# Try_v2
Provides a derive macro for `Try` ([try_trait_v2](https://rust-lang.github.io/rfcs/3058-try-trait-v2.html))
Also enables inter-conversion from `Result<T, E>` `where E: Into::into(Self)`
and back `where E: From::from<Self<!>>`
## Requires
- nightly or `RUSTC_BOOTSTRAP = 1`
- `#![feature(never_type)]`
- `#![feature(try_trait_v2)]`
## Limitations on the annotated type
- must be an `enum`
- must have _at least one_ generic type
- the _first_ generic type must be the `Output` type (produced when not short circuiting)
- the output variant (does not short-circuit) must be the _first_ variant and store the output
type as the _only unnamed_ field
See the [full documentation](https://docs.rs/try_v2/latest/try_v2/) for specifics on the generated code.
## Example Usage
```rust
#![feature(never_type)]
#![feature(try_trait_v2)]
use try_v2::{Try, Try_ConvertResult};
#[derive(Try, Try_ConvertResult)]
enum TestResult<T> {
Ok(T),
TestsFailed,
OtherError(String)
}
// Basic short circuiting thanks to `#[derive(Try)]`
fn run_tests() -> TestResult<()> {
TestResult::OtherError("oops!".to_string())?; // <- Function short-circuits here ...
TestResult::TestsFailed?;
TestResult::Ok(())
}
assert!(matches!(run_tests(), TestResult::OtherError(msg) if msg == "oops!"));
// Conversion from std::result::Result thanks to `#[derive(Try_ConvertResult)]`
struct TestFailure {}
impl<T> From<TestFailure> for TestResult<T> {
fn from(err: TestFailure) -> Self {
TestResult::TestsFailed
}
}
fn run_more_tests() -> TestResult<()> {
std::result::Result::Err(TestFailure{})?; // <- Function short-circuits here & converts to a TestResult...
TestResult::Ok(())
}
assert!(matches!(run_more_tests(), TestResult::TestsFailed));
```
## MSRV
1.85.1 if you are walking the grey-zone between stable and nightly via `RUSTC_BOOTSTRAP`
## Currently untested (may work, may not ...)
- `where` clauses
- storing `Fn`s in variants