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 ...)

• where clauses
• storing Fns in variants