Deprecate string_to_string

Author: smoelius

clippy_lints/src/declared_lints.rs

@@ -706,7 +706,6 @@ pub static LINTS: &[&crate::LintInfo] = &[
     crate::strings::STRING_FROM_UTF8_AS_BYTES_INFO,
     crate::strings::STRING_LIT_AS_BYTES_INFO,
     crate::strings::STRING_SLICE_INFO,
-    crate::strings::STRING_TO_STRING_INFO,
     crate::strings::STR_TO_STRING_INFO,
     crate::strings::TRIM_SPLIT_WHITESPACE_INFO,
     crate::strlen_on_c_strings::STRLEN_ON_C_STRINGS_INFO,

clippy_lints/src/deprecated_lints.rs

@@ -42,6 +42,8 @@ declare_with_version! { DEPRECATED(DEPRECATED_VERSION): &[(&str, &str)] = &[
     ("clippy::wrong_pub_self_convention", "`clippy::wrong_self_convention` now covers this case via the `avoid-breaking-exported-api` config"),
     #[clippy::version = "1.86.0"]
     ("clippy::option_map_or_err_ok", "`clippy::manual_ok_or` covers this case"),
+    #[clippy::version = "1.86.0"]
+    ("clippy::string_to_string", "`clippy:implicit_clone` covers this case"),
     // end deprecated lints. used by `cargo dev deprecate_lint`
 ]}
 

clippy_lints/src/lib.rs

@@ -823,7 +823,6 @@ pub fn register_lints(store: &mut rustc_lint::LintStore, conf: &'static Conf) {
     store.register_early_pass(|| Box::new(asm_syntax::InlineAsmX86IntelSyntax));
     store.register_late_pass(|_| Box::new(empty_drop::EmptyDrop));
     store.register_late_pass(|_| Box::new(strings::StrToString));
-    store.register_late_pass(|_| Box::new(strings::StringToString));
     store.register_late_pass(|_| Box::new(zero_sized_map_values::ZeroSizedMapValues));
     store.register_late_pass(|_| Box::<vec_init_then_push::VecInitThenPush>::default());
     store.register_late_pass(|_| Box::new(redundant_slicing::RedundantSlicing));

clippy_lints/src/strings.rs

@@ -411,58 +411,6 @@ impl<'tcx> LateLintPass<'tcx> for StrToString {
     }
 }
 
-declare_clippy_lint! {
-    /// ### What it does
-    /// This lint checks for `.to_string()` method calls on values of type `String`.
-    ///
-    /// ### Why restrict this?
-    /// The `to_string` method is also used on other types to convert them to a string.
-    /// When called on a `String` it only clones the `String`, which can be more specifically
-    /// expressed with `.clone()`.
-    ///
-    /// ### Example
-    /// ```no_run
-    /// let msg = String::from("Hello World");
-    /// let _ = msg.to_string();
-    /// ```
-    /// Use instead:
-    /// ```no_run
-    /// let msg = String::from("Hello World");
-    /// let _ = msg.clone();
-    /// ```
-    #[clippy::version = "pre 1.29.0"]
-    pub STRING_TO_STRING,
-    restriction,
-    "using `to_string()` on a `String`, which should be `clone()`"
-}
-
-declare_lint_pass!(StringToString => [STRING_TO_STRING]);
-
-impl<'tcx> LateLintPass<'tcx> for StringToString {
-    fn check_expr(&mut self, cx: &LateContext<'tcx>, expr: &Expr<'_>) {
-        if expr.span.from_expansion() {
-            return;
-        }
-
-        if let ExprKind::MethodCall(path, self_arg, [], _) = &expr.kind
-            && path.ident.name == sym::to_string
-            && let ty = cx.typeck_results().expr_ty(self_arg)
-            && is_type_lang_item(cx, ty, LangItem::String)
-        {
-            #[expect(clippy::collapsible_span_lint_calls, reason = "rust-clippy#7797")]
-            span_lint_and_then(
-                cx,
-                STRING_TO_STRING,
-                expr.span,
-                "`to_string()` called on a `String`",
-                |diag| {
-                    diag.help("consider using `.clone()`");
-                },
-            );
-        }
-    }
-}
-
 declare_clippy_lint! {
     /// ### What it does
     /// Warns about calling `str::trim` (or variants) before `str::split_whitespace`.

tests/ui/deprecated.rs

@@ -16,5 +16,6 @@
 #![warn(clippy::pub_enum_variant_names)] //~ ERROR: lint `clippy::pub_enum_variant_names`
 #![warn(clippy::wrong_pub_self_convention)] //~ ERROR: lint `clippy::wrong_pub_self_convention`
 #![warn(clippy::option_map_or_err_ok)] //~ ERROR: lint `clippy::option_map_or_err_ok`
+#![warn(clippy::string_to_string)] //~ ERROR: lint `clippy::string_to_string`
 
 fn main() {}

tests/ui/deprecated.stderr

@@ -85,5 +85,11 @@ error: lint `clippy::option_map_or_err_ok` has been removed: `clippy::manual_ok_
 LL | #![warn(clippy::option_map_or_err_ok)]
    |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
 
-error: aborting due to 14 previous errors
+error: lint `clippy::string_to_string` has been removed: `clippy:implicit_clone` covers this case
+  --> tests/ui/deprecated.rs:19:9
+   |
+LL | #![warn(clippy::string_to_string)]
+   |         ^^^^^^^^^^^^^^^^^^^^^^^^
+
+error: aborting due to 15 previous errors