diff --git a/library/alloc/Cargo.toml b/library/alloc/Cargo.toml
index b3ff0fd0a313c..265020209eb12 100644
--- a/library/alloc/Cargo.toml
+++ b/library/alloc/Cargo.toml
@@ -6,7 +6,7 @@ repository = "https://github.com/rust-lang/rust.git"
 description = "The Rust core allocation and collections library"
 autotests = false
 autobenches = false
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 core = { path = "../core" }
diff --git a/library/core/Cargo.toml b/library/core/Cargo.toml
index 6f10b9e434290..6bc4ba3cc0edf 100644
--- a/library/core/Cargo.toml
+++ b/library/core/Cargo.toml
@@ -6,7 +6,7 @@ repository = "https://github.com/rust-lang/rust.git"
 description = "The Rust Core Library"
 autotests = false
 autobenches = false
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/library/core/src/array/mod.rs b/library/core/src/array/mod.rs
index 37292bf8e2624..121aa634deb33 100644
--- a/library/core/src/array/mod.rs
+++ b/library/core/src/array/mod.rs
@@ -66,8 +66,6 @@ where
 ///
 /// ```rust
 /// #![feature(array_from_fn)]
-/// # // Apparently these doc tests are still on edition2018
-/// # use std::convert::TryInto;
 ///
 /// let array: Result<[u8; 5], _> = std::array::try_from_fn(|i| i.try_into());
 /// assert_eq!(array, Ok([0, 1, 2, 3, 4]));
diff --git a/library/core/src/convert/mod.rs b/library/core/src/convert/mod.rs
index 1c2e673d60493..d40f69f8b3574 100644
--- a/library/core/src/convert/mod.rs
+++ b/library/core/src/convert/mod.rs
@@ -426,8 +426,6 @@ pub trait TryInto<T>: Sized {
 /// `TryFrom<T>` can be implemented as follows:
 ///
 /// ```
-/// use std::convert::TryFrom;
-///
 /// struct GreaterThanZero(i32);
 ///
 /// impl TryFrom<i32> for GreaterThanZero {
@@ -448,8 +446,6 @@ pub trait TryInto<T>: Sized {
 /// As described, [`i32`] implements `TryFrom<`[`i64`]`>`:
 ///
 /// ```
-/// use std::convert::TryFrom;
-///
 /// let big_number = 1_000_000_000_000i64;
 /// // Silently truncates `big_number`, requires detecting
 /// // and handling the truncation after the fact.
diff --git a/library/core/src/iter/traits/collect.rs b/library/core/src/iter/traits/collect.rs
index 56fad602cf9c8..26c97b8ed785d 100644
--- a/library/core/src/iter/traits/collect.rs
+++ b/library/core/src/iter/traits/collect.rs
@@ -15,8 +15,6 @@
 /// Basic usage:
 ///
 /// ```
-/// use std::iter::FromIterator;
-///
 /// let five_fives = std::iter::repeat(5).take(5);
 ///
 /// let v = Vec::from_iter(five_fives);
@@ -37,8 +35,6 @@
 /// Implementing `FromIterator` for your type:
 ///
 /// ```
-/// use std::iter::FromIterator;
-///
 /// // A sample collection, that's just a wrapper over Vec<T>
 /// #[derive(Debug)]
 /// struct MyCollection(Vec<i32>);
@@ -102,8 +98,6 @@ pub trait FromIterator<A>: Sized {
     /// Basic usage:
     ///
     /// ```
-    /// use std::iter::FromIterator;
-    ///
     /// let five_fives = std::iter::repeat(5).take(5);
     ///
     /// let v = Vec::from_iter(five_fives);
diff --git a/library/core/src/iter/traits/iterator.rs b/library/core/src/iter/traits/iterator.rs
index 9a9a844f41bb4..2049adafa2fed 100644
--- a/library/core/src/iter/traits/iterator.rs
+++ b/library/core/src/iter/traits/iterator.rs
@@ -1155,8 +1155,6 @@ pub trait Iterator {
     /// Stopping after an initial [`None`]:
     ///
     /// ```
-    /// use std::convert::TryFrom;
-    ///
     /// let a = [0, 1, 2, -3, 4, 5, -6];
     ///
     /// let iter = a.iter().map_while(|x| u32::try_from(*x).ok());
@@ -1172,8 +1170,6 @@ pub trait Iterator {
     /// removed:
     ///
     /// ```
-    /// use std::convert::TryFrom;
-    ///
     /// let a = [1, 2, -3, 4];
     /// let mut iter = a.iter();
     ///
diff --git a/library/core/src/num/int_macros.rs b/library/core/src/num/int_macros.rs
index 9a668d34b6278..47641a9ed5405 100644
--- a/library/core/src/num/int_macros.rs
+++ b/library/core/src/num/int_macros.rs
@@ -2602,8 +2602,6 @@ macro_rules! int_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
@@ -2633,8 +2631,6 @@ macro_rules! int_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_le_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
@@ -2675,8 +2671,6 @@ macro_rules! int_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_ne_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
diff --git a/library/core/src/num/uint_macros.rs b/library/core/src/num/uint_macros.rs
index 054b814b7e08e..3aa05a0c6042a 100644
--- a/library/core/src/num/uint_macros.rs
+++ b/library/core/src/num/uint_macros.rs
@@ -2323,8 +2323,6 @@ macro_rules! uint_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_be_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
@@ -2354,8 +2352,6 @@ macro_rules! uint_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_le_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
@@ -2396,8 +2392,6 @@ macro_rules! uint_impl {
         /// When starting from a slice rather than an array, fallible conversion APIs can be used:
         ///
         /// ```
-        /// use std::convert::TryInto;
-        ///
         #[doc = concat!("fn read_ne_", stringify!($SelfT), "(input: &mut &[u8]) -> ", stringify!($SelfT), " {")]
         #[doc = concat!("    let (int_bytes, rest) = input.split_at(std::mem::size_of::<", stringify!($SelfT), ">());")]
         ///     *input = rest;
diff --git a/library/panic_abort/Cargo.toml b/library/panic_abort/Cargo.toml
index 6dec0e674975c..46183d1ad0066 100644
--- a/library/panic_abort/Cargo.toml
+++ b/library/panic_abort/Cargo.toml
@@ -4,7 +4,7 @@ version = "0.0.0"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/rust.git"
 description = "Implementation of Rust panics via process aborts"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/library/panic_unwind/Cargo.toml b/library/panic_unwind/Cargo.toml
index 67405463aa66a..d720cc7bcbdf1 100644
--- a/library/panic_unwind/Cargo.toml
+++ b/library/panic_unwind/Cargo.toml
@@ -4,7 +4,7 @@ version = "0.0.0"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/rust.git"
 description = "Implementation of Rust panics via stack unwinding"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/library/proc_macro/Cargo.toml b/library/proc_macro/Cargo.toml
index faf460e32bd87..db5e2e4e245ea 100644
--- a/library/proc_macro/Cargo.toml
+++ b/library/proc_macro/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "proc_macro"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [dependencies]
 std = { path = "../std" }
diff --git a/library/profiler_builtins/Cargo.toml b/library/profiler_builtins/Cargo.toml
index 0f7f0067652f6..3371dfa124253 100644
--- a/library/profiler_builtins/Cargo.toml
+++ b/library/profiler_builtins/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "profiler_builtins"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 test = false
diff --git a/library/rustc-std-workspace-alloc/Cargo.toml b/library/rustc-std-workspace-alloc/Cargo.toml
index 1ea421834a7d5..049ca3e46b57d 100644
--- a/library/rustc-std-workspace-alloc/Cargo.toml
+++ b/library/rustc-std-workspace-alloc/Cargo.toml
@@ -5,7 +5,7 @@ license = 'MIT OR Apache-2.0'
 description = """
 Hack for the compiler's own build system
 """
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/library/rustc-std-workspace-core/Cargo.toml b/library/rustc-std-workspace-core/Cargo.toml
index 01e8b92e14941..ff5cfcbd64144 100644
--- a/library/rustc-std-workspace-core/Cargo.toml
+++ b/library/rustc-std-workspace-core/Cargo.toml
@@ -5,7 +5,7 @@ license = 'MIT OR Apache-2.0'
 description = """
 Hack for the compiler's own build system
 """
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/library/rustc-std-workspace-std/Cargo.toml b/library/rustc-std-workspace-std/Cargo.toml
index 811bc78d21016..3a1dc2a02b557 100644
--- a/library/rustc-std-workspace-std/Cargo.toml
+++ b/library/rustc-std-workspace-std/Cargo.toml
@@ -5,7 +5,7 @@ license = 'MIT OR Apache-2.0'
 description = """
 Hack for the compiler's own build system
 """
-edition = "2018"
+edition = "2021"
 
 [lib]
 path = "lib.rs"
diff --git a/library/test/Cargo.toml b/library/test/Cargo.toml
index 04dab6b804acc..2da41484ca564 100644
--- a/library/test/Cargo.toml
+++ b/library/test/Cargo.toml
@@ -1,7 +1,7 @@
 [package]
 name = "test"
 version = "0.0.0"
-edition = "2018"
+edition = "2021"
 
 [lib]
 crate-type = ["dylib", "rlib"]
diff --git a/library/unwind/Cargo.toml b/library/unwind/Cargo.toml
index 1941f2b5a0026..69fce8d7795c1 100644
--- a/library/unwind/Cargo.toml
+++ b/library/unwind/Cargo.toml
@@ -3,7 +3,7 @@ name = "unwind"
 version = "0.0.0"
 license = "MIT OR Apache-2.0"
 repository = "https://github.com/rust-lang/rust.git"
-edition = "2018"
+edition = "2021"
 include = [
   '/libunwind/*',
 ]
diff --git a/src/tools/tidy/src/edition.rs b/src/tools/tidy/src/edition.rs
index f610dbd806aea..b0abee459869c 100644
--- a/src/tools/tidy/src/edition.rs
+++ b/src/tools/tidy/src/edition.rs
@@ -2,11 +2,6 @@
 
 use std::path::Path;
 
-fn is_edition_2018(mut line: &str) -> bool {
-    line = line.trim();
-    line == "edition = \"2018\""
-}
-
 fn is_edition_2021(mut line: &str) -> bool {
     line = line.trim();
     line == "edition = \"2021\""
@@ -23,27 +18,13 @@ pub fn check(path: &Path, bad: &mut bool) {
                 return;
             }
 
-            // Not all library crates are ready to migrate to 2021.
-            if file.components().any(|c| c.as_os_str() == "library")
-                && file.components().all(|c| c.as_os_str() != "std")
-            {
-                let has = contents.lines().any(is_edition_2018);
-                if !has {
-                    tidy_error!(
-                        bad,
-                        "{} doesn't have `edition = \"2018\"` on a separate line",
-                        file.display()
-                    );
-                }
-            } else {
-                let is_2021 = contents.lines().any(is_edition_2021);
-                if !is_2021 {
-                    tidy_error!(
-                        bad,
-                        "{} doesn't have `edition = \"2021\"` on a separate line",
-                        file.display()
-                    );
-                }
+            let is_2021 = contents.lines().any(is_edition_2021);
+            if !is_2021 {
+                tidy_error!(
+                    bad,
+                    "{} doesn't have `edition = \"2021\"` on a separate line",
+                    file.display()
+                );
             }
         },
     );