vendor/failure/src/macros.rs

   1 /// Exits a function early with an `Error`.
   2 ///
   3 /// The `bail!` macro provides an easy way to exit a function. `bail!(X)` is
   4 /// equivalent to writing:
   5 ///
   6 /// ```rust,ignore
   7 /// return Err(format_err!(X))
   8 /// ```
   9 #[macro_export]
  10 macro_rules! bail {
  11     ($e:expr) => {
  12         return Err($crate::err_msg($e));
  13     };
  14     ($fmt:expr, $($arg:tt)*) => {
  15         return Err($crate::err_msg(format!($fmt, $($arg)*)));
  16     };
  17 }
  18
  19 /// Exits a function early with an `Error` if the condition is not satisfied.
  20 ///
  21 /// Similar to `assert!`, `ensure!` takes a condition and exits the function
  22 /// if the condition fails. Unlike `assert!`, `ensure!` returns an `Error`,
  23 /// it does not panic.
  24 #[macro_export(local_inner_macros)]
  25 macro_rules! ensure {
  26     ($cond:expr, $e:expr) => {
  27         if !($cond) {
  28             bail!($e);
  29         }
  30     };
  31     ($cond:expr, $fmt:expr, $($arg:tt)*) => {
  32         if !($cond) {
  33             bail!($fmt, $($arg)*);
  34         }
  35     };
  36 }
  37
  38 /// Constructs an `Error` using the standard string interpolation syntax.
  39 ///
  40 /// ```rust
  41 /// #[macro_use] extern crate failure;
  42 ///
  43 /// fn main() {
  44 ///     let code = 101;
  45 ///     let err = format_err!("Error code: {}", code);
  46 /// }
  47 /// ```
  48 #[macro_export]
  49 macro_rules! format_err {
  50     ($($arg:tt)*) => { $crate::err_msg(format!($($arg)*)) }
  51 }