RS.CLIPPY.VEC_INIT_THEN_PUSH

`push` immediately after `Vec` creation

This checker is a Clippy lint created by The Rust Project Contributors. The documentation shown here is a copy of the original documentation for: vec_init_then_push. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for calls to push immediately after creating a new Vec.

If the Vec is created using with_capacity this will only lint if the capacity is a constant and the number of pushes is greater than or equal to the initial capacity.

If the Vec is extended after the initial sequence of pushes and it was default initialized then this will only lint after there were at least four pushes. This number may change in the future.

Why is this bad?

The vec![] macro is both more performant and easier to read than multiple push calls.

Example

let mut v = Vec::new();
v.push(0);
v.push(1);
v.push(2);

Use instead:

let v = vec![0, 1, 2];