src/tools/clippy/clippy_lints/src/eq_op.rs

   1 use clippy_utils::diagnostics::{multispan_sugg, span_lint, span_lint_and_then};
   2 use clippy_utils::source::snippet;
   3 use clippy_utils::ty::{implements_trait, is_copy};
   4 use clippy_utils::{ast_utils::is_useless_with_eq_exprs, eq_expr_value, higher, in_macro, is_expn_of};
   5 use if_chain::if_chain;
   6 use rustc_errors::Applicability;
   7 use rustc_hir::{BinOpKind, BorrowKind, Expr, ExprKind, StmtKind};
   8 use rustc_lint::{LateContext, LateLintPass};
   9 use rustc_session::{declare_lint_pass, declare_tool_lint};
  10
  11 declare_clippy_lint! {
  12     /// ### What it does
  13     /// Checks for equal operands to comparison, logical and
  14     /// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
  15     /// `||`, `&`, `|`, `^`, `-` and `/`).
  16     ///
  17     /// ### Why is this bad?
  18     /// This is usually just a typo or a copy and paste error.
  19     ///
  20     /// ### Known problems
  21     /// False negatives: We had some false positives regarding
  22     /// calls (notably [racer](https://github.com/phildawes/racer) had one instance
  23     /// of `x.pop() && x.pop()`), so we removed matching any function or method
  24     /// calls. We may introduce a list of known pure functions in the future.
  25     ///
  26     /// ### Example
  27     /// ```rust
  28     /// # let x = 1;
  29     /// if x + 1 == x + 1 {}
  30     /// ```
  31     /// or
  32     /// ```rust
  33     /// # let a = 3;
  34     /// # let b = 4;
  35     /// assert_eq!(a, a);
  36     /// ```
  37     pub EQ_OP,
  38     correctness,
  39     "equal operands on both sides of a comparison or bitwise combination (e.g., `x == x`)"
  40 }
  41
  42 declare_clippy_lint! {
  43     /// ### What it does
  44     /// Checks for arguments to `==` which have their address
  45     /// taken to satisfy a bound
  46     /// and suggests to dereference the other argument instead
  47     ///
  48     /// ### Why is this bad?
  49     /// It is more idiomatic to dereference the other argument.
  50     ///
  51     /// ### Known problems
  52     /// None
  53     ///
  54     /// ### Example
  55     /// ```ignore
  56     /// // Bad
  57     /// &x == y
  58     ///
  59     /// // Good
  60     /// x == *y
  61     /// ```
  62     pub OP_REF,
  63     style,
  64     "taking a reference to satisfy the type constraints on `==`"
  65 }
  66
  67 declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);
  68
  69 const ASSERT_MACRO_NAMES: [&str; 4] = ["assert_eq", "assert_ne", "debug_assert_eq", "debug_assert_ne"];
  70
  71 impl<'tcx> LateLintPass<'tcx> for EqOp {
  72     #[allow(clippy::similar_names, clippy::too_many_lines)]
  73     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  74         if let ExprKind::Block(block, _) = e.kind {
  75             for stmt in block.stmts {
  76                 for amn in &ASSERT_MACRO_NAMES {
  77                     if_chain! {
  78                         if is_expn_of(stmt.span, amn).is_some();
  79                         if let StmtKind::Semi(matchexpr) = stmt.kind;
  80                         if let Some(macro_args) = higher::extract_assert_macro_args(matchexpr);
  81                         if macro_args.len() == 2;
  82                         let (lhs, rhs) = (macro_args[0], macro_args[1]);
  83                         if eq_expr_value(cx, lhs, rhs);
  84
  85                         then {
  86                             span_lint(
  87                                 cx,
  88                                 EQ_OP,
  89                                 lhs.span.to(rhs.span),
  90                                 &format!("identical args used in this `{}!` macro call", amn),
  91                             );
  92                         }
  93                     }
  94                 }
  95             }
  96         }
  97         if let ExprKind::Binary(op, left, right) = e.kind {
  98             if e.span.from_expansion() {
  99                 return;
 100             }
 101             let macro_with_not_op = |expr_kind: &ExprKind<'_>| {
 102                 if let ExprKind::Unary(_, expr) = *expr_kind {
 103                     in_macro(expr.span)
 104                 } else {
 105                     false
 106                 }
 107             };
 108             if macro_with_not_op(&left.kind) || macro_with_not_op(&right.kind) {
 109                 return;
 110             }
 111             if is_useless_with_eq_exprs(op.node.into()) && eq_expr_value(cx, left, right) {
 112                 span_lint(
 113                     cx,
 114                     EQ_OP,
 115                     e.span,
 116                     &format!("equal expressions as operands to `{}`", op.node.as_str()),
 117                 );
 118                 return;
 119             }
 120             let (trait_id, requires_ref) = match op.node {
 121                 BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
 122                 BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
 123                 BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
 124                 BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
 125                 BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
 126                 // don't lint short circuiting ops
 127                 BinOpKind::And | BinOpKind::Or => return,
 128                 BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
 129                 BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
 130                 BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
 131                 BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
 132                 BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
 133                 BinOpKind::Ne | BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
 134                 BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ge | BinOpKind::Gt => {
 135                     (cx.tcx.lang_items().partial_ord_trait(), true)
 136                 },
 137             };
 138             if let Some(trait_id) = trait_id {
 139                 #[allow(clippy::match_same_arms)]
 140                 match (&left.kind, &right.kind) {
 141                     // do not suggest to dereference literals
 142                     (&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
 143                     // &foo == &bar
 144                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 145                         let lty = cx.typeck_results().expr_ty(l);
 146                         let rty = cx.typeck_results().expr_ty(r);
 147                         let lcpy = is_copy(cx, lty);
 148                         let rcpy = is_copy(cx, rty);
 149                         // either operator autorefs or both args are copyable
 150                         if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
 151                             span_lint_and_then(
 152                                 cx,
 153                                 OP_REF,
 154                                 e.span,
 155                                 "needlessly taken reference of both operands",
 156                                 |diag| {
 157                                     let lsnip = snippet(cx, l.span, "...").to_string();
 158                                     let rsnip = snippet(cx, r.span, "...").to_string();
 159                                     multispan_sugg(
 160                                         diag,
 161                                         "use the values directly",
 162                                         vec![(left.span, lsnip), (right.span, rsnip)],
 163                                     );
 164                                 },
 165                             );
 166                         } else if lcpy
 167                             && !rcpy
 168                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 169                         {
 170                             span_lint_and_then(
 171                                 cx,
 172                                 OP_REF,
 173                                 e.span,
 174                                 "needlessly taken reference of left operand",
 175                                 |diag| {
 176                                     let lsnip = snippet(cx, l.span, "...").to_string();
 177                                     diag.span_suggestion(
 178                                         left.span,
 179                                         "use the left value directly",
 180                                         lsnip,
 181                                         Applicability::MaybeIncorrect, // FIXME #2597
 182                                     );
 183                                 },
 184                             );
 185                         } else if !lcpy
 186                             && rcpy
 187                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 188                         {
 189                             span_lint_and_then(
 190                                 cx,
 191                                 OP_REF,
 192                                 e.span,
 193                                 "needlessly taken reference of right operand",
 194                                 |diag| {
 195                                     let rsnip = snippet(cx, r.span, "...").to_string();
 196                                     diag.span_suggestion(
 197                                         right.span,
 198                                         "use the right value directly",
 199                                         rsnip,
 200                                         Applicability::MaybeIncorrect, // FIXME #2597
 201                                     );
 202                                 },
 203                             );
 204                         }
 205                     },
 206                     // &foo == bar
 207                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
 208                         let lty = cx.typeck_results().expr_ty(l);
 209                         let lcpy = is_copy(cx, lty);
 210                         if (requires_ref || lcpy)
 211                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 212                         {
 213                             span_lint_and_then(
 214                                 cx,
 215                                 OP_REF,
 216                                 e.span,
 217                                 "needlessly taken reference of left operand",
 218                                 |diag| {
 219                                     let lsnip = snippet(cx, l.span, "...").to_string();
 220                                     diag.span_suggestion(
 221                                         left.span,
 222                                         "use the left value directly",
 223                                         lsnip,
 224                                         Applicability::MaybeIncorrect, // FIXME #2597
 225                                     );
 226                                 },
 227                             );
 228                         }
 229                     },
 230                     // foo == &bar
 231                     (_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 232                         let rty = cx.typeck_results().expr_ty(r);
 233                         let rcpy = is_copy(cx, rty);
 234                         if (requires_ref || rcpy)
 235                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 236                         {
 237                             span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
 238                                 let rsnip = snippet(cx, r.span, "...").to_string();
 239                                 diag.span_suggestion(
 240                                     right.span,
 241                                     "use the right value directly",
 242                                     rsnip,
 243                                     Applicability::MaybeIncorrect, // FIXME #2597
 244                                 );
 245                             });
 246                         }
 247                     },
 248                     _ => {},
 249                 }
 250             }
 251         }
 252     }
 253 }