From d20fc38f0a17561166fb57c83ff5660b3cd41392 Mon Sep 17 00:00:00 2001 From: Guillaume Gomez Date: Fri, 19 Jul 2024 14:51:56 +0200 Subject: [PATCH] Create new `inverted_saturating_sub` lint --- CHANGELOG.md | 1 + clippy_lints/src/declared_lints.rs | 1 + clippy_lints/src/implicit_saturating_sub.rs | 34 +++++++++++++++++++-- tests/ui/manual_arithmetic_check-2.stderr | 3 +- tests/ui/manual_arithmetic_check.fixed | 2 +- tests/ui/manual_arithmetic_check.rs | 2 +- 6 files changed, 37 insertions(+), 6 deletions(-) diff --git a/CHANGELOG.md b/CHANGELOG.md index fddc2fd994e8..0bef35529662 100644 --- a/CHANGELOG.md +++ b/CHANGELOG.md @@ -5500,6 +5500,7 @@ Released 2018-09-13 [`invalid_regex`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_regex [`invalid_upcast_comparisons`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_upcast_comparisons [`invalid_utf8_in_unchecked`]: https://rust-lang.github.io/rust-clippy/master/index.html#invalid_utf8_in_unchecked +[`inverted_saturating_sub`]: https://rust-lang.github.io/rust-clippy/master/index.html#inverted_saturating_sub [`invisible_characters`]: https://rust-lang.github.io/rust-clippy/master/index.html#invisible_characters [`is_digit_ascii_radix`]: https://rust-lang.github.io/rust-clippy/master/index.html#is_digit_ascii_radix [`items_after_statements`]: https://rust-lang.github.io/rust-clippy/master/index.html#items_after_statements diff --git a/clippy_lints/src/declared_lints.rs b/clippy_lints/src/declared_lints.rs index 8754a4dff87b..a6dd6ae73128 100644 --- a/clippy_lints/src/declared_lints.rs +++ b/clippy_lints/src/declared_lints.rs @@ -216,6 +216,7 @@ pub static LINTS: &[&crate::LintInfo] = &[ crate::implicit_return::IMPLICIT_RETURN_INFO, crate::implicit_saturating_add::IMPLICIT_SATURATING_ADD_INFO, crate::implicit_saturating_sub::IMPLICIT_SATURATING_SUB_INFO, + crate::implicit_saturating_sub::INVERTED_SATURATING_SUB_INFO, crate::implied_bounds_in_impls::IMPLIED_BOUNDS_IN_IMPLS_INFO, crate::incompatible_msrv::INCOMPATIBLE_MSRV_INFO, crate::inconsistent_struct_constructor::INCONSISTENT_STRUCT_CONSTRUCTOR_INFO, diff --git a/clippy_lints/src/implicit_saturating_sub.rs b/clippy_lints/src/implicit_saturating_sub.rs index 453ff09bf4fb..04c890620396 100644 --- a/clippy_lints/src/implicit_saturating_sub.rs +++ b/clippy_lints/src/implicit_saturating_sub.rs @@ -41,7 +41,37 @@ declare_clippy_lint! { "Perform saturating subtraction instead of implicitly checking lower bound of data type" } -declare_lint_pass!(ImplicitSaturatingSub => [IMPLICIT_SATURATING_SUB]); +declare_clippy_lint! { + /// ### What it does + /// Checks for comparisons between integers, followed by subtracting the greater value from the + /// lower one. + /// + /// ### Why is this bad? + /// This could result in an underflow and is most likely not what the user wants. If this was + /// intended to be a saturated subtraction, consider using the `saturating_sub` method directly. + /// + /// ### Example + /// ```no_run + /// let a = 12u32; + /// let b = 13u32; + /// + /// let result = if a > b { b - a } else { 0 }; + /// ``` + /// + /// Use instead: + /// ```no_run + /// let a = 12u32; + /// let b = 13u32; + /// + /// let result = a.saturating_sub(b); + /// ``` + #[clippy::version = "1.44.0"] + pub INVERTED_SATURATING_SUB, + correctness, + "Check if a variable is smaller than another one and still subtract from it even if smaller" +} + +declare_lint_pass!(ImplicitSaturatingSub => [IMPLICIT_SATURATING_SUB, INVERTED_SATURATING_SUB]); impl<'tcx> LateLintPass<'tcx> for ImplicitSaturatingSub { fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>) { @@ -182,7 +212,7 @@ fn check_subtraction( { span_lint_and_then( cx, - IMPLICIT_SATURATING_SUB, + INVERTED_SATURATING_SUB, condition_span, "inverted arithmetic check before subtraction", |diag| { diff --git a/tests/ui/manual_arithmetic_check-2.stderr b/tests/ui/manual_arithmetic_check-2.stderr index d49e536ce3fb..4121aa7464f0 100644 --- a/tests/ui/manual_arithmetic_check-2.stderr +++ b/tests/ui/manual_arithmetic_check-2.stderr @@ -9,8 +9,7 @@ note: this subtraction underflows when `b < a` | LL | let result = if a > b { b - a } else { 0 }; | ^^^^^ - = note: `-D clippy::implicit-saturating-sub` implied by `-D warnings` - = help: to override `-D warnings` add `#[allow(clippy::implicit_saturating_sub)]` + = note: `#[deny(clippy::inverted_saturating_sub)]` on by default error: inverted arithmetic check before subtraction --> tests/ui/manual_arithmetic_check-2.rs:11:23 diff --git a/tests/ui/manual_arithmetic_check.fixed b/tests/ui/manual_arithmetic_check.fixed index 600fcd3765d8..29ecbb9ad2ad 100644 --- a/tests/ui/manual_arithmetic_check.fixed +++ b/tests/ui/manual_arithmetic_check.fixed @@ -1,4 +1,4 @@ -#![warn(clippy::implicit_saturating_sub)] +#![warn(clippy::implicit_saturating_sub, clippy::inverted_saturating_sub)] #![allow(clippy::if_same_then_else)] fn main() { diff --git a/tests/ui/manual_arithmetic_check.rs b/tests/ui/manual_arithmetic_check.rs index 33f5adafe7e4..69554c6b61ca 100644 --- a/tests/ui/manual_arithmetic_check.rs +++ b/tests/ui/manual_arithmetic_check.rs @@ -1,4 +1,4 @@ -#![warn(clippy::implicit_saturating_sub)] +#![warn(clippy::implicit_saturating_sub, clippy::inverted_saturating_sub)] #![allow(clippy::if_same_then_else)] fn main() {