syntax: add an obsolete syntax warning for @[].

src/libsyntax/parse/obsolete.rs

@@ -45,6 +45,7 @@ pub enum ObsoleteSyntax {
     ObsoleteExternModAttributesInParens,
     ObsoleteManagedPattern,
     ObsoleteManagedString,
+    ObsoleteManagedVec,
 }
 
 impl to_bytes::IterBytes for ObsoleteSyntax {
@@ -154,6 +155,10 @@ impl ParserObsoleteMethods for Parser {
                 "managed string",
                 "use `Rc<~str>` instead of a managed string"
             ),
+            ObsoleteManagedVec => (
+                "managed vector",
+                "use `Rc<~[T]>` instead of a managed vector"
+            ),
         };
 
         self.report(sp, kind, kind_str, desc);

src/libsyntax/parse/parser.rs

@@ -2294,7 +2294,10 @@ impl Parser {
             // HACK: turn @[...] into a @-vec
             ex = match e.node {
               ExprVec(..) |
-              ExprRepeat(..) => ExprVstore(e, ExprVstoreBox),
+              ExprRepeat(..) => {
+                  self.obsolete(e.span, ObsoleteManagedVec);
+                  ExprVstore(e, ExprVstoreBox)
+              }
               ExprLit(lit) if lit_is_str(lit) => {
                   self.obsolete(self.last_span, ObsoleteManagedString);
                   ExprVstore(e, ExprVstoreBox)