prefer-eager-fallback

Prefer eager fallbacks when deferred evaluation cannot avoid work

Result.unwrapOrElse adds an unnecessary callback when its fallback is Copy and effect-free.
Instead, you SHOULD pass the expression directly to unwrapOr.

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

Reported

function value(result: Result<int32, string>): int32 {
    return result.unwrapOrElse(() => 0);
}
Accepted

function value(result: Result<int32, string>): int32 {
    return result.unwrapOr(0);
}
Prior art

- Clippy · unnecessarylazyevaluations

language/linter/src/rules/performance/prefereagerfallback.rs:8