ast: fix generic structs with multiple levels of generic embedding (#20042)

vlib/v/ast/table.v

@@ -1936,6 +1936,7 @@ pub fn (mut t Table) unwrap_generic_type(typ Type, generic_names []string, concr
 				fields = ts.info.fields.clone()
 				for i in 0 .. fields.len {
 					if fields[i].typ.has_flag(.generic) {
+						orig_type := fields[i].typ
 						sym := t.sym(fields[i].typ)
 						if sym.kind == .struct_ && fields[i].typ.idx() != typ.idx() {
 							fields[i].typ = t.unwrap_generic_type(fields[i].typ, t_generic_names,
@@ -1947,6 +1948,19 @@ pub fn (mut t Table) unwrap_generic_type(typ Type, generic_names []string, concr
 								fields[i].typ = t_typ
 							}
 						}
+						// Update type in `info.embeds`, if it's embed
+						if fields[i].name.len > 1 && fields[i].name[0].is_capital() {
+							mut parent_sym := t.sym(typ)
+							mut parent_info := parent_sym.info
+							if mut parent_info is Struct {
+								for mut embed in parent_info.embeds {
+									if embed == orig_type {
+										embed = fields[i].typ.set_flag(.generic)
+										break
+									}
+								}
+							}
+						}
 					}
 				}
 				// update concrete types

vlib/v/tests/generics_with_embed_generics_structs_test.v

@@ -2,11 +2,28 @@ struct Foo[T] {
 	field T
 }
 
-struct MainStruct[T] {
+struct Bar[T] {
+	Foo[T]
+}
+
+struct Baz[T] {
+	Bar[T]
+}
+
+struct OneLevelEmbed[T] {
 	Foo[T]
 }
 
 fn test_main() {
-	m := MainStruct[int]{}
+	m := OneLevelEmbed[int]{}
+	assert m.field == 0
+}
+
+struct MultiLevelEmbed[T] {
+	Baz[T]
+}
+
+fn test_multi_level() {
+	m := MultiLevelEmbed[int]{}
 	assert m.field == 0
 }