Summary

clippy::manual_unwrap_or_default fails to consider deref type coercion for the returned values

Lint Name

manual_unwrap_or_default

Reproducer

Playground: https://play.rust-lang.org/?version=nightly&mode=debug&edition=2021&gist=b8497c471fa7991f62cb1ef29fe18e31

fn foo(s: &Option<String>) -> &str { if let Some(s) = s { s } else { "" } } fn bar(s: Option<&String>) -> &str { if let Some(s) = s { s } else { "" } }

Clippy suggests the code s.unwrap_or_default() and then rust suggests &s.unwrap_or_default(), which naturally will not work due to returning a reference to a temporary local value.

A way to simplify foo would be to use as_deref() first:

s.as_deref().unwrap_or_default()

A way to simplify bar would be to deref the inner value using map first:

s.map(std::ops::Deref::deref).unwrap_or_default() // or s.map(|s| &**s).unwrap_or_default()

Version

Playground: Nightly channel Build using the Nightly version: 1.79.0-nightly (2024-04-08 ab5bda1aa70f707014e2) Local: rustc 1.79.0-nightly (8b2459c1f 2024-04-09) binary: rustc commit-hash: 8b2459c1f21187f9792d99310171a15e64feb9cf commit-date: 2024-04-09 host: x86_64-apple-darwin release: 1.79.0-nightly LLVM version: 18.1.3 

Additional Labels

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