use clippy_utils::diagnostics::span_lint; use clippy_utils::SpanlessEq; use if_chain::if_chain; use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; use rustc_lint::{LateContext, LateLintPass}; use rustc_session::{declare_lint_pass, declare_tool_lint}; declare_clippy_lint! { /// ### What it does /// Detects classic underflow/overflow checks. /// /// ### Why is this bad? /// Most classic C underflow/overflow checks will fail in /// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead. /// /// ### Example /// ```rust /// # let a = 1; /// # let b = 2; /// a + b < a; /// ``` pub OVERFLOW_CHECK_CONDITIONAL, complexity, "overflow checks inspired by C which are likely to panic" } declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]); const OVERFLOW_MSG: &str = "you are trying to use classic C overflow conditions that will fail in Rust"; const UNDERFLOW_MSG: &str = "you are trying to use classic C underflow conditions that will fail in Rust"; impl<'tcx> LateLintPass<'tcx> for OverflowCheckConditional { // a + b < a, a > a + b, a < a - b, a - b > a fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r); if_chain! { if let ExprKind::Binary(ref op, first, second) = expr.kind; if let ExprKind::Binary(ref op2, ident1, ident2) = first.kind; if let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind; if let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind; if let ExprKind::Path(QPath::Resolved(_, path3)) = second.kind; if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); if cx.typeck_results().expr_ty(ident1).is_integral(); if cx.typeck_results().expr_ty(ident2).is_integral(); then { if op.node == BinOpKind::Lt && op2.node == BinOpKind::Add { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); } if op.node == BinOpKind::Gt && op2.node == BinOpKind::Sub { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); } } } if_chain! { if let ExprKind::Binary(ref op, first, second) = expr.kind; if let ExprKind::Binary(ref op2, ident1, ident2) = second.kind; if let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind; if let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind; if let ExprKind::Path(QPath::Resolved(_, path3)) = first.kind; if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); if cx.typeck_results().expr_ty(ident1).is_integral(); if cx.typeck_results().expr_ty(ident2).is_integral(); then { if op.node == BinOpKind::Gt && op2.node == BinOpKind::Add { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); } if op.node == BinOpKind::Lt && op2.node == BinOpKind::Sub { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); } } } } }