libsyntax: fix pretty printing of macro with braces

Pretty printing of macro with braces but without terminated semicolon
removed more boxes from stack than it put there, resulting in panic.
This fixes the issue #30731.

1 files changed, 2 insertions, 5 deletions

diff --git a/src/libsyntax/print/pprust.rs b/src/libsyntax/print/pprust.rs
index e80297eb797..759b16c5738 100644
--- a/src/libsyntax/print/pprust.rs
+++ b/src/libsyntax/print/pprust.rs
@@ -1781,11 +1781,8 @@ impl<'a> State<'a> {
             token::Paren => try!(self.popen()),
             token::Bracket => try!(word(&mut self.s, "[")),
             token::Brace => {
-                // head-ibox, will be closed by bopen()
-                try!(self.ibox(0));
-                // Don't ask me why the regular bopen() does
-                // more then just opening a brace...
-                try!(self.bopen())
+                try!(self.head(""));
+                try!(self.bopen());
             }
         }
         try!(self.print_tts(&m.node.tts));