From 84a3b335aa119c536be8186a6c1b91a31a7963c1 Mon Sep 17 00:00:00 2001
From: "Colton G. Rushton" <colton51919@gmail.com>
Date: Fri, 17 Jun 2022 23:30:53 -0300
Subject: [PATCH] Document that `farcall` returns `c` in `a` for some code
 (#937)

---
 engine/overworld/events.asm | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/engine/overworld/events.asm b/engine/overworld/events.asm
index ffbd01dee..5ef11e7c6 100644
--- a/engine/overworld/events.asm
+++ b/engine/overworld/events.asm
@@ -1085,9 +1085,13 @@ TryTileCollisionEvent::
 	call GetFacingTileCoord
 	ld [wFacingTileID], a
 	ld c, a
+	; CheckFacingTileForStdScript preserves c, and
+	; farcall copies c back into a.
 	farcall CheckFacingTileForStdScript
 	jr c, .done
 
+	; CheckCutTreeTile expects a == [wFacingTileID], which
+	; it still is after the previous farcall.
 	call CheckCutTreeTile
 	jr nz, .whirlpool
 	farcall TryCutOW