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use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_with_context;
use clippy_utils::ty::{implements_trait, peel_mid_ty_refs};
use clippy_utils::{is_diag_item_method, is_diag_trait_item};
use if_chain::if_chain;
use rustc_errors::Applicability;
use rustc_hir as hir;
use rustc_lint::LateContext;
use rustc_span::sym;
use super::IMPLICIT_CLONE;
pub fn check(cx: &LateContext<'_>, method_name: &str, expr: &hir::Expr<'_>, recv: &hir::Expr<'_>) {
if_chain! {
if let Some(method_def_id) = cx.typeck_results().type_dependent_def_id(expr.hir_id);
if is_clone_like(cx, method_name, method_def_id);
let return_type = cx.typeck_results().expr_ty(expr);
let input_type = cx.typeck_results().expr_ty(recv);
let (input_type, ref_count) = peel_mid_ty_refs(input_type);
if let Some(ty_name) = input_type.ty_adt_def().map(|adt_def| cx.tcx.item_name(adt_def.did()));
if return_type == input_type;
if let Some(clone_trait) = cx.tcx.lang_items().clone_trait();
if implements_trait(cx, return_type, clone_trait, &[]);
then {
let mut app = Applicability::MachineApplicable;
let recv_snip = snippet_with_context(cx, recv.span, expr.span.ctxt(), "..", &mut app).0;
span_lint_and_sugg(
cx,
IMPLICIT_CLONE,
expr.span,
&format!("implicitly cloning a `{ty_name}` by calling `{method_name}` on its dereferenced type"),
"consider using",
if ref_count > 1 {
format!("({}{recv_snip}).clone()", "*".repeat(ref_count - 1))
} else {
format!("{recv_snip}.clone()")
},
app,
);
}
}
}
/// Returns true if the named method can be used to clone the receiver.
/// Note that `to_string` is not flagged by `implicit_clone`. So other lints that call
/// `is_clone_like` and that do flag `to_string` must handle it separately. See, e.g.,
/// `is_to_owned_like` in `unnecessary_to_owned.rs`.
pub fn is_clone_like(cx: &LateContext<'_>, method_name: &str, method_def_id: hir::def_id::DefId) -> bool {
match method_name {
"to_os_string" => is_diag_item_method(cx, method_def_id, sym::OsStr),
"to_owned" => is_diag_trait_item(cx, method_def_id, sym::ToOwned),
"to_path_buf" => is_diag_item_method(cx, method_def_id, sym::Path),
"to_vec" => cx
.tcx
.impl_of_method(method_def_id)
.filter(|&impl_did| cx.tcx.type_of(impl_did).is_slice() && cx.tcx.impl_trait_ref(impl_did).is_none())
.is_some(),
_ => false,
}
}
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