681 lines
25 KiB
Rust
681 lines
25 KiB
Rust
//! Checks for usage of `&Vec[_]` and `&String`.
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use clippy_utils::diagnostics::{span_lint, span_lint_and_sugg, span_lint_and_then};
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use clippy_utils::source::snippet_opt;
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use clippy_utils::ty::expr_sig;
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use clippy_utils::{get_expr_use_or_unification_node, is_lint_allowed, path_def_id, path_to_local, paths};
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use if_chain::if_chain;
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use rustc_errors::Applicability;
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use rustc_hir::def_id::DefId;
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use rustc_hir::hir_id::HirIdMap;
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use rustc_hir::intravisit::{walk_expr, Visitor};
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use rustc_hir::{
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self as hir, AnonConst, BinOpKind, BindingAnnotation, Body, Expr, ExprKind, FnDecl, FnRetTy, GenericArg,
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ImplItemKind, ItemKind, Lifetime, LifetimeName, Mutability, Node, Param, ParamName, PatKind, QPath, TraitFn,
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TraitItem, TraitItemKind, TyKind,
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};
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use rustc_lint::{LateContext, LateLintPass};
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use rustc_middle::hir::nested_filter;
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use rustc_middle::ty::{self, AssocItems, AssocKind, Ty};
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use rustc_session::{declare_lint_pass, declare_tool_lint};
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use rustc_span::source_map::Span;
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use rustc_span::symbol::Symbol;
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use rustc_span::{sym, MultiSpan};
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use std::fmt;
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use std::iter;
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declare_clippy_lint! {
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/// ### What it does
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/// This lint checks for function arguments of type `&String`, `&Vec`,
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/// `&PathBuf`, and `Cow<_>`. It will also suggest you replace `.clone()` calls
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/// with the appropriate `.to_owned()`/`to_string()` calls.
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///
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/// ### Why is this bad?
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/// Requiring the argument to be of the specific size
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/// makes the function less useful for no benefit; slices in the form of `&[T]`
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/// or `&str` usually suffice and can be obtained from other types, too.
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///
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/// ### Known problems
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/// There may be `fn(&Vec)`-typed references pointing to your function.
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/// If you have them, you will get a compiler error after applying this lint's
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/// suggestions. You then have the choice to undo your changes or change the
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/// type of the reference.
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///
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/// Note that if the function is part of your public interface, there may be
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/// other crates referencing it, of which you may not be aware. Carefully
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/// deprecate the function before applying the lint suggestions in this case.
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///
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/// ### Example
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/// ```ignore
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/// // Bad
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/// fn foo(&Vec<u32>) { .. }
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///
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/// // Good
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/// fn foo(&[u32]) { .. }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub PTR_ARG,
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style,
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"fn arguments of the type `&Vec<...>` or `&String`, suggesting to use `&[...]` or `&str` instead, respectively"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// This lint checks for equality comparisons with `ptr::null`
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///
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/// ### Why is this bad?
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/// It's easier and more readable to use the inherent
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/// `.is_null()`
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/// method instead
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///
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/// ### Example
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/// ```ignore
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/// // Bad
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/// if x == ptr::null {
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/// ..
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/// }
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///
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/// // Good
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/// if x.is_null() {
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/// ..
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/// }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub CMP_NULL,
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style,
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"comparing a pointer to a null pointer, suggesting to use `.is_null()` instead"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// This lint checks for functions that take immutable
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/// references and return mutable ones.
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///
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/// ### Why is this bad?
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/// This is trivially unsound, as one can create two
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/// mutable references from the same (immutable!) source.
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/// This [error](https://github.com/rust-lang/rust/issues/39465)
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/// actually lead to an interim Rust release 1.15.1.
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///
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/// ### Known problems
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/// To be on the conservative side, if there's at least one
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/// mutable reference with the output lifetime, this lint will not trigger.
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/// In practice, this case is unlikely anyway.
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///
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/// ### Example
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/// ```ignore
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/// fn foo(&Foo) -> &mut Bar { .. }
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/// ```
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#[clippy::version = "pre 1.29.0"]
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pub MUT_FROM_REF,
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correctness,
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"fns that create mutable refs from immutable ref args"
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}
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declare_clippy_lint! {
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/// ### What it does
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/// This lint checks for invalid usages of `ptr::null`.
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///
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/// ### Why is this bad?
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/// This causes undefined behavior.
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///
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/// ### Example
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/// ```ignore
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/// // Bad. Undefined behavior
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/// unsafe { std::slice::from_raw_parts(ptr::null(), 0); }
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/// ```
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///
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/// ```ignore
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/// // Good
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/// unsafe { std::slice::from_raw_parts(NonNull::dangling().as_ptr(), 0); }
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/// ```
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#[clippy::version = "1.53.0"]
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pub INVALID_NULL_PTR_USAGE,
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correctness,
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"invalid usage of a null pointer, suggesting `NonNull::dangling()` instead"
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}
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declare_lint_pass!(Ptr => [PTR_ARG, CMP_NULL, MUT_FROM_REF, INVALID_NULL_PTR_USAGE]);
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impl<'tcx> LateLintPass<'tcx> for Ptr {
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fn check_trait_item(&mut self, cx: &LateContext<'tcx>, item: &'tcx TraitItem<'_>) {
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if let TraitItemKind::Fn(sig, trait_method) = &item.kind {
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if matches!(trait_method, TraitFn::Provided(_)) {
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// Handled by check body.
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return;
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}
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check_mut_from_ref(cx, sig.decl);
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for arg in check_fn_args(
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cx,
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cx.tcx.fn_sig(item.def_id).skip_binder().inputs(),
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sig.decl.inputs,
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&[],
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)
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.filter(|arg| arg.mutability() == Mutability::Not)
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{
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span_lint_and_sugg(
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cx,
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PTR_ARG,
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arg.span,
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&arg.build_msg(),
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"change this to",
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format!("{}{}", arg.ref_prefix, arg.deref_ty.display(cx)),
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Applicability::Unspecified,
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);
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}
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}
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}
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fn check_body(&mut self, cx: &LateContext<'tcx>, body: &'tcx Body<'_>) {
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let hir = cx.tcx.hir();
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let mut parents = hir.parent_iter(body.value.hir_id);
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let (item_id, decl, is_trait_item) = match parents.next() {
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Some((_, Node::Item(i))) => {
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if let ItemKind::Fn(sig, ..) = &i.kind {
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(i.def_id, sig.decl, false)
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} else {
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return;
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}
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},
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Some((_, Node::ImplItem(i))) => {
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if !matches!(parents.next(),
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Some((_, Node::Item(i))) if matches!(&i.kind, ItemKind::Impl(i) if i.of_trait.is_none())
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) {
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return;
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}
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if let ImplItemKind::Fn(sig, _) = &i.kind {
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(i.def_id, sig.decl, false)
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} else {
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return;
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}
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},
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Some((_, Node::TraitItem(i))) => {
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if let TraitItemKind::Fn(sig, _) = &i.kind {
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(i.def_id, sig.decl, true)
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} else {
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return;
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}
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},
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_ => return,
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};
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check_mut_from_ref(cx, decl);
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let sig = cx.tcx.fn_sig(item_id).skip_binder();
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let lint_args: Vec<_> = check_fn_args(cx, sig.inputs(), decl.inputs, body.params)
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.filter(|arg| !is_trait_item || arg.mutability() == Mutability::Not)
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.collect();
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let results = check_ptr_arg_usage(cx, body, &lint_args);
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for (result, args) in results.iter().zip(lint_args.iter()).filter(|(r, _)| !r.skip) {
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span_lint_and_then(cx, PTR_ARG, args.span, &args.build_msg(), |diag| {
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diag.multipart_suggestion(
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"change this to",
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iter::once((args.span, format!("{}{}", args.ref_prefix, args.deref_ty.display(cx))))
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.chain(result.replacements.iter().map(|r| {
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(
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r.expr_span,
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format!("{}{}", snippet_opt(cx, r.self_span).unwrap(), r.replacement),
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)
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}))
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.collect(),
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Applicability::Unspecified,
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);
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});
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}
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}
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fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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if let ExprKind::Binary(ref op, l, r) = expr.kind {
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if (op.node == BinOpKind::Eq || op.node == BinOpKind::Ne) && (is_null_path(cx, l) || is_null_path(cx, r)) {
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span_lint(
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cx,
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CMP_NULL,
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expr.span,
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"comparing with null is better expressed by the `.is_null()` method",
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);
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}
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} else {
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check_invalid_ptr_usage(cx, expr);
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}
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}
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}
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fn check_invalid_ptr_usage<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'_>) {
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// (fn_path, arg_indices) - `arg_indices` are the `arg` positions where null would cause U.B.
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const INVALID_NULL_PTR_USAGE_TABLE: [(&[&str], &[usize]); 16] = [
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(&paths::SLICE_FROM_RAW_PARTS, &[0]),
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(&paths::SLICE_FROM_RAW_PARTS_MUT, &[0]),
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(&paths::PTR_COPY, &[0, 1]),
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(&paths::PTR_COPY_NONOVERLAPPING, &[0, 1]),
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(&paths::PTR_READ, &[0]),
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(&paths::PTR_READ_UNALIGNED, &[0]),
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(&paths::PTR_READ_VOLATILE, &[0]),
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(&paths::PTR_REPLACE, &[0]),
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(&paths::PTR_SLICE_FROM_RAW_PARTS, &[0]),
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(&paths::PTR_SLICE_FROM_RAW_PARTS_MUT, &[0]),
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(&paths::PTR_SWAP, &[0, 1]),
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(&paths::PTR_SWAP_NONOVERLAPPING, &[0, 1]),
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(&paths::PTR_WRITE, &[0]),
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(&paths::PTR_WRITE_UNALIGNED, &[0]),
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(&paths::PTR_WRITE_VOLATILE, &[0]),
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(&paths::PTR_WRITE_BYTES, &[0]),
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];
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if_chain! {
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if let ExprKind::Call(fun, args) = expr.kind;
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if let ExprKind::Path(ref qpath) = fun.kind;
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if let Some(fun_def_id) = cx.qpath_res(qpath, fun.hir_id).opt_def_id();
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let fun_def_path = cx.get_def_path(fun_def_id).into_iter().map(Symbol::to_ident_string).collect::<Vec<_>>();
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if let Some(&(_, arg_indices)) = INVALID_NULL_PTR_USAGE_TABLE
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.iter()
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.find(|&&(fn_path, _)| fn_path == fun_def_path);
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then {
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for &arg_idx in arg_indices {
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if let Some(arg) = args.get(arg_idx).filter(|arg| is_null_path(cx, arg)) {
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span_lint_and_sugg(
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cx,
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INVALID_NULL_PTR_USAGE,
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arg.span,
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"pointer must be non-null",
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"change this to",
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"core::ptr::NonNull::dangling().as_ptr()".to_string(),
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Applicability::MachineApplicable,
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);
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}
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}
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}
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}
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}
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#[derive(Default)]
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struct PtrArgResult {
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skip: bool,
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replacements: Vec<PtrArgReplacement>,
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}
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struct PtrArgReplacement {
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expr_span: Span,
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self_span: Span,
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replacement: &'static str,
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}
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struct PtrArg<'tcx> {
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idx: usize,
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span: Span,
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ty_did: DefId,
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ty_name: Symbol,
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method_renames: &'static [(&'static str, &'static str)],
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ref_prefix: RefPrefix,
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deref_ty: DerefTy<'tcx>,
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deref_assoc_items: Option<(DefId, &'tcx AssocItems<'tcx>)>,
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}
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impl PtrArg<'_> {
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fn build_msg(&self) -> String {
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format!(
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"writing `&{}{}` instead of `&{}{}` involves a new object where a slice will do",
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self.ref_prefix.mutability.prefix_str(),
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self.ty_name,
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self.ref_prefix.mutability.prefix_str(),
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self.deref_ty.argless_str(),
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)
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}
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fn mutability(&self) -> Mutability {
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self.ref_prefix.mutability
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}
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}
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struct RefPrefix {
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lt: LifetimeName,
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mutability: Mutability,
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}
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impl fmt::Display for RefPrefix {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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use fmt::Write;
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f.write_char('&')?;
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match self.lt {
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LifetimeName::Param(ParamName::Plain(name)) => {
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name.fmt(f)?;
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f.write_char(' ')?;
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},
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LifetimeName::Underscore => f.write_str("'_ ")?,
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LifetimeName::Static => f.write_str("'static ")?,
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_ => (),
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}
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f.write_str(self.mutability.prefix_str())
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}
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}
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struct DerefTyDisplay<'a, 'tcx>(&'a LateContext<'tcx>, &'a DerefTy<'tcx>);
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impl fmt::Display for DerefTyDisplay<'_, '_> {
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fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
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use std::fmt::Write;
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match self.1 {
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DerefTy::Str => f.write_str("str"),
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DerefTy::Path => f.write_str("Path"),
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DerefTy::Slice(hir_ty, ty) => {
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f.write_char('[')?;
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match hir_ty.and_then(|s| snippet_opt(self.0, s)) {
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Some(s) => f.write_str(&s)?,
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None => ty.fmt(f)?,
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}
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f.write_char(']')
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},
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}
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}
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}
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enum DerefTy<'tcx> {
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Str,
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Path,
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Slice(Option<Span>, Ty<'tcx>),
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}
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impl<'tcx> DerefTy<'tcx> {
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fn argless_str(&self) -> &'static str {
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match *self {
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Self::Str => "str",
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Self::Path => "Path",
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Self::Slice(..) => "[_]",
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}
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}
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fn display<'a>(&'a self, cx: &'a LateContext<'tcx>) -> DerefTyDisplay<'a, 'tcx> {
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DerefTyDisplay(cx, self)
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}
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}
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fn check_fn_args<'cx, 'tcx: 'cx>(
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cx: &'cx LateContext<'tcx>,
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tys: &'tcx [Ty<'_>],
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hir_tys: &'tcx [hir::Ty<'_>],
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params: &'tcx [Param<'_>],
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) -> impl Iterator<Item = PtrArg<'tcx>> + 'cx {
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tys.iter()
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.zip(hir_tys.iter())
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.enumerate()
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.filter_map(|(i, (ty, hir_ty))| {
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if_chain! {
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if let ty::Ref(_, ty, mutability) = *ty.kind();
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if let ty::Adt(adt, substs) = *ty.kind();
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if let TyKind::Rptr(lt, ref ty) = hir_ty.kind;
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if let TyKind::Path(QPath::Resolved(None, path)) = ty.ty.kind;
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// Check that the name as typed matches the actual name of the type.
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// e.g. `fn foo(_: &Foo)` shouldn't trigger the lint when `Foo` is an alias for `Vec`
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if let [.., name] = path.segments;
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if cx.tcx.item_name(adt.did()) == name.ident.name;
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if !is_lint_allowed(cx, PTR_ARG, hir_ty.hir_id);
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if params.get(i).map_or(true, |p| !is_lint_allowed(cx, PTR_ARG, p.hir_id));
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then {
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let (method_renames, deref_ty, deref_impl_id) = match cx.tcx.get_diagnostic_name(adt.did()) {
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Some(sym::Vec) => (
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[("clone", ".to_owned()")].as_slice(),
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DerefTy::Slice(
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name.args
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.and_then(|args| args.args.first())
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.and_then(|arg| if let GenericArg::Type(ty) = arg {
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Some(ty.span)
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} else {
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None
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}),
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substs.type_at(0),
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),
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cx.tcx.lang_items().slice_impl()
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),
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Some(sym::String) => (
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[("clone", ".to_owned()"), ("as_str", "")].as_slice(),
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DerefTy::Str,
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cx.tcx.lang_items().str_impl()
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),
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Some(sym::PathBuf) => (
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[("clone", ".to_path_buf()"), ("as_path", "")].as_slice(),
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DerefTy::Path,
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None,
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),
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Some(sym::Cow) if mutability == Mutability::Not => {
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let ty_name = name.args
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.and_then(|args| {
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args.args.iter().find_map(|a| match a {
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GenericArg::Type(x) => Some(x),
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_ => None,
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})
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})
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.and_then(|arg| snippet_opt(cx, arg.span))
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.unwrap_or_else(|| substs.type_at(1).to_string());
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span_lint_and_sugg(
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cx,
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PTR_ARG,
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hir_ty.span,
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"using a reference to `Cow` is not recommended",
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"change this to",
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format!("&{}{}", mutability.prefix_str(), ty_name),
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Applicability::Unspecified,
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);
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return None;
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},
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_ => return None,
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};
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return Some(PtrArg {
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idx: i,
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span: hir_ty.span,
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ty_did: adt.did(),
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ty_name: name.ident.name,
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method_renames,
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ref_prefix: RefPrefix {
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lt: lt.name,
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mutability,
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|
},
|
|
deref_ty,
|
|
deref_assoc_items: deref_impl_id.map(|id| (id, cx.tcx.associated_items(id))),
|
|
});
|
|
}
|
|
}
|
|
None
|
|
})
|
|
}
|
|
|
|
fn check_mut_from_ref(cx: &LateContext<'_>, decl: &FnDecl<'_>) {
|
|
if let FnRetTy::Return(ty) = decl.output {
|
|
if let Some((out, Mutability::Mut, _)) = get_rptr_lm(ty) {
|
|
let mut immutables = vec![];
|
|
for (_, mutbl, argspan) in decl
|
|
.inputs
|
|
.iter()
|
|
.filter_map(get_rptr_lm)
|
|
.filter(|&(lt, _, _)| lt.name == out.name)
|
|
{
|
|
if mutbl == Mutability::Mut {
|
|
return;
|
|
}
|
|
immutables.push(argspan);
|
|
}
|
|
if immutables.is_empty() {
|
|
return;
|
|
}
|
|
span_lint_and_then(
|
|
cx,
|
|
MUT_FROM_REF,
|
|
ty.span,
|
|
"mutable borrow from immutable input(s)",
|
|
|diag| {
|
|
let ms = MultiSpan::from_spans(immutables);
|
|
diag.span_note(ms, "immutable borrow here");
|
|
},
|
|
);
|
|
}
|
|
}
|
|
}
|
|
|
|
#[allow(clippy::too_many_lines)]
|
|
fn check_ptr_arg_usage<'tcx>(cx: &LateContext<'tcx>, body: &'tcx Body<'_>, args: &[PtrArg<'tcx>]) -> Vec<PtrArgResult> {
|
|
struct V<'cx, 'tcx> {
|
|
cx: &'cx LateContext<'tcx>,
|
|
/// Map from a local id to which argument it came from (index into `Self::args` and
|
|
/// `Self::results`)
|
|
bindings: HirIdMap<usize>,
|
|
/// The arguments being checked.
|
|
args: &'cx [PtrArg<'tcx>],
|
|
/// The results for each argument (len should match args.len)
|
|
results: Vec<PtrArgResult>,
|
|
/// The number of arguments which can't be linted. Used to return early.
|
|
skip_count: usize,
|
|
}
|
|
impl<'tcx> Visitor<'tcx> for V<'_, 'tcx> {
|
|
type NestedFilter = nested_filter::OnlyBodies;
|
|
fn nested_visit_map(&mut self) -> Self::Map {
|
|
self.cx.tcx.hir()
|
|
}
|
|
|
|
fn visit_anon_const(&mut self, _: &'tcx AnonConst) {}
|
|
|
|
fn visit_expr(&mut self, e: &'tcx Expr<'_>) {
|
|
if self.skip_count == self.args.len() {
|
|
return;
|
|
}
|
|
|
|
// Check if this is local we care about
|
|
let args_idx = match path_to_local(e).and_then(|id| self.bindings.get(&id)) {
|
|
Some(&i) => i,
|
|
None => return walk_expr(self, e),
|
|
};
|
|
let args = &self.args[args_idx];
|
|
let result = &mut self.results[args_idx];
|
|
|
|
// Helper function to handle early returns.
|
|
let mut set_skip_flag = || {
|
|
if !result.skip {
|
|
self.skip_count += 1;
|
|
}
|
|
result.skip = true;
|
|
};
|
|
|
|
match get_expr_use_or_unification_node(self.cx.tcx, e) {
|
|
Some((Node::Stmt(_), _)) => (),
|
|
Some((Node::Local(l), _)) => {
|
|
// Only trace simple bindings. e.g `let x = y;`
|
|
if let PatKind::Binding(BindingAnnotation::Unannotated, id, _, None) = l.pat.kind {
|
|
self.bindings.insert(id, args_idx);
|
|
} else {
|
|
set_skip_flag();
|
|
}
|
|
},
|
|
Some((Node::Expr(e), child_id)) => match e.kind {
|
|
ExprKind::Call(f, expr_args) => {
|
|
let i = expr_args.iter().position(|arg| arg.hir_id == child_id).unwrap_or(0);
|
|
if expr_sig(self.cx, f)
|
|
.map(|sig| sig.input(i).skip_binder().peel_refs())
|
|
.map_or(true, |ty| match *ty.kind() {
|
|
ty::Param(_) => true,
|
|
ty::Adt(def, _) => def.did() == args.ty_did,
|
|
_ => false,
|
|
})
|
|
{
|
|
// Passed to a function taking the non-dereferenced type.
|
|
set_skip_flag();
|
|
}
|
|
},
|
|
ExprKind::MethodCall(name, expr_args @ [self_arg, ..], _) => {
|
|
let i = expr_args.iter().position(|arg| arg.hir_id == child_id).unwrap_or(0);
|
|
if i == 0 {
|
|
// Check if the method can be renamed.
|
|
let name = name.ident.as_str();
|
|
if let Some((_, replacement)) = args.method_renames.iter().find(|&&(x, _)| x == name) {
|
|
result.replacements.push(PtrArgReplacement {
|
|
expr_span: e.span,
|
|
self_span: self_arg.span,
|
|
replacement,
|
|
});
|
|
return;
|
|
}
|
|
}
|
|
|
|
let id = if let Some(x) = self.cx.typeck_results().type_dependent_def_id(e.hir_id) {
|
|
x
|
|
} else {
|
|
set_skip_flag();
|
|
return;
|
|
};
|
|
|
|
match *self.cx.tcx.fn_sig(id).skip_binder().inputs()[i].peel_refs().kind() {
|
|
ty::Param(_) => {
|
|
set_skip_flag();
|
|
},
|
|
// If the types match check for methods which exist on both types. e.g. `Vec::len` and
|
|
// `slice::len`
|
|
ty::Adt(def, _)
|
|
if def.did() == args.ty_did
|
|
&& (i != 0
|
|
|| self.cx.tcx.trait_of_item(id).is_some()
|
|
|| !args.deref_assoc_items.map_or(false, |(id, items)| {
|
|
items
|
|
.find_by_name_and_kind(self.cx.tcx, name.ident, AssocKind::Fn, id)
|
|
.is_some()
|
|
})) =>
|
|
{
|
|
set_skip_flag();
|
|
},
|
|
_ => (),
|
|
}
|
|
},
|
|
// Indexing is fine for currently supported types.
|
|
ExprKind::Index(e, _) if e.hir_id == child_id => (),
|
|
_ => set_skip_flag(),
|
|
},
|
|
_ => set_skip_flag(),
|
|
}
|
|
}
|
|
}
|
|
|
|
let mut skip_count = 0;
|
|
let mut results = args.iter().map(|_| PtrArgResult::default()).collect::<Vec<_>>();
|
|
let mut v = V {
|
|
cx,
|
|
bindings: args
|
|
.iter()
|
|
.enumerate()
|
|
.filter_map(|(i, arg)| {
|
|
let param = &body.params[arg.idx];
|
|
match param.pat.kind {
|
|
PatKind::Binding(BindingAnnotation::Unannotated, id, _, None)
|
|
if !is_lint_allowed(cx, PTR_ARG, param.hir_id) =>
|
|
{
|
|
Some((id, i))
|
|
},
|
|
_ => {
|
|
skip_count += 1;
|
|
results[i].skip = true;
|
|
None
|
|
},
|
|
}
|
|
})
|
|
.collect(),
|
|
args,
|
|
results,
|
|
skip_count,
|
|
};
|
|
v.visit_expr(&body.value);
|
|
v.results
|
|
}
|
|
|
|
fn get_rptr_lm<'tcx>(ty: &'tcx hir::Ty<'tcx>) -> Option<(&'tcx Lifetime, Mutability, Span)> {
|
|
if let TyKind::Rptr(ref lt, ref m) = ty.kind {
|
|
Some((lt, m.mutbl, ty.span))
|
|
} else {
|
|
None
|
|
}
|
|
}
|
|
|
|
fn is_null_path(cx: &LateContext<'_>, expr: &Expr<'_>) -> bool {
|
|
if let ExprKind::Call(pathexp, []) = expr.kind {
|
|
path_def_id(cx, pathexp).map_or(false, |id| {
|
|
matches!(cx.tcx.get_diagnostic_name(id), Some(sym::ptr_null | sym::ptr_null_mut))
|
|
})
|
|
} else {
|
|
false
|
|
}
|
|
}
|