or_fun_call bad output with vec![]

[leonardo-m]

#![allow(unused_variables)]
fn main() {
    use std::collections::HashMap;
    let mut hash = HashMap::<u32, Vec<u32>>::new();
    let foo = hash.entry(1).or_insert(vec![]);
}

Gives:

warning: use of `or_insert` followed by a function call
 --> src\main.rs:5:15
  |
5 |     let foo = hash.entry(1).or_insert(vec![]);
  |               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  |
  = note: #[warn(or_fun_call)] on by default
help: try this
  |     let foo = hash.entry(1).or_insert_with(|| < [ _ ] > :: into_vec ( box [ $ ( $ x ) , * ] ));
  = help: for further information visit https://github.com/Manishearth/rust-clippy/wiki#or_fun_call

A nicer looking warning should show .or_insert_with(|| vec![]);

[clarfonthey]

This potentially could recommend or_insert_with(Vec::new) as well.

[yacoob]

A variation on this:

warning: use of `or_insert` followed by a function call
  --> src/bin/04.rs:88:60
   |
88 |         let minutes = &mut minutes_frequency.entry(*guard).or_insert(vec![0; 60]);
   |                                                            ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `or_insert_with(|| $ crate :: vec :: from_elem ( $ elem , $ n ))`

.or_insert_with(|| vec![0; 60]) work just as well. :D I guess clippy expands the vec! macro, and then tries to advise on that.

[clarfonthey]

in that case, you are actually allocating the Vec and should be using or_insert_with.

[yacoob]

Yup, that's what I've meant; updated the comment to be less vague.

[clarfonthey]

Ah, gotcha!

[tesuji]

Current output:

warning: use of `or_insert` followed by a function call
 --> src/main.rs:5:29
  |
5 |     let foo = hash.entry(1).or_insert(vec![0; 60]);
  |                             ^^^^^^^^^^^^^^^^^^^^^^ help: try this: `or_insert_with(|| vec![0; 60])`
  |
  = note: `#[warn(clippy::or_fun_call)]` on by default
  = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#or_fun_call

So this issue is fixed? @phansch