[![version-badge][]][version] [![license-badge][]][license] [![rust-version-badge][]][rust-version]
Adding support for "throwing functions" to Rust through procedural macros.
Functions marked with the `throws` attribute return `Result`, but the "Ok" path
is used by default and you don't need to wrap ok return values in `Ok`. To throw
errors, use `?` or the `throws` macro.
> A fork of [Der Fehler](https://github.com/withoutboats/fehler) updating
dependencies and fixing issues while (by my understanding) boats is unable to
contribute to open source.
# The `#[throws]` attribute
The throws attribute modifies a function or method to make it return a
`Result`. It takes an optional typename as an argument to the attribute which
will be the error type of this function; if no typename is supplied, it uses
the default error type for this crate.
Within the function body, `return`s (including the implicit final return) are
automatically "Ok-wrapped." To raise errors, use `?` or the `throws!` macro.
For example, these two functions are equivalent:
```rust
#[throws(i32)]
fn foo(x: bool) -> i32 {
if x {
0
} else {
throw!(1);
}
}
fn bar(x: bool) -> Result<i32, i32> {
if x {
Ok(0)
} else {
Err(1)
}
}
```
## In functions that return `Option`
The attribute can be used to make a function that returns an Option using the
`as Option` syntax, demonstrated below:
```rust
// This function returns `Option<i32>`
#[throws(as Option)]
fn foo(x: bool) -> i32 {
if x {
0
} else {
throw!();
}
}
```
# The `throw!` macro
`throw!` is a macro which is equivalent to the `Err($e)?` pattern. It takes an
error type and "throws" it.
One important aspect of the `throw!` macro is that it allows you to return
errors inside of functions marked with `throws`. You cannot just `return`
errors from these functions, you need to use this macro.
# Rust Version Policy
This crate only supports the current stable version of Rust, patch releases may
use new features at any time.
# License
Licensed under either of
* Apache License, Version 2.0 ([LICENSE-APACHE](LICENSE-APACHE) or http://www.apache.org/licenses/LICENSE-2.0)
* MIT license ([LICENSE-MIT](LICENSE-MIT) or http://opensource.org/licenses/MIT)
at your option.
## Contribution
Unless you explicitly state otherwise, any contribution intentionally submitted
for inclusion in the work by you, as defined in the Apache-2.0 license, shall be
dual licensed as above, without any additional terms or conditions.
[version-badge]: https://img.shields.io/crates/v/culpa.svg?style=flat-square
[version]: https://crates.io/crates/culpa
[license-badge]: https://img.shields.io/crates/l/culpa.svg?style=flat-square
[license]: #license
[rust-version-badge]: https://img.shields.io/badge/rust-latest%20stable-blueviolet.svg?style=flat-square
[rust-version]: #rust-version-policy