clippy_lints/src/suspicious_trait_impl.rs

   1 use crate::utils::{get_trait_def_id, span_lint, trait_ref_of_method};
   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_lint_pass, declare_tool_lint};
   7
   8 declare_clippy_lint! {
   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     /// ```ignore
  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     pub SUSPICIOUS_ARITHMETIC_IMPL,
  27     correctness,
  28     "suspicious use of operators in impl of arithmetic trait"
  29 }
  30
  31 declare_clippy_lint! {
  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     /// ```ignore
  41     /// impl AddAssign for Foo {
  42     ///     fn add_assign(&mut self, other: Foo) {
  43     ///         *self = *self - other;
  44     ///     }
  45     /// }
  46     /// ```
  47     pub SUSPICIOUS_OP_ASSIGN_IMPL,
  48     correctness,
  49     "suspicious use of operators in impl of OpAssign trait"
  50 }
  51
  52 declare_lint_pass!(SuspiciousImpl => [SUSPICIOUS_ARITHMETIC_IMPL, SUSPICIOUS_OP_ASSIGN_IMPL]);
  53
  54 impl<'a, 'tcx> LateLintPass<'a, 'tcx> for SuspiciousImpl {
  55     fn check_expr(&mut self, cx: &LateContext<'a, 'tcx>, expr: &'tcx hir::Expr) {
  56         if let hir::ExprKind::Binary(binop, _, _) = expr.node {
  57             match binop.node {
  58                 hir::BinOpKind::Eq
  59                 | hir::BinOpKind::Lt
  60                 | hir::BinOpKind::Le
  61                 | hir::BinOpKind::Ne
  62                 | hir::BinOpKind::Ge
  63                 | hir::BinOpKind::Gt => return,
  64                 _ => {},
  65             }
  66             // Check if the binary expression is part of another bi/unary expression
  67             // as a child node
  68             let mut parent_expr = cx.tcx.hir().get_parent_node_by_hir_id(expr.hir_id);
  69             while parent_expr != hir::CRATE_HIR_ID {
  70                 if let hir::Node::Expr(e) = cx.tcx.hir().get_by_hir_id(parent_expr) {
  71                     match e.node {
  72                         hir::ExprKind::Binary(..)
  73                         | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
  74                         | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => return,
  75                         _ => {},
  76                     }
  77                 }
  78                 parent_expr = cx.tcx.hir().get_parent_node_by_hir_id(parent_expr);
  79             }
  80             // as a parent node
  81             let mut visitor = BinaryExprVisitor { in_binary_expr: false };
  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                 &[
  94                     hir::BinOpKind::Add,
  95                     hir::BinOpKind::Sub,
  96                     hir::BinOpKind::Mul,
  97                     hir::BinOpKind::Div,
  98                 ],
  99             ) {
 100                 span_lint(
 101                     cx,
 102                     SUSPICIOUS_ARITHMETIC_IMPL,
 103                     binop.span,
 104                     &format!(r#"Suspicious use of binary operator in `{}` impl"#, impl_trait),
 105                 );
 106             }
 107
 108             if let Some(impl_trait) = check_binop(
 109                 cx,
 110                 expr,
 111                 binop.node,
 112                 &[
 113                     "AddAssign",
 114                     "SubAssign",
 115                     "MulAssign",
 116                     "DivAssign",
 117                     "BitAndAssign",
 118                     "BitOrAssign",
 119                     "BitXorAssign",
 120                     "RemAssign",
 121                     "ShlAssign",
 122                     "ShrAssign",
 123                 ],
 124                 &[
 125                     hir::BinOpKind::Add,
 126                     hir::BinOpKind::Sub,
 127                     hir::BinOpKind::Mul,
 128                     hir::BinOpKind::Div,
 129                     hir::BinOpKind::BitAnd,
 130                     hir::BinOpKind::BitOr,
 131                     hir::BinOpKind::BitXor,
 132                     hir::BinOpKind::Rem,
 133                     hir::BinOpKind::Shl,
 134                     hir::BinOpKind::Shr,
 135                 ],
 136             ) {
 137                 span_lint(
 138                     cx,
 139                     SUSPICIOUS_OP_ASSIGN_IMPL,
 140                     binop.span,
 141                     &format!(r#"Suspicious use of binary operator in `{}` impl"#, impl_trait),
 142                 );
 143             }
 144         }
 145     }
 146 }
 147
 148 fn check_binop<'a>(
 149     cx: &LateContext<'_, '_>,
 150     expr: &hir::Expr,
 151     binop: hir::BinOpKind,
 152     traits: &[&'a str],
 153     expected_ops: &[hir::BinOpKind],
 154 ) -> Option<&'a str> {
 155     let mut trait_ids = vec![];
 156     let [krate, module] = crate::utils::paths::OPS_MODULE;
 157
 158     for t in traits {
 159         let path = [krate, module, t];
 160         if let Some(trait_id) = get_trait_def_id(cx, &path) {
 161             trait_ids.push(trait_id);
 162         } else {
 163             return None;
 164         }
 165     }
 166
 167     // Get the actually implemented trait
 168     let parent_fn = cx.tcx.hir().get_parent_item(expr.hir_id);
 169
 170     if_chain! {
 171         if let Some(trait_ref) = trait_ref_of_method(cx, parent_fn);
 172         if let Some(idx) = trait_ids.iter().position(|&tid| tid == trait_ref.path.def.def_id());
 173         if binop != expected_ops[idx];
 174         then{
 175             return Some(traits[idx])
 176         }
 177     }
 178
 179     None
 180 }
 181
 182 struct BinaryExprVisitor {
 183     in_binary_expr: bool,
 184 }
 185
 186 impl<'a, 'tcx: 'a> Visitor<'tcx> for BinaryExprVisitor {
 187     fn visit_expr(&mut self, expr: &'tcx hir::Expr) {
 188         match expr.node {
 189             hir::ExprKind::Binary(..)
 190             | hir::ExprKind::Unary(hir::UnOp::UnNot, _)
 191             | hir::ExprKind::Unary(hir::UnOp::UnNeg, _) => self.in_binary_expr = true,
 192             _ => {},
 193         }
 194
 195         walk_expr(self, expr);
 196     }
 197     fn nested_visit_map<'this>(&'this mut self) -> NestedVisitorMap<'this, 'tcx> {
 198         NestedVisitorMap::None
 199     }
 200 }