clippy_lints/src/overflow_check_conditional.rs

   1 use crate::utils::{span_lint, SpanlessEq};
   2 use if_chain::if_chain;
   3 use rustc::hir::*;
   4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   5 use rustc::{declare_lint_pass, declare_tool_lint};
   6
   7 declare_clippy_lint! {
   8     /// **What it does:** Detects classic underflow/overflow checks.
   9     ///
  10     /// **Why is this bad?** Most classic C underflow/overflow checks will fail in
  11     /// Rust. Users can use functions like `overflowing_*` and `wrapping_*` instead.
  12     ///
  13     /// **Known problems:** None.
  14     ///
  15     /// **Example:**
  16     /// ```rust
  17     /// a + b < a
  18     /// ```
  19     pub OVERFLOW_CHECK_CONDITIONAL,
  20     complexity,
  21     "overflow checks inspired by C which are likely to panic"
  22 }
  23
  24 declare_lint_pass!(OverflowCheckConditional => [OVERFLOW_CHECK_CONDITIONAL]);
  25
  26 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for OverflowCheckConditional {
  27     // a + b < a, a > a + b, a < a - b, a - b > a
  28     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx Expr) {
  29         let eq = |l, r| SpanlessEq::new(cx).eq_path_segment(l, r);
  30         if_chain! {
  31             if let ExprKind::Binary(ref op, ref first, ref second) = expr.node;
  32             if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = first.node;
  33             if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.node;
  34             if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.node;
  35             if let ExprKind::Path(QPath::Resolved(_, ref path3)) = second.node;
  36             if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]);
  37             if cx.tables.expr_ty(ident1).is_integral();
  38             if cx.tables.expr_ty(ident2).is_integral();
  39             then {
  40                 if let BinOpKind::Lt = op.node {
  41                     if let BinOpKind::Add = op2.node {
  42                         span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
  43                             "You are trying to use classic C overflow conditions that will fail in Rust.");
  44                     }
  45                 }
  46                 if let BinOpKind::Gt = op.node {
  47                     if let BinOpKind::Sub = op2.node {
  48                         span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
  49                             "You are trying to use classic C underflow conditions that will fail in Rust.");
  50                     }
  51                 }
  52             }
  53         }
  54
  55         if_chain! {
  56             if let ExprKind::Binary(ref op, ref first, ref second) = expr.node;
  57             if let ExprKind::Binary(ref op2, ref ident1, ref ident2) = second.node;
  58             if let ExprKind::Path(QPath::Resolved(_, ref path1)) = ident1.node;
  59             if let ExprKind::Path(QPath::Resolved(_, ref path2)) = ident2.node;
  60             if let ExprKind::Path(QPath::Resolved(_, ref path3)) = first.node;
  61             if eq(&path1.segments[0], &path3.segments[0]) || eq(&path2.segments[0], &path3.segments[0]);
  62             if cx.tables.expr_ty(ident1).is_integral();
  63             if cx.tables.expr_ty(ident2).is_integral();
  64             then {
  65                 if let BinOpKind::Gt = op.node {
  66                     if let BinOpKind::Add = op2.node {
  67                         span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
  68                             "You are trying to use classic C overflow conditions that will fail in Rust.");
  69                     }
  70                 }
  71                 if let BinOpKind::Lt = op.node {
  72                     if let BinOpKind::Sub = op2.node {
  73                         span_lint(cx, OVERFLOW_CHECK_CONDITIONAL, expr.span,
  74                             "You are trying to use classic C underflow conditions that will fail in Rust.");
  75                     }
  76                 }
  77             }
  78         }
  79     }
  80 }