Closed
Description
Summary
There's a lint, slow-vector-initialization, which catches if you try to do something like this:
let mut foo = Vec::with_capacity(1024);
foo.resize(1024, 0);It suggests you use the vec! macro instead, which is faster. However, if you replace the call to Vec::with_capacity with Vec::new, you get an even worse-performing version of the same code, and clippy is no longer able to suggest the better option.
Lint Name
slow-vector-initialization
Reproducer
I tried this code:
pub fn main() {
let mut bar = Vec::new();
bar.resize(1024, 0);
}I expected to see this happen:
Raise an instance of slow-vector-initialization, something similar to this:
warning: slow zero-filling initialization
--> src/main.rs:3:5
|
2 | let mut bar = Vec::new();
| ------------------ help: consider replace allocation with: `vec![0; 1024]`
3 | bar.resize(1024, 0);
| ^^^^^^^^^^^^^^^^^^^
|
= help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#slow_vector_initialization
= note: `#[warn(clippy::slow_vector_initialization)]` on by default
Instead, this happened:
No lint raised
Version
rustc 1.70.0 (90c541806 2023-05-31)
binary: rustc
commit-hash: 90c541806f23a127002de5b4038be731ba1458ca
commit-date: 2023-05-31
host: aarch64-apple-darwin
release: 1.70.0
LLVM version: 16.0.2
(this also happens on the version running on playground right now)