diff options
| -rw-r--r-- | src/libcore/result.rs | 4 | ||||
| -rw-r--r-- | src/libstd/macros.rs | 28 |
2 files changed, 30 insertions, 2 deletions
diff --git a/src/libcore/result.rs b/src/libcore/result.rs index e909946ece4..003c4b2b78c 100644 --- a/src/libcore/result.rs +++ b/src/libcore/result.rs @@ -223,7 +223,9 @@ //! } //! ``` //! -//! `try!` is imported by the prelude, and is available everywhere. +//! `try!` is imported by the prelude and is available everywhere, but it can only +//! be used in functions that return `Result` because of the early return of +//! `Err` that it provides. #![stable(feature = "rust1", since = "1.0.0")] diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs index 32193b4089d..a7c18783025 100644 --- a/src/libstd/macros.rs +++ b/src/libstd/macros.rs @@ -117,7 +117,33 @@ macro_rules! println { } /// Helper macro for unwrapping `Result` values while returning early with an -/// error if the value of the expression is `Err`. +/// error if the value of the expression is `Err`. Can only be used in +/// functions that return `Result` because of the early return of `Err` that +/// it provides. +/// +/// # Examples +/// +/// ``` +/// use std::io; +/// use std::fs::File; +/// +/// fn write_to_file_using_try() -> Result<(), io::Error> { +/// let mut file = try!(File::create("my_best_friends.txt")); +/// try!(file.write_line("This is a list of my best friends.")); +/// println!("I wrote to the file"); +/// Ok() +/// } +/// // This is equivalent to: +/// fn write_to_file_using_match() -> Result<(), io::Error> { +/// let mut file = try!(File::create("my_best_friends.txt")); +/// match file.write_line("This is a list of my best friends.") { +/// Ok(_) => (), +/// Err(e) => return Err(e), +/// } +/// println!("I wrote to the file"); +/// Ok() +/// } +/// ``` #[macro_export] #[stable(feature = "rust1", since = "1.0.0")] macro_rules! try { |