use crate::utils::{span_lint, SpanlessEq}; use if_chain::if_chain; use rustc::declare_lint_pass; use rustc::hir::*; use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass}; use rustc_session::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. /// /// **Known problems:** None. /// /// **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]); impl<'a, 'tcx> LateLintPass<'a, 'tcx> for OverflowCheckConditional { // a + b < a, a > a + b, a < a - b, a - b > a fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) { let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r); if_chain! { if let ExprKind::Binary(ref op, ref first, ref second) = expr.kind; if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = first.kind; if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.kind; if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.kind; if let ExprKind::Path(QPath::Resolved(_, ref path3)) = second.kind; if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); if cx.tables.expr_ty(ident1).is_integral(); if cx.tables.expr_ty(ident2).is_integral(); then { if let BinOpKind::Lt = op.node { if let BinOpKind::Add = op2.node { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C overflow conditions that will fail in Rust."); } } if let BinOpKind::Gt = op.node { if let BinOpKind::Sub = op2.node { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C underflow conditions that will fail in Rust."); } } } } if_chain! { if let ExprKind::Binary(ref op, ref first, ref second) = expr.kind; if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = second.kind; if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.kind; if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.kind; if let ExprKind::Path(QPath::Resolved(_, ref path3)) = first.kind; if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); if cx.tables.expr_ty(ident1).is_integral(); if cx.tables.expr_ty(ident2).is_integral(); then { if let BinOpKind::Gt = op.node { if let BinOpKind::Add = op2.node { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C overflow conditions that will fail in Rust."); } } if let BinOpKind::Lt = op.node { if let BinOpKind::Sub = op2.node { span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, "You are trying to use classic C underflow conditions that will fail in Rust."); } } } } } }