From 70bef827a775beec64cd7bbfe34f0edb4dfd6343 Mon Sep 17 00:00:00 2001
From: Richard Feldman <oss@rtfeldman.com>
Date: Fri, 28 Aug 2020 20:23:03 -0400
Subject: [PATCH] Change borrow signature for concat

---
 compiler/mono/src/borrow.rs | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/compiler/mono/src/borrow.rs b/compiler/mono/src/borrow.rs
index ba9487b5e3..d4146a96c8 100644
--- a/compiler/mono/src/borrow.rs
+++ b/compiler/mono/src/borrow.rs
@@ -496,11 +496,11 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         ListSet => arena.alloc_slice_copy(&[owned, irrelevant, irrelevant]),
         ListSetInPlace => arena.alloc_slice_copy(&[owned, irrelevant, irrelevant]),
         ListGetUnsafe => arena.alloc_slice_copy(&[borrowed, irrelevant]),
+        ListConcat | StrConcat => arena.alloc_slice_copy(&[owned, borrowed]),
 
         ListSingle => arena.alloc_slice_copy(&[irrelevant]),
         ListRepeat => arena.alloc_slice_copy(&[irrelevant, irrelevant]),
         ListReverse => arena.alloc_slice_copy(&[owned]),
-        ListConcat | StrConcat => arena.alloc_slice_copy(&[irrelevant, irrelevant]),
         ListAppend => arena.alloc_slice_copy(&[owned, owned]),
         ListPrepend => arena.alloc_slice_copy(&[owned, owned]),
         ListJoin => arena.alloc_slice_copy(&[irrelevant]),