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Auto merge of #12091 - samueltardieu:issue-12068, r=Alexendoo

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Add .as_ref() to suggestion to remove .to_string()

The case of `.to_owned().split(…)` is treated specially in the `unnecessary_to_owned` lint. Test cases check that it works both for slices and for strings, but they missed a corner case: `x.to_string().split(…)` when `x` implements `AsRef<str>` but not `Deref<Target = str>`. In this case, it is wrong to suggest to remove `.to_string()` without adding `.as_ref()` instead.

Fix #12068

changelog: [`unnecessary_to_owned`]: suggest replacing `.to_string()` by `.as_ref()`
This commit is contained in:
bors 2024-01-05 14:54:40 +00:00
commit 2d6c2386f5
4 changed files with 65 additions and 14 deletions
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19
clippy_lints/src/methods/unnecessary_to_owned.rs
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@ -3,13 +3,13 @@ use super::unnecessary_iter_cloned::{self, is_into_iter};
use clippy_config::msrvs::{self, Msrv};
use clippy_utils::diagnostics::span_lint_and_sugg;
use clippy_utils::source::snippet_opt;
use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs};
use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy, is_type_lang_item, peel_mid_ty_refs};
use clippy_utils::visitors::find_all_ret_expressions;
use clippy_utils::{fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, return_ty};
use rustc_errors::Applicability;
use rustc_hir::def::{DefKind, Res};
use rustc_hir::def_id::DefId;
use rustc_hir::{BorrowKind, Expr, ExprKind, ItemKind, Node};
use rustc_hir::{BorrowKind, Expr, ExprKind, ItemKind, LangItem, Node};
use rustc_hir_typeck::{FnCtxt, Inherited};
use rustc_infer::infer::TyCtxtInferExt;
use rustc_lint::LateContext;
@ -246,6 +246,19 @@ fn check_split_call_arg(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: Symb
&& let Some(receiver_snippet) = snippet_opt(cx, receiver.span)
&& let Some(arg_snippet) = snippet_opt(cx, argument_expr.span)
{
// We may end-up here because of an expression like `x.to_string().split(…)` where the type of `x`
// implements `AsRef<str>` but does not implement `Deref<Target = str>`. In this case, we have to
// add `.as_ref()` to the suggestion.
let as_ref = if is_type_lang_item(cx, cx.typeck_results().expr_ty(expr), LangItem::String)
&& let Some(deref_trait_id) = cx.tcx.get_diagnostic_item(sym::Deref)
&& cx.get_associated_type(cx.typeck_results().expr_ty(receiver), deref_trait_id, "Target")
!= Some(cx.tcx.types.str_)
{
".as_ref()"
} else {
""
};
// The next suggestion may be incorrect because the removal of the `to_owned`-like
// function could cause the iterator to hold a reference to a resource that is used
// mutably. See https://github.com/rust-lang/rust-clippy/issues/8148.
@ -255,7 +268,7 @@ fn check_split_call_arg(cx: &LateContext<'_>, expr: &Expr<'_>, method_name: Symb
parent.span,
&format!("unnecessary use of `{method_name}`"),
"use",
format!("{receiver_snippet}.split({arg_snippet})"),
format!("{receiver_snippet}{as_ref}.split({arg_snippet})"),
Applicability::MaybeIncorrect,
);
return true;