---

yaml
---
r: 273149
b: refs/heads/beta
c: e816910
h: refs/heads/master
i:
  273147: 176cccd

Author: aturon

[refs]

@@ -23,7 +23,7 @@ refs/tags/0.9: 36870b185fc5f5486636d4515f0e22677493f225
 refs/tags/0.10: ac33f2b15782272ae348dbd7b14b8257b2148b5a
 refs/tags/0.11.0: e1247cb1d0d681be034adb4b558b5a0c0d5720f9
 refs/tags/0.12.0: f0c419429ef30723ceaf6b42f9b5a2aeb5d2e2d1
-refs/heads/beta: 9f16c2ce59ac942e1c0415987012100756a44039
+refs/heads/beta: e81691039854e678381042ce93e13bee6971c3d9
 refs/tags/1.0.0-alpha: e42bd6d93a1d3433c486200587f8f9e12590a4d7
 refs/heads/tmp: e06d2ad9fcd5027bcaac5b08fc9aa39a49d0ecd3
 refs/tags/1.0.0-alpha.2: 4c705f6bc559886632d3871b04f58aab093bfa2f

branches/beta/src/librustc/middle/traits/specialize.rs

@@ -88,6 +88,16 @@ impl SpecializationGraph {
                 let overlap = traits::overlapping_impls(&infcx, possible_sibling, impl_def_id);
 
                 if let Some(trait_ref) = overlap {
+                    if !tcx.sess.features.borrow().specialization {
+                        // if specialization is not turned on, all overlaps
+                        // should immediately trigger an error
+
+                        return Err(Overlap {
+                            with_impl: possible_sibling,
+                            on_trait_ref: trait_ref,
+                        });
+                    }
+
                     let le = specializes(tcx, impl_def_id, possible_sibling);
                     let ge = specializes(tcx, possible_sibling, impl_def_id);
 

branches/beta/src/libsyntax/feature_gate.rs

@@ -248,6 +248,9 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Option<u32>, Status
 
     // `expr?`
     ("question_mark", "1.9.0", Some(31436), Active)
+
+    // impl specialization (RFC 1210)
+    ("specialization", "1.7.0", None, Active),
 ];
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -574,6 +577,7 @@ pub struct Features {
     pub stmt_expr_attributes: bool,
     pub deprecated: bool,
     pub question_mark: bool,
+    pub specialization: bool,
 }
 
 impl Features {
@@ -608,6 +612,7 @@ impl Features {
             stmt_expr_attributes: false,
             deprecated: false,
             question_mark: false,
+            specialization: false,
         }
     }
 }
@@ -1102,6 +1107,12 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
     }
 
     fn visit_impl_item(&mut self, ii: &'v ast::ImplItem) {
+        if ii.defaultness == ast::Defaultness::Default {
+            self.gate_feature("specialization",
+                              ii.span,
+                              "specialization is unstable");
+        }
+
         match ii.node {
             ast::ImplItemKind::Const(..) => {
                 self.gate_feature("associated_consts",
@@ -1212,6 +1223,7 @@ fn check_crate_inner<F>(cm: &CodeMap, span_handler: &Handler,
         stmt_expr_attributes: cx.has_feature("stmt_expr_attributes"),
         deprecated: cx.has_feature("deprecated"),
         question_mark: cx.has_feature("question_mark"),
+        specialization: cx.has_feature("specialization"),
     }
 }