| 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 |
| /// ```no_run |
| /// # let a = 1; |
| /// # let b = 2; |
| /// a + b < a; |
| /// ``` |
| #[clippy::version = "pre 1.29.0"] |
| 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); |
| } |
| } |
| } |
| } |
| } |