Enable fall through past $:lifetime matcher

src/libsyntax/ext/tt/macro_parser.rs

@@ -827,6 +827,14 @@ fn may_begin_with(name: &str, token: &Token) -> bool {
             Token::Interpolated(ref nt) => may_be_ident(&nt.0),
             _ => false,
         },
+        "lifetime" => match *token {
+            Token::Lifetime(_) => true,
+            Token::Interpolated(ref nt) => match nt.0 {
+                token::NtLifetime(_) | token::NtTT(_) => true,
+                _ => false,
+            },
+            _ => false,
+        },
         _ => match *token {
             token::CloseDelim(_) => false,
             _ => true,