clippy_lints/src/arithmetic.rs

   1 use crate::utils::span_lint;
   2 use rustc::hir;
   3 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   4 use rustc::{declare_tool_lint, lint_array};
   5 use syntax::source_map::Span;
   6
   7 /// **What it does:** Checks for plain integer arithmetic.
   8 ///
   9 /// **Why is this bad?** This is only checked against overflow in debug builds.
  10 /// In some applications one wants explicitly checked, wrapping or saturating
  11 /// arithmetic.
  12 ///
  13 /// **Known problems:** None.
  14 ///
  15 /// **Example:**
  16 /// ```rust
  17 /// a + 1
  18 /// ```
  19 declare_clippy_lint! {
  20     pub INTEGER_ARITHMETIC,
  21     restriction,
  22     "any integer arithmetic statement"
  23 }
  24
  25 /// **What it does:** Checks for float arithmetic.
  26 ///
  27 /// **Why is this bad?** For some embedded systems or kernel development, it
  28 /// can be useful to rule out floating-point numbers.
  29 ///
  30 /// **Known problems:** None.
  31 ///
  32 /// **Example:**
  33 /// ```rust
  34 /// a + 1.0
  35 /// ```
  36 declare_clippy_lint! {
  37     pub FLOAT_ARITHMETIC,
  38     restriction,
  39     "any floating-point arithmetic statement"
  40 }
  41
  42 #[derive(Copy, Clone, Default)]
  43 pub struct Arithmetic {
  44     expr_span: Option<Span>,
  45     /// This field is used to check whether expressions are constants, such as in enum discriminants
  46     /// and consts
  47     const_span: Option<Span>,
  48 }
  49
  50 impl LintPass for Arithmetic {
  51     fn get_lints(&self) -> LintArray {
  52         lint_array!(INTEGER_ARITHMETIC, FLOAT_ARITHMETIC)
  53     }
  54 }
  55
  56 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
  57     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  58         if self.expr_span.is_some() {
  59             return;
  60         }
  61
  62         if let Some(span) = self.const_span {
  63             if span.contains(expr.span) {
  64                 return;
  65             }
  66         }
  67         match &expr.node {
  68             hir::ExprKind::Binary(op, l, r) => {
  69                 match op.node {
  70                     hir::BinOpKind::And
  71                     | hir::BinOpKind::Or
  72                     | hir::BinOpKind::BitAnd
  73                     | hir::BinOpKind::BitOr
  74                     | hir::BinOpKind::BitXor
  75                     | hir::BinOpKind::Shl
  76                     | hir::BinOpKind::Shr
  77                     | hir::BinOpKind::Eq
  78                     | hir::BinOpKind::Lt
  79                     | hir::BinOpKind::Le
  80                     | hir::BinOpKind::Ne
  81                     | hir::BinOpKind::Ge
  82                     | hir::BinOpKind::Gt => return,
  83                     _ => (),
  84                 }
  85                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  86                 if l_ty.is_integral() && r_ty.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.is_floating_point() && r_ty.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 ty.is_integral() {
  97                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  98                     self.expr_span = Some(expr.span);
  99                 } else if ty.is_floating_point() {
 100                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 101                     self.expr_span = Some(expr.span);
 102                 }
 103             },
 104             _ => (),
 105         }
 106     }
 107
 108     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 109         if Some(expr.span) == self.expr_span {
 110             self.expr_span = None;
 111         }
 112     }
 113
 114     fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 115         let body_owner = cx.tcx.hir().body_owner(body.id());
 116
 117         match cx.tcx.hir().body_owner_kind(body_owner) {
 118             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 119                 let body_span = cx.tcx.hir().span(body_owner);
 120
 121                 if let Some(span) = self.const_span {
 122                     if span.contains(body_span) {
 123                         return;
 124                     }
 125                 }
 126                 self.const_span = Some(body_span);
 127             },
 128             hir::BodyOwnerKind::Fn => (),
 129         }
 130     }
 131
 132     fn check_body_post(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 133         let body_owner = cx.tcx.hir().body_owner(body.id());
 134         let body_span = cx.tcx.hir().span(body_owner);
 135
 136         if let Some(span) = self.const_span {
 137             if span.contains(body_span) {
 138                 return;
 139             }
 140         }
 141         self.const_span = None;
 142     }
 143 }