Add #[rustc_no_implicit_autorefs] and apply it to std methods

Author: Urgau

compiler/rustc_feature/src/builtin_attrs.rs

@@ -809,6 +809,10 @@ pub const 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 that should not autorefs in raw pointers context."
+    ),
     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

@@ -156,6 +156,9 @@ impl<'tcx> CheckAttrVisitor<'tcx> {
                 sym::rustc_never_returns_null_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_legacy_const_generics => {
                     self.check_rustc_legacy_const_generics(hir_id, attr, span, target, item)
                 }

compiler/rustc_span/src/symbol.rs

@@ -1582,6 +1582,7 @@ 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

@@ -1755,6 +1755,7 @@ impl String {
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_confusables("length", "size")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     pub fn len(&self) -> usize {
         self.vec.len()
     }
@@ -1773,6 +1774,7 @@ impl String {
     #[inline]
     #[must_use]
     #[stable(feature = "rust1", since = "1.0.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     pub 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

@@ -133,6 +133,7 @@ impl<T> [T] {
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_slice_len", since = "1.39.0")]
     #[rustc_allow_const_fn_unstable(ptr_metadata)]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[inline]
     #[must_use]
     pub const fn len(&self) -> usize {
@@ -152,6 +153,7 @@ 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 {
@@ -612,6 +614,7 @@ 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>
@@ -637,6 +640,7 @@ 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>
@@ -674,6 +678,7 @@ 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
@@ -716,6 +721,7 @@ 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

@@ -155,6 +155,7 @@ impl str {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[rustc_const_stable(feature = "const_str_len", since = "1.39.0")]
+    #[cfg_attr(not(bootstrap), rustc_no_implicit_autorefs)]
     #[must_use]
     #[inline]
     pub const fn len(&self) -> usize {
@@ -174,6 +175,7 @@ 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 {