unnecessary_literal_unwrap gets me confused

[tshepang]

I get the warning with this:

let version = option_env!("CARGO_PKG_VERSION");
let version = format!(
    "version: {}",
    version.unwrap_or_("(unknown version)"),
);

It gets quiet when I change it to this:

let version = option_env!("CARGO_PKG_VERSION");
let version = format!(
    "version: {}",
    if let Some(version) = version {
        version
    } else {
        "(unknown version)"
    }
};

Is this expected?

[y21]

The option_env! macro expands to Some("...") or None, so the clippy lint sees that code in its expanded form as:

let version = Some("<package version"); // option_env! expansion
let header = format!("{}",
  version.unwrap_or_("(unknown version)")
);

which makes it think that the unwrap_or is unnecessary because version is always Some.

This looks like a bug, and it should check if the Some(...)/None comes from an expansion and not lint in that case.

[tshepang]

as a sidenote, the lint goes quiet when unwrap_or happens on option_env!

[y21]

as a sidenote, the lint goes quiet when unwrap_or happens on option_env!

Looking at the code now, it already does check if the receiver of the unwrap_or call comes from an expansion and not lint then (e.g. option_env!("V").unwrap()), so this seems to be why it correctly ignores it for that case but not if you store it in a variable.

[y21]

Submitted a PR that fixes this: #11110
(deleted & reposted it here as a reply to this answer and not a new one)