RS.CLIPPY.AS_CONVERSIONS

Using a potentially dangerous silent `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_conversions. Copyright ©2025 The Rust Team. All rights reserved.

What it does

Checks for usage of as conversions.

Note that this lint is specialized in linting every single use of as regardless of whether good alternatives exist or not. If you want more precise lints for as, please consider using these separate lints:

clippy::cast_lossless
clippy::cast_possible_truncation
clippy::cast_possible_wrap
clippy::cast_precision_loss
clippy::cast_sign_loss
clippy::char_lit_as_u8
clippy::fn_to_numeric_cast
clippy::fn_to_numeric_cast_with_truncation
clippy::ptr_as_ptr
clippy::unnecessary_cast
invalid_reference_casting

There is a good explanation the reason why this lint should work in this way and how it is useful in this issue.

Why restrict this?

as conversions will perform many kinds of conversions, including silently lossy conversions and dangerous coercions. There are cases when it makes sense to use as, so the lint is Allow by default.

Example

let a: u32;
...
f(a as u16);

Use instead:

f(a.try_into()?);

// or

f(a.try_into().expect("Unexpected u16 overflow in f"));