[Clippy] Swap unnecessary_to_owned to use diagnostic item instead of path

Author: GnomedDev

compiler/rustc_span/src/symbol.rs

@@ -1888,6 +1888,7 @@ symbols! {
         string_as_mut_str,
         string_as_str,
         string_deref_patterns,
+        string_from_utf8,
         string_insert_str,
         string_push_str,
         stringify,

library/alloc/src/string.rs

@@ -571,6 +571,7 @@ impl String {
     /// [`into_bytes`]: String::into_bytes
     #[inline]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(test), rustc_diagnostic_item = "string_from_utf8")]
     pub fn from_utf8(vec: Vec<u8>) -> Result<String, FromUtf8Error> {
         match str::from_utf8(&vec) {
             Ok(..) => Ok(String { vec }),

src/tools/clippy/clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -6,7 +6,7 @@ use clippy_utils::source::{snippet, SpanRangeExt};
 use clippy_utils::ty::{get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item, is_type_lang_item};
 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, match_def_path, paths, peel_middle_ty_refs,
+    fn_def_id, get_parent_expr, is_diag_item_method, is_diag_trait_item, peel_middle_ty_refs,
     return_ty,
 };
 use rustc_errors::Applicability;
@@ -250,7 +250,7 @@ fn check_string_from_utf8<'tcx>(cx: &LateContext<'tcx>, expr: &'tcx Expr<'tcx>,
     if let Some((call, arg)) = skip_addr_of_ancestors(cx, expr)
         && !arg.span.from_expansion()
         && let ExprKind::Call(callee, _) = call.kind
-        && fn_def_id(cx, call).is_some_and(|did| match_def_path(cx, did, &paths::STRING_FROM_UTF8))
+        && fn_def_id(cx, call).is_some_and(|did| cx.tcx.is_diagnostic_item(sym::string_from_utf8, did))
         && let Some(unwrap_call) = get_parent_expr(cx, call)
         && let ExprKind::MethodCall(unwrap_method_name, ..) = unwrap_call.kind
         && matches!(unwrap_method_name.ident.name, sym::unwrap | sym::expect)

src/tools/clippy/clippy_utils/src/paths.rs

@@ -61,7 +61,6 @@ pub const SYMBOL_INTERN: [&str; 4] = ["rustc_span", "symbol", "Symbol", "intern"
 pub const SYMBOL_TO_IDENT_STRING: [&str; 4] = ["rustc_span", "symbol", "Symbol", "to_ident_string"];
 pub const SYM_MODULE: [&str; 3] = ["rustc_span", "symbol", "sym"];
 pub const SYNTAX_CONTEXT: [&str; 3] = ["rustc_span", "hygiene", "SyntaxContext"];
-pub const STRING_FROM_UTF8: [&str; 4] = ["alloc", "string", "String", "from_utf8"];
 #[expect(clippy::invalid_paths)] // internal lints do not know about all external crates
 pub const TOKIO_FILE_OPTIONS: [&str; 5] = ["tokio", "fs", "file", "File", "options"];
 #[expect(clippy::invalid_paths)] // internal lints do not know about all external crates