From 218caa410aa38c29984be31a5229b9fa717560ee Mon Sep 17 00:00:00 2001
From: Daniel Baumann <daniel.baumann@progress-linux.org>
Date: Wed, 17 Apr 2024 14:19:13 +0200
Subject: Merging upstream version 1.68.2+dfsg1.

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
---
 library/core/src/option.rs | 57 +++++++++++++++++++++++++++++++++++++++++-----
 1 file changed, 51 insertions(+), 6 deletions(-)

(limited to 'library/core/src/option.rs')

diff --git a/library/core/src/option.rs b/library/core/src/option.rs
index 505d964e5..7cc00e3f8 100644
--- a/library/core/src/option.rs
+++ b/library/core/src/option.rs
@@ -72,6 +72,50 @@
 //! }
 //! ```
 //!
+//! # The question mark operator, `?`
+//!
+//! Similar to the [`Result`] type, when writing code that calls many functions that return the
+//! [`Option`] type, handling `Some`/`None` can be tedious. The question mark
+//! operator, [`?`], hides some of the boilerplate of propagating values
+//! up the call stack.
+//!
+//! It replaces this:
+//!
+//! ```
+//! # #![allow(dead_code)]
+//! fn add_last_numbers(stack: &mut Vec<i32>) -> Option<i32> {
+//!     let a = stack.pop();
+//!     let b = stack.pop();
+//!
+//!     match (a, b) {
+//!         (Some(x), Some(y)) => Some(x + y),
+//!         _ => None,
+//!     }
+//! }
+//!
+//! ```
+//!
+//! With this:
+//!
+//! ```
+//! # #![allow(dead_code)]
+//! fn add_last_numbers(stack: &mut Vec<i32>) -> Option<i32> {
+//!     Some(stack.pop()? + stack.pop()?)
+//! }
+//! ```
+//!
+//! *It's much nicer!*
+//!
+//! Ending the expression with [`?`] will result in the [`Some`]'s unwrapped value, unless the
+//! result is [`None`], in which case [`None`] is returned early from the enclosing function.
+//!
+//! [`?`] can be used in functions that return [`Option`] because of the
+//! early return of [`None`] that it provides.
+//!
+//! [`?`]: crate::ops::Try
+//! [`Some`]: Some
+//! [`None`]: None
+//!
 //! # Representation
 //!
 //! Rust guarantees to optimize the following types `T` such that
@@ -608,13 +652,14 @@ impl<T> Option<T> {
     ///
     /// # Examples
     ///
-    /// Converts an <code>Option<[String]></code> into an <code>Option<[usize]></code>, preserving
-    /// the original. The [`map`] method takes the `self` argument by value, consuming the original,
-    /// so this technique uses `as_ref` to first take an `Option` to a reference
-    /// to the value inside the original.
+    /// Calculates the length of an <code>Option<[String]></code> as an <code>Option<[usize]></code>
+    /// without moving the [`String`]. The [`map`] method takes the `self` argument by value,
+    /// consuming the original, so this technique uses `as_ref` to first take an `Option` to a
+    /// reference to the value inside the original.
     ///
     /// [`map`]: Option::map
     /// [String]: ../../std/string/struct.String.html "String"
+    /// [`String`]: ../../std/string/struct.String.html "String"
     ///
     /// ```
     /// let text: Option<String> = Some("Hello, world!".to_string());
@@ -902,8 +947,8 @@ impl<T> Option<T> {
     ///
     /// # Examples
     ///
-    /// Converts an <code>Option<[String]></code> into an <code>Option<[usize]></code>, consuming
-    /// the original:
+    /// Calculates the length of an <code>Option<[String]></code> as an
+    /// <code>Option<[usize]></code>, consuming the original:
     ///
     /// [String]: ../../std/string/struct.String.html "String"
     /// ```
-- 
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