interface ErrorTrace

e.trace() on a value of an @error type, and r.trace() on a union that holds one (§6.5, D-3960): the frames of the ? operators this very value crossed, innermost first. The trace is stored in the value (a hidden field), so it survives copies, moves, storage, tasks and channels. The method is provided by the compiler (Sema::lookupMethod).

Example:

@error data NotFound { what: str }

fn find(k: str) -> i64 | NotFound {
  fail NotFound{ what: k }
}

fn lookup(k: str) -> i64 | NotFound {
  let v = find(k)?
  v
}

fn main() io {
  match lookup("x") {
    NotFound e => print("{e.trace().len() >= 1}")
    _ => print("found")
  }
}

true

pub(api) interface ErrorTrace

Since. 1.0.0-beta

Methods

Defined in: std/core/types.oxl:925