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/// Return early with an error.
///
/// This macro is equivalent to `return Err(From::from($err))`.
///
/// # Example
///
/// ```
/// # use eyre::{bail, Result};
/// #
/// # fn has_permission(user: usize, resource: usize) -> bool {
/// # true
/// # }
/// #
/// # fn main() -> Result<()> {
/// # let user = 0;
/// # let resource = 0;
/// #
/// if !has_permission(user, resource) {
/// bail!("permission denied for accessing {}", resource);
/// }
/// # Ok(())
/// # }
/// ```
///
/// ```
/// # use eyre::{bail, Result};
/// # use thiserror::Error;
/// #
/// # const MAX_DEPTH: usize = 1;
/// #
/// #[derive(Error, Debug)]
/// enum ScienceError {
/// #[error("recursion limit exceeded")]
/// RecursionLimitExceeded,
/// # #[error("...")]
/// # More = (stringify! {
/// ...
/// # }, 1).1,
/// }
///
/// # fn main() -> Result<()> {
/// # let depth = 0;
/// # let err: &'static dyn std::error::Error = &ScienceError::RecursionLimitExceeded;
/// #
/// if depth > MAX_DEPTH {
/// bail!(ScienceError::RecursionLimitExceeded);
/// }
/// # Ok(())
/// # }
/// ```
#[macro_export]
macro_rules! bail {
($msg:literal $(,)?) => {
return $crate::private::Err($crate::eyre!($msg));
};
($err:expr $(,)?) => {
return $crate::private::Err($crate::eyre!($err));
};
($fmt:expr, $($arg:tt)*) => {
return $crate::private::Err($crate::eyre!($fmt, $($arg)*));
};
}
/// Return early with an error if a condition is not satisfied.
///
/// This macro is equivalent to `if !$cond { return Err(From::from($err)); }`.
///
/// Analogously to `assert!`, `ensure!` takes a condition and exits the function
/// if the condition fails. Unlike `assert!`, `ensure!` returns an `Error`
/// rather than panicking.
///
/// # Example
///
/// ```
/// # use eyre::{ensure, Result};
/// #
/// # fn main() -> Result<()> {
/// # let user = 0;
/// #
/// ensure!(user == 0, "only user 0 is allowed");
/// # Ok(())
/// # }
/// ```
///
/// ```
/// # use eyre::{ensure, Result};
/// # use thiserror::Error;
/// #
/// # const MAX_DEPTH: usize = 1;
/// #
/// #[derive(Error, Debug)]
/// enum ScienceError {
/// #[error("recursion limit exceeded")]
/// RecursionLimitExceeded,
/// # #[error("...")]
/// # More = (stringify! {
/// ...
/// # }, 1).1,
/// }
///
/// # fn main() -> Result<()> {
/// # let depth = 0;
/// #
/// ensure!(depth <= MAX_DEPTH, ScienceError::RecursionLimitExceeded);
/// # Ok(())
/// # }
/// ```
#[macro_export]
macro_rules! ensure {
($cond:expr, $msg:literal $(,)?) => {
if !$cond {
return $crate::private::Err($crate::eyre!($msg));
}
};
($cond:expr, $err:expr $(,)?) => {
if !$cond {
return $crate::private::Err($crate::eyre!($err));
}
};
($cond:expr, $fmt:expr, $($arg:tt)*) => {
if !$cond {
return $crate::private::Err($crate::eyre!($fmt, $($arg)*));
}
};
}
/// Construct an ad-hoc error from a string.
///
/// This evaluates to an `Error`. It can take either just a string, or a format
/// string with arguments. It also can take any custom type which implements
/// `Debug` and `Display`.
///
/// # Example
///
/// ```
/// # type V = ();
/// #
/// use eyre::{eyre, Result};
///
/// fn lookup(key: &str) -> Result<V> {
/// if key.len() != 16 {
/// return Err(eyre!("key length must be 16 characters, got {:?}", key));
/// }
///
/// // ...
/// # Ok(())
/// }
/// ```
#[macro_export]
macro_rules! eyre {
($msg:literal $(,)?) => ({
let error = $crate::private::format_err($crate::private::format_args!($msg));
error
});
($err:expr $(,)?) => ({
use $crate::private::kind::*;
let error = match $err {
error => (&error).eyre_kind().new(error),
};
error
});
($fmt:expr, $($arg:tt)*) => {
$crate::private::new_adhoc($crate::private::format!($fmt, $($arg)*))
};
}