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, impl_lint_pass};
   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_lint_pass!(Arithmetic => [INTEGER_ARITHMETIC, FLOAT_ARITHMETIC]);
  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.expr_span.is_some() {
  56             return;
  57         }
  58
  59         if let Some(span) = self.const_span {
  60             if span.contains(expr.span) {
  61                 return;
  62             }
  63         }
  64         match &expr.node {
  65             hir::ExprKind::Binary(op, l, r) => {
  66                 match op.node {
  67                     hir::BinOpKind::And
  68                     | hir::BinOpKind::Or
  69                     | hir::BinOpKind::BitAnd
  70                     | hir::BinOpKind::BitOr
  71                     | hir::BinOpKind::BitXor
  72                     | hir::BinOpKind::Shl
  73                     | hir::BinOpKind::Shr
  74                     | hir::BinOpKind::Eq
  75                     | hir::BinOpKind::Lt
  76                     | hir::BinOpKind::Le
  77                     | hir::BinOpKind::Ne
  78                     | hir::BinOpKind::Ge
  79                     | hir::BinOpKind::Gt => return,
  80                     _ => (),
  81                 }
  82                 let (l_ty, r_ty) = (cx.tables.expr_ty(l), cx.tables.expr_ty(r));
  83                 if l_ty.is_integral() && r_ty.is_integral() {
  84                     span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  85                     self.expr_span = Some(expr.span);
  86                 } else if l_ty.is_floating_point() && r_ty.is_floating_point() {
  87                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
  88                     self.expr_span = Some(expr.span);
  89                 }
  90             },
  91             hir::ExprKind::Unary(hir::UnOp::UnNeg, arg) => {
  92                 let ty = cx.tables.expr_ty(arg);
  93                 if ty.is_integral() {
  94                     if constant_simple(cx, cx.tables, expr).is_none() {
  95                         span_lint(cx, INTEGER_ARITHMETIC, expr.span, "integer arithmetic detected");
  96                         self.expr_span = Some(expr.span);
  97                     }
  98                 } else if ty.is_floating_point() {
  99                     span_lint(cx, FLOAT_ARITHMETIC, expr.span, "floating-point arithmetic detected");
 100                     self.expr_span = Some(expr.span);
 101                 }
 102             },
 103             _ => (),
 104         }
 105     }
 106
 107     fn check_expr_post(&mut self, _: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
 108         if Some(expr.span) == self.expr_span {
 109             self.expr_span = None;
 110         }
 111     }
 112
 113     fn check_body(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 114         let body_owner = cx.tcx.hir().body_owner(body.id());
 115
 116         match cx.tcx.hir().body_owner_kind(body_owner) {
 117             hir::BodyOwnerKind::Static(_) | hir::BodyOwnerKind::Const => {
 118                 let body_span = cx.tcx.hir().span(body_owner);
 119
 120                 if let Some(span) = self.const_span {
 121                     if span.contains(body_span) {
 122                         return;
 123                     }
 124                 }
 125                 self.const_span = Some(body_span);
 126             },
 127             hir::BodyOwnerKind::Fn | hir::BodyOwnerKind::Closure => (),
 128         }
 129     }
 130
 131     fn check_body_post(&mut self, cx: &LateContext<'_, '_>, body: &hir::Body) {
 132         let body_owner = cx.tcx.hir().body_owner(body.id());
 133         let body_span = cx.tcx.hir().span(body_owner);
 134
 135         if let Some(span) = self.const_span {
 136             if span.contains(body_span) {
 137                 return;
 138             }
 139         }
 140         self.const_span = None;
 141     }
 142 }