clippy_lints/src/ptr.rs

   1 //! Checks for usage of  `&Vec[_]` and `&String`.
   2
   3 use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then, span_lint_hir_and_then};
   4 use clippy_utils::source::snippet_opt;
   5 use clippy_utils::ty::expr_sig;
   6 use clippy_utils::visitors::contains_unsafe_block;
   7 use clippy_utils::{get_expr_use_or_unification_node, is_lint_allowed, path_def_id, path_to_local, paths};
   8 use if_chain::if_chain;
   9 use rustc_errors::{Applicability, MultiSpan};
  10 use rustc_hir::def_id::DefId;
  11 use rustc_hir::hir_id::HirIdMap;
  12 use rustc_hir::intravisit::{walk_expr, Visitor};
  13 use rustc_hir::{
  14     self as hir, AnonConst, BinOpKind, BindingAnnotation, Body, Expr, ExprKind, FnRetTy, FnSig, GenericArg,
  15     ImplItemKind, ItemKind, Lifetime, Mutability, Node, Param, PatKind, QPath, TraitFn, TraitItem, TraitItemKind,
  16     TyKind, Unsafety,
  17 };
  18 use rustc_infer::infer::TyCtxtInferExt;
  19 use rustc_infer::traits::{Obligation, ObligationCause};
  20 use rustc_lint::{LateContext, LateLintPass};
  21 use rustc_middle::hir::nested_filter;
  22 use rustc_middle::ty::{self, Binder, Clause, ExistentialPredicate, List, PredicateKind, Ty};
  23 use rustc_session::{declare_lint_pass, declare_tool_lint};
  24 use rustc_span::source_map::Span;
  25 use rustc_span::sym;
  26 use rustc_span::symbol::Symbol;
  27 use rustc_trait_selection::infer::InferCtxtExt as _;
  28 use rustc_trait_selection::traits::query::evaluate_obligation::InferCtxtExt as _;
  29 use std::fmt;
  30 use std::iter;
  31
  32 declare_clippy_lint! {
  33     /// ### What it does
  34     /// This lint checks for function arguments of type `&String`, `&Vec`,
  35     /// `&PathBuf`, and `Cow<_>`. It will also suggest you replace `.clone()` calls
  36     /// with the appropriate `.to_owned()`/`to_string()` calls.
  37     ///
  38     /// ### Why is this bad?
  39     /// Requiring the argument to be of the specific size
  40     /// makes the function less useful for no benefit; slices in the form of `&[T]`
  41     /// or `&str` usually suffice and can be obtained from other types, too.
  42     ///
  43     /// ### Known problems
  44     /// There may be `fn(&Vec)`-typed references pointing to your function.
  45     /// If you have them, you will get a compiler error after applying this lint's
  46     /// suggestions. You then have the choice to undo your changes or change the
  47     /// type of the reference.
  48     ///
  49     /// Note that if the function is part of your public interface, there may be
  50     /// other crates referencing it, of which you may not be aware. Carefully
  51     /// deprecate the function before applying the lint suggestions in this case.
  52     ///
  53     /// ### Example
  54     /// ```ignore
  55     /// fn foo(&Vec<u32>) { .. }
  56     /// ```
  57     ///
  58     /// Use instead:
  59     /// ```ignore
  60     /// fn foo(&[u32]) { .. }
  61     /// ```
  62     #[clippy::version = "pre 1.29.0"]
  63     pub PTR_ARG,
  64     style,
  65     "fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively"
  66 }
  67
  68 declare_clippy_lint! {
  69     /// ### What it does
  70     /// This lint checks for equality comparisons with `ptr::null`
  71     ///
  72     /// ### Why is this bad?
  73     /// It's easier and more readable to use the inherent
  74     /// `.is_null()`
  75     /// method instead
  76     ///
  77     /// ### Example
  78     /// ```rust,ignore
  79     /// use std::ptr;
  80     ///
  81     /// if x == ptr::null {
  82     ///     // ..
  83     /// }
  84     /// ```
  85     ///
  86     /// Use instead:
  87     /// ```rust,ignore
  88     /// if x.is_null() {
  89     ///     // ..
  90     /// }
  91     /// ```
  92     #[clippy::version = "pre 1.29.0"]
  93     pub CMP_NULL,
  94     style,
  95     "comparing a pointer to a null pointer, suggesting to use `.is_null()` instead"
  96 }
  97
  98 declare_clippy_lint! {
  99     /// ### What it does
 100     /// This lint checks for functions that take immutable references and return
 101     /// mutable ones. This will not trigger if no unsafe code exists as there
 102     /// are multiple safe functions which will do this transformation
 103     ///
 104     /// To be on the conservative side, if there's at least one mutable
 105     /// reference with the output lifetime, this lint will not trigger.
 106     ///
 107     /// ### Why is this bad?
 108     /// Creating a mutable reference which can be repeatably derived from an
 109     /// immutable reference is unsound as it allows creating multiple live
 110     /// mutable references to the same object.
 111     ///
 112     /// This [error](https://github.com/rust-lang/rust/issues/39465) actually
 113     /// lead to an interim Rust release 1.15.1.
 114     ///
 115     /// ### Known problems
 116     /// This pattern is used by memory allocators to allow allocating multiple
 117     /// objects while returning mutable references to each one. So long as
 118     /// different mutable references are returned each time such a function may
 119     /// be safe.
 120     ///
 121     /// ### Example
 122     /// ```ignore
 123     /// fn foo(&Foo) -> &mut Bar { .. }
 124     /// ```
 125     #[clippy::version = "pre 1.29.0"]
 126     pub MUT_FROM_REF,
 127     correctness,
 128     "fns that create mutable refs from immutable ref args"
 129 }
 130
 131 declare_clippy_lint! {
 132     /// ### What it does
 133     /// This lint checks for invalid usages of `ptr::null`.
 134     ///
 135     /// ### Why is this bad?
 136     /// This causes undefined behavior.
 137     ///
 138     /// ### Example
 139     /// ```ignore
 140     /// // Undefined behavior
 141     /// unsafe { std::slice::from_raw_parts(ptr::null(), 0); }
 142     /// ```
 143     ///
 144     /// Use instead:
 145     /// ```ignore
 146     /// unsafe { std::slice::from_raw_parts(NonNull::dangling().as_ptr(), 0); }
 147     /// ```
 148     #[clippy::version = "1.53.0"]
 149     pub INVALID_NULL_PTR_USAGE,
 150     correctness,
 151     "invalid usage of a null pointer, suggesting `NonNull::dangling()` instead"
 152 }
 153
 154 declare_lint_pass!(Ptr => [PTR_ARG, CMP_NULL, MUT_FROM_REF, INVALID_NULL_PTR_USAGE]);
 155
 156 impl<'tcx> LateLintPass<'tcx> for Ptr {
 157     fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
 158         if let TraitItemKind::Fn(sig, trait_method) = &item.kind {
 159             if matches!(trait_method, TraitFn::Provided(_)) {
 160                 // Handled by check body.
 161                 return;
 162             }
 163
 164             check_mut_from_ref(cx, sig, None);
 165             for arg in check_fn_args(
 166                 cx,
 167                 cx.tcx.fn_sig(item.owner_id).skip_binder().inputs(),
 168                 sig.decl.inputs,
 169                 &[],
 170             )
 171             .filter(|arg| arg.mutability() == Mutability::Not)
 172             {
 173                 span_lint_hir_and_then(cx, PTR_ARG, arg.emission_id, arg.span, &arg.build_msg(), |diag| {
 174                     diag.span_suggestion(
 175                         arg.span,
 176                         "change this to",
 177                         format!("{}{}", arg.ref_prefix, arg.deref_ty.display(cx)),
 178                         Applicability::Unspecified,
 179                     );
 180                 });
 181             }
 182         }
 183     }
 184
 185     fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
 186         let hir = cx.tcx.hir();
 187         let mut parents = hir.parent_iter(body.value.hir_id);
 188         let (item_id, sig, is_trait_item) = match parents.next() {
 189             Some((_, Node::Item(i))) => {
 190                 if let ItemKind::Fn(sig, ..) = &i.kind {
 191                     (i.owner_id, sig, false)
 192                 } else {
 193                     return;
 194                 }
 195             },
 196             Some((_, Node::ImplItem(i))) => {
 197                 if !matches!(parents.next(),
 198                     Some((_, Node::Item(i))) if matches!(&i.kind, ItemKind::Impl(i) if i.of_trait.is_none())
 199                 ) {
 200                     return;
 201                 }
 202                 if let ImplItemKind::Fn(sig, _) = &i.kind {
 203                     (i.owner_id, sig, false)
 204                 } else {
 205                     return;
 206                 }
 207             },
 208             Some((_, Node::TraitItem(i))) => {
 209                 if let TraitItemKind::Fn(sig, _) = &i.kind {
 210                     (i.owner_id, sig, true)
 211                 } else {
 212                     return;
 213                 }
 214             },
 215             _ => return,
 216         };
 217
 218         check_mut_from_ref(cx, sig, Some(body));
 219         let decl = sig.decl;
 220         let sig = cx.tcx.fn_sig(item_id).skip_binder();
 221         let lint_args: Vec<_> = check_fn_args(cx, sig.inputs(), decl.inputs, body.params)
 222             .filter(|arg| !is_trait_item || arg.mutability() == Mutability::Not)
 223             .collect();
 224         let results = check_ptr_arg_usage(cx, body, &lint_args);
 225
 226         for (result, args) in results.iter().zip(lint_args.iter()).filter(|(r, _)| !r.skip) {
 227             span_lint_hir_and_then(cx, PTR_ARG, args.emission_id, args.span, &args.build_msg(), |diag| {
 228                 diag.multipart_suggestion(
 229                     "change this to",
 230                     iter::once((args.span, format!("{}{}", args.ref_prefix, args.deref_ty.display(cx))))
 231                         .chain(result.replacements.iter().map(|r| {
 232                             (
 233                                 r.expr_span,
 234                                 format!("{}{}", snippet_opt(cx, r.self_span).unwrap(), r.replacement),
 235                             )
 236                         }))
 237                         .collect(),
 238                     Applicability::Unspecified,
 239                 );
 240             });
 241         }
 242     }
 243
 244     fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
 245         if let ExprKind::Binary(ref op, l, r) = expr.kind {
 246             if (op.node == BinOpKind::Eq || op.node == BinOpKind::Ne) && (is_null_path(cx, l) || is_null_path(cx, r)) {
 247                 span_lint(
 248                     cx,
 249                     CMP_NULL,
 250                     expr.span,
 251                     "comparing with null is better expressed by the `.is_null()` method",
 252                 );
 253             }
 254         } else {
 255             check_invalid_ptr_usage(cx, expr);
 256         }
 257     }
 258 }
 259
 260 fn check_invalid_ptr_usage<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
 261     // (fn_path, arg_indices) - `arg_indices` are the `arg` positions where null would cause U.B.
 262     const INVALID_NULL_PTR_USAGE_TABLE: [(&[&str], &[usize]); 16] = [
 263         (&paths::SLICE_FROM_RAW_PARTS, &[0]),
 264         (&paths::SLICE_FROM_RAW_PARTS_MUT, &[0]),
 265         (&paths::PTR_COPY, &[0, 1]),
 266         (&paths::PTR_COPY_NONOVERLAPPING, &[0, 1]),
 267         (&paths::PTR_READ, &[0]),
 268         (&paths::PTR_READ_UNALIGNED, &[0]),
 269         (&paths::PTR_READ_VOLATILE, &[0]),
 270         (&paths::PTR_REPLACE, &[0]),
 271         (&paths::PTR_SLICE_FROM_RAW_PARTS, &[0]),
 272         (&paths::PTR_SLICE_FROM_RAW_PARTS_MUT, &[0]),
 273         (&paths::PTR_SWAP, &[0, 1]),
 274         (&paths::PTR_SWAP_NONOVERLAPPING, &[0, 1]),
 275         (&paths::PTR_WRITE, &[0]),
 276         (&paths::PTR_WRITE_UNALIGNED, &[0]),
 277         (&paths::PTR_WRITE_VOLATILE, &[0]),
 278         (&paths::PTR_WRITE_BYTES, &[0]),
 279     ];
 280
 281     if_chain! {
 282         if let ExprKind::Call(fun, args) = expr.kind;
 283         if let ExprKind::Path(ref qpath) = fun.kind;
 284         if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
 285         let fun_def_path = cx.get_def_path(fun_def_id).into_iter().map(Symbol::to_ident_string).collect::<Vec<_>>();
 286         if let Some(&(_, arg_indices)) = INVALID_NULL_PTR_USAGE_TABLE
 287             .iter()
 288             .find(|&&(fn_path, _)| fn_path == fun_def_path);
 289         then {
 290             for &arg_idx in arg_indices {
 291                 if let Some(arg) = args.get(arg_idx).filter(|arg| is_null_path(cx, arg)) {
 292                     span_lint_and_sugg(
 293                         cx,
 294                         INVALID_NULL_PTR_USAGE,
 295                         arg.span,
 296                         "pointer must be non-null",
 297                         "change this to",
 298                         "core::ptr::NonNull::dangling().as_ptr()".to_string(),
 299                         Applicability::MachineApplicable,
 300                     );
 301                 }
 302             }
 303         }
 304     }
 305 }
 306
 307 #[derive(Default)]
 308 struct PtrArgResult {
 309     skip: bool,
 310     replacements: Vec<PtrArgReplacement>,
 311 }
 312
 313 struct PtrArgReplacement {
 314     expr_span: Span,
 315     self_span: Span,
 316     replacement: &'static str,
 317 }
 318
 319 struct PtrArg<'tcx> {
 320     idx: usize,
 321     emission_id: hir::HirId,
 322     span: Span,
 323     ty_did: DefId,
 324     ty_name: Symbol,
 325     method_renames: &'static [(&'static str, &'static str)],
 326     ref_prefix: RefPrefix,
 327     deref_ty: DerefTy<'tcx>,
 328 }
 329 impl PtrArg<'_> {
 330     fn build_msg(&self) -> String {
 331         format!(
 332             "writing `&{}{}` instead of `&{}{}` involves a new object where a slice will do",
 333             self.ref_prefix.mutability.prefix_str(),
 334             self.ty_name,
 335             self.ref_prefix.mutability.prefix_str(),
 336             self.deref_ty.argless_str(),
 337         )
 338     }
 339
 340     fn mutability(&self) -> Mutability {
 341         self.ref_prefix.mutability
 342     }
 343 }
 344
 345 struct RefPrefix {
 346     lt: Lifetime,
 347     mutability: Mutability,
 348 }
 349 impl fmt::Display for RefPrefix {
 350     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 351         use fmt::Write;
 352         f.write_char('&')?;
 353         if !self.lt.is_anonymous() {
 354             self.lt.ident.fmt(f)?;
 355             f.write_char(' ')?;
 356         }
 357         f.write_str(self.mutability.prefix_str())
 358     }
 359 }
 360
 361 struct DerefTyDisplay<'a, 'tcx>(&'a LateContext<'tcx>, &'a DerefTy<'tcx>);
 362 impl fmt::Display for DerefTyDisplay<'_, '_> {
 363     fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
 364         use std::fmt::Write;
 365         match self.1 {
 366             DerefTy::Str => f.write_str("str"),
 367             DerefTy::Path => f.write_str("Path"),
 368             DerefTy::Slice(hir_ty, ty) => {
 369                 f.write_char('[')?;
 370                 match hir_ty.and_then(|s| snippet_opt(self.0, s)) {
 371                     Some(s) => f.write_str(&s)?,
 372                     None => ty.fmt(f)?,
 373                 }
 374                 f.write_char(']')
 375             },
 376         }
 377     }
 378 }
 379
 380 enum DerefTy<'tcx> {
 381     Str,
 382     Path,
 383     Slice(Option<Span>, Ty<'tcx>),
 384 }
 385 impl<'tcx> DerefTy<'tcx> {
 386     fn ty(&self, cx: &LateContext<'tcx>) -> Ty<'tcx> {
 387         match *self {
 388             Self::Str => cx.tcx.types.str_,
 389             Self::Path => cx.tcx.mk_adt(
 390                 cx.tcx.adt_def(cx.tcx.get_diagnostic_item(sym::Path).unwrap()),
 391                 List::empty(),
 392             ),
 393             Self::Slice(_, ty) => cx.tcx.mk_slice(ty),
 394         }
 395     }
 396
 397     fn argless_str(&self) -> &'static str {
 398         match *self {
 399             Self::Str => "str",
 400             Self::Path => "Path",
 401             Self::Slice(..) => "[_]",
 402         }
 403     }
 404
 405     fn display<'a>(&'a self, cx: &'a LateContext<'tcx>) -> DerefTyDisplay<'a, 'tcx> {
 406         DerefTyDisplay(cx, self)
 407     }
 408 }
 409
 410 fn check_fn_args<'cx, 'tcx: 'cx>(
 411     cx: &'cx LateContext<'tcx>,
 412     tys: &'tcx [Ty<'tcx>],
 413     hir_tys: &'tcx [hir::Ty<'tcx>],
 414     params: &'tcx [Param<'tcx>],
 415 ) -> impl Iterator<Item = PtrArg<'tcx>> + 'cx {
 416     tys.iter()
 417         .zip(hir_tys.iter())
 418         .enumerate()
 419         .filter_map(|(i, (ty, hir_ty))| {
 420             if_chain! {
 421                 if let ty::Ref(_, ty, mutability) = *ty.kind();
 422                 if let ty::Adt(adt, substs) = *ty.kind();
 423
 424                 if let TyKind::Rptr(lt, ref ty) = hir_ty.kind;
 425                 if let TyKind::Path(QPath::Resolved(None, path)) = ty.ty.kind;
 426
 427                 // Check that the name as typed matches the actual name of the type.
 428                 // e.g. `fn foo(_: &Foo)` shouldn't trigger the lint when `Foo` is an alias for `Vec`
 429                 if let [.., name] = path.segments;
 430                 if cx.tcx.item_name(adt.did()) == name.ident.name;
 431
 432                 then {
 433                     let emission_id = params.get(i).map_or(hir_ty.hir_id, |param| param.hir_id);
 434                     let (method_renames, deref_ty) = match cx.tcx.get_diagnostic_name(adt.did()) {
 435                         Some(sym::Vec) => (
 436                             [("clone", ".to_owned()")].as_slice(),
 437                             DerefTy::Slice(
 438                                 name.args
 439                                     .and_then(|args| args.args.first())
 440                                     .and_then(|arg| if let GenericArg::Type(ty) = arg {
 441                                         Some(ty.span)
 442                                     } else {
 443                                         None
 444                                     }),
 445                                 substs.type_at(0),
 446                             ),
 447                         ),
 448                         _ if Some(adt.did()) == cx.tcx.lang_items().string() => (
 449                             [("clone", ".to_owned()"), ("as_str", "")].as_slice(),
 450                             DerefTy::Str,
 451                         ),
 452                         Some(sym::PathBuf) => (
 453                             [("clone", ".to_path_buf()"), ("as_path", "")].as_slice(),
 454                             DerefTy::Path,
 455                         ),
 456                         Some(sym::Cow) if mutability == Mutability::Not => {
 457                             let ty_name = name.args
 458                                 .and_then(|args| {
 459                                     args.args.iter().find_map(|a| match a {
 460                                         GenericArg::Type(x) => Some(x),
 461                                         _ => None,
 462                                     })
 463                                 })
 464                                 .and_then(|arg| snippet_opt(cx, arg.span))
 465                                 .unwrap_or_else(|| substs.type_at(1).to_string());
 466                             span_lint_hir_and_then(
 467                                 cx,
 468                                 PTR_ARG,
 469                                 emission_id,
 470                                 hir_ty.span,
 471                                 "using a reference to `Cow` is not recommended",
 472                                 |diag| {
 473                                     diag.span_suggestion(
 474                                         hir_ty.span,
 475                                         "change this to",
 476                                         format!("&{}{ty_name}", mutability.prefix_str()),
 477                                         Applicability::Unspecified,
 478                                     );
 479                                 }
 480                             );
 481                             return None;
 482                         },
 483                         _ => return None,
 484                     };
 485                     return Some(PtrArg {
 486                         idx: i,
 487                         emission_id,
 488                         span: hir_ty.span,
 489                         ty_did: adt.did(),
 490                         ty_name: name.ident.name,
 491                         method_renames,
 492                         ref_prefix: RefPrefix {
 493                             lt: *lt,
 494                             mutability,
 495                         },
 496                         deref_ty,
 497                     });
 498                 }
 499             }
 500             None
 501         })
 502 }
 503
 504 fn check_mut_from_ref<'tcx>(cx: &LateContext<'tcx>, sig: &FnSig<'_>, body: Option<&'tcx Body<'_>>) {
 505     if let FnRetTy::Return(ty) = sig.decl.output
 506         && let Some((out, Mutability::Mut, _)) = get_rptr_lm(ty)
 507     {
 508         let out_region = cx.tcx.named_region(out.hir_id);
 509         let args: Option<Vec<_>> = sig
 510             .decl
 511             .inputs
 512             .iter()
 513             .filter_map(get_rptr_lm)
 514             .filter(|&(lt, _, _)| cx.tcx.named_region(lt.hir_id) == out_region)
 515             .map(|(_, mutability, span)| (mutability == Mutability::Not).then_some(span))
 516             .collect();
 517         if let Some(args) = args
 518             && !args.is_empty()
 519             && body.map_or(true, |body| {
 520                 sig.header.unsafety == Unsafety::Unsafe || contains_unsafe_block(cx, body.value)
 521             })
 522         {
 523             span_lint_and_then(
 524                 cx,
 525                 MUT_FROM_REF,
 526                 ty.span,
 527                 "mutable borrow from immutable input(s)",
 528                 |diag| {
 529                     let ms = MultiSpan::from_spans(args);
 530                     diag.span_note(ms, "immutable borrow here");
 531                 },
 532             );
 533         }
 534     }
 535 }
 536
 537 #[expect(clippy::too_many_lines)]
 538 fn check_ptr_arg_usage<'tcx>(cx: &LateContext<'tcx>, body: &'tcx Body<'_>, args: &[PtrArg<'tcx>]) -> Vec<PtrArgResult> {
 539     struct V<'cx, 'tcx> {
 540         cx: &'cx LateContext<'tcx>,
 541         /// Map from a local id to which argument it came from (index into `Self::args` and
 542         /// `Self::results`)
 543         bindings: HirIdMap<usize>,
 544         /// The arguments being checked.
 545         args: &'cx [PtrArg<'tcx>],
 546         /// The results for each argument (len should match args.len)
 547         results: Vec<PtrArgResult>,
 548         /// The number of arguments which can't be linted. Used to return early.
 549         skip_count: usize,
 550     }
 551     impl<'tcx> Visitor<'tcx> for V<'_, 'tcx> {
 552         type NestedFilter = nested_filter::OnlyBodies;
 553         fn nested_visit_map(&mut self) -> Self::Map {
 554             self.cx.tcx.hir()
 555         }
 556
 557         fn visit_anon_const(&mut self, _: &'tcx AnonConst) {}
 558
 559         fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
 560             if self.skip_count == self.args.len() {
 561                 return;
 562             }
 563
 564             // Check if this is local we care about
 565             let Some(&args_idx) = path_to_local(e).and_then(|id| self.bindings.get(&id)) else {
 566                 return walk_expr(self, e);
 567             };
 568             let args = &self.args[args_idx];
 569             let result = &mut self.results[args_idx];
 570
 571             // Helper function to handle early returns.
 572             let mut set_skip_flag = || {
 573                 if !result.skip {
 574                     self.skip_count += 1;
 575                 }
 576                 result.skip = true;
 577             };
 578
 579             match get_expr_use_or_unification_node(self.cx.tcx, e) {
 580                 Some((Node::Stmt(_), _)) => (),
 581                 Some((Node::Local(l), _)) => {
 582                     // Only trace simple bindings. e.g `let x = y;`
 583                     if let PatKind::Binding(BindingAnnotation::NONE, id, _, None) = l.pat.kind {
 584                         self.bindings.insert(id, args_idx);
 585                     } else {
 586                         set_skip_flag();
 587                     }
 588                 },
 589                 Some((Node::Expr(e), child_id)) => match e.kind {
 590                     ExprKind::Call(f, expr_args) => {
 591                         let i = expr_args.iter().position(|arg| arg.hir_id == child_id).unwrap_or(0);
 592                         if expr_sig(self.cx, f).and_then(|sig| sig.input(i)).map_or(true, |ty| {
 593                             match *ty.skip_binder().peel_refs().kind() {
 594                                 ty::Dynamic(preds, _, _) => !matches_preds(self.cx, args.deref_ty.ty(self.cx), preds),
 595                                 ty::Param(_) => true,
 596                                 ty::Adt(def, _) => def.did() == args.ty_did,
 597                                 _ => false,
 598                             }
 599                         }) {
 600                             // Passed to a function taking the non-dereferenced type.
 601                             set_skip_flag();
 602                         }
 603                     },
 604                     ExprKind::MethodCall(name, self_arg, expr_args, _) => {
 605                         let i = std::iter::once(self_arg)
 606                             .chain(expr_args.iter())
 607                             .position(|arg| arg.hir_id == child_id)
 608                             .unwrap_or(0);
 609                         if i == 0 {
 610                             // Check if the method can be renamed.
 611                             let name = name.ident.as_str();
 612                             if let Some((_, replacement)) = args.method_renames.iter().find(|&&(x, _)| x == name) {
 613                                 result.replacements.push(PtrArgReplacement {
 614                                     expr_span: e.span,
 615                                     self_span: self_arg.span,
 616                                     replacement,
 617                                 });
 618                                 return;
 619                             }
 620                         }
 621
 622                         let Some(id) = self.cx.typeck_results().type_dependent_def_id(e.hir_id) else {
 623                             set_skip_flag();
 624                             return;
 625                         };
 626
 627                         match *self.cx.tcx.fn_sig(id).skip_binder().inputs()[i].peel_refs().kind() {
 628                             ty::Dynamic(preds, _, _) if !matches_preds(self.cx, args.deref_ty.ty(self.cx), preds) => {
 629                                 set_skip_flag();
 630                             },
 631                             ty::Param(_) => {
 632                                 set_skip_flag();
 633                             },
 634                             // If the types match check for methods which exist on both types. e.g. `Vec::len` and
 635                             // `slice::len`
 636                             ty::Adt(def, _) if def.did() == args.ty_did => {
 637                                 set_skip_flag();
 638                             },
 639                             _ => (),
 640                         }
 641                     },
 642                     // Indexing is fine for currently supported types.
 643                     ExprKind::Index(e, _) if e.hir_id == child_id => (),
 644                     _ => set_skip_flag(),
 645                 },
 646                 _ => set_skip_flag(),
 647             }
 648         }
 649     }
 650
 651     let mut skip_count = 0;
 652     let mut results = args.iter().map(|_| PtrArgResult::default()).collect::<Vec<_>>();
 653     let mut v = V {
 654         cx,
 655         bindings: args
 656             .iter()
 657             .enumerate()
 658             .filter_map(|(i, arg)| {
 659                 let param = &body.params[arg.idx];
 660                 match param.pat.kind {
 661                     PatKind::Binding(BindingAnnotation::NONE, id, _, None)
 662                         if !is_lint_allowed(cx, PTR_ARG, param.hir_id) =>
 663                     {
 664                         Some((id, i))
 665                     },
 666                     _ => {
 667                         skip_count += 1;
 668                         results[i].skip = true;
 669                         None
 670                     },
 671                 }
 672             })
 673             .collect(),
 674         args,
 675         results,
 676         skip_count,
 677     };
 678     v.visit_expr(body.value);
 679     v.results
 680 }
 681
 682 fn matches_preds<'tcx>(
 683     cx: &LateContext<'tcx>,
 684     ty: Ty<'tcx>,
 685     preds: &'tcx [ty::PolyExistentialPredicate<'tcx>],
 686 ) -> bool {
 687     let infcx = cx.tcx.infer_ctxt().build();
 688     preds.iter().all(|&p| match cx.tcx.erase_late_bound_regions(p) {
 689         ExistentialPredicate::Trait(p) => infcx
 690             .type_implements_trait(p.def_id, [ty.into()].into_iter().chain(p.substs.iter()), cx.param_env)
 691             .must_apply_modulo_regions(),
 692         ExistentialPredicate::Projection(p) => infcx.predicate_must_hold_modulo_regions(&Obligation::new(
 693             cx.tcx,
 694             ObligationCause::dummy(),
 695             cx.param_env,
 696             cx.tcx
 697                 .mk_predicate(Binder::dummy(PredicateKind::Clause(Clause::Projection(
 698                     p.with_self_ty(cx.tcx, ty),
 699                 )))),
 700         )),
 701         ExistentialPredicate::AutoTrait(p) => infcx
 702             .type_implements_trait(p, [ty], cx.param_env)
 703             .must_apply_modulo_regions(),
 704     })
 705 }
 706
 707 fn get_rptr_lm<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> Option<(&'tcx Lifetime, Mutability, Span)> {
 708     if let TyKind::Rptr(lt, ref m) = ty.kind {
 709         Some((lt, m.mutbl, ty.span))
 710     } else {
 711         None
 712     }
 713 }
 714
 715 fn is_null_path(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
 716     if let ExprKind::Call(pathexp, []) = expr.kind {
 717         path_def_id(cx, pathexp).map_or(false, |id| {
 718             matches!(cx.tcx.get_diagnostic_name(id), Some(sym::ptr_null | sym::ptr_null_mut))
 719         })
 720     } else {
 721         false
 722     }
 723 }