Implement RFC 1861: Extern types

src/libcore/ptr.rs

@@ -485,8 +485,9 @@ impl<T: ?Sized> *const T {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn is_null(self) -> bool where T: Sized {
-        self == null()
+    pub fn is_null(self) -> bool {
+        // cast to () pointer, as T may not be sized
+        self as *const () == null()
     }
 
     /// Returns `None` if the pointer is null, or else returns a reference to
@@ -517,7 +518,7 @@ impl<T: ?Sized> *const T {
     /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
     #[inline]
-    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> where T: Sized {
+    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
         if self.is_null() {
             None
         } else {
@@ -1116,8 +1117,9 @@ impl<T: ?Sized> *mut T {
     /// ```
     #[stable(feature = "rust1", since = "1.0.0")]
     #[inline]
-    pub fn is_null(self) -> bool where T: Sized {
-        self == null_mut()
+    pub fn is_null(self) -> bool {
+        // cast to () pointer, as T may not be sized
+        self as *mut () == null_mut()
     }
 
     /// Returns `None` if the pointer is null, or else returns a reference to
@@ -1148,7 +1150,7 @@ impl<T: ?Sized> *mut T {
     /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
     #[inline]
-    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> where T: Sized {
+    pub unsafe fn as_ref<'a>(self) -> Option<&'a T> {
         if self.is_null() {
             None
         } else {
@@ -1272,7 +1274,7 @@ impl<T: ?Sized> *mut T {
     /// ```
     #[stable(feature = "ptr_as_ref", since = "1.9.0")]
     #[inline]
-    pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> where T: Sized {
+    pub unsafe fn as_mut<'a>(self) -> Option<&'a mut T> {
         if self.is_null() {
             None
         } else {

src/librustc/hir/def.rs

@@ -35,6 +35,7 @@ pub enum Def {
     Variant(DefId),
     Trait(DefId),
     TyAlias(DefId),
+    TyForeign(DefId),
     AssociatedTy(DefId),
     PrimTy(hir::PrimTy),
     TyParam(DefId),
@@ -152,7 +153,7 @@ impl Def {
             Def::AssociatedTy(id) | Def::TyParam(id) | Def::Struct(id) | Def::StructCtor(id, ..) |
             Def::Union(id) | Def::Trait(id) | Def::Method(id) | Def::Const(id) |
             Def::AssociatedConst(id) | Def::Macro(id, ..) |
-            Def::GlobalAsm(id) => {
+            Def::GlobalAsm(id) | Def::TyForeign(id) => {
                 id
             }
 
@@ -186,6 +187,7 @@ impl Def {
             Def::StructCtor(.., CtorKind::Fictive) => bug!("impossible struct constructor"),
             Def::Union(..) => "union",
             Def::Trait(..) => "trait",
+            Def::TyForeign(..) => "foreign type",
             Def::Method(..) => "method",
             Def::Const(..) => "constant",
             Def::AssociatedConst(..) => "associated constant",

src/librustc/hir/intravisit.rs

@@ -704,6 +704,7 @@ pub fn walk_foreign_item<'v, V: Visitor<'v>>(visitor: &mut V, foreign_item: &'v
             }
         }
         ForeignItemStatic(ref typ, _) => visitor.visit_ty(typ),
+        ForeignItemType => (),
     }
 
     walk_list!(visitor, visit_attribute, &foreign_item.attrs);

src/librustc/hir/lowering.rs

@@ -1722,6 +1722,9 @@ impl<'a> LoweringContext<'a> {
                     ForeignItemKind::Static(ref t, m) => {
                         hir::ForeignItemStatic(this.lower_ty(t), m)
                     }
+                    ForeignItemKind::Ty => {
+                        hir::ForeignItemType
+                    }
                 },
                 vis: this.lower_visibility(&i.vis, None),
                 span: i.span,

src/librustc/hir/mod.rs

@@ -1912,13 +1912,16 @@ pub enum ForeignItem_ {
     /// A foreign static item (`static ext: u8`), with optional mutability
     /// (the boolean is true when mutable)
     ForeignItemStatic(P<Ty>, bool),
+    /// A foreign type
+    ForeignItemType,
 }
 
 impl ForeignItem_ {
     pub fn descriptive_variant(&self) -> &str {
         match *self {
             ForeignItemFn(..) => "foreign function",
             ForeignItemStatic(..) => "foreign static item",
+            ForeignItemType => "foreign type",
         }
     }
 }

src/librustc/hir/print.rs

@@ -478,6 +478,13 @@ impl<'a> State<'a> {
                 self.end()?; // end the head-ibox
                 self.end() // end the outer cbox
             }
+            hir::ForeignItemType => {
+                self.head(&visibility_qualified(&item.vis, "type"))?;
+                self.print_name(item.name)?;
+                self.s.word(";")?;
+                self.end()?; // end the head-ibox
+                self.end() // end the outer cbox
+            }
         }
     }
 

src/librustc/ich/impls_hir.rs

@@ -977,7 +977,8 @@ impl_stable_hash_for!(struct hir::ForeignItem {
 
 impl_stable_hash_for!(enum hir::ForeignItem_ {
     ForeignItemFn(fn_decl, arg_names, generics),
-    ForeignItemStatic(ty, is_mutbl)
+    ForeignItemStatic(ty, is_mutbl),
+    ForeignItemType
 });
 
 impl_stable_hash_for!(enum hir::Stmt_ {
@@ -1086,6 +1087,7 @@ impl_stable_hash_for!(enum hir::def::Def {
     PrimTy(prim_ty),
     TyParam(def_id),
     SelfTy(trait_def_id, impl_def_id),
+    TyForeign(def_id),
     Fn(def_id),
     Const(def_id),
     Static(def_id, is_mutbl),

src/librustc/ich/impls_ty.rs

@@ -610,8 +610,7 @@ for ty::TypeVariants<'gcx>
                 def_id.hash_stable(hcx, hasher);
                 closure_substs.hash_stable(hcx, hasher);
             }
-            TyGenerator(def_id, closure_substs, interior)
-             => {
+            TyGenerator(def_id, closure_substs, interior) => {
                 def_id.hash_stable(hcx, hasher);
                 closure_substs.hash_stable(hcx, hasher);
                 interior.hash_stable(hcx, hasher);
@@ -630,6 +629,9 @@ for ty::TypeVariants<'gcx>
             TyParam(param_ty) => {
                 param_ty.hash_stable(hcx, hasher);
             }
+            TyForeign(def_id) => {
+                def_id.hash_stable(hcx, hasher);
+            }
             TyInfer(..) => {
                 bug!("ty::TypeVariants::hash_stable() - Unexpected variant {:?}.", *self)
             }

src/librustc/infer/freshen.rs

@@ -312,6 +312,7 @@ impl<'a, 'gcx, 'tcx> TypeFolder<'gcx, 'tcx> for TypeFreshener<'a, 'gcx, 'tcx> {
             ty::TyNever |
             ty::TyTuple(..) |
             ty::TyProjection(..) |
+            ty::TyForeign(..) |
             ty::TyParam(..) |
             ty::TyAnon(..) => {
                 t.super_fold_with(self)

src/librustc/middle/resolve_lifetime.rs

@@ -365,6 +365,9 @@ impl<'a, 'tcx> Visitor<'tcx> for LifetimeContext<'a, 'tcx> {
             hir::ForeignItemStatic(..) => {
                 intravisit::walk_foreign_item(self, item);
             }
+            hir::ForeignItemType => {
+                intravisit::walk_foreign_item(self, item);
+            }
         }
     }
 

src/librustc/traits/coherence.rs

@@ -304,6 +304,10 @@ fn ty_is_local_constructor(ty: Ty, infer_is_local: InferIsLocal)-> bool {
             def.did.is_local()
         }
 
+        ty::TyForeign(did) => {
+            did.is_local()
+        }
+
         ty::TyDynamic(ref tt, ..) => {
             tt.principal().map_or(false, |p| p.def_id().is_local())
         }

src/librustc/traits/error_reporting.rs

@@ -255,6 +255,7 @@ impl<'a, 'gcx, 'tcx> InferCtxt<'a, 'gcx, 'tcx> {
                     AdtKind::Enum => Some(17),
                 },
                 ty::TyGenerator(..) => Some(18),
+                ty::TyForeign(..) => Some(19),
                 ty::TyInfer(..) | ty::TyError => None
             }
         }

src/librustc/traits/select.rs

@@ -1705,6 +1705,12 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                     // say nothing; a candidate may be added by
                     // `assemble_candidates_from_object_ty`.
                 }
+                ty::TyForeign(..) => {
+                    // Since the contents of foreign types is unknown,
+                    // we don't add any `..` impl. Default traits could
+                    // still be provided by a manual implementation for
+                    // this trait and type.
+                }
                 ty::TyParam(..) |
                 ty::TyProjection(..) => {
                     // In these cases, we don't know what the actual
@@ -2022,7 +2028,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Where(ty::Binder(Vec::new()))
             }
 
-            ty::TyStr | ty::TySlice(_) | ty::TyDynamic(..) => Never,
+            ty::TyStr | ty::TySlice(_) | ty::TyDynamic(..) | ty::TyForeign(..) => Never,
 
             ty::TyTuple(tys, _) => {
                 Where(ty::Binder(tys.last().into_iter().cloned().collect()))
@@ -2066,7 +2072,8 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
                 Where(ty::Binder(Vec::new()))
             }
 
-            ty::TyDynamic(..) | ty::TyStr | ty::TySlice(..) | ty::TyGenerator(..) |
+            ty::TyDynamic(..) | ty::TyStr | ty::TySlice(..) |
+            ty::TyGenerator(..) | ty::TyForeign(..) |
             ty::TyRef(_, ty::TypeAndMut { ty: _, mutbl: hir::MutMutable }) => {
                 Never
             }
@@ -2148,6 +2155,7 @@ impl<'cx, 'gcx, 'tcx> SelectionContext<'cx, 'gcx, 'tcx> {
 
             ty::TyDynamic(..) |
             ty::TyParam(..) |
+            ty::TyForeign(..) |
             ty::TyProjection(..) |
             ty::TyInfer(ty::TyVar(_)) |
             ty::TyInfer(ty::FreshTy(_)) |

src/librustc/ty/context.rs

@@ -1610,7 +1610,7 @@ impl<'a, 'tcx> TyCtxt<'a, 'tcx, 'tcx> {
     pub fn print_debug_stats(self) {
         sty_debug_print!(
             self,
-            TyAdt, TyArray, TySlice, TyRawPtr, TyRef, TyFnDef, TyFnPtr, TyGenerator,
+            TyAdt, TyArray, TySlice, TyRawPtr, TyRef, TyFnDef, TyFnPtr, TyGenerator, TyForeign,
             TyDynamic, TyClosure, TyTuple, TyParam, TyInfer, TyProjection, TyAnon);
 
         println!("Substs interner: #{}", self.interners.substs.borrow().len());
@@ -1861,6 +1861,10 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
         self.mk_ty(TyAdt(def, substs))
     }
 
+    pub fn mk_foreign(self, def_id: DefId) -> Ty<'tcx> {
+        self.mk_ty(TyForeign(def_id))
+    }
+
     pub fn mk_box(self, ty: Ty<'tcx>) -> Ty<'tcx> {
         let def_id = self.require_lang_item(lang_items::OwnedBoxLangItem);
         let adt_def = self.adt_def(def_id);

src/librustc/ty/error.rs

@@ -182,6 +182,7 @@ impl<'a, 'gcx, 'lcx, 'tcx> ty::TyS<'tcx> {
             ty::TyTuple(ref tys, _) if tys.is_empty() => self.to_string(),
 
             ty::TyAdt(def, _) => format!("{} `{}`", def.descr(), tcx.item_path_str(def.did)),
+            ty::TyForeign(def_id) => format!("extern type `{}`", tcx.item_path_str(def_id)),
             ty::TyArray(_, n) => {
                 if let ConstVal::Integral(ConstInt::Usize(n)) = n.val {
                     format!("array of {} elements", n)

src/librustc/ty/fast_reject.rs

@@ -49,6 +49,7 @@ pub enum SimplifiedTypeGen<D>
     AnonSimplifiedType(D),
     FunctionSimplifiedType(usize),
     ParameterSimplifiedType,
+    ForeignSimplifiedType(DefId),
 }
 
 /// Tries to simplify a type by dropping type parameters, deref'ing away any reference types, etc.
@@ -113,6 +114,9 @@ pub fn simplify_type<'a, 'gcx, 'tcx>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
         ty::TyAnon(def_id, _) => {
             Some(AnonSimplifiedType(def_id))
         }
+        ty::TyForeign(def_id) => {
+            Some(ForeignSimplifiedType(def_id))
+        }
         ty::TyInfer(_) | ty::TyError => None,
     }
 }
@@ -140,6 +144,7 @@ impl<D: Copy + Debug + Ord + Eq + Hash> SimplifiedTypeGen<D> {
             AnonSimplifiedType(d) => AnonSimplifiedType(map(d)),
             FunctionSimplifiedType(n) => FunctionSimplifiedType(n),
             ParameterSimplifiedType => ParameterSimplifiedType,
+            ForeignSimplifiedType(d) => ForeignSimplifiedType(d),
         }
     }
 }
@@ -172,6 +177,7 @@ impl<'gcx, D> HashStable<StableHashingContext<'gcx>> for SimplifiedTypeGen<D>
             GeneratorSimplifiedType(d) => d.hash_stable(hcx, hasher),
             AnonSimplifiedType(d) => d.hash_stable(hcx, hasher),
             FunctionSimplifiedType(n) => n.hash_stable(hcx, hasher),
+            ForeignSimplifiedType(d) => d.hash_stable(hcx, hasher),
         }
     }
 }

src/librustc/ty/flags.rs

@@ -63,7 +63,8 @@ impl FlagComputation {
             &ty::TyFloat(_) |
             &ty::TyUint(_) |
             &ty::TyNever |
-            &ty::TyStr => {
+            &ty::TyStr |
+            &ty::TyForeign(..) => {
             }
 
             // You might think that we could just return TyError for

src/librustc/ty/item_path.rs

@@ -281,6 +281,8 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
                 }
             }
 
+            ty::TyForeign(did) => self.push_item_path(buffer, did),
+
             ty::TyBool |
             ty::TyChar |
             ty::TyInt(_) |
@@ -344,8 +346,9 @@ pub fn characteristic_def_id_of_type(ty: Ty) -> Option<DefId> {
                                       .next(),
 
         ty::TyFnDef(def_id, _) |
-        ty::TyClosure(def_id, _) => Some(def_id),
-        ty::TyGenerator(def_id, _, _) => Some(def_id),
+        ty::TyClosure(def_id, _) |
+        ty::TyGenerator(def_id, _, _) |
+        ty::TyForeign(def_id) => Some(def_id),
 
         ty::TyBool |
         ty::TyChar |

src/librustc/ty/layout.rs

@@ -1141,14 +1141,15 @@ impl<'a, 'tcx> Layout {
                 Ok(Scalar { value: Pointer, non_zero: non_zero })
             } else {
                 let unsized_part = tcx.struct_tail(pointee);
-                let meta = match unsized_part.sty {
-                    ty::TySlice(_) | ty::TyStr => {
-                        Int(dl.ptr_sized_integer())
-                    }
-                    ty::TyDynamic(..) => Pointer,
-                    _ => return Err(LayoutError::Unknown(unsized_part))
-                };
-                Ok(FatPointer { metadata: meta, non_zero: non_zero })
+                match unsized_part.sty {
+                    ty::TySlice(_) | ty::TyStr => Ok(FatPointer {
+                        metadata: Int(dl.ptr_sized_integer()),
+                        non_zero: non_zero
+                    }),
+                    ty::TyDynamic(..) => Ok(FatPointer { metadata: Pointer, non_zero: non_zero }),
+                    ty::TyForeign(..) => Ok(Scalar { value: Pointer, non_zero: non_zero }),
+                    _ => Err(LayoutError::Unknown(unsized_part)),
+                }
             }
         };
 
@@ -1239,7 +1240,7 @@ impl<'a, 'tcx> Layout {
                     non_zero: false
                 }
             }
-            ty::TyDynamic(..) => {
+            ty::TyDynamic(..) | ty::TyForeign(..) => {
                 let mut unit = Struct::new(dl, &vec![], &ReprOptions::default(),
                   StructKind::AlwaysSizedUnivariant, ty)?;
                 unit.sized = false;
@@ -2252,7 +2253,8 @@ impl<'a, 'tcx> TyLayout<'tcx> {
             ty::TyFnPtr(_) |
             ty::TyNever |
             ty::TyFnDef(..) |
-            ty::TyDynamic(..) => {
+            ty::TyDynamic(..) |
+            ty::TyForeign(..) => {
                 bug!("TyLayout::field_type({:?}): not applicable", self)
             }
 

src/librustc/ty/mod.rs

@@ -1784,7 +1784,7 @@ impl<'a, 'gcx, 'tcx> AdtDef {
                 vec![]
             }
 
-            TyStr | TyDynamic(..) | TySlice(_) | TyError => {
+            TyStr | TyDynamic(..) | TySlice(_) | TyForeign(..) | TyError => {
                 // these are never sized - return the target type
                 vec![ty]
             }

src/librustc/ty/outlives.rs

@@ -142,6 +142,7 @@ impl<'a, 'gcx, 'tcx> TyCtxt<'a, 'gcx, 'tcx> {
             ty::TyNever |           // ...
             ty::TyAdt(..) |         // OutlivesNominalType
             ty::TyAnon(..) |        // OutlivesNominalType (ish)
+            ty::TyForeign(..) |     // OutlivesNominalType
             ty::TyStr |             // OutlivesScalar (ish)
             ty::TyArray(..) |       // ...
             ty::TySlice(..) |       // ...