Add feature gate macro_lifetime_matcher

2 files changed, 20 insertions, 2 deletions

diff --git a/src/libsyntax/ext/tt/macro_rules.rs b/src/libsyntax/ext/tt/macro_rules.rs
index 8f2e571c213..5412decd3b7 100644
--- a/src/libsyntax/ext/tt/macro_rules.rs
+++ b/src/libsyntax/ext/tt/macro_rules.rs
@@ -886,8 +886,20 @@ fn is_legal_fragment_specifier(sess: &ParseSess,
                                frag_name: &str,
                                frag_span: Span) -> bool {
     match frag_name {
-        "item" | "block" | "stmt" | "expr" | "pat" | "lifetime" |
+        "item" | "block" | "stmt" | "expr" | "pat" |
         "path" | "ty" | "ident" | "meta" | "tt" | "" => true,
+        "lifetime" => {
+            if     !features.borrow().macro_lifetime_matcher
+                && !attr::contains_name(attrs, "allow_internal_unstable") {
+                let explain = feature_gate::EXPLAIN_LIFETIME_MATCHER;
+                emit_feature_err(sess,
+                                 "macro_lifetime_matcher",
+                                 frag_span,
+                                 GateIssue::Language,
+                                 explain);
+            }
+            true
+        },
         "vis" => {
             if     !features.borrow().macro_vis_matcher
                 && !attr::contains_name(attrs, "allow_internal_unstable") {
diff --git a/src/libsyntax/feature_gate.rs b/src/libsyntax/feature_gate.rs
index 7ae360678cd..471251b0630 100644
--- a/src/libsyntax/feature_gate.rs
+++ b/src/libsyntax/feature_gate.rs
@@ -447,6 +447,9 @@ declare_features! (
 
     // Termination trait in main (RFC 1937)
     (active, termination_trait, "1.24.0", Some(43301)),
+
+    // Allows use of the :lifetime macro fragment specifier
+    (active, macro_lifetime_matcher, "1.24.0", Some(46895)),
 );
 
 declare_features! (
@@ -520,7 +523,7 @@ declare_features! (
     (accepted, loop_break_value, "1.19.0", Some(37339)),
     // Permits numeric fields in struct expressions and patterns.
     (accepted, relaxed_adts, "1.19.0", Some(35626)),
-    // Coerces non capturing closures to function pointers
+   // Coerces non capturing closures to function pointers
     (accepted, closure_to_fn_coercion, "1.19.0", Some(39817)),
     // Allows attributes on struct literal fields.
     (accepted, struct_field_attributes, "1.20.0", Some(38814)),
@@ -1226,6 +1229,9 @@ pub const EXPLAIN_DERIVE_UNDERSCORE: &'static str =
 pub const EXPLAIN_VIS_MATCHER: &'static str =
     ":vis fragment specifier is experimental and subject to change";
 
+pub const EXPLAIN_LIFETIME_MATCHER: &'static str =
+    ":lifetime fragment specifier is experimental and subject to change";
+
 pub const EXPLAIN_PLACEMENT_IN: &'static str =
     "placement-in expression syntax is experimental and subject to change.";