Adding feature gate

src/libsyntax/feature_gate.rs

@@ -431,6 +431,9 @@ declare_features! (
 
     // Nested groups in `use` (RFC 2128)
     (active, use_nested_groups, "1.23.0", Some(44494)),
+
+    // generic associated types (RFC 1598)
+    (active, generic_associated_types, "1.23.0", Some(44265)),
 );
 
 declare_features! (
@@ -1618,6 +1621,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                 gate_feature_post!(&self, associated_type_defaults, ti.span,
                                   "associated type defaults are unstable");
             }
+            _ if ti.generics.is_parameterized() => {
+                gate_feature_post!(&self, generic_associated_types, ti.span, "generic associated types are unstable");
+            }
             _ => {}
         }
         visit::walk_trait_item(self, ti);
@@ -1636,6 +1642,9 @@ impl<'a> Visitor<'a> for PostExpansionVisitor<'a> {
                     gate_feature_post!(&self, const_fn, ii.span, "const fn is unstable");
                 }
             }
+            _ if ii.generics.is_parameterized() => {
+                gate_feature_post!(&self, generic_associated_types, ii.span, "generic associated types are unstable");
+            }
             _ => {}
         }
         visit::walk_impl_item(self, ii);

src/test/compile-fail/generic-associated-types.rs

@@ -0,0 +1,17 @@
+// Copyright 2012 The Rust Project Developers. See the COPYRIGHT
+// file at the top-level directory of this distribution and at
+// http://rust-lang.org/COPYRIGHT.
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+use std::ops::Deref;
+
+trait PointerFamily {
+    type Pointer<T>: Deref<Target = T>;
+}
+
+fn main() {}

src/test/run-pass/rfc1598-generic-associated-types/construct_with_other_type.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(generic_associated_types)]
+
 trait Foo {
     type Bar<'a, 'b>;
 }

src/test/run-pass/rfc1598-generic-associated-types/iterable.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(generic_associated_types)]
+
 trait Iterable {
     type Item<'a>;
     type Iter<'a>: Iterator<Item = Self::Item<'a>>;

src/test/run-pass/rfc1598-generic-associated-types/pointer_family.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(generic_associated_types)]
+
 use std::rc::Rc;
 use std::sync::Arc;
 use std::ops::Deref;

src/test/run-pass/rfc1598-generic-associated-types/streaming_iterator.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(generic_associated_types)]
+
 use std::fmt::Display;
 
 trait StreamingIterator {

src/test/run-pass/rfc1598-generic-associated-types/where.rs

@@ -8,6 +8,8 @@
 // option. This file may not be copied, modified, or distributed
 // except according to those terms.
 
+#![feature(generic_associated_types)]
+
 // Checking the interaction with this other feature
 #![feature(associated_type_defaults)]