Put slicing syntax behind a feature gate.

[breaking-change]

If you are using slicing syntax you will need to add #![feature(slicing_syntax)] to your crate.

2 files changed, 8 insertions, 1 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index ca6d488772c..38de2a9c284 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -70,6 +70,7 @@ static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
     ("tuple_indexing", Active),
     ("associated_types", Active),
     ("visible_private_types", Active),
+    ("slicing_syntax", Active),
 
     ("if_let", Active),
 
@@ -362,6 +363,11 @@ impl<'a, 'v> Visitor<'v> for Context<'a> {
                 self.gate_feature("if_let", e.span,
                                   "`if let` syntax is experimental");
             }
+            ast::ExprSlice(..) => {
+                self.gate_feature("slicing_syntax",
+                                  e.span,
+                                  "slicing syntax is experimental");
+            }
             _ => {}
         }
         visit::walk_expr(self, e);
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index a4271544146..64dedd45923 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -23,7 +23,8 @@
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/master/")]
 
-#![feature(macro_rules, globs, default_type_params, phase)]
+#![allow(unknown_features)]
+#![feature(macro_rules, globs, default_type_params, phase, slicing_syntax)]
 #![feature(quote, struct_variant, unsafe_destructor, import_shadowing)]
 #![allow(deprecated)]