From 117cb040f14719489a38ace1c256ec282f42c367 Mon Sep 17 00:00:00 2001
From: Vadim Petrochenkov <vadim.petrochenkov@gmail.com>
Date: Sat, 23 Jun 2018 20:42:25 +0300
Subject: [PATCH] hygiene: Make sure transparency of `Mark::root()` is an
 implementation detail and cannot be inspected outside of `hygiene.rs`

---
 src/libsyntax_pos/hygiene.rs | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/libsyntax_pos/hygiene.rs b/src/libsyntax_pos/hygiene.rs
index cd2b8b2bff8b..5c35984dfd08 100644
--- a/src/libsyntax_pos/hygiene.rs
+++ b/src/libsyntax_pos/hygiene.rs
@@ -126,11 +126,13 @@ impl Mark {
 
     #[inline]
     pub fn transparency(self) -> Transparency {
+        assert_ne!(self, Mark::root());
         HygieneData::with(|data| data.marks[self.0 as usize].transparency)
     }
 
     #[inline]
     pub fn set_transparency(self, transparency: Transparency) {
+        assert_ne!(self, Mark::root());
         HygieneData::with(|data| data.marks[self.0 as usize].transparency = transparency)
     }