cgen: fix unwrap option ptr selector (fix #23631) (#23638)

vlib/v/gen/c/cgen.v

@@ -4012,10 +4012,11 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 	mut sum_type_dot := '.'
 	mut field_typ := ast.void_type
 	mut is_option_unwrap := false
+	is_iface_or_sumtype := sym.kind in [.interface, .sum_type]
 	if f := g.table.find_field_with_embeds(sym, node.field_name) {
 		field_sym := g.table.sym(f.typ)
 		field_typ = f.typ
-		if sym.kind in [.interface, .sum_type] {
+		if is_iface_or_sumtype {
 			g.write('(*(')
 		}
 		is_option := field_typ.has_flag(.option)
@@ -4036,7 +4037,11 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 					for i, typ in field.smartcasts {
 						if i == 0 && (is_option_unwrap || nested_unwrap) {
 							deref := if g.inside_selector {
-								'*'.repeat(field.smartcasts.last().nr_muls() + 1)
+								if is_iface_or_sumtype {
+									'*'.repeat(field.smartcasts.last().nr_muls())
+								} else {
+									'*'.repeat(field.smartcasts.last().nr_muls() + 1)
+								}
 							} else if sym.kind == .interface && !typ.is_ptr()
 								&& field.orig_type.has_flag(.option) {
 								''
@@ -4138,7 +4143,7 @@ fn (mut g Gen) selector_expr(node ast.SelectorExpr) {
 			return
 		}
 	} else {
-		if sym.kind in [.interface, .sum_type] {
+		if is_iface_or_sumtype {
 			g.write('(*(')
 		}
 	}

vlib/v/tests/options/option_ptr_unwrap_selector_test.v

@@ -0,0 +1,39 @@
+module main
+
+@[heap]
+interface IGameObject {
+mut:
+	name     string
+	parent   ?&IGameObject
+	children []&IGameObject
+	add_child(mut o IGameObject)
+}
+
+@[heap]
+struct GameObject implements IGameObject {
+mut:
+	name     string
+	parent   ?&IGameObject
+	children []&IGameObject
+}
+
+fn (mut gameobject GameObject) add_child(mut o IGameObject) {
+	o.parent = gameobject
+	gameobject.children << o
+}
+
+fn test_main() {
+	mut v1 := &GameObject{
+		name: 'v1'
+	}
+	mut v2 := &GameObject{
+		name: 'v2'
+	}
+	v1.add_child(mut v2)
+	for child in v1.children {
+		if child.parent != none {
+			eprintln('parent: ${child.parent.name}')
+		}
+	}
+	assert true
+}