Add #[rustc_no_implicit_autorefs] and apply it to std methods

compiler/rustc_feature/src/builtin_attrs.rs

@@ -931,6 +931,10 @@ pub static BUILTIN_ATTRIBUTES: &[BuiltinAttribute] = &[
         EncodeCrossCrate::Yes,
         "#[rustc_never_returns_null_ptr] is used to mark functions returning non-null pointers."
     ),
+    rustc_attr!(
+        rustc_no_implicit_autorefs, AttributeType::Normal, template!(Word), ErrorFollowing, EncodeCrossCrate::Yes,
+        "`#[rustc_no_implicit_autorefs]` is used to mark functions for which an autoref to the dereference of a raw pointer should not be used as an argument."
+    ),
     rustc_attr!(
         rustc_coherence_is_core, AttributeType::CrateLevel, template!(Word), ErrorFollowing, EncodeCrossCrate::No,
         "#![rustc_coherence_is_core] allows inherent methods on builtin types, only intended to be used in `core`."

compiler/rustc_passes/src/check_attr.rs

@@ -179,6 +179,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                         [sym::rustc_as_ptr, ..] => {
                             self.check_applied_to_fn_or_method(hir_id, attr, span, target)
                         }
+                        [sym::rustc_no_implicit_autorefs, ..] => {
+                            self.check_applied_to_fn_or_method(hir_id, attr, span, target)
+                        }
                         [sym::rustc_never_returns_null_ptr, ..] => {
                             self.check_applied_to_fn_or_method(hir_id, attr, span, target)
                         }

compiler/rustc_span/src/symbol.rs

@@ -1830,6 +1830,7 @@ symbols! {
         rustc_must_implement_one_of,
         rustc_never_returns_null_ptr,
         rustc_never_type_options,
+        rustc_no_implicit_autorefs,
         rustc_no_mir_inline,
         rustc_nonnull_optimization_guaranteed,
         rustc_nounwind,

library/alloc/src/string.rs

@@ -1832,6 +1832,7 @@ impl String {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_vec_string_slice", since = "1.87.0")]
     #[rustc_confusables("length", "size")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     pub const fn len(&self) -> usize {
         self.vec.len()
     }
@@ -1851,6 +1852,7 @@ impl String {
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_vec_string_slice", since = "1.87.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     pub const fn is_empty(&self) -> bool {
         self.len() == 0
     }

library/core/src/ops/index.rs

@@ -67,6 +67,7 @@ pub trait Index<Idx: ?Sized> {
     ///
     /// May panic if the index is out of bounds.
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[track_caller]
     fn index(&self, index: Idx) -> &Self::Output;
 }
@@ -171,6 +172,7 @@ pub trait IndexMut<Idx: ?Sized>: Index<Idx> {
     ///
     /// May panic if the index is out of bounds.
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[track_caller]
     fn index_mut(&mut self, index: Idx) -> &mut Self::Output;
 }

library/core/src/slice/mod.rs

@@ -109,6 +109,7 @@ impl<T> [T] {
     #[lang = "slice_len_fn"]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_slice_len", since = "1.39.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub const fn len(&self) -> usize {
@@ -128,6 +129,7 @@ impl<T> [T] {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_slice_is_empty", since = "1.39.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub const fn is_empty(&self) -> bool {
@@ -562,6 +564,7 @@ impl<T> [T] {
     /// assert_eq!(None, v.get(0..4));
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub fn get<I>(&self, index: I) -> Option<&I::Output>
@@ -587,6 +590,7 @@ impl<T> [T] {
     /// assert_eq!(x, &[0, 42, 2]);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub fn get_mut<I>(&mut self, index: I) -> Option<&mut I::Output>
@@ -624,6 +628,7 @@ impl<T> [T] {
     /// }
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub unsafe fn get_unchecked<I>(&self, index: I) -> &I::Output
@@ -666,6 +671,7 @@ impl<T> [T] {
     /// assert_eq!(x, &[1, 13, 4]);
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub unsafe fn get_unchecked_mut<I>(&mut self, index: I) -> &mut I::Output

library/core/src/str/mod.rs

@@ -134,6 +134,7 @@ impl str {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_str_len", since = "1.39.0")]
     #[rustc_diagnostic_item = "str_len"]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[must_use]
     #[inline]
     pub const fn len(&self) -> usize {
@@ -153,6 +154,7 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_str_is_empty", since = "1.39.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[must_use]
     #[inline]
     pub const fn is_empty(&self) -> bool {