Auto merge of #22175 - pnkfelix:featuregate-boxpat-rfc469, r=nikomatsakis

Feature gate `box` patterns.

Note that this adds a new feature gate, `box_patterns` specific to e.g. `let box i = ...`, while leaving  `box` expressions (alone) still guarded via the preexisting `box_syntax`.

2 files changed, 7 insertions, 3 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 72bbe1adfaa..1a328f87c19 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -126,6 +126,9 @@ static KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
 
     // Allows using #![no_std]
     ("no_std", "1.0.0", Active),
+
+    // Allows using `box` in patterns; RFC 469
+    ("box_patterns", "1.0.0", Active),
 ];
 
 enum Status {
@@ -427,7 +430,7 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
             ast::ExprBox(..) | ast::ExprUnary(ast::UnOp::UnUniq, _) => {
                 self.gate_feature("box_syntax",
                                   e.span,
-                                  "box expression syntax is experimental in alpha release; \
+                                  "box expression syntax is experimental; \
                                    you can call `Box::new` instead.");
             }
             ast::ExprLit(ref lit) => {
@@ -486,9 +489,9 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                    `[0, ..xs, 0]` are experimental")
             }
             ast::PatBox(..) => {
-                self.gate_feature("box_syntax",
+                self.gate_feature("box_patterns",
                                   pattern.span,
-                                  "box pattern syntax is experimental in alpha release");
+                                  "box pattern syntax is experimental");
             }
             _ => {}
         }
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 41850ada3e6..951e4dcf792 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -23,6 +23,7 @@
        html_favicon_url = "http://www.rust-lang.org/favicon.ico",
        html_root_url = "http://doc.rust-lang.org/nightly/")]
 
+#![feature(box_patterns)]
 #![feature(box_syntax)]
 #![feature(collections)]
 #![feature(core)]