From 70a33140586b1f6826736b5ba02f794737ea0580 Mon Sep 17 00:00:00 2001
From: Oldes <oldes.huhuman@gmail.com>
Date: Sun, 9 Feb 2020 15:17:04 +0100
Subject: [PATCH] FIX: Overprotective PROTECT for path access to maps

fixes: https://github.com/rebol/rebol-issues/issues/1872
---
 src/core/t-map.c            | 3 ++-
 src/tests/units/map-test.r3 | 9 +++++++++
 2 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/src/core/t-map.c b/src/core/t-map.c
index ea981c3a0b..a173031560 100644
--- a/src/core/t-map.c
+++ b/src/core/t-map.c
@@ -291,6 +291,8 @@
 	REBVAL *val = 0;
 	REBINT n = 0;
 
+	if (pvs->setval) TRAP_PROTECT(VAL_SERIES(data));
+
 	if (IS_END(pvs->path+1)) val = pvs->setval;
 	if (IS_NONE(pvs->select)) return PE_NONE;
 
@@ -302,7 +304,6 @@
 
 	if (!n) return PE_NONE;
 
-	TRAP_PROTECT(VAL_SERIES(data));
 	pvs->value = VAL_BLK_SKIP(data, ((n-1)*2)+1);
 	return PE_OK;
 }
diff --git a/src/tests/units/map-test.r3 b/src/tests/units/map-test.r3
index e4b237834d..77770662a6 100644
--- a/src/tests/units/map-test.r3
+++ b/src/tests/units/map-test.r3
@@ -20,6 +20,15 @@ Rebol [
 	--test-- "map-issue-598"
 		--assert error? try [make map! [[a] 1]]
 
+	;@@ https://github.com/rebol/rebol-issues/issues/1872
+	--test-- "map-issue-1872"
+		m: map [a: 42]
+		protect m
+		--assert error? err: try [m/a: 0]
+		--assert err/id = 'protected
+		--assert 42 = try [m/a]
+		unprotect m
+
 ===end-group===
 
 ===start-group=== "reflection"