clippy_lints/src/suspicious_trait_impl.rs

   1 use rustc::lint::*;
   2 use rustc::{declare_lint, lint_array};
   3 use if_chain::if_chain;
   4 use rustc::hir;
   5 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   6 use syntax::ast;
   7 use crate::utils::{get_trait_def_id, span_lint};
   8
   9 /// **What it does:** Lints for suspicious operations in impls of arithmetic operators, e.g.
  10 /// subtracting elements in an Add impl.
  11 ///
  12 /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  13 ///
  14 /// **Known problems:** None.
  15 ///
  16 /// **Example:**
  17 /// ```rust
  18 /// impl Add for Foo {
  19 ///     type Output = Foo;
  20 ///
  21 ///     fn add(self, other: Foo) -> Foo {
  22 ///         Foo(self.0 - other.0)
  23 ///     }
  24 /// }
  25 /// ```
  26 declare_clippy_lint! {
  27     pub SUSPICIOUS_ARITHMETIC_IMPL,
  28     correctness,
  29     "suspicious use of operators in impl of arithmetic trait"
  30 }
  31
  32 /// **What it does:** Lints for suspicious operations in impls of OpAssign, e.g.
  33 /// subtracting elements in an AddAssign impl.
  34 ///
  35 /// **Why this is bad?** This is probably a typo or copy-and-paste error and not intended.
  36 ///
  37 /// **Known problems:** None.
  38 ///
  39 /// **Example:**
  40 /// ```rust
  41 /// impl AddAssign for Foo {
  42 ///     fn add_assign(&mut self, other: Foo) {
  43 ///         *self = *self - other;
  44 ///     }
  45 /// }
  46 /// ```
  47 declare_clippy_lint! {
  48     pub SUSPICIOUS_OP_ASSIGN_IMPL,
  49     correctness,
  50     "suspicious use of operators in impl of OpAssign trait"
  51 }
  52
  53 #[derive(Copy, Clone)]
  54 pub struct SuspiciousImpl;
  55
  56 impl LintPass for SuspiciousImpl {
  57     fn get_lints(&self) -> LintArray {
  58         lint_array![SUSPICIOUS_ARITHMETIC_IMPL, SUSPICIOUS_OP_ASSIGN_IMPL]
  59     }
  60 }
  61
  62 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for SuspiciousImpl {
  63     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  64         if let hir::ExprKind::Binary(binop, _, _) = expr.node {
  65             match binop.node {
  66                 | hir::BinOpKind::Eq
  67                 | hir::BinOpKind::Lt
  68                 | hir::BinOpKind::Le
  69                 | hir::BinOpKind::Ne
  70                 | hir::BinOpKind::Ge
  71                 | hir::BinOpKind::Gt
  72                 => return,
  73                 _ => {},
  74             }
  75             // Check if the binary expression is part of another bi/unary expression
  76             // as a child node
  77             let mut parent_expr = cx.tcx.hir.get_parent_node(expr.id);
  78             while parent_expr != ast::CRATE_NODE_ID {
  79                 if let hir::map::Node::NodeExpr(e) = cx.tcx.hir.get(parent_expr) {
  80                     match e.node {
  81                         hir::ExprKind::Binary(..)
  82                         | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
  83                         | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => return,
  84                         _ => {},
  85                     }
  86                 }
  87                 parent_expr = cx.tcx.hir.get_parent_node(parent_expr);
  88             }
  89             // as a parent node
  90             let mut visitor = BinaryExprVisitor {
  91                 in_binary_expr: false,
  92             };
  93             walk_expr(&mut visitor, expr);
  94
  95             if visitor.in_binary_expr {
  96                 return;
  97             }
  98
  99             if let Some(impl_trait) = check_binop(
 100                 cx,
 101                 expr,
 102                 binop.node,
 103                 &["Add", "Sub", "Mul", "Div"],
 104                 &[
 105                     hir::BinOpKind::Add,
 106                     hir::BinOpKind::Sub,
 107                     hir::BinOpKind::Mul,
 108                     hir::BinOpKind::Div,
 109                 ],
 110             ) {
 111                 span_lint(
 112                     cx,
 113                     SUSPICIOUS_ARITHMETIC_IMPL,
 114                     binop.span,
 115                     &format!(
 116                         r#"Suspicious use of binary operator in `{}` impl"#,
 117                         impl_trait
 118                     ),
 119                 );
 120             }
 121
 122             if let Some(impl_trait) = check_binop(
 123                 cx,
 124                 expr,
 125                 binop.node,
 126                 &[
 127                     "AddAssign",
 128                     "SubAssign",
 129                     "MulAssign",
 130                     "DivAssign",
 131                     "BitAndAssign",
 132                     "BitOrAssign",
 133                     "BitXorAssign",
 134                     "RemAssign",
 135                     "ShlAssign",
 136                     "ShrAssign",
 137                 ],
 138                 &[
 139                     hir::BinOpKind::Add,
 140                     hir::BinOpKind::Sub,
 141                     hir::BinOpKind::Mul,
 142                     hir::BinOpKind::Div,
 143                     hir::BinOpKind::BitAnd,
 144                     hir::BinOpKind::BitOr,
 145                     hir::BinOpKind::BitXor,
 146                     hir::BinOpKind::Rem,
 147                     hir::BinOpKind::Shl,
 148                     hir::BinOpKind::Shr,
 149                 ],
 150             ) {
 151                 span_lint(
 152                     cx,
 153                     SUSPICIOUS_OP_ASSIGN_IMPL,
 154                     binop.span,
 155                     &format!(
 156                         r#"Suspicious use of binary operator in `{}` impl"#,
 157                         impl_trait
 158                     ),
 159                 );
 160             }
 161         }
 162     }
 163 }
 164
 165 fn check_binop<'a>(
 166     cx: &LateContext,
 167     expr: &hir::Expr,
 168     binop: hir::BinOpKind,
 169     traits: &[&'a str],
 170     expected_ops: &[hir::BinOpKind],
 171 ) -> Option<&'a str> {
 172     let mut trait_ids = vec![];
 173     let [krate, module] = crate::utils::paths::OPS_MODULE;
 174
 175     for t in traits {
 176         let path = [krate, module, t];
 177         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 178             trait_ids.push(trait_id);
 179         } else {
 180             return None;
 181         }
 182     }
 183
 184     // Get the actually implemented trait
 185     let parent_fn = cx.tcx.hir.get_parent(expr.id);
 186     let parent_impl = cx.tcx.hir.get_parent(parent_fn);
 187
 188     if_chain! {
 189         if parent_impl != ast::CRATE_NODE_ID;
 190         if let hir::map::Node::NodeItem(item) = cx.tcx.hir.get(parent_impl);
 191         if let hir::ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.node;
 192         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
 193         if binop != expected_ops[idx];
 194         then{
 195             return Some(traits[idx])
 196         }
 197     }
 198
 199     None
 200 }
 201
 202 struct BinaryExprVisitor {
 203     in_binary_expr: bool,
 204 }
 205
 206 impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
 207     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 208         match expr.node {
 209             hir::ExprKind::Binary(..)
 210             | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
 211             | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => {
 212                 self.in_binary_expr = true
 213             },
 214             _ => {},
 215         }
 216
 217         walk_expr(self, expr);
 218     }
 219     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 220         NestedVisitorMap::None
 221     }
 222 }