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