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::get_enclosing_block;
   3 use clippy_utils::macros::{find_assert_eq_args, first_node_macro_backtrace};
   4 use clippy_utils::source::snippet;
   5 use clippy_utils::ty::{implements_trait, is_copy};
   6 use clippy_utils::{ast_utils::is_useless_with_eq_exprs, eq_expr_value, is_in_test_function};
   7 use if_chain::if_chain;
   8 use rustc_errors::Applicability;
   9 use rustc_hir::{def::Res, def_id::DefId, BinOpKind, BorrowKind, Expr, ExprKind, GenericArg, ItemKind, QPath, TyKind};
  10 use rustc_lint::{LateContext, LateLintPass};
  11 use rustc_middle::ty::{self, Ty};
  12 use rustc_session::{declare_lint_pass, declare_tool_lint};
  13
  14 declare_clippy_lint! {
  15     /// ### What it does
  16     /// Checks for equal operands to comparison, logical and
  17     /// bitwise, difference and division binary operators (`==`, `>`, etc., `&&`,
  18     /// `||`, `&`, `|`, `^`, `-` and `/`).
  19     ///
  20     /// ### Why is this bad?
  21     /// This is usually just a typo or a copy and paste error.
  22     ///
  23     /// ### Known problems
  24     /// False negatives: We had some false positives regarding
  25     /// calls (notably [racer](https://github.com/phildawes/racer) had one instance
  26     /// of `x.pop() && x.pop()`), so we removed matching any function or method
  27     /// calls. We may introduce a list of known pure functions in the future.
  28     ///
  29     /// ### Example
  30     /// ```rust
  31     /// # let x = 1;
  32     /// if x + 1 == x + 1 {}
  33     ///
  34     /// // or
  35     ///
  36     /// # let a = 3;
  37     /// # let b = 4;
  38     /// assert_eq!(a, a);
  39     /// ```
  40     #[clippy::version = "pre 1.29.0"]
  41     pub EQ_OP,
  42     correctness,
  43     "equal operands on both sides of a comparison or bitwise combination (e.g., `x == x`)"
  44 }
  45
  46 declare_clippy_lint! {
  47     /// ### What it does
  48     /// Checks for arguments to `==` which have their address
  49     /// taken to satisfy a bound
  50     /// and suggests to dereference the other argument instead
  51     ///
  52     /// ### Why is this bad?
  53     /// It is more idiomatic to dereference the other argument.
  54     ///
  55     /// ### Example
  56     /// ```rust,ignore
  57     /// &x == y
  58     /// ```
  59     ///
  60     /// Use instead:
  61     /// ```rust,ignore
  62     /// x == *y
  63     /// ```
  64     #[clippy::version = "pre 1.29.0"]
  65     pub OP_REF,
  66     style,
  67     "taking a reference to satisfy the type constraints on `==`"
  68 }
  69
  70 declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);
  71
  72 impl<'tcx> LateLintPass<'tcx> for EqOp {
  73     #[expect(clippy::similar_names, clippy::too_many_lines)]
  74     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  75         if_chain! {
  76             if let Some((macro_call, macro_name)) = first_node_macro_backtrace(cx, e).find_map(|macro_call| {
  77                 let name = cx.tcx.item_name(macro_call.def_id);
  78                 matches!(name.as_str(), "assert_eq" | "assert_ne" | "debug_assert_eq" | "debug_assert_ne")
  79                     .then(|| (macro_call, name))
  80             });
  81             if let Some((lhs, rhs, _)) = find_assert_eq_args(cx, e, macro_call.expn);
  82             if eq_expr_value(cx, lhs, rhs);
  83             if macro_call.is_local();
  84             if !is_in_test_function(cx.tcx, e.hir_id);
  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", macro_name),
  91                 );
  92             }
  93         }
  94         if let ExprKind::Binary(op, left, right) = e.kind {
  95             if e.span.from_expansion() {
  96                 return;
  97             }
  98             let macro_with_not_op = |expr_kind: &ExprKind<'_>| {
  99                 if let ExprKind::Unary(_, expr) = *expr_kind {
 100                     expr.span.from_expansion()
 101                 } else {
 102                     false
 103                 }
 104             };
 105             if macro_with_not_op(&left.kind) || macro_with_not_op(&right.kind) {
 106                 return;
 107             }
 108             if is_useless_with_eq_exprs(op.node.into())
 109                 && eq_expr_value(cx, left, right)
 110                 && !is_in_test_function(cx.tcx, e.hir_id)
 111             {
 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                 match (&left.kind, &right.kind) {
 140                     // do not suggest to dereference literals
 141                     (&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
 142                     // &foo == &bar
 143                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 144                         let lty = cx.typeck_results().expr_ty(l);
 145                         let rty = cx.typeck_results().expr_ty(r);
 146                         let lcpy = is_copy(cx, lty);
 147                         let rcpy = is_copy(cx, rty);
 148                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 149                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 150                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 151                             {
 152                                 return; // Don't lint
 153                             }
 154                         }
 155                         // either operator autorefs or both args are copyable
 156                         if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
 157                             span_lint_and_then(
 158                                 cx,
 159                                 OP_REF,
 160                                 e.span,
 161                                 "needlessly taken reference of both operands",
 162                                 |diag| {
 163                                     let lsnip = snippet(cx, l.span, "...").to_string();
 164                                     let rsnip = snippet(cx, r.span, "...").to_string();
 165                                     multispan_sugg(
 166                                         diag,
 167                                         "use the values directly",
 168                                         vec![(left.span, lsnip), (right.span, rsnip)],
 169                                     );
 170                                 },
 171                             );
 172                         } else if lcpy
 173                             && !rcpy
 174                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 175                         {
 176                             span_lint_and_then(
 177                                 cx,
 178                                 OP_REF,
 179                                 e.span,
 180                                 "needlessly taken reference of left operand",
 181                                 |diag| {
 182                                     let lsnip = snippet(cx, l.span, "...").to_string();
 183                                     diag.span_suggestion(
 184                                         left.span,
 185                                         "use the left value directly",
 186                                         lsnip,
 187                                         Applicability::MaybeIncorrect, // FIXME #2597
 188                                     );
 189                                 },
 190                             );
 191                         } else if !lcpy
 192                             && rcpy
 193                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 194                         {
 195                             span_lint_and_then(
 196                                 cx,
 197                                 OP_REF,
 198                                 e.span,
 199                                 "needlessly taken reference of right operand",
 200                                 |diag| {
 201                                     let rsnip = snippet(cx, r.span, "...").to_string();
 202                                     diag.span_suggestion(
 203                                         right.span,
 204                                         "use the right value directly",
 205                                         rsnip,
 206                                         Applicability::MaybeIncorrect, // FIXME #2597
 207                                     );
 208                                 },
 209                             );
 210                         }
 211                     },
 212                     // &foo == bar
 213                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
 214                         let lty = cx.typeck_results().expr_ty(l);
 215                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 216                             let rty = cx.typeck_results().expr_ty(right);
 217                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 218                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 219                             {
 220                                 return; // Don't lint
 221                             }
 222                         }
 223                         let lcpy = is_copy(cx, lty);
 224                         if (requires_ref || lcpy)
 225                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 226                         {
 227                             span_lint_and_then(
 228                                 cx,
 229                                 OP_REF,
 230                                 e.span,
 231                                 "needlessly taken reference of left operand",
 232                                 |diag| {
 233                                     let lsnip = snippet(cx, l.span, "...").to_string();
 234                                     diag.span_suggestion(
 235                                         left.span,
 236                                         "use the left value directly",
 237                                         lsnip,
 238                                         Applicability::MaybeIncorrect, // FIXME #2597
 239                                     );
 240                                 },
 241                             );
 242                         }
 243                     },
 244                     // foo == &bar
 245                     (_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 246                         let rty = cx.typeck_results().expr_ty(r);
 247                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 248                             let lty = cx.typeck_results().expr_ty(left);
 249                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 250                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 251                             {
 252                                 return; // Don't lint
 253                             }
 254                         }
 255                         let rcpy = is_copy(cx, rty);
 256                         if (requires_ref || rcpy)
 257                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 258                         {
 259                             span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
 260                                 let rsnip = snippet(cx, r.span, "...").to_string();
 261                                 diag.span_suggestion(
 262                                     right.span,
 263                                     "use the right value directly",
 264                                     rsnip,
 265                                     Applicability::MaybeIncorrect, // FIXME #2597
 266                                 );
 267                             });
 268                         }
 269                     },
 270                     _ => {},
 271                 }
 272             }
 273         }
 274     }
 275 }
 276
 277 fn in_impl<'tcx>(
 278     cx: &LateContext<'tcx>,
 279     e: &'tcx Expr<'_>,
 280     bin_op: DefId,
 281 ) -> Option<(&'tcx rustc_hir::Ty<'tcx>, &'tcx rustc_hir::Ty<'tcx>)> {
 282     if_chain! {
 283         if let Some(block) = get_enclosing_block(cx, e.hir_id);
 284         if let Some(impl_def_id) = cx.tcx.impl_of_method(block.hir_id.owner.to_def_id());
 285         let item = cx.tcx.hir().expect_item(impl_def_id.expect_local());
 286         if let ItemKind::Impl(item) = &item.kind;
 287         if let Some(of_trait) = &item.of_trait;
 288         if let Some(seg) = of_trait.path.segments.last();
 289         if let Some(Res::Def(_, trait_id)) = seg.res;
 290         if trait_id == bin_op;
 291         if let Some(generic_args) = seg.args;
 292         if let Some(GenericArg::Type(other_ty)) = generic_args.args.last();
 293
 294         then {
 295             Some((item.self_ty, other_ty))
 296         }
 297         else {
 298             None
 299         }
 300     }
 301 }
 302
 303 fn are_equal<'tcx>(cx: &LateContext<'tcx>, middle_ty: Ty<'_>, hir_ty: &rustc_hir::Ty<'_>) -> bool {
 304     if_chain! {
 305         if let ty::Adt(adt_def, _) = middle_ty.kind();
 306         if let Some(local_did) = adt_def.did().as_local();
 307         let item = cx.tcx.hir().expect_item(local_did);
 308         let middle_ty_id = item.def_id.to_def_id();
 309         if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind;
 310         if let Res::Def(_, hir_ty_id) = path.res;
 311
 312         then {
 313             hir_ty_id == middle_ty_id
 314         }
 315         else {
 316             false
 317         }
 318     }
 319 }