clippy_lints/src/arithmetic.rs

   1 use crate::consts::constant_simple;
   2 use crate::utils::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 plain integer arithmetic.
  10     ///
  11     /// **Why is this bad?** This is only checked against overflow in debug builds.
  12     /// In some applications one wants explicitly checked, wrapping or saturating
  13     /// arithmetic.
  14     ///
  15     /// **Known problems:** None.
  16     ///
  17     /// **Example:**
  18     /// ```rust
  19     /// # let a = 0;
  20     /// a + 1;
  21     /// ```
  22     pub INTEGER_ARITHMETIC,
  23     restriction,
  24     "any integer arithmetic statement"
  25 }
  26
  27 declare_clippy_lint! {
  28     /// **What it does:** Checks for float arithmetic.
  29     ///
  30     /// **Why is this bad?** For some embedded systems or kernel development, it
  31     /// can be useful to rule out floating-point numbers.
  32     ///
  33     /// **Known problems:** None.
  34     ///
  35     /// **Example:**
  36     /// ```rust
  37     /// # let a = 0.0;
  38     /// a + 1.0;
  39     /// ```
  40     pub FLOAT_ARITHMETIC,
  41     restriction,
  42     "any floating-point arithmetic statement"
  43 }
  44
  45 #[derive(Copy, Clone, Default)]
  46 pub struct Arithmetic {
  47     expr_span: Option<Span>,
  48     /// This field is used to check whether expressions are constants, such as in enum discriminants
  49     /// and consts
  50     const_span: Option<Span>,
  51 }
  52
  53 impl_lint_pass!(Arithmetic => [INTEGER_ARITHMETIC, FLOAT_ARITHMETIC]);
  54
  55 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
  56     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
  57         if self.expr_span.is_some() {
  58             return;
  59         }
  60
  61         if let Some(span) = self.const_span {
  62             if span.contains(expr.span) {
  63                 return;
  64             }
  65         }
  66         match &expr.kind {
  67             hir::ExprKind::Binary(op, l, r) | hir::ExprKind::AssignOp(op, l, r) => {
  68                 match op.node {
  69                     hir::BinOpKind::And
  70                     | hir::BinOpKind::Or
  71                     | hir::BinOpKind::BitAnd
  72                     | hir::BinOpKind::BitOr
  73                     | hir::BinOpKind::BitXor
  74                     | hir::BinOpKind::Shl
  75                     | hir::BinOpKind::Shr
  76                     | hir::BinOpKind::Eq
  77                     | hir::BinOpKind::Lt
  78                     | hir::BinOpKind::Le
  79                     | hir::BinOpKind::Ne
  80                     | hir::BinOpKind::Ge
  81                     | hir::BinOpKind::Gt => return,
  82                     _ => (),
  83                 }
  84
  85                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  86                 if l_ty.peel_refs().is_integral() && r_ty.peel_refs().is_integral() {
  87                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  88                     self.expr_span = Some(expr.span);
  89                 } else if l_ty.peel_refs().is_floating_point() && r_ty.peel_refs().is_floating_point() {
  90                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  91                     self.expr_span = Some(expr.span);
  92                 }
  93             },
  94             hir::ExprKind::Unary(hir::UnOp::UnNeg, arg) => {
  95                 let ty = cx.tables.expr_ty(arg);
  96                 if constant_simple(cx, cx.tables, expr).is_none() {
  97                     if ty.is_integral() {
  98                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  99                         self.expr_span = Some(expr.span);
 100                     } else if ty.is_floating_point() {
 101                         span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 102                         self.expr_span = Some(expr.span);
 103                     }
 104                 }
 105             },
 106             _ => (),
 107         }
 108     }
 109
 110     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr<'_>) {
 111         if Some(expr.span) == self.expr_span {
 112             self.expr_span = None;
 113         }
 114     }
 115
 116     fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body<'_>) {
 117         let body_owner = cx.tcx.hir().body_owner(body.id());
 118
 119         match cx.tcx.hir().body_owner_kind(body_owner) {
 120             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 121                 let body_span = cx.tcx.hir().span(body_owner);
 122
 123                 if let Some(span) = self.const_span {
 124                     if span.contains(body_span) {
 125                         return;
 126                     }
 127                 }
 128                 self.const_span = Some(body_span);
 129             },
 130             hir::BodyOwnerKind::Fn | hir::BodyOwnerKind::Closure => (),
 131         }
 132     }
 133
 134     fn check_body_post(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body<'_>) {
 135         let body_owner = cx.tcx.hir().body_owner(body.id());
 136         let body_span = cx.tcx.hir().span(body_owner);
 137
 138         if let Some(span) = self.const_span {
 139             if span.contains(body_span) {
 140                 return;
 141             }
 142         }
 143         self.const_span = None;
 144     }
 145 }