src/tools/clippy/clippy_lints/src/arithmetic.rs

   1 use clippy_utils::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
  10     /// Checks for integer arithmetic operations which could overflow or panic.
  11     ///
  12     /// Specifically, checks for any operators (`+`, `-`, `*`, `<<`, etc) which are capable
  13     /// of overflowing according to the [Rust
  14     /// Reference](https://doc.rust-lang.org/reference/expressions/operator-expr.html#overflow),
  15     /// or which can panic (`/`, `%`). No bounds analysis or sophisticated reasoning is
  16     /// attempted.
  17     ///
  18     /// ### Why is this bad?
  19     /// Integer overflow will trigger a panic in debug builds or will wrap in
  20     /// release mode. Division by zero will cause a panic in either mode. In some applications one
  21     /// wants explicitly checked, wrapping or saturating arithmetic.
  22     ///
  23     /// ### Example
  24     /// ```rust
  25     /// # let a = 0;
  26     /// a + 1;
  27     /// ```
  28     #[clippy::version = "pre 1.29.0"]
  29     pub INTEGER_ARITHMETIC,
  30     restriction,
  31     "any integer arithmetic expression which could overflow or panic"
  32 }
  33
  34 declare_clippy_lint! {
  35     /// ### What it does
  36     /// Checks for float arithmetic.
  37     ///
  38     /// ### Why is this bad?
  39     /// For some embedded systems or kernel development, it
  40     /// can be useful to rule out floating-point numbers.
  41     ///
  42     /// ### Example
  43     /// ```rust
  44     /// # let a = 0.0;
  45     /// a + 1.0;
  46     /// ```
  47     #[clippy::version = "pre 1.29.0"]
  48     pub FLOAT_ARITHMETIC,
  49     restriction,
  50     "any floating-point arithmetic statement"
  51 }
  52
  53 #[derive(Copy, Clone, Default)]
  54 pub struct Arithmetic {
  55     expr_span: Option<Span>,
  56     /// This field is used to check whether expressions are constants, such as in enum discriminants
  57     /// and consts
  58     const_span: Option<Span>,
  59 }
  60
  61 impl_lint_pass!(Arithmetic => [INTEGER_ARITHMETIC, FLOAT_ARITHMETIC]);
  62
  63 impl<'tcx> LateLintPass<'tcx> for Arithmetic {
  64     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
  65         if self.expr_span.is_some() {
  66             return;
  67         }
  68
  69         if let Some(span) = self.const_span {
  70             if span.contains(expr.span) {
  71                 return;
  72             }
  73         }
  74         match &expr.kind {
  75             hir::ExprKind::Binary(op, l, r) | hir::ExprKind::AssignOp(op, l, r) => {
  76                 match op.node {
  77                     hir::BinOpKind::And
  78                     | hir::BinOpKind::Or
  79                     | hir::BinOpKind::BitAnd
  80                     | hir::BinOpKind::BitOr
  81                     | hir::BinOpKind::BitXor
  82                     | hir::BinOpKind::Eq
  83                     | hir::BinOpKind::Lt
  84                     | hir::BinOpKind::Le
  85                     | hir::BinOpKind::Ne
  86                     | hir::BinOpKind::Ge
  87                     | hir::BinOpKind::Gt => return,
  88                     _ => (),
  89                 }
  90
  91                 let (l_ty, r_ty) = (cx.typeck_results().expr_ty(l), cx.typeck_results().expr_ty(r));
  92                 if l_ty.peel_refs().is_integral() && r_ty.peel_refs().is_integral() {
  93                     match op.node {
  94                         hir::BinOpKind::Div | hir::BinOpKind::Rem => match &r.kind {
  95                             hir::ExprKind::Lit(_lit) => (),
  96                             hir::ExprKind::Unary(hir::UnOp::Neg, expr) => {
  97                                 if let hir::ExprKind::Lit(lit) = &expr.kind {
  98                                     if let rustc_ast::ast::LitKind::Int(1, _) = lit.node {
  99                                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 100                                         self.expr_span = Some(expr.span);
 101                                     }
 102                                 }
 103                             },
 104                             _ => {
 105                                 span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 106                                 self.expr_span = Some(expr.span);
 107                             },
 108                         },
 109                         _ => {
 110                             span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 111                             self.expr_span = Some(expr.span);
 112                         },
 113                     }
 114                 } else if r_ty.peel_refs().is_floating_point() && r_ty.peel_refs().is_floating_point() {
 115                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 116                     self.expr_span = Some(expr.span);
 117                 }
 118             },
 119             hir::ExprKind::Unary(hir::UnOp::Neg, arg) => {
 120                 let ty = cx.typeck_results().expr_ty(arg);
 121                 if constant_simple(cx, cx.typeck_results(), expr).is_none() {
 122                     if ty.is_integral() {
 123                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 124                         self.expr_span = Some(expr.span);
 125                     } else if ty.is_floating_point() {
 126                         span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 127                         self.expr_span = Some(expr.span);
 128                     }
 129                 }
 130             },
 131             _ => (),
 132         }
 133     }
 134
 135     fn check_expr_post(&mut self, _: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
 136         if Some(expr.span) == self.expr_span {
 137             self.expr_span = None;
 138         }
 139     }
 140
 141     fn check_body(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
 142         let body_owner = cx.tcx.hir().body_owner(body.id());
 143
 144         match cx.tcx.hir().body_owner_kind(body_owner) {
 145             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 146                 let body_span = cx.tcx.hir().span(body_owner);
 147
 148                 if let Some(span) = self.const_span {
 149                     if span.contains(body_span) {
 150                         return;
 151                     }
 152                 }
 153                 self.const_span = Some(body_span);
 154             },
 155             hir::BodyOwnerKind::Fn | hir::BodyOwnerKind::Closure => (),
 156         }
 157     }
 158
 159     fn check_body_post(&mut self, cx: &LateContext<'_>, body: &hir::Body<'_>) {
 160         let body_owner = cx.tcx.hir().body_owner(body.id());
 161         let body_span = cx.tcx.hir().span(body_owner);
 162
 163         if let Some(span) = self.const_span {
 164             if span.contains(body_span) {
 165                 return;
 166             }
 167         }
 168         self.const_span = None;
 169     }
 170 }