diff options
Diffstat (limited to 'src/libstd')
| -rw-r--r-- | src/libstd/macros.rs | 17 |
1 files changed, 15 insertions, 2 deletions
diff --git a/src/libstd/macros.rs b/src/libstd/macros.rs index d1274a40900..8da70f5717e 100644 --- a/src/libstd/macros.rs +++ b/src/libstd/macros.rs @@ -364,7 +364,6 @@ pub mod builtin { /// /// let s = fmt::format(format_args!("hello {}", "world")); /// assert_eq!(s, format!("hello {}", "world")); - /// /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[macro_export] @@ -379,7 +378,7 @@ pub mod builtin { /// compile time, yielding an expression of type `&'static str`. /// /// If the environment variable is not defined, then a compilation error - /// will be emitted. To not emit a compile error, use the [`option_env!`] + /// will be emitted. To not emit a compile error, use the [`option_env!`] /// macro instead. /// /// [`option_env!`]: ../std/macro.option_env.html @@ -390,6 +389,20 @@ pub mod builtin { /// let path: &'static str = env!("PATH"); /// println!("the $PATH variable at the time of compiling was: {}", path); /// ``` + /// + /// You can customize the error message by passing a string as the second + /// parameter: + /// + /// ```compile_fail + /// let doc: &'static str = env!("documentation", "what's that?!"); + /// ``` + /// + /// If the `documentation` environment variable is not defined, you'll get + /// the following error: + /// + /// ```text + /// error: what's that?! + /// ``` #[stable(feature = "rust1", since = "1.0.0")] #[macro_export] macro_rules! env { |