From d9afebc277cc3b96c3df0b5b6538cfecffaaa712 Mon Sep 17 00:00:00 2001
From: Felipe Pena <felipensp@gmail.com>
Date: Mon, 5 May 2025 13:50:33 -0300
Subject: [PATCH] cgen: fix `if mut var != none {` for optional interface
 values (fix #24351) (#24410)

---
 vlib/v/gen/c/cgen.v                           | 13 +++++-
 .../v/tests/options/option_mut_if_none_test.v | 42 +++++++++++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)
 create mode 100644 vlib/v/tests/options/option_mut_if_none_test.v

diff --git a/vlib/v/gen/c/cgen.v b/vlib/v/gen/c/cgen.v
index 0638fb2b3c..e560659401 100644
--- a/vlib/v/gen/c/cgen.v
+++ b/vlib/v/gen/c/cgen.v
@@ -5269,8 +5269,17 @@ fn (mut g Gen) ident(node ast.Ident) {
 						is_option_unwrap := is_option && typ == node.obj.typ.clear_flag(.option)
 						cast_sym := g.table.sym(g.unwrap_generic(typ))
 						if obj_sym.kind == .interface && cast_sym.kind == .interface {
-							ptr := '*'.repeat(node.obj.typ.nr_muls())
-							g.write('I_${obj_sym.cname}_as_I_${cast_sym.cname}(${ptr}${node.name})')
+							if cast_sym.cname != obj_sym.cname {
+								ptr := '*'.repeat(node.obj.typ.nr_muls())
+								g.write('I_${obj_sym.cname}_as_I_${cast_sym.cname}(${ptr}${node.name})')
+							} else {
+								ptr := if is_option {
+									''
+								} else {
+									'*'.repeat(node.obj.typ.nr_muls())
+								}
+								g.write('${ptr}${node.name}')
+							}
 						} else {
 							mut is_ptr := false
 							if i == 0 {
diff --git a/vlib/v/tests/options/option_mut_if_none_test.v b/vlib/v/tests/options/option_mut_if_none_test.v
new file mode 100644
index 0000000000..175f92bd1e
--- /dev/null
+++ b/vlib/v/tests/options/option_mut_if_none_test.v
@@ -0,0 +1,42 @@
+module main
+
+@[heap]
+interface IGameObject {
+mut:
+	name       string
+	parent     ?&IGameObject
+	next       ?&IGameObject
+	child      ?&IGameObject
+	last_child ?&IGameObject
+}
+
+@[heap]
+struct GameObject implements IGameObject {
+mut:
+	name       string
+	parent     ?&IGameObject
+	next       ?&IGameObject
+	child      ?&IGameObject
+	last_child ?&IGameObject
+}
+
+fn test_main() {
+	mut v1 := &GameObject{
+		name: 'v1'
+	}
+	v1.next = &GameObject{
+		name: 'v2'
+	}
+
+	mut next := v1.next
+	for {
+		if mut next != none {
+			eprintln(next.name)
+			assert next.name == 'v2'
+			next = next.next
+		} else {
+			break
+		}
+	}
+	assert next == none
+}