remove some unneeded imports

55 files changed, 64 insertions, 135 deletions

diff --git a/library/alloc/benches/btree/map.rs b/library/alloc/benches/btree/map.rs
index 1f6b87fb0e4..ec1b0a8eba0 100644
--- a/library/alloc/benches/btree/map.rs
+++ b/library/alloc/benches/btree/map.rs
@@ -1,5 +1,4 @@
 use std::collections::BTreeMap;
-use std::iter::Iterator;
 use std::ops::RangeBounds;
 use std::vec::Vec;
 
diff --git a/library/alloc/benches/vec.rs b/library/alloc/benches/vec.rs
index 663f6b9dd1c..c1d3e1bdfe7 100644
--- a/library/alloc/benches/vec.rs
+++ b/library/alloc/benches/vec.rs
@@ -1,5 +1,5 @@
 use rand::RngCore;
-use std::iter::{repeat, FromIterator};
+use std::iter::repeat;
 use test::{black_box, Bencher};
 
 #[bench]
diff --git a/library/alloc/src/boxed.rs b/library/alloc/src/boxed.rs
index 09041bb119b..7f88327bf19 100644
--- a/library/alloc/src/boxed.rs
+++ b/library/alloc/src/boxed.rs
@@ -150,16 +150,13 @@ use core::any::Any;
 use core::async_iter::AsyncIterator;
 use core::borrow;
 use core::cmp::Ordering;
-use core::convert::{From, TryFrom};
 use core::error::Error;
 use core::fmt;
 use core::future::Future;
 use core::hash::{Hash, Hasher};
-#[cfg(not(no_global_oom_handling))]
-use core::iter::FromIterator;
-use core::iter::{FusedIterator, Iterator};
+use core::iter::FusedIterator;
 use core::marker::Tuple;
-use core::marker::{Unpin, Unsize};
+use core::marker::Unsize;
 use core::mem;
 use core::ops::{
     CoerceUnsized, Deref, DerefMut, DispatchFromDyn, Generator, GeneratorState, Receiver,
diff --git a/library/alloc/src/collections/binary_heap/mod.rs b/library/alloc/src/collections/binary_heap/mod.rs
index bc86125c7c3..8aa4d342e6e 100644
--- a/library/alloc/src/collections/binary_heap/mod.rs
+++ b/library/alloc/src/collections/binary_heap/mod.rs
@@ -144,7 +144,7 @@
 #![stable(feature = "rust1", since = "1.0.0")]
 
 use core::fmt;
-use core::iter::{FromIterator, FusedIterator, InPlaceIterable, SourceIter, TrustedLen};
+use core::iter::{FusedIterator, InPlaceIterable, SourceIter, TrustedLen};
 use core::mem::{self, swap, ManuallyDrop};
 use core::num::NonZeroUsize;
 use core::ops::{Deref, DerefMut};
@@ -263,7 +263,6 @@ mod tests;
 /// more detailed analysis.
 ///
 /// [`core::cmp::Reverse`]: core::cmp::Reverse
-/// [`Ord`]: core::cmp::Ord
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
 /// [push]: BinaryHeap::push
@@ -1418,7 +1417,6 @@ impl<T> FusedIterator for Iter<'_, T> {}
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: BinaryHeap::into_iter
-/// [`IntoIterator`]: core::iter::IntoIterator
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Clone)]
 pub struct IntoIter<T> {
diff --git a/library/alloc/src/collections/btree/map.rs b/library/alloc/src/collections/btree/map.rs
index 61db46314b7..7b378ccc01a 100644
--- a/library/alloc/src/collections/btree/map.rs
+++ b/library/alloc/src/collections/btree/map.rs
@@ -3,7 +3,7 @@ use core::borrow::Borrow;
 use core::cmp::Ordering;
 use core::fmt::{self, Debug};
 use core::hash::{Hash, Hasher};
-use core::iter::{FromIterator, FusedIterator};
+use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem::{self, ManuallyDrop};
 use core::ops::{Bound, Index, RangeBounds};
@@ -420,7 +420,6 @@ impl<'a, K: 'a, V: 'a> Default for IterMut<'a, K, V> {
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: IntoIterator::into_iter
-/// [`IntoIterator`]: core::iter::IntoIterator
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_insignificant_dtor]
 pub struct IntoIter<
@@ -650,7 +649,7 @@ impl<K, V, A: Allocator + Clone> BTreeMap<K, V, A> {
     #[stable(feature = "rust1", since = "1.0.0")]
     pub fn clear(&mut self) {
         // avoid moving the allocator
-        mem::drop(BTreeMap {
+        drop(BTreeMap {
             root: mem::replace(&mut self.root, None),
             length: mem::replace(&mut self.length, 0),
             alloc: self.alloc.clone(),
diff --git a/library/alloc/src/collections/btree/map/tests.rs b/library/alloc/src/collections/btree/map/tests.rs
index 76c2f27b466..1c6ed0b4f8b 100644
--- a/library/alloc/src/collections/btree/map/tests.rs
+++ b/library/alloc/src/collections/btree/map/tests.rs
@@ -9,8 +9,7 @@ use crate::testing::ord_chaos::{Cyclic3, Governed, Governor};
 use crate::testing::rng::DeterministicRng;
 use crate::vec::Vec;
 use std::cmp::Ordering;
-use std::convert::TryFrom;
-use std::iter::{self, FromIterator};
+use std::iter;
 use std::mem;
 use std::ops::Bound::{self, Excluded, Included, Unbounded};
 use std::ops::RangeBounds;
diff --git a/library/alloc/src/collections/btree/set.rs b/library/alloc/src/collections/btree/set.rs
index a7cb3948aa1..232a017314e 100644
--- a/library/alloc/src/collections/btree/set.rs
+++ b/library/alloc/src/collections/btree/set.rs
@@ -4,7 +4,7 @@ use core::cmp::Ordering::{self, Equal, Greater, Less};
 use core::cmp::{max, min};
 use core::fmt::{self, Debug};
 use core::hash::{Hash, Hasher};
-use core::iter::{FromIterator, FusedIterator, Peekable};
+use core::iter::{FusedIterator, Peekable};
 use core::mem::ManuallyDrop;
 use core::ops::{BitAnd, BitOr, BitXor, RangeBounds, Sub};
 
@@ -30,7 +30,6 @@ use crate::alloc::{Allocator, Global};
 /// Iterators returned by [`BTreeSet::iter`] produce their items in order, and take worst-case
 /// logarithmic and amortized constant time per item returned.
 ///
-/// [`Ord`]: core::cmp::Ord
 /// [`Cell`]: core::cell::Cell
 /// [`RefCell`]: core::cell::RefCell
 ///
@@ -147,7 +146,6 @@ impl<T: fmt::Debug> fmt::Debug for Iter<'_, T> {
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: BTreeSet#method.into_iter
-/// [`IntoIterator`]: core::iter::IntoIterator
 #[stable(feature = "rust1", since = "1.0.0")]
 #[derive(Debug)]
 pub struct IntoIter<
diff --git a/library/alloc/src/collections/btree/set/tests.rs b/library/alloc/src/collections/btree/set/tests.rs
index 7b8d41a6031..a7c839d77ed 100644
--- a/library/alloc/src/collections/btree/set/tests.rs
+++ b/library/alloc/src/collections/btree/set/tests.rs
@@ -4,7 +4,6 @@ use crate::testing::rng::DeterministicRng;
 use crate::vec::Vec;
 use std::cmp::Ordering;
 use std::hash::{Hash, Hasher};
-use std::iter::FromIterator;
 use std::ops::Bound::{Excluded, Included};
 use std::panic::{catch_unwind, AssertUnwindSafe};
 
diff --git a/library/alloc/src/collections/linked_list.rs b/library/alloc/src/collections/linked_list.rs
index 080a4a14eda..1743a155c5a 100644
--- a/library/alloc/src/collections/linked_list.rs
+++ b/library/alloc/src/collections/linked_list.rs
@@ -15,7 +15,7 @@
 use core::cmp::Ordering;
 use core::fmt;
 use core::hash::{Hash, Hasher};
-use core::iter::{FromIterator, FusedIterator};
+use core::iter::FusedIterator;
 use core::marker::PhantomData;
 use core::mem;
 use core::ptr::NonNull;
@@ -130,7 +130,6 @@ impl<T: fmt::Debug> fmt::Debug for IterMut<'_, T> {
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: LinkedList::into_iter
-/// [`IntoIterator`]: core::iter::IntoIterator
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<T> {
diff --git a/library/alloc/src/collections/vec_deque/into_iter.rs b/library/alloc/src/collections/vec_deque/into_iter.rs
index e2b40f7912e..d9e274df0f5 100644
--- a/library/alloc/src/collections/vec_deque/into_iter.rs
+++ b/library/alloc/src/collections/vec_deque/into_iter.rs
@@ -12,7 +12,6 @@ use super::VecDeque;
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: VecDeque::into_iter
-/// [`IntoIterator`]: core::iter::IntoIterator
 #[derive(Clone)]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct IntoIter<
diff --git a/library/alloc/src/collections/vec_deque/mod.rs b/library/alloc/src/collections/vec_deque/mod.rs
index 05dbcdc904e..8916b42eda0 100644
--- a/library/alloc/src/collections/vec_deque/mod.rs
+++ b/library/alloc/src/collections/vec_deque/mod.rs
@@ -10,7 +10,7 @@
 use core::cmp::{self, Ordering};
 use core::fmt;
 use core::hash::{Hash, Hasher};
-use core::iter::{repeat_n, repeat_with, ByRefSized, FromIterator};
+use core::iter::{repeat_n, repeat_with, ByRefSized};
 use core::mem::{ManuallyDrop, SizedTypeProperties};
 use core::ops::{Index, IndexMut, Range, RangeBounds};
 use core::ptr;
diff --git a/library/alloc/src/raw_vec.rs b/library/alloc/src/raw_vec.rs
index 3751f2a2454..dfd30d99cf0 100644
--- a/library/alloc/src/raw_vec.rs
+++ b/library/alloc/src/raw_vec.rs
@@ -4,7 +4,6 @@ use core::alloc::LayoutError;
 use core::cmp;
 use core::intrinsics;
 use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
-use core::ops::Drop;
 use core::ptr::{self, NonNull, Unique};
 use core::slice;
 
diff --git a/library/alloc/src/rc.rs b/library/alloc/src/rc.rs
index 1e9cf404f77..cf93a40496f 100644
--- a/library/alloc/src/rc.rs
+++ b/library/alloc/src/rc.rs
@@ -15,7 +15,7 @@
 //!
 //! [`Rc`] uses non-atomic reference counting. This means that overhead is very
 //! low, but an [`Rc`] cannot be sent between threads, and consequently [`Rc`]
-//! does not implement [`Send`][send]. As a result, the Rust compiler
+//! does not implement [`Send`]. As a result, the Rust compiler
 //! will check *at compile time* that you are not sending [`Rc`]s between
 //! threads. If you need multi-threaded, atomic reference counting, use
 //! [`sync::Arc`][arc].
@@ -232,7 +232,6 @@
 //! [clone]: Clone::clone
 //! [`Cell`]: core::cell::Cell
 //! [`RefCell`]: core::cell::RefCell
-//! [send]: core::marker::Send
 //! [arc]: crate::sync::Arc
 //! [`Deref`]: core::ops::Deref
 //! [downgrade]: Rc::downgrade
@@ -251,13 +250,12 @@ use core::any::Any;
 use core::borrow;
 use core::cell::Cell;
 use core::cmp::Ordering;
-use core::convert::{From, TryFrom};
 use core::fmt;
 use core::hash::{Hash, Hasher};
 use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
-use core::marker::{self, PhantomData, Unpin, Unsize};
+use core::marker::{PhantomData, Unsize};
 #[cfg(not(no_global_oom_handling))]
 use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw, forget};
@@ -321,7 +319,7 @@ pub struct Rc<T: ?Sized> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> !marker::Send for Rc<T> {}
+impl<T: ?Sized> !Send for Rc<T> {}
 
 // Note that this negative impl isn't strictly necessary for correctness,
 // as `Rc` transitively contains a `Cell`, which is itself `!Sync`.
@@ -329,7 +327,7 @@ impl<T: ?Sized> !marker::Send for Rc<T> {}
 // having an explicit negative impl is nice for documentation purposes
 // and results in nicer error messages.
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<T: ?Sized> !marker::Sync for Rc<T> {}
+impl<T: ?Sized> !Sync for Rc<T> {}
 
 #[stable(feature = "catch_unwind", since = "1.9.0")]
 impl<T: RefUnwindSafe + ?Sized> UnwindSafe for Rc<T> {}
@@ -1060,7 +1058,7 @@ impl<T: ?Sized> Rc<T> {
     #[inline]
     #[stable(feature = "rc_mutate_strong_count", since = "1.53.0")]
     pub unsafe fn decrement_strong_count(ptr: *const T) {
-        unsafe { mem::drop(Rc::from_raw(ptr)) };
+        unsafe { drop(Rc::from_raw(ptr)) };
     }
 
     /// Returns `true` if there are no other `Rc` or [`Weak`] pointers to
@@ -1496,7 +1494,7 @@ impl<T> Rc<[T]> {
     ///
     /// Behavior is undefined should the size be wrong.
     #[cfg(not(no_global_oom_handling))]
-    unsafe fn from_iter_exact(iter: impl iter::Iterator<Item = T>, len: usize) -> Rc<[T]> {
+    unsafe fn from_iter_exact(iter: impl Iterator<Item = T>, len: usize) -> Rc<[T]> {
         // Panic guard while cloning T elements.
         // In the event of a panic, elements that have been written
         // into the new RcBox will be dropped, then the memory freed.
@@ -2088,7 +2086,7 @@ impl<T, const N: usize> TryFrom<Rc<[T]>> for Rc<[T; N]> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "shared_from_iter", since = "1.37.0")]
-impl<T> iter::FromIterator<T> for Rc<[T]> {
+impl<T> FromIterator<T> for Rc<[T]> {
     /// Takes each element in the `Iterator` and collects it into an `Rc<[T]>`.
     ///
     /// # Performance characteristics
@@ -2127,7 +2125,7 @@ impl<T> iter::FromIterator<T> for Rc<[T]> {
     /// let evens: Rc<[u8]> = (0..10).collect(); // Just a single allocation happens here.
     /// # assert_eq!(&*evens, &*(0..10).collect::<Vec<_>>());
     /// ```
-    fn from_iter<I: iter::IntoIterator<Item = T>>(iter: I) -> Self {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
         ToRcSlice::to_rc_slice(iter.into_iter())
     }
 }
@@ -2204,9 +2202,9 @@ pub struct Weak<T: ?Sized> {
 }
 
 #[stable(feature = "rc_weak", since = "1.4.0")]
-impl<T: ?Sized> !marker::Send for Weak<T> {}
+impl<T: ?Sized> !Send for Weak<T> {}
 #[stable(feature = "rc_weak", since = "1.4.0")]
-impl<T: ?Sized> !marker::Sync for Weak<T> {}
+impl<T: ?Sized> !Sync for Weak<T> {}
 
 #[unstable(feature = "coerce_unsized", issue = "18598")]
 impl<T: ?Sized + Unsize<U>, U: ?Sized> CoerceUnsized<Weak<U>> for Weak<T> {}
diff --git a/library/alloc/src/string.rs b/library/alloc/src/string.rs
index c1cd3c74ab6..be41919b9dc 100644
--- a/library/alloc/src/string.rs
+++ b/library/alloc/src/string.rs
@@ -45,9 +45,9 @@
 use core::error::Error;
 use core::fmt;
 use core::hash;
-use core::iter::FusedIterator;
 #[cfg(not(no_global_oom_handling))]
-use core::iter::{from_fn, FromIterator};
+use core::iter::from_fn;
+use core::iter::FusedIterator;
 #[cfg(not(no_global_oom_handling))]
 use core::ops::Add;
 #[cfg(not(no_global_oom_handling))]
diff --git a/library/alloc/src/sync.rs b/library/alloc/src/sync.rs
index 150924851d2..5bfe537bc83 100644
--- a/library/alloc/src/sync.rs
+++ b/library/alloc/src/sync.rs
@@ -11,14 +11,13 @@
 use core::any::Any;
 use core::borrow;
 use core::cmp::Ordering;
-use core::convert::{From, TryFrom};
 use core::fmt;
 use core::hash::{Hash, Hasher};
 use core::hint;
 use core::intrinsics::abort;
 #[cfg(not(no_global_oom_handling))]
 use core::iter;
-use core::marker::{PhantomData, Unpin, Unsize};
+use core::marker::{PhantomData, Unsize};
 #[cfg(not(no_global_oom_handling))]
 use core::mem::size_of_val;
 use core::mem::{self, align_of_val_raw};
@@ -188,8 +187,6 @@ macro_rules! acquire {
 /// [mutex]: ../../std/sync/struct.Mutex.html
 /// [rwlock]: ../../std/sync/struct.RwLock.html
 /// [atomic]: core::sync::atomic
-/// [`Send`]: core::marker::Send
-/// [`Sync`]: core::marker::Sync
 /// [deref]: core::ops::Deref
 /// [downgrade]: Arc::downgrade
 /// [upgrade]: Weak::upgrade
@@ -1241,7 +1238,7 @@ impl<T: ?Sized> Arc<T> {
     #[inline]
     #[stable(feature = "arc_mutate_strong_count", since = "1.51.0")]
     pub unsafe fn decrement_strong_count(ptr: *const T) {
-        unsafe { mem::drop(Arc::from_raw(ptr)) };
+        unsafe { drop(Arc::from_raw(ptr)) };
     }
 
     #[inline]
@@ -1404,7 +1401,7 @@ impl<T> Arc<[T]> {
     ///
     /// Behavior is undefined should the size be wrong.
     #[cfg(not(no_global_oom_handling))]
-    unsafe fn from_iter_exact(iter: impl iter::Iterator<Item = T>, len: usize) -> Arc<[T]> {
+    unsafe fn from_iter_exact(iter: impl Iterator<Item = T>, len: usize) -> Arc<[T]> {
         // Panic guard while cloning T elements.
         // In the event of a panic, elements that have been written
         // into the new ArcInner will be dropped, then the memory freed.
@@ -2818,7 +2815,7 @@ impl<T, const N: usize> TryFrom<Arc<[T]>> for Arc<[T; N]> {
 
 #[cfg(not(no_global_oom_handling))]
 #[stable(feature = "shared_from_iter", since = "1.37.0")]
-impl<T> iter::FromIterator<T> for Arc<[T]> {
+impl<T> FromIterator<T> for Arc<[T]> {
     /// Takes each element in the `Iterator` and collects it into an `Arc<[T]>`.
     ///
     /// # Performance characteristics
@@ -2857,7 +2854,7 @@ impl<T> iter::FromIterator<T> for Arc<[T]> {
     /// let evens: Arc<[u8]> = (0..10).collect(); // Just a single allocation happens here.
     /// # assert_eq!(&*evens, &*(0..10).collect::<Vec<_>>());
     /// ```
-    fn from_iter<I: iter::IntoIterator<Item = T>>(iter: I) -> Self {
+    fn from_iter<I: IntoIterator<Item = T>>(iter: I) -> Self {
         ToArcSlice::to_arc_slice(iter.into_iter())
     }
 }
diff --git a/library/alloc/src/vec/cow.rs b/library/alloc/src/vec/cow.rs
index 64943a273c9..2c799605b7b 100644
--- a/library/alloc/src/vec/cow.rs
+++ b/library/alloc/src/vec/cow.rs
@@ -1,5 +1,4 @@
 use crate::borrow::Cow;
-use core::iter::FromIterator;
 
 use super::Vec;
 
diff --git a/library/alloc/src/vec/into_iter.rs b/library/alloc/src/vec/into_iter.rs
index 6a05f70e437..02faf8e6389 100644
--- a/library/alloc/src/vec/into_iter.rs
+++ b/library/alloc/src/vec/into_iter.rs
@@ -108,7 +108,7 @@ impl<T, A: Allocator> IntoIter<T, A> {
     /// ```
     /// # let mut into_iter = Vec::<u8>::with_capacity(10).into_iter();
     /// let mut into_iter = std::mem::replace(&mut into_iter, Vec::new().into_iter());
-    /// (&mut into_iter).for_each(core::mem::drop);
+    /// (&mut into_iter).for_each(drop);
     /// std::mem::forget(into_iter);
     /// ```
     ///
diff --git a/library/alloc/src/vec/mod.rs b/library/alloc/src/vec/mod.rs
index 9f0111db452..3736a6e0b0e 100644
--- a/library/alloc/src/vec/mod.rs
+++ b/library/alloc/src/vec/mod.rs
@@ -56,12 +56,9 @@
 #[cfg(not(no_global_oom_handling))]
 use core::cmp;
 use core::cmp::Ordering;
-use core::convert::TryFrom;
 use core::fmt;
 use core::hash::{Hash, Hasher};
 use core::iter;
-#[cfg(not(no_global_oom_handling))]
-use core::iter::FromIterator;
 use core::marker::PhantomData;
 use core::mem::{self, ManuallyDrop, MaybeUninit, SizedTypeProperties};
 use core::ops::{self, Index, IndexMut, Range, RangeBounds};
@@ -2990,7 +2987,7 @@ impl<'a, T: Copy + 'a, A: Allocator + 'a> Extend<&'a T> for Vec<T, A> {
     }
 }
 
-/// Implements comparison of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
+/// Implements comparison of vectors, [lexicographically](Ord#lexicographical-comparison).
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> {
     #[inline]
@@ -3002,7 +2999,7 @@ impl<T: PartialOrd, A: Allocator> PartialOrd for Vec<T, A> {
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Eq, A: Allocator> Eq for Vec<T, A> {}
 
-/// Implements ordering of vectors, [lexicographically](core::cmp::Ord#lexicographical-comparison).
+/// Implements ordering of vectors, [lexicographically](Ord#lexicographical-comparison).
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<T: Ord, A: Allocator> Ord for Vec<T, A> {
     #[inline]
diff --git a/library/core/src/iter/sources/repeat_with.rs b/library/core/src/iter/sources/repeat_with.rs
index 3f34105a3e0..d3cd74a4483 100644
--- a/library/core/src/iter/sources/repeat_with.rs
+++ b/library/core/src/iter/sources/repeat_with.rs
@@ -19,7 +19,6 @@ use crate::ops::Try;
 /// please open a GitHub issue explaining your use case.
 ///
 /// [`repeat()`]: crate::iter::repeat
-/// [`DoubleEndedIterator`]: crate::iter::DoubleEndedIterator
 ///
 /// # Examples
 ///
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index f3d1e45f4fb..02877604248 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -764,7 +764,6 @@ pub trait Iterator {
     /// more idiomatic to use [`for`] than `map()`.
     ///
     /// [`for`]: ../../book/ch03-05-control-flow.html#looping-through-a-collection-with-for
-    /// [`FnMut`]: crate::ops::FnMut
     ///
     /// # Examples
     ///
diff --git a/library/core/src/net/parser.rs b/library/core/src/net/parser.rs
index a08d2792d04..b9a1924d668 100644
--- a/library/core/src/net/parser.rs
+++ b/library/core/src/net/parser.rs
@@ -9,7 +9,7 @@ use crate::fmt;
 use crate::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr, SocketAddrV4, SocketAddrV6};
 use crate::str::FromStr;
 
-trait ReadNumberHelper: crate::marker::Sized {
+trait ReadNumberHelper: Sized {
     const ZERO: Self;
     fn checked_mul(&self, other: u32) -> Option<Self>;
     fn checked_add(&self, other: u32) -> Option<Self>;
diff --git a/library/core/src/primitive_docs.rs b/library/core/src/primitive_docs.rs
index 51e6947a9c2..3df990e5dd9 100644
--- a/library/core/src/primitive_docs.rs
+++ b/library/core/src/primitive_docs.rs
@@ -577,7 +577,6 @@ impl Copy for () {
 /// [`is_null`]: pointer::is_null
 /// [`offset`]: pointer::offset
 #[doc = concat!("[`into_raw`]: ", include_str!("../primitive_docs/box_into_raw.md"))]
-/// [`drop`]: mem::drop
 /// [`write`]: ptr::write
 #[stable(feature = "rust1", since = "1.0.0")]
 mod prim_pointer {}
@@ -1026,7 +1025,6 @@ mod prim_str {}
 /// * [`UnwindSafe`]
 /// * [`RefUnwindSafe`]
 ///
-/// [`Unpin`]: marker::Unpin
 /// [`UnwindSafe`]: panic::UnwindSafe
 /// [`RefUnwindSafe`]: panic::RefUnwindSafe
 ///
@@ -1405,10 +1403,6 @@ mod prim_ref {}
 ///
 /// *See also the traits [`Fn`], [`FnMut`], and [`FnOnce`].*
 ///
-/// [`Fn`]: ops::Fn
-/// [`FnMut`]: ops::FnMut
-/// [`FnOnce`]: ops::FnOnce
-///
 /// Function pointers are pointers that point to *code*, not data. They can be called
 /// just like functions. Like references, function pointers are, among other things, assumed to
 /// not be null, so if you want to pass a function pointer over FFI and be able to accommodate null
diff --git a/library/core/src/sync/exclusive.rs b/library/core/src/sync/exclusive.rs
index 301ad41c966..3f3e19c55d4 100644
--- a/library/core/src/sync/exclusive.rs
+++ b/library/core/src/sync/exclusive.rs
@@ -69,9 +69,6 @@ use core::task::{Context, Poll};
 /// for any value. This is a parallel with the fact that
 /// `&` and `&mut` references together can be thought of as a _compile-time_
 /// version of a read-write lock.
-///
-///
-/// [`Sync`]: core::marker::Sync
 #[unstable(feature = "exclusive_wrapper", issue = "98407")]
 #[doc(alias = "SyncWrapper")]
 #[doc(alias = "SyncCell")]
diff --git a/library/portable-simd/crates/core_simd/src/masks/full_masks.rs b/library/portable-simd/crates/core_simd/src/masks/full_masks.rs
index adf0fcbeae2..b5ba198e504 100644
--- a/library/portable-simd/crates/core_simd/src/masks/full_masks.rs
+++ b/library/portable-simd/crates/core_simd/src/masks/full_masks.rs
@@ -257,7 +257,7 @@ where
     }
 }
 
-impl<T, const LANES: usize> core::convert::From<Mask<T, LANES>> for Simd<T, LANES>
+impl<T, const LANES: usize> From<Mask<T, LANES>> for Simd<T, LANES>
 where
     T: MaskElement,
     LaneCount<LANES>: SupportedLaneCount,
diff --git a/library/proc_macro/src/bridge/fxhash.rs b/library/proc_macro/src/bridge/fxhash.rs
index 17bd0a1b336..f4e90544197 100644
--- a/library/proc_macro/src/bridge/fxhash.rs
+++ b/library/proc_macro/src/bridge/fxhash.rs
@@ -5,8 +5,6 @@
 //! on the `rustc_hash` crate.
 
 use std::collections::HashMap;
-use std::convert::TryInto;
-use std::default::Default;
 use std::hash::BuildHasherDefault;
 use std::hash::Hasher;
 use std::mem::size_of;
diff --git a/library/proc_macro/src/lib.rs b/library/proc_macro/src/lib.rs
index 938935771d6..9d081c8b842 100644
--- a/library/proc_macro/src/lib.rs
+++ b/library/proc_macro/src/lib.rs
@@ -47,7 +47,7 @@ use std::cmp::Ordering;
 use std::ops::RangeBounds;
 use std::path::PathBuf;
 use std::str::FromStr;
-use std::{error, fmt, iter};
+use std::{error, fmt};
 
 /// Determines whether proc_macro has been made accessible to the currently
 /// running program.
@@ -310,7 +310,7 @@ impl ConcatStreamsHelper {
 
 /// Collects a number of token trees into a single stream.
 #[stable(feature = "proc_macro_lib2", since = "1.29.0")]
-impl iter::FromIterator<TokenTree> for TokenStream {
+impl FromIterator<TokenTree> for TokenStream {
     fn from_iter<I: IntoIterator<Item = TokenTree>>(trees: I) -> Self {
         let iter = trees.into_iter();
         let mut builder = ConcatTreesHelper::new(iter.size_hint().0);
@@ -322,7 +322,7 @@ impl iter::FromIterator<TokenTree> for TokenStream {
 /// A "flattening" operation on token streams, collects token trees
 /// from multiple token streams into a single stream.
 #[stable(feature = "proc_macro_lib", since = "1.15.0")]
-impl iter::FromIterator<TokenStream> for TokenStream {
+impl FromIterator<TokenStream> for TokenStream {
     fn from_iter<I: IntoIterator<Item = TokenStream>>(streams: I) -> Self {
         let iter = streams.into_iter();
         let mut builder = ConcatStreamsHelper::new(iter.size_hint().0);
diff --git a/library/std/src/collections/hash/map.rs b/library/std/src/collections/hash/map.rs
index 742c4cc7c55..3afc8287ecc 100644
--- a/library/std/src/collections/hash/map.rs
+++ b/library/std/src/collections/hash/map.rs
@@ -1446,7 +1446,6 @@ impl<'a, K, V> IterMut<'a, K, V> {
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: IntoIterator::into_iter
-/// [`IntoIterator`]: crate::iter::IntoIterator
 ///
 /// # Example
 ///
diff --git a/library/std/src/collections/hash/set.rs b/library/std/src/collections/hash/set.rs
index 837a18bff60..ac906e682d5 100644
--- a/library/std/src/collections/hash/set.rs
+++ b/library/std/src/collections/hash/set.rs
@@ -1272,7 +1272,6 @@ pub struct Iter<'a, K: 'a> {
 /// (provided by the [`IntoIterator`] trait). See its documentation for more.
 ///
 /// [`into_iter`]: IntoIterator::into_iter
-/// [`IntoIterator`]: crate::iter::IntoIterator
 ///
 /// # Examples
 ///
diff --git a/library/std/src/collections/mod.rs b/library/std/src/collections/mod.rs
index 575f56ff4df..49d3b7a1f61 100644
--- a/library/std/src/collections/mod.rs
+++ b/library/std/src/collections/mod.rs
@@ -395,8 +395,6 @@
 //! // ...but the key hasn't changed. b is still "baz", not "xyz".
 //! assert_eq!(map.keys().next().unwrap().b, "baz");
 //! ```
-//!
-//! [IntoIterator]: crate::iter::IntoIterator "iter::IntoIterator"
 
 #![stable(feature = "rust1", since = "1.0.0")]
 
diff --git a/library/std/src/ffi/os_str.rs b/library/std/src/ffi/os_str.rs
index 80ed34157e6..5c0541d3caf 100644
--- a/library/std/src/ffi/os_str.rs
+++ b/library/std/src/ffi/os_str.rs
@@ -6,7 +6,6 @@ use crate::cmp;
 use crate::collections::TryReserveError;
 use crate::fmt;
 use crate::hash::{Hash, Hasher};
-use crate::iter::Extend;
 use crate::ops;
 use crate::rc::Rc;
 use crate::str::FromStr;
diff --git a/library/std/src/io/error.rs b/library/std/src/io/error.rs
index 1cedd6eedfa..34c0ce9dcf8 100644
--- a/library/std/src/io/error.rs
+++ b/library/std/src/io/error.rs
@@ -11,7 +11,6 @@ mod repr_unpacked;
 #[cfg(not(target_pointer_width = "64"))]
 use repr_unpacked::Repr;
 
-use crate::convert::From;
 use crate::error;
 use crate::fmt;
 use crate::result;
diff --git a/library/std/src/keyword_docs.rs b/library/std/src/keyword_docs.rs
index 203c490fa29..43842bee992 100644
--- a/library/std/src/keyword_docs.rs
+++ b/library/std/src/keyword_docs.rs
@@ -1678,7 +1678,7 @@ mod super_keyword {}
 /// below `Iterator` is a **supertrait** and `ThreeIterator` is a **subtrait**:
 ///
 /// ```rust
-/// trait ThreeIterator: std::iter::Iterator {
+/// trait ThreeIterator: Iterator {
 ///     fn next_three(&mut self) -> Option<[Self::Item; 3]>;
 /// }
 /// ```
diff --git a/library/std/src/path.rs b/library/std/src/path.rs
index dbc18f7827e..8014ba992ea 100644
--- a/library/std/src/path.rs
+++ b/library/std/src/path.rs
@@ -78,7 +78,7 @@ use crate::fmt;
 use crate::fs;
 use crate::hash::{Hash, Hasher};
 use crate::io;
-use crate::iter::{self, FusedIterator};
+use crate::iter::FusedIterator;
 use crate::ops::{self, Deref};
 use crate::rc::Rc;
 use crate::str::FromStr;
@@ -450,26 +450,26 @@ impl<'a> PrefixComponent<'a> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> cmp::PartialEq for PrefixComponent<'a> {
+impl<'a> PartialEq for PrefixComponent<'a> {
     #[inline]
     fn eq(&self, other: &PrefixComponent<'a>) -> bool {
-        cmp::PartialEq::eq(&self.parsed, &other.parsed)
+        self.parsed == other.parsed
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> cmp::PartialOrd for PrefixComponent<'a> {
+impl<'a> PartialOrd for PrefixComponent<'a> {
     #[inline]
     fn partial_cmp(&self, other: &PrefixComponent<'a>) -> Option<cmp::Ordering> {
-        cmp::PartialOrd::partial_cmp(&self.parsed, &other.parsed)
+        PartialOrd::partial_cmp(&self.parsed, &other.parsed)
     }
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Ord for PrefixComponent<'_> {
+impl Ord for PrefixComponent<'_> {
     #[inline]
     fn cmp(&self, other: &Self) -> cmp::Ordering {
-        cmp::Ord::cmp(&self.parsed, &other.parsed)
+        Ord::cmp(&self.parsed, &other.parsed)
     }
 }
 
@@ -988,7 +988,7 @@ impl<'a> DoubleEndedIterator for Components<'a> {
 impl FusedIterator for Components<'_> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> cmp::PartialEq for Components<'a> {
+impl<'a> PartialEq for Components<'a> {
     #[inline]
     fn eq(&self, other: &Components<'a>) -> bool {
         let Components { path: _, front: _, back: _, has_physical_root: _, prefix: _ } = self;
@@ -1015,10 +1015,10 @@ impl<'a> cmp::PartialEq for Components<'a> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Eq for Components<'_> {}
+impl Eq for Components<'_> {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<'a> cmp::PartialOrd for Components<'a> {
+impl<'a> PartialOrd for Components<'a> {
     #[inline]
     fn partial_cmp(&self, other: &Components<'a>) -> Option<cmp::Ordering> {
         Some(compare_components(self.clone(), other.clone()))
@@ -1026,7 +1026,7 @@ impl<'a> cmp::PartialOrd for Components<'a> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Ord for Components<'_> {
+impl Ord for Components<'_> {
     #[inline]
     fn cmp(&self, other: &Self) -> cmp::Ordering {
         compare_components(self.clone(), other.clone())
@@ -1741,7 +1741,7 @@ impl FromStr for PathBuf {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<P: AsRef<Path>> iter::FromIterator<P> for PathBuf {
+impl<P: AsRef<Path>> FromIterator<P> for PathBuf {
     fn from_iter<I: IntoIterator<Item = P>>(iter: I) -> PathBuf {
         let mut buf = PathBuf::new();
         buf.extend(iter);
@@ -1750,7 +1750,7 @@ impl<P: AsRef<Path>> iter::FromIterator<P> for PathBuf {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl<P: AsRef<Path>> iter::Extend<P> for PathBuf {
+impl<P: AsRef<Path>> Extend<P> for PathBuf {
     fn extend<I: IntoIterator<Item = P>>(&mut self, iter: I) {
         iter.into_iter().for_each(move |p| self.push(p.as_ref()));
     }
@@ -1904,7 +1904,7 @@ impl ToOwned for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::PartialEq for PathBuf {
+impl PartialEq for PathBuf {
     #[inline]
     fn eq(&self, other: &PathBuf) -> bool {
         self.components() == other.components()
@@ -1919,10 +1919,10 @@ impl Hash for PathBuf {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Eq for PathBuf {}
+impl Eq for PathBuf {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::PartialOrd for PathBuf {
+impl PartialOrd for PathBuf {
     #[inline]
     fn partial_cmp(&self, other: &PathBuf) -> Option<cmp::Ordering> {
         Some(compare_components(self.components(), other.components()))
@@ -1930,7 +1930,7 @@ impl cmp::PartialOrd for PathBuf {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Ord for PathBuf {
+impl Ord for PathBuf {
     #[inline]
     fn cmp(&self, other: &PathBuf) -> cmp::Ordering {
         compare_components(self.components(), other.components())
@@ -3025,7 +3025,7 @@ impl fmt::Display for Display<'_> {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::PartialEq for Path {
+impl PartialEq for Path {
     #[inline]
     fn eq(&self, other: &Path) -> bool {
         self.components() == other.components()
@@ -3084,10 +3084,10 @@ impl Hash for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Eq for Path {}
+impl Eq for Path {}
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::PartialOrd for Path {
+impl PartialOrd for Path {
     #[inline]
     fn partial_cmp(&self, other: &Path) -> Option<cmp::Ordering> {
         Some(compare_components(self.components(), other.components()))
@@ -3095,7 +3095,7 @@ impl cmp::PartialOrd for Path {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
-impl cmp::Ord for Path {
+impl Ord for Path {
     #[inline]
     fn cmp(&self, other: &Path) -> cmp::Ordering {
         compare_components(self.components(), other.components())
diff --git a/library/std/src/prelude/mod.rs b/library/std/src/prelude/mod.rs
index c314bbbb68e..1b29c887d21 100644
--- a/library/std/src/prelude/mod.rs
+++ b/library/std/src/prelude/mod.rs
@@ -34,7 +34,7 @@
 //!   marker traits that indicate fundamental properties of types.
 //! * <code>[std::ops]::{[Drop], [Fn], [FnMut], [FnOnce]}</code>, various
 //!   operations for both destructors and overloading `()`.
-//! * <code>[std::mem]::[drop][mem::drop]</code>, a convenience function for explicitly
+//! * <code>[std::mem]::[drop]</code>, a convenience function for explicitly
 //!   dropping a value.
 //! * <code>[std::boxed]::[Box]</code>, a way to allocate values on the heap.
 //! * <code>[std::borrow]::[ToOwned]</code>, the conversion trait that defines
@@ -66,7 +66,6 @@
 //! * <code>[std::convert]::{[TryFrom], [TryInto]}</code>,
 //! * <code>[std::iter]::[FromIterator]</code>.
 //!
-//! [mem::drop]: crate::mem::drop
 //! [std::borrow]: crate::borrow
 //! [std::boxed]: crate::boxed
 //! [std::clone]: crate::clone
@@ -86,9 +85,6 @@
 //! [std::slice]: crate::slice
 //! [std::string]: crate::string
 //! [std::vec]: mod@crate::vec
-//! [TryFrom]: crate::convert::TryFrom
-//! [TryInto]: crate::convert::TryInto
-//! [FromIterator]: crate::iter::FromIterator
 //! [`to_owned`]: crate::borrow::ToOwned::to_owned
 //! [book-closures]: ../../book/ch13-01-closures.html
 //! [book-dtor]: ../../book/ch15-03-drop.html
diff --git a/library/std/src/primitive_docs.rs b/library/std/src/primitive_docs.rs
index 51e6947a9c2..3df990e5dd9 100644
--- a/library/std/src/primitive_docs.rs
+++ b/library/std/src/primitive_docs.rs
@@ -577,7 +577,6 @@ impl Copy for () {
 /// [`is_null`]: pointer::is_null
 /// [`offset`]: pointer::offset
 #[doc = concat!("[`into_raw`]: ", include_str!("../primitive_docs/box_into_raw.md"))]
-/// [`drop`]: mem::drop
 /// [`write`]: ptr::write
 #[stable(feature = "rust1", since = "1.0.0")]
 mod prim_pointer {}
@@ -1026,7 +1025,6 @@ mod prim_str {}
 /// * [`UnwindSafe`]
 /// * [`RefUnwindSafe`]
 ///
-/// [`Unpin`]: marker::Unpin
 /// [`UnwindSafe`]: panic::UnwindSafe
 /// [`RefUnwindSafe`]: panic::RefUnwindSafe
 ///
@@ -1405,10 +1403,6 @@ mod prim_ref {}
 ///
 /// *See also the traits [`Fn`], [`FnMut`], and [`FnOnce`].*
 ///
-/// [`Fn`]: ops::Fn
-/// [`FnMut`]: ops::FnMut
-/// [`FnOnce`]: ops::FnOnce
-///
 /// Function pointers are pointers that point to *code*, not data. They can be called
 /// just like functions. Like references, function pointers are, among other things, assumed to
 /// not be null, so if you want to pass a function pointer over FFI and be able to accommodate null
diff --git a/library/std/src/sys/sgx/abi/usercalls/alloc.rs b/library/std/src/sys/sgx/abi/usercalls/alloc.rs
index 0d934318c22..01505e94487 100644
--- a/library/std/src/sys/sgx/abi/usercalls/alloc.rs
+++ b/library/std/src/sys/sgx/abi/usercalls/alloc.rs
@@ -3,7 +3,6 @@
 use crate::arch::asm;
 use crate::cell::UnsafeCell;
 use crate::cmp;
-use crate::convert::TryInto;
 use crate::mem;
 use crate::ops::{CoerceUnsized, Deref, DerefMut, Index, IndexMut};
 use crate::ptr::{self, NonNull};
diff --git a/library/std/src/sys/unix/futex.rs b/library/std/src/sys/unix/futex.rs
index 8d5b540212a..d310be6c7a1 100644
--- a/library/std/src/sys/unix/futex.rs
+++ b/library/std/src/sys/unix/futex.rs
@@ -273,8 +273,6 @@ pub mod zircon {
 
 #[cfg(target_os = "fuchsia")]
 pub fn futex_wait(futex: &AtomicU32, expected: u32, timeout: Option<Duration>) -> bool {
-    use crate::convert::TryFrom;
-
     // Sleep forever if the timeout is longer than fits in a i64.
     let deadline = timeout
         .and_then(|d| {
diff --git a/library/std/src/sys/unix/os.rs b/library/std/src/sys/unix/os.rs
index 1c44058aff7..a345af76fa2 100644
--- a/library/std/src/sys/unix/os.rs
+++ b/library/std/src/sys/unix/os.rs
@@ -7,7 +7,6 @@ mod tests;
 
 use crate::os::unix::prelude::*;
 
-use crate::convert::TryFrom;
 use crate::error::Error as StdError;
 use crate::ffi::{CStr, CString, OsStr, OsString};
 use crate::fmt;
diff --git a/library/std/src/sys/unix/process/process_fuchsia.rs b/library/std/src/sys/unix/process/process_fuchsia.rs
index d4c7e58b34d..e45c380a0bb 100644
--- a/library/std/src/sys/unix/process/process_fuchsia.rs
+++ b/library/std/src/sys/unix/process/process_fuchsia.rs
@@ -166,7 +166,6 @@ impl Process {
     }
 
     pub fn wait(&mut self) -> io::Result<ExitStatus> {
-        use crate::default::Default;
         use crate::sys::process::zircon::*;
 
         let mut proc_info: zx_info_process_t = Default::default();
@@ -199,7 +198,6 @@ impl Process {
     }
 
     pub fn try_wait(&mut self) -> io::Result<Option<ExitStatus>> {
-        use crate::default::Default;
         use crate::sys::process::zircon::*;
 
         let mut proc_info: zx_info_process_t = Default::default();
diff --git a/library/std/src/sys_common/net.rs b/library/std/src/sys_common/net.rs
index eb427dbda23..cb24caa1e8a 100644
--- a/library/std/src/sys_common/net.rs
+++ b/library/std/src/sys_common/net.rs
@@ -2,7 +2,6 @@
 mod tests;
 
 use crate::cmp;
-use crate::convert::{TryFrom, TryInto};
 use crate::fmt;
 use crate::io::{self, BorrowedCursor, ErrorKind, IoSlice, IoSliceMut};
 use crate::mem;
diff --git a/src/bootstrap/cache.rs b/src/bootstrap/cache.rs
index 05f25af68ea..5376c4ec9c3 100644
--- a/src/bootstrap/cache.rs
+++ b/src/bootstrap/cache.rs
@@ -1,9 +1,8 @@
 use std::any::{Any, TypeId};
 use std::borrow::Borrow;
 use std::cell::RefCell;
-use std::cmp::{Ord, Ordering, PartialOrd};
+use std::cmp::Ordering;
 use std::collections::HashMap;
-use std::convert::AsRef;
 use std::fmt;
 use std::hash::{Hash, Hasher};
 use std::marker::PhantomData;
diff --git a/src/librustdoc/clean/mod.rs b/src/librustdoc/clean/mod.rs
index b3df12a9df1..02cec16b35c 100644
--- a/src/librustdoc/clean/mod.rs
+++ b/src/librustdoc/clean/mod.rs
@@ -35,7 +35,6 @@ use rustc_span::{self, ExpnKind};
 use std::borrow::Cow;
 use std::collections::hash_map::Entry;
 use std::collections::BTreeMap;
-use std::default::Default;
 use std::hash::Hash;
 use std::mem;
 use thin_vec::ThinVec;
diff --git a/src/librustdoc/clean/types.rs b/src/librustdoc/clean/types.rs
index e34ece9264c..6d2ce9e2833 100644
--- a/src/librustdoc/clean/types.rs
+++ b/src/librustdoc/clean/types.rs
@@ -1,6 +1,5 @@
 use std::borrow::Cow;
 use std::cell::RefCell;
-use std::default::Default;
 use std::hash::Hash;
 use std::path::PathBuf;
 use std::rc::Rc;
@@ -980,7 +979,7 @@ pub(crate) trait NestedAttributesExt {
     /// Returns `true` if the attribute list contains a specific `word`
     fn has_word(self, word: Symbol) -> bool
     where
-        Self: std::marker::Sized,
+        Self: Sized,
     {
         <Self as NestedAttributesExt>::get_word_attr(self, word).is_some()
     }
diff --git a/src/librustdoc/config.rs b/src/librustdoc/config.rs
index c848089dad6..b97bb190dd8 100644
--- a/src/librustdoc/config.rs
+++ b/src/librustdoc/config.rs
@@ -1,5 +1,4 @@
 use std::collections::BTreeMap;
-use std::convert::TryFrom;
 use std::ffi::OsStr;
 use std::fmt;
 use std::path::PathBuf;
diff --git a/src/librustdoc/html/markdown.rs b/src/librustdoc/html/markdown.rs
index fd81a21f5a9..00aadb8e82a 100644
--- a/src/librustdoc/html/markdown.rs
+++ b/src/librustdoc/html/markdown.rs
@@ -36,7 +36,6 @@ use rustc_span::{Span, Symbol};
 use once_cell::sync::Lazy;
 use std::borrow::Cow;
 use std::collections::VecDeque;
-use std::default::Default;
 use std::fmt::Write;
 use std::ops::{ControlFlow, Range};
 use std::str;
diff --git a/src/librustdoc/html/render/mod.rs b/src/librustdoc/html/render/mod.rs
index 1e3cd266850..463184acaa1 100644
--- a/src/librustdoc/html/render/mod.rs
+++ b/src/librustdoc/html/render/mod.rs
@@ -38,7 +38,6 @@ pub(crate) use self::context::*;
 pub(crate) use self::span_map::{collect_spans_and_sources, LinkFromSrc};
 
 use std::collections::VecDeque;
-use std::default::Default;
 use std::fmt::{self, Write};
 use std::fs;
 use std::iter::Peekable;
diff --git a/src/librustdoc/html/render/search_index.rs b/src/librustdoc/html/render/search_index.rs
index 08a0e1c377e..f5b4a3f5abd 100644
--- a/src/librustdoc/html/render/search_index.rs
+++ b/src/librustdoc/html/render/search_index.rs
@@ -59,7 +59,7 @@ pub(crate) fn build_index<'tcx>(
         // `sort_unstable_by_key` produces lifetime errors
         let k1 = (&k1.path, k1.name.as_str(), &k1.ty, &k1.parent);
         let k2 = (&k2.path, k2.name.as_str(), &k2.ty, &k2.parent);
-        std::cmp::Ord::cmp(&k1, &k2)
+        Ord::cmp(&k1, &k2)
     });
 
     // Set up alias indexes.
diff --git a/src/librustdoc/json/conversions.rs b/src/librustdoc/json/conversions.rs
index c39caf73a93..cd6509607d5 100644
--- a/src/librustdoc/json/conversions.rs
+++ b/src/librustdoc/json/conversions.rs
@@ -4,7 +4,6 @@
 
 #![allow(rustc::default_hash_types)]
 
-use std::convert::From;
 use std::fmt;
 
 use rustc_ast::ast;
diff --git a/src/librustdoc/lib.rs b/src/librustdoc/lib.rs
index 79f53ee57cc..9fd130c4717 100644
--- a/src/librustdoc/lib.rs
+++ b/src/librustdoc/lib.rs
@@ -69,7 +69,6 @@ extern crate test;
 #[cfg(feature = "jemalloc")]
 extern crate jemalloc_sys;
 
-use std::default::Default;
 use std::env::{self, VarError};
 use std::io::{self, IsTerminal};
 use std::process;
diff --git a/src/tools/bump-stage0/src/main.rs b/src/tools/bump-stage0/src/main.rs
index f530a4d73d3..b007f9a22c3 100644
--- a/src/tools/bump-stage0/src/main.rs
+++ b/src/tools/bump-stage0/src/main.rs
@@ -2,7 +2,6 @@ use anyhow::{Context, Error};
 use curl::easy::Easy;
 use indexmap::IndexMap;
 use std::collections::HashMap;
-use std::convert::TryInto;
 
 const PATH: &str = "src/stage0.json";
 const COMPILER_COMPONENTS: &[&str] = &["rustc", "rust-std", "cargo"];
diff --git a/src/tools/tidy/src/bins.rs b/src/tools/tidy/src/bins.rs
index 7e5b4d810ba..197e9a9965f 100644
--- a/src/tools/tidy/src/bins.rs
+++ b/src/tools/tidy/src/bins.rs
@@ -57,8 +57,8 @@ mod os_impl {
             match fs::File::create(&path) {
                 Ok(file) => {
                     let exec = is_executable(&path).unwrap_or(false);
-                    std::mem::drop(file);
-                    std::fs::remove_file(&path).expect("Deleted temp file");
+                    drop(file);
+                    fs::remove_file(&path).expect("Deleted temp file");
                     // If the file is executable, then we assume that this
                     // filesystem does not track executability, so skip this check.
                     return if exec { Unsupported } else { Supported };
diff --git a/src/tools/tidy/src/pal.rs b/src/tools/tidy/src/pal.rs
index d40c4ad0711..6fd41e83362 100644
--- a/src/tools/tidy/src/pal.rs
+++ b/src/tools/tidy/src/pal.rs
@@ -31,7 +31,6 @@
 //! this in the long term.
 
 use crate::walk::{filter_dirs, walk};
-use std::iter::Iterator;
 use std::path::Path;
 
 // Paths that may contain platform-specific code.
diff --git a/src/tools/unicode-table-generator/src/raw_emitter.rs b/src/tools/unicode-table-generator/src/raw_emitter.rs
index 890ff986c2b..7547b49ab2a 100644
--- a/src/tools/unicode-table-generator/src/raw_emitter.rs
+++ b/src/tools/unicode-table-generator/src/raw_emitter.rs
@@ -1,6 +1,5 @@
 use crate::fmt_list;
 use std::collections::{BTreeMap, BTreeSet, HashMap};
-use std::convert::TryFrom;
 use std::fmt::{self, Write};
 use std::ops::Range;
 
diff --git a/src/tools/unicode-table-generator/src/skiplist.rs b/src/tools/unicode-table-generator/src/skiplist.rs
index 6e439968c3b..9b613a94c57 100644
--- a/src/tools/unicode-table-generator/src/skiplist.rs
+++ b/src/tools/unicode-table-generator/src/skiplist.rs
@@ -1,6 +1,5 @@
 use crate::fmt_list;
 use crate::raw_emitter::RawEmitter;
-use std::convert::TryInto;
 use std::fmt::Write as _;
 use std::ops::Range;
 
diff --git a/tests/ui/hygiene/panic-location.run.stderr b/tests/ui/hygiene/panic-location.run.stderr
index 1c6a7b02f8e..a7252a40027 100644
--- a/tests/ui/hygiene/panic-location.run.stderr
+++ b/tests/ui/hygiene/panic-location.run.stderr
@@ -1,2 +1,2 @@
-thread 'main' panicked at 'capacity overflow', library/alloc/src/raw_vec.rs:525:5
+thread 'main' panicked at 'capacity overflow', library/alloc/src/raw_vec.rs:524:5
 note: run with `RUST_BACKTRACE=1` environment variable to display a backtrace