From a7886506ad109a1d8c823fd3f32ecab2c6dfca3c Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Wed, 24 Aug 2022 14:41:22 +0200
Subject: [PATCH 1/4] Remove some documentation duplicated between `writeln!`
 and `write!`

`writeln!` already includes a reference to `write!` for more
information, so remove duplicated information.
---
 library/core/src/macros/mod.rs | 19 -------------------
 1 file changed, 19 deletions(-)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 3a115a8b8b6c6..0d4cb990d1e97 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -526,25 +526,6 @@ macro_rules! write {
 ///     Ok(())
 /// }
 /// ```
-///
-/// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects
-/// implementing either, as objects do not typically implement both. However, the module must
-/// import the traits qualified so their names do not conflict:
-///
-/// ```
-/// use std::fmt::Write as FmtWrite;
-/// use std::io::Write as IoWrite;
-///
-/// fn main() -> Result<(), Box<dyn std::error::Error>> {
-///     let mut s = String::new();
-///     let mut v = Vec::new();
-///
-///     writeln!(&mut s, "{} {}", "abc", 123)?; // uses fmt::Write::write_fmt
-///     writeln!(&mut v, "s = {:?}", s)?; // uses io::Write::write_fmt
-///     assert_eq!(v, b"s = \"abc 123\\n\"\n");
-///     Ok(())
-/// }
-/// ```
 #[macro_export]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[cfg_attr(not(test), rustc_diagnostic_item = "writeln_macro")]

From 3c8618fd82baa24523246f1380952fc7f42ec30a Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Wed, 24 Aug 2022 14:42:25 +0200
Subject: [PATCH 2/4] Update `write!` docs: can now import traits as `_` to
 avoid conflicts

---
 library/core/src/macros/mod.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 0d4cb990d1e97..8ead64808ca83 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -460,8 +460,8 @@ macro_rules! r#try {
 /// import the traits qualified so their names do not conflict:
 ///
 /// ```
-/// use std::fmt::Write as FmtWrite;
-/// use std::io::Write as IoWrite;
+/// use std::fmt::Write as _;
+/// use std::io::Write as _;
 ///
 /// fn main() -> Result<(), Box<dyn std::error::Error>> {
 ///     let mut s = String::new();

From 589db1f73af1837d633024c297abbe36074d4aca Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Wed, 24 Aug 2022 14:51:56 +0200
Subject: [PATCH 3/4] Expand example to show how to implement qualified trait
 names

---
 library/core/src/macros/mod.rs | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 8ead64808ca83..60d809c54899f 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -474,6 +474,23 @@ macro_rules! r#try {
 /// }
 /// ```
 ///
+/// If you also need the trait names themselves, such as to implement one or both on your types,
+/// import the containing module and then name them with a prefix:
+///
+/// ```
+/// # #![allow(unused_imports)]
+/// use std::fmt::{self, Write as _};
+/// use std::io::{self, Write as _};
+///
+/// struct Example;
+///
+/// impl fmt::Write for Example {
+///     fn write_str(&mut self, _s: &str) -> core::fmt::Result {
+///          unimplemented!();
+///     }
+/// }
+/// ```
+///
 /// Note: This macro can be used in `no_std` setups as well.
 /// In a `no_std` setup you are responsible for the implementation details of the components.
 ///

From ae937cc347b1f1290a9a8208d1896ed366247109 Mon Sep 17 00:00:00 2001
From: Josh Triplett <josh@joshtriplett.org>
Date: Thu, 25 Aug 2022 00:22:40 +0200
Subject: [PATCH 4/4] Clarify comment to fit `as _` better

---
 library/core/src/macros/mod.rs | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/library/core/src/macros/mod.rs b/library/core/src/macros/mod.rs
index 60d809c54899f..0bd9c8e9acfcb 100644
--- a/library/core/src/macros/mod.rs
+++ b/library/core/src/macros/mod.rs
@@ -457,7 +457,8 @@ macro_rules! r#try {
 ///
 /// A module can import both `std::fmt::Write` and `std::io::Write` and call `write!` on objects
 /// implementing either, as objects do not typically implement both. However, the module must
-/// import the traits qualified so their names do not conflict:
+/// avoid conflict between the trait names, such as by importing them as `_` or otherwise renaming
+/// them:
 ///
 /// ```
 /// use std::fmt::Write as _;