Result<T, E>

Fallible operations return Result<T, E> — an enum with two variants, Ok(T) and Err(E). The compiler enforces must_use semantics: ignoring a Result value without inspecting it is a compile error, so fallible APIs cannot be silently dropped.

use system.io
use system.result

fn divide(a int, b int) Result<int, String>
    if b == 0
        return Result.Err("division by zero")
    return Result.Ok(a / b)

fn main()
    match divide(10, 2)
        Result.Ok(v): println(f"got {v}")
        Result.Err(e): println(f"err: {e}")

    // unwrap_or returns the Ok value or a fallback.
    let safe = divide(10, 0).unwrap_or(-1)
    println(f"{safe}")

    // Predicates for quick inspection.
    let r = divide(8, 4)
    println(f"{r.is_ok()} {r.is_err()}")

Inspect a result with match for full extraction, or with the helpers is_ok(), is_err(), and unwrap_or(default) for quick paths. There is no unwrap() that panics on Err — Miri's standard library does not panic, so the failure path is always explicit at the call site.