cgen: fix interface embedding complex cases (#13472)

vlib/v/gen/c/cgen.v

@@ -5536,7 +5536,7 @@ static inline __shared__$interface_name ${shared_fn_name}(__shared__$cctype* x)
 			}
 			t_methods := g.table.get_embed_methods(st_sym)
 			for t_method in t_methods {
-				if t_method.name !in method_names {
+				if t_method.name !in methods.map(it.name) {
 					methods << t_method
 				}
 			}

vlib/v/tests/interface_embedding_complex_test.v

@@ -0,0 +1,57 @@
+fn test_interface_embedding_complex() {
+	mut win := &Window{}
+	ll := &LinearLayout{}
+	win.initables << ll
+	win.init()
+}
+
+//----------------------------------
+
+[heap]
+pub struct Window {
+mut:
+	initables []Initable
+}
+
+interface Initable {
+	get_ptr()
+mut:
+	init(&Window)
+}
+
+fn (mut w Window) init() {
+	for mut i in w.initables {
+		i.init(w)
+	}
+}
+
+//----------------------------------
+
+pub struct ViewBase {}
+
+pub fn (mut vb ViewBase) init(window &Window) {
+	dump(@METHOD)
+	assert false
+}
+
+pub fn (vb ViewBase) get_ptr() {}
+
+//-------------------------------------
+
+[heap]
+pub struct ContainerBase {
+	ViewBase
+}
+
+// want to excute this method
+pub fn (mut cb ContainerBase) init(window &Window) {
+	dump(@METHOD)
+	assert true
+}
+
+//--------------------------------------
+
+[heap]
+pub struct LinearLayout {
+	ContainerBase
+}