diff --git a/alloc/tests/str.rs b/alloc/tests/str.rs
index c1dbbde08..0ba5d088f 100644
--- a/alloc/tests/str.rs
+++ b/alloc/tests/str.rs
@@ -1,3 +1,5 @@
+#![cfg_attr(not(bootstrap), allow(invalid_from_utf8))]
+
 use std::assert_matches::assert_matches;
 use std::borrow::Cow;
 use std::cmp::Ordering::{Equal, Greater, Less};
diff --git a/core/src/str/converts.rs b/core/src/str/converts.rs
index 5f8748206..0f23cf7ae 100644
--- a/core/src/str/converts.rs
+++ b/core/src/str/converts.rs
@@ -84,6 +84,7 @@ use super::Utf8Error;
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_str_from_utf8_shared", since = "1.63.0")]
 #[rustc_allow_const_fn_unstable(str_internals)]
+#[rustc_diagnostic_item = "str_from_utf8"]
 pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
     // FIXME: This should use `?` again, once it's `const`
     match run_utf8_validation(v) {
@@ -127,6 +128,7 @@ pub const fn from_utf8(v: &[u8]) -> Result<&str, Utf8Error> {
 /// errors that can be returned.
 #[stable(feature = "str_mut_extras", since = "1.20.0")]
 #[rustc_const_unstable(feature = "const_str_from_utf8", issue = "91006")]
+#[rustc_diagnostic_item = "str_from_utf8_mut"]
 pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
     // This should use `?` again, once it's `const`
     match run_utf8_validation(v) {
@@ -167,6 +169,7 @@ pub const fn from_utf8_mut(v: &mut [u8]) -> Result<&mut str, Utf8Error> {
 #[must_use]
 #[stable(feature = "rust1", since = "1.0.0")]
 #[rustc_const_stable(feature = "const_str_from_utf8_unchecked", since = "1.55.0")]
+#[rustc_diagnostic_item = "str_from_utf8_unchecked"]
 pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
     // SAFETY: the caller must guarantee that the bytes `v` are valid UTF-8.
     // Also relies on `&str` and `&[u8]` having the same layout.
@@ -194,6 +197,7 @@ pub const unsafe fn from_utf8_unchecked(v: &[u8]) -> &str {
 #[must_use]
 #[stable(feature = "str_mut_extras", since = "1.20.0")]
 #[rustc_const_unstable(feature = "const_str_from_utf8_unchecked_mut", issue = "91005")]
+#[rustc_diagnostic_item = "str_from_utf8_unchecked_mut"]
 pub const unsafe fn from_utf8_unchecked_mut(v: &mut [u8]) -> &mut str {
     // SAFETY: the caller must guarantee that the bytes `v`
     // are valid UTF-8, thus the cast to `*mut str` is safe.