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 /// **What it does:** Checks for plain integer arithmetic.
   9 ///
  10 /// **Why is this bad?** This is only checked against overflow in debug builds.
  11 /// In some applications one wants explicitly checked, wrapping or saturating
  12 /// arithmetic.
  13 ///
  14 /// **Known problems:** None.
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// a + 1
  19 /// ```
  20 declare_clippy_lint! {
  21     pub INTEGER_ARITHMETIC,
  22     restriction,
  23     "any integer arithmetic statement"
  24 }
  25
  26 /// **What it does:** Checks for float arithmetic.
  27 ///
  28 /// **Why is this bad?** For some embedded systems or kernel development, it
  29 /// can be useful to rule out floating-point numbers.
  30 ///
  31 /// **Known problems:** None.
  32 ///
  33 /// **Example:**
  34 /// ```rust
  35 /// a + 1.0
  36 /// ```
  37 declare_clippy_lint! {
  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
  57 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
  58     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  59         if self.expr_span.is_some() {
  60             return;
  61         }
  62
  63         if let Some(span) = self.const_span {
  64             if span.contains(expr.span) {
  65                 return;
  66             }
  67         }
  68         match &expr.node {
  69             hir::ExprKind::Binary(op, l, r) => {
  70                 match op.node {
  71                     hir::BinOpKind::And
  72                     | hir::BinOpKind::Or
  73                     | hir::BinOpKind::BitAnd
  74                     | hir::BinOpKind::BitOr
  75                     | hir::BinOpKind::BitXor
  76                     | hir::BinOpKind::Shl
  77                     | hir::BinOpKind::Shr
  78                     | hir::BinOpKind::Eq
  79                     | hir::BinOpKind::Lt
  80                     | hir::BinOpKind::Le
  81                     | hir::BinOpKind::Ne
  82                     | hir::BinOpKind::Ge
  83                     | hir::BinOpKind::Gt => return,
  84                     _ => (),
  85                 }
  86                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  87                 if l_ty.is_integral() && r_ty.is_integral() {
  88                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  89                     self.expr_span = Some(expr.span);
  90                 } else if l_ty.is_floating_point() && r_ty.is_floating_point() {
  91                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  92                     self.expr_span = Some(expr.span);
  93                 }
  94             },
  95             hir::ExprKind::Unary(hir::UnOp::UnNeg, arg) => {
  96                 let ty = cx.tables.expr_ty(arg);
  97                 if ty.is_integral() {
  98                     if constant_simple(cx, cx.tables, expr).is_none() {
  99                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
 100                         self.expr_span = Some(expr.span);
 101                     }
 102                 } else if ty.is_floating_point() {
 103                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 104                     self.expr_span = Some(expr.span);
 105                 }
 106             },
 107             _ => (),
 108         }
 109     }
 110
 111     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 112         if Some(expr.span) == self.expr_span {
 113             self.expr_span = None;
 114         }
 115     }
 116
 117     fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 118         let body_owner = cx.tcx.hir().body_owner(body.id());
 119
 120         match cx.tcx.hir().body_owner_kind(body_owner) {
 121             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 122                 let body_span = cx.tcx.hir().span(body_owner);
 123
 124                 if let Some(span) = self.const_span {
 125                     if span.contains(body_span) {
 126                         return;
 127                     }
 128                 }
 129                 self.const_span = Some(body_span);
 130             },
 131             hir::BodyOwnerKind::Fn => (),
 132         }
 133     }
 134
 135     fn check_body_post(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 136         let body_owner = cx.tcx.hir().body_owner(body.id());
 137         let body_span = cx.tcx.hir().span(body_owner);
 138
 139         if let Some(span) = self.const_span {
 140             if span.contains(body_span) {
 141                 return;
 142             }
 143         }
 144         self.const_span = None;
 145     }
 146 }