1 files changed, 119 insertions, 0 deletions
diff --git a/src/tools/clippy/clippy_lints/src/operators/arithmetic.rs b/src/tools/clippy/clippy_lints/src/operators/arithmetic.rs
new file mode 100644
index 000000000..800cf249f
--- /dev/null
+++ b/src/tools/clippy/clippy_lints/src/operators/arithmetic.rs
@@ -0,0 +1,119 @@
+#![allow(
+    // False positive
+    clippy::match_same_arms
+)]
+
+use super::ARITHMETIC;
+use clippy_utils::{consts::constant_simple, diagnostics::span_lint};
+use rustc_data_structures::fx::FxHashSet;
+use rustc_hir as hir;
+use rustc_lint::{LateContext, LateLintPass};
+use rustc_session::impl_lint_pass;
+use rustc_span::source_map::Span;
+
+const HARD_CODED_ALLOWED: &[&str] = &["std::num::Saturating", "std::string::String", "std::num::Wrapping"];
+
+#[derive(Debug)]
+pub struct Arithmetic {
+    allowed: FxHashSet<String>,
+    // Used to check whether expressions are constants, such as in enum discriminants and consts
+    const_span: Option<Span>,
+    expr_span: Option<Span>,
+}
+
+impl_lint_pass!(Arithmetic => [ARITHMETIC]);
+
+impl Arithmetic {
+    #[must_use]
+    pub fn new(mut allowed: FxHashSet<String>) -> Self {
+        allowed.extend(HARD_CODED_ALLOWED.iter().copied().map(String::from));
+        Self {
+            allowed,
+            const_span: None,
+            expr_span: None,
+        }
+    }
+
+    /// Checks if the given `expr` has any of the inner `allowed` elements.
+    fn is_allowed_ty(&self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) -> bool {
+        self.allowed.contains(
+            cx.typeck_results()
+                .expr_ty(expr)
+                .to_string()
+                .split('<')
+                .next()
+                .unwrap_or_default(),
+        )
+    }
+
+    fn issue_lint(&mut self, cx: &LateContext<'_>, expr: &hir::Expr<'_>) {
+        span_lint(cx, ARITHMETIC, expr.span, "arithmetic detected");
+        self.expr_span = Some(expr.span);
+    }
+}
+
+impl<'tcx> LateLintPass<'tcx> for Arithmetic {
+    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
+        if self.expr_span.is_some() {
+            return;
+        }
+        if let Some(span) = self.const_span && span.contains(expr.span) {
+            return;
+        }
+        match &expr.kind {
+            hir::ExprKind::Binary(op, lhs, rhs) | hir::ExprKind::AssignOp(op, lhs, rhs) => {
+                let (
+                    hir::BinOpKind::Add
+                    | hir::BinOpKind::Sub
+                    | hir::BinOpKind::Mul
+                    | hir::BinOpKind::Div
+                    | hir::BinOpKind::Rem
+                    | hir::BinOpKind::Shl
+                    | hir::BinOpKind::Shr
+                ) = op.node else {
+                    return;
+                };
+                if self.is_allowed_ty(cx, lhs) || self.is_allowed_ty(cx, rhs) {
+                    return;
+                }
+                self.issue_lint(cx, expr);
+            },
+            hir::ExprKind::Unary(hir::UnOp::Neg, _) => {
+                // CTFE already takes care of things like `-1` that do not overflow.
+                if constant_simple(cx, cx.typeck_results(), expr).is_none() {
+                    self.issue_lint(cx, expr);
+                }
+            },
+            _ => {},
+        }
+    }
+
+    fn check_body(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
+        let body_owner = cx.tcx.hir().body_owner_def_id(body.id());
+        match cx.tcx.hir().body_owner_kind(body_owner) {
+            hir::BodyOwnerKind::Const | hir::BodyOwnerKind::Static(_) => {
+                let body_span = cx.tcx.def_span(body_owner);
+                if let Some(span) = self.const_span && span.contains(body_span) {
+                    return;
+                }
+                self.const_span = Some(body_span);
+            },
+            hir::BodyOwnerKind::Closure | hir::BodyOwnerKind::Fn => {},
+        }
+    }
+
+    fn check_body_post(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
+        let body_owner = cx.tcx.hir().body_owner(body.id());
+        let body_span = cx.tcx.hir().span(body_owner);
+        if let Some(span) = self.const_span && span.contains(body_span) {
+            return;
+        }
+        self.const_span = None;
+    }
+
+    fn check_expr_post(&mut self, _: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
+        if Some(expr.span) == self.expr_span {
+            self.expr_span = None;
+        }
+    }
+}