`get_or_insert_with` followed by unwrap can be replaced by `unwrap_or_else`

[KisaragiEffective]

What it does

get_or_insert_with followed by unwrap function can be replaced by unwrap_or_else.

unwrap function:

• unwrap
• except
• unwrap_unchecked

Lint Name

manual_option_folding

Category

style

Advantage

• Remove unsafe block for unwrap_unchecked.
• More idiomatic.

Drawbacks

No response

Example

// foo: impl Fn() -> X
// def: impl Fn() -> X
let mut opt: Option<X> = foo();
opt.get_or_insert_with(|| def());
let res: X = unsafe { opt.unwrap_unchecked() };

Could be written as:

let res: X = foo().unwrap_or_else(|| def());

[sjwang05]

@rustbot claim