clippy::map_or_identity: expression can be simplified using `Option::unwrap_or()`

What you see

warning: expression can be simplified using `Option::unwrap_or()`
 --> main.rs:4:1
  |
4 | opt.map_or(42, |v| v);
  | ^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#map_or_identity
  = note: `#[warn(clippy::map_or_identity)]` on by default
help: consider using `unwrap_or`
  |
4 - opt.map_or(42, |v| v);
4 + opt.unwrap_or(42);
  |

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

This can be written more concisely by using unwrap_or().

Code that does something simple in a complicated way. Warns by default.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

let opt = Some(1);
opt.map_or(42, |v| v);

Write this instead

let opt = Some(1);
opt.unwrap_or(42);

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

#[allow(clippy::map_or_identity)]
fn my_function() { /* ... */ }

[lints.clippy]
map_or_identity = "allow"

cargo clippy -- -A clippy::map-or-identity

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.