From 2f02a4e4a02fed8275f71f800899fadc488b18d9 Mon Sep 17 00:00:00 2001
From: Tyler Mandry <tmandry@google.com>
Date: Tue, 24 May 2022 12:08:54 -0700
Subject: [PATCH] coverage: Don't underflow column number
I noticed this when running coverage on a debug build of rustc. There
may be other places that do this but I'm just fixing the one I hit.
---
compiler/rustc_mir_transform/src/coverage/mod.rs | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/compiler/rustc_mir_transform/src/coverage/mod.rs b/compiler/rustc_mir_transform/src/coverage/mod.rs
index 2bb9f48f9b7..a96b8efd481 100644
--- a/compiler/rustc_mir_transform/src/coverage/mod.rs
+++ b/compiler/rustc_mir_transform/src/coverage/mod.rs
@@ -515,7 +515,7 @@ fn make_code_region(
// Extend an empty span by one character so the region will be counted.
let CharPos(char_pos) = start_col;
if span.hi() == body_span.hi() {
- start_col = CharPos(char_pos - 1);
+ start_col = CharPos(char_pos.saturating_sub(1));
} else {
end_col = CharPos(char_pos + 1);
}