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     /// ```rust
  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     /// ### Known problems
  56     /// None
  57     ///
  58     /// ### Example
  59     /// ```ignore
  60     /// // Bad
  61     /// &x == y
  62     ///
  63     /// // Good
  64     /// x == *y
  65     /// ```
  66     #[clippy::version = "pre 1.29.0"]
  67     pub OP_REF,
  68     style,
  69     "taking a reference to satisfy the type constraints on `==`"
  70 }
  71
  72 declare_lint_pass!(EqOp => [EQ_OP, OP_REF]);
  73
  74 impl<'tcx> LateLintPass<'tcx> for EqOp {
  75     #[allow(clippy::similar_names, clippy::too_many_lines)]
  76     fn check_expr(&mut self, cx: &LateContext<'tcx>, e: &'tcx Expr<'_>) {
  77         if_chain! {
  78             if let Some((macro_call, macro_name)) = first_node_macro_backtrace(cx, e).find_map(|macro_call| {
  79                 let name = cx.tcx.item_name(macro_call.def_id);
  80                 matches!(name.as_str(), "assert_eq" | "assert_ne" | "debug_assert_eq" | "debug_assert_ne")
  81                     .then(|| (macro_call, name))
  82             });
  83             if let Some((lhs, rhs, _)) = find_assert_eq_args(cx, e, macro_call.expn);
  84             if eq_expr_value(cx, lhs, rhs);
  85             if macro_call.is_local();
  86             if !is_in_test_function(cx.tcx, e.hir_id);
  87             then {
  88                 span_lint(
  89                     cx,
  90                     EQ_OP,
  91                     lhs.span.to(rhs.span),
  92                     &format!("identical args used in this `{}!` macro call", macro_name),
  93                 );
  94             }
  95         }
  96         if let ExprKind::Binary(op, left, right) = e.kind {
  97             if e.span.from_expansion() {
  98                 return;
  99             }
 100             let macro_with_not_op = |expr_kind: &ExprKind<'_>| {
 101                 if let ExprKind::Unary(_, expr) = *expr_kind {
 102                     expr.span.from_expansion()
 103                 } else {
 104                     false
 105                 }
 106             };
 107             if macro_with_not_op(&left.kind) || macro_with_not_op(&right.kind) {
 108                 return;
 109             }
 110             if is_useless_with_eq_exprs(op.node.into())
 111                 && eq_expr_value(cx, left, right)
 112                 && !is_in_test_function(cx.tcx, e.hir_id)
 113             {
 114                 span_lint(
 115                     cx,
 116                     EQ_OP,
 117                     e.span,
 118                     &format!("equal expressions as operands to `{}`", op.node.as_str()),
 119                 );
 120                 return;
 121             }
 122             let (trait_id, requires_ref) = match op.node {
 123                 BinOpKind::Add => (cx.tcx.lang_items().add_trait(), false),
 124                 BinOpKind::Sub => (cx.tcx.lang_items().sub_trait(), false),
 125                 BinOpKind::Mul => (cx.tcx.lang_items().mul_trait(), false),
 126                 BinOpKind::Div => (cx.tcx.lang_items().div_trait(), false),
 127                 BinOpKind::Rem => (cx.tcx.lang_items().rem_trait(), false),
 128                 // don't lint short circuiting ops
 129                 BinOpKind::And | BinOpKind::Or => return,
 130                 BinOpKind::BitXor => (cx.tcx.lang_items().bitxor_trait(), false),
 131                 BinOpKind::BitAnd => (cx.tcx.lang_items().bitand_trait(), false),
 132                 BinOpKind::BitOr => (cx.tcx.lang_items().bitor_trait(), false),
 133                 BinOpKind::Shl => (cx.tcx.lang_items().shl_trait(), false),
 134                 BinOpKind::Shr => (cx.tcx.lang_items().shr_trait(), false),
 135                 BinOpKind::Ne | BinOpKind::Eq => (cx.tcx.lang_items().eq_trait(), true),
 136                 BinOpKind::Lt | BinOpKind::Le | BinOpKind::Ge | BinOpKind::Gt => {
 137                     (cx.tcx.lang_items().partial_ord_trait(), true)
 138                 },
 139             };
 140             if let Some(trait_id) = trait_id {
 141                 #[allow(clippy::match_same_arms)]
 142                 match (&left.kind, &right.kind) {
 143                     // do not suggest to dereference literals
 144                     (&ExprKind::Lit(..), _) | (_, &ExprKind::Lit(..)) => {},
 145                     // &foo == &bar
 146                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 147                         let lty = cx.typeck_results().expr_ty(l);
 148                         let rty = cx.typeck_results().expr_ty(r);
 149                         let lcpy = is_copy(cx, lty);
 150                         let rcpy = is_copy(cx, rty);
 151                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 152                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 153                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 154                             {
 155                                 return; // Don't lint
 156                             }
 157                         }
 158                         // either operator autorefs or both args are copyable
 159                         if (requires_ref || (lcpy && rcpy)) && implements_trait(cx, lty, trait_id, &[rty.into()]) {
 160                             span_lint_and_then(
 161                                 cx,
 162                                 OP_REF,
 163                                 e.span,
 164                                 "needlessly taken reference of both operands",
 165                                 |diag| {
 166                                     let lsnip = snippet(cx, l.span, "...").to_string();
 167                                     let rsnip = snippet(cx, r.span, "...").to_string();
 168                                     multispan_sugg(
 169                                         diag,
 170                                         "use the values directly",
 171                                         vec![(left.span, lsnip), (right.span, rsnip)],
 172                                     );
 173                                 },
 174                             );
 175                         } else if lcpy
 176                             && !rcpy
 177                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 178                         {
 179                             span_lint_and_then(
 180                                 cx,
 181                                 OP_REF,
 182                                 e.span,
 183                                 "needlessly taken reference of left operand",
 184                                 |diag| {
 185                                     let lsnip = snippet(cx, l.span, "...").to_string();
 186                                     diag.span_suggestion(
 187                                         left.span,
 188                                         "use the left value directly",
 189                                         lsnip,
 190                                         Applicability::MaybeIncorrect, // FIXME #2597
 191                                     );
 192                                 },
 193                             );
 194                         } else if !lcpy
 195                             && rcpy
 196                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 197                         {
 198                             span_lint_and_then(
 199                                 cx,
 200                                 OP_REF,
 201                                 e.span,
 202                                 "needlessly taken reference of right operand",
 203                                 |diag| {
 204                                     let rsnip = snippet(cx, r.span, "...").to_string();
 205                                     diag.span_suggestion(
 206                                         right.span,
 207                                         "use the right value directly",
 208                                         rsnip,
 209                                         Applicability::MaybeIncorrect, // FIXME #2597
 210                                     );
 211                                 },
 212                             );
 213                         }
 214                     },
 215                     // &foo == bar
 216                     (&ExprKind::AddrOf(BorrowKind::Ref, _, l), _) => {
 217                         let lty = cx.typeck_results().expr_ty(l);
 218                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 219                             let rty = cx.typeck_results().expr_ty(right);
 220                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 221                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 222                             {
 223                                 return; // Don't lint
 224                             }
 225                         }
 226                         let lcpy = is_copy(cx, lty);
 227                         if (requires_ref || lcpy)
 228                             && implements_trait(cx, lty, trait_id, &[cx.typeck_results().expr_ty(right).into()])
 229                         {
 230                             span_lint_and_then(
 231                                 cx,
 232                                 OP_REF,
 233                                 e.span,
 234                                 "needlessly taken reference of left operand",
 235                                 |diag| {
 236                                     let lsnip = snippet(cx, l.span, "...").to_string();
 237                                     diag.span_suggestion(
 238                                         left.span,
 239                                         "use the left value directly",
 240                                         lsnip,
 241                                         Applicability::MaybeIncorrect, // FIXME #2597
 242                                     );
 243                                 },
 244                             );
 245                         }
 246                     },
 247                     // foo == &bar
 248                     (_, &ExprKind::AddrOf(BorrowKind::Ref, _, r)) => {
 249                         let rty = cx.typeck_results().expr_ty(r);
 250                         if let Some((self_ty, other_ty)) = in_impl(cx, e, trait_id) {
 251                             let lty = cx.typeck_results().expr_ty(left);
 252                             if (are_equal(cx, rty, self_ty) && are_equal(cx, lty, other_ty))
 253                                 || (are_equal(cx, rty, other_ty) && are_equal(cx, lty, self_ty))
 254                             {
 255                                 return; // Don't lint
 256                             }
 257                         }
 258                         let rcpy = is_copy(cx, rty);
 259                         if (requires_ref || rcpy)
 260                             && implements_trait(cx, cx.typeck_results().expr_ty(left), trait_id, &[rty.into()])
 261                         {
 262                             span_lint_and_then(cx, OP_REF, e.span, "taken reference of right operand", |diag| {
 263                                 let rsnip = snippet(cx, r.span, "...").to_string();
 264                                 diag.span_suggestion(
 265                                     right.span,
 266                                     "use the right value directly",
 267                                     rsnip,
 268                                     Applicability::MaybeIncorrect, // FIXME #2597
 269                                 );
 270                             });
 271                         }
 272                     },
 273                     _ => {},
 274                 }
 275             }
 276         }
 277     }
 278 }
 279
 280 fn in_impl<'tcx>(
 281     cx: &LateContext<'tcx>,
 282     e: &'tcx Expr<'_>,
 283     bin_op: DefId,
 284 ) -> Option<(&'tcx rustc_hir::Ty<'tcx>, &'tcx rustc_hir::Ty<'tcx>)> {
 285     if_chain! {
 286         if let Some(block) = get_enclosing_block(cx, e.hir_id);
 287         if let Some(impl_def_id) = cx.tcx.impl_of_method(block.hir_id.owner.to_def_id());
 288         let item = cx.tcx.hir().expect_item(impl_def_id.expect_local());
 289         if let ItemKind::Impl(item) = &item.kind;
 290         if let Some(of_trait) = &item.of_trait;
 291         if let Some(seg) = of_trait.path.segments.last();
 292         if let Some(Res::Def(_, trait_id)) = seg.res;
 293         if trait_id == bin_op;
 294         if let Some(generic_args) = seg.args;
 295         if let Some(GenericArg::Type(other_ty)) = generic_args.args.last();
 296
 297         then {
 298             Some((item.self_ty, other_ty))
 299         }
 300         else {
 301             None
 302         }
 303     }
 304 }
 305
 306 fn are_equal<'tcx>(cx: &LateContext<'tcx>, middle_ty: Ty<'_>, hir_ty: &rustc_hir::Ty<'_>) -> bool {
 307     if_chain! {
 308         if let ty::Adt(adt_def, _) = middle_ty.kind();
 309         if let Some(local_did) = adt_def.did().as_local();
 310         let item = cx.tcx.hir().expect_item(local_did);
 311         let middle_ty_id = item.def_id.to_def_id();
 312         if let TyKind::Path(QPath::Resolved(_, path)) = hir_ty.kind;
 313         if let Res::Def(_, hir_ty_id) = path.res;
 314
 315         then {
 316             hir_ty_id == middle_ty_id
 317         }
 318         else {
 319             false
 320         }
 321     }
 322 }