Try_v2

Provides a derive macro for Try (try_trait_v2)

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 for specifics on the generated code.

Example Usage

  #![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 ...)