Return early with an error.

This macro is equivalent to return Err(anyhow!($args...)).

The surrounding function's or closure's return value is required to be Result<_, [anyhow::Error][crate::Error]>.

Example

# use anyhow::{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 anyhow::{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;
#
if depth > MAX_DEPTH {
    bail!(ScienceError::RecursionLimitExceeded);
}
#     Ok(())
# }