clippy_lints/src/overflow_check_conditional.rs

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