If a longer method chain is undesirable due to complex logic inside, there are still a few readable, low-indent options.

ok_or and ?

We can convert an Option to a Result with a desired error, and immediately unwrap it with the ? operator. This solution probably provides the least indent possible, and can be easily used to “unwrap” multiple Options.

fn bar1(x: Option<u64>) -> Result<u64, MyErrors> {
    let x = x.ok_or(MyErrors::SomeError)?;
    // A lot of stuff going on.
    Ok(x * 2)
}

This will evaluate the error inside ok_or regardless of whether or not it will actually be used. If this computation is expensive, ok_or_else, which produces the error lazily, will be more efficient (related question).

if let

This solution can still lead to a staircase of code if nested, but may be more appropriate if the else branch logic is more involved.

fn bar2(x: Option<u64>) -> Result<u64, MyErrors> {
    if let Some(x) = x {
        // Lot of stuff here as well.
        Ok(x * 2)
    } else {
        Err(MyErrors::SomeError)
    }
}