RS.CLIPPY.AS_UNDERSCORE

Detects `as _` conversion

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

What it does

Checks for the usage of as _ conversion using inferred type.

Why restrict this?

The conversion might include lossy conversion or a dangerous cast that might go undetected due to the type being inferred.

The lint is allowed by default as using _ is less wordy than always specifying the type.

Example

fn foo(n: usize) {}
let n: u16 = 256;
foo(n as _);

Use instead:

fn foo(n: usize) {}
let n: u16 = 256;
foo(n as usize);