clippy_lints/src/arithmetic.rs

   1 use crate::consts::constant_simple;
   2 use clippy_utils::diagnostics::span_lint;
   3 use rustc_hir as hir;
   4 use rustc_lint::{LateContext, LateLintPass};
   5 use rustc_session::{declare_tool_lint, impl_lint_pass};
   6 use rustc_span::source_map::Span;
   7
   8 declare_clippy_lint! {
   9     /// **What it does:** Checks for integer arithmetic operations which could overflow or panic.
  10     ///
  11     /// Specifically, checks for any operators (`+`, `-`, `*`, `<<`, etc) which are capable
  12     /// of overflowing according to the [Rust
  13     /// Reference](https://doc.rust-lang.org/reference/expressions/operator-expr.html#overflow),
  14     /// or which can panic (`/`, `%`). No bounds analysis or sophisticated reasoning is
  15     /// attempted.
  16     ///
  17     /// **Why is this bad?** Integer overflow will trigger a panic in debug builds or will wrap in
  18     /// release mode. Division by zero will cause a panic in either mode. In some applications one
  19     /// wants explicitly checked, wrapping or saturating arithmetic.
  20     ///
  21     /// **Known problems:** None.
  22     ///
  23     /// **Example:**
  24     /// ```rust
  25     /// # let a = 0;
  26     /// a + 1;
  27     /// ```
  28     pub INTEGER_ARITHMETIC,
  29     restriction,
  30     "any integer arithmetic expression which could overflow or panic"
  31 }
  32
  33 declare_clippy_lint! {
  34     /// **What it does:** Checks for float arithmetic.
  35     ///
  36     /// **Why is this bad?** For some embedded systems or kernel development, it
  37     /// can be useful to rule out floating-point numbers.
  38     ///
  39     /// **Known problems:** None.
  40     ///
  41     /// **Example:**
  42     /// ```rust
  43     /// # let a = 0.0;
  44     /// a + 1.0;
  45     /// ```
  46     pub FLOAT_ARITHMETIC,
  47     restriction,
  48     "any floating-point arithmetic statement"
  49 }
  50
  51 #[derive(Copy, Clone, Default)]
  52 pub struct Arithmetic {
  53     expr_span: Option<Span>,
  54     /// This field is used to check whether expressions are constants, such as in enum discriminants
  55     /// and consts
  56     const_span: Option<Span>,
  57 }
  58
  59 impl_lint_pass!(Arithmetic => [INTEGER_ARITHMETIC, FLOAT_ARITHMETIC]);
  60
  61 impl<'tcx> LateLintPass<'tcx> for Arithmetic {
  62     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
  63         if self.expr_span.is_some() {
  64             return;
  65         }
  66
  67         if let Some(span) = self.const_span {
  68             if span.contains(expr.span) {
  69                 return;
  70             }
  71         }
  72         match &expr.kind {
  73             hir::ExprKind::Binary(op, l, r) | hir::ExprKind::AssignOp(op, l, r) => {
  74                 match op.node {
  75                     hir::BinOpKind::And
  76                     | hir::BinOpKind::Or
  77                     | hir::BinOpKind::BitAnd
  78                     | hir::BinOpKind::BitOr
  79                     | hir::BinOpKind::BitXor
  80                     | hir::BinOpKind::Eq
  81                     | hir::BinOpKind::Lt
  82                     | hir::BinOpKind::Le
  83                     | hir::BinOpKind::Ne
  84                     | hir::BinOpKind::Ge
  85                     | hir::BinOpKind::Gt => return,
  86                     _ => (),
  87                 }
  88
  89                 let (l_ty, r_ty) = (cx.typeck_results().expr_ty(l), cx.typeck_results().expr_ty(r));
  90                 if l_ty.peel_refs().is_integral() && r_ty.peel_refs().is_integral() {
  91                     match op.node {
  92                         hir::BinOpKind::Div | hir::BinOpKind::Rem => match &r.kind {
  93                             hir::ExprKind::Lit(_lit) => (),
  94                             hir::ExprKind::Unary(hir::UnOp::Neg, expr) => {
  95                                 if let hir::ExprKind::Lit(lit) = &expr.kind {
  96                                     if let rustc_ast::ast::LitKind::Int(1, _) = lit.node {
  97                                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  98                                         self.expr_span = Some(expr.span);
  99                                     }
 100                                 }
 101                             },
 102                             _ => {
 103                                 span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 104                                 self.expr_span = Some(expr.span);
 105                             },
 106                         },
 107                         _ => {
 108                             span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 109                             self.expr_span = Some(expr.span);
 110                         },
 111                     }
 112                 } else if r_ty.peel_refs().is_floating_point() && r_ty.peel_refs().is_floating_point() {
 113                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 114                     self.expr_span = Some(expr.span);
 115                 }
 116             },
 117             hir::ExprKind::Unary(hir::UnOp::Neg, arg) => {
 118                 let ty = cx.typeck_results().expr_ty(arg);
 119                 if constant_simple(cx, cx.typeck_results(), expr).is_none() {
 120                     if ty.is_integral() {
 121                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 122                         self.expr_span = Some(expr.span);
 123                     } else if ty.is_floating_point() {
 124                         span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 125                         self.expr_span = Some(expr.span);
 126                     }
 127                 }
 128             },
 129             _ => (),
 130         }
 131     }
 132
 133     fn check_expr_post(&mut self, _: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
 134         if Some(expr.span) == self.expr_span {
 135             self.expr_span = None;
 136         }
 137     }
 138
 139     fn check_body(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
 140         let body_owner = cx.tcx.hir().body_owner(body.id());
 141
 142         match cx.tcx.hir().body_owner_kind(body_owner) {
 143             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 144                 let body_span = cx.tcx.hir().span(body_owner);
 145
 146                 if let Some(span) = self.const_span {
 147                     if span.contains(body_span) {
 148                         return;
 149                     }
 150                 }
 151                 self.const_span = Some(body_span);
 152             },
 153             hir::BodyOwnerKind::Fn | hir::BodyOwnerKind::Closure => (),
 154         }
 155     }
 156
 157     fn check_body_post(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
 158         let body_owner = cx.tcx.hir().body_owner(body.id());
 159         let body_span = cx.tcx.hir().span(body_owner);
 160
 161         if let Some(span) = self.const_span {
 162             if span.contains(body_span) {
 163                 return;
 164             }
 165         }
 166         self.const_span = None;
 167     }
 168 }