From c351107cdc378dec4f855c29a3566fbd1d2ac358 Mon Sep 17 00:00:00 2001
From: rodrimati1992 <rodrimatt1985@gmail.com>
Date: Sun, 31 Jan 2021 01:21:06 -0300
Subject: [PATCH 1/4] Document how `MaybeUninit<Struct>` can be initialized.

---
 library/core/src/mem/maybe_uninit.rs | 39 +++++++++++++++++++++++++---
 1 file changed, 35 insertions(+), 4 deletions(-)

diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 05bcd90d3ca76..c85b5655bdb0c 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -172,10 +172,41 @@ use crate::ptr;
 ///
 /// ## Initializing a struct field-by-field
 ///
-/// There is currently no supported way to create a raw pointer or reference
-/// to a field of a struct inside `MaybeUninit<Struct>`. That means it is not possible
-/// to create a struct by calling `MaybeUninit::uninit::<Struct>()` and then writing
-/// to its fields.
+/// You can use `MaybeUninit<T>`, and the [`std::ptr::addr_of_mut`] macro, to initialize structs field by field:
+/// 
+/// ```rust
+/// use std::mem::MaybeUninit;
+/// use std::ptr::addr_of_mut;
+/// 
+/// #[derive(Debug, PartialEq)]
+/// pub struct Foo {
+///     name: String,
+///     list: Vec<u8>,
+/// }
+/// 
+/// let foo = {
+///     let mut uninit: MaybeUninit<Foo> = MaybeUninit::uninit();
+///     let ptr = uninit.as_mut_ptr();
+/// 
+///     // Initializing the `name` field
+///     unsafe { addr_of_mut!((*ptr).name).write("Bob".to_string()); }
+/// 
+///     // Initializing the `list` field
+///     // If there was a panic here, then the `String` in the `name` field would be leaked.
+///     unsafe { addr_of_mut!((*ptr).list).write(vec![0, 1, 2]); }
+/// 
+///     // All the fields are initialized, so we call `assume_init` to get an initialized Foo.
+///     unsafe { uninit.assume_init() }
+/// };
+/// 
+/// assert_eq!(
+///     foo,
+///     Foo {
+///         name: "Bob".to_string(),
+///         list: vec![0, 1, 2]
+///     }
+/// );
+/// ```
 ///
 /// [ub]: ../../reference/behavior-considered-undefined.html
 ///

From 0974026a5de5150cbffa46c1cc8f7d3256b58e30 Mon Sep 17 00:00:00 2001
From: rodrimati1992 <rodrimatt1985@gmail.com>
Date: Sun, 31 Jan 2021 01:37:48 -0300
Subject: [PATCH 2/4] Removed trailing whitespace

---
 library/core/src/mem/maybe_uninit.rs | 14 +++++++-------
 1 file changed, 7 insertions(+), 7 deletions(-)

diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index c85b5655bdb0c..3be730a35cedc 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -173,32 +173,32 @@ use crate::ptr;
 /// ## Initializing a struct field-by-field
 ///
 /// You can use `MaybeUninit<T>`, and the [`std::ptr::addr_of_mut`] macro, to initialize structs field by field:
-/// 
+///
 /// ```rust
 /// use std::mem::MaybeUninit;
 /// use std::ptr::addr_of_mut;
-/// 
+///
 /// #[derive(Debug, PartialEq)]
 /// pub struct Foo {
 ///     name: String,
 ///     list: Vec<u8>,
 /// }
-/// 
+///
 /// let foo = {
 ///     let mut uninit: MaybeUninit<Foo> = MaybeUninit::uninit();
 ///     let ptr = uninit.as_mut_ptr();
-/// 
+///
 ///     // Initializing the `name` field
 ///     unsafe { addr_of_mut!((*ptr).name).write("Bob".to_string()); }
-/// 
+///
 ///     // Initializing the `list` field
 ///     // If there was a panic here, then the `String` in the `name` field would be leaked.
 ///     unsafe { addr_of_mut!((*ptr).list).write(vec![0, 1, 2]); }
-/// 
+///
 ///     // All the fields are initialized, so we call `assume_init` to get an initialized Foo.
 ///     unsafe { uninit.assume_init() }
 /// };
-/// 
+///
 /// assert_eq!(
 ///     foo,
 ///     Foo {

From aa83e2aa0489c56c2256a0853ebfab442f57061e Mon Sep 17 00:00:00 2001
From: rodrimati1992 <rodrimatt1985@gmail.com>
Date: Sun, 31 Jan 2021 01:56:53 -0300
Subject: [PATCH 3/4] Update maybe_uninit.rs

---
 library/core/src/mem/maybe_uninit.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 3be730a35cedc..9452eb83da012 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -207,7 +207,7 @@ use crate::ptr;
 ///     }
 /// );
 /// ```
-///
+/// [`std::ptr::addr_of_mut`]: crate::ptr::addr_of_mut
 /// [ub]: ../../reference/behavior-considered-undefined.html
 ///
 /// # Layout

From 21c2343d3f95348b10b3b6ff73c3c237eea89c32 Mon Sep 17 00:00:00 2001
From: rodrimati1992 <rodrimatt1985@gmail.com>
Date: Sun, 31 Jan 2021 14:20:04 -0300
Subject: [PATCH 4/4] Update comment about leaking

---
 library/core/src/mem/maybe_uninit.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/library/core/src/mem/maybe_uninit.rs b/library/core/src/mem/maybe_uninit.rs
index 9452eb83da012..3760f5c479481 100644
--- a/library/core/src/mem/maybe_uninit.rs
+++ b/library/core/src/mem/maybe_uninit.rs
@@ -192,7 +192,7 @@ use crate::ptr;
 ///     unsafe { addr_of_mut!((*ptr).name).write("Bob".to_string()); }
 ///
 ///     // Initializing the `list` field
-///     // If there was a panic here, then the `String` in the `name` field would be leaked.
+///     // If there is a panic here, then the `String` in the `name` field leaks.
 ///     unsafe { addr_of_mut!((*ptr).list).write(vec![0, 1, 2]); }
 ///
 ///     // All the fields are initialized, so we call `assume_init` to get an initialized Foo.