Auto merge of rust-lang#9329 - xphoniex:fix-rust-lang#9317, r=flip1995

Skip `unnecessary_to_owned` when `t != t.to_string()` Fixes rust-lang#9317 changelog: [`unnecessary_to_owned`]: none

Author: bors

clippy_lints/src/methods/unnecessary_to_owned.rs

@@ -3,7 +3,8 @@ use super::unnecessary_iter_cloned::{self, is_into_iter};
 use clippy_utils::diagnostics::span_lint_and_sugg;
 use clippy_utils::source::snippet_opt;
 use clippy_utils::ty::{
- contains_ty, get_associated_type, get_iterator_item_ty, implements_trait, is_copy, peel_mid_ty_refs,
+ contains_ty, get_associated_type, get_iterator_item_ty, implements_trait, is_copy, is_type_diagnostic_item,
+ peel_mid_ty_refs,
 };
 use clippy_utils::{meets_msrv, msrvs};
 
@@ -279,7 +280,19 @@ fn check_other_call_arg<'tcx>(
  &trait_predicate.trait_ref.substs.iter().skip(1).collect::<Vec<_>>()[..],
  call_substs,
  );
- implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
+ // if `expr` is a `String` and generic target is [u8], skip
+ // (https://github.com/rust-lang/rust-clippy/issues/9317).
+ if let [subst] = composed_substs[..]
+ && let GenericArgKind::Type(arg_ty) = subst.unpack()
+ && arg_ty.is_slice()
+ && let inner_ty = arg_ty.builtin_index().unwrap()
+ && let ty::Uint(ty::UintTy::U8) = inner_ty.kind()
+ && let self_ty = cx.typeck_results().expr_ty(expr).peel_refs()
+ && is_type_diagnostic_item(cx, self_ty, sym::String) {
+ false
+ } else {
+ implements_trait(cx, receiver_ty, as_ref_trait_id, &composed_substs)
+ }
  } else {
  false
  };

tests/ui/unnecessary_to_owned.fixed

@@ -329,3 +329,31 @@ mod issue_8759_variant {
  rw.set_view(&rw.default_view().to_owned());
  }
 }
+
+mod issue_9317 {
+ #![allow(dead_code)]
+
+ struct Bytes {}
+
+ impl ToString for Bytes {
+ fn to_string(&self) -> String {
+ "123".to_string()
+ }
+ }
+
+ impl AsRef<[u8]> for Bytes {
+ fn as_ref(&self) -> &[u8] {
+ &[1, 2, 3]
+ }
+ }
+
+ fn consume<C: AsRef<[u8]>>(c: C) {
+ let _ = c;
+ }
+
+ pub fn main() {
+ let b = Bytes {};
+ // Should not lint.
+ consume(b.to_string());
+ }
+}

tests/ui/unnecessary_to_owned.rs

@@ -329,3 +329,31 @@ mod issue_8759_variant {
  rw.set_view(&rw.default_view().to_owned());
  }
 }
+
+mod issue_9317 {
+ #![allow(dead_code)]
+
+ struct Bytes {}
+
+ impl ToString for Bytes {
+ fn to_string(&self) -> String {
+ "123".to_string()
+ }
+ }
+
+ impl AsRef<[u8]> for Bytes {
+ fn as_ref(&self) -> &[u8] {
+ &[1, 2, 3]
+ }
+ }
+
+ fn consume<C: AsRef<[u8]>>(c: C) {
+ let _ = c;
+ }
+
+ pub fn main() {
+ let b = Bytes {};
+ // Should not lint.
+ consume(b.to_string());
+ }
+}