From 373c362b7ed0df2dfbc21853e53d5082f20d3de8 Mon Sep 17 00:00:00 2001
From: Oliver Scherer <github35764891676564198441@oli-obk.de>
Date: Thu, 10 Oct 2019 18:21:34 +0200
Subject: [PATCH] Check that we don't access nonexisting union fields

---
 src/librustc_target/abi/mod.rs | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/src/librustc_target/abi/mod.rs b/src/librustc_target/abi/mod.rs
index 26d37f196bef..fde5c5bed4d9 100644
--- a/src/librustc_target/abi/mod.rs
+++ b/src/librustc_target/abi/mod.rs
@@ -738,7 +738,11 @@ impl FieldPlacement {
 
     pub fn offset(&self, i: usize) -> Size {
         match *self {
-            FieldPlacement::Union(_) => Size::ZERO,
+            FieldPlacement::Union(count) => {
+                assert!(i < count,
+                        "Tried to access field {} of union with {} fields", i, count);
+                Size::ZERO
+            },
             FieldPlacement::Array { stride, count } => {
                 let i = i as u64;
                 assert!(i < count);