Suggest use of unwrap_or_default

[ndmitchell]

What it does

Suggest using Option::unwrap_or_default when Option::unwrap_or_else is called using a function that creates the default.

Categories (optional)

• Kind: style

Makes the code shorter and more idiomatic.

Drawbacks

None.

Example

let x : Option<_> = ...
x.unwrap_or_else(Vec::new)

Could be written as:

let x : Option<_> = ...
x.unwrap_or_default()

Requires an understanding of what closures produce default values - e.g. Vec::default, Default::default, Vec::new, || Vec::new().

[pmnoxx]

+1, I see a lot of code in our code base that's like
tmp.get(arg).cloned().unwrap_or(0u64)
or
dict.get(arg).unwrap_or(HashMap::new())

[giraffate]

Oh, we've already have the unwrap_or_else_default lint.

[pmnoxx]

Oh, we've already have the unwrap_or_else_default lint.

Yes, I saw that. Though it only works when used with <TYPE>::default.
For example:
unwrap_or(u64::default) -> works
unwrap_or(0u64) -> doesn't.

[pmnoxx]

@giraffate Maybe, there should be another int, let's call it

name: use_default.
Example:

func(0u64)

Warnings message:
0u64 could be replaced with u64::default

This way, we would convert values to default, and then unwrap_or_else_default would do the rest of the work.

[giraffate]

Yes, I saw that. Though it only works when used with ::default.
For example:
unwrap_or(u64::default) -> works
unwrap_or(0u64) -> doesn't.

IMO or_fun_call should cover these cases.

This way, we would convert values to default, and then unwrap_or_else_default would do the rest of the work.

I don't want to make Clippy run multiple times. I want it to suggest the desired code once.

[pmnoxx]

Yes, I saw that. Though it only works when used with ::default.
For example:
unwrap_or(u64::default) -> works
unwrap_or(0u64) -> doesn't.

IMO or_fun_call should cover these cases.

This way, we would convert values to default, and then unwrap_or_else_default would do the rest of the work.

I don't want to make Clippy run multiple times. I want it to suggest the desired code once.

Yes, I saw that. Though it only works when used with ::default.
For example:
unwrap_or(u64::default) -> works
unwrap_or(0u64) -> doesn't.

IMO or_fun_call should cover these cases.

This way, we would convert values to default, and then unwrap_or_else_default would do the rest of the work.

I don't want to make Clippy run multiple times. I want it to suggest the desired code once.

I'm wondering whenever something like this would work: #8163

[giraffate]

#8163 fixes this, so I'm closing this.