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