prefer-lazy-fallback

Prefer lazy fallbacks when eager arguments perform avoidable work

An eager Result fallback is evaluated even when the result already contains a value.
Instead, you SHOULD pass a callback to unwrapOrElse when evaluating the fallback can trap or perform work.

- Category: performance
- Level: warning
- Fix: suggestion
- Scope: module

Reported

declare function recover(): int32;

function value(result: Result<int32, string>): int32 {
    return result.unwrapOr(recover());
}
Accepted

declare function recover(): int32;

function value(result: Result<int32, string>): int32 {
    return result.unwrapOrElse(() => recover());
}
Prior art

- Clippy · orfuncall

language/linter/src/rules/performance/preferlazyfallback.rs:7