try_v2

A derive macro for try_trait_v2

Also enables auto-conversion from Result<T, E> where E: Into::into(Self)

Requires

• RUSTC_BOOTSTRAP = 1 (or nightly)
• #![feature(never_type)]
• #![feature(try_trait_v2)]

Current Limitations on the annotated type

• must be an enum
• must have one generic type
• the first and only generic type must be the Output type (produced when not short circuiting)
• the output variant (does not short-circuit) must be the first variant
• other (short-circuiting) variants can have at most one unnamed field

Example Usage

#![feature(never_type)]
#![feature(try_trait_v2)]
use try_v2::Try;

#[derive(Try)]
enum TestResult<T> {
    Ok(T),
    TestsFailed,
    OtherError(String)
}

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!"));

struct MyError {}

impl<T> From<MyError> for TestResult<T> {
    fn from(err: MyError) -> Self {
        TestResult::TestsFailed
    }
}

fn run_more_tests() -> TestResult<()> {
    Err(MyError{})?; // <- Function short-circuits here & converts to a TestResult...
    TestResult::Ok(())
}

assert!(matches!(run_more_tests(), TestResult::TestsFailed));