clippy_lints/src/suspicious_trait_impl.rs

   1 use crate::utils::{get_trait_def_id, span_lint};
   2 use if_chain::if_chain;
   3 use rustc::hir;
   4 use rustc::hir::intravisit::{walk_expr, NestedVisitorMap, Visitor};
   5 use rustc::lint::{LateContext, LateLintPass, LintArray, LintPass};
   6 use rustc::{declare_tool_lint, lint_array};
   7 use syntax::ast;
   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 => return,
  72                 _ => {},
  73             }
  74             // Check if the binary expression is part of another bi/unary expression
  75             // as a child node
  76             let mut parent_expr = cx.tcx.hir().get_parent_node(expr.id);
  77             while parent_expr != ast::CRATE_NODE_ID {
  78                 if let hir::Node::Expr(e) = cx.tcx.hir().get(parent_expr) {
  79                     match e.node {
  80                         hir::ExprKind::Binary(..)
  81                         | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
  82                         | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => return,
  83                         _ => {},
  84                     }
  85                 }
  86                 parent_expr = cx.tcx.hir().get_parent_node(parent_expr);
  87             }
  88             // as a parent node
  89             let mut visitor = BinaryExprVisitor { in_binary_expr: false };
  90             walk_expr(&mut visitor, expr);
  91
  92             if visitor.in_binary_expr {
  93                 return;
  94             }
  95
  96             if let Some(impl_trait) = check_binop(
  97                 cx,
  98                 expr,
  99                 binop.node,
 100                 &["Add", "Sub", "Mul", "Div"],
 101                 &[
 102                     hir::BinOpKind::Add,
 103                     hir::BinOpKind::Sub,
 104                     hir::BinOpKind::Mul,
 105                     hir::BinOpKind::Div,
 106                 ],
 107             ) {
 108                 span_lint(
 109                     cx,
 110                     SUSPICIOUS_ARITHMETIC_IMPL,
 111                     binop.span,
 112                     &format!(r#"Suspicious use of binary operator in `{}` impl"#, impl_trait),
 113                 );
 114             }
 115
 116             if let Some(impl_trait) = check_binop(
 117                 cx,
 118                 expr,
 119                 binop.node,
 120                 &[
 121                     "AddAssign",
 122                     "SubAssign",
 123                     "MulAssign",
 124                     "DivAssign",
 125                     "BitAndAssign",
 126                     "BitOrAssign",
 127                     "BitXorAssign",
 128                     "RemAssign",
 129                     "ShlAssign",
 130                     "ShrAssign",
 131                 ],
 132                 &[
 133                     hir::BinOpKind::Add,
 134                     hir::BinOpKind::Sub,
 135                     hir::BinOpKind::Mul,
 136                     hir::BinOpKind::Div,
 137                     hir::BinOpKind::BitAnd,
 138                     hir::BinOpKind::BitOr,
 139                     hir::BinOpKind::BitXor,
 140                     hir::BinOpKind::Rem,
 141                     hir::BinOpKind::Shl,
 142                     hir::BinOpKind::Shr,
 143                 ],
 144             ) {
 145                 span_lint(
 146                     cx,
 147                     SUSPICIOUS_OP_ASSIGN_IMPL,
 148                     binop.span,
 149                     &format!(r#"Suspicious use of binary operator in `{}` impl"#, impl_trait),
 150                 );
 151             }
 152         }
 153     }
 154 }
 155
 156 fn check_binop<'a>(
 157     cx: &LateContext<'_, '_>,
 158     expr: &hir::Expr,
 159     binop: hir::BinOpKind,
 160     traits: &[&'a str],
 161     expected_ops: &[hir::BinOpKind],
 162 ) -> Option<&'a str> {
 163     let mut trait_ids = vec![];
 164     let [krate, module] = crate::utils::paths::OPS_MODULE;
 165
 166     for t in traits {
 167         let path = [krate, module, t];
 168         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 169             trait_ids.push(trait_id);
 170         } else {
 171             return None;
 172         }
 173     }
 174
 175     // Get the actually implemented trait
 176     let parent_fn = cx.tcx.hir().get_parent(expr.id);
 177     let parent_impl = cx.tcx.hir().get_parent(parent_fn);
 178
 179     if_chain! {
 180         if parent_impl != ast::CRATE_NODE_ID;
 181         if let hir::Node::Item(item) = cx.tcx.hir().get(parent_impl);
 182         if let hir::ItemKind::Impl(_, _, _, _, Some(ref trait_ref), _, _) = item.node;
 183         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
 184         if binop != expected_ops[idx];
 185         then{
 186             return Some(traits[idx])
 187         }
 188     }
 189
 190     None
 191 }
 192
 193 struct BinaryExprVisitor {
 194     in_binary_expr: bool,
 195 }
 196
 197 impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
 198     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 199         match expr.node {
 200             hir::ExprKind::Binary(..)
 201             | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
 202             | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => self.in_binary_expr = true,
 203             _ => {},
 204         }
 205
 206         walk_expr(self, expr);
 207     }
 208     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 209         NestedVisitorMap::None
 210     }
 211 }