acc3842d43
This lint checks for code that looks like
```rust
let something : Vec<_> = (0..100).map(|_| {
1 + 2 + 3
}).collect();
```
which is more clear as
```rust
let something : Vec<_> = std::iter::repeat_with(|| {
1 + 2 + 3
}).take(100).collect();
```
or
```rust
let something : Vec<_> =
std::iter::repeat_n(1 + 2 + 3, 100)
.collect();
```
That is, a map over a range which does nothing with the parameter
passed to it is simply a function (or closure) being called `n`
times and could be more semantically expressed using `take`.
39 lines
1.1 KiB
Rust
39 lines
1.1 KiB
Rust
#![allow(clippy::map_with_unused_argument_over_ranges)]
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#![warn(clippy::repeat_vec_with_capacity)]
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fn main() {
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{
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(0..123).map(|_| Vec::<()>::with_capacity(42)).collect::<Vec<_>>();
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//~^ ERROR: repeating `Vec::with_capacity` using `vec![x; n]`, which does not retain capacity
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}
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{
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let n = 123;
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(0..n).map(|_| Vec::<()>::with_capacity(42)).collect::<Vec<_>>();
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//~^ ERROR: repeating `Vec::with_capacity` using `vec![x; n]`, which does not retain capacity
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}
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{
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macro_rules! from_macro {
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($x:expr) => {
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vec![$x; 123];
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};
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}
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// vec expansion is from another macro, don't lint
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from_macro!(Vec::<()>::with_capacity(42));
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}
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{
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std::iter::repeat_with(|| Vec::<()>::with_capacity(42));
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//~^ ERROR: repeating `Vec::with_capacity` using `iter::repeat`, which does not retain capacity
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}
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{
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macro_rules! from_macro {
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($x:expr) => {
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std::iter::repeat($x)
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};
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}
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from_macro!(Vec::<()>::with_capacity(42));
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}
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}
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