clippy::with_capacity_zero: calling `with_capacity(0)` is equivalent to `new()`

What you see

warning: calling `with_capacity(0)` is equivalent to `new()`
 --> main.rs:3:19
  |
3 | let v: Vec<i32> = Vec::with_capacity(0);
  |                   ^^^^^^^^^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#with_capacity_zero
  = note: `-W clippy::with-capacity-zero` implied by `-W clippy::pedantic`
help: use `new()` instead
  |
3 - let v: Vec<i32> = Vec::with_capacity(0);
3 + let v: Vec<i32> = Vec::new();
  |

Real output of Clippy 0.1.99 (Rust 1.99) on the example below. Names and line numbers in yours will differ.

Does it matter?

Calling with_capacity(0) does not allocate any initial capacity and behaves identically to new(). Using new() is more idiomatic, concise, and is a const fn for these types.

Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

let v: Vec<i32> = Vec::with_capacity(0);
let s = String::with_capacity(0);

Write this instead

let v: Vec<i32> = Vec::new();
let s = String::new();

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

[lints.clippy]
with_capacity_zero = "warn"

#![warn(clippy::with_capacity_zero)]

cargo clippy -- -W clippy::with-capacity-zero

The [lints] table needs Rust 1.74 or newer. In a workspace, put it under [workspace.lints.clippy] and add [lints] workspace = true to each member.