Clippy lint · Suspicious · checked with Clippy 0.1.99

clippy::cast_enum_constructor: cast of an enum tuple constructor to an integer

What it meansChecks for casts from an enum tuple constructor to an integer. It is in the suspicious group and warns by default.

What you see

warning: cast of an enum tuple constructor to an integer
 --> main.rs:4:9
  |
4 | let _ = E::X as usize;
  |         ^^^^^^^^^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#cast_enum_constructor
  = note: `#[warn(clippy::cast_enum_constructor)]` on by default

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?

The cast is easily confused with casting a c-like enum value to an integer.

Code that is most likely wrong or useless. Warns by default.

How to fix it

Clippy does not fix this one automatically. Change the code by hand:

Flagged

enum E { X(i32) };
let _ = E::X as usize;

Turn it off, or on

Allow it where it does not fit your code, as narrowly as you can:

On one item

#[allow(clippy::cast_enum_constructor)]
fn my_function() { /* ... */ }

Whole crate (Cargo.toml)

[lints.clippy]
cast_enum_constructor = "allow"

One run

cargo clippy -- -A clippy::cast-enum-constructor

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.

Suspiciousgroup

warndefault level

nofixed by cargo clippy --fix

1.61.0added in Rust

Clippy's own documentation

What it does

Checks for casts from an enum tuple constructor to an integer.

Why is this bad?

The cast is easily confused with casting a c-like enum value to an integer.

Example

enum E { X(i32) };
let _ = E::X as usize;

From the Clippy lint list (0.1.99), part of the Rust project, MIT or Apache-2.0. Official entry.

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