Usage of unwrap_or followed by a function call RS-W1031

Calls to unwrap_or followed by a function call should be replaced with unwrap_or_else or unwrap_or_default, to increase laziness. The argument to unwrap_or is evaluated eagerly and unconditionally. unwrap_or_else or unwrap_or_default are evaluated lazily and only if required, sometimes leading to lower overhead and fewer allocations. Replace the call to unwrap_or with unwrap_or_else or unwrap_or_default.

Bad practice

// allocates a new `Foo` instance even if `bar` is `Ok(_)`
bar.unwrap_or(Foo::new());

Recommended

// only allocates if `bar` evaluates to `Err(_)`
bar.unwrap_or_else(|| Foo::new());