rollup merge of #23211: FlaPer87/oibit-send-and-friends

Fixes #23225

r? @nikomatsakis

src/libcore/marker.rs

@@ -39,6 +39,8 @@ pub unsafe trait Send : MarkerTrait {
     // empty.
 }
 
+unsafe impl Send for .. { }
+
 impl<T> !Send for *const T { }
 impl<T> !Send for *mut T { }
 impl !Send for Managed { }
@@ -203,6 +205,8 @@ pub unsafe trait Sync : MarkerTrait {
     // Empty
 }
 
+unsafe impl Sync for .. { }
+
 impl<T> !Sync for *const T { }
 impl<T> !Sync for *mut T { }
 impl !Sync for Managed { }

src/librustc/middle/ty.rs

@@ -5989,10 +5989,7 @@ pub fn item_variances(tcx: &ctxt, item_id: ast::DefId) -> Rc<ItemVariances> {
 
 pub fn trait_has_default_impl(tcx: &ctxt, trait_def_id: DefId) -> bool {
     populate_implementations_for_trait_if_necessary(tcx, trait_def_id);
-    match tcx.lang_items.to_builtin_kind(trait_def_id) {
+    tcx.traits_with_default_impls.borrow().contains_key(&trait_def_id)
-        Some(BoundSend) | Some(BoundSync) => true,
-        _ => tcx.traits_with_default_impls.borrow().contains_key(&trait_def_id),
-    }
 }
 
 /// Records a trait-to-implementation mapping.

src/librustc_typeck/coherence/unsafety.rs

@@ -27,10 +27,10 @@ struct UnsafetyChecker<'cx, 'tcx:'cx> {
     tcx: &'cx ty::ctxt<'tcx>
 }
 
-impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
+impl<'cx, 'tcx, 'v> UnsafetyChecker<'cx, 'tcx> {
-    fn visit_item(&mut self, item: &'v ast::Item) {
+    fn check_unsafety_coherence(&mut self, item: &'v ast::Item,
-        match item.node {
+                                unsafety: ast::Unsafety,
-            ast::ItemImpl(unsafety, polarity, _, _, _, _) => {
+                                polarity: ast::ImplPolarity) {
         match ty::impl_trait_ref(self.tcx, ast_util::local_def(item.id)) {
             None => {
                 // Inherent impl.
@@ -76,6 +76,17 @@ impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
             }
         }
     }
+}
+
+impl<'cx, 'tcx,'v> visit::Visitor<'v> for UnsafetyChecker<'cx, 'tcx> {
+    fn visit_item(&mut self, item: &'v ast::Item) {
+        match item.node {
+            ast::ItemDefaultImpl(unsafety, _) => {
+                self.check_unsafety_coherence(item, unsafety, ast::ImplPolarity::Positive);
+            }
+            ast::ItemImpl(unsafety, polarity, _, _, _, _) => {
+                self.check_unsafety_coherence(item, unsafety, polarity);
+            }
             _ => { }
         }
 

src/libsyntax/feature_gate.rs

@@ -563,6 +563,13 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                 }
             }
 
+            ast::ItemDefaultImpl(..) => {
+                self.gate_feature("optin_builtin_traits",
+                                  i.span,
+                                  "default trait implementations are experimental \
+                                   and possibly buggy");
+            }
+
             ast::ItemImpl(_, polarity, _, _, _, _) => {
                 match polarity {
                     ast::ImplPolarity::Negative => {

src/test/compile-fail/coherence-default-trait-impl.rs

@@ -21,4 +21,14 @@ impl MyTrait for .. {}
 impl MyTrait for .. {}
 //~^ ERROR conflicting implementations for trait `MyTrait`
 
+trait MySafeTrait: MarkerTrait {}
+
+unsafe impl MySafeTrait for .. {}
+//~^ ERROR implementing the trait `MySafeTrait` is not unsafe
+
+unsafe trait MyUnsafeTrait: MarkerTrait {}
+
+impl MyUnsafeTrait for .. {}
+//~^ ERROR the trait `MyUnsafeTrait` requires an `unsafe impl` declaration
+
 fn main() {}

src/test/run-make/rustdoc-default-impl/foo.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(optin_builtin_traits)]
+
 pub mod bar {
     use std::marker;