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