From 5a393820c6bea13a59133a140dfcaf0ab43bf6bf Mon Sep 17 00:00:00 2001
From: Swastik Baranwal <swstkbaranwal@gmail.com>
Date: Mon, 2 Feb 2026 02:32:01 +0530
Subject: [PATCH] checker: preserve mut in other non-none if branch (fix
 #26491) (#26495)

---
 vlib/v/checker/checker.v             |  2 +-
 vlib/v/tests/options/option_2_test.v | 11 +++++++++++
 2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/vlib/v/checker/checker.v b/vlib/v/checker/checker.v
index e3116b665..adef2c2f8 100644
--- a/vlib/v/checker/checker.v
+++ b/vlib/v/checker/checker.v
@@ -4913,7 +4913,7 @@ fn (mut c Checker) smartcast(mut expr ast.Expr, cur_type ast.Type, to_type_ ast.
 					typ:               cur_type
 					pos:               expr.pos
 					is_used:           true
-					is_mut:            expr.is_mut
+					is_mut:            expr.is_mut || is_mut
 					is_inherited:      is_inherited
 					is_unwrapped:      is_option_unwrap
 					smartcasts:        smartcasts
diff --git a/vlib/v/tests/options/option_2_test.v b/vlib/v/tests/options/option_2_test.v
index 16982cd9f..d94069d07 100644
--- a/vlib/v/tests/options/option_2_test.v
+++ b/vlib/v/tests/options/option_2_test.v
@@ -64,3 +64,14 @@ fn foo() ?string {
 fn test_opt_subexp_field() {
 	assert foo()?.len == 2
 }
+
+fn test_mut_opt_none_if_branch() {
+	mut x := ?int(none)
+
+	if x != none {
+		x = 10
+	} else {
+		x = 5
+	}
+	assert x? == 5
+}
-- 
2.39.5