Feature gate *all* slice patterns. #23121

Until some backwards-compatibility hazards are fixed in #23121,
these need to be unstable.

[breaking-change]

2 files changed, 9 insertions, 0 deletions

diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 60f81dac1e9..ef8a0aa7b52 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -153,6 +153,9 @@ const KNOWN_FEATURES: &'static [(&'static str, &'static str, Status)] = &[
     // below (it has to be checked before expansion possibly makes
     // macros disappear).
     ("allow_internal_unstable", "1.0.0", Active),
+
+    // #23121. Array patterns have some hazards yet.
+    ("slice_patterns", "1.0.0", Active),
 ];
 // (changing above list without updating src/doc/reference.md makes @cmr sad)
 
@@ -694,6 +697,11 @@ impl<'a, 'v> Visitor<'v> for PostExpansionVisitor<'a> {
                                    but at the end of a slice (e.g. \
                                    `[0, ..xs, 0]` are experimental")
             }
+            ast::PatVec(..) => {
+                self.gate_feature("slice_patterns",
+                                  pattern.span,
+                                  "slice pattern syntax is experimental");
+            }
             ast::PatBox(..) => {
                 self.gate_feature("box_patterns",
                                   pattern.span,
diff --git a/src/libsyntax/lib.rs b/src/libsyntax/lib.rs
index 9af7b9ab633..a456807bb90 100644
--- a/src/libsyntax/lib.rs
+++ b/src/libsyntax/lib.rs
@@ -41,6 +41,7 @@
 #![feature(str_char)]
 #![feature(convert)]
 #![feature(into_cow)]
+#![feature(slice_patterns)]
 
 extern crate arena;
 extern crate fmt_macros;