroneous code example:
 
 ```compile_fail,E0277
 // here we declare the Foo trait with a bar method
diff --git a/src/librustc_error_codes/error_codes/E0282.md b/src/librustc_error_codes/error_codes/E0282.md
index 54a9de0025a3d..49d2205f92c2a 100644
--- a/src/librustc_error_codes/error_codes/E0282.md
+++ b/src/librustc_error_codes/error_codes/E0282.md
@@ -1,3 +1,11 @@
+The compiler could not infer a type and asked for a type annotation.
+
+Erroneous code example:
+
+```compile_fail,E0282
+let x = "hello".chars().rev().collect();
+```
+
 This error indicates that type inference did not result in one unique possible
 type, and extra information is required. In most cases this can be provided
 by adding a type annotation. Sometimes you need to specify a generic type
@@ -8,13 +16,9 @@ parameter with a `FromIterator` bound, which for a `char` iterator is
 implemented by `Vec` and `String` among others. Consider the following snippet
 that reverses the characters of a string:
 
-```compile_fail,E0282
-let x = "hello".chars().rev().collect();
-```
-
-In this case, the compiler cannot infer what the type of `x` should be:
-`Vec<char>` and `String` are both suitable candidates. To specify which type to
-use, you can use a type annotation on `x`:
+In the first code example, the compiler cannot infer what the type of `x` should
+be: `Vec<char>` and `String` are both suitable candidates. To specify which type
+to use, you can use a type annotation on `x`:
 
 ```
 let x: Vec<char> = "hello".chars().rev().collect();
diff --git a/src/librustc_errors/lib.rs b/src/librustc_errors/lib.rs
index 97667febc3ca2..594e813def8a9 100644
--- a/src/librustc_errors/lib.rs
+++ b/src/librustc_errors/lib.rs
@@ -4,9 +4,7 @@
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(crate_visibility_modifier)]
-#![cfg_attr(unix, feature(libc))]
 #![feature(nll)]
-#![feature(optin_builtin_traits)]
 
 pub use emitter::ColorConfig;
 
diff --git a/src/librustc_hir/lib.rs b/src/librustc_hir/lib.rs
index f54fa291bd6e8..e4edd34bd6e23 100644
--- a/src/librustc_hir/lib.rs
+++ b/src/librustc_hir/lib.rs
@@ -12,7 +12,7 @@
 extern crate rustc_data_structures;
 
 pub mod def;
-pub mod def_id;
+pub use rustc_span::def_id;
 mod hir;
 pub mod hir_id;
 pub mod intravisit;
diff --git a/src/librustc_hir/print.rs b/src/librustc_hir/print.rs
index b0d2f96c71a03..071c3de4b1c2c 100644
--- a/src/librustc_hir/print.rs
+++ b/src/librustc_hir/print.rs
@@ -454,14 +454,17 @@ impl<'a> State<'a> {
     fn print_associated_type(
         &mut self,
         ident: ast::Ident,
+        generics: &hir::Generics<'_>,
         bounds: Option<hir::GenericBounds<'_>>,
         ty: Option<&hir::Ty<'_>>,
     ) {
         self.word_space("type");
         self.print_ident(ident);
+        self.print_generic_params(&generics.params);
         if let Some(bounds) = bounds {
             self.print_bounds(":", bounds);
         }
+        self.print_where_clause(&generics.where_clause);
         if let Some(ty) = ty {
             self.s.space();
             self.word_space("=");
@@ -902,6 +905,7 @@ impl<'a> State<'a> {
             hir::TraitItemKind::Type(ref bounds, ref default) => {
                 self.print_associated_type(
                     ti.ident,
+                    &ti.generics,
                     Some(bounds),
                     default.as_ref().map(|ty| &**ty),
                 );
@@ -930,7 +934,7 @@ impl<'a> State<'a> {
                 self.ann.nested(self, Nested::Body(body));
             }
             hir::ImplItemKind::TyAlias(ref ty) => {
-                self.print_associated_type(ii.ident, None, Some(ty));
+                self.print_associated_type(ii.ident, &ii.generics, None, Some(ty));
             }
             hir::ImplItemKind::OpaqueTy(bounds) => {
                 self.word_space("type");
diff --git a/src/librustc_hir/stable_hash_impls.rs b/src/librustc_hir/stable_hash_impls.rs
index 294074cd3e5a4..e8407b537011b 100644
--- a/src/librustc_hir/stable_hash_impls.rs
+++ b/src/librustc_hir/stable_hash_impls.rs
@@ -1,6 +1,5 @@
 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 
-use crate::def_id::DefId;
 use crate::hir::{BodyId, Expr, ImplItemId, ItemId, Mod, TraitItemId, Ty, VisibilityKind};
 use crate::hir_id::HirId;
 
@@ -8,7 +7,6 @@ use crate::hir_id::HirId;
 /// This is a hack to allow using the `HashStable_Generic` derive macro
 /// instead of implementing everything in librustc.
 pub trait HashStableContext: syntax::HashStableContext + rustc_target::HashStableContext {
-    fn hash_def_id(&mut self, _: DefId, hasher: &mut StableHasher);
     fn hash_hir_id(&mut self, _: HirId, hasher: &mut StableHasher);
     fn hash_body_id(&mut self, _: BodyId, hasher: &mut StableHasher);
     fn hash_reference_to_item(&mut self, _: HirId, hasher: &mut StableHasher);
@@ -24,12 +22,6 @@ impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for HirId {
     }
 }
 
-impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for DefId {
-    fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
-        hcx.hash_def_id(*self, hasher)
-    }
-}
-
 impl<HirCtx: crate::HashStableContext> HashStable<HirCtx> for BodyId {
     fn hash_stable(&self, hcx: &mut HirCtx, hasher: &mut StableHasher) {
         hcx.hash_body_id(*self, hasher)
diff --git a/src/librustc_incremental/lib.rs b/src/librustc_incremental/lib.rs
index 7ce4def2886b8..ca824fde7efc1 100644
--- a/src/librustc_incremental/lib.rs
+++ b/src/librustc_incremental/lib.rs
@@ -3,7 +3,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
-#![feature(specialization)]
 #![recursion_limit = "256"]
 
 #[macro_use]
diff --git a/src/librustc_interface/lib.rs b/src/librustc_interface/lib.rs
index e4e6849ab8e59..ba1e2216ca805 100644
--- a/src/librustc_interface/lib.rs
+++ b/src/librustc_interface/lib.rs
@@ -2,10 +2,8 @@
 #![feature(box_syntax)]
 #![feature(set_stdio)]
 #![feature(nll)]
-#![feature(arbitrary_self_types)]
 #![feature(generator_trait)]
 #![feature(generators)]
-#![cfg_attr(unix, feature(libc))]
 #![recursion_limit = "256"]
 
 #[cfg(unix)]
diff --git a/src/librustc_lint/lib.rs b/src/librustc_lint/lib.rs
index 78e9d0f14f2de..6e2db65c84005 100644
--- a/src/librustc_lint/lib.rs
+++ b/src/librustc_lint/lib.rs
@@ -28,7 +28,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![cfg_attr(test, feature(test))]
 #![feature(bool_to_option)]
-#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
 #![feature(never_type)]
diff --git a/src/librustc_metadata/lib.rs b/src/librustc_metadata/lib.rs
index d94f23ff8bc6a..d4cc3c32616ac 100644
--- a/src/librustc_metadata/lib.rs
+++ b/src/librustc_metadata/lib.rs
@@ -1,15 +1,11 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(bool_to_option)]
-#![feature(box_patterns)]
 #![feature(core_intrinsics)]
 #![feature(crate_visibility_modifier)]
 #![feature(drain_filter)]
 #![feature(in_band_lifetimes)]
-#![feature(libc)]
 #![feature(nll)]
 #![feature(proc_macro_internals)]
-#![feature(proc_macro_quote)]
-#![feature(rustc_private)]
 #![feature(specialization)]
 #![feature(stmt_expr_attributes)]
 #![recursion_limit = "256"]
diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs
index f064869d66471..4f1b90e34cf00 100644
--- a/src/librustc_mir/lib.rs
+++ b/src/librustc_mir/lib.rs
@@ -6,21 +6,15 @@ Rust MIR: a lowered representation of Rust. Also: an experiment!
 
 #![feature(nll)]
 #![feature(in_band_lifetimes)]
-#![feature(inner_deref)]
 #![feature(bool_to_option)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
-#![feature(core_intrinsics)]
-#![feature(decl_macro)]
 #![feature(drain_filter)]
 #![feature(exhaustive_patterns)]
 #![feature(iter_order_by)]
 #![feature(never_type)]
 #![feature(specialization)]
-#![feature(try_trait)]
-#![feature(unicode_internals)]
-#![feature(slice_concat_ext)]
 #![feature(trusted_len)]
 #![feature(try_blocks)]
 #![feature(associated_type_bounds)]
diff --git a/src/librustc_mir/shim.rs b/src/librustc_mir/shim.rs
index 94a5f2b3bf86d..a8c66be359c4a 100644
--- a/src/librustc_mir/shim.rs
+++ b/src/librustc_mir/shim.rs
@@ -68,6 +68,7 @@ fn make_shim<'tcx>(tcx: TyCtxt<'tcx>, instance: ty::InstanceDef<'tcx>) -> &'tcx
             let fn_mut = tcx.lang_items().fn_mut_trait().unwrap();
             let call_mut = tcx
                 .associated_items(fn_mut)
+                .iter()
                 .find(|it| it.kind == ty::AssocKind::Method)
                 .unwrap()
                 .def_id;
diff --git a/src/librustc_mir/util/elaborate_drops.rs b/src/librustc_mir/util/elaborate_drops.rs
index 1be3da4b3d85a..091ae1bbb799d 100644
--- a/src/librustc_mir/util/elaborate_drops.rs
+++ b/src/librustc_mir/util/elaborate_drops.rs
@@ -539,7 +539,7 @@ where
         debug!("destructor_call_block({:?}, {:?})", self, succ);
         let tcx = self.tcx();
         let drop_trait = tcx.lang_items().drop_trait().unwrap();
-        let drop_fn = tcx.associated_items(drop_trait).next().unwrap();
+        let drop_fn = tcx.associated_items(drop_trait)[0];
         let ty = self.place_ty(self.place);
         let substs = tcx.mk_substs_trait(ty, &[]);
 
diff --git a/src/librustc_passes/reachable.rs b/src/librustc_passes/reachable.rs
index 667898046ac36..888f4370dd5e8 100644
--- a/src/librustc_passes/reachable.rs
+++ b/src/librustc_passes/reachable.rs
@@ -362,12 +362,12 @@ impl<'a, 'tcx> ItemLikeVisitor<'tcx> for CollectPrivateImplItemsVisitor<'a, 'tcx
                     return;
                 }
 
-                let provided_trait_methods = self.tcx.provided_trait_methods(trait_def_id);
-                self.worklist.reserve(provided_trait_methods.len());
-                for default_method in provided_trait_methods {
-                    let hir_id = self.tcx.hir().as_local_hir_id(default_method.def_id).unwrap();
-                    self.worklist.push(hir_id);
-                }
+                // FIXME(#53488) remove `let`
+                let tcx = self.tcx;
+                self.worklist.extend(
+                    tcx.provided_trait_methods(trait_def_id)
+                        .map(|assoc| tcx.hir().as_local_hir_id(assoc.def_id).unwrap()),
+                );
             }
         }
     }
diff --git a/src/librustc_passes/stability.rs b/src/librustc_passes/stability.rs
index 4009cc6d725ab..12debfb66a431 100644
--- a/src/librustc_passes/stability.rs
+++ b/src/librustc_passes/stability.rs
@@ -468,6 +468,7 @@ impl Visitor<'tcx> for Checker<'tcx> {
                         let trait_item_def_id = self
                             .tcx
                             .associated_items(trait_did)
+                            .iter()
                             .find(|item| item.ident.name == impl_item.ident.name)
                             .map(|item| item.def_id);
                         if let Some(def_id) = trait_item_def_id {
diff --git a/src/librustc_resolve/lib.rs b/src/librustc_resolve/lib.rs
index af4ba4c0eb20e..2e63c3e170605 100644
--- a/src/librustc_resolve/lib.rs
+++ b/src/librustc_resolve/lib.rs
@@ -9,7 +9,6 @@
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![feature(bool_to_option)]
 #![feature(crate_visibility_modifier)]
-#![feature(label_break_value)]
 #![feature(nll)]
 #![recursion_limit = "256"]
 
diff --git a/src/librustc_save_analysis/lib.rs b/src/librustc_save_analysis/lib.rs
index e32f47443667b..401e172275113 100644
--- a/src/librustc_save_analysis/lib.rs
+++ b/src/librustc_save_analysis/lib.rs
@@ -423,6 +423,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
                             qualname.push_str(&self.tcx.def_path_str(def_id));
                             self.tcx
                                 .associated_items(def_id)
+                                .iter()
                                 .find(|item| item.ident.name == ident.name)
                                 .map(|item| decl_id = Some(item.def_id));
                         }
@@ -717,6 +718,7 @@ impl<'l, 'tcx> SaveContext<'l, 'tcx> {
                     let ti = self.tcx.associated_item(decl_id);
                     self.tcx
                         .associated_items(ti.container.id())
+                        .iter()
                         .find(|item| {
                             item.ident.name == ti.ident.name && item.defaultness.has_value()
                         })
diff --git a/src/librustc_hir/def_id.rs b/src/librustc_span/def_id.rs
similarity index 95%
rename from src/librustc_hir/def_id.rs
rename to src/librustc_span/def_id.rs
index 7ee778ddd8ec7..6cdfd0500ca84 100644
--- a/src/librustc_hir/def_id.rs
+++ b/src/librustc_span/def_id.rs
@@ -1,3 +1,5 @@
+use crate::HashStableContext;
+use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
 use rustc_data_structures::AtomicRef;
 use rustc_index::vec::Idx;
 use rustc_serialize::{Decoder, Encoder};
@@ -18,15 +20,6 @@ pub enum CrateNum {
     Index(CrateId),
 }
 
-impl ::std::fmt::Debug for CrateNum {
-    fn fmt(&self, fmt: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
-        match self {
-            CrateNum::Index(id) => write!(fmt, "crate{}", id.private),
-            CrateNum::ReservedForIncrCompCache => write!(fmt, "crate for decoding incr comp cache"),
-        }
-    }
-}
-
 /// Item definitions in the currently-compiled crate would have the `CrateNum`
 /// `LOCAL_CRATE` in their `DefId`.
 pub const LOCAL_CRATE: CrateNum = CrateNum::Index(CrateId::from_u32_const(0));
@@ -100,6 +93,15 @@ impl rustc_serialize::UseSpecializedDecodable for CrateNum {
     }
 }
 
+impl ::std::fmt::Debug for CrateNum {
+    fn fmt(&self, fmt: &mut ::std::fmt::Formatter<'_>) -> ::std::fmt::Result {
+        match self {
+            CrateNum::Index(id) => write!(fmt, "crate{}", id.private),
+            CrateNum::ReservedForIncrCompCache => write!(fmt, "crate for decoding incr comp cache"),
+        }
+    }
+}
+
 rustc_index::newtype_index! {
     /// A DefIndex is an index into the hir-map for a crate, identifying a
     /// particular definition. It should really be considered an interned
@@ -207,3 +209,9 @@ impl fmt::Debug for LocalDefId {
 
 impl rustc_serialize::UseSpecializedEncodable for LocalDefId {}
 impl rustc_serialize::UseSpecializedDecodable for LocalDefId {}
+
+impl<CTX: HashStableContext> HashStable<CTX> for DefId {
+    fn hash_stable(&self, hcx: &mut CTX, hasher: &mut StableHasher) {
+        hcx.hash_def_id(*self, hasher)
+    }
+}
diff --git a/src/librustc_span/lib.rs b/src/librustc_span/lib.rs
index 413bd77daae24..b7c6b0c4f690e 100644
--- a/src/librustc_span/lib.rs
+++ b/src/librustc_span/lib.rs
@@ -8,9 +8,6 @@
 #![feature(crate_visibility_modifier)]
 #![feature(nll)]
 #![feature(optin_builtin_traits)]
-#![feature(rustc_attrs)]
-#![feature(specialization)]
-#![feature(step_trait)]
 
 use rustc_data_structures::AtomicRef;
 use rustc_macros::HashStable_Generic;
@@ -25,7 +22,8 @@ use edition::Edition;
 pub mod hygiene;
 use hygiene::Transparency;
 pub use hygiene::{DesugaringKind, ExpnData, ExpnId, ExpnKind, MacroKind, SyntaxContext};
-
+pub mod def_id;
+use def_id::DefId;
 mod span_encoding;
 pub use span_encoding::{Span, DUMMY_SP};
 
@@ -1561,6 +1559,7 @@ fn lookup_line(lines: &[BytePos], pos: BytePos) -> isize {
 /// instead of implementing everything in librustc.
 pub trait HashStableContext {
     fn hash_spans(&self) -> bool;
+    fn hash_def_id(&mut self, _: DefId, hasher: &mut StableHasher);
     fn byte_pos_to_line_and_col(
         &mut self,
         byte: BytePos,
diff --git a/src/librustc_target/lib.rs b/src/librustc_target/lib.rs
index a9db0254a7d11..71150e74f70d4 100644
--- a/src/librustc_target/lib.rs
+++ b/src/librustc_target/lib.rs
@@ -8,7 +8,6 @@
 //! LLVM.
 
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
-#![feature(box_syntax)]
 #![feature(bool_to_option)]
 #![feature(nll)]
 
diff --git a/src/librustc_ty/ty.rs b/src/librustc_ty/ty.rs
index aa05165e3de32..b032acf82f582 100644
--- a/src/librustc_ty/ty.rs
+++ b/src/librustc_ty/ty.rs
@@ -206,12 +206,10 @@ fn associated_item_def_ids(tcx: TyCtxt<'_>, def_id: DefId) -> &[DefId] {
     }
 }
 
-fn associated_items<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> ty::AssocItemsIterator<'tcx> {
-    ty::AssocItemsIterator {
-        items: tcx.arena.alloc_from_iter(
-            tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did)),
-        ),
-    }
+fn associated_items<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx [ty::AssocItem] {
+    tcx.arena.alloc_from_iter(
+        tcx.associated_item_def_ids(def_id).iter().map(|did| tcx.associated_item(*did)),
+    )
 }
 
 fn def_span(tcx: TyCtxt<'_>, def_id: DefId) -> Span {
diff --git a/src/librustc_typeck/astconv.rs b/src/librustc_typeck/astconv.rs
index 6bd120d818d09..2909d0f8c54e7 100644
--- a/src/librustc_typeck/astconv.rs
+++ b/src/librustc_typeck/astconv.rs
@@ -1109,7 +1109,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
         trait_def_id: DefId,
         assoc_name: ast::Ident,
     ) -> bool {
-        self.tcx().associated_items(trait_def_id).any(|item| {
+        self.tcx().associated_items(trait_def_id).iter().any(|item| {
             item.kind == ty::AssocKind::Type
                 && self.tcx().hygienic_eq(assoc_name, item.ident, trait_def_id)
         })
@@ -1347,6 +1347,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             tcx.adjust_ident_and_get_scope(binding.item_name, candidate.def_id(), hir_ref_id);
         let assoc_ty = tcx
             .associated_items(candidate.def_id())
+            .iter()
             .find(|i| i.kind == ty::AssocKind::Type && i.ident.modern() == assoc_ident)
             .expect("missing associated type");
 
@@ -1512,6 +1513,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                     ty::Predicate::Trait(pred, _) => {
                         associated_types.entry(span).or_default().extend(
                             tcx.associated_items(pred.def_id())
+                                .iter()
                                 .filter(|item| item.kind == ty::AssocKind::Type)
                                 .map(|item| item.def_id),
                         );
@@ -1969,6 +1971,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
                 let bound_span = self
                     .tcx()
                     .associated_items(bound.def_id())
+                    .iter()
                     .find(|item| {
                         item.kind == ty::AssocKind::Type
                             && self.tcx().hygienic_eq(assoc_name, item.ident, bound.def_id())
@@ -2198,6 +2201,7 @@ impl<'o, 'tcx> dyn AstConv<'tcx> + 'o {
             tcx.adjust_ident_and_get_scope(assoc_ident, trait_did, hir_ref_id);
         let item = tcx
             .associated_items(trait_did)
+            .iter()
             .find(|i| Namespace::from(i.kind) == Namespace::Type && i.ident.modern() == assoc_ident)
             .expect("missing associated type");
 
diff --git a/src/librustc_typeck/check/closure.rs b/src/librustc_typeck/check/closure.rs
index 26777b3b01048..707125b3fd522 100644
--- a/src/librustc_typeck/check/closure.rs
+++ b/src/librustc_typeck/check/closure.rs
@@ -248,7 +248,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         if is_gen {
             // Check that we deduce the signature from the `<_ as std::ops::Generator>::Return`
             // associated item and not yield.
-            let return_assoc_item = self.tcx.associated_items(gen_trait).nth(1).unwrap().def_id;
+            let return_assoc_item = self.tcx.associated_items(gen_trait)[1].def_id;
             if return_assoc_item != projection.projection_def_id() {
                 debug!("deduce_sig_from_projection: not return assoc item of generator");
                 return None;
@@ -673,7 +673,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
 
         // The `Future` trait has only one associted item, `Output`,
         // so check that this is what we see.
-        let output_assoc_item = self.tcx.associated_items(future_trait).nth(0).unwrap().def_id;
+        let output_assoc_item = self.tcx.associated_items(future_trait)[0].def_id;
         if output_assoc_item != predicate.projection_ty.item_def_id {
             span_bug!(
                 cause_span,
diff --git a/src/librustc_typeck/check/demand.rs b/src/librustc_typeck/check/demand.rs
index e0f9fcc69325c..8c7f1330820e3 100644
--- a/src/librustc_typeck/check/demand.rs
+++ b/src/librustc_typeck/check/demand.rs
@@ -536,6 +536,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 let item_def_id = self
                     .tcx
                     .associated_items(deref_trait)
+                    .iter()
                     .find(|item| item.kind == ty::AssocKind::Type)
                     .unwrap()
                     .def_id;
diff --git a/src/librustc_typeck/check/method/mod.rs b/src/librustc_typeck/check/method/mod.rs
index e90c2ef5e4361..67d8030a9d69b 100644
--- a/src/librustc_typeck/check/method/mod.rs
+++ b/src/librustc_typeck/check/method/mod.rs
@@ -474,8 +474,13 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
         item_name: ast::Ident,
         ns: Namespace,
     ) -> Option<ty::AssocItem> {
-        self.tcx.associated_items(def_id).find(|item| {
-            Namespace::from(item.kind) == ns && self.tcx.hygienic_eq(item_name, item.ident, def_id)
-        })
+        self.tcx
+            .associated_items(def_id)
+            .iter()
+            .find(|item| {
+                Namespace::from(item.kind) == ns
+                    && self.tcx.hygienic_eq(item_name, item.ident, def_id)
+            })
+            .copied()
     }
 }
diff --git a/src/librustc_typeck/check/method/probe.rs b/src/librustc_typeck/check/method/probe.rs
index 2444fc60f77ba..497a401a031e5 100644
--- a/src/librustc_typeck/check/method/probe.rs
+++ b/src/librustc_typeck/check/method/probe.rs
@@ -1696,10 +1696,12 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                 let max_dist = max(name.as_str().len(), 3) / 3;
                 self.tcx
                     .associated_items(def_id)
+                    .iter()
                     .filter(|x| {
                         let dist = lev_distance(&*name.as_str(), &x.ident.as_str());
                         Namespace::from(x.kind) == Namespace::Value && dist > 0 && dist <= max_dist
                     })
+                    .copied()
                     .collect()
             } else {
                 self.fcx
@@ -1707,7 +1709,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
                     .map_or(Vec::new(), |x| vec![x])
             }
         } else {
-            self.tcx.associated_items(def_id).collect()
+            self.tcx.associated_items(def_id).to_vec()
         }
     }
 }
diff --git a/src/librustc_typeck/check/mod.rs b/src/librustc_typeck/check/mod.rs
index 7e5d27d93b3cb..54a5330df399d 100644
--- a/src/librustc_typeck/check/mod.rs
+++ b/src/librustc_typeck/check/mod.rs
@@ -1976,6 +1976,7 @@ fn check_impl_items_against_trait<'tcx>(
         let ty_impl_item = tcx.associated_item(tcx.hir().local_def_id(impl_item.hir_id));
         let ty_trait_item = tcx
             .associated_items(impl_trait_ref.def_id)
+            .iter()
             .find(|ac| {
                 Namespace::from(&impl_item.kind) == Namespace::from(ac.kind)
                     && tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id)
@@ -1983,6 +1984,7 @@ fn check_impl_items_against_trait<'tcx>(
             .or_else(|| {
                 // Not compatible, but needed for the error message
                 tcx.associated_items(impl_trait_ref.def_id)
+                    .iter()
                     .find(|ac| tcx.hygienic_eq(ty_impl_item.ident, ac.ident, impl_trait_ref.def_id))
             });
 
@@ -2096,7 +2098,7 @@ fn check_impl_items_against_trait<'tcx>(
 
         if !is_implemented && !traits::impl_is_default(tcx, impl_id) {
             if !trait_item.defaultness.has_value() {
-                missing_items.push(trait_item);
+                missing_items.push(*trait_item);
             } else if associated_type_overridden {
                 invalidated_items.push(trait_item.ident);
             }
@@ -5096,7 +5098,7 @@ impl<'a, 'tcx> FnCtxt<'a, 'tcx> {
                 // 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 item_def_id = self.tcx.associated_items(future_trait).next().unwrap().def_id;
+                let item_def_id = self.tcx.associated_items(future_trait)[0].def_id;
                 let predicate =
                     ty::Predicate::Projection(ty::Binder::bind(ty::ProjectionPredicate {
                         // `<T as Future>::Output`
diff --git a/src/librustc_typeck/coherence/inherent_impls_overlap.rs b/src/librustc_typeck/coherence/inherent_impls_overlap.rs
index 3e17b661cf4ce..fb9c173f52000 100644
--- a/src/librustc_typeck/coherence/inherent_impls_overlap.rs
+++ b/src/librustc_typeck/coherence/inherent_impls_overlap.rs
@@ -1,6 +1,6 @@
 use crate::namespace::Namespace;
 use rustc::traits::{self, IntercrateMode, SkipLeakCheck};
-use rustc::ty::TyCtxt;
+use rustc::ty::{AssocItem, TyCtxt};
 use rustc_errors::struct_span_err;
 use rustc_hir as hir;
 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
@@ -17,38 +17,60 @@ struct InherentOverlapChecker<'tcx> {
 }
 
 impl InherentOverlapChecker<'tcx> {
+    /// Checks whether any associated items in impls 1 and 2 share the same identifier and
+    /// namespace.
+    fn impls_have_common_items(&self, impl1: DefId, impl2: DefId) -> bool {
+        let impl_items1 = self.tcx.associated_items(impl1);
+        let impl_items2 = self.tcx.associated_items(impl2);
+
+        for item1 in &impl_items1[..] {
+            for item2 in &impl_items2[..] {
+                // Avoid costly `.modern()` calls as much as possible by doing them as late as we
+                // can. Compare raw symbols first.
+                if item1.ident.name == item2.ident.name
+                    && Namespace::from(item1.kind) == Namespace::from(item2.kind)
+                {
+                    // Symbols and namespace match, compare hygienically.
+                    if item1.ident.modern() == item2.ident.modern() {
+                        return true;
+                    }
+                }
+            }
+        }
+
+        false
+    }
+
     fn check_for_common_items_in_impls(
         &self,
         impl1: DefId,
         impl2: DefId,
         overlap: traits::OverlapResult<'_>,
     ) {
-        let name_and_namespace = |def_id| {
-            let item = self.tcx.associated_item(def_id);
-            (item.ident.modern(), Namespace::from(item.kind))
-        };
+        let name_and_namespace =
+            |assoc: &AssocItem| (assoc.ident.modern(), Namespace::from(assoc.kind));
 
-        let impl_items1 = self.tcx.associated_item_def_ids(impl1);
-        let impl_items2 = self.tcx.associated_item_def_ids(impl2);
+        let impl_items1 = self.tcx.associated_items(impl1);
+        let impl_items2 = self.tcx.associated_items(impl2);
 
-        for &item1 in &impl_items1[..] {
+        for item1 in &impl_items1[..] {
             let (name, namespace) = name_and_namespace(item1);
 
-            for &item2 in &impl_items2[..] {
+            for item2 in &impl_items2[..] {
                 if (name, namespace) == name_and_namespace(item2) {
                     let mut err = struct_span_err!(
                         self.tcx.sess,
-                        self.tcx.span_of_impl(item1).unwrap(),
+                        self.tcx.span_of_impl(item1.def_id).unwrap(),
                         E0592,
                         "duplicate definitions with name `{}`",
                         name
                     );
                     err.span_label(
-                        self.tcx.span_of_impl(item1).unwrap(),
+                        self.tcx.span_of_impl(item1.def_id).unwrap(),
                         format!("duplicate definitions for `{}`", name),
                     );
                     err.span_label(
-                        self.tcx.span_of_impl(item2).unwrap(),
+                        self.tcx.span_of_impl(item2.def_id).unwrap(),
                         format!("other definition for `{}`", name),
                     );
 
@@ -66,27 +88,21 @@ impl InherentOverlapChecker<'tcx> {
         }
     }
 
-    fn check_for_overlapping_inherent_impls(&self, ty_def_id: DefId) {
-        let impls = self.tcx.inherent_impls(ty_def_id);
-
-        for (i, &impl1_def_id) in impls.iter().enumerate() {
-            for &impl2_def_id in &impls[(i + 1)..] {
-                traits::overlapping_impls(
-                    self.tcx,
-                    impl1_def_id,
-                    impl2_def_id,
-                    IntercrateMode::Issue43355,
-                    // We go ahead and just skip the leak check for
-                    // inherent impls without warning.
-                    SkipLeakCheck::Yes,
-                    |overlap| {
-                        self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id, overlap);
-                        false
-                    },
-                    || true,
-                );
-            }
-        }
+    fn check_for_overlapping_inherent_impls(&self, impl1_def_id: DefId, impl2_def_id: DefId) {
+        traits::overlapping_impls(
+            self.tcx,
+            impl1_def_id,
+            impl2_def_id,
+            IntercrateMode::Issue43355,
+            // We go ahead and just skip the leak check for
+            // inherent impls without warning.
+            SkipLeakCheck::Yes,
+            |overlap| {
+                self.check_for_common_items_in_impls(impl1_def_id, impl2_def_id, overlap);
+                false
+            },
+            || true,
+        );
     }
 }
 
@@ -97,8 +113,16 @@ impl ItemLikeVisitor<'v> for InherentOverlapChecker<'tcx> {
             | hir::ItemKind::Struct(..)
             | hir::ItemKind::Trait(..)
             | hir::ItemKind::Union(..) => {
-                let type_def_id = self.tcx.hir().local_def_id(item.hir_id);
-                self.check_for_overlapping_inherent_impls(type_def_id);
+                let ty_def_id = self.tcx.hir().local_def_id(item.hir_id);
+                let impls = self.tcx.inherent_impls(ty_def_id);
+
+                for (i, &impl1_def_id) in impls.iter().enumerate() {
+                    for &impl2_def_id in &impls[(i + 1)..] {
+                        if self.impls_have_common_items(impl1_def_id, impl2_def_id) {
+                            self.check_for_overlapping_inherent_impls(impl1_def_id, impl2_def_id);
+                        }
+                    }
+                }
             }
             _ => {}
         }
diff --git a/src/librustc_typeck/lib.rs b/src/librustc_typeck/lib.rs
index 05ea9b1ac56dc..474868f0dd6c4 100644
--- a/src/librustc_typeck/lib.rs
+++ b/src/librustc_typeck/lib.rs
@@ -58,10 +58,8 @@ This API is completely unstable and subject to change.
 #![doc(html_root_url = "https://doc.rust-lang.org/nightly/")]
 #![allow(non_camel_case_types)]
 #![feature(bool_to_option)]
-#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(crate_visibility_modifier)]
-#![feature(exhaustive_patterns)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
 #![feature(try_blocks)]
diff --git a/src/librustdoc/clean/blanket_impl.rs b/src/librustdoc/clean/blanket_impl.rs
index 18ebd254507ea..288446b6219ce 100644
--- a/src/librustdoc/clean/blanket_impl.rs
+++ b/src/librustdoc/clean/blanket_impl.rs
@@ -87,7 +87,6 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                     .cx
                     .tcx
                     .provided_trait_methods(trait_def_id)
-                    .into_iter()
                     .map(|meth| meth.ident.to_string())
                     .collect();
 
@@ -115,6 +114,8 @@ impl<'a, 'tcx> BlanketImplFinder<'a, 'tcx> {
                             .cx
                             .tcx
                             .associated_items(impl_def_id)
+                            .iter()
+                            .copied()
                             .collect::<Vec<_>>()
                             .clean(self.cx),
                         polarity: None,
diff --git a/src/librustdoc/clean/inline.rs b/src/librustdoc/clean/inline.rs
index df72bf0b56e61..90ce8802f6584 100644
--- a/src/librustdoc/clean/inline.rs
+++ b/src/librustdoc/clean/inline.rs
@@ -191,7 +191,7 @@ pub fn record_extern_fqn(cx: &DocContext<'_>, did: DefId, kind: clean::TypeKind)
 
 pub fn build_external_trait(cx: &DocContext<'_>, did: DefId) -> clean::Trait {
     let auto_trait = cx.tcx.trait_def(did).has_auto_impl;
-    let trait_items = cx.tcx.associated_items(did).map(|item| item.clean(cx)).collect();
+    let trait_items = cx.tcx.associated_items(did).iter().map(|item| item.clean(cx)).collect();
     let predicates = cx.tcx.predicates_of(did);
     let generics = (cx.tcx.generics_of(did), predicates).clean(cx);
     let generics = filter_non_trait_generics(did, generics);
@@ -376,6 +376,7 @@ pub fn build_impl(
     } else {
         (
             tcx.associated_items(did)
+                .iter()
                 .filter_map(|item| {
                     if associated_trait.is_some() || item.vis == ty::Visibility::Public {
                         Some(item.clean(cx))
@@ -401,9 +402,7 @@ pub fn build_impl(
 
     let provided = trait_
         .def_id()
-        .map(|did| {
-            tcx.provided_trait_methods(did).into_iter().map(|meth| meth.ident.to_string()).collect()
-        })
+        .map(|did| tcx.provided_trait_methods(did).map(|meth| meth.ident.to_string()).collect())
         .unwrap_or_default();
 
     debug!("build_impl: impl {:?} for {:?}", trait_.def_id(), for_.def_id());
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index f140f11b09098..87edc88611f3a 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -2108,11 +2108,7 @@ impl Clean<Vec<Item>> for doctree::Impl<'_> {
         let provided: FxHashSet<String> = trait_
             .def_id()
             .map(|did| {
-                cx.tcx
-                    .provided_trait_methods(did)
-                    .into_iter()
-                    .map(|meth| meth.ident.to_string())
-                    .collect()
+                cx.tcx.provided_trait_methods(did).map(|meth| meth.ident.to_string()).collect()
             })
             .unwrap_or_default();
 
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index ed3f0f94e0ed8..4e0a2d9427431 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -3,19 +3,15 @@
     html_playground_url = "https://play.rust-lang.org/"
 )]
 #![feature(rustc_private)]
-#![feature(arbitrary_self_types)]
 #![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(in_band_lifetimes)]
 #![feature(nll)]
-#![feature(set_stdio)]
 #![feature(test)]
 #![feature(vec_remove_item)]
 #![feature(ptr_offset_from)]
 #![feature(crate_visibility_modifier)]
-#![feature(drain_filter)]
 #![feature(never_type)]
-#![feature(unicode_internals)]
 #![recursion_limit = "256"]
 
 extern crate env_logger;
diff --git a/src/librustdoc/passes/collect_intra_doc_links.rs b/src/librustdoc/passes/collect_intra_doc_links.rs
index 332d19fbfaeca..9ecf6d531299f 100644
--- a/src/librustdoc/passes/collect_intra_doc_links.rs
+++ b/src/librustdoc/passes/collect_intra_doc_links.rs
@@ -206,6 +206,7 @@ impl<'a, 'tcx> LinkCollector<'a, 'tcx> {
                 return cx
                     .tcx
                     .associated_items(did)
+                    .iter()
                     .find(|item| item.ident.name == item_name)
                     .and_then(|item| match item.kind {
                         ty::AssocKind::Method => Some("method"),
diff --git a/src/libserialize/lib.rs b/src/libserialize/lib.rs
index 280fb078f7de4..b990e71bef0dd 100644
--- a/src/libserialize/lib.rs
+++ b/src/libserialize/lib.rs
@@ -10,7 +10,6 @@ Core encoding and decoding interfaces.
     test(attr(allow(unused_variables), deny(warnings)))
 )]
 #![feature(box_syntax)]
-#![feature(core_intrinsics)]
 #![feature(specialization)]
 #![feature(never_type)]
 #![feature(nll)]
diff --git a/src/test/pretty/gat-bounds.pp b/src/test/pretty/gat-bounds.pp
new file mode 100644
index 0000000000000..0c95add490110
--- /dev/null
+++ b/src/test/pretty/gat-bounds.pp
@@ -0,0 +1,25 @@
+// Check that associated types print generic parameters and where clauses.
+// See issue #67509.
+
+// pretty-compare-only
+// pp-exact:gat-bounds.pp
+
+#![feature(generic_associated_types)]
+
+trait X {
+    type
+    Y<T>: Trait
+    where
+    Self: Sized;
+}
+
+impl X for () {
+    type
+    Y<T>
+    where
+    Self: Sized
+    =
+    u32;
+}
+
+fn main() { }
diff --git a/src/test/pretty/gat-bounds.rs b/src/test/pretty/gat-bounds.rs
new file mode 100644
index 0000000000000..1275f432a3c50
--- /dev/null
+++ b/src/test/pretty/gat-bounds.rs
@@ -0,0 +1,17 @@
+// Check that associated types print generic parameters and where clauses.
+// See issue #67509.
+
+// pretty-compare-only
+// pp-exact:gat-bounds.pp
+
+#![feature(generic_associated_types)]
+
+trait X {
+    type Y<T>: Trait where Self: Sized;
+}
+
+impl X for () {
+    type Y<T> where Self: Sized = u32;
+}
+
+fn main() { }
diff --git a/src/test/ui/consts/miri_unleashed/mutable_const2.stderr b/src/test/ui/consts/miri_unleashed/mutable_const2.stderr
index a316d8f1698ac..3eb8e0ec18288 100644
--- a/src/test/ui/consts/miri_unleashed/mutable_const2.stderr
+++ b/src/test/ui/consts/miri_unleashed/mutable_const2.stderr
@@ -10,7 +10,7 @@ error: internal compiler error: mutable allocation in constant
 LL | const MUTABLE_BEHIND_RAW: *mut i32 = &UnsafeCell::new(42) as *const _ as *mut _;
    | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:357:17
+thread 'rustc' panicked at 'no errors encountered even though `delay_span_bug` issued', src/librustc_errors/lib.rs:355:17
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace
 
 error: internal compiler error: unexpected panic