clippy_lints/src/suspicious_trait_impl.rs

   1 use rustc::lint::*;
   2 use rustc::hir;
   3 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   4 use syntax::ast;
   5 use crate::utils::{get_trait_def_id, span_lint};
   6
   7 /// **What it does:** Lints for suspicious operations in impls of arithmetic operators, e.g.
   8 /// subtracting elements in an Add impl.
   9 ///
  10 /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  11 ///
  12 /// **Known problems:** None.
  13 ///
  14 /// **Example:**
  15 /// ```rust
  16 /// impl Add for Foo {
  17 ///     type Output = Foo;
  18 ///
  19 ///     fn add(self, other: Foo) -> Foo {
  20 ///         Foo(self.0 - other.0)
  21 ///     }
  22 /// }
  23 /// ```
  24 declare_clippy_lint! {
  25     pub SUSPICIOUS_ARITHMETIC_IMPL,
  26     correctness,
  27     "suspicious use of operators in impl of arithmetic trait"
  28 }
  29
  30 /// **What it does:** Lints for suspicious operations in impls of OpAssign, e.g.
  31 /// subtracting elements in an AddAssign impl.
  32 ///
  33 /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  34 ///
  35 /// **Known problems:** None.
  36 ///
  37 /// **Example:**
  38 /// ```rust
  39 /// impl AddAssign for Foo {
  40 ///     fn add_assign(&mut self, other: Foo) {
  41 ///         *self = *self - other;
  42 ///     }
  43 /// }
  44 /// ```
  45 declare_clippy_lint! {
  46     pub SUSPICIOUS_OP_ASSIGN_IMPL,
  47     correctness,
  48     "suspicious use of operators in impl of OpAssign trait"
  49 }
  50
  51 #[derive(Copy, Clone)]
  52 pub struct SuspiciousImpl;
  53
  54 impl LintPass for SuspiciousImpl {
  55     fn get_lints(&self) -> LintArray {
  56         lint_array![SUSPICIOUS_ARITHMETIC_IMPL, SUSPICIOUS_OP_ASSIGN_IMPL]
  57     }
  58 }
  59
  60 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for SuspiciousImpl {
  61     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  62         if let hir::ExprKind::Binary(binop, _, _) = expr.node {
  63             match binop.node {
  64                 | hir::BinOpKind::Eq
  65                 | hir::BinOpKind::Lt
  66                 | hir::BinOpKind::Le
  67                 | hir::BinOpKind::Ne
  68                 | hir::BinOpKind::Ge
  69                 | hir::BinOpKind::Gt
  70                 => return,
  71                 _ => {},
  72             }
  73             // Check if the binary expression is part of another bi/unary expression
  74             // as a child node
  75             let mut parent_expr = cx.tcx.hir.get_parent_node(expr.id);
  76             while parent_expr != ast::CRATE_NODE_ID {
  77                 if let hir::map::Node::NodeExpr(e) = cx.tcx.hir.get(parent_expr) {
  78                     match e.node {
  79                         hir::ExprKind::Binary(..)
  80                         | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
  81                         | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => return,
  82                         _ => {},
  83                     }
  84                 }
  85                 parent_expr = cx.tcx.hir.get_parent_node(parent_expr);
  86             }
  87             // as a parent node
  88             let mut visitor = BinaryExprVisitor {
  89                 in_binary_expr: false,
  90             };
  91             walk_expr(&mut visitor, expr);
  92
  93             if visitor.in_binary_expr {
  94                 return;
  95             }
  96
  97             if let Some(impl_trait) = check_binop(
  98                 cx,
  99                 expr,
 100                 binop.node,
 101                 &["Add", "Sub", "Mul", "Div"],
 102                 &[
 103                     hir::BinOpKind::Add,
 104                     hir::BinOpKind::Sub,
 105                     hir::BinOpKind::Mul,
 106                     hir::BinOpKind::Div,
 107                 ],
 108             ) {
 109                 span_lint(
 110                     cx,
 111                     SUSPICIOUS_ARITHMETIC_IMPL,
 112                     binop.span,
 113                     &format!(
 114                         r#"Suspicious use of binary operator in `{}` impl"#,
 115                         impl_trait
 116                     ),
 117                 );
 118             }
 119
 120             if let Some(impl_trait) = check_binop(
 121                 cx,
 122                 expr,
 123                 binop.node,
 124                 &[
 125                     "AddAssign",
 126                     "SubAssign",
 127                     "MulAssign",
 128                     "DivAssign",
 129                     "BitAndAssign",
 130                     "BitOrAssign",
 131                     "BitXorAssign",
 132                     "RemAssign",
 133                     "ShlAssign",
 134                     "ShrAssign",
 135                 ],
 136                 &[
 137                     hir::BinOpKind::Add,
 138                     hir::BinOpKind::Sub,
 139                     hir::BinOpKind::Mul,
 140                     hir::BinOpKind::Div,
 141                     hir::BinOpKind::BitAnd,
 142                     hir::BinOpKind::BitOr,
 143                     hir::BinOpKind::BitXor,
 144                     hir::BinOpKind::Rem,
 145                     hir::BinOpKind::Shl,
 146                     hir::BinOpKind::Shr,
 147                 ],
 148             ) {
 149                 span_lint(
 150                     cx,
 151                     SUSPICIOUS_OP_ASSIGN_IMPL,
 152                     binop.span,
 153                     &format!(
 154                         r#"Suspicious use of binary operator in `{}` impl"#,
 155                         impl_trait
 156                     ),
 157                 );
 158             }
 159         }
 160     }
 161 }
 162
 163 fn check_binop<'a>(
 164     cx: &LateContext,
 165     expr: &hir::Expr,
 166     binop: hir::BinOpKind,
 167     traits: &[&'a str],
 168     expected_ops: &[hir::BinOpKind],
 169 ) -> Option<&'a str> {
 170     let mut trait_ids = vec![];
 171     let [krate, module] = crate::utils::paths::OPS_MODULE;
 172
 173     for t in traits {
 174         let path = [krate, module, t];
 175         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 176             trait_ids.push(trait_id);
 177         } else {
 178             return None;
 179         }
 180     }
 181
 182     // Get the actually implemented trait
 183     let parent_fn = cx.tcx.hir.get_parent(expr.id);
 184     let parent_impl = cx.tcx.hir.get_parent(parent_fn);
 185
 186     if_chain! {
 187         if parent_impl != ast::CRATE_NODE_ID;
 188         if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
 189         if let hir::ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.node;
 190         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
 191         if binop != expected_ops[idx];
 192         then{
 193             return Some(traits[idx])
 194         }
 195     }
 196
 197     None
 198 }
 199
 200 struct BinaryExprVisitor {
 201     in_binary_expr: bool,
 202 }
 203
 204 impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
 205     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 206         match expr.node {
 207             hir::ExprKind::Binary(..)
 208             | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
 209             | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => {
 210                 self.in_binary_expr = true
 211             },
 212             _ => {},
 213         }
 214
 215         walk_expr(self, expr);
 216     }
 217     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 218         NestedVisitorMap::None
 219     }
 220 }