mirror of
https://github.com/rust-lang/rust-clippy
synced 2024-11-10 07:04:18 +00:00
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`.
40 lines
1.8 KiB
Text
40 lines
1.8 KiB
Text
error: repeating `Vec::with_capacity` using `vec![x; n]`, which does not retain capacity
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--> tests/ui/repeat_vec_with_capacity.rs:6:9
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LL | vec![Vec::<()>::with_capacity(42); 123];
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: only the last `Vec` will have the capacity
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= note: `-D clippy::repeat-vec-with-capacity` implied by `-D warnings`
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= help: to override `-D warnings` add `#[allow(clippy::repeat_vec_with_capacity)]`
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help: if you intended to initialize multiple `Vec`s with an initial capacity, try
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LL | (0..123).map(|_| Vec::<()>::with_capacity(42)).collect::<Vec<_>>();
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| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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error: repeating `Vec::with_capacity` using `vec![x; n]`, which does not retain capacity
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--> tests/ui/repeat_vec_with_capacity.rs:12:9
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LL | vec![Vec::<()>::with_capacity(42); n];
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: only the last `Vec` will have the capacity
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help: if you intended to initialize multiple `Vec`s with an initial capacity, try
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LL | (0..n).map(|_| Vec::<()>::with_capacity(42)).collect::<Vec<_>>();
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| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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error: repeating `Vec::with_capacity` using `iter::repeat`, which does not retain capacity
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--> tests/ui/repeat_vec_with_capacity.rs:27:9
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LL | std::iter::repeat(Vec::<()>::with_capacity(42));
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| ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
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= note: none of the yielded `Vec`s will have the requested capacity
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help: if you intended to create an iterator that yields `Vec`s with an initial capacity, try
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LL | std::iter::repeat_with(|| Vec::<()>::with_capacity(42));
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| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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error: aborting due to 3 previous errors
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