Rollup merge of #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),
+                    ),
                 }
             }
         };