clippy::arithmetic_side_effects: arithmetic operation that can potentially result in unexpected side-effects

warning: arithmetic operation that can potentially result in unexpected side-effects
 --> main.rs:5:5
  |
5 |     n + 1
  |     ^^^^^
  |
  = help: for further information visit https://rust-lang.github.io/rust-clippy/stable/index.html#arithmetic_side_effects
  = note: requested on the command line with `-W clippy::arithmetic-side-effects`

// `n` can be any number, including `i32::MAX`.
fn foo(n: i32) -> i32 {
    n + 1
}

use rust_decimal::Decimal;
let _n = Decimal::MAX + Decimal::MAX;

[lints.clippy]
arithmetic_side_effects = "warn"

#![warn(clippy::arithmetic_side_effects)]

cargo clippy -- -W clippy::arithmetic-side-effects

Clippy's own documentation

What it does

Checks any kind of arithmetic operation of any type.

Operators like +, -, * or << are usually capable of overflowing according to the Rust Reference, or can panic (/, %).

Known safe built-in types like Wrapping or Saturating, floats, operations in constant environments, allowed types and non-constant operations that won’t overflow are ignored.

Why restrict this?

For integers, overflow will trigger a panic in debug builds or wrap the result in release mode; division by zero will cause a panic in either mode. As a result, it is desirable to explicitly call checked, wrapping or saturating arithmetic methods.

Example

// `n` can be any number, including `i32::MAX`.
fn foo(n: i32) -> i32 {
    n + 1
}

Third-party types can also overflow or present unwanted side-effects.

Example

use rust_decimal::Decimal;
let _n = Decimal::MAX + Decimal::MAX;

Past names

• integer_arithmetic

Configuration

• arithmetic-side-effects-allowed: Suppress checking of the passed type names in all types of operations.

If a specific operation is desired, consider using arithmetic_side_effects_allowed_binary or arithmetic_side_effects_allowed_unary instead.

Example

arithmetic-side-effects-allowed = ["SomeType", "AnotherType"]

Noteworthy

A type, say SomeType, listed in this configuration has the same behavior of ["SomeType" , "*"], ["*", "SomeType"] in arithmetic_side_effects_allowed_binary.

(default: [])

• arithmetic-side-effects-allowed-binary: Suppress checking of the passed type pair names in binary operations like addition or multiplication.

Supports the “*” wildcard to indicate that a certain type won’t trigger the lint regardless of the involved counterpart. For example, ["SomeType", "*"] or ["*", "AnotherType"].

Pairs are asymmetric, which means that ["SomeType", "AnotherType"] is not the same as ["AnotherType", "SomeType"].

Example

arithmetic-side-effects-allowed-binary = [["SomeType" , "f32"], ["AnotherType", "*"]]

(default: [])

• arithmetic-side-effects-allowed-unary: Suppress checking of the passed type names in unary operations like “negation” (-).

Example

arithmetic-side-effects-allowed-unary = ["SomeType", "AnotherType"]

(default: [])

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

Related lints

• unwrap_usedChecks for .unwrap() or .unwrap_err() calls on Results and .unwrap() call on Options
• module_name_repetitionsDetects public item names that are prefixed or suffixed by the containing public module’s name
• expect_usedChecks for .expect() or .expect_err() calls on Results and .expect() call on Options
• allow_attributes#[allow] attribute found
• allow_attributes_without_reason`allow` attribute without specifying a reason
• arbitrary_source_item_orderingincorrect ordering of items (must be alphabetically ordered)
• as_conversionsChecks 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
• as_pointer_underscoreusing inferred pointer cast
• as_underscoreusing `as _` conversion

All 847 Clippy lints · Rust compiler errors · Cargo.toml checker