diff options
Diffstat (limited to 'src/libcore/macros.rs')
| -rw-r--r-- | src/libcore/macros.rs | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/src/libcore/macros.rs b/src/libcore/macros.rs index cae46a0dd0f..3cf32d1a559 100644 --- a/src/libcore/macros.rs +++ b/src/libcore/macros.rs @@ -350,6 +350,21 @@ macro_rules! try { /// /// assert_eq!(w, b"testformatted arguments"); /// ``` +/// +/// 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; +/// +/// let mut s = String::new(); +/// let mut v = Vec::new(); +/// write!(&mut s, "{} {}", "abc", 123).unwrap(); // uses fmt::Write::write_fmt +/// write!(&mut v, "s = {:?}", s).unwrap(); // uses io::Write::write_fmt +/// assert_eq!(v, b"s = \"abc 123\""); +/// ``` #[macro_export] #[stable(feature = "core", since = "1.6.0")] macro_rules! write { @@ -394,6 +409,21 @@ macro_rules! write { /// /// assert_eq!(&w[..], "test\nformatted arguments\n".as_bytes()); /// ``` +/// +/// 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; +/// +/// let mut s = String::new(); +/// let mut v = Vec::new(); +/// writeln!(&mut s, "{} {}", "abc", 123).unwrap(); // uses fmt::Write::write_fmt +/// writeln!(&mut v, "s = {:?}", s).unwrap(); // uses io::Write::write_fmt +/// assert_eq!(v, b"s = \"abc 123\\n\"\n"); +/// ``` #[macro_export] #[stable(feature = "rust1", since = "1.0.0")] macro_rules! writeln { |