From 8347d69abfd632bcbc34cbd2256a13ff958d7535 Mon Sep 17 00:00:00 2001
From: Per Lundberg <per.lundberg@ecraft.com>
Date: Fri, 11 Aug 2017 23:25:25 +0300
Subject: [PATCH] I noted tonight that using the examples straight away, e.g.
 in your `main` method or in any other method returning a
 non-`std::io::Result` value fails, because of reasons mentioned in
 https://github.com/rust-lang/rfcs/pull/1937.

I suggest uncommenting these parts of the examples, so that the examples are more "copy-pasteable" and show the true requirements for using them. The compilation errors I got wasn't enough to make me realize what the problem was:

```
error[E0277]: the trait bound `std::string::String: std::ops::Try` is not satisfied
```

(Thanks to the helpful people at #rust-beginners who helped me debug it; it was obvious once you knew the prerequisites for using the `?` operator.)
---
 src/libstd/fs.rs | 40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/src/libstd/fs.rs b/src/libstd/fs.rs
index 062186ef70866..106a52f2972ef 100644
--- a/src/libstd/fs.rs
+++ b/src/libstd/fs.rs
@@ -41,11 +41,11 @@ use time::SystemTime;
 /// use std::fs::File;
 /// use std::io::prelude::*;
 ///
-/// # fn foo() -> std::io::Result<()> {
-/// let mut file = File::create("foo.txt")?;
-/// file.write_all(b"Hello, world!")?;
-/// # Ok(())
-/// # }
+/// fn foo() -> std::io::Result<()> {
+///     let mut file = File::create("foo.txt")?;
+///     file.write_all(b"Hello, world!")?;
+///     Ok(())
+/// }
 /// ```
 ///
 /// Read the contents of a file into a [`String`]:
@@ -54,13 +54,13 @@ use time::SystemTime;
 /// use std::fs::File;
 /// use std::io::prelude::*;
 ///
-/// # fn foo() -> std::io::Result<()> {
-/// let mut file = File::open("foo.txt")?;
-/// let mut contents = String::new();
-/// file.read_to_string(&mut contents)?;
-/// assert_eq!(contents, "Hello, world!");
-/// # Ok(())
-/// # }
+/// fn foo() -> std::io::Result<()> {
+///     let mut file = File::open("foo.txt")?;
+///     let mut contents = String::new();
+///     file.read_to_string(&mut contents)?;
+///     assert_eq!(contents, "Hello, world!");
+///     Ok(())
+/// }
 /// ```
 ///
 /// It can be more efficient to read the contents of a file with a buffered
@@ -71,14 +71,14 @@ use time::SystemTime;
 /// use std::io::BufReader;
 /// use std::io::prelude::*;
 ///
-/// # fn foo() -> std::io::Result<()> {
-/// let file = File::open("foo.txt")?;
-/// let mut buf_reader = BufReader::new(file);
-/// let mut contents = String::new();
-/// buf_reader.read_to_string(&mut contents)?;
-/// assert_eq!(contents, "Hello, world!");
-/// # Ok(())
-/// # }
+/// fn foo() -> std::io::Result<()> {
+///     let file = File::open("foo.txt")?;
+///     let mut buf_reader = BufReader::new(file);
+///     let mut contents = String::new();
+///     buf_reader.read_to_string(&mut contents)?;
+///     assert_eq!(contents, "Hello, world!");
+///     Ok(())
+/// }
 /// ```
 ///
 /// [`Seek`]: ../io/trait.Seek.html