clippy_lints/src/arithmetic.rs

   1 use crate::consts::constant_simple;
   2 use crate::utils::span_lint;
   3 use rustc::hir;
   4 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   5 use rustc::{declare_tool_lint, lint_array};
   6 use syntax::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     /// a + 1
  20     /// ```
  21     pub INTEGER_ARITHMETIC,
  22     restriction,
  23     "any integer arithmetic statement"
  24 }
  25
  26 declare_clippy_lint! {
  27     /// **What it does:** Checks for float arithmetic.
  28     ///
  29     /// **Why is this bad?** For some embedded systems or kernel development, it
  30     /// can be useful to rule out floating-point numbers.
  31     ///
  32     /// **Known problems:** None.
  33     ///
  34     /// **Example:**
  35     /// ```rust
  36     /// a + 1.0
  37     /// ```
  38     pub FLOAT_ARITHMETIC,
  39     restriction,
  40     "any floating-point arithmetic statement"
  41 }
  42
  43 #[derive(Copy, Clone, Default)]
  44 pub struct Arithmetic {
  45     expr_span: Option<Span>,
  46     /// This field is used to check whether expressions are constants, such as in enum discriminants
  47     /// and consts
  48     const_span: Option<Span>,
  49 }
  50
  51 impl LintPass for Arithmetic {
  52     fn get_lints(&self) -> LintArray {
  53         lint_array!(INTEGER_ARITHMETIC, FLOAT_ARITHMETIC)
  54     }
  55
  56     fn name(&self) -> &'static str {
  57         "Arithmetic"
  58     }
  59 }
  60
  61 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
  62     fn check_expr(&mut self, cx: &LateContext<'a, '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.node {
  73             hir::ExprKind::Binary(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::Shl
  81                     | hir::BinOpKind::Shr
  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                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  91                 if l_ty.is_integral() && r_ty.is_integral() {
  92                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  93                     self.expr_span = Some(expr.span);
  94                 } else if l_ty.is_floating_point() && r_ty.is_floating_point() {
  95                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  96                     self.expr_span = Some(expr.span);
  97                 }
  98             },
  99             hir::ExprKind::Unary(hir::UnOp::UnNeg, arg) => {
 100                 let ty = cx.tables.expr_ty(arg);
 101                 if ty.is_integral() {
 102                     if constant_simple(cx, cx.tables, expr).is_none() {
 103                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 104                         self.expr_span = Some(expr.span);
 105                     }
 106                 } else if ty.is_floating_point() {
 107                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 108                     self.expr_span = Some(expr.span);
 109                 }
 110             },
 111             _ => (),
 112         }
 113     }
 114
 115     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 116         if Some(expr.span) == self.expr_span {
 117             self.expr_span = None;
 118         }
 119     }
 120
 121     fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 122         let body_owner = cx.tcx.hir().body_owner(body.id());
 123
 124         match cx.tcx.hir().body_owner_kind(body_owner) {
 125             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 126                 let body_span = cx.tcx.hir().span(body_owner);
 127
 128                 if let Some(span) = self.const_span {
 129                     if span.contains(body_span) {
 130                         return;
 131                     }
 132                 }
 133                 self.const_span = Some(body_span);
 134             },
 135             hir::BodyOwnerKind::Fn | hir::BodyOwnerKind::Closure => (),
 136         }
 137     }
 138
 139     fn check_body_post(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 140         let body_owner = cx.tcx.hir().body_owner(body.id());
 141         let body_span = cx.tcx.hir().span(body_owner);
 142
 143         if let Some(span) = self.const_span {
 144             if span.contains(body_span) {
 145                 return;
 146             }
 147         }
 148         self.const_span = None;
 149     }
 150 }