clippy_lints/src/suspicious_trait_impl.rs

   1 use clippy_utils::diagnostics::span_lint;
   2 use clippy_utils::{get_trait_def_id, paths, trait_ref_of_method};
   3 use if_chain::if_chain;
   4 use rustc_hir as hir;
   5 use rustc_hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   6 use rustc_lint::{LateContext, LateLintPass};
   7 use rustc_middle::hir::map::Map;
   8 use rustc_session::{declare_lint_pass, declare_tool_lint};
   9
  10 declare_clippy_lint! {
  11     /// **What it does:** Lints for suspicious operations in impls of arithmetic operators, e.g.
  12     /// subtracting elements in an Add impl.
  13     ///
  14     /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  15     ///
  16     /// **Known problems:** None.
  17     ///
  18     /// **Example:**
  19     /// ```ignore
  20     /// impl Add for Foo {
  21     ///     type Output = Foo;
  22     ///
  23     ///     fn add(self, other: Foo) -> Foo {
  24     ///         Foo(self.0 - other.0)
  25     ///     }
  26     /// }
  27     /// ```
  28     pub SUSPICIOUS_ARITHMETIC_IMPL,
  29     correctness,
  30     "suspicious use of operators in impl of arithmetic trait"
  31 }
  32
  33 declare_clippy_lint! {
  34     /// **What it does:** Lints for suspicious operations in impls of OpAssign, e.g.
  35     /// subtracting elements in an AddAssign impl.
  36     ///
  37     /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  38     ///
  39     /// **Known problems:** None.
  40     ///
  41     /// **Example:**
  42     /// ```ignore
  43     /// impl AddAssign for Foo {
  44     ///     fn add_assign(&mut self, other: Foo) {
  45     ///         *self = *self - other;
  46     ///     }
  47     /// }
  48     /// ```
  49     pub SUSPICIOUS_OP_ASSIGN_IMPL,
  50     correctness,
  51     "suspicious use of operators in impl of OpAssign trait"
  52 }
  53
  54 declare_lint_pass!(SuspiciousImpl => [SUSPICIOUS_ARITHMETIC_IMPL, SUSPICIOUS_OP_ASSIGN_IMPL]);
  55
  56 impl<'tcx> LateLintPass<'tcx> for SuspiciousImpl {
  57     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx hir::Expr<'_>) {
  58         if let hir::ExprKind::Binary(binop, _, _) | hir::ExprKind::AssignOp(binop, ..) = expr.kind {
  59             match binop.node {
  60                 hir::BinOpKind::Eq
  61                 | hir::BinOpKind::Lt
  62                 | hir::BinOpKind::Le
  63                 | hir::BinOpKind::Ne
  64                 | hir::BinOpKind::Ge
  65                 | hir::BinOpKind::Gt => return,
  66                 _ => {},
  67             }
  68
  69             // Check for more than one binary operation in the implemented function
  70             // Linting when multiple operations are involved can result in false positives
  71             let parent_fn = cx.tcx.hir().get_parent_item(expr.hir_id);
  72             if_chain! {
  73                 if let hir::Node::ImplItem(impl_item) = cx.tcx.hir().get(parent_fn);
  74                 if let hir::ImplItemKind::Fn(_, body_id) = impl_item.kind;
  75                 then {
  76                     let body = cx.tcx.hir().body(body_id);
  77                     let mut visitor = BinaryExprVisitor { nb_binops: 0 };
  78                     walk_expr(&mut visitor, &body.value);
  79                     if visitor.nb_binops > 1 {
  80                         return;
  81                     }
  82                 }
  83             }
  84
  85             if let Some(impl_trait) = check_binop(
  86                 cx,
  87                 expr,
  88                 binop.node,
  89                 &[
  90                     "Add", "Sub", "Mul", "Div", "Rem", "BitAnd", "BitOr", "BitXor", "Shl", "Shr",
  91                 ],
  92                 &[
  93                     hir::BinOpKind::Add,
  94                     hir::BinOpKind::Sub,
  95                     hir::BinOpKind::Mul,
  96                     hir::BinOpKind::Div,
  97                     hir::BinOpKind::Rem,
  98                     hir::BinOpKind::BitAnd,
  99                     hir::BinOpKind::BitOr,
 100                     hir::BinOpKind::BitXor,
 101                     hir::BinOpKind::Shl,
 102                     hir::BinOpKind::Shr,
 103                 ],
 104             ) {
 105                 span_lint(
 106                     cx,
 107                     SUSPICIOUS_ARITHMETIC_IMPL,
 108                     binop.span,
 109                     &format!("suspicious use of binary operator in `{}` impl", impl_trait),
 110                 );
 111             }
 112
 113             if let Some(impl_trait) = check_binop(
 114                 cx,
 115                 expr,
 116                 binop.node,
 117                 &[
 118                     "AddAssign",
 119                     "SubAssign",
 120                     "MulAssign",
 121                     "DivAssign",
 122                     "BitAndAssign",
 123                     "BitOrAssign",
 124                     "BitXorAssign",
 125                     "RemAssign",
 126                     "ShlAssign",
 127                     "ShrAssign",
 128                 ],
 129                 &[
 130                     hir::BinOpKind::Add,
 131                     hir::BinOpKind::Sub,
 132                     hir::BinOpKind::Mul,
 133                     hir::BinOpKind::Div,
 134                     hir::BinOpKind::BitAnd,
 135                     hir::BinOpKind::BitOr,
 136                     hir::BinOpKind::BitXor,
 137                     hir::BinOpKind::Rem,
 138                     hir::BinOpKind::Shl,
 139                     hir::BinOpKind::Shr,
 140                 ],
 141             ) {
 142                 span_lint(
 143                     cx,
 144                     SUSPICIOUS_OP_ASSIGN_IMPL,
 145                     binop.span,
 146                     &format!("suspicious use of binary operator in `{}` impl", impl_trait),
 147                 );
 148             }
 149         }
 150     }
 151 }
 152
 153 fn check_binop(
 154     cx: &LateContext<'_>,
 155     expr: &hir::Expr<'_>,
 156     binop: hir::BinOpKind,
 157     traits: &[&'static str],
 158     expected_ops: &[hir::BinOpKind],
 159 ) -> Option<&'static str> {
 160     let mut trait_ids = vec![];
 161     let [krate, module] = paths::OPS_MODULE;
 162
 163     for &t in traits {
 164         let path = [krate, module, t];
 165         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 166             trait_ids.push(trait_id);
 167         } else {
 168             return None;
 169         }
 170     }
 171
 172     // Get the actually implemented trait
 173     let parent_fn = cx.tcx.hir().get_parent_item(expr.hir_id);
 174
 175     if_chain! {
 176         if let Some(trait_ref) = trait_ref_of_method(cx, parent_fn);
 177         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.res.def_id());
 178         if binop != expected_ops[idx];
 179         then{
 180             return Some(traits[idx])
 181         }
 182     }
 183
 184     None
 185 }
 186
 187 struct BinaryExprVisitor {
 188     nb_binops: u32,
 189 }
 190
 191 impl<'tcx> Visitor<'tcx> for BinaryExprVisitor {
 192     type Map = Map<'tcx>;
 193
 194     fn visit_expr(&mut self, expr: &'tcx hir::Expr<'_>) {
 195         match expr.kind {
 196             hir::ExprKind::Binary(..)
 197             | hir::ExprKind::Unary(hir::UnOp::Not | hir::UnOp::Neg, _)
 198             | hir::ExprKind::AssignOp(..) => self.nb_binops += 1,
 199             _ => {},
 200         }
 201
 202         walk_expr(self, expr);
 203     }
 204
 205     fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
 206         NestedVisitorMap::None
 207     }
 208 }