Make Clone a lang item and generate builtin impls.

Fixes #28229.
Fixes #24000.

src/libcore/array.rs

@@ -124,6 +124,7 @@ macro_rules! array_impls {
             }
 
             #[stable(feature = "rust1", since = "1.0.0")]
+            #[cfg(stage0)]
             impl<T:Copy> Clone for [T; $N] {
                 fn clone(&self) -> [T; $N] {
                     *self

src/libcore/clone.rs

@@ -88,6 +88,7 @@
 /// }
 /// ```
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg_attr(not(stage0), lang = "clone")]
 pub trait Clone : Sized {
     /// Returns a copy of the value.
     ///
@@ -131,6 +132,7 @@ pub struct AssertParamIsClone<T: Clone + ?Sized> { _field: ::marker::PhantomData
 pub struct AssertParamIsCopy<T: Copy + ?Sized> { _field: ::marker::PhantomData<T> }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(stage0)]
 impl<'a, T: ?Sized> Clone for &'a T {
     /// Returns a shallow copy of the reference.
     #[inline]
@@ -140,6 +142,7 @@ impl<'a, T: ?Sized> Clone for &'a T {
 macro_rules! clone_impl {
     ($t:ty) => {
         #[stable(feature = "rust1", since = "1.0.0")]
+        #[cfg(stage0)]
         impl Clone for $t {
             /// Returns a deep copy of the value.
             #[inline]

src/libcore/ptr.rs

@@ -876,6 +876,7 @@ pub fn eq<T: ?Sized>(a: *const T, b: *const T) -> bool {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(stage0)]
 impl<T: ?Sized> Clone for *const T {
     #[inline]
     fn clone(&self) -> *const T {
@@ -884,6 +885,7 @@ impl<T: ?Sized> Clone for *const T {
 }
 
 #[stable(feature = "rust1", since = "1.0.0")]
+#[cfg(stage0)]
 impl<T: ?Sized> Clone for *mut T {
     #[inline]
     fn clone(&self) -> *mut T {
@@ -895,6 +897,7 @@ impl<T: ?Sized> Clone for *mut T {
 macro_rules! fnptr_impls_safety_abi {
     ($FnTy: ty, $($Arg: ident),*) => {
         #[stable(feature = "rust1", since = "1.0.0")]
+        #[cfg(stage0)]
         impl<Ret, $($Arg),*> Clone for $FnTy {
             #[inline]
             fn clone(&self) -> Self {

src/libcore/tuple.rs

@@ -22,6 +22,7 @@ macro_rules! tuple_impls {
     )+) => {
         $(
             #[stable(feature = "rust1", since = "1.0.0")]
+            #[cfg(stage0)]
             impl<$($T:Clone),+> Clone for ($($T,)+) {
                 fn clone(&self) -> ($($T,)+) {
                     ($(self.$idx.clone(),)+)

src/librustc/ich/impls_ty.rs

@@ -721,6 +721,10 @@ impl<'a, 'gcx, 'tcx> HashStable<StableHashingContext<'a, 'gcx, 'tcx>> for ty::In
                 def_id.hash_stable(hcx, hasher);
                 t.hash_stable(hcx, hasher);
             }
+            ty::InstanceDef::BuiltinShim(def_id, t) => {
+                def_id.hash_stable(hcx, hasher);
+                t.hash_stable(hcx, hasher);
+            }
         }
     }
 }

src/librustc/middle/lang_items.rs

@@ -274,6 +274,7 @@ language_item_table! {
     SizedTraitLangItem,              "sized",                   sized_trait;
     UnsizeTraitLangItem,             "unsize",                  unsize_trait;
     CopyTraitLangItem,               "copy",                    copy_trait;
+    CloneTraitLangItem,              "clone",                   clone_trait;
     SyncTraitLangItem,               "sync",                    sync_trait;
     FreezeTraitLangItem,             "freeze",                  freeze_trait;
 
@@ -320,6 +321,9 @@ language_item_table! {
 
     StrEqFnLangItem,                 "str_eq",                  str_eq_fn;
 
+    CloneMethodLangItem,             "clone_method",            clone_method;
+    CloneFromMethodLangItem,         "clone_from_method",       clone_from_method;
+
     // A number of panic-related lang items. The `panic` item corresponds to
     // divide-by-zero and various panic cases with `match`. The
     // `panic_bounds_check` item is for indexing arrays.

src/librustc/traits/mod.rs

@@ -301,7 +301,7 @@ pub enum Vtable<'tcx, N> {
     VtableObject(VtableObjectData<'tcx, N>),
 
     /// Successful resolution for a builtin trait.
-    VtableBuiltin(VtableBuiltinData<N>),
+    VtableBuiltin(VtableBuiltinData<'tcx, N>),
 
     /// Vtable automatically generated for a closure. The def ID is the ID
     /// of the closure expression. This is a `VtableImpl` in spirit, but the
@@ -345,7 +345,9 @@ pub struct VtableDefaultImplData<N> {
 }
 
 #[derive(Clone)]
-pub struct VtableBuiltinData<N> {
+pub struct VtableBuiltinData<'tcx, N> {
+    /// `ty` can be used for generating shim for builtin implementations like `Clone::clone`.
+    pub ty: ty::Ty<'tcx>,
     pub nested: Vec<N>
 }
 
@@ -769,6 +771,7 @@ impl<'tcx, N> Vtable<'tcx, N> {
             }),
             VtableParam(n) => VtableParam(n.into_iter().map(f).collect()),
             VtableBuiltin(i) => VtableBuiltin(VtableBuiltinData {
+                ty: i.ty,
                 nested: i.nested.into_iter().map(f).collect(),
             }),
             VtableObject(o) => VtableObject(VtableObjectData {

src/librustc/traits/select.rs

@@ -1296,6 +1296,14 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
          } else if self.tcx().lang_items.unsize_trait() == Some(def_id) {
              self.assemble_candidates_for_unsizing(obligation, &mut candidates);
          } else {
+            if self.tcx().lang_items.clone_trait() == Some(def_id) {
+                // Same builtin conditions as `Copy`, i.e. every type which has builtin support
+                // for `Copy` also has builtin support for `Clone`, + tuples and arrays of `Clone`
+                // types have builtin support for `Clone`.
+                let clone_conditions = self.copy_conditions(obligation);
+                self.assemble_builtin_bound_candidates(clone_conditions, &mut candidates)?;
+            }
+
              self.assemble_closure_candidates(obligation, &mut candidates)?;
              self.assemble_fn_pointer_candidates(obligation, &mut candidates)?;
              self.assemble_candidates_from_impls(obligation, &mut candidates)?;
@@ -2164,8 +2172,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         match candidate {
             BuiltinCandidate { has_nested } => {
-                Ok(VtableBuiltin(
-                    self.confirm_builtin_candidate(obligation, has_nested)))
+                let data = self.confirm_builtin_candidate(obligation, has_nested);
+                Ok(VtableBuiltin(data))
             }
 
             ParamCandidate(param) => {
@@ -2257,7 +2265,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
     fn confirm_builtin_candidate(&mut self,
                                  obligation: &TraitObligation<'tcx>,
                                  has_nested: bool)
-                                 -> VtableBuiltinData<PredicateObligation<'tcx>>
+                                 -> VtableBuiltinData<'tcx, PredicateObligation<'tcx>>
     {
         debug!("confirm_builtin_candidate({:?}, {:?})",
                obligation, has_nested);
@@ -2271,6 +2279,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 _ if Some(trait_def) == self.tcx().lang_items.copy_trait() => {
                     self.copy_conditions(obligation)
                 }
+                _ if Some(trait_def) == self.tcx().lang_items.clone_trait() => {
+                    self.copy_conditions(obligation)
+                }
                 _ => bug!("unexpected builtin trait {:?}", trait_def)
             };
             let nested = match conditions {
@@ -2291,7 +2302,9 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
         debug!("confirm_builtin_candidate: obligations={:?}",
                obligations);
-        VtableBuiltinData { nested: obligations }
+
+        let self_ty = self.infcx.shallow_resolve(obligation.predicate.skip_binder().self_ty());
+        VtableBuiltinData { ty: self_ty, nested: obligations }
     }
 
     /// This handles the case where a `impl Foo for ..` impl is being used.
@@ -2598,8 +2611,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
     fn confirm_builtin_unsize_candidate(&mut self,
                                         obligation: &TraitObligation<'tcx>,)
-                                        -> Result<VtableBuiltinData<PredicateObligation<'tcx>>,
-                                                  SelectionError<'tcx>> {
+        -> Result<VtableBuiltinData<'tcx, PredicateObligation<'tcx>>, SelectionError<'tcx>>
+    {
         let tcx = self.tcx();
 
         // assemble_candidates_for_unsizing should ensure there are no late bound
@@ -2801,7 +2814,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
             _ => bug!()
         };
 
-        Ok(VtableBuiltinData { nested: nested })
+        Ok(VtableBuiltinData { ty: source, nested: nested })
     }
 
     ///////////////////////////////////////////////////////////////////////////

src/librustc/traits/structural_impls.rs

@@ -86,9 +86,9 @@ impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableClosureData<'tcx, N> {
     }
 }
 
-impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableBuiltinData<N> {
+impl<'tcx, N: fmt::Debug> fmt::Debug for traits::VtableBuiltinData<'tcx, N> {
     fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
-        write!(f, "VtableBuiltin(nested={:?})", self.nested)
+        write!(f, "VtableBuiltin(ty={:?}, nested={:?})", self.ty, self.nested)
     }
 }
 
@@ -300,7 +300,14 @@ impl<'a, 'tcx> Lift<'tcx> for traits::Vtable<'a, ()> {
                 })
             }
             traits::VtableParam(n) => Some(traits::VtableParam(n)),
-            traits::VtableBuiltin(d) => Some(traits::VtableBuiltin(d)),
+            traits::VtableBuiltin(traits::VtableBuiltinData { ty, nested }) => {
+                tcx.lift(&ty).map(|ty| {
+                    traits::VtableBuiltin(traits::VtableBuiltinData {
+                        ty,
+                        nested,
+                    })
+                })
+            }
             traits::VtableObject(traits::VtableObjectData {
                 upcast_trait_ref,
                 vtable_base,
@@ -378,9 +385,10 @@ impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableDefaultIm
     }
 }
 
-impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableBuiltinData<N> {
+impl<'tcx, N: TypeFoldable<'tcx>> TypeFoldable<'tcx> for traits::VtableBuiltinData<'tcx, N> {
     fn super_fold_with<'gcx: 'tcx, F: TypeFolder<'gcx, 'tcx>>(&self, folder: &mut F) -> Self {
         traits::VtableBuiltinData {
+            ty: self.ty.fold_with(folder),
             nested: self.nested.fold_with(folder),
         }
     }

src/librustc/ty/instance.rs

@@ -24,15 +24,22 @@ pub struct Instance<'tcx> {
 pub enum InstanceDef<'tcx> {
     Item(DefId),
     Intrinsic(DefId),
-    // <fn() as FnTrait>::call_*
-    // def-id is FnTrait::call_*
+
+    /// <fn() as FnTrait>::call_*
+    /// def-id is FnTrait::call_*
     FnPtrShim(DefId, Ty<'tcx>),
-    // <Trait as Trait>::fn
+
+    /// <Trait as Trait>::fn
     Virtual(DefId, usize),
-    // <[mut closure] as FnOnce>::call_once
+
+    /// <[mut closure] as FnOnce>::call_once
     ClosureOnceShim { call_once: DefId },
-    // drop_in_place::<T>; None for empty drop glue.
+
+    /// drop_in_place::<T>; None for empty drop glue.
     DropGlue(DefId, Option<Ty<'tcx>>),
+
+    /// Builtin method implementation, e.g. `Clone::clone`.
+    BuiltinShim(DefId, Ty<'tcx>),
 }
 
 impl<'tcx> InstanceDef<'tcx> {
@@ -43,9 +50,9 @@ impl<'tcx> InstanceDef<'tcx> {
             InstanceDef::FnPtrShim(def_id, _) |
             InstanceDef::Virtual(def_id, _) |
             InstanceDef::Intrinsic(def_id, ) |
-            InstanceDef::ClosureOnceShim { call_once: def_id }
-                => def_id,
-            InstanceDef::DropGlue(def_id, _) => def_id
+            InstanceDef::ClosureOnceShim { call_once: def_id } |
+            InstanceDef::DropGlue(def_id, _) |
+            InstanceDef::BuiltinShim(def_id, _) => def_id
         }
     }
 
@@ -80,6 +87,9 @@ impl<'tcx> fmt::Display for Instance<'tcx> {
             InstanceDef::DropGlue(_, ty) => {
                 write!(f, " - shim({:?})", ty)
             }
+            InstanceDef::BuiltinShim(_, ty) => {
+                write!(f, " - shim({:?})", ty)
+            }
         }
     }
 }

src/librustc/ty/mod.rs

@@ -2227,7 +2227,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             ty::InstanceDef::FnPtrShim(..) |
             ty::InstanceDef::Virtual(..) |
             ty::InstanceDef::ClosureOnceShim { .. } |
-            ty::InstanceDef::DropGlue(..) => {
+            ty::InstanceDef::DropGlue(..) |
+            ty::InstanceDef::BuiltinShim(..) => {
                 self.mir_shims(instance)
             }
         }