Clippy lint · Pedantic · checked with Clippy 0.1.99

clippy::unchecked_time_subtraction: Lints subtraction between an Instant and a Duration, or between two Duration values

What it meansLints subtraction between an Instant and a Duration, or between two Duration values. It is in the pedantic group and off by default.

Does it matter?

Unchecked subtraction could cause underflow on certain platforms, leading to unintentional panics.

Stricter lints with some false positives. Off by default; opt in with clippy::pedantic.

How to fix it

Clippy can fix this one for you: run cargo clippy --fix (add --allow-dirty if you have uncommitted changes). Review the diff before you commit.

Flagged

let time_passed = Instant::now() - Duration::from_secs(5);
let dur1 = Duration::from_secs(3);
let dur2 = Duration::from_secs(5);
let diff = dur1 - dur2;

Write this instead

let time_passed = Instant::now().checked_sub(Duration::from_secs(5));
let dur1 = Duration::from_secs(3);
let dur2 = Duration::from_secs(5);
let diff = dur1.checked_sub(dur2);

Turn it off, or on

It is off by default. To use it, set it to warn or deny:

Whole crate (Cargo.toml)

[lints.clippy]
unchecked_time_subtraction = "warn"

In code

#![warn(clippy::unchecked_time_subtraction)]

One run

cargo clippy -- -W clippy::unchecked-time-subtraction

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.

Settings in clippy.toml

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml

Pedanticgroup

allowdefault level

yesfixed by cargo clippy --fix

1.67.0added in Rust

Clippy's own documentation

What it does

Lints subtraction between an Instant and a Duration, or between two Duration values.

Why is this bad?

Unchecked subtraction could cause underflow on certain platforms, leading to unintentional panics.

Example

let time_passed = Instant::now() - Duration::from_secs(5);
let dur1 = Duration::from_secs(3);
let dur2 = Duration::from_secs(5);
let diff = dur1 - dur2;

Use instead:

let time_passed = Instant::now().checked_sub(Duration::from_secs(5));
let dur1 = Duration::from_secs(3);
let dur2 = Duration::from_secs(5);
let diff = dur1.checked_sub(dur2);

Past names

unchecked_duration_subtraction

Configuration

msrv: The minimum rust version that the project supports. Defaults to the rust-version field in Cargo.toml

(default: current version)

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

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