From 4a31aaddb364f5ab8280242a1016bdd3d10dcaed Mon Sep 17 00:00:00 2001
From: "Felix S. Klock II" <pnkfelix@pnkfx.org>
Date: Wed, 7 Jan 2015 15:15:34 +0100
Subject: Added `box_syntax` feature gate; added to std and rustc crates for
 bootstrap.

To avoid using the feauture, change uses of `box <expr>` to
`Box::new(<expr>)` alternative, as noted by the feature gate message.

(Note that box patterns have no analogous trivial replacement, at
least not in general; you need to revise the code to do a partial
match, deref, and then the rest of the match.)

[breaking-change]
---
 src/libsyntax/feature_gate.rs | 12 ++++++++++++
 src/libsyntax/lib.rs          |  1 +
 2 files changed, 13 insertions(+)

(limited to 'src/libsyntax')

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index f10113254de..fbff5e16ef5 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -70,6 +70,7 @@ static KNOWN_FEATURES: &'static [(&'static str, Status)] = &[
     ("associated_types", Accepted),
     ("visible_private_types", Active),
     ("slicing_syntax", Active),
+    ("box_syntax", Active),
 
     ("if_let", Accepted),
     ("while_let", Accepted),
@@ -343,6 +344,12 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                   e.span,
                                   "range syntax is experimental");
             }
+            ast::ExprBox(..) | ast::ExprUnary(ast::UnOp::UnUniq, _) => {
+                self.gate_feature("box_syntax",
+                                  e.span,
+                                  "box expression syntax is experimental in alpha release; \
+                                   you can call `Box::new` instead.");
+            }
             _ => {}
         }
         visit::walk_expr(self, e);
@@ -365,6 +372,11 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                    but at the end of a slice (e.g. \
                                    `[0, ..xs, 0]` are experimental")
             }
+            ast::PatBox(..) => {
+                self.gate_feature("box_syntax",
+                                  pattern.span,
+                                  "box pattern syntax is experimental in alpha release");
+            }
             _ => {}
         }
         visit::walk_pat(self, pattern)
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 9e14f9dd1ea..b6516254dbf 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -24,6 +24,7 @@
 
 #![allow(unknown_features)]
 #![feature(slicing_syntax)]
+#![feature(box_syntax)]
 #![feature(quote, unsafe_destructor)]
 
 extern crate arena;
-- 
cgit 1.4.1-3-g733a5