From b54386ab7a9da8a4f22db3a35a9ec7b0f2b98b6c Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Tomasz=20Mi=C4=85sko?= <tomasz.miasko@gmail.com>
Date: Tue, 4 Aug 2020 00:00:00 +0000
Subject: [PATCH] Detect overflow in proc_macro_server subspan

---
 compiler/rustc_expand/src/proc_macro_server.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compiler/rustc_expand/src/proc_macro_server.rs b/compiler/rustc_expand/src/proc_macro_server.rs
index 39c82f97e0a..5a728bbda96 100644
--- a/compiler/rustc_expand/src/proc_macro_server.rs
+++ b/compiler/rustc_expand/src/proc_macro_server.rs
@@ -584,12 +584,12 @@ impl server::Literal for Rustc<'_> {
 
         let start = match start {
             Bound::Included(lo) => lo,
-            Bound::Excluded(lo) => lo + 1,
+            Bound::Excluded(lo) => lo.checked_add(1)?,
             Bound::Unbounded => 0,
         };
 
         let end = match end {
-            Bound::Included(hi) => hi + 1,
+            Bound::Included(hi) => hi.checked_add(1)?,
             Bound::Excluded(hi) => hi,
             Bound::Unbounded => length,
         };