RS.CLIPPY.UNINIT_ASSUMED_INIT

`MaybeUninit::uninit().assume_init()`

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

What it does

Checks for MaybeUninit::uninit().assume_init().

Why is this bad?

For most types, this is undefined behavior.

Known problems

For now, we accept empty tuples and tuples / arrays of MaybeUninit. There may be other types that allow uninitialized data, but those are not yet rigorously defined.

Example

// Beware the UB
use std::mem::MaybeUninit;

let _: usize = unsafe { MaybeUninit::uninit().assume_init() };

Note that the following is OK:

use std::mem::MaybeUninit;

let _: [MaybeUninit<bool>; 5] = unsafe {
    MaybeUninit::uninit().assume_init()
};