diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2f64cd0e914..7b5279cda6e 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -3210,6 +3210,7 @@ Released 2018-09-13
[`unnecessary_operation`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_operation
[`unnecessary_self_imports`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_self_imports
[`unnecessary_sort_by`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_sort_by
+[`unnecessary_to_owned`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_to_owned
[`unnecessary_unwrap`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_unwrap
[`unnecessary_wraps`]: https://rust-lang.github.io/rust-clippy/master/index.html#unnecessary_wraps
[`unneeded_field_pattern`]: https://rust-lang.github.io/rust-clippy/master/index.html#unneeded_field_pattern
diff --git a/clippy_lints/src/lib.register_all.rs b/clippy_lints/src/lib.register_all.rs
index 9ac77d63879..3d3999d4cc0 100644
--- a/clippy_lints/src/lib.register_all.rs
+++ b/clippy_lints/src/lib.register_all.rs
@@ -181,6 +181,7 @@ store.register_group(true, "clippy::all", Some("clippy_all"), vec
+ /// and other `to_owned`-like functions.
+ ///
+ /// ### Why is this bad?
+ /// The unnecessary calls result in unnecessary allocations.
+ ///
+ /// ### Example
+ /// ```rust
+ /// let path = std::path::Path::new("x");
+ /// foo(&path.to_string_lossy().to_string());
+ /// fn foo(s: &str) {}
+ /// ```
+ /// Use instead:
+ /// ```rust
+ /// let path = std::path::Path::new("x");
+ /// foo(&path.to_string_lossy());
+ /// fn foo(s: &str) {}
+ /// ```
+ #[clippy::version = "1.58.0"]
+ pub UNNECESSARY_TO_OWNED,
+ perf,
+ "unnecessary calls to `to_owned`-like functions"
+}
+
pub struct Methods {
avoid_breaking_exported_api: bool,
msrv: Option<RustcVersion>,
@@ -1964,7 +1991,8 @@ impl_lint_pass!(Methods => [
MANUAL_STR_REPEAT,
EXTEND_WITH_DRAIN,
MANUAL_SPLIT_ONCE,
- NEEDLESS_SPLITN
+ NEEDLESS_SPLITN,
+ UNNECESSARY_TO_OWNED
]);
/// Extracts a method call name, args, and `Span` of the method name.
@@ -2007,6 +2035,7 @@ impl<'tcx> LateLintPass<'tcx> for Methods {
single_char_add_str::check(cx, expr, args);
into_iter_on_ref::check(cx, expr, *method_span, method_call.ident.name, args);
single_char_pattern::check(cx, expr, method_call.ident.name, args);
+ unnecessary_to_owned::check(cx, expr, method_call.ident.name, args);
},
hir::ExprKind::Binary(op, lhs, rhs) if op.node == hir::BinOpKind::Eq || op.node == hir::BinOpKind::Ne => {
let mut info = BinaryExprInfo {
diff --git a/clippy_lints/src/methods/unnecessary_to_owned.rs b/clippy_lints/src/methods/unnecessary_to_owned.rs
new file mode 100644
index 00000000000..307de7bb65a
--- /dev/null
+++ b/clippy_lints/src/methods/unnecessary_to_owned.rs
@@ -0,0 +1,328 @@
+use clippy_utils::diagnostics::span_lint_and_sugg;
+use clippy_utils::source::snippet_opt;
+use clippy_utils::ty::{implements_trait, is_copy, peel_mid_ty_refs};
+use clippy_utils::{get_parent_expr, match_def_path, paths};
+use rustc_errors::Applicability;
+use rustc_hir::{def_id::DefId, BorrowKind, Expr, ExprKind};
+use rustc_lint::LateContext;
+use rustc_middle::mir::Mutability;
+use rustc_middle::ty::adjustment::{Adjust, Adjustment, OverloadedDeref};
+use rustc_middle::ty::subst::{GenericArg, GenericArgKind, SubstsRef};
+use rustc_middle::ty::{self, PredicateKind, ProjectionPredicate, TraitPredicate, Ty};
+use rustc_span::{sym, Symbol};
+use std::cmp::max;
+
+use super::UNNECESSARY_TO_OWNED;
+
+const TO_OWNED_LIKE_PATHS: &[&[&str]] = &[
+ &paths::COW_INTO_OWNED,
+ &paths::OS_STR_TO_OS_STRING,
+ &paths::PATH_TO_PATH_BUF,
+ &paths::SLICE_TO_VEC,
+ &paths::TO_OWNED_METHOD,
+ &paths::TO_STRING_METHOD,
+];
+
+pub fn check(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, method_name: Symbol, args: &'tcx [Expr<'tcx>]) {
+ if_chain! {
+ if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+ if TO_OWNED_LIKE_PATHS
+ .iter()
+ .any(|path| match_def_path(cx, method_def_id, path));
+ if let [receiver] = args;
+ then {
+ // At this point, we know the call is of a `to_owned`-like function. The functions
+ // `check_addr_of_expr` and `check_call_arg` determine whether the call is unnecessary
+ // based on its context, that is, whether it is a referent in an `AddrOf` expression or
+ // an argument in a function call.
+ if check_addr_of_expr(cx, expr, method_name, receiver) {
+ return;
+ }
+ check_call_arg(cx, expr, method_name, receiver);
+ }
+ }
+}
+
+/// Checks whether `expr` is a referent in an `AddrOf` expression and, if so, determines whether its
+/// call of a `to_owned`-like function is unnecessary.
+fn check_addr_of_expr(
+ cx: &LateContext<'tcx>,
+ expr: &'tcx Expr<'tcx>,
+ method_name: Symbol,
+ receiver: &'tcx Expr<'tcx>,
+) -> bool {
+ if_chain! {
+ if let Some(parent) = get_parent_expr(cx, expr);
+ if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind;
+ let adjustments = cx.typeck_results().expr_adjustments(parent).iter().collect::<Vec<_>>();
+ if let Some(target_ty) = match adjustments[..]
+ {
+ // For matching uses of `Cow::from`
+ [
+ Adjustment {
+ kind: Adjust::Deref(None),
+ ..
+ },
+ Adjustment {
+ kind: Adjust::Borrow(_),
+ target: target_ty,
+ },
+ ]
+ // For matching uses of arrays
+ | [
+ Adjustment {
+ kind: Adjust::Deref(None),
+ ..
+ },
+ Adjustment {
+ kind: Adjust::Borrow(_),
+ ..
+ },
+ Adjustment {
+ kind: Adjust::Pointer(_),
+ target: target_ty,
+ },
+ ]
+ // For matching everything else
+ | [
+ Adjustment {
+ kind: Adjust::Deref(None),
+ ..
+ },
+ Adjustment {
+ kind: Adjust::Deref(Some(OverloadedDeref { .. })),
+ ..
+ },
+ Adjustment {
+ kind: Adjust::Borrow(_),
+ target: target_ty,
+ },
+ ] => Some(target_ty),
+ _ => None,
+ };
+ then {
+ let (target_ty, n_target_refs) = peel_mid_ty_refs(target_ty);
+ let receiver_ty = cx.typeck_results().expr_ty(receiver);
+ let (receiver_ty, n_receiver_refs) = peel_mid_ty_refs(receiver_ty);
+ if_chain! {
+ if receiver_ty == target_ty;
+ if n_target_refs >= n_receiver_refs;
+ if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
+ then {
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_TO_OWNED,
+ parent.span,
+ &format!("unnecessary use of `{}`", method_name),
+ "use",
+ format!("{:&>width$}{}", "", receiver_snippet, width = n_target_refs - n_receiver_refs),
+ Applicability::MachineApplicable,
+ );
+ return true;
+ }
+ }
+ if implements_deref_trait(cx, receiver_ty, target_ty) {
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_TO_OWNED,
+ expr.span.with_lo(receiver.span.hi()),
+ &format!("unnecessary use of `{}`", method_name),
+ "remove this",
+ String::new(),
+ Applicability::MachineApplicable,
+ );
+ return true;
+ }
+ if_chain! {
+ if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef);
+ if implements_trait(cx, receiver_ty, as_ref_trait_id, &[GenericArg::from(target_ty)]);
+ if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
+ then {
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_TO_OWNED,
+ parent.span,
+ &format!("unnecessary use of `{}`", method_name),
+ "use",
+ format!("{}.as_ref()", receiver_snippet),
+ Applicability::MachineApplicable,
+ );
+ return true;
+ }
+ }
+ }
+ }
+ false
+}
+
+/// Checks whether `expr` is an argument in a function call and, if so, determines whether its call
+/// of a `to_owned`-like function is unnecessary.
+fn check_call_arg(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>, method_name: Symbol, receiver: &'tcx Expr<'tcx>) {
+ if_chain! {
+ if let Some((maybe_call, maybe_arg)) = skip_addr_of_ancestors(cx, expr);
+ if let Some((callee_def_id, call_substs, call_args)) = get_callee_substs_and_args(cx, maybe_call);
+ let fn_sig = cx.tcx.fn_sig(callee_def_id).skip_binder();
+ if let Some(i) = call_args.iter().position(|arg| arg.hir_id == maybe_arg.hir_id);
+ if let Some(input) = fn_sig.inputs().get(i);
+ let (input, n_refs) = peel_mid_ty_refs(input);
+ if let (trait_predicates, projection_predicates) = get_input_traits_and_projections(cx, callee_def_id, input);
+ if let Some(sized_def_id) = cx.tcx.lang_items().sized_trait();
+ if let [trait_predicate] = trait_predicates
+ .iter()
+ .filter(|trait_predicate| trait_predicate.def_id() != sized_def_id)
+ .collect::<Vec<_>>()[..];
+ if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
+ if let Some(as_ref_trait_id) = cx.tcx.get_diagnostic_item(sym::AsRef);
+ let receiver_ty = cx.typeck_results().expr_ty(receiver);
+ // If the callee has type parameters, they could appear in `projection_predicate.ty` or the
+ // types of `trait_predicate.trait_ref.substs`.
+ if if trait_predicate.def_id() == deref_trait_id {
+ if let [projection_predicate] = projection_predicates[..] {
+ let normalized_ty =
+ cx.tcx.subst_and_normalize_erasing_regions(call_substs, cx.param_env, projection_predicate.ty);
+ implements_deref_trait(cx, receiver_ty, normalized_ty)
+ } else {
+ false
+ }
+ } else if trait_predicate.def_id() == as_ref_trait_id {
+ let composed_substs = compose_substs(
+ cx,
+ &trait_predicate.trait_ref.substs.iter().skip(1).collect::<Vec<_>>()[..],
+ call_substs
+ );
+ implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
+ } else {
+ false
+ };
+ // We can't add an `&` when the trait is `Deref` because `Target = &T` won't match
+ // `Target = T`.
+ if n_refs > 0 || is_copy(cx, receiver_ty) || trait_predicate.def_id() != deref_trait_id;
+ let n_refs = max(n_refs, if is_copy(cx, receiver_ty) { 0 } else { 1 });
+ if let Some(receiver_snippet) = snippet_opt(cx, receiver.span);
+ then {
+ span_lint_and_sugg(
+ cx,
+ UNNECESSARY_TO_OWNED,
+ maybe_arg.span,
+ &format!("unnecessary use of `{}`", method_name),
+ "use",
+ format!("{:&>width$}{}", "", receiver_snippet, width = n_refs),
+ Applicability::MachineApplicable,
+ );
+ }
+ }
+}
+
+/// Walks an expression's ancestors until it finds a non-`AddrOf` expression. Returns the first such
+/// expression found (if any) along with the immediately prior expression.
+fn skip_addr_of_ancestors(
+ cx: &LateContext<'tcx>,
+ mut expr: &'tcx Expr<'tcx>,
+) -> Option<(&'tcx Expr<'tcx>, &'tcx Expr<'tcx>)> {
+ while let Some(parent) = get_parent_expr(cx, expr) {
+ if let ExprKind::AddrOf(BorrowKind::Ref, Mutability::Not, _) = parent.kind {
+ expr = parent;
+ } else {
+ return Some((parent, expr));
+ }
+ }
+ None
+}
+
+/// Checks whether an expression is a function or method call and, if so, returns its `DefId`,
+/// `Substs`, and arguments.
+fn get_callee_substs_and_args(
+ cx: &LateContext<'tcx>,
+ expr: &'tcx Expr<'tcx>,
+) -> Option<(DefId, SubstsRef<'tcx>, &'tcx [Expr<'tcx>])> {
+ if_chain! {
+ if let ExprKind::Call(callee, args) = expr.kind;
+ let callee_ty = cx.typeck_results().expr_ty(callee);
+ if let ty::FnDef(callee_def_id, _) = callee_ty.kind();
+ then {
+ let substs = cx.typeck_results().node_substs(callee.hir_id);
+ return Some((*callee_def_id, substs, args));
+ }
+ }
+ if_chain! {
+ if let ExprKind::MethodCall(_, _, args, _) = expr.kind;
+ if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
+ then {
+ let substs = cx.typeck_results().node_substs(expr.hir_id);
+ return Some((method_def_id, substs, args));
+ }
+ }
+ None
+}
+
+/// Returns the `TraitPredicate`s and `ProjectionPredicate`s for a function's input type.
+fn get_input_traits_and_projections(
+ cx: &LateContext<'tcx>,
+ callee_def_id: DefId,
+ input: Ty<'tcx>,
+) -> (Vec<TraitPredicate<'tcx>>, Vec<ProjectionPredicate<'tcx>>) {
+ let mut trait_predicates = Vec::new();
+ let mut projection_predicates = Vec::new();
+ for (predicate, _) in cx.tcx.predicates_of(callee_def_id).predicates.iter() {
+ // `substs` should have 1 + n elements. The first is the type on the left hand side of an
+ // `as`. The remaining n are trait parameters.
+ let is_input_substs = |substs: SubstsRef<'tcx>| {
+ if_chain! {
+ if let Some(arg) = substs.iter().next();
+ if let GenericArgKind::Type(arg_ty) = arg.unpack();
+ if arg_ty == input;
+ then {
+ true
+ } else {
+ false
+ }
+ }
+ };
+ match predicate.kind().skip_binder() {
+ PredicateKind::Trait(trait_predicate) => {
+ if is_input_substs(trait_predicate.trait_ref.substs) {
+ trait_predicates.push(trait_predicate);
+ }
+ },
+ PredicateKind::Projection(projection_predicate) => {
+ if is_input_substs(projection_predicate.projection_ty.substs) {
+ projection_predicates.push(projection_predicate);
+ }
+ },
+ _ => {},
+ }
+ }
+ (trait_predicates, projection_predicates)
+}
+
+/// Composes two substitutions by applying the latter to the types of the former.
+fn compose_substs(cx: &LateContext<'tcx>, left: &[GenericArg<'tcx>], right: SubstsRef<'tcx>) -> Vec<GenericArg<'tcx>> {
+ left.iter()
+ .map(|arg| {
+ if let GenericArgKind::Type(arg_ty) = arg.unpack() {
+ let normalized_ty = cx.tcx.subst_and_normalize_erasing_regions(right, cx.param_env, arg_ty);
+ GenericArg::from(normalized_ty)
+ } else {
+ *arg
+ }
+ })
+ .collect()
+}
+
+/// Helper function to check whether a type implements the `Deref` trait.
+fn implements_deref_trait(cx: &LateContext<'tcx>, ty: Ty<'tcx>, deref_target_ty: Ty<'tcx>) -> bool {
+ if_chain! {
+ if let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref);
+ if implements_trait(cx, ty, deref_trait_id, &[]);
+ if let Some(deref_target_id) = cx.tcx.lang_items().deref_target();
+ let substs = cx.tcx.mk_substs_trait(ty, &[]);
+ let projection_ty = cx.tcx.mk_projection(deref_target_id, substs);
+ let normalized_ty = cx.tcx.normalize_erasing_regions(cx.param_env, projection_ty);
+ if normalized_ty == deref_target_ty;
+ then {
+ true
+ } else {
+ false
+ }
+ }
+}
diff --git a/clippy_lints/src/unit_return_expecting_ord.rs b/clippy_lints/src/unit_return_expecting_ord.rs
index 9fb8f236899..fe35ff33d35 100644
--- a/clippy_lints/src/unit_return_expecting_ord.rs
+++ b/clippy_lints/src/unit_return_expecting_ord.rs
@@ -169,7 +169,7 @@ impl<'tcx> LateLintPass<'tcx> for UnitReturnExpectingOrd {
trait_name
),
Some(last_semi),
- &"probably caused by this trailing semicolon".to_string(),
+ "probably caused by this trailing semicolon",
);
},
None => {},
diff --git a/clippy_utils/src/paths.rs b/clippy_utils/src/paths.rs
index 6171823abbb..634a452d6f1 100644
--- a/clippy_utils/src/paths.rs
+++ b/clippy_utils/src/paths.rs
@@ -36,6 +36,7 @@ pub const CLONE_TRAIT_METHOD: [&str; 4] = ["core", "clone", "Clone", "clone"];
pub const CMP_MAX: [&str; 3] = ["core", "cmp", "max"];
pub const CMP_MIN: [&str; 3] = ["core", "cmp", "min"];
pub const COW: [&str; 3] = ["alloc", "borrow", "Cow"];
+pub const COW_INTO_OWNED: [&str; 4] = ["alloc", "borrow", "Cow", "into_owned"];
pub const CSTRING_AS_C_STR: [&str; 5] = ["std", "ffi", "c_str", "CString", "as_c_str"];
pub const DEFAULT_TRAIT_METHOD: [&str; 4] = ["core", "default", "Default", "default"];
pub const DEREF_MUT_TRAIT_METHOD: [&str; 5] = ["core", "ops", "deref", "DerefMut", "deref_mut"];
@@ -170,6 +171,7 @@ pub const SLICE_FROM_RAW_PARTS: [&str; 4] = ["core", "slice", "raw", "from_raw_p
pub const SLICE_FROM_RAW_PARTS_MUT: [&str; 4] = ["core", "slice", "raw", "from_raw_parts_mut"];
pub const SLICE_INTO_VEC: [&str; 4] = ["alloc", "slice", "<impl [T]>", "into_vec"];
pub const SLICE_ITER: [&str; 4] = ["core", "slice", "iter", "Iter"];
+pub const SLICE_TO_VEC: [&str; 4] = ["alloc", "slice", "<impl [T]>", "to_vec"];
pub const STDERR: [&str; 4] = ["std", "io", "stdio", "stderr"];
pub const STDOUT: [&str; 4] = ["std", "io", "stdio", "stdout"];
pub const CONVERT_IDENTITY: [&str; 3] = ["core", "convert", "identity"];
diff --git a/tests/ui/unnecessary_to_owned.fixed b/tests/ui/unnecessary_to_owned.fixed
new file mode 100644
index 00000000000..f1a5dc91a7e
--- /dev/null
+++ b/tests/ui/unnecessary_to_owned.fixed
@@ -0,0 +1,170 @@
+// run-rustfix
+
+#![allow(clippy::ptr_arg)]
+// Some of the expressions that `redundant_clone` flags overlap with ours. Enabling it interferes
+// with `rustfix`.
+#![allow(clippy::redundant_clone)]
+// `needless_borrow` is for checking the fixed code.
+#![warn(clippy::needless_borrow)]
+#![warn(clippy::unnecessary_to_owned)]
+
+use std::borrow::Cow;
+use std::ffi::{CStr, OsStr};
+use std::ops::Deref;
+
+#[derive(Clone)]
+struct X(String);
+
+impl Deref for X {
+ type Target = [u8];
+ fn deref(&self) -> &[u8] {
+ self.0.as_bytes()
+ }
+}
+
+impl AsRef<str> for X {
+ fn as_ref(&self) -> &str {
+ self.0.as_str()
+ }
+}
+
+impl ToString for X {
+ fn to_string(&self) -> String {
+ self.0.to_string()
+ }
+}
+
+impl X {
+ fn join(&self, other: impl AsRef<str>) -> Self {
+ let mut s = self.0.clone();
+ s.push_str(other.as_ref());
+ Self(s)
+ }
+}
+
+fn main() {
+ let c_str = CStr::from_bytes_with_nul(&[0]).unwrap();
+ let os_str = OsStr::new("x");
+ let path = std::path::Path::new("x");
+ let s = "x";
+ let array = ["x"];
+ let array_ref = &["x"];
+ let slice = &["x"][..];
+ let x = X(String::from("x"));
+
+ require_c_str(&Cow::from(c_str));
+ require_c_str(c_str);
+
+ require_os_str(os_str);
+ require_os_str(&Cow::from(os_str));
+ require_os_str(os_str);
+
+ require_path(path);
+ require_path(&Cow::from(path));
+ require_path(path);
+
+ require_str(s);
+ require_str(&Cow::from(s));
+ require_str(s);
+ require_str(x.as_ref());
+
+ require_slice(slice);
+ require_slice(&Cow::from(slice));
+ require_slice(array.as_ref());
+ require_slice(array_ref.as_ref());
+ require_slice(slice);
+ require_slice(&x);
+
+ require_x(&Cow::<X>::Owned(x.clone()));
+ require_x(&x);
+
+ require_deref_c_str(c_str);
+ require_deref_os_str(os_str);
+ require_deref_path(path);
+ require_deref_str(s);
+ require_deref_slice(slice);
+
+ require_impl_deref_c_str(c_str);
+ require_impl_deref_os_str(os_str);
+ require_impl_deref_path(path);
+ require_impl_deref_str(s);
+ require_impl_deref_slice(slice);
+
+ require_deref_str_slice(s, slice);
+ require_deref_slice_str(slice, s);
+
+ require_as_ref_c_str(c_str);
+ require_as_ref_os_str(os_str);
+ require_as_ref_path(path);
+ require_as_ref_str(s);
+ require_as_ref_str(&x);
+ require_as_ref_slice(array);
+ require_as_ref_slice(array_ref);
+ require_as_ref_slice(slice);
+
+ require_impl_as_ref_c_str(c_str);
+ require_impl_as_ref_os_str(os_str);
+ require_impl_as_ref_path(path);
+ require_impl_as_ref_str(s);
+ require_impl_as_ref_str(&x);
+ require_impl_as_ref_slice(array);
+ require_impl_as_ref_slice(array_ref);
+ require_impl_as_ref_slice(slice);
+
+ require_as_ref_str_slice(s, array);
+ require_as_ref_str_slice(s, array_ref);
+ require_as_ref_str_slice(s, slice);
+ require_as_ref_slice_str(array, s);
+ require_as_ref_slice_str(array_ref, s);
+ require_as_ref_slice_str(slice, s);
+
+ let _ = x.join(&x);
+
+ // negative tests
+ require_string(&s.to_string());
+ require_string(&Cow::from(s).into_owned());
+ require_string(&s.to_owned());
+ require_string(&x.to_string());
+
+ // `X` isn't copy.
+ require_deref_slice(x.to_owned());
+}
+
+fn require_c_str(_: &CStr) {}
+fn require_os_str(_: &OsStr) {}
+fn require_path(_: &std::path::Path) {}
+fn require_str(_: &str) {}
+fn require_slice<T>(_: &[T]) {}
+fn require_x(_: &X) {}
+
+fn require_deref_c_str<T: Deref<Target = CStr>>(_: T) {}
+fn require_deref_os_str<T: Deref<Target = OsStr>>(_: T) {}
+fn require_deref_path<T: Deref<Target = std::path::Path>>(_: T) {}
+fn require_deref_str<T: Deref<Target = str>>(_: T) {}
+fn require_deref_slice<T, U: Deref<Target = [T]>>(_: U) {}
+
+fn require_impl_deref_c_str(_: impl Deref<Target = CStr>) {}
+fn require_impl_deref_os_str(_: impl Deref<Target = OsStr>) {}
+fn require_impl_deref_path(_: impl Deref<Target = std::path::Path>) {}
+fn require_impl_deref_str(_: impl Deref<Target = str>) {}
+fn require_impl_deref_slice<T>(_: impl Deref<Target = [T]>) {}
+
+fn require_deref_str_slice<T: Deref<Target = str>, U, V: Deref<Target = [U]>>(_: T, _: V) {}
+fn require_deref_slice_str<T, U: Deref<Target = [T]>, V: Deref<Target = str>>(_: U, _: V) {}
+
+fn require_as_ref_c_str<T: AsRef<CStr>>(_: T) {}
+fn require_as_ref_os_str<T: AsRef<OsStr>>(_: T) {}
+fn require_as_ref_path<T: AsRef<std::path::Path>>(_: T) {}
+fn require_as_ref_str<T: AsRef<str>>(_: T) {}
+fn require_as_ref_slice<T, U: AsRef<[T]>>(_: U) {}
+
+fn require_impl_as_ref_c_str(_: impl AsRef<CStr>) {}
+fn require_impl_as_ref_os_str(_: impl AsRef<OsStr>) {}
+fn require_impl_as_ref_path(_: impl AsRef<std::path::Path>) {}
+fn require_impl_as_ref_str(_: impl AsRef<str>) {}
+fn require_impl_as_ref_slice<T>(_: impl AsRef<[T]>) {}
+
+fn require_as_ref_str_slice<T: AsRef<str>, U, V: AsRef<[U]>>(_: T, _: V) {}
+fn require_as_ref_slice_str<T, U: AsRef<[T]>, V: AsRef<str>>(_: U, _: V) {}
+
+fn require_string(_: &String) {}
diff --git a/tests/ui/unnecessary_to_owned.rs b/tests/ui/unnecessary_to_owned.rs
new file mode 100644
index 00000000000..081ff635bbd
--- /dev/null
+++ b/tests/ui/unnecessary_to_owned.rs
@@ -0,0 +1,170 @@
+// run-rustfix
+
+#![allow(clippy::ptr_arg)]
+// Some of the expressions that `redundant_clone` flags overlap with ours. Enabling it interferes
+// with `rustfix`.
+#![allow(clippy::redundant_clone)]
+// `needless_borrow` is for checking the fixed code.
+#![warn(clippy::needless_borrow)]
+#![warn(clippy::unnecessary_to_owned)]
+
+use std::borrow::Cow;
+use std::ffi::{CStr, OsStr};
+use std::ops::Deref;
+
+#[derive(Clone)]
+struct X(String);
+
+impl Deref for X {
+ type Target = [u8];
+ fn deref(&self) -> &[u8] {
+ self.0.as_bytes()
+ }
+}
+
+impl AsRef<str> for X {
+ fn as_ref(&self) -> &str {
+ self.0.as_str()
+ }
+}
+
+impl ToString for X {
+ fn to_string(&self) -> String {
+ self.0.to_string()
+ }
+}
+
+impl X {
+ fn join(&self, other: impl AsRef<str>) -> Self {
+ let mut s = self.0.clone();
+ s.push_str(other.as_ref());
+ Self(s)
+ }
+}
+
+fn main() {
+ let c_str = CStr::from_bytes_with_nul(&[0]).unwrap();
+ let os_str = OsStr::new("x");
+ let path = std::path::Path::new("x");
+ let s = "x";
+ let array = ["x"];
+ let array_ref = &["x"];
+ let slice = &["x"][..];
+ let x = X(String::from("x"));
+
+ require_c_str(&Cow::from(c_str).into_owned());
+ require_c_str(&c_str.to_owned());
+
+ require_os_str(&os_str.to_os_string());
+ require_os_str(&Cow::from(os_str).into_owned());
+ require_os_str(&os_str.to_owned());
+
+ require_path(&path.to_path_buf());
+ require_path(&Cow::from(path).into_owned());
+ require_path(&path.to_owned());
+
+ require_str(&s.to_string());
+ require_str(&Cow::from(s).into_owned());
+ require_str(&s.to_owned());
+ require_str(&x.to_string());
+
+ require_slice(&slice.to_vec());
+ require_slice(&Cow::from(slice).into_owned());
+ require_slice(&array.to_owned());
+ require_slice(&array_ref.to_owned());
+ require_slice(&slice.to_owned());
+ require_slice(&x.to_owned());
+
+ require_x(&Cow::<X>::Owned(x.clone()).into_owned());
+ require_x(&x.to_owned());
+
+ require_deref_c_str(c_str.to_owned());
+ require_deref_os_str(os_str.to_owned());
+ require_deref_path(path.to_owned());
+ require_deref_str(s.to_owned());
+ require_deref_slice(slice.to_owned());
+
+ require_impl_deref_c_str(c_str.to_owned());
+ require_impl_deref_os_str(os_str.to_owned());
+ require_impl_deref_path(path.to_owned());
+ require_impl_deref_str(s.to_owned());
+ require_impl_deref_slice(slice.to_owned());
+
+ require_deref_str_slice(s.to_owned(), slice.to_owned());
+ require_deref_slice_str(slice.to_owned(), s.to_owned());
+
+ require_as_ref_c_str(c_str.to_owned());
+ require_as_ref_os_str(os_str.to_owned());
+ require_as_ref_path(path.to_owned());
+ require_as_ref_str(s.to_owned());
+ require_as_ref_str(x.to_owned());
+ require_as_ref_slice(array.to_owned());
+ require_as_ref_slice(array_ref.to_owned());
+ require_as_ref_slice(slice.to_owned());
+
+ require_impl_as_ref_c_str(c_str.to_owned());
+ require_impl_as_ref_os_str(os_str.to_owned());
+ require_impl_as_ref_path(path.to_owned());
+ require_impl_as_ref_str(s.to_owned());
+ require_impl_as_ref_str(x.to_owned());
+ require_impl_as_ref_slice(array.to_owned());
+ require_impl_as_ref_slice(array_ref.to_owned());
+ require_impl_as_ref_slice(slice.to_owned());
+
+ require_as_ref_str_slice(s.to_owned(), array.to_owned());
+ require_as_ref_str_slice(s.to_owned(), array_ref.to_owned());
+ require_as_ref_str_slice(s.to_owned(), slice.to_owned());
+ require_as_ref_slice_str(array.to_owned(), s.to_owned());
+ require_as_ref_slice_str(array_ref.to_owned(), s.to_owned());
+ require_as_ref_slice_str(slice.to_owned(), s.to_owned());
+
+ let _ = x.join(&x.to_string());
+
+ // negative tests
+ require_string(&s.to_string());
+ require_string(&Cow::from(s).into_owned());
+ require_string(&s.to_owned());
+ require_string(&x.to_string());
+
+ // `X` isn't copy.
+ require_deref_slice(x.to_owned());
+}
+
+fn require_c_str(_: &CStr) {}
+fn require_os_str(_: &OsStr) {}
+fn require_path(_: &std::path::Path) {}
+fn require_str(_: &str) {}
+fn require_slice<T>(_: &[T]) {}
+fn require_x(_: &X) {}
+
+fn require_deref_c_str<T: Deref<Target = CStr>>(_: T) {}
+fn require_deref_os_str<T: Deref<Target = OsStr>>(_: T) {}
+fn require_deref_path<T: Deref<Target = std::path::Path>>(_: T) {}
+fn require_deref_str<T: Deref<Target = str>>(_: T) {}
+fn require_deref_slice<T, U: Deref<Target = [T]>>(_: U) {}
+
+fn require_impl_deref_c_str(_: impl Deref<Target = CStr>) {}
+fn require_impl_deref_os_str(_: impl Deref<Target = OsStr>) {}
+fn require_impl_deref_path(_: impl Deref<Target = std::path::Path>) {}
+fn require_impl_deref_str(_: impl Deref<Target = str>) {}
+fn require_impl_deref_slice<T>(_: impl Deref<Target = [T]>) {}
+
+fn require_deref_str_slice<T: Deref<Target = str>, U, V: Deref<Target = [U]>>(_: T, _: V) {}
+fn require_deref_slice_str<T, U: Deref<Target = [T]>, V: Deref<Target = str>>(_: U, _: V) {}
+
+fn require_as_ref_c_str<T: AsRef<CStr>>(_: T) {}
+fn require_as_ref_os_str<T: AsRef<OsStr>>(_: T) {}
+fn require_as_ref_path<T: AsRef<std::path::Path>>(_: T) {}
+fn require_as_ref_str<T: AsRef<str>>(_: T) {}
+fn require_as_ref_slice<T, U: AsRef<[T]>>(_: U) {}
+
+fn require_impl_as_ref_c_str(_: impl AsRef<CStr>) {}
+fn require_impl_as_ref_os_str(_: impl AsRef<OsStr>) {}
+fn require_impl_as_ref_path(_: impl AsRef<std::path::Path>) {}
+fn require_impl_as_ref_str(_: impl AsRef<str>) {}
+fn require_impl_as_ref_slice<T>(_: impl AsRef<[T]>) {}
+
+fn require_as_ref_str_slice<T: AsRef<str>, U, V: AsRef<[U]>>(_: T, _: V) {}
+fn require_as_ref_slice_str<T, U: AsRef<[T]>, V: AsRef<str>>(_: U, _: V) {}
+
+fn require_string(_: &String) {}
diff --git a/tests/ui/unnecessary_to_owned.stderr b/tests/ui/unnecessary_to_owned.stderr
new file mode 100644
index 00000000000..b15dd4c7ee7
--- /dev/null
+++ b/tests/ui/unnecessary_to_owned.stderr
@@ -0,0 +1,382 @@
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:55:36
+ |
+LL | require_c_str(&Cow::from(c_str).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+ |
+ = note: `-D clippy::unnecessary-to-owned` implied by `-D warnings`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:56:19
+ |
+LL | require_c_str(&c_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `c_str`
+
+error: unnecessary use of `to_os_string`
+ --> $DIR/unnecessary_to_owned.rs:58:20
+ |
+LL | require_os_str(&os_str.to_os_string());
+ | ^^^^^^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:59:38
+ |
+LL | require_os_str(&Cow::from(os_str).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:60:20
+ |
+LL | require_os_str(&os_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `to_path_buf`
+ --> $DIR/unnecessary_to_owned.rs:62:18
+ |
+LL | require_path(&path.to_path_buf());
+ | ^^^^^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:63:34
+ |
+LL | require_path(&Cow::from(path).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:64:18
+ |
+LL | require_path(&path.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `to_string`
+ --> $DIR/unnecessary_to_owned.rs:66:17
+ |
+LL | require_str(&s.to_string());
+ | ^^^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:67:30
+ |
+LL | require_str(&Cow::from(s).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:68:17
+ |
+LL | require_str(&s.to_owned());
+ | ^^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_string`
+ --> $DIR/unnecessary_to_owned.rs:69:17
+ |
+LL | require_str(&x.to_string());
+ | ^^^^^^^^^^^^^^ help: use: `x.as_ref()`
+
+error: unnecessary use of `to_vec`
+ --> $DIR/unnecessary_to_owned.rs:71:19
+ |
+LL | require_slice(&slice.to_vec());
+ | ^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:72:36
+ |
+LL | require_slice(&Cow::from(slice).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:73:19
+ |
+LL | require_slice(&array.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `array.as_ref()`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:74:19
+ |
+LL | require_slice(&array_ref.to_owned());
+ | ^^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref.as_ref()`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:75:19
+ |
+LL | require_slice(&slice.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:76:21
+ |
+LL | require_slice(&x.to_owned());
+ | ^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `into_owned`
+ --> $DIR/unnecessary_to_owned.rs:78:42
+ |
+LL | require_x(&Cow::<X>::Owned(x.clone()).into_owned());
+ | ^^^^^^^^^^^^^ help: remove this
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:79:15
+ |
+LL | require_x(&x.to_owned());
+ | ^^^^^^^^^^^^^ help: use: `&x`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:81:25
+ |
+LL | require_deref_c_str(c_str.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `c_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:82:26
+ |
+LL | require_deref_os_str(os_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:83:24
+ |
+LL | require_deref_path(path.to_owned());
+ | ^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:84:23
+ |
+LL | require_deref_str(s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:85:25
+ |
+LL | require_deref_slice(slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:87:30
+ |
+LL | require_impl_deref_c_str(c_str.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `c_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:88:31
+ |
+LL | require_impl_deref_os_str(os_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:89:29
+ |
+LL | require_impl_deref_path(path.to_owned());
+ | ^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:90:28
+ |
+LL | require_impl_deref_str(s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:91:30
+ |
+LL | require_impl_deref_slice(slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:93:29
+ |
+LL | require_deref_str_slice(s.to_owned(), slice.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:93:43
+ |
+LL | require_deref_str_slice(s.to_owned(), slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:94:29
+ |
+LL | require_deref_slice_str(slice.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:94:47
+ |
+LL | require_deref_slice_str(slice.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:96:26
+ |
+LL | require_as_ref_c_str(c_str.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `c_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:97:27
+ |
+LL | require_as_ref_os_str(os_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:98:25
+ |
+LL | require_as_ref_path(path.to_owned());
+ | ^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:99:24
+ |
+LL | require_as_ref_str(s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:100:24
+ |
+LL | require_as_ref_str(x.to_owned());
+ | ^^^^^^^^^^^^ help: use: `&x`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:101:26
+ |
+LL | require_as_ref_slice(array.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `array`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:102:26
+ |
+LL | require_as_ref_slice(array_ref.to_owned());
+ | ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:103:26
+ |
+LL | require_as_ref_slice(slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:105:31
+ |
+LL | require_impl_as_ref_c_str(c_str.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `c_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:106:32
+ |
+LL | require_impl_as_ref_os_str(os_str.to_owned());
+ | ^^^^^^^^^^^^^^^^^ help: use: `os_str`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:107:30
+ |
+LL | require_impl_as_ref_path(path.to_owned());
+ | ^^^^^^^^^^^^^^^ help: use: `path`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:108:29
+ |
+LL | require_impl_as_ref_str(s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:109:29
+ |
+LL | require_impl_as_ref_str(x.to_owned());
+ | ^^^^^^^^^^^^ help: use: `&x`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:110:31
+ |
+LL | require_impl_as_ref_slice(array.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `array`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:111:31
+ |
+LL | require_impl_as_ref_slice(array_ref.to_owned());
+ | ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:112:31
+ |
+LL | require_impl_as_ref_slice(slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:114:30
+ |
+LL | require_as_ref_str_slice(s.to_owned(), array.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:114:44
+ |
+LL | require_as_ref_str_slice(s.to_owned(), array.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `array`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:115:30
+ |
+LL | require_as_ref_str_slice(s.to_owned(), array_ref.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:115:44
+ |
+LL | require_as_ref_str_slice(s.to_owned(), array_ref.to_owned());
+ | ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:116:30
+ |
+LL | require_as_ref_str_slice(s.to_owned(), slice.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:116:44
+ |
+LL | require_as_ref_str_slice(s.to_owned(), slice.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:117:30
+ |
+LL | require_as_ref_slice_str(array.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `array`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:117:48
+ |
+LL | require_as_ref_slice_str(array.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:118:30
+ |
+LL | require_as_ref_slice_str(array_ref.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^^^^^^^^^ help: use: `array_ref`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:118:52
+ |
+LL | require_as_ref_slice_str(array_ref.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:119:30
+ |
+LL | require_as_ref_slice_str(slice.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^^^^^ help: use: `slice`
+
+error: unnecessary use of `to_owned`
+ --> $DIR/unnecessary_to_owned.rs:119:48
+ |
+LL | require_as_ref_slice_str(slice.to_owned(), s.to_owned());
+ | ^^^^^^^^^^^^ help: use: `s`
+
+error: unnecessary use of `to_string`
+ --> $DIR/unnecessary_to_owned.rs:121:20
+ |
+LL | let _ = x.join(&x.to_string());
+ | ^^^^^^^^^^^^^^ help: use: `&x`
+
+error: aborting due to 63 previous errors
+