Rollup merge of rust-lang#70913 - eddyb:rc-arc-diagnostic-items, r=matthewjasper

Replace "rc"/"arc" lang items with Rc/Arc diagnostic items. `Rc`/`Arc` should have no special semantics, so it seems appropriate for them to not be lang items. r? @matthewjasper

Author: Centril

src/liballoc/rc.rs

@@ -279,7 +279,8 @@ struct RcBox<T: ?Sized> {
 /// type `T`.
 ///
 /// [get_mut]: #method.get_mut
-#[cfg_attr(not(test), lang = "rc")]
+#[cfg_attr(all(bootstrap, not(test)), lang = "rc")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Rc")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Rc<T: ?Sized> {
  ptr: NonNull<RcBox<T>>,

src/liballoc/sync.rs

@@ -207,7 +207,8 @@ macro_rules! acquire {
 /// counting in general.
 ///
 /// [rc_examples]: ../../std/rc/index.html#examples
-#[cfg_attr(not(test), lang = "arc")]
+#[cfg_attr(all(bootstrap, not(test)), lang = "arc")]
+#[cfg_attr(not(test), rustc_diagnostic_item = "Arc")]
 #[stable(feature = "rust1", since = "1.0.0")]
 pub struct Arc<T: ?Sized> {
  ptr: NonNull<ArcInner<T>>,

src/librustc_error_codes/error_codes/E0152.md

@@ -5,8 +5,8 @@ Erroneous code example:
 ```compile_fail,E0152
 #![feature(lang_items)]
 
-#[lang = "arc"]
-struct Foo; // error: duplicate lang item found: `arc`
+#[lang = "owned_box"]
+struct Foo; // error: duplicate lang item found: `owned_box`
 ```
 
 Lang items are already implemented in the standard library. Unless you are

src/librustc_error_codes/error_codes/E0718.md

@@ -6,6 +6,6 @@ Examples of erroneous code:
 ```compile_fail,E0718
 #![feature(lang_items)]
 
-#[lang = "arc"]
+#[lang = "owned_box"]
 static X: u32 = 42;
 ```

src/librustc_hir/lang_items.rs

@@ -254,7 +254,4 @@ language_item_table! {
  AlignOffsetLangItem, "align_offset", align_offset_fn, Target::Fn;
 
  TerminationTraitLangItem, "termination", termination, Target::Trait;
-
- Arc, "arc", arc, Target::Struct;
- Rc, "rc", rc, Target::Struct;
 }

src/librustc_middle/ty/context.rs

@@ -2209,6 +2209,12 @@ impl<'tcx> TyCtxt<'tcx> {
  Some(self.mk_generic_adt(def_id, ty))
  }
 
+ #[inline]
+ pub fn mk_diagnostic_item(self, ty: Ty<'tcx>, name: Symbol) -> Option<Ty<'tcx>> {
+ let def_id = self.get_diagnostic_item(name)?;
+ Some(self.mk_generic_adt(def_id, ty))
+ }
+
  #[inline]
  pub fn mk_maybe_uninit(self, ty: Ty<'tcx>) -> Ty<'tcx> {
  let def_id = self.require_lang_item(lang_items::MaybeUninitLangItem, None);

src/librustc_middle/ty/mod.rs

@@ -1829,14 +1829,9 @@ bitflags! {
  const IS_BOX = 1 << 6;
  /// Indicates whether the type is `ManuallyDrop`.
  const IS_MANUALLY_DROP = 1 << 7;
- // FIXME(matthewjasper) replace these with diagnostic items
- /// Indicates whether the type is an `Arc`.
- const IS_ARC = 1 << 8;
- /// Indicates whether the type is an `Rc`.
- const IS_RC = 1 << 9;
  /// Indicates whether the variant list of this ADT is `#[non_exhaustive]`.
  /// (i.e., this flag is never set unless this ADT is an enum).
- const IS_VARIANT_LIST_NON_EXHAUSTIVE = 1 << 10;
+ const IS_VARIANT_LIST_NON_EXHAUSTIVE = 1 << 8;
  }
 }
 
@@ -2221,12 +2216,6 @@ impl<'tcx> AdtDef {
  if Some(did) == tcx.lang_items().manually_drop() {
  flags |= AdtFlags::IS_MANUALLY_DROP;
  }
- if Some(did) == tcx.lang_items().arc() {
- flags |= AdtFlags::IS_ARC;
- }
- if Some(did) == tcx.lang_items().rc() {
- flags |= AdtFlags::IS_RC;
- }
 
  AdtDef { did, variants, flags, repr }
  }
@@ -2305,16 +2294,6 @@ impl<'tcx> AdtDef {
  self.flags.contains(AdtFlags::IS_PHANTOM_DATA)
  }
 
- /// Returns `true` if this is `Arc<T>`.
- pub fn is_arc(&self) -> bool {
- self.flags.contains(AdtFlags::IS_ARC)
- }
-
- /// Returns `true` if this is `Rc<T>`.
- pub fn is_rc(&self) -> bool {
- self.flags.contains(AdtFlags::IS_RC)
- }
-
  /// Returns `true` if this is Box<T>.
  #[inline]
  pub fn is_box(&self) -> bool {

src/librustc_middle/ty/sty.rs

@@ -1864,24 +1864,6 @@ impl<'tcx> TyS<'tcx> {
  self.is_region_ptr() || self.is_unsafe_ptr() || self.is_fn_ptr()
  }
 
- /// Returns `true` if this type is an `Arc<T>`.
- #[inline]
- pub fn is_arc(&self) -> bool {
- match self.kind {
- Adt(def, _) => def.is_arc(),
- _ => false,
- }
- }
-
- /// Returns `true` if this type is an `Rc<T>`.
- #[inline]
- pub fn is_rc(&self) -> bool {
- match self.kind {
- Adt(def, _) => def.is_rc(),
- _ => false,
- }
- }
-
  #[inline]
  pub fn is_box(&self) -> bool {
  match self.kind {

src/librustc_mir/borrow_check/diagnostics/mod.rs

@@ -11,7 +11,7 @@ use rustc_middle::mir::{
 };
 use rustc_middle::ty::print::Print;
 use rustc_middle::ty::{self, DefIdTree, Ty, TyCtxt};
-use rustc_span::Span;
+use rustc_span::{symbol::sym, Span};
 use rustc_target::abi::VariantIdx;
 
 use super::borrow_set::BorrowData;
@@ -632,20 +632,20 @@ pub(super) enum BorrowedContentSource<'tcx> {
 }
 
 impl BorrowedContentSource<'tcx> {
- pub(super) fn describe_for_unnamed_place(&self) -> String {
+ pub(super) fn describe_for_unnamed_place(&self, tcx: TyCtxt<'_>) -> String {
  match *self {
  BorrowedContentSource::DerefRawPointer => "a raw pointer".to_string(),
  BorrowedContentSource::DerefSharedRef => "a shared reference".to_string(),
  BorrowedContentSource::DerefMutableRef => "a mutable reference".to_string(),
- BorrowedContentSource::OverloadedDeref(ty) => {
- if ty.is_rc() {
+ BorrowedContentSource::OverloadedDeref(ty) => match ty.kind {
+ ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Rc, def.did) => {
  "an `Rc`".to_string()
- } else if ty.is_arc() {
+ }
+ ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Arc, def.did) => {
  "an `Arc`".to_string()
- } else {
- format!("dereference of `{}`", ty)
  }
- }
+ _ => format!("dereference of `{}`", ty),
+ },
  BorrowedContentSource::OverloadedIndex(ty) => format!("index of `{}`", ty),
  }
  }
@@ -662,22 +662,22 @@ impl BorrowedContentSource<'tcx> {
  }
  }
 
- pub(super) fn describe_for_immutable_place(&self) -> String {
+ pub(super) fn describe_for_immutable_place(&self, tcx: TyCtxt<'_>) -> String {
  match *self {
  BorrowedContentSource::DerefRawPointer => "a `*const` pointer".to_string(),
  BorrowedContentSource::DerefSharedRef => "a `&` reference".to_string(),
  BorrowedContentSource::DerefMutableRef => {
  bug!("describe_for_immutable_place: DerefMutableRef isn't immutable")
  }
- BorrowedContentSource::OverloadedDeref(ty) => {
- if ty.is_rc() {
+ BorrowedContentSource::OverloadedDeref(ty) => match ty.kind {
+ ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Rc, def.did) => {
  "an `Rc`".to_string()
- } else if ty.is_arc() {
+ }
+ ty::Adt(def, _) if tcx.is_diagnostic_item(sym::Arc, def.did) => {
  "an `Arc`".to_string()
- } else {
- format!("a dereference of `{}`", ty)
  }
- }
+ _ => format!("a dereference of `{}`", ty),
+ },
  BorrowedContentSource::OverloadedIndex(ty) => format!("an index of `{}`", ty),
  }
  }

src/librustc_mir/borrow_check/diagnostics/move_errors.rs

@@ -377,7 +377,10 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, 'tcx> {
  span,
  &format!("`{}` which is behind a {}", place_desc, source_desc),
  ),
- (_, _) => self.cannot_move_out_of(span, &source.describe_for_unnamed_place()),
+ (_, _) => self.cannot_move_out_of(
+ span,
+ &source.describe_for_unnamed_place(self.infcx.tcx),
+ ),
  }
  }
  };