4 releases (1 stable)
1.0.0 | Apr 6, 2020 |
---|---|
1.0.0-alpha.2 | Nov 21, 2019 |
1.0.0-alpha.1 | Sep 23, 2019 |
0.1.0-alpha.0 | Sep 20, 2019 |
#6 in #des
32,468 downloads per month
Used in fehler
10KB
217 lines
Der Fehler
Der Fehler is a library to add 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.
Der Fehler provides these items:
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:
#[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:
// This function returns `Option<i32>`
#[throws(as Option)]
fn foo(x: bool) -> i32 {
if x {
return 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.
TODO
- Make throws work on closures and async blocks (attributes are not allowed on expressions on stable)
- Make throws work on Try types other than Result and Option (TRy is not on stable).
License
Licensed under either of
- Apache License, Version 2.0 (LICENSE-APACHE or http://www.apache.org/licenses/LICENSE-2.0)
- MIT license (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.
Dependencies
~1.5MB
~36K SLoC