clippy_lints/src/arithmetic.rs

   1 use crate::utils::span_lint;
   2 use rustc::hir;
   3 use rustc::lint::*;
   4 use rustc::{declare_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     span: Option<Span>,
  45 }
  46
  47 impl LintPass for Arithmetic {
  48     fn get_lints(&self) -> LintArray {
  49         lint_array!(INTEGER_ARITHMETIC, FLOAT_ARITHMETIC)
  50     }
  51 }
  52
  53 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for Arithmetic {
  54     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  55         if self.span.is_some() {
  56             return;
  57         }
  58         match expr.node {
  59             hir::ExprKind::Binary(ref op, ref l, ref r) => {
  60                 match op.node {
  61                     hir::BinOpKind::And
  62                     | hir::BinOpKind::Or
  63                     | hir::BinOpKind::BitAnd
  64                     | hir::BinOpKind::BitOr
  65                     | hir::BinOpKind::BitXor
  66                     | hir::BinOpKind::Shl
  67                     | hir::BinOpKind::Shr
  68                     | hir::BinOpKind::Eq
  69                     | hir::BinOpKind::Lt
  70                     | hir::BinOpKind::Le
  71                     | hir::BinOpKind::Ne
  72                     | hir::BinOpKind::Ge
  73                     | hir::BinOpKind::Gt => return,
  74                     _ => (),
  75                 }
  76                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  77                 if l_ty.is_integral() && r_ty.is_integral() {
  78                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  79                     self.span = Some(expr.span);
  80                 } else if l_ty.is_floating_point() && r_ty.is_floating_point() {
  81                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  82                     self.span = Some(expr.span);
  83                 }
  84             },
  85             hir::ExprKind::Unary(hir::UnOp::UnNeg, ref arg) => {
  86                 let ty = cx.tables.expr_ty(arg);
  87                 if ty.is_integral() {
  88                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  89                     self.span = Some(expr.span);
  90                 } else if ty.is_floating_point() {
  91                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  92                     self.span = Some(expr.span);
  93                 }
  94             },
  95             _ => (),
  96         }
  97     }
  98
  99     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 100         if Some(expr.span) == self.span {
 101             self.span = None;
 102         }
 103     }
 104 }