1 use clippy_utils::diagnostics::span_lint; 2 use clippy_utils::SpanlessEq; 3 use if_chain::if_chain; 4 use rustc_hir::{BinOpKind, Expr, ExprKind, QPath}; 5 use rustc_lint::{LateContext, LateLintPass}; 6 use rustc_session::{declare_lint_pass, declare_tool_lint}; 7 8 declare_clippy_lint! { 9 /// ### What it does 10 /// Detects classic underflow/overflow checks. 11 /// 12 /// ### Why is this bad? 13 /// Most classic C underflow/overflow checks will fail in 14 /// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead. 15 /// 16 /// ### Example 17 /// ```rust 18 /// # let a = 1; 19 /// # let b = 2; 20 /// a + b < a; 21 /// ``` 22 #[clippy::version = "pre 1.29.0"] 23 pub OVERFLOW_CHECK_CONDITIONAL, 24 complexity, 25 "overflow checks inspired by C which are likely to panic" 26 } 27 28 declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]); 29 30 const OVERFLOW_MSG: &str = "you are trying to use classic C overflow conditions that will fail in Rust"; 31 const UNDERFLOW_MSG: &str = "you are trying to use classic C underflow conditions that will fail in Rust"; 32 33 impl<'tcx> LateLintPass<'tcx> for OverflowCheckConditional { 34 // a + b < a, a > a + b, a < a - b, a - b > a check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>)35 fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) { 36 let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r); 37 if_chain! { 38 if let ExprKind::Binary(ref op, first, second) = expr.kind; 39 if let ExprKind::Binary(ref op2, ident1, ident2) = first.kind; 40 if let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind; 41 if let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind; 42 if let ExprKind::Path(QPath::Resolved(_, path3)) = second.kind; 43 if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); 44 if cx.typeck_results().expr_ty(ident1).is_integral(); 45 if cx.typeck_results().expr_ty(ident2).is_integral(); 46 then { 47 if op.node == BinOpKind::Lt && op2.node == BinOpKind::Add { 48 span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); 49 } 50 if op.node == BinOpKind::Gt && op2.node == BinOpKind::Sub { 51 span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); 52 } 53 } 54 } 55 56 if_chain! { 57 if let ExprKind::Binary(ref op, first, second) = expr.kind; 58 if let ExprKind::Binary(ref op2, ident1, ident2) = second.kind; 59 if let ExprKind::Path(QPath::Resolved(_, path1)) = ident1.kind; 60 if let ExprKind::Path(QPath::Resolved(_, path2)) = ident2.kind; 61 if let ExprKind::Path(QPath::Resolved(_, path3)) = first.kind; 62 if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]); 63 if cx.typeck_results().expr_ty(ident1).is_integral(); 64 if cx.typeck_results().expr_ty(ident2).is_integral(); 65 then { 66 if op.node == BinOpKind::Gt && op2.node == BinOpKind::Add { 67 span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, OVERFLOW_MSG); 68 } 69 if op.node == BinOpKind::Lt && op2.node == BinOpKind::Sub { 70 span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span, UNDERFLOW_MSG); 71 } 72 } 73 } 74 } 75 } 76