cgen: fix error for interface with multi nested embed structs (fix #13331) (#13336)

vlib/v/ast/table.v

@@ -446,6 +446,18 @@ pub fn (t &Table) find_method_with_embeds(sym &TypeSymbol, method_name string) ?
 	}
 }
 
+pub fn (t &Table) get_embed_methods(sym &TypeSymbol) []Fn {
+	mut methods := []Fn{}
+	if sym.info is Struct {
+		for embed in sym.info.embeds {
+			embed_sym := t.sym(embed)
+			methods << embed_sym.methods
+			methods << t.get_embed_methods(embed_sym)
+		}
+	}
+	return methods
+}
+
 fn (t &Table) register_aggregate_field(mut sym TypeSymbol, name string) ?StructField {
 	if sym.kind != .aggregate {
 		t.panic('Unexpected type symbol: $sym.kind')

vlib/v/gen/c/cgen.v

@@ -6797,16 +6797,13 @@ static inline __shared__$interface_name ${shared_fn_name}(__shared__$cctype* x)
 				}
 				else {}
 			}
-			if st_sym.info is ast.Struct {
-				for embed in st_sym.info.embeds {
-					embed_sym := g.table.sym(embed)
-					for embed_method in embed_sym.methods {
-						if embed_method.name !in method_names {
-							methods << embed_method
-						}
-					}
+			t_methods := g.table.get_embed_methods(st_sym)
+			for t_method in t_methods {
+				if t_method.name !in method_names {
+					methods << t_method
 				}
 			}
+
 			for method in methods {
 				mut name := method.name
 				if inter_info.parent_type.has_flag(.generic) {

vlib/v/tests/interface_struct_with_multi_nested_embed_test.v

@@ -0,0 +1,91 @@
+fn test_interface_struct_with_multi_nested_embed() {
+	mut win := &Window{}
+	mut ll := &LinearLayout{}
+	mut lbl := &Label{
+		x: 10
+		y: 20
+	}
+
+	ll.add(mut lbl)
+	win.add(mut ll)
+
+	win.init()
+}
+
+[heap]
+pub struct Window {
+mut:
+	initables []&Initable
+}
+
+interface Initable {
+mut:
+	init(&Window)
+}
+
+pub fn (mut w Window) add(mut initable Initable) {
+	w.initables << initable
+}
+
+interface Container {
+mut:
+	layout()
+}
+
+fn (mut w Window) init() {
+	for wd in w.initables {
+		if mut wd is Container {
+			mut c := wd as Container
+			c.layout()
+		}
+	}
+}
+
+pub struct Rect {
+mut:
+	x int
+	y int
+}
+
+pub fn (r Rect) get_pos() (int, int) {
+	return r.x, r.y
+}
+
+pub struct LayoutBase {
+	Rect
+}
+
+pub struct Base {
+	LayoutBase
+}
+
+pub fn (mut b Base) init(window &Window) {}
+
+[heap]
+pub struct Label {
+	Base
+}
+
+pub interface Layoutable {
+	get_pos() (int, int)
+}
+
+[heap]
+pub struct LinearLayout {
+	Base
+mut:
+	layoutables []Layoutable
+}
+
+pub fn (mut ll LinearLayout) add(mut l Layoutable) {
+	ll.layoutables << l
+}
+
+pub fn (mut ll LinearLayout) layout() {
+	for mut wl in ll.layoutables {
+		x, y := wl.get_pos()
+		println('$x, $y')
+		assert x == 10
+		assert y == 20
+	}
+}