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         use rustc::hir::BinOp_::*;
  63         if let hir::ExprBinary(binop, _, _) = expr.node {
  64             match binop.node {
  65                 BiEq | BiLt | BiLe | BiNe | BiGe | BiGt => return,
  66                 _ => {},
  67             }
  68             // Check if the binary expression is part of another bi/unary expression
  69             // as a child node
  70             let mut parent_expr = cx.tcx.hir.get_parent_node(expr.id);
  71             while parent_expr != ast::CRATE_NODE_ID {
  72                 if let hir::map::Node::NodeExpr(e) = cx.tcx.hir.get(parent_expr) {
  73                     match e.node {
  74                         hir::ExprBinary(..)
  75                         | hir::ExprUnary(hir::UnOp::UnNot, _)
  76                         | hir::ExprUnary(hir::UnOp::UnNeg, _) => return,
  77                         _ => {},
  78                     }
  79                 }
  80                 parent_expr = cx.tcx.hir.get_parent_node(parent_expr);
  81             }
  82             // as a parent node
  83             let mut visitor = BinaryExprVisitor {
  84                 in_binary_expr: false,
  85             };
  86             walk_expr(&mut visitor, expr);
  87
  88             if visitor.in_binary_expr {
  89                 return;
  90             }
  91
  92             if let Some(impl_trait) = check_binop(
  93                 cx,
  94                 expr,
  95                 &binop.node,
  96                 &["Add", "Sub", "Mul", "Div"],
  97                 &[BiAdd, BiSub, BiMul, BiDiv],
  98             ) {
  99                 span_lint(
 100                     cx,
 101                     SUSPICIOUS_ARITHMETIC_IMPL,
 102                     binop.span,
 103                     &format!(
 104                         r#"Suspicious use of binary operator in `{}` impl"#,
 105                         impl_trait
 106                     ),
 107                 );
 108             }
 109
 110             if let Some(impl_trait) = check_binop(
 111                 cx,
 112                 expr,
 113                 &binop.node,
 114                 &[
 115                     "AddAssign",
 116                     "SubAssign",
 117                     "MulAssign",
 118                     "DivAssign",
 119                     "BitAndAssign",
 120                     "BitOrAssign",
 121                     "BitXorAssign",
 122                     "RemAssign",
 123                     "ShlAssign",
 124                     "ShrAssign",
 125                 ],
 126                 &[
 127                     BiAdd, BiSub, BiMul, BiDiv, BiBitAnd, BiBitOr, BiBitXor, BiRem, BiShl, BiShr
 128                 ],
 129             ) {
 130                 span_lint(
 131                     cx,
 132                     SUSPICIOUS_OP_ASSIGN_IMPL,
 133                     binop.span,
 134                     &format!(
 135                         r#"Suspicious use of binary operator in `{}` impl"#,
 136                         impl_trait
 137                     ),
 138                 );
 139             }
 140         }
 141     }
 142 }
 143
 144 fn check_binop<'a>(
 145     cx: &LateContext,
 146     expr: &hir::Expr,
 147     binop: &hir::BinOp_,
 148     traits: &[&'a str],
 149     expected_ops: &[hir::BinOp_],
 150 ) -> Option<&'a str> {
 151     let mut trait_ids = vec![];
 152     let [krate, module] = crate::utils::paths::OPS_MODULE;
 153
 154     for t in traits {
 155         let path = [krate, module, t];
 156         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 157             trait_ids.push(trait_id);
 158         } else {
 159             return None;
 160         }
 161     }
 162
 163     // Get the actually implemented trait
 164     let parent_fn = cx.tcx.hir.get_parent(expr.id);
 165     let parent_impl = cx.tcx.hir.get_parent(parent_fn);
 166
 167     if_chain! {
 168         if parent_impl != ast::CRATE_NODE_ID;
 169         if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
 170         if let hir::Item_::ItemImpl(_, _, _, _, Some(ref trait_ref), _, _) = item.node;
 171         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
 172         if *binop != expected_ops[idx];
 173         then{
 174             return Some(traits[idx])
 175         }
 176     }
 177
 178     None
 179 }
 180
 181 struct BinaryExprVisitor {
 182     in_binary_expr: bool,
 183 }
 184
 185 impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
 186     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 187         match expr.node {
 188             hir::ExprBinary(..)
 189             | hir::ExprUnary(hir::UnOp::UnNot, _)
 190             | hir::ExprUnary(hir::UnOp::UnNeg, _) => {
 191                 self.in_binary_expr = true
 192             },
 193             _ => {},
 194         }
 195
 196         walk_expr(self, expr);
 197     }
 198     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 199         NestedVisitorMap::None
 200     }
 201 }